- Email: [email protected]
Evaluation of the potential of solar energy utilization in Famagusta, Cyprus
Sustainable Cities and Society 37 (2018) 189–202
Contents lists available at ScienceDirect
Sustainable Cities and Society journal homepage: www.elsevier.com/locate/scs
Evaluation of the potential of solar energy utilization in Famagusta, Cyprus ⁎
T
Mahmoud Ouria , Harun Sevinc Faculty of Architecture, Eastern Mediterranean University, Famagusta, North Cyprus via Mersin 10, Turkey
A R T I C L E I N F O
A B S T R A C T
Keywords: SHC Solar Energy Urban Area Climatic Factors GIS Famagusta Ladybug
This paper investigates the use of solar energy in urban areas as exemplified by Famagusta in Cyprus. All the climatic and geographic factors were analyzed to compute the solar energy potential for Famagusta City. Next, the solar energy utilization potential in the Social Housing Complex (SHC) district of Famagusta was investigated in detail. The effective parameters of solar energy, including climatic factors, radiation types, geographic parameters, orientation techniques, height to width ratio (H/W) and landscape analysis, were evaluated based on Famagusta using DuffieBeckman and Stephenson’s cousin methods. The rate of irradiation solar energy was analyzed for horizontal, vertical and tilted surfaces of blocks and routes in the SHC in Famagusta City using Ladybug for Rhino and MS Excel software programs. The results of this study showed that the district landscape is very poor from a solar energy point of view. While there is a great source of solar energy producing extreme heat, the solar energy is not utilized properly, as the district is not walkable, especially in the afternoons. It is recommended that pedestrians be helped by adding hardwood trees, by using solar panels to generate renewable power for lightning, and by using permeable materials for pavements.
1. Introduction Considering the aims of sustainable development, renewable energy wins over fossil or nuclear energy sources in regard to the limitations of resources and the negative impacts on environmental factors in sustainable cities (Shukla, Sudhakara, & Prashant, 2017; Shukla, Manish, & Barve, 2017). The role of urban energy consumption is significant because the majority of populations already live in urban areas or cities (United Nations Secretariat, 2012) and (Amadoa & Poggi, 2014). To become climate-neutral is a far-fetched goal that many municipalities have decided to adhere to, while there is little to no experience available for implementing local renewable energy resources on an urban scale. Solar radiation data are the best source of information for estimating the average incident radiation necessary for the proper design and assessment of solar energy conversion systems (Shukla, Rangnekar, & Sudhakar, 2015a; Shukla, Rangnekar, & Sudhakar, 2015b). The solar potential of urban areas corresponding to their various local and geographical features needs to be measured and estimated accordingly (Jakhrani, Othman, Samo, & Kamboh, 2012), (Boehmea, Berger, & Tobias, 2015) and (Shukla et al., 2015a; Shukla et al., 2015b). To maximize active and passive solar heating, production of photovoltaic electricity, or daylighting, is required to quantify the potential of building materials, such as façades, streets and roofs (Lagaris, 2012) and (Shukla, Sudhakar, & Prashant, 2016). Building materials should be ⁎
evaluated by simulations to estimate the solar irradiation and illuminance they absorb, reflect and transmit (Paulescu, Paulescu, Gravila, & Badescu, 2013) and (Sailor, Georgescu, Milne, & Hart, 2015). Solar energy is important in cities because it preserves the natural environment economically and safely (Shukla, Sudhakara et al., 2017; Shukla, Manish et al., 2017) and guarantees a healthy society (Ouria & Sevinc, 2016). This paper evaluates the effective factors of solar energy that influence energy consumption and public activities in cities, in particular the case study of Famagusta. The main objective of this study is the evaluation of solar effects in cities, especially in Famagusta City. The study focused on the solar urban conditions of the Social Housing Complex (SHC) district of Famagusta. Quantitative and comparative methods have been used to analyze orientation techniques, H/W ratio and landscape of routes and blocks. However, existing methodologies, including albedo computation, were applied to support criticism of the current district design of Famagusta City. Famagusta City and the SHC district have low and moderate density characteristics, respectively, and were selected as case studies to evaluate their solar radiation, geographic and climatic conditions. The solar energy potential of Famagusta has been numerically and graphically modeled using quantitative methods in Microsoft Excel and Ladybug for Grasshopper. Solar irradiation is calculated analytically for Famagusta City as a case study because there is no radiation measure available in the
Corresponding author. E-mail addresses: [email protected] (M. Ouria), [email protected] (H. Sevinc).
https://doi.org/10.1016/j.scs.2017.10.036 Received 24 December 2016; Received in revised form 29 October 2017; Accepted 30 October 2017 Available online 21 November 2017 2210-6707/ © 2017 Elsevier Ltd. All rights reserved.
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
weather file as input to Ladybug. The output of the analytical calculation has been fed as input to Ladybug using MS Excel and Elements converter. The value of sky density quantified for the Gen Cumulative Sky model of Famagusta City has been inputted to calculate yearly radiation in Ladybug using isotropic equations 16, 19 and 20. Finally, this paper recommends some alternatives to optimize the use of solar energy in Famagusta in Cyprus.
2. Solar theory and geometry Solar energy analysis processes include four essential steps (Paulescu et al., 2013) and (Ouria, Akçay, & Azami, 2016):
• Analysis of the solar radiation on the latitude • Analysis of climatic and geographic factors • Analysis of site geometry • Analysis of materials/context
Fig. 2. Global, Direct and Diffused radiation.
and DNI. The climate (temperature, humidity and pressure) of different regions is bound to four geographic aspects: altitude, sea level, latitude, and direction of prevailing winds. Location is the most important factor in solar urban design. An inappropriate site selection leads the most discreetly outlined solar system to failure. Therefore, appropriate attention to solar geometry is very important (Cooper, 1969). There are two main parameters, namely, the declination angle (δ) and the sun height/altitude/radiation angle (β), required to describe the relative locations of Earth and sun (Paulescu & Badescu, 2013). The angular position of the sun at the solar noon is shown by the declination angle with respect to the equator in Fig. 3. The angle varies between −23.45° on December 21 (winter solstice) and +23.45° on June 21 (summer solstice). South-facing façades are the ideal orientation for living areas in northern hemispheres. Poor orientation can cause overheating in summer, creating a greenhouse effect at the wrong time of the year. Therefore, the best orientation should be selected. Living spaces with access to the winter sun with south-facing outdoor living areas will have optimum use of the sun’s natural heat and lighting (Montavon, 2010). The value of solar energy varies depending on atmospheric and climatic factors. Global solar radiation includes direct and diffuse radiation (NASA, 2005), (Gray, Beer, Geller, & Haigh, 2010). The amount of the extra-terrestrial irradiance (ETR) does not depend on the position of the urban area on the Earth’s surface. Fig. 4 illustrates the mechanism of ETR. The maximum ratio of solar energy and cosine effect can be collected on each surface if solar radiation is not being scattered and absorbed by the atmosphere. The (ETR) insolation per hour equals the insolation on the horizontal surface at the place (Famagusta City in this paper) without the atmospheric effects (Duffie & Beckman, 1980), (van der Hoeven, 2011). It is presented as follows:
Solar irradiance is the total beam flux density descending on a surface which is perpendicular with the radiation angle (β) with respect to the horizontal plane (Paulescu et al., 2013), (Steinhilber, Beer, & Frohlich, 2009). The sun rises and sets from different points in the sky (the horizon) at different times of the year. It moves across the sky along different paths. Measuring altitude and azimuth is essential to analyzing the sun’s path. Altitude is the angular distance above the horizon measured perpendicularly to the horizon. It has a maximum value of 90° at the zenith, which is the point overhead. Azimuth is the angular distance measured along the horizon in a clockwise direction, as shown in Fig. 1. The number of degrees along the horizon corresponds to the compass direction (Paulescu et al., 2013) and (Jin You, 2017). There are three parameters to measuring solar radiation in sites: Direct Normal Irradiance (DNI), Diffuse Horizontal Irradiance (DHI) and Global Horizontal Irradiance (GHI) (Cogliani, 2014), (Shukla et al., 2015a; Shukla et al., 2015b). Direct Solar Radiation or Direct Normal Irradiance (DNI) is the quantity of received solar radiation per unit area. The area of surface is perpendicular to the sun beams hitting directly. DNI is the maximum rate of radiation that can be measured (Paulescu et al., 2013) and (Cogliani, 2014). Diffuse Solar Radiation or Diffuse Horizontal Irradiance (DHI) is the amount of the radiation scattered by dust, aerosols and particles (Rajput & Sudhakar, 2013). DHI has no unique or special direction (Cogliani, 2014). Global Solar Radiation or Global Horizontal Irradiance (GHI) is the total rate of diffuse and direct solar radiation, which means the sum of the received and scattered radiation on the horizontal surface (Cogliani, 2014), (Paulescu & Badescu, 2013) and (Shukla et al., 2015a; Shukla et al., 2015b). Fig. 2 shows a graphical representation of DHI
360(N ) ⎞ Io = Isc ⎛1 + 0.034 cos 265.25 ⎠ ⎝
(1)
and
Ioh = Io. C osθz
(2)
and
Cosθz = sinφ. sinδ + cosφ. cosδ. cosω where Isc is (the solar constant) equal to 1366 Wm−2; φ is the latitude angle of Famagusta (35); ω is the solar time angle as follows;
Fig. 1. Zenith, Altitude and Azimuth.
190
(3)
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Fig. 3. Solar Geometry.
Iu = Rb . Ib +Id ⎛ ⎝
Rb =
1 + cos s 1 − cos s ⎞ ⎞ + (Ib + Id ) KT ⎛ 2 2 ⎠ ⎠ ⎝
cos θ cos θz
(16)
(17)
cos θ = (sin δ sin φ cos (s ))−(sin δ cos φ sin (s ) cos (z‵)) + (cos δ cos φ cos (s ) cosω) + (cos δ sin φ sin (s ) cos (z‵) cosω) + cos δ sin (s ) sin (z‵) sin ω)
(18)
2
Ioh is calculated in (w/m ). The extra-terrestrial insolation is calculated for a specific time angle (ω). The hour angle at sunrise (ωsr ) is based on radians (Duffie & Beckman, 1980), (Paulescu et al., 2013). The solar constant (Isc) equals (1367 W/m2), and (δ) shows a declination angle. (Ib) is the direct solar beam irradiance on Famagusta surfaces, and (Idh) is the diffuse sky irradiance on the surface following climatic conditions of Famagusta. Sg is surface reflectivity, or albedo, which is 0.22 for Famagusta (Table 2). The irradiation ratio between vertical and horizontal surfaces (Rb) changes based on surface slope (s) and orientation/surface azimuth (z‘) at a given time for Famagusta. (Ibh) is solar irradiation on horizontal surfaces in Famagusta (φ = 35°) on any given day of the year (N). (Ih) has a relation with direct irradiation (Ib), diffused irradiation (Id) and clearness index (KT). Computed values would be affected by arthrosporic factors. The clearness index (KT) clarifies the effective atmospheric factors on the value of insolation at Famagusta. (KT) represents a stochastic parameter that changes depending on altitude, latitude, solar time and climatic conditions (Hoffmann, Oliver, & Schlünzen, 2011). (Iu) is the intensity of the entire solar radiation arriving at oblique surfaces using the isotropic sky model. The clearness index is estimated according to the monthly average of the daily number of hours of bright sunshine in Famagusta (Sb), and the monthly average of the daily maximum number of hours of possible sunshine (Sp) as follows:
Fig. 4. The cosine effect.
ω = 15(t − 12);
(4)
δ is the declination angle of the sun as follows (Duffie & Beckman, 1980); and δ = 23.45. s in ⎡ ⎣
2π . (284 + N ) ⎤ 365 ⎦
(5)
Large amounts of solar energy computations implement (I0) as an initiation point. For each day of the year, I0 is the highest obtainable energy at the edge of the Earth’s atmosphere. The intensity of the solar irradiation received by each surface of Famagusta has been modeled using Duffie-Beckman Solar method as follows (Paulescu et al., 2013), (Duffie & Beckman, 1980), (Shyam & Aggarwal, 2011) and (Khalesi Doost & Akhlaghi, 2014):
Ioh = Isc ⎛1 + 0.033 cos ⎝
360(N ) ⎞ (cos θz ) 365 ⎠
(6)
KT =
Sb Sp
(19)
2 ωs 15
(20)
Cos θz = (cos φ cos δ sin ω + sin φ sin δ )
(7)
ωsr = cos−1 (−tanδ . tan φ)
(8)
Sp =
ω = 15(t − 12)
(9)
The position of the sun can be determined using the azimuth angle (Z) and attitude/radiation angle (β) depending on the location (Famagusta City).
Ih = Ioh. kt
(10)
Ibh = Ih − Idh
(11)
Idh Ih
kT < 0.35 ⎧ 1 − 0.249kT , = 1.557 − 1.84kT , 0.35 < kT < 0.75 ⎨ 0.177kT , kT > 0.75 ⎩
β = arcSin (Sinφ . Sinδ + Cosφ . Cosδ. Cosω)
Z = sin−1 ⎡ ⎢ ⎣
(12)
KT = a + b cos ωs (t − 12) KT
(13)
a = 0.409 − 0.5016 sin(ω − 60)
(14)
b = 0.6607 − 0.4767 sin(ω − 60)
(15)
cosδ . sinω ⎤ cosβ ⎥ ⎦
(21)
(22)
Where δ is declination φ is latitude ω hour angle The Stephenson cosine method was employed to calculate the solar 191
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
energy of vertical surfaces using MS Excel software. The most important factor is cosine angle (θ) between the intensity of the direct beam and façades as follows:
Ivs = Ih. C osθ
(23)
Cosθ = Cosβ . Cos (Z − Z ‵)
(24)
β = sin−1 (sin (φ). sin (δ ) + cos (φ). cos (δ ). cos (ω))
(25)
The azimuth angle of the sun (Z) is different from the orientation azimuth (Z‵). The azimuth of the façades is represented by (Z‵). (β) is the altitude/radiation angle of the sun that varies according to latitude (φ), declination angle (δ) and the solar time angle (ω ). 3. Methodology Solar cities must be designed according to both solar energy and urban design principles. Studies have shown the importance of climatic and geographic factors in solar urban design. In addition, the street orientation, H/W ratio and landscape are important factors in solar design. Solar energy transmission depends on environmental factors (Iqbal, 1983). Therefore, natural environmental factors should also be evaluated to optimize man-made environmental (cities) elements during the design and restoration process. The main objective of this study is the evaluation of the solar effects in cities, especially for Famagusta City in North Cyprus. The study focused on the solar urban conditions of the Social Housing Complex (SHC) district of Famagusta. Qualitative, qualitative and comparative methods were used to analyze the orientation techniques, H/W ratio and landscape of routes and blocks. Famagusta City and the SHC district have low and moderate density characteristics, respectively, that were selected as case studies to evaluate their solar radiation, geographic and climatic conditions. The solar energy potential of Famagusta has been numerically and graphically modeled using quantitative methods in MS Excel and Ladybug for Grasshopper. Fig. 5 visualizes the research process in a flowchart.
Fig. 5. Research Process.
distribution of land use/cover in urban Famagusta was analyzed. Next, the albedo constant in Famagusta City was computed according to GIS data and the proportion of the different materials and colors used in the urban land cover. Land cover is very important, especially in places with limited physical extents (Bahrain, 2003) and (Qingqing et al., 2012). To analyze the solar energy in an area, its land cover and type of use are necessary parameters because they have different reactions to solar radiation. The land cover distribution of Famagusta is presented Fig. 8. According to the land cover data (Figs. 8–10), the urban areas in Famagusta cover 661.7474 ha. This includes 11.5% of the total land area. The forested area is 1193.447 ha, which is 22% of the total area. Bare ground covers 901.1273 ha or 16%, wetland areas 880.41 ha, approximately 16%. Mediterranean grass accounts for 20.69% (1298.751 ha) of the total area (Akingbaso, 2014). Albedo, or the reflectivity of different surfaces, depends of the ratio of surface areas and their reflection ratios. The amount of different land areas was estimated using GIS data for Famagusta City. However, the reflectivity of different surfaces is presented in Table 1 (Oke, 1973) and (Ahrens, 2006). It should be noted that the albedo coefficient (0.22) is estimated for the urban scale of the Famagusta region (rather than Famagusta City) by measuring the area of the cover types and their special coefficients. Therefore, one will have to focus on the micro-scale of environmental factors for each building. The albedo rates in different districts of the city are different. Subsequently, the percentage of each type of cover is presented in Table 1. Although the reflectivity rate varies between 0.2 and 0.5, the lower rate of albedo in Famagusta (0.22) does not help citizens feel that the urban spaces are more comfortable.
3.1. Climatic and geographic analysis of Famagusta City Cyprus is the third largest island in the eastern part of the Mediterranean Sea (Fig. 6). The island is located 33° east of Greenwich and 35° north of the equator. Cyprus has a great potential for domesticating solar energy because of its geographical position and climatic advantages. Its climate is Mediterranean, with mild winters and hot dry summers (Michaelides & Votsi, 1991). Famagusta City is located at the eastern end of island. On average, the city is 25 m above sea level. Its geographical location is 35.1° N, 33.9° E. Its hot Mediterranean climate leads to mild/moderate seasons (Kottek, 2006). Humidity is high in summer, which makes the heat of the environment intolerable. However, it should not be forgotten that the energy absorption rate is different from feeling heat caused by humidity (Oktay, 2009). Dry bulb temperatures, dew point temperatures and relative humidity of the city illustrated using Lady Bug for Grasshopper in Rhino software are shown in Fig. 7a–c, respectively. The input parameters used in these analyses were taken from the Energy Plus database. The average monthly temperature is 22.0 °C in a Mediterranean climate. The differences between the warmest and coldest months is −3 °C to +18 °C, with at least four months above 10 °C. 3.2. Albedo analyses of Famagusta City by GIS data The importance of land cover in the reflection rate of solar energy requires consistent analysis of land cover types and portions taking place on urban heat islands (Xu, Wang, & Xiao, 2000). Therefore, the 192
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Fig. 6. Cyprus in the Mediterranean Sea.
For example, in December, the duration of sunlight hours is 9:37 on average, while it reaches 14:22 in July. The difference between the shortest and longest days is 4:44 h. Potentially, Famagusta has 4383 sunlight hours, but 24% of this amount is wasted during cloudy, hazy and foggy days. There is only 3331 sunny hours. The solar altitude average is 55.2° on March 21 at noon, while it decreases to 32° on December 21 and rises to 72° on June 21 (Fig. 12).
3.3. Solar radiation components at ground level Table 2 presents monthly sunny hours, solar times and clearness index of Famagusta City according to equations 19 and 20. According to equation 22, the altitude of Famagusta City is presented in Fig. 11 using Microsoft Excel. The values are calculated for March 21–22 (spring equinox), December 21–22 (winter solstice), September 22–23 (autumn equinox) and June 21–22 (summer solstice). The solar altitude average is 55.2° on March 21 at noon, while it decreases to 32° on December 21 and rises to 72° on June 21. Additionally, the solar azimuth angle at sunrise is 90° on March 21 at 6:00, while it decreases to 61° on June 21 and rises to 129° on December 21. The annual solar radiation components, such as global solar radiation, diffuse radiation and direct radiation in Famagusta, were generated by the Ladybug for Grasshopper Program. In this model, the annual rate of each component computed according to the solar azimuth is shown.
3.4. The solar energy in vertical surfaces According to Stephenson’s cosine method (Eqs. (23) and (24)), the solar energy of vertical surfaces is computed for winter solstice (21 December) and summer solstice (21 June), without any orientation (vertical walls). In this process, all the climatic and geographic factors, such as altitude, latitude, and sky clearness, have been considered. Fig. 13, shows the solar energy on different surfaces in Famagusta City per hour.
Fig. 7. Famagusta Climate & Temperature.
193
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Fig. 10. The land cover portions of Famagusta after 2012.
Table 1 Average Albedo Value of Land Covers in Famagusta City.
Fig. 8. Land use/cover in the state of Famagusta after 2012.
3.5. SHC The SHC is located along to the Gazi Mustafa Kemal Blvd., with a 47° angle difference from the south (47° SW). There are three streets (Abant St., Konak St. and Sincan St.) in the district running parallel with the blocks. The blocks are organized according to street orientation (Figs. 14 and 15). The orientation rows of Anat, Konak and Sancak streets are in a southeast-northwest direction, which impose a southwest-northeast façade orientation (Fig. 15). The accordance or variance of the block’s angle is checked with the street angle. The majority of blocks and streets are oriented by 43° from a southern direction toward the west.
Cover Types
Albedo Coefficient
Covered Area
Albedo Portion
Mediterranean Grass Open Land (Light Soil and Grass) Bare Ground (light and wet) Wetland (in average temperature of (23 °C) Scrub forest Urban (Stone and Metals with light color and Low Density) Average Constant for Famagusta
0.26 0.45 0.22 0.1
22% 12% 16% 16%
5.7% 5.4% 3.5% 1.6%
0.2 0.15
22% 12%
4.4% 1.8%
–
100%
22.4%
blocks in the SHC. Solar radiation in the SHC has modeled for the whole year using Ladybug for Grasshopper, as shown in Figs. 16–18. The solar irradiation on vertical façades with an orientation of 43° is presented for June 21, March 21 and December 21 using Stephenson’s Cosine method in Microsoft, as shown in Fig. 19. As shown in Fig. 19, the maximum rate of solar energy is available at noon on the south face and is approximately 77 W per square meter per hour (W/m2). The solar energy available on west face is acquirable at 3:00 pm, and its value is approximately 732 (W/m2). Because of the orientation of the buildings, the solar energy available on the east face is not noticeable and is approximately 175 (W/m2) at 8:00 am It can be seen in Fig. 19, that the maximum amount of radiation is obtainable on March 21 at 12:00 on the south surface and is approximately 850 W per square meter per hour (W/m2). The rate of solar energy available on the west face is acquirable at 4:00 pm and is approximately 770 (W/m2). As illustrated in Fig. 19, the highest rate of solar energy is acquirable on June 21 at noon on the south-facing walls and is approximately 872 W per square meter per hour (W/m2). The radiational solar energy available on the west face is approximately 745 (W/m2) at 5:00 pm Because of the orientation of the building and sunrise and sunset azimuth, the solar energy available on the north face is approximately 192 (W/m2) at 6:00 am and 6:00 pm
3.6. Solar potential in the SHC The different orientation or surface azimuth angle causes varying rates of solar energy distribution on different faces or vertical surfaces. It is important to consider the energy behavior of exterior surfaces because it impacts human activities, energy costs, and the period of energy demands. Therefore, the intensity of radiation is computed for all surfaces of the SHC. Solar irradiation is calculated analytically for Famagusta City as a case because there is no radiation measure available in the weather file as input to Ladybug. The output of the analytical calculation has been fed as input to Ladybug using Elements converter. The data given in Table 2 used the Gen Cumulative Sky model based on isotropic methods, which has been input to Ladybug to calculate yearly radiation. The solar radiation rate is computed per square meter (kwh/m2). It has been computed according to the different orientation angles of the
Fig. 9. Different areas of land use/cover in the state of Famagusta after 2012.
194
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Table 2 Monthly Sunny Hours, Solar Time and Clearness Index of Famagusta City. Month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Ave
Sb Sp K̄ t
5.6 9.89 0.56
6 10.73 0.55
7.6 11.77 0.64
8.5 12.92 0.65
10.8 13.86 0.77
11.9 14.34 0.82
12.5 14.11 0.88
12 12.13 0.90
10.4 13.25 0.85
8.9 11.02 0.80
7.3 10.07 0.72
5.5 9.64 0.57
8.91 6.42 0.72
Fig. 11. Solar Altitude of Famagusta City in Solstices and Equilibriums.
Fig. 12. Annual Radiation in Famagusta City. Fig. 13. Solar Radiation on Vertical Surfaces in Famagusta (W/m2).
3.6.1. Solar potential on sloped roofs in the social housing complex Roofs are sloped in the SHC by 20°. The average solar irradiation on sloped surfaces is computed for December 21, March 21, and June 21. In this model, the surface tilt assumed is 20°, with an azimuth of 180 ° from the north, as shown in Fig. 20.
The results (Fig. 22) show that the optimum tilt of collectors is approximately 45–60° for maximum solar energy in December, March and June.
3.6.2. Solar potential on collectors in the social housing complex Solar collectors are installed at 90° opposite the main direction of buildings in the Social Housing Complex (Fig. 21). Whereas the average azimuth of blocks is −43 toward the west, the collectors are on average installed at +47 toward the east. To find an appropriate tilt value for collectors, different alternatives, such as 15, 30, 45, 60 and 75°, with an azimuth of +56, were analyzed.
The effect of the vicinity of the blocks has been analyzed. The vicinity of the blocks next to each other and their azimuth led to a waste of passive solar energy from the façades. In addition, the H/W ratio influences air circulation, which is effective from a street thermal comfort/discomfort aspect. The width of the street is 14 m, and the height of the buildings is 9 m. Thus, the height/width ratio on Konak St. is 9/14, as shown in
3.7. Height-to-width ratio
195
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Fig. 14. Orientation angle of streets and blocks in the Social Housing Complex of Famagusta.
Fig. 15. Social Housing Area in Famagusta City in 2013 (Oktay, 2009).
The type and quality of materials are important factors effecting landscape. Materials with a high reflectance rate should be chosen for the sidewalks, as reflectance directly impacts the heat storage of materials as well as health (Shukla, Sudhakara et al., 2017; Shukla, Manish et al., 2017). Shading is another important factor in solar street space. Shadows impact the walking period, especially in hot climates (Almeida, 2006). There is nothing to provide shadows in the street (Fig. 24). Plants, trees and greenery are used around buildings where the street spaces are very poor.
Fig. 23. 3.8. Landscape analysis In this study, the landscape (the quality of plantings and pavements) was analyzed based on a field survey and photographs. 3.8.1. Greenery analysis Fig. 24 shows the greenery on Konak St. in the SHC. One can see that the trees are planted in private spaces rather than on street space. Although they influence the street quality visually, the trees do not work as solar elements in the street space. Moreover, urban furniture is not applied appropriately.
3.8.2. Sidewalks and pavements The Social Housing Complex is not walkable because the walkways 196
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
energy absorption for each face were performed separately. 4.1. The results of block analysis The main façade of blocks is usually perpendicular to the street direction; therefore, street orientation influences the blocks’ solar performance. A portion of absorbed solar energy radiates from the blocks toward street spaces, which causes increased street temperatures and thermal discomfort. The main aspects of the blocks are orientated at 47° to the southwest, which causes increased solar absorption in the afternoons. The street is exposed to sunlight between 137 and 313°. Thus, street temperatures are high in the afternoons. The data are presented in Table 4. 4.1.1. The results of sloped roofs analysis On average, vertical façades are exposed at a maximum rate when the sun is low on December 21. In addition, horizontal surfaces receive maximum solar energy when the sun is high on June 21. However, the solar energy receiving rate of tilted/sloped surfaces increases on March 21. The solar energy absorbed by sloped surfaces in Famagusta is shown in W/m2 in Table 5. 4.1.2. The results of solar collectors Several factors play an essential role in the efficiency of solar collectors with an acceptable design, including its appropriate location, the tank volume, the tilt angle of the collector, and component quality. The performance of solar collectors depends on the building orientation, collector tilt and azimuth angle. The orientation angle of the collectors is 90° from the block’s main face in the SHC. The recommendations of the tilt and azimuth angles of the Social Housing Complex cases are presented in Tables 6 and 7. The tilt angle of collectors in the SHC is fixed, which has reduced their effectiveness. Collectors are fixed because in this way they are easy to maintain. However, they obtain 25% less solar energy throughout the year. Solar systems are considered to reduce the financial costs of the energy consumed. Therefore, fossil fuels should be avoided for domestic heating. Keep in mind that solar urban areas focus not only on environmental and financial problems, but that aesthetic factors also play a role in solar urban design. For example, water storage tanks in the SHC are not well installed, cause visual pollution and waste absorbed solar energy. Locating water storage tanks on rooftops is inefficient, as the stored heated water gets cooler when coming into contact with outdoor wind. One should therefore install water storage tanks in interior spaces.
Fig. 16. Annual Radiation of Horizontal and Tilted Surfaces in the Social Housing Complex.
are not well-designed, and there is no strategy to provide shade. A lack of car parking and undefined walkways lead to walkways being used as parking places for cars (Fig. 24). Therefore, pedestrians must walk on asphalt streets. 3.8.3. The role of materials in walkability The type and quality of materials are important factors effecting walking periods. Materials with a low rate of reflectance should be used for sidewalks. A comparison of reflectance between asphalt and concrete (like stone) is shown in Table 3. 4. Results and summary A solar analysis of the SHC in Famagusta City was conducted to evaluate its urban passive solar energy potential. Climatic parameters, including a sky clearness coefficient, were calculated for Famagusta’s sky using Duffie-Beckman and Stephenson’s cosine methods. The absorbed solar energy of each surface was computed using numerical methods for blocks in the SHC in Famagusta City. Calculations of solar
4.2. Results of H/W ratio analysis Horizontal surfaces such as streets and roofs are more exposed to solar radiation than vertical surfaces. Therefore, street surface exposure depends on (H/W) ratio or the canyon's depth.
Fig. 17. Annual Radiation of North-Facing Surfaces in Social Housing Complex.
197
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Fig. 18. Annual Radiation of South-Facing Surfaces in the Social Housing Complex. Fig. 19. Solar energy of vertical surfaces with an orientation of 34° in Famagusta.
Fig. 22. Comparison of Solar Collectors Tilt Alternatives in the Social Housing Complex.
atmosphere. Sensible heat flux is a good example of energy transmitted through urban surfaces. A regular urban canyon provides healthy daylight in Famagusta City. The H/W ration analysis of Famagusta streets shows a regular category of canyon, as shown in Table 8.
Fig. 20. Solar energy of tilted (20°) surfaces with orientation of 34° in Famagusta.
4.3. Results of landscape analysis Inappropriate planting resulted in a poor landscape in the SHC. Because of its poor landscape, there are not enough elements to produce shade. Therefore, it is difficult for pedestrians to walk on the pavement, especially during the summer. However, the materials used in pavements are concrete and stone, and these materials are effective in mitigating the urban heat island and reducing the sensible heat flux released into the atmosphere by the paving surfaces. The high reflection coefficient rate of concrete and stone with light color prevents extreme heating. On the other hand, the use of existing asphalt, with its high rate of heat absorption, causes an increase in UHI. Using permeable paving is effective in reducing pavement temperature.
Fig. 21. The azimuth angle of a solar collector in the Social Housing Complex.
The quantity of radiation received via canyon surfaces influences the ambient temperature. The impact rate of these surfaces depends on the thermal performance of the materials, such as reflectance (albedo). Urban surfaces transmit a portion of their absorbed energy into the
4.4. Results of greenery analysis Greenery analysis shows that streets are in very poor condition, with 198
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Fig. 23. The Height/Width Ratio on a Social Housing Complex Street.
Table 7 The Existing Tilt of the Case Examples and Recommendations. Factor
Amount
Existing Fixed Rate Optimum Rate (Fixed without Climatic Factors) Optimum Rate (Practically with Climatic Factors)
Dec-21
Mar-21
Jun-21
45° 55° 60°
45°
30°
Table 8 H/W ratio analysis. Block Height (H)
Street Width (W)
Canyon Ratio
Category
9m
14 m
0.64
Regular
Fig. 24. Lack of Elements to Provide Shadows on a Social Housing Complex Street.
Table 3 Comparison of reflectance between asphalt & concrete. Wavelength (nm)
Asphalt
Concrete
400 500 560 800
0.00 1.00 0.08 0.00
0.00 3.00 0.18 0.00
Table 4 Orientation-related parameters of streets. Orientation Direction
Street Maximum Radiation
Façade Maximum Radiation
Exposed Range (Degrees)
Discomfort Time
Comfort Time
SoutheastNorthwest −47°
1121 Wh/ m2 From 180° at noon
750 Wh/m2 From Southwest (14:00–17:00)
137–313°
Summerafternoon
Winterafternoon Fig. 25. Inappropriate location of solar collectors on a rooftop in the Social Housing Complex.
Table 5 The absorbed solar energy by (20°) slopped surfaces in Famagusta in W/m2. Dec-21
Mar-21
Jun-21
1156
1316
935
Table 9 Albedo Rate of Land Covers.
Table 6 The Existing Azimuth of the Case Examples and Recommendations. Existing Rate
Optimum Rate (Nominally without Climatic Factors)
56° (SE)/124° (N)
15°(SE) – 15° (SW)
199
Cover Types
Albedo Coefficient
Covered Area
Albedo Portion
Mediterranean Greenery/ Trees Urban Average Constant for Famagusta
0.26
< 20%
0.052
0.15 –
> 80% 100%
0.12 17.2%
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Table 10 Summary and Evaluation of the Findings. Issues effecting the street spaces
Good
Orientation H/W Ratio Landscape Greenery Street Shading Albedo
√ √
Poor
√ √ √ √
Comments Well-exposed façades Enough width on streets to provide daylight, low buildings, regular category, providing healthy daylight Poor solar furniture, lack of solar equipment, ruined sidewalks, good materials Inappropriate location of plants in private areas, but effective in solar streets Lack of trees in the streets, lack of any element to provide shade, inappropriate types of tall trees with low rate of shadow range. High rate of urban surfaces, surfaces with low reflectance rate.
Table 11 Details of Recommended Pavements for the Social Housing Complex. Row
Name
1
Gravel
2
Grass
3
Masonry
4
Engineered
Detail
Fig. 26. Recommended Main Paths.
inefficient greenery. Analysis of green areas using Google Maps shows that less than 20% of total green areas for the region. 4.6. Results of albedo value analysis 4.5. Results of shading analysis
According to the data in Table 1, the albedo rate (0.22) is estimated for the urban scale of Famagusta by measuring the ratio of areas and their cover types and special coefficients. However, the albedo rate varies in the SHC streets because their land cover varies. The streets consisting of urban materials (asphalt, concrete and stone) have an albedo rate of 0.26, while the Mediterranean’s greenery albedo rate is 0.15 (Table 9).
Shading analysis of Famagusta streets shows that there are no efficient elements to provide shade. There are very few trees, and existing trees are planted in inappropriate places. In addition, the tall and softwood types of existing trees do not provide shade. We suggest planting short and hardwood trees, as these would be better suited to the climatic conditions of Famagusta City.
4.7. Summary of the findings
4.5.1. Results of Pedestrian path analysis Pedestrian paths of the SHC in Famagusta City are not appropriately designed. In addition to their bumpy paving, they are not appropriate to solar standards. Inappropriate planting has made its landscape poor (Figs. 24 and 25).
The results of this study are presented in a summarized form in Table 10.
Fig. 27. Recommended Pedestrians, Bike and Street Route Section.
200
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
5. Recommendations
direction. In addition, rooftop collectors are not appropriately installed. According to the analyzed data, they would obtain maximum solar energy with an optimal tilting of approximately 45–60°. Famagusta City’s clearness index, the most important factor in diffusing direct beams, is 0.55 and 0.90 in February and August, respectively. Sky clearness influences diffused solar radiation. Therefore, global solar radiation on the city is influenced by both sky clearness and street orientation. Additionally, street orientation limits the period of public activities on the streets. Social Housing Complex streets are suitable for public activities only in the afternoons. The city’s climatic and geographic features influence the rate of solar energy, but the quality of the solar street does not depend only on these factors. The urban characteristics of a street, such as orientation, H/W ratio and landscape, also play a decisive role in the quality of solar streets. Street canyon or H/W ratio is related to the urban micro-climate and human health. A regular urban canyon provides healthy daylight in Social Housing Complex streets (0.64) and supports solar accessibility in Famagusta City. Landscape analysis shows poor greenery and solar tools. The city has a shading problem, and existing trees do not provide sufficient shade. Short trees and solar tools are required to solve this shading problem. The albedo value for Konak St. is less than the total value of the city influencing the poor landscape. According to the energy modeling for Famagusta City using the Ladybug for Grasshopper in Rhino program, direct radiation is 695.03 Wh/m2, diffused horizontal radiation is 426.72 Wh/m2, and global horizontal radiation is 1121.75 Wh/m2. On the other hand, Stephenson’s cosine method for vertical surfaces modeling for Famagusta City shows a radiation rate for Konak St. of approximately 750 Wh/m2 from the southwest in summer (14:00–17:00), which is the most uncomfortable period for public activities in the street. The materials used in pavements around the Social Housing Complex are concrete and stone. We recommend that the northeastern façade of the blocks or the southwestern façade of the streets be redefined to accommodate main pedestrian paths. To increase the permeability of the vegetated and non-vegetated pavement surfaces, it is important to decrease their surface temperatures through evaporation processes. To make their urban space more walkable, livable and sustainable, pedestrians should be shaded by natural hardwood trees. In addition, the use of solar panels is recommended to generate electrical power for street lighting.
5.1. Recommendation for solar pedestrians We recommend the northeastern façades of blocks or southwestern façades of streets be redefined and equipped with main pedestrian paths, as shown in Fig. 26. Recommended paths should be designed with natural trees and sunshades. To make the urban space more walkable, livable and sustainable, pedestrians should be shaded by natural trees. In addition, solar panels should be used to generate electric lighting power, as shown in Fig. 27. To increase the albedo of the paving surfaces, it is essential to absorb less solar radiation (reflective pavements). Most of the existing techniques apply to asphalt, concrete and other types of pavements. Existing techniques to enhance the albedo value of the pavements include the use of concrete additives, such as fly ash and slag. Using light aggregates in asphalt and concrete, white topping techniques, the use of seals and color pigments, reflective and colorless binders, light aggregates, using light color surfaces and pavements with resin-based materials can also produce reflective pavement. To improve the permeability of vegetated and non-vegetated surfaces, it is important to reduce the temperature by an evaporation process. These kinds of pavements can be water-retaining, porous, permeable or made of pervious materials. Permeable and pervious types of materials operate similarly. They have a series of connected holes or pores which facilitate water flow through the material/surface. In the porous type, it is not essential to connect the holes in the mass of the material. The advantage of non-vegetated permeable pavements is in providing a low rate of albedo compared to impermeable surfaces. The maximum rate of voided content in their surface area causes an increase in convective fluxes to the atmosphere. On the other hand, the advantage of vegetated permeable pavements is in reducing temperature through evapotranspiration. Table 11 shows the recommended pavements for the Social Housing Complex in detail. To provide appropriate elements to create shading for paved areas, we suggest applying natural or artificial elements to control unwanted solar radiation, especially during summers in the SHC. Shaded surfaces provide a much lower temperature than surfaces exposed to direct solar radiation. There are two types of sun shading needed for SHC routes: artificial solar shading devices and natural trees. 5.2. Recommendation for active solar energy generation Solar passive house/solar street lights aim to convert solar energy into thermal/electrical energy using urban elements in passive type and photovoltaics in active type (Shukla et al., 2016). The electricity produced can be used to light the paths in the SHC.
Acknowledgements I thank Dr. Ahad Ouria, Associate Professor Department of Civil Engineering for comments that greatly improved the manuscript.
6. Conclusion References Famagusta City has enormous potential to utilize solar energy, but the city is unable to produce the required amount of solar energy because of its inappropriate urban design. The solar altitude average is 55.2° on March 21 at noon, while it decreases to 32° on December 21 and reaches 72° in June 21. In December, the duration of sunlight hours is 9:37 on average, while this increases to 14:22 in July. The differences between the shortest and longest days is 4:44 h. Potentially, Famagusta has 4383 sunlight hours, but as 24% of this amount is wasted during cloudy, hazy and foggy days, only 3331 sunny hours remain. The roofs are sloped at 20°, and the average solar irradiation on sloped surfaces is computed for December 21, March 21, and June 21 as 1156 w/m2, 1316 w/m2 and 935 w/m2 respectively. Solar collectors are installed at 90° toward the east in the opposite direction of blocks. While this is effective at a minimum rate of absorption, they could absorb a maximum rate of energy from a western
Ahrens, C. D. (2006). Meteorology today: an introduction to weather, climate and the environment (8th ed.). Florence: Ky: Brooks/Cole. Akingbaso, E. Y. (2014). Land use – Cover change assessment framework: Famagusta North Cyprus. Famagusta, s.n. Almeida, D. M. (2006). The importance of street Shade for downtown. Porto: Arquitectos Associados Ltd. Amadoa, M., & Poggi, F. (2014). Solar energy integration in urban planning: GUUD model. Energy Procedia, 50, 277–284. Bahrain, M. (2003). Geographic information for planning. Marrakech, Morocco. Boehmea, P., Berger, M., & Tobias, M. (2015). Estimating the building based energy consumption as an anthropogenic contribution to urban heat islands. Sustainable Cities and Society, 19, 373. Cogliani, E. (2014). The role of the direct normal irradiance (DNI) forecasting in the operation of solar concentrating plants. Energy Procedia, 49, 1614. Cooper, P. (1969). Digital simulation of transient solar still process. Solar Energy, 313. Duffie, J., & Beckman, W. (1980). Solar energy of thermal. New York: John Wiley. Gray, L. J., Beer, J., Geller, M., & Haigh, J. D. (2010). Solar influences on climate. The American Geophysical Union.
201
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Paulescu, M., Paulescu, E., Gravila, P., & Badescu, V. (2013). Weather modeling and forecasting of PV systems operation (1st ed.). London: Springer-Verlag London. Qingqing, Z., et al. (2012). Spatial analysis of land use and land cover changes in recent 30 years in manas river basin. Procedia Environmental Sciences, 12, 906–9016. Rajput, D. S., & Sudhakar, K. (2013). Effect of dust on the performance of solar PV panel. International Journal of ChemTech Research, 5(2), 1084. Sailor, D. J., Georgescu, M., Milne, J., & Hart, M. A. (2015). Development of a national anthropogenic heating database with an extrapolation for international cities. Atmospheric Environment, 118, 7. Shukla, A. K., Sudhakara, K., & Prashant, B. (2017). Recent advancement in BIPV product technologies: A review. Energy and Buildings, 140, 188–195. Shukla, A. K., Sudhakar, K., & Prashant, B. (2016). A comprehensive review on design of building integratedphotovoltaic system. Energy and Buildings, 128, 107. Shukla, K. N., Manish, K., & Barve, A. (2017). Simulation and performance analysis of 110 kW p grid-connected photovoltaic system for residential building in India. Bhopal: Nakshmi Narain College of Technology. Shukla, K., Rangnekar, S., & Sudhakar, K. (2015a). Mathematical modelling of solar radiation incident on tilted surface for photovoltaic application at Bhopal, M.P., India. International Journal of Ambient Energy, 37(6), 579–588. Shukla, K., Rangnekar, S., & Sudhakar, K. (2015b). Comparative study of isotropic and anisotropic sky models to estimate solar radiation incident on tilted surface: A case study for Bhopal, India. Energy Reports, 1, 96–103. Shyam, S., & Aggarwal, R. K. (2011). Estimation of hourly solar radiation on horizontal and inclined surfaces in Western Himalayas. Smart Grid and Renewable Energy, 45–50. Steinhilber, F., Beer, J., & Frohlich, C. (2009). Total solar irradiance during the Holocene. American Geophysical Union, 1. United Nations Secretariat (2012). World urbanization prospects. Department of economic and social affairs (Ed.) the 2011 revision. New York: United Nations. van der Hoeven, M. (2011). Solar energy perspectives. Paris: International Energy Agancy. Xu, H., Wang, X., & Xiao, G. (2000). A remote sensing and GIS integrated study on urbanization with its impact on arable lands: Fuqing City, Fujian, Province, China. Land Degradation & Development, 11, 301–314.
Hoffmann, P., Oliver, K., & Schlünzen, K. H. (2011). A statistical model for the urban heat island and its application to a climate change scenario. International Journal of Climatology, 32(8), 1238–1248. Iqbal, M. (1983). Sun-earth astronomical relationships. Solar Radiation, 1–28. Jakhrani, A., Othman, A., Samo, S., & Kamboh, S. (2012). Estimation of incident solar radiation on tilted surface by different empirical models. International Journal of Scientific and Research Publications, 2(12), 1–6. Jin You, L. (2017). GEK 1506 heavenly mathematics: sun and architecture, s.l.: GEK 1506 heavenly mathematics. Khalesi Doost, A., & Akhlaghi, M. (2014). Estimation and comparison of solar radiation intensity by some models in a region of Iran. Journal of Power and Energy Engineering, 2, 345–351. Kottek, M. (2006). World Map of the Köppen-Geiger climate classification updated. Meteorologische Zeitschrif, 259–260. Lagaris, A. (2012). Urban sprawl simulation linking macro-escale processes to microdynamics through cellular automata, an application in Thessaloniki. Applied Geography, 1(34), 46–160. Michaelides, J., & Votsi, P. (1991). Energy analysis and solar energy development in Cyprus. Comput Contre Journal, 211–215. Montavon, M. (2010). Optimisation of urban form by the evaluation of the solar potential. Lausanne s.n. NASA (2005). The balance of power in the earth-sun system. Louisiana: National Aeronautics and Space Administration. Oke, T. (1973). City size and the urban heat island. Atmospheric Environment, 7, 769–779. Oktay, D. (2009). Measuring the quality of urban life in Famagusta, Ankara: Technical reportAnkara: Scientific and Technological Research Council of Turkey. Ouria, M., Akçay, A., & Azami, A. (2016). Quantitative investigation on shaded area according to the geometry of blue-mosque domes in Tabriz-Iran. International Journal of Architectural Engineering & Urban Planning, 26(1), 1–13. Ouria, M., & Sevinc, H. (2016). The role of dams In drying up lake urmia and its environmental impacts on Azerbaijani districts of Iran. Saussurea, 6(1), 54–65. Paulescu, M., & Badescu, V. (2013). Solar energy at urban scale. Online: Wiley.
202
Contents lists available at ScienceDirect
Sustainable Cities and Society journal homepage: www.elsevier.com/locate/scs
Evaluation of the potential of solar energy utilization in Famagusta, Cyprus ⁎
T
Mahmoud Ouria , Harun Sevinc Faculty of Architecture, Eastern Mediterranean University, Famagusta, North Cyprus via Mersin 10, Turkey
A R T I C L E I N F O
A B S T R A C T
Keywords: SHC Solar Energy Urban Area Climatic Factors GIS Famagusta Ladybug
This paper investigates the use of solar energy in urban areas as exemplified by Famagusta in Cyprus. All the climatic and geographic factors were analyzed to compute the solar energy potential for Famagusta City. Next, the solar energy utilization potential in the Social Housing Complex (SHC) district of Famagusta was investigated in detail. The effective parameters of solar energy, including climatic factors, radiation types, geographic parameters, orientation techniques, height to width ratio (H/W) and landscape analysis, were evaluated based on Famagusta using DuffieBeckman and Stephenson’s cousin methods. The rate of irradiation solar energy was analyzed for horizontal, vertical and tilted surfaces of blocks and routes in the SHC in Famagusta City using Ladybug for Rhino and MS Excel software programs. The results of this study showed that the district landscape is very poor from a solar energy point of view. While there is a great source of solar energy producing extreme heat, the solar energy is not utilized properly, as the district is not walkable, especially in the afternoons. It is recommended that pedestrians be helped by adding hardwood trees, by using solar panels to generate renewable power for lightning, and by using permeable materials for pavements.
1. Introduction Considering the aims of sustainable development, renewable energy wins over fossil or nuclear energy sources in regard to the limitations of resources and the negative impacts on environmental factors in sustainable cities (Shukla, Sudhakara, & Prashant, 2017; Shukla, Manish, & Barve, 2017). The role of urban energy consumption is significant because the majority of populations already live in urban areas or cities (United Nations Secretariat, 2012) and (Amadoa & Poggi, 2014). To become climate-neutral is a far-fetched goal that many municipalities have decided to adhere to, while there is little to no experience available for implementing local renewable energy resources on an urban scale. Solar radiation data are the best source of information for estimating the average incident radiation necessary for the proper design and assessment of solar energy conversion systems (Shukla, Rangnekar, & Sudhakar, 2015a; Shukla, Rangnekar, & Sudhakar, 2015b). The solar potential of urban areas corresponding to their various local and geographical features needs to be measured and estimated accordingly (Jakhrani, Othman, Samo, & Kamboh, 2012), (Boehmea, Berger, & Tobias, 2015) and (Shukla et al., 2015a; Shukla et al., 2015b). To maximize active and passive solar heating, production of photovoltaic electricity, or daylighting, is required to quantify the potential of building materials, such as façades, streets and roofs (Lagaris, 2012) and (Shukla, Sudhakar, & Prashant, 2016). Building materials should be ⁎
evaluated by simulations to estimate the solar irradiation and illuminance they absorb, reflect and transmit (Paulescu, Paulescu, Gravila, & Badescu, 2013) and (Sailor, Georgescu, Milne, & Hart, 2015). Solar energy is important in cities because it preserves the natural environment economically and safely (Shukla, Sudhakara et al., 2017; Shukla, Manish et al., 2017) and guarantees a healthy society (Ouria & Sevinc, 2016). This paper evaluates the effective factors of solar energy that influence energy consumption and public activities in cities, in particular the case study of Famagusta. The main objective of this study is the evaluation of solar effects in cities, especially in Famagusta City. The study focused on the solar urban conditions of the Social Housing Complex (SHC) district of Famagusta. Quantitative and comparative methods have been used to analyze orientation techniques, H/W ratio and landscape of routes and blocks. However, existing methodologies, including albedo computation, were applied to support criticism of the current district design of Famagusta City. Famagusta City and the SHC district have low and moderate density characteristics, respectively, and were selected as case studies to evaluate their solar radiation, geographic and climatic conditions. The solar energy potential of Famagusta has been numerically and graphically modeled using quantitative methods in Microsoft Excel and Ladybug for Grasshopper. Solar irradiation is calculated analytically for Famagusta City as a case study because there is no radiation measure available in the
Corresponding author. E-mail addresses: [email protected] (M. Ouria), [email protected] (H. Sevinc).
https://doi.org/10.1016/j.scs.2017.10.036 Received 24 December 2016; Received in revised form 29 October 2017; Accepted 30 October 2017 Available online 21 November 2017 2210-6707/ © 2017 Elsevier Ltd. All rights reserved.
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
weather file as input to Ladybug. The output of the analytical calculation has been fed as input to Ladybug using MS Excel and Elements converter. The value of sky density quantified for the Gen Cumulative Sky model of Famagusta City has been inputted to calculate yearly radiation in Ladybug using isotropic equations 16, 19 and 20. Finally, this paper recommends some alternatives to optimize the use of solar energy in Famagusta in Cyprus.
2. Solar theory and geometry Solar energy analysis processes include four essential steps (Paulescu et al., 2013) and (Ouria, Akçay, & Azami, 2016):
• Analysis of the solar radiation on the latitude • Analysis of climatic and geographic factors • Analysis of site geometry • Analysis of materials/context
Fig. 2. Global, Direct and Diffused radiation.
and DNI. The climate (temperature, humidity and pressure) of different regions is bound to four geographic aspects: altitude, sea level, latitude, and direction of prevailing winds. Location is the most important factor in solar urban design. An inappropriate site selection leads the most discreetly outlined solar system to failure. Therefore, appropriate attention to solar geometry is very important (Cooper, 1969). There are two main parameters, namely, the declination angle (δ) and the sun height/altitude/radiation angle (β), required to describe the relative locations of Earth and sun (Paulescu & Badescu, 2013). The angular position of the sun at the solar noon is shown by the declination angle with respect to the equator in Fig. 3. The angle varies between −23.45° on December 21 (winter solstice) and +23.45° on June 21 (summer solstice). South-facing façades are the ideal orientation for living areas in northern hemispheres. Poor orientation can cause overheating in summer, creating a greenhouse effect at the wrong time of the year. Therefore, the best orientation should be selected. Living spaces with access to the winter sun with south-facing outdoor living areas will have optimum use of the sun’s natural heat and lighting (Montavon, 2010). The value of solar energy varies depending on atmospheric and climatic factors. Global solar radiation includes direct and diffuse radiation (NASA, 2005), (Gray, Beer, Geller, & Haigh, 2010). The amount of the extra-terrestrial irradiance (ETR) does not depend on the position of the urban area on the Earth’s surface. Fig. 4 illustrates the mechanism of ETR. The maximum ratio of solar energy and cosine effect can be collected on each surface if solar radiation is not being scattered and absorbed by the atmosphere. The (ETR) insolation per hour equals the insolation on the horizontal surface at the place (Famagusta City in this paper) without the atmospheric effects (Duffie & Beckman, 1980), (van der Hoeven, 2011). It is presented as follows:
Solar irradiance is the total beam flux density descending on a surface which is perpendicular with the radiation angle (β) with respect to the horizontal plane (Paulescu et al., 2013), (Steinhilber, Beer, & Frohlich, 2009). The sun rises and sets from different points in the sky (the horizon) at different times of the year. It moves across the sky along different paths. Measuring altitude and azimuth is essential to analyzing the sun’s path. Altitude is the angular distance above the horizon measured perpendicularly to the horizon. It has a maximum value of 90° at the zenith, which is the point overhead. Azimuth is the angular distance measured along the horizon in a clockwise direction, as shown in Fig. 1. The number of degrees along the horizon corresponds to the compass direction (Paulescu et al., 2013) and (Jin You, 2017). There are three parameters to measuring solar radiation in sites: Direct Normal Irradiance (DNI), Diffuse Horizontal Irradiance (DHI) and Global Horizontal Irradiance (GHI) (Cogliani, 2014), (Shukla et al., 2015a; Shukla et al., 2015b). Direct Solar Radiation or Direct Normal Irradiance (DNI) is the quantity of received solar radiation per unit area. The area of surface is perpendicular to the sun beams hitting directly. DNI is the maximum rate of radiation that can be measured (Paulescu et al., 2013) and (Cogliani, 2014). Diffuse Solar Radiation or Diffuse Horizontal Irradiance (DHI) is the amount of the radiation scattered by dust, aerosols and particles (Rajput & Sudhakar, 2013). DHI has no unique or special direction (Cogliani, 2014). Global Solar Radiation or Global Horizontal Irradiance (GHI) is the total rate of diffuse and direct solar radiation, which means the sum of the received and scattered radiation on the horizontal surface (Cogliani, 2014), (Paulescu & Badescu, 2013) and (Shukla et al., 2015a; Shukla et al., 2015b). Fig. 2 shows a graphical representation of DHI
360(N ) ⎞ Io = Isc ⎛1 + 0.034 cos 265.25 ⎠ ⎝
(1)
and
Ioh = Io. C osθz
(2)
and
Cosθz = sinφ. sinδ + cosφ. cosδ. cosω where Isc is (the solar constant) equal to 1366 Wm−2; φ is the latitude angle of Famagusta (35); ω is the solar time angle as follows;
Fig. 1. Zenith, Altitude and Azimuth.
190
(3)
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Fig. 3. Solar Geometry.
Iu = Rb . Ib +Id ⎛ ⎝
Rb =
1 + cos s 1 − cos s ⎞ ⎞ + (Ib + Id ) KT ⎛ 2 2 ⎠ ⎠ ⎝
cos θ cos θz
(16)
(17)
cos θ = (sin δ sin φ cos (s ))−(sin δ cos φ sin (s ) cos (z‵)) + (cos δ cos φ cos (s ) cosω) + (cos δ sin φ sin (s ) cos (z‵) cosω) + cos δ sin (s ) sin (z‵) sin ω)
(18)
2
Ioh is calculated in (w/m ). The extra-terrestrial insolation is calculated for a specific time angle (ω). The hour angle at sunrise (ωsr ) is based on radians (Duffie & Beckman, 1980), (Paulescu et al., 2013). The solar constant (Isc) equals (1367 W/m2), and (δ) shows a declination angle. (Ib) is the direct solar beam irradiance on Famagusta surfaces, and (Idh) is the diffuse sky irradiance on the surface following climatic conditions of Famagusta. Sg is surface reflectivity, or albedo, which is 0.22 for Famagusta (Table 2). The irradiation ratio between vertical and horizontal surfaces (Rb) changes based on surface slope (s) and orientation/surface azimuth (z‘) at a given time for Famagusta. (Ibh) is solar irradiation on horizontal surfaces in Famagusta (φ = 35°) on any given day of the year (N). (Ih) has a relation with direct irradiation (Ib), diffused irradiation (Id) and clearness index (KT). Computed values would be affected by arthrosporic factors. The clearness index (KT) clarifies the effective atmospheric factors on the value of insolation at Famagusta. (KT) represents a stochastic parameter that changes depending on altitude, latitude, solar time and climatic conditions (Hoffmann, Oliver, & Schlünzen, 2011). (Iu) is the intensity of the entire solar radiation arriving at oblique surfaces using the isotropic sky model. The clearness index is estimated according to the monthly average of the daily number of hours of bright sunshine in Famagusta (Sb), and the monthly average of the daily maximum number of hours of possible sunshine (Sp) as follows:
Fig. 4. The cosine effect.
ω = 15(t − 12);
(4)
δ is the declination angle of the sun as follows (Duffie & Beckman, 1980); and δ = 23.45. s in ⎡ ⎣
2π . (284 + N ) ⎤ 365 ⎦
(5)
Large amounts of solar energy computations implement (I0) as an initiation point. For each day of the year, I0 is the highest obtainable energy at the edge of the Earth’s atmosphere. The intensity of the solar irradiation received by each surface of Famagusta has been modeled using Duffie-Beckman Solar method as follows (Paulescu et al., 2013), (Duffie & Beckman, 1980), (Shyam & Aggarwal, 2011) and (Khalesi Doost & Akhlaghi, 2014):
Ioh = Isc ⎛1 + 0.033 cos ⎝
360(N ) ⎞ (cos θz ) 365 ⎠
(6)
KT =
Sb Sp
(19)
2 ωs 15
(20)
Cos θz = (cos φ cos δ sin ω + sin φ sin δ )
(7)
ωsr = cos−1 (−tanδ . tan φ)
(8)
Sp =
ω = 15(t − 12)
(9)
The position of the sun can be determined using the azimuth angle (Z) and attitude/radiation angle (β) depending on the location (Famagusta City).
Ih = Ioh. kt
(10)
Ibh = Ih − Idh
(11)
Idh Ih
kT < 0.35 ⎧ 1 − 0.249kT , = 1.557 − 1.84kT , 0.35 < kT < 0.75 ⎨ 0.177kT , kT > 0.75 ⎩
β = arcSin (Sinφ . Sinδ + Cosφ . Cosδ. Cosω)
Z = sin−1 ⎡ ⎢ ⎣
(12)
KT = a + b cos ωs (t − 12) KT
(13)
a = 0.409 − 0.5016 sin(ω − 60)
(14)
b = 0.6607 − 0.4767 sin(ω − 60)
(15)
cosδ . sinω ⎤ cosβ ⎥ ⎦
(21)
(22)
Where δ is declination φ is latitude ω hour angle The Stephenson cosine method was employed to calculate the solar 191
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
energy of vertical surfaces using MS Excel software. The most important factor is cosine angle (θ) between the intensity of the direct beam and façades as follows:
Ivs = Ih. C osθ
(23)
Cosθ = Cosβ . Cos (Z − Z ‵)
(24)
β = sin−1 (sin (φ). sin (δ ) + cos (φ). cos (δ ). cos (ω))
(25)
The azimuth angle of the sun (Z) is different from the orientation azimuth (Z‵). The azimuth of the façades is represented by (Z‵). (β) is the altitude/radiation angle of the sun that varies according to latitude (φ), declination angle (δ) and the solar time angle (ω ). 3. Methodology Solar cities must be designed according to both solar energy and urban design principles. Studies have shown the importance of climatic and geographic factors in solar urban design. In addition, the street orientation, H/W ratio and landscape are important factors in solar design. Solar energy transmission depends on environmental factors (Iqbal, 1983). Therefore, natural environmental factors should also be evaluated to optimize man-made environmental (cities) elements during the design and restoration process. The main objective of this study is the evaluation of the solar effects in cities, especially for Famagusta City in North Cyprus. The study focused on the solar urban conditions of the Social Housing Complex (SHC) district of Famagusta. Qualitative, qualitative and comparative methods were used to analyze the orientation techniques, H/W ratio and landscape of routes and blocks. Famagusta City and the SHC district have low and moderate density characteristics, respectively, that were selected as case studies to evaluate their solar radiation, geographic and climatic conditions. The solar energy potential of Famagusta has been numerically and graphically modeled using quantitative methods in MS Excel and Ladybug for Grasshopper. Fig. 5 visualizes the research process in a flowchart.
Fig. 5. Research Process.
distribution of land use/cover in urban Famagusta was analyzed. Next, the albedo constant in Famagusta City was computed according to GIS data and the proportion of the different materials and colors used in the urban land cover. Land cover is very important, especially in places with limited physical extents (Bahrain, 2003) and (Qingqing et al., 2012). To analyze the solar energy in an area, its land cover and type of use are necessary parameters because they have different reactions to solar radiation. The land cover distribution of Famagusta is presented Fig. 8. According to the land cover data (Figs. 8–10), the urban areas in Famagusta cover 661.7474 ha. This includes 11.5% of the total land area. The forested area is 1193.447 ha, which is 22% of the total area. Bare ground covers 901.1273 ha or 16%, wetland areas 880.41 ha, approximately 16%. Mediterranean grass accounts for 20.69% (1298.751 ha) of the total area (Akingbaso, 2014). Albedo, or the reflectivity of different surfaces, depends of the ratio of surface areas and their reflection ratios. The amount of different land areas was estimated using GIS data for Famagusta City. However, the reflectivity of different surfaces is presented in Table 1 (Oke, 1973) and (Ahrens, 2006). It should be noted that the albedo coefficient (0.22) is estimated for the urban scale of the Famagusta region (rather than Famagusta City) by measuring the area of the cover types and their special coefficients. Therefore, one will have to focus on the micro-scale of environmental factors for each building. The albedo rates in different districts of the city are different. Subsequently, the percentage of each type of cover is presented in Table 1. Although the reflectivity rate varies between 0.2 and 0.5, the lower rate of albedo in Famagusta (0.22) does not help citizens feel that the urban spaces are more comfortable.
3.1. Climatic and geographic analysis of Famagusta City Cyprus is the third largest island in the eastern part of the Mediterranean Sea (Fig. 6). The island is located 33° east of Greenwich and 35° north of the equator. Cyprus has a great potential for domesticating solar energy because of its geographical position and climatic advantages. Its climate is Mediterranean, with mild winters and hot dry summers (Michaelides & Votsi, 1991). Famagusta City is located at the eastern end of island. On average, the city is 25 m above sea level. Its geographical location is 35.1° N, 33.9° E. Its hot Mediterranean climate leads to mild/moderate seasons (Kottek, 2006). Humidity is high in summer, which makes the heat of the environment intolerable. However, it should not be forgotten that the energy absorption rate is different from feeling heat caused by humidity (Oktay, 2009). Dry bulb temperatures, dew point temperatures and relative humidity of the city illustrated using Lady Bug for Grasshopper in Rhino software are shown in Fig. 7a–c, respectively. The input parameters used in these analyses were taken from the Energy Plus database. The average monthly temperature is 22.0 °C in a Mediterranean climate. The differences between the warmest and coldest months is −3 °C to +18 °C, with at least four months above 10 °C. 3.2. Albedo analyses of Famagusta City by GIS data The importance of land cover in the reflection rate of solar energy requires consistent analysis of land cover types and portions taking place on urban heat islands (Xu, Wang, & Xiao, 2000). Therefore, the 192
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Fig. 6. Cyprus in the Mediterranean Sea.
For example, in December, the duration of sunlight hours is 9:37 on average, while it reaches 14:22 in July. The difference between the shortest and longest days is 4:44 h. Potentially, Famagusta has 4383 sunlight hours, but 24% of this amount is wasted during cloudy, hazy and foggy days. There is only 3331 sunny hours. The solar altitude average is 55.2° on March 21 at noon, while it decreases to 32° on December 21 and rises to 72° on June 21 (Fig. 12).
3.3. Solar radiation components at ground level Table 2 presents monthly sunny hours, solar times and clearness index of Famagusta City according to equations 19 and 20. According to equation 22, the altitude of Famagusta City is presented in Fig. 11 using Microsoft Excel. The values are calculated for March 21–22 (spring equinox), December 21–22 (winter solstice), September 22–23 (autumn equinox) and June 21–22 (summer solstice). The solar altitude average is 55.2° on March 21 at noon, while it decreases to 32° on December 21 and rises to 72° on June 21. Additionally, the solar azimuth angle at sunrise is 90° on March 21 at 6:00, while it decreases to 61° on June 21 and rises to 129° on December 21. The annual solar radiation components, such as global solar radiation, diffuse radiation and direct radiation in Famagusta, were generated by the Ladybug for Grasshopper Program. In this model, the annual rate of each component computed according to the solar azimuth is shown.
3.4. The solar energy in vertical surfaces According to Stephenson’s cosine method (Eqs. (23) and (24)), the solar energy of vertical surfaces is computed for winter solstice (21 December) and summer solstice (21 June), without any orientation (vertical walls). In this process, all the climatic and geographic factors, such as altitude, latitude, and sky clearness, have been considered. Fig. 13, shows the solar energy on different surfaces in Famagusta City per hour.
Fig. 7. Famagusta Climate & Temperature.
193
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Fig. 10. The land cover portions of Famagusta after 2012.
Table 1 Average Albedo Value of Land Covers in Famagusta City.
Fig. 8. Land use/cover in the state of Famagusta after 2012.
3.5. SHC The SHC is located along to the Gazi Mustafa Kemal Blvd., with a 47° angle difference from the south (47° SW). There are three streets (Abant St., Konak St. and Sincan St.) in the district running parallel with the blocks. The blocks are organized according to street orientation (Figs. 14 and 15). The orientation rows of Anat, Konak and Sancak streets are in a southeast-northwest direction, which impose a southwest-northeast façade orientation (Fig. 15). The accordance or variance of the block’s angle is checked with the street angle. The majority of blocks and streets are oriented by 43° from a southern direction toward the west.
Cover Types
Albedo Coefficient
Covered Area
Albedo Portion
Mediterranean Grass Open Land (Light Soil and Grass) Bare Ground (light and wet) Wetland (in average temperature of (23 °C) Scrub forest Urban (Stone and Metals with light color and Low Density) Average Constant for Famagusta
0.26 0.45 0.22 0.1
22% 12% 16% 16%
5.7% 5.4% 3.5% 1.6%
0.2 0.15
22% 12%
4.4% 1.8%
–
100%
22.4%
blocks in the SHC. Solar radiation in the SHC has modeled for the whole year using Ladybug for Grasshopper, as shown in Figs. 16–18. The solar irradiation on vertical façades with an orientation of 43° is presented for June 21, March 21 and December 21 using Stephenson’s Cosine method in Microsoft, as shown in Fig. 19. As shown in Fig. 19, the maximum rate of solar energy is available at noon on the south face and is approximately 77 W per square meter per hour (W/m2). The solar energy available on west face is acquirable at 3:00 pm, and its value is approximately 732 (W/m2). Because of the orientation of the buildings, the solar energy available on the east face is not noticeable and is approximately 175 (W/m2) at 8:00 am It can be seen in Fig. 19, that the maximum amount of radiation is obtainable on March 21 at 12:00 on the south surface and is approximately 850 W per square meter per hour (W/m2). The rate of solar energy available on the west face is acquirable at 4:00 pm and is approximately 770 (W/m2). As illustrated in Fig. 19, the highest rate of solar energy is acquirable on June 21 at noon on the south-facing walls and is approximately 872 W per square meter per hour (W/m2). The radiational solar energy available on the west face is approximately 745 (W/m2) at 5:00 pm Because of the orientation of the building and sunrise and sunset azimuth, the solar energy available on the north face is approximately 192 (W/m2) at 6:00 am and 6:00 pm
3.6. Solar potential in the SHC The different orientation or surface azimuth angle causes varying rates of solar energy distribution on different faces or vertical surfaces. It is important to consider the energy behavior of exterior surfaces because it impacts human activities, energy costs, and the period of energy demands. Therefore, the intensity of radiation is computed for all surfaces of the SHC. Solar irradiation is calculated analytically for Famagusta City as a case because there is no radiation measure available in the weather file as input to Ladybug. The output of the analytical calculation has been fed as input to Ladybug using Elements converter. The data given in Table 2 used the Gen Cumulative Sky model based on isotropic methods, which has been input to Ladybug to calculate yearly radiation. The solar radiation rate is computed per square meter (kwh/m2). It has been computed according to the different orientation angles of the
Fig. 9. Different areas of land use/cover in the state of Famagusta after 2012.
194
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Table 2 Monthly Sunny Hours, Solar Time and Clearness Index of Famagusta City. Month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Ave
Sb Sp K̄ t
5.6 9.89 0.56
6 10.73 0.55
7.6 11.77 0.64
8.5 12.92 0.65
10.8 13.86 0.77
11.9 14.34 0.82
12.5 14.11 0.88
12 12.13 0.90
10.4 13.25 0.85
8.9 11.02 0.80
7.3 10.07 0.72
5.5 9.64 0.57
8.91 6.42 0.72
Fig. 11. Solar Altitude of Famagusta City in Solstices and Equilibriums.
Fig. 12. Annual Radiation in Famagusta City. Fig. 13. Solar Radiation on Vertical Surfaces in Famagusta (W/m2).
3.6.1. Solar potential on sloped roofs in the social housing complex Roofs are sloped in the SHC by 20°. The average solar irradiation on sloped surfaces is computed for December 21, March 21, and June 21. In this model, the surface tilt assumed is 20°, with an azimuth of 180 ° from the north, as shown in Fig. 20.
The results (Fig. 22) show that the optimum tilt of collectors is approximately 45–60° for maximum solar energy in December, March and June.
3.6.2. Solar potential on collectors in the social housing complex Solar collectors are installed at 90° opposite the main direction of buildings in the Social Housing Complex (Fig. 21). Whereas the average azimuth of blocks is −43 toward the west, the collectors are on average installed at +47 toward the east. To find an appropriate tilt value for collectors, different alternatives, such as 15, 30, 45, 60 and 75°, with an azimuth of +56, were analyzed.
The effect of the vicinity of the blocks has been analyzed. The vicinity of the blocks next to each other and their azimuth led to a waste of passive solar energy from the façades. In addition, the H/W ratio influences air circulation, which is effective from a street thermal comfort/discomfort aspect. The width of the street is 14 m, and the height of the buildings is 9 m. Thus, the height/width ratio on Konak St. is 9/14, as shown in
3.7. Height-to-width ratio
195
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Fig. 14. Orientation angle of streets and blocks in the Social Housing Complex of Famagusta.
Fig. 15. Social Housing Area in Famagusta City in 2013 (Oktay, 2009).
The type and quality of materials are important factors effecting landscape. Materials with a high reflectance rate should be chosen for the sidewalks, as reflectance directly impacts the heat storage of materials as well as health (Shukla, Sudhakara et al., 2017; Shukla, Manish et al., 2017). Shading is another important factor in solar street space. Shadows impact the walking period, especially in hot climates (Almeida, 2006). There is nothing to provide shadows in the street (Fig. 24). Plants, trees and greenery are used around buildings where the street spaces are very poor.
Fig. 23. 3.8. Landscape analysis In this study, the landscape (the quality of plantings and pavements) was analyzed based on a field survey and photographs. 3.8.1. Greenery analysis Fig. 24 shows the greenery on Konak St. in the SHC. One can see that the trees are planted in private spaces rather than on street space. Although they influence the street quality visually, the trees do not work as solar elements in the street space. Moreover, urban furniture is not applied appropriately.
3.8.2. Sidewalks and pavements The Social Housing Complex is not walkable because the walkways 196
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
energy absorption for each face were performed separately. 4.1. The results of block analysis The main façade of blocks is usually perpendicular to the street direction; therefore, street orientation influences the blocks’ solar performance. A portion of absorbed solar energy radiates from the blocks toward street spaces, which causes increased street temperatures and thermal discomfort. The main aspects of the blocks are orientated at 47° to the southwest, which causes increased solar absorption in the afternoons. The street is exposed to sunlight between 137 and 313°. Thus, street temperatures are high in the afternoons. The data are presented in Table 4. 4.1.1. The results of sloped roofs analysis On average, vertical façades are exposed at a maximum rate when the sun is low on December 21. In addition, horizontal surfaces receive maximum solar energy when the sun is high on June 21. However, the solar energy receiving rate of tilted/sloped surfaces increases on March 21. The solar energy absorbed by sloped surfaces in Famagusta is shown in W/m2 in Table 5. 4.1.2. The results of solar collectors Several factors play an essential role in the efficiency of solar collectors with an acceptable design, including its appropriate location, the tank volume, the tilt angle of the collector, and component quality. The performance of solar collectors depends on the building orientation, collector tilt and azimuth angle. The orientation angle of the collectors is 90° from the block’s main face in the SHC. The recommendations of the tilt and azimuth angles of the Social Housing Complex cases are presented in Tables 6 and 7. The tilt angle of collectors in the SHC is fixed, which has reduced their effectiveness. Collectors are fixed because in this way they are easy to maintain. However, they obtain 25% less solar energy throughout the year. Solar systems are considered to reduce the financial costs of the energy consumed. Therefore, fossil fuels should be avoided for domestic heating. Keep in mind that solar urban areas focus not only on environmental and financial problems, but that aesthetic factors also play a role in solar urban design. For example, water storage tanks in the SHC are not well installed, cause visual pollution and waste absorbed solar energy. Locating water storage tanks on rooftops is inefficient, as the stored heated water gets cooler when coming into contact with outdoor wind. One should therefore install water storage tanks in interior spaces.
Fig. 16. Annual Radiation of Horizontal and Tilted Surfaces in the Social Housing Complex.
are not well-designed, and there is no strategy to provide shade. A lack of car parking and undefined walkways lead to walkways being used as parking places for cars (Fig. 24). Therefore, pedestrians must walk on asphalt streets. 3.8.3. The role of materials in walkability The type and quality of materials are important factors effecting walking periods. Materials with a low rate of reflectance should be used for sidewalks. A comparison of reflectance between asphalt and concrete (like stone) is shown in Table 3. 4. Results and summary A solar analysis of the SHC in Famagusta City was conducted to evaluate its urban passive solar energy potential. Climatic parameters, including a sky clearness coefficient, were calculated for Famagusta’s sky using Duffie-Beckman and Stephenson’s cosine methods. The absorbed solar energy of each surface was computed using numerical methods for blocks in the SHC in Famagusta City. Calculations of solar
4.2. Results of H/W ratio analysis Horizontal surfaces such as streets and roofs are more exposed to solar radiation than vertical surfaces. Therefore, street surface exposure depends on (H/W) ratio or the canyon's depth.
Fig. 17. Annual Radiation of North-Facing Surfaces in Social Housing Complex.
197
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Fig. 18. Annual Radiation of South-Facing Surfaces in the Social Housing Complex. Fig. 19. Solar energy of vertical surfaces with an orientation of 34° in Famagusta.
Fig. 22. Comparison of Solar Collectors Tilt Alternatives in the Social Housing Complex.
atmosphere. Sensible heat flux is a good example of energy transmitted through urban surfaces. A regular urban canyon provides healthy daylight in Famagusta City. The H/W ration analysis of Famagusta streets shows a regular category of canyon, as shown in Table 8.
Fig. 20. Solar energy of tilted (20°) surfaces with orientation of 34° in Famagusta.
4.3. Results of landscape analysis Inappropriate planting resulted in a poor landscape in the SHC. Because of its poor landscape, there are not enough elements to produce shade. Therefore, it is difficult for pedestrians to walk on the pavement, especially during the summer. However, the materials used in pavements are concrete and stone, and these materials are effective in mitigating the urban heat island and reducing the sensible heat flux released into the atmosphere by the paving surfaces. The high reflection coefficient rate of concrete and stone with light color prevents extreme heating. On the other hand, the use of existing asphalt, with its high rate of heat absorption, causes an increase in UHI. Using permeable paving is effective in reducing pavement temperature.
Fig. 21. The azimuth angle of a solar collector in the Social Housing Complex.
The quantity of radiation received via canyon surfaces influences the ambient temperature. The impact rate of these surfaces depends on the thermal performance of the materials, such as reflectance (albedo). Urban surfaces transmit a portion of their absorbed energy into the
4.4. Results of greenery analysis Greenery analysis shows that streets are in very poor condition, with 198
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Fig. 23. The Height/Width Ratio on a Social Housing Complex Street.
Table 7 The Existing Tilt of the Case Examples and Recommendations. Factor
Amount
Existing Fixed Rate Optimum Rate (Fixed without Climatic Factors) Optimum Rate (Practically with Climatic Factors)
Dec-21
Mar-21
Jun-21
45° 55° 60°
45°
30°
Table 8 H/W ratio analysis. Block Height (H)
Street Width (W)
Canyon Ratio
Category
9m
14 m
0.64
Regular
Fig. 24. Lack of Elements to Provide Shadows on a Social Housing Complex Street.
Table 3 Comparison of reflectance between asphalt & concrete. Wavelength (nm)
Asphalt
Concrete
400 500 560 800
0.00 1.00 0.08 0.00
0.00 3.00 0.18 0.00
Table 4 Orientation-related parameters of streets. Orientation Direction
Street Maximum Radiation
Façade Maximum Radiation
Exposed Range (Degrees)
Discomfort Time
Comfort Time
SoutheastNorthwest −47°
1121 Wh/ m2 From 180° at noon
750 Wh/m2 From Southwest (14:00–17:00)
137–313°
Summerafternoon
Winterafternoon Fig. 25. Inappropriate location of solar collectors on a rooftop in the Social Housing Complex.
Table 5 The absorbed solar energy by (20°) slopped surfaces in Famagusta in W/m2. Dec-21
Mar-21
Jun-21
1156
1316
935
Table 9 Albedo Rate of Land Covers.
Table 6 The Existing Azimuth of the Case Examples and Recommendations. Existing Rate
Optimum Rate (Nominally without Climatic Factors)
56° (SE)/124° (N)
15°(SE) – 15° (SW)
199
Cover Types
Albedo Coefficient
Covered Area
Albedo Portion
Mediterranean Greenery/ Trees Urban Average Constant for Famagusta
0.26
< 20%
0.052
0.15 –
> 80% 100%
0.12 17.2%
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Table 10 Summary and Evaluation of the Findings. Issues effecting the street spaces
Good
Orientation H/W Ratio Landscape Greenery Street Shading Albedo
√ √
Poor
√ √ √ √
Comments Well-exposed façades Enough width on streets to provide daylight, low buildings, regular category, providing healthy daylight Poor solar furniture, lack of solar equipment, ruined sidewalks, good materials Inappropriate location of plants in private areas, but effective in solar streets Lack of trees in the streets, lack of any element to provide shade, inappropriate types of tall trees with low rate of shadow range. High rate of urban surfaces, surfaces with low reflectance rate.
Table 11 Details of Recommended Pavements for the Social Housing Complex. Row
Name
1
Gravel
2
Grass
3
Masonry
4
Engineered
Detail
Fig. 26. Recommended Main Paths.
inefficient greenery. Analysis of green areas using Google Maps shows that less than 20% of total green areas for the region. 4.6. Results of albedo value analysis 4.5. Results of shading analysis
According to the data in Table 1, the albedo rate (0.22) is estimated for the urban scale of Famagusta by measuring the ratio of areas and their cover types and special coefficients. However, the albedo rate varies in the SHC streets because their land cover varies. The streets consisting of urban materials (asphalt, concrete and stone) have an albedo rate of 0.26, while the Mediterranean’s greenery albedo rate is 0.15 (Table 9).
Shading analysis of Famagusta streets shows that there are no efficient elements to provide shade. There are very few trees, and existing trees are planted in inappropriate places. In addition, the tall and softwood types of existing trees do not provide shade. We suggest planting short and hardwood trees, as these would be better suited to the climatic conditions of Famagusta City.
4.7. Summary of the findings
4.5.1. Results of Pedestrian path analysis Pedestrian paths of the SHC in Famagusta City are not appropriately designed. In addition to their bumpy paving, they are not appropriate to solar standards. Inappropriate planting has made its landscape poor (Figs. 24 and 25).
The results of this study are presented in a summarized form in Table 10.
Fig. 27. Recommended Pedestrians, Bike and Street Route Section.
200
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
5. Recommendations
direction. In addition, rooftop collectors are not appropriately installed. According to the analyzed data, they would obtain maximum solar energy with an optimal tilting of approximately 45–60°. Famagusta City’s clearness index, the most important factor in diffusing direct beams, is 0.55 and 0.90 in February and August, respectively. Sky clearness influences diffused solar radiation. Therefore, global solar radiation on the city is influenced by both sky clearness and street orientation. Additionally, street orientation limits the period of public activities on the streets. Social Housing Complex streets are suitable for public activities only in the afternoons. The city’s climatic and geographic features influence the rate of solar energy, but the quality of the solar street does not depend only on these factors. The urban characteristics of a street, such as orientation, H/W ratio and landscape, also play a decisive role in the quality of solar streets. Street canyon or H/W ratio is related to the urban micro-climate and human health. A regular urban canyon provides healthy daylight in Social Housing Complex streets (0.64) and supports solar accessibility in Famagusta City. Landscape analysis shows poor greenery and solar tools. The city has a shading problem, and existing trees do not provide sufficient shade. Short trees and solar tools are required to solve this shading problem. The albedo value for Konak St. is less than the total value of the city influencing the poor landscape. According to the energy modeling for Famagusta City using the Ladybug for Grasshopper in Rhino program, direct radiation is 695.03 Wh/m2, diffused horizontal radiation is 426.72 Wh/m2, and global horizontal radiation is 1121.75 Wh/m2. On the other hand, Stephenson’s cosine method for vertical surfaces modeling for Famagusta City shows a radiation rate for Konak St. of approximately 750 Wh/m2 from the southwest in summer (14:00–17:00), which is the most uncomfortable period for public activities in the street. The materials used in pavements around the Social Housing Complex are concrete and stone. We recommend that the northeastern façade of the blocks or the southwestern façade of the streets be redefined to accommodate main pedestrian paths. To increase the permeability of the vegetated and non-vegetated pavement surfaces, it is important to decrease their surface temperatures through evaporation processes. To make their urban space more walkable, livable and sustainable, pedestrians should be shaded by natural hardwood trees. In addition, the use of solar panels is recommended to generate electrical power for street lighting.
5.1. Recommendation for solar pedestrians We recommend the northeastern façades of blocks or southwestern façades of streets be redefined and equipped with main pedestrian paths, as shown in Fig. 26. Recommended paths should be designed with natural trees and sunshades. To make the urban space more walkable, livable and sustainable, pedestrians should be shaded by natural trees. In addition, solar panels should be used to generate electric lighting power, as shown in Fig. 27. To increase the albedo of the paving surfaces, it is essential to absorb less solar radiation (reflective pavements). Most of the existing techniques apply to asphalt, concrete and other types of pavements. Existing techniques to enhance the albedo value of the pavements include the use of concrete additives, such as fly ash and slag. Using light aggregates in asphalt and concrete, white topping techniques, the use of seals and color pigments, reflective and colorless binders, light aggregates, using light color surfaces and pavements with resin-based materials can also produce reflective pavement. To improve the permeability of vegetated and non-vegetated surfaces, it is important to reduce the temperature by an evaporation process. These kinds of pavements can be water-retaining, porous, permeable or made of pervious materials. Permeable and pervious types of materials operate similarly. They have a series of connected holes or pores which facilitate water flow through the material/surface. In the porous type, it is not essential to connect the holes in the mass of the material. The advantage of non-vegetated permeable pavements is in providing a low rate of albedo compared to impermeable surfaces. The maximum rate of voided content in their surface area causes an increase in convective fluxes to the atmosphere. On the other hand, the advantage of vegetated permeable pavements is in reducing temperature through evapotranspiration. Table 11 shows the recommended pavements for the Social Housing Complex in detail. To provide appropriate elements to create shading for paved areas, we suggest applying natural or artificial elements to control unwanted solar radiation, especially during summers in the SHC. Shaded surfaces provide a much lower temperature than surfaces exposed to direct solar radiation. There are two types of sun shading needed for SHC routes: artificial solar shading devices and natural trees. 5.2. Recommendation for active solar energy generation Solar passive house/solar street lights aim to convert solar energy into thermal/electrical energy using urban elements in passive type and photovoltaics in active type (Shukla et al., 2016). The electricity produced can be used to light the paths in the SHC.
Acknowledgements I thank Dr. Ahad Ouria, Associate Professor Department of Civil Engineering for comments that greatly improved the manuscript.
6. Conclusion References Famagusta City has enormous potential to utilize solar energy, but the city is unable to produce the required amount of solar energy because of its inappropriate urban design. The solar altitude average is 55.2° on March 21 at noon, while it decreases to 32° on December 21 and reaches 72° in June 21. In December, the duration of sunlight hours is 9:37 on average, while this increases to 14:22 in July. The differences between the shortest and longest days is 4:44 h. Potentially, Famagusta has 4383 sunlight hours, but as 24% of this amount is wasted during cloudy, hazy and foggy days, only 3331 sunny hours remain. The roofs are sloped at 20°, and the average solar irradiation on sloped surfaces is computed for December 21, March 21, and June 21 as 1156 w/m2, 1316 w/m2 and 935 w/m2 respectively. Solar collectors are installed at 90° toward the east in the opposite direction of blocks. While this is effective at a minimum rate of absorption, they could absorb a maximum rate of energy from a western
Ahrens, C. D. (2006). Meteorology today: an introduction to weather, climate and the environment (8th ed.). Florence: Ky: Brooks/Cole. Akingbaso, E. Y. (2014). Land use – Cover change assessment framework: Famagusta North Cyprus. Famagusta, s.n. Almeida, D. M. (2006). The importance of street Shade for downtown. Porto: Arquitectos Associados Ltd. Amadoa, M., & Poggi, F. (2014). Solar energy integration in urban planning: GUUD model. Energy Procedia, 50, 277–284. Bahrain, M. (2003). Geographic information for planning. Marrakech, Morocco. Boehmea, P., Berger, M., & Tobias, M. (2015). Estimating the building based energy consumption as an anthropogenic contribution to urban heat islands. Sustainable Cities and Society, 19, 373. Cogliani, E. (2014). The role of the direct normal irradiance (DNI) forecasting in the operation of solar concentrating plants. Energy Procedia, 49, 1614. Cooper, P. (1969). Digital simulation of transient solar still process. Solar Energy, 313. Duffie, J., & Beckman, W. (1980). Solar energy of thermal. New York: John Wiley. Gray, L. J., Beer, J., Geller, M., & Haigh, J. D. (2010). Solar influences on climate. The American Geophysical Union.
201
Sustainable Cities and Society 37 (2018) 189–202
M. Ouria, H. Sevinc
Paulescu, M., Paulescu, E., Gravila, P., & Badescu, V. (2013). Weather modeling and forecasting of PV systems operation (1st ed.). London: Springer-Verlag London. Qingqing, Z., et al. (2012). Spatial analysis of land use and land cover changes in recent 30 years in manas river basin. Procedia Environmental Sciences, 12, 906–9016. Rajput, D. S., & Sudhakar, K. (2013). Effect of dust on the performance of solar PV panel. International Journal of ChemTech Research, 5(2), 1084. Sailor, D. J., Georgescu, M., Milne, J., & Hart, M. A. (2015). Development of a national anthropogenic heating database with an extrapolation for international cities. Atmospheric Environment, 118, 7. Shukla, A. K., Sudhakara, K., & Prashant, B. (2017). Recent advancement in BIPV product technologies: A review. Energy and Buildings, 140, 188–195. Shukla, A. K., Sudhakar, K., & Prashant, B. (2016). A comprehensive review on design of building integratedphotovoltaic system. Energy and Buildings, 128, 107. Shukla, K. N., Manish, K., & Barve, A. (2017). Simulation and performance analysis of 110 kW p grid-connected photovoltaic system for residential building in India. Bhopal: Nakshmi Narain College of Technology. Shukla, K., Rangnekar, S., & Sudhakar, K. (2015a). Mathematical modelling of solar radiation incident on tilted surface for photovoltaic application at Bhopal, M.P., India. International Journal of Ambient Energy, 37(6), 579–588. Shukla, K., Rangnekar, S., & Sudhakar, K. (2015b). Comparative study of isotropic and anisotropic sky models to estimate solar radiation incident on tilted surface: A case study for Bhopal, India. Energy Reports, 1, 96–103. Shyam, S., & Aggarwal, R. K. (2011). Estimation of hourly solar radiation on horizontal and inclined surfaces in Western Himalayas. Smart Grid and Renewable Energy, 45–50. Steinhilber, F., Beer, J., & Frohlich, C. (2009). Total solar irradiance during the Holocene. American Geophysical Union, 1. United Nations Secretariat (2012). World urbanization prospects. Department of economic and social affairs (Ed.) the 2011 revision. New York: United Nations. van der Hoeven, M. (2011). Solar energy perspectives. Paris: International Energy Agancy. Xu, H., Wang, X., & Xiao, G. (2000). A remote sensing and GIS integrated study on urbanization with its impact on arable lands: Fuqing City, Fujian, Province, China. Land Degradation & Development, 11, 301–314.
Hoffmann, P., Oliver, K., & Schlünzen, K. H. (2011). A statistical model for the urban heat island and its application to a climate change scenario. International Journal of Climatology, 32(8), 1238–1248. Iqbal, M. (1983). Sun-earth astronomical relationships. Solar Radiation, 1–28. Jakhrani, A., Othman, A., Samo, S., & Kamboh, S. (2012). Estimation of incident solar radiation on tilted surface by different empirical models. International Journal of Scientific and Research Publications, 2(12), 1–6. Jin You, L. (2017). GEK 1506 heavenly mathematics: sun and architecture, s.l.: GEK 1506 heavenly mathematics. Khalesi Doost, A., & Akhlaghi, M. (2014). Estimation and comparison of solar radiation intensity by some models in a region of Iran. Journal of Power and Energy Engineering, 2, 345–351. Kottek, M. (2006). World Map of the Köppen-Geiger climate classification updated. Meteorologische Zeitschrif, 259–260. Lagaris, A. (2012). Urban sprawl simulation linking macro-escale processes to microdynamics through cellular automata, an application in Thessaloniki. Applied Geography, 1(34), 46–160. Michaelides, J., & Votsi, P. (1991). Energy analysis and solar energy development in Cyprus. Comput Contre Journal, 211–215. Montavon, M. (2010). Optimisation of urban form by the evaluation of the solar potential. Lausanne s.n. NASA (2005). The balance of power in the earth-sun system. Louisiana: National Aeronautics and Space Administration. Oke, T. (1973). City size and the urban heat island. Atmospheric Environment, 7, 769–779. Oktay, D. (2009). Measuring the quality of urban life in Famagusta, Ankara: Technical reportAnkara: Scientific and Technological Research Council of Turkey. Ouria, M., Akçay, A., & Azami, A. (2016). Quantitative investigation on shaded area according to the geometry of blue-mosque domes in Tabriz-Iran. International Journal of Architectural Engineering & Urban Planning, 26(1), 1–13. Ouria, M., & Sevinc, H. (2016). The role of dams In drying up lake urmia and its environmental impacts on Azerbaijani districts of Iran. Saussurea, 6(1), 54–65. Paulescu, M., & Badescu, V. (2013). Solar energy at urban scale. Online: Wiley.
202