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Cost of PV electricity – Case study of Greece
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Solar Energy 91 (2013) 120–130 www.elsevier.com/locate/solener
Cost of PV electricity – Case study of Greece J.G. Fantidis, D.V. Bandekas ⇑, C. Potolias, N. Vordos Dpt. of Electrical Engineering, Kavala Institute of Technology, St. Lukas, P.O. 65 404, Greece Received 11 July 2011; received in revised form 14 November 2012; accepted 5 February 2013 Available online 22 March 2013 Communicated by: Associate Editor S.C. Bhattacharya
Abstract The potential for a 20 kW photovoltaic (PV) power plant in Greece is examined in this study. HOMER software is used to predict energy production, cost of energy and reduction of green house gasses (GHGs) emissions. The long-term meteorological parameters for 46 sites in Greece being considered by the Centre for Renewable Energy Sources and Saving (CRES) are analyzed. The global solar radiation varies between a minimum of 4.04 kW h/m2/day in Ioannina and a maximum of 4.89 kW h/m2/day in Tymbakion, while the mean value for the 46 locations remained as 4.46 kW h/m2/day. The renewable energy produced each year from the PV power plant varied between 33.35 MW h in Ioannina and 41.63 MW h in Tymbakion while the average value for the 46 locations is 37.61 MW h. The results of the financial analysis demonstrate that a PV power plant can operate profitably at any of the considered sites in Greece. The capacity factor of a PV plant varies between 19.4% and 24.2% and the cost of electricity varies between 0.122 €/kW h and 0.152 €/ kW h from the most appropriate location to the least attractive location respectively. Bearing in mind that the electricity cost for consumers in Greece is approximately 0.13 €/kW h, the present study demonstrates that photovoltaics can play an important role in Greek energy generation. Last but not least, utilization of photovoltaics means that considerable quantity of CO2 is not released into the local atmosphere each year. Ó 2013 Elsevier Ltd. All rights reserved. Keywords: Renewable energy; HOMER; Solar radiation; Photovoltaic; Solar energy; GHG emissions
1. Introduction Energy is a fundamental ingredient in economic development and energy consumption is an index of prosperity and the standard of living. The consumption of energy per capita has increased significantly in the last number of decades, as the standard of living has improved. Renewable energy is a sustainable and clean source of energy derived from nature. Renewable energy technology is one of the solutions, which produces energy by transforming natural phenomena (or natural resources) into useful energy forms (Dincer, 2011), helps to ensure security of energy supply (Kattakayam and Srinivasan, 1996; Beyer and Langer, 1996), and contributes to the meeting of the ⇑ Corresponding author. Tel.: +30 2510462132.
E-mail address: [email protected] (D.V. Bandekas). 0038-092X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.solener.2013.02.001
Kyoto Protocol objectives (Wohlgemuth and Missfeldt, 2000; Mirasgedis et al., 2002; Sims, 2004; Lund, 2006). Greece is mainly a mountainous country with many variously sized scattered islands, which cover their electricity demand with the utilization of aged autonomous lignite, diesel–oil, natural gas, and mazut (a third of Greece’s electricity is produced from oil and gas) power stations. As a result, the cost of electricity production is extremely high on most islands (Greek PPC, 2013; Kaldellis et al., 2009). The sun is a clean and renewable energy source. Solar energy is a non-depletable, site-dependent source of alternative energy. Among several available technologies, solar PV is the most promising. PV conversion is the direct conversion of sunlight into direct current electricity without the need for a heat engine. The PV process produces power silently and is low maintenance as there are no moving parts. The largest advantage of PV devices is the breadth
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of their power output, ranging from microwatts to megawatts. Greece is one of Europe’s sunnier regions; the annual solar energy approaches 1800 kW h m2 (Fig. 1) (Kaldellis et al., 2002; PVGIS, 2008). The Greek islands in particular possess a very high solar potential and PV electricity offers an economically-attractive solution. Furthermore the solar potential and the seasonal electricity load in Greece are consistent, with higher values during the summer months and lower values during winter. Greece has a range of legislative regulations that have been established for the promotion of renewable energy sources such as development law 3299/2004, as well as 3468/2006, in relation to which the investment is strengthened with reference to the production of electric energy from renewable energy sources. PV systems development constitutes part of the Promotion of Electric Energy Production from Renewable Energy Sources program which operates until 2020 (OJHR, 2004, 2006; Economou, 2010). Law 3299/04 is the “National Development Law” that is applicable to enterprises involved in any economic activity in the country. Regions with high unemployment rates and low income per capita receive the highest investment
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subsidies from the state. Investments in renewable energy systems keep their favoured status under this Law, through investments in high technology, environmental protection, tourism, etc. The funding subsidizes the total investment cost and can amount to 20–60% depending on the region and the size of the company (OJHR, 2004). Law 3468/ 2006 was enacted (from the 6th of June 2006), in order to speed up the licensing procedures and to reform electric energy production from renewable energy. Among others, law 3468/2006 increases the guaranteed market price up to fivefold (for the PV systems), expands the market time from 10 to 20 years and reduces licensing deadlines (OJHR, 2006). In this paper making use of the average daily global solar radiation and clearness index data for 46 locations in Greece, the annual energy production, the economic analysis and the environmental considerations calculated using HOMER software. Locations derived from each of the four climatic zones, in which Greece can be divided (Technical Chamber of Greece, 2010) and not only from areas with good solar potential. HOMERs (Hybrid Optimization Model for Electric Renewables) is a modelling tool that facilitates design of electric power systems. The
Fig. 1. Global solar radiation in Europe.
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assessment criterion of the analysis is the cost of energy (COE). The project assumes a solar PV power plant of 20 kW at each of the 46 locations to calculate the COE, the Capacity Factor (CF) and potential emission reduction due to the PV array (Rehman et al., 2007; Al-Badi et al., 2006).
2. Case study (Greece) It is widely acknowledged that Greece possesses an excellent solar energy potential according to existing long-term measurements, presented in Fig. 1. More specifically, Greece is located in the SE Mediterranean area with an affluent and reliable supply of solar energy, even during the winter. The entire Greek territory is characterized by high solar irradiance, hence the annual solar energy at horizontal plane varies between 1450 kW h/m2 and 1800 kW h/m2 (Fig. 2). From Fig. 2, it is obvious that the south areas in Greece especially the Aegean
Archipelago islands have the highest values of global solar radiation, while less solar irradiance is to be expected in Northern Greece (Kaldellis et al., 2002; PVGIS, 2008). The electricity network of Greece may be divided into two; first is the main-land national grid, based largely on the operation of centralized Thermal Power Stations (mainly based on the local lignite reserves). The second consists of several thousand remote consumers, mainly in the Aegean and Ionian Archipelago areas, located on the several small and medium-sized scattered islands. In these areas the electricity production cost is extremely high (Ntziachristos et al., 2005; Kaldellis et al., 2009) due to the utilization of outdated autonomous power stations based on oil-fuel imports and diesel electric generators.
3. Solar resource In order to calculate the performance of a PV system it is necessary to collect the meteorological data for the site
Fig. 2. Global solar radiation in Greece.
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under consideration. The Centre for Renewable Energy Sources and Saving (CRES, 2011), a source for this data, is the Greek national entity for the promotion of renewable energy sources, rational use of energy and energy conservation. In the present study, 46 representative locations covering all areas of Greece have been identified for solar radiation resource assessment. CRES deduced these long term (1955–1997) meteorological parameters (includes data for wind speed, solar radiation, clearness index, heating degree-days, cooling degree-days, relative humidity) from the Hellenic National Meteorological Service (HNMS, 2011). The average daily solar radiation and the average daily clearness index (both available from CRES) at these locations are given in Table 1 and used as index of the solar
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potential of each of the 46 locations. The clearness index is a dimensionless number (0–1) indicating the fraction of the solar radiation striking the top of the atmosphere that makes it through the atmosphere to strike the Earth’s surface. The following equation defines the monthly average clearness index: K T ¼ H ave =H o;ave
ð1Þ
where Have is the monthly average radiation on the horizontal surface of the earth (kW h/m2/day) and Ho,ave is the extraterrestrial horizontal radiation, meaning the radiation on a horizontal surface at the top of the earth’s atmosphere (kW h/m2/day). The geography in terms of
Table 1 Long-term daily mean values of global solar radiation and the correspondingly clearness index. No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46
City Agchialos Agrinio Alexandroupolis Aliartos Andravida Araxos Argos/pirgela Argostoli Arta Athens/filadelfia Athens/hellenkion Chania Chios Chrysopouli Ierapetra Ioannina Iraklion Kalamata Kastoria Kerkira Komotini Konitsa Korinthos/velo Lamia Larisa Limnos Methoni Milos Mitilini Naxos Paros Patra Pirgos Rethimno Rhodes Samos Serres Siros Sitia Skiros Souda bay Tanagra Thessaloniki Trikala imathias Tymbakion Zakinthos
Latitude N 39° 38° 40° 38° 37° 38° 37° 38° 37° 38° 37° 35° 38° 40° 35° 39° 35° 37° 40° 39° 40° 41° 40° 38° 39° 39° 36° 36° 39° 37° 37° 38° 37° 35° 36° 37° 41° 37° 35° 38° 35° 38° 40° 40° 35° 39°
0
13 370 510 230 550 090 360 110 470 030 540 290 280 540 000 420 200 040 270 370 180 070 030 510 390 550 500 430 040 060 010 150 400 210 240 420 050 250 120 540 330 190 310 360 000 100
Longitude E 22° 21° 25° 23° 21° 21° 22° 20° 20° 23° 23° 24° 26° 24° 25° 20° 25° 22° 21° 19° 21° 25° 20° 22° 22° 25° 21° 24° 26° 25° 25° 21° 21° 24° 28° 26° 23° 24° 26° 24° 24° 23° 22° 22° 24° 21°
0
48 230 560 060 170 250 470 290 540 400 450 070 080 360 440 490 110 000 170 550 470 240 450 240 270 140 420 270 360 230 080 440 180 310 070 550 340 570 060 330 070 330 580 330 460 000
Elevation (m)
Daily solar radiation (kWh/m2/day)
Clearness index
15.3 25 3.5 110 15.1 11.5 11.2 22 7.9 138 15 150 5 5.4 10 484 39.3 11.1 660.9 4 625 30 542 17.4 73.6 4.6 33 182 4 9.8 33.5 1 12 7 11.5 7.3 34.5 72 115.6 17.9 151.6 140.1 4.8 0.8 6.7 10.5
4.30 4.44 4.12 4.40 4.65 4.45 4.66 4.59 4.42 4.41 4.48 4.66 4.55 4.16 4.87 4.04 4.71 4.58 4.08 4.35 4.15 4.16 4.56 4.28 4.25 4.33 4.56 4.62 4.44 4.59 4.65 4.39 4.61 4.61 4.70 4.73 4.05 4.63 4.74 4.32 4.73 4.39 4.05 4.07 4.89 4.38
0.523 0.537 0.506 0.521 0.560 0.535 0.540 0.543 0.524 0.532 0.538 0.540 0.542 0.520 0.570 0.489 0.546 0.537 0.506 0.530 0.512 0.510 0.540 0.515 0.522 0.568 0.538 0.535 0.542 0.550 0.534 0.534 0.535 0.557 0.567 0.532 0.518 0.523 0.537 0.550 0.585 0.536 0.493 0.512 0.571 0.543
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latitude, longitude and elevation from the sea level is also presented in Table 1. HOMER (2011) uses the following equation to estimate the output of the PV array: P PV ¼ Y PV fPV
GT ½1 þ ap ðT c T c;STC Þ GT ;STC
ð2Þ
where YPV is the rated capacity of the PV array, meaning its power output under standard test conditions (kW), fPV is the PV derating factor (%), is the solar radiation incident on the PV array in the current time step (kW/m2), is the incident radiation at standard test conditions (1 kW/ m2), Tc is the PV cell temperature in the current time step (°C), and Tc,STC is the PV cell temperature under standard test conditions (25 °C). In the present study the derating factor was taken as 90%, which compensates for reduction in efficiency due to temperature, dust and wiring losses (Demiroren and Yilmaz, 2010; Al-Karaghouli and Kazmerski, 2010). HOMER simulates the operation of a system by making energy balance calculations for each of the 8760 h in a year. Because the measured hourly solar radiation data is rarely available, it is often necessary to use HOMER’s capability to generate synthetic hourly solar data from monthly averages. The algorithm that HOMER uses to synthesize solar data is based on the work of Graham and Hollands (1990). This algorithm produces realistic hourly data and it is easy to use because it requires only the latitude and the monthly averages. HOMER handles the PV panels in terms of rated kW and not in m2 and for this reason it does not need the efficiency. HOMER assumes the PV panels always operate at the maximum power point, as it would if they were controlled by a maximum power point tracker. Finally HOMER supposes that the output of the PV panel is linearly proportional to the incident radiation; consequently if the radiation is 0.75 kW/m2, the panels will produce 75% of their rated output.
Fig. 3. System configuration in HOMERENERGY.
Fig. 3. According to this architecture, there are three main components to the system; PV panels, a converter and the public grid. The generated energy is sent to the grid. The DC and AC lines are connected via the inverter (converter); the DC power from the PV modules is converted into AC power and fed into the grid system using the inverters. Owing to the dramatic decrease in the cost of PV panels over the last number of years, the current (February 2012) wholesale price of a simple PV panel is approximately 0.72 €/Wp, excluding transportation cost. However, the retail price for a customer is more than twice that value (1.88 €/Wp) since a small power plant additionally requires other components such as wires, switches, inverters, tracker costs, and labor for installing solar modules – these represent more than half the cost of a solar power system. These components are collectively referred to as the “balance of system” (BOS). BOS manufacturers could significantly reduce their costs (and thus lower costs for the whole industry) by implementing techniques—such as modularization, preassembly, standardization, and automation. The best price for a small 20 kW (19.88 kW for the correctness of a description) power plant in Greece is approximately 67,000 € (Levadiotis, 2012). Each of the utilized PV modules has a rated power of 280 W and other specifications shown in Table 2 (Exiom, 2012). Table 3 shows the technical data for the inverters (SMA, 2012). The project lifetime has been considered to be 25 years and the annual real interest rate has been taken as 5%.
4. Economic analysis of energy system HOMER defines the levelized COE as the average cost/ kW h of electrical energy produced by the system. In order to calculate the COE, HOMER divides the annualized cost of producing electricity by the total useful electric energy production. According to the HOMER software, the equation for the COE is as follows: COE ¼
C ann;tot Eprim;AC þ Eprim;DC þ Egrid;sales
ð3Þ
where Cann,tot is the total annualized cost (€/year), Eprim,AC is AC primary load served (kW h/year), Eprim,DC is DC primary load served (kW h/year), and Egrid,sales is the total grid sales (kW h/year). The study assumes a small power plant of 20 kW capacity. A tracking system is considered in order for the PV modules to collect the maximum solar radiation. The HOMER system configuration, is shown in
Table 2 PV module specifications. Item
Specification
Manufacturer PV module type Module number Nominal efficiency PV module rating Maximum power voltage Maximum power current Open circuit voltage Short circuit current Dimensions Weight Quantity Life time Price Replacement Maintenance
Exiom solution Mono-Si EX-280 M 14.5% 280 W 36.8 V 7.61 A 43.8 V 8.52 A 1956 992 45 mm 26 kg 71 25 years 1.88 €/Wp 1.88 €/Wp 1% of price cost every year
J.G. Fantidis et al. / Solar Energy 91 (2013) 120–130 Table 3 Inverter specifications. Item
Specification
Manufacturer Module number Rated output power (@230 V, 50 Hz) Rated power frequency/rated power voltage Minimum output current Efficiency Dimensions (W H D) Weight Quantity Life time Price Replacement Maintenance
SMA solar technology Sunny mini central 7000TL 7000 W 50 Hz/230 V 31 A 97.7% 468 613 242 mm 32 kg 3 25 years 2400 € 2400 € Null
5. Results and discussion Given the global solar irradiation and the clearness index at a certain site, HOMER calculates the net energy output of the PV system. A part of this energy is lost in the inverter. CF represents the ratio of the average power produced by the power station over a year to its rated power (CF = average power output of the system/rated power). The long-term seasonal variation of global solar radiation at the 46 locations is depicted in Fig. 4. An interesting characteristic of fig. 4 should be noted; the available solar potential almost coincides with the corresponding electrical energy consumption. According from Fig. 4, it
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is obvious that higher values of solar radiation were considered during summer months and minor in the winter months. The highest value of solar radiation (7.439 kW h/m2/day) occurred in July, with the lowest (1.401 kW h/m2/day), in December. Based on the values from the 46 areas, SDS, the long-term monthly mean values of global solar radiation and the monthly average daily clearness index over Greece are shown in Fig. 5. The electricity obtained from the PV panels and the CF for the 46 locations are given in Fig. 6. In relation to Fig. 6, the maximum value of renewable energy production (41.63 kW h/year) occurs in Tymbakion and the minimum value (33.35 kW h/year) occurs in Ioannina. According to the results obtained, in all circumstances energy from PV generators is quite high, although Crete (Tymbakion, Chania, Ierapetra, Iraklion, Rethimno, Sitia, Souda), Cyclades (Milos, Naxos, Paros, Siros) and Dodecanese (Rhodes) prefectures are the more attractive areas (prefectures are shown on the map of Fig. 2). The lowest energy and CFs values are obtained in Northern Greece; Thrace (Alexandroupolis, Komotini), Macedonia (Thessaloniki, Serres, Kastoria, Chrysoupoli), and Epirus (Ioannina, Konitsa, Arta). The COE is an important parameter in every power system. The cost of generating electricity in a PV power plant has only one main component, the capital cost, because the operation and maintenance costs are negligible (presumable result for a grid connected system). Generation cost per kW h energy depends on the solar radiation. As
The average montly solar radiation kWh/m2/day 12
1.5
1.5
1.5
12
2.0 2.0
11
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
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10 9 8
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7.0
7
7 6
6
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4 3 2
2.5 2.0
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Arta Athens/Filadelfia Agrinio Mitilini Araxos Athens/Hellenkion Chios Methoni Korinthos/Velo Kalamata Argostoli Naxos Pirgos Rethimno Milos Siros Paros Andravida Chania Argos/Pirgela Kithira Rhodes Iraklion Souda Bay Samos Sitia Ierapetra Tymbakion
1 Ioannina Thessaloniki Serres Trikala Imathias Kastoria Alexandroupolis Komotini Konitsa Chrysopouli Larisa Lamia Agchialos Skiros Limnos Kerkira Zakinthos Tanagra Patra Aliartos
Month
6.5
11
Location
Fig. 4. Seasonal variation of global solar radiation for each.
1
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J.G. Fantidis et al. / Solar Energy 91 (2013) 120–130 0.65 Daily solar radiation Clearness Index
7
0.60
6 5
0.55
4 0.50
3
Clearness Index
Daily solar radiation kWh/m2/d
8
2 0.45 1 0 December
October
November
Augdust
September
July
June
May
April
March
February
January
0.40
Month Fig. 5. Monthly variation of global radiation and monthly average daily clearness index over Greece.
depicted in Fig. 7, the results show that the Aegean Archipelago islands (Crete, Cyclades and Dodecanese) have the lowest production cost of about 0.122 €/kW h while the areas in the North Greece have the higher cost (Ioannina 0.152 €/kW h). The average COE for the 46 locations is around 0.135 €/kW h. In comparison, about 50% of Greece’s electricity comes from lignite power plants with electricity production cost of 0.035–0.039 €/kW h. However in the numerous off-grid Greek Islands, the electricity production cost ranges from 0.12 up to 0.6 €/kW h (Kaldellis, 2008). It is therefore obvious that a small PV power plant produces power at very competitive prices. According to the EurObserv’ER (2011), the PV capacity installed in the European Union was ca. 13,000 MWp in
2010, resulting in a total cumulative capacity of more than 29,000 MWp. Germany is the European leader in photovoltaic energy, having 7411 MWp of cumulative installed power in 2010. Greece offers very attractive conditions for the development of PV energy (abundant resource and large number of islands visited by tourists during the sunnier months), however the growth of the Greek PV market has been rather slow (Table 4). In order to compare the results with those of other countries, the same PV power plant with the same costs was simulated for 30 European countries. The comparison utilizes the average solar radiation in each country, based on data from the PVGIS web site (Sˇu´ri et al., 2007; PVGIS, 2008). The COE and the renewable energy production are shown in Fig 8. As observed, it is obvious that Greece has one of the highest potential for solar electricity generation with small variability of PV electricity generation at the national level. Based on the data from Table 4 and the results from Fig. 8, the proposal from German Finance Minister Wolfgang Scha¨uble that Greece could export solar electricity to Germany based on a multi-billion Euro solar project (YPEKA, 2011) is logical. The idea to use money from northern countries that have higher cloud cover to produce electricity from PV panels in sunnier climates makes more sense than producing it in the clouded countries. Replacing energy generated by conventional methods (lignite, mazut, natural gas or diesel) with PV electricity could provide further benefits to Greece in the form of reduced emissions of air pollutants and GHG as the PV panels has zero GHG emissions. HOMER is capable of estimating the amount of GHG which could be avoided as a result of usage of PV generators. HOMER has six pollutants as simulation outputs: carbon dioxide (CO2), carbon monoxide (CO), unburned hydrocarbons (UHCs),
Fig. 6. Annual energy production and CF for 46 locations in Greece.
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Fig. 7. Cost of energy (COE).
Table 4 Cumulated photovoltaic capacity at the end of 2010 and photovoltaic power per inhabitant for each European Union country in 2010. Country
Installed power (MWp)
Wp/capita
Germany Spain Italy Czech Rep. France Belgium Greece Slovakia Portugal Austria Netherlands United Kingdom Slovenia Luxembourg Bulgaria Sweden Finland Denmark Cyprus Romania Poland Hungary Malta Ireland Lithuania Estonia Latvia
17,370.000 3,808.081 3,478.500 1,953.100 1,054.346 787.457 205.400 143.809 130.839 102.596 96.900 74.845 36.336 27.273 17.240 10.064 9.649 7.065 6.246 1.940 1.750 1.750 1.670 0.610 0.100 0.080 0.008
212.3 82.8 57.6 185.9 16.3 72.6 18.2 26.5 12.3 12.2 5.8 1.2 17.8 54.3 2.3 1.1 1.8 1.3 7.8 0.1 0.0 0.2 4.0 0.1 0.0 0.1 0.0
particulate matter (PM), sulfur dioxide (SO2) and nitrogen oxides (NOx). From the total emissions, more than 99% are derived from CO2; all the other pollutants have negligible effect on the results. Considering that approximately 46.16% of Greece’s electricity comes from lignite power
plants and 24.82% from natural gas generation facilities (Greek PPC, 2013), the energy supplied by the PV power plant would replace mainly lignite or natural gas fuel. According to Efthimiadis et al., the efficiency of the lignite stations in Greece is about 33% (Efthimiadis et al., 2005) and based on CO2 emission factor for lignite (0.36 kg CO2/KW h) (Quaschning, 2005), the estimated GHG emission factor is 1.09 kg CO2/KW h. In the case of natural gas, the CO2 emission factor is 0.2 kg CO2/KW h with facility efficiency approximately 34%, so the estimated GHG emission factor is 0.59 kg CO2/KW h. Calculation of the annual reduction in GHG emissions – estimated to occur if the proposed 20 kW solar PV system is implemented – was performed. The amount of GHG reduction for the 46 locations is presented in Fig. 9; the highest GHG emissions mitigation of 45.37 tons/year and 24.56 tons/year were observed for Tymbakion (replacing lignite and natural gas respectively) and the lowest reduction was observed for Ioannina, with respective values of 36.35 tons/year and 19.68 tons/year. CO2 emission pollutes the environment and plays a significant role in climate change; an indirect or hidden cost of fossil fuels, is paid by human beings. In order to quantify the benefits of GHG emission reduction, an average damage cost of 5 and 20 €/t CO2 is considered (reliant on GHG emission reduction credit from previous work by Sardi and Kromidas (2005), Al-Badi et al. (2006), Dehmas et al. (2011). Based on these values, the COE for the 46 locations are calculated as presented in Fig. 10. If clean development mechanisms, and carbon tax is considered, and bearing in mind that oil and natural gas prices are continuously increasing while PV installed prices are falling, the COE from PV is expected to be lower than the grid in a short interval of time (Bhandari and Stadler, 2009; Branker et al., 2011).
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Fig. 8. The comparison of the photovoltaic solar electricity and COE in European countries and in Greece.
Fig. 9. Green house gases reduction due usage of PV systems for different locations.
6. Conclusion Greece has high energy production potential for PV power plants. This paper presented an extended study for placement of a 20 kW PV power plant in Greece. The long-term meteorological parameters for each of the considered sites are analyzed and the results corroborate that Greece has a high content of solar radiations throughout the year. The global solar radiation varies between a minimum of 4.04 kW h/m2/day in Thessaloniki and a maximum of 4.89 kW h/m2/day in Tymbakion, while mean value remained as 4.46 kW h/m2/day. The clearness index varied between 0.488 and 0.585.
The results of energy production analysis show that the minimum value of renewable energy production is 33.35 MW h occurs in Ioannina and its maximum value is 41.63 MW h occurs in Tymbakion. Also, the minimum value of PV power plant capacity factor is 19.4% in Ioannina and its maximum value is 24.4% in Tymbakion. The average values of energy production and capacity factor for all the sites are found to be 37.61 MW h/year and 21.9%, respectively. Based on economical indicators, Tymbakion was found to be the best site for the development of PV based power plant and Ioannina the worst. From an environmental point of view, it was found that on an average of 40.99 tons or 22.19 tons of green house
J.G. Fantidis et al. / Solar Energy 91 (2013) 120–130 No penalty 5 /t CO2 penalty replacing natural gas 5 /t CO2 penalty replacing lignite 20 /t CO2 penalty replacing natural gas 20 /t CO2 penalty replacing lignite
0.15
0.14
0.15
0.14
0.11
0.11
0.10
0.10 Sitia
0.12
Ierapetra Tymbakion
0.12
Arta
0.13
Tanagra Athens/Filadelfia Patra Aliartos Araxos Agrinio Mitilini Athens/Hellenkion Kalamata Methoni Korinthos/Velo Pirgos Chios Argostoli Naxos Rethimno Andravida Siros Argos/Pirgela Kithira Paros Milos Samos Chania Iraklion Souda Bay Rhodes
0.13
Ioannina Thessaloniki Trikala Imathias Kastoria Serres Alexandroupolis Chrysopouli Komotini Konitsa Larisa Lamia Agchialos Skiros Limnos Kerkira Zakinthos
COE ( /kWh)
129
Locations
Fig. 10. The reduction on COE for different values of GHG penalties.
gases can be avoided entering into the local atmosphere each year for each implementation of PV power plant over those currently using lignite and natural gas, respectively. Since the PV investment costs are dropping significantly and the results show that the electricity from PV is already competitive in many areas in Greece, and given that grid electricity prices will continue to escalate due to rises in cost of diesel oil and natural gas, PV will become an increasingly economically beneficial source of electricity in Greece. Acknowledgement The authors are thankful to Mr. X. Levadiotis Technical, director in Terra Verde Company for providing the financial data for the example presented in this work. References Al-Badi, A.H., Albadi, M.H., Al-Lawati, A.M., Malik, A.S., 2006. Economic perspective of PV electricity in Oman. Energy 36, 226–232. Al-Karaghouli, A., Kazmerski, L.L., 2010. Optimization and life-cycle cost of health clinic PV system for a rural area in southern Iraq using HOMER software. Sol. Energy 84, 710–714. Beyer, H.G., Langer, C., 1996. A method for the identification of configurations of pv/wind hybrid systems for the reliable supply of small loads. Sol. Energy 57, 381–391. Bhandari, R., Stadler, I., 2009. Grid parity analysis of solar photovoltaic systems in Germany using experience curves. Sol. Energy 83, 1634– 1644. Branker, K., Pathak, M.J.M., Pearce, J.M., 2011. A Review of Solar Photovoltaic Levelized Cost of Electricity. Renew. Sust. Energy Rev. 15, 4470–4482. Centre for Renewable Energy Sources and Saving, 2011.. Demiroren, A., Yilmaz, U., 2010. Analysis of change in electric energy cost with using renewable energy sources in Go¨kceada, Turkey: An island example. Renew. Sust. Energy Rev. 14, 323–333.
Dehmas, D.A., Kherba, N., Hacene, F.B., Merzouk, N.K., Merzouk, M., Mahmoudi, H., Goosen, M.F.A., 2011. On the use of wind energy to power reverse osmosis desalination plant: A case study from Te´ne`s (Algeria). 15, 956–963. Dincer, F., 2011. The analysis on photovoltaic electricity generation status, potential and policies of the leading countries in solar energy. Renew. Sust. Energy Rev. 15, 713–720. Economou, A., 2010. Renewable energy resources and sustainable development in Mykonos (Greece). Renew. Sust. Energy Rev. 14, 1496–1501. Efthimiadis, A., Virvili, I., Porfiris, G., 2005. Comparative evaluation of electricity generation technologies in terms of financial and environmental efficiency. National conference for the lignite and natural gas in the national electricity generation. Technical chamber of Greece, 9–10 June 2005, Athens, Greece. Exiom Solution, S.A., 2012.. HNMS, 2011. Hellenic National Meteorological Service.
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Mirasgedis, S., Sarafidis, Y., Georgopoulou, E., Lalas, D.P., 2002. The role of renewable energy sources within the framework of the Kyoto Protocol: the case of Greece. Renew. Sust. Energy Rev. 6, 249–272. Homer, NREL (National Renewable Energy Laboratory), HOMER Computer Software, Version 2.68 beta. Retrieved from https:// analysis.nrel.gov/homer/S, 2011. Ntziachristos, L., Kouridis, Ch., Samaras, Z., Pattas, K., 2005. A windpower fuel-cell hybrid system study on the non-interconnected Aegean islands grid. Renew. Energy 30, 1471–1487. Official Journal of the Hellenic Republic. 261/A/23.12.2004. pp. 6373– 6399.. Official Journal of the Hellenic Republic. 129/A/27.06.2006. pp. 1405– 1426. . Photovoltaic Geographical Information System (PVGIS), 2008.
Rehman, S., Bader, M.A., Al-Moallem, S.A., 2007. Cost of solar energy generated using PV panels. Renew. Sust. Energy Rev. 11, 1843–1857. Sardi, K., Kromidas, T., 2005. Future Development in the World GHG Market. In: 10th National Conference of Energy & Development, 7–9 December 2005, Athens, Greece. Sims, R.E.H., 2004. Renewable energy: a response to climate change. Sol. Energy 76, 9–17. SMA, 2012. Solar Technology AG.
Solar Energy 91 (2013) 120–130 www.elsevier.com/locate/solener
Cost of PV electricity – Case study of Greece J.G. Fantidis, D.V. Bandekas ⇑, C. Potolias, N. Vordos Dpt. of Electrical Engineering, Kavala Institute of Technology, St. Lukas, P.O. 65 404, Greece Received 11 July 2011; received in revised form 14 November 2012; accepted 5 February 2013 Available online 22 March 2013 Communicated by: Associate Editor S.C. Bhattacharya
Abstract The potential for a 20 kW photovoltaic (PV) power plant in Greece is examined in this study. HOMER software is used to predict energy production, cost of energy and reduction of green house gasses (GHGs) emissions. The long-term meteorological parameters for 46 sites in Greece being considered by the Centre for Renewable Energy Sources and Saving (CRES) are analyzed. The global solar radiation varies between a minimum of 4.04 kW h/m2/day in Ioannina and a maximum of 4.89 kW h/m2/day in Tymbakion, while the mean value for the 46 locations remained as 4.46 kW h/m2/day. The renewable energy produced each year from the PV power plant varied between 33.35 MW h in Ioannina and 41.63 MW h in Tymbakion while the average value for the 46 locations is 37.61 MW h. The results of the financial analysis demonstrate that a PV power plant can operate profitably at any of the considered sites in Greece. The capacity factor of a PV plant varies between 19.4% and 24.2% and the cost of electricity varies between 0.122 €/kW h and 0.152 €/ kW h from the most appropriate location to the least attractive location respectively. Bearing in mind that the electricity cost for consumers in Greece is approximately 0.13 €/kW h, the present study demonstrates that photovoltaics can play an important role in Greek energy generation. Last but not least, utilization of photovoltaics means that considerable quantity of CO2 is not released into the local atmosphere each year. Ó 2013 Elsevier Ltd. All rights reserved. Keywords: Renewable energy; HOMER; Solar radiation; Photovoltaic; Solar energy; GHG emissions
1. Introduction Energy is a fundamental ingredient in economic development and energy consumption is an index of prosperity and the standard of living. The consumption of energy per capita has increased significantly in the last number of decades, as the standard of living has improved. Renewable energy is a sustainable and clean source of energy derived from nature. Renewable energy technology is one of the solutions, which produces energy by transforming natural phenomena (or natural resources) into useful energy forms (Dincer, 2011), helps to ensure security of energy supply (Kattakayam and Srinivasan, 1996; Beyer and Langer, 1996), and contributes to the meeting of the ⇑ Corresponding author. Tel.: +30 2510462132.
E-mail address: [email protected] (D.V. Bandekas). 0038-092X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.solener.2013.02.001
Kyoto Protocol objectives (Wohlgemuth and Missfeldt, 2000; Mirasgedis et al., 2002; Sims, 2004; Lund, 2006). Greece is mainly a mountainous country with many variously sized scattered islands, which cover their electricity demand with the utilization of aged autonomous lignite, diesel–oil, natural gas, and mazut (a third of Greece’s electricity is produced from oil and gas) power stations. As a result, the cost of electricity production is extremely high on most islands (Greek PPC, 2013; Kaldellis et al., 2009). The sun is a clean and renewable energy source. Solar energy is a non-depletable, site-dependent source of alternative energy. Among several available technologies, solar PV is the most promising. PV conversion is the direct conversion of sunlight into direct current electricity without the need for a heat engine. The PV process produces power silently and is low maintenance as there are no moving parts. The largest advantage of PV devices is the breadth
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of their power output, ranging from microwatts to megawatts. Greece is one of Europe’s sunnier regions; the annual solar energy approaches 1800 kW h m2 (Fig. 1) (Kaldellis et al., 2002; PVGIS, 2008). The Greek islands in particular possess a very high solar potential and PV electricity offers an economically-attractive solution. Furthermore the solar potential and the seasonal electricity load in Greece are consistent, with higher values during the summer months and lower values during winter. Greece has a range of legislative regulations that have been established for the promotion of renewable energy sources such as development law 3299/2004, as well as 3468/2006, in relation to which the investment is strengthened with reference to the production of electric energy from renewable energy sources. PV systems development constitutes part of the Promotion of Electric Energy Production from Renewable Energy Sources program which operates until 2020 (OJHR, 2004, 2006; Economou, 2010). Law 3299/04 is the “National Development Law” that is applicable to enterprises involved in any economic activity in the country. Regions with high unemployment rates and low income per capita receive the highest investment
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subsidies from the state. Investments in renewable energy systems keep their favoured status under this Law, through investments in high technology, environmental protection, tourism, etc. The funding subsidizes the total investment cost and can amount to 20–60% depending on the region and the size of the company (OJHR, 2004). Law 3468/ 2006 was enacted (from the 6th of June 2006), in order to speed up the licensing procedures and to reform electric energy production from renewable energy. Among others, law 3468/2006 increases the guaranteed market price up to fivefold (for the PV systems), expands the market time from 10 to 20 years and reduces licensing deadlines (OJHR, 2006). In this paper making use of the average daily global solar radiation and clearness index data for 46 locations in Greece, the annual energy production, the economic analysis and the environmental considerations calculated using HOMER software. Locations derived from each of the four climatic zones, in which Greece can be divided (Technical Chamber of Greece, 2010) and not only from areas with good solar potential. HOMERs (Hybrid Optimization Model for Electric Renewables) is a modelling tool that facilitates design of electric power systems. The
Fig. 1. Global solar radiation in Europe.
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assessment criterion of the analysis is the cost of energy (COE). The project assumes a solar PV power plant of 20 kW at each of the 46 locations to calculate the COE, the Capacity Factor (CF) and potential emission reduction due to the PV array (Rehman et al., 2007; Al-Badi et al., 2006).
2. Case study (Greece) It is widely acknowledged that Greece possesses an excellent solar energy potential according to existing long-term measurements, presented in Fig. 1. More specifically, Greece is located in the SE Mediterranean area with an affluent and reliable supply of solar energy, even during the winter. The entire Greek territory is characterized by high solar irradiance, hence the annual solar energy at horizontal plane varies between 1450 kW h/m2 and 1800 kW h/m2 (Fig. 2). From Fig. 2, it is obvious that the south areas in Greece especially the Aegean
Archipelago islands have the highest values of global solar radiation, while less solar irradiance is to be expected in Northern Greece (Kaldellis et al., 2002; PVGIS, 2008). The electricity network of Greece may be divided into two; first is the main-land national grid, based largely on the operation of centralized Thermal Power Stations (mainly based on the local lignite reserves). The second consists of several thousand remote consumers, mainly in the Aegean and Ionian Archipelago areas, located on the several small and medium-sized scattered islands. In these areas the electricity production cost is extremely high (Ntziachristos et al., 2005; Kaldellis et al., 2009) due to the utilization of outdated autonomous power stations based on oil-fuel imports and diesel electric generators.
3. Solar resource In order to calculate the performance of a PV system it is necessary to collect the meteorological data for the site
Fig. 2. Global solar radiation in Greece.
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under consideration. The Centre for Renewable Energy Sources and Saving (CRES, 2011), a source for this data, is the Greek national entity for the promotion of renewable energy sources, rational use of energy and energy conservation. In the present study, 46 representative locations covering all areas of Greece have been identified for solar radiation resource assessment. CRES deduced these long term (1955–1997) meteorological parameters (includes data for wind speed, solar radiation, clearness index, heating degree-days, cooling degree-days, relative humidity) from the Hellenic National Meteorological Service (HNMS, 2011). The average daily solar radiation and the average daily clearness index (both available from CRES) at these locations are given in Table 1 and used as index of the solar
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potential of each of the 46 locations. The clearness index is a dimensionless number (0–1) indicating the fraction of the solar radiation striking the top of the atmosphere that makes it through the atmosphere to strike the Earth’s surface. The following equation defines the monthly average clearness index: K T ¼ H ave =H o;ave
ð1Þ
where Have is the monthly average radiation on the horizontal surface of the earth (kW h/m2/day) and Ho,ave is the extraterrestrial horizontal radiation, meaning the radiation on a horizontal surface at the top of the earth’s atmosphere (kW h/m2/day). The geography in terms of
Table 1 Long-term daily mean values of global solar radiation and the correspondingly clearness index. No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46
City Agchialos Agrinio Alexandroupolis Aliartos Andravida Araxos Argos/pirgela Argostoli Arta Athens/filadelfia Athens/hellenkion Chania Chios Chrysopouli Ierapetra Ioannina Iraklion Kalamata Kastoria Kerkira Komotini Konitsa Korinthos/velo Lamia Larisa Limnos Methoni Milos Mitilini Naxos Paros Patra Pirgos Rethimno Rhodes Samos Serres Siros Sitia Skiros Souda bay Tanagra Thessaloniki Trikala imathias Tymbakion Zakinthos
Latitude N 39° 38° 40° 38° 37° 38° 37° 38° 37° 38° 37° 35° 38° 40° 35° 39° 35° 37° 40° 39° 40° 41° 40° 38° 39° 39° 36° 36° 39° 37° 37° 38° 37° 35° 36° 37° 41° 37° 35° 38° 35° 38° 40° 40° 35° 39°
0
13 370 510 230 550 090 360 110 470 030 540 290 280 540 000 420 200 040 270 370 180 070 030 510 390 550 500 430 040 060 010 150 400 210 240 420 050 250 120 540 330 190 310 360 000 100
Longitude E 22° 21° 25° 23° 21° 21° 22° 20° 20° 23° 23° 24° 26° 24° 25° 20° 25° 22° 21° 19° 21° 25° 20° 22° 22° 25° 21° 24° 26° 25° 25° 21° 21° 24° 28° 26° 23° 24° 26° 24° 24° 23° 22° 22° 24° 21°
0
48 230 560 060 170 250 470 290 540 400 450 070 080 360 440 490 110 000 170 550 470 240 450 240 270 140 420 270 360 230 080 440 180 310 070 550 340 570 060 330 070 330 580 330 460 000
Elevation (m)
Daily solar radiation (kWh/m2/day)
Clearness index
15.3 25 3.5 110 15.1 11.5 11.2 22 7.9 138 15 150 5 5.4 10 484 39.3 11.1 660.9 4 625 30 542 17.4 73.6 4.6 33 182 4 9.8 33.5 1 12 7 11.5 7.3 34.5 72 115.6 17.9 151.6 140.1 4.8 0.8 6.7 10.5
4.30 4.44 4.12 4.40 4.65 4.45 4.66 4.59 4.42 4.41 4.48 4.66 4.55 4.16 4.87 4.04 4.71 4.58 4.08 4.35 4.15 4.16 4.56 4.28 4.25 4.33 4.56 4.62 4.44 4.59 4.65 4.39 4.61 4.61 4.70 4.73 4.05 4.63 4.74 4.32 4.73 4.39 4.05 4.07 4.89 4.38
0.523 0.537 0.506 0.521 0.560 0.535 0.540 0.543 0.524 0.532 0.538 0.540 0.542 0.520 0.570 0.489 0.546 0.537 0.506 0.530 0.512 0.510 0.540 0.515 0.522 0.568 0.538 0.535 0.542 0.550 0.534 0.534 0.535 0.557 0.567 0.532 0.518 0.523 0.537 0.550 0.585 0.536 0.493 0.512 0.571 0.543
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latitude, longitude and elevation from the sea level is also presented in Table 1. HOMER (2011) uses the following equation to estimate the output of the PV array: P PV ¼ Y PV fPV
GT ½1 þ ap ðT c T c;STC Þ GT ;STC
ð2Þ
where YPV is the rated capacity of the PV array, meaning its power output under standard test conditions (kW), fPV is the PV derating factor (%), is the solar radiation incident on the PV array in the current time step (kW/m2), is the incident radiation at standard test conditions (1 kW/ m2), Tc is the PV cell temperature in the current time step (°C), and Tc,STC is the PV cell temperature under standard test conditions (25 °C). In the present study the derating factor was taken as 90%, which compensates for reduction in efficiency due to temperature, dust and wiring losses (Demiroren and Yilmaz, 2010; Al-Karaghouli and Kazmerski, 2010). HOMER simulates the operation of a system by making energy balance calculations for each of the 8760 h in a year. Because the measured hourly solar radiation data is rarely available, it is often necessary to use HOMER’s capability to generate synthetic hourly solar data from monthly averages. The algorithm that HOMER uses to synthesize solar data is based on the work of Graham and Hollands (1990). This algorithm produces realistic hourly data and it is easy to use because it requires only the latitude and the monthly averages. HOMER handles the PV panels in terms of rated kW and not in m2 and for this reason it does not need the efficiency. HOMER assumes the PV panels always operate at the maximum power point, as it would if they were controlled by a maximum power point tracker. Finally HOMER supposes that the output of the PV panel is linearly proportional to the incident radiation; consequently if the radiation is 0.75 kW/m2, the panels will produce 75% of their rated output.
Fig. 3. System configuration in HOMERENERGY.
Fig. 3. According to this architecture, there are three main components to the system; PV panels, a converter and the public grid. The generated energy is sent to the grid. The DC and AC lines are connected via the inverter (converter); the DC power from the PV modules is converted into AC power and fed into the grid system using the inverters. Owing to the dramatic decrease in the cost of PV panels over the last number of years, the current (February 2012) wholesale price of a simple PV panel is approximately 0.72 €/Wp, excluding transportation cost. However, the retail price for a customer is more than twice that value (1.88 €/Wp) since a small power plant additionally requires other components such as wires, switches, inverters, tracker costs, and labor for installing solar modules – these represent more than half the cost of a solar power system. These components are collectively referred to as the “balance of system” (BOS). BOS manufacturers could significantly reduce their costs (and thus lower costs for the whole industry) by implementing techniques—such as modularization, preassembly, standardization, and automation. The best price for a small 20 kW (19.88 kW for the correctness of a description) power plant in Greece is approximately 67,000 € (Levadiotis, 2012). Each of the utilized PV modules has a rated power of 280 W and other specifications shown in Table 2 (Exiom, 2012). Table 3 shows the technical data for the inverters (SMA, 2012). The project lifetime has been considered to be 25 years and the annual real interest rate has been taken as 5%.
4. Economic analysis of energy system HOMER defines the levelized COE as the average cost/ kW h of electrical energy produced by the system. In order to calculate the COE, HOMER divides the annualized cost of producing electricity by the total useful electric energy production. According to the HOMER software, the equation for the COE is as follows: COE ¼
C ann;tot Eprim;AC þ Eprim;DC þ Egrid;sales
ð3Þ
where Cann,tot is the total annualized cost (€/year), Eprim,AC is AC primary load served (kW h/year), Eprim,DC is DC primary load served (kW h/year), and Egrid,sales is the total grid sales (kW h/year). The study assumes a small power plant of 20 kW capacity. A tracking system is considered in order for the PV modules to collect the maximum solar radiation. The HOMER system configuration, is shown in
Table 2 PV module specifications. Item
Specification
Manufacturer PV module type Module number Nominal efficiency PV module rating Maximum power voltage Maximum power current Open circuit voltage Short circuit current Dimensions Weight Quantity Life time Price Replacement Maintenance
Exiom solution Mono-Si EX-280 M 14.5% 280 W 36.8 V 7.61 A 43.8 V 8.52 A 1956 992 45 mm 26 kg 71 25 years 1.88 €/Wp 1.88 €/Wp 1% of price cost every year
J.G. Fantidis et al. / Solar Energy 91 (2013) 120–130 Table 3 Inverter specifications. Item
Specification
Manufacturer Module number Rated output power (@230 V, 50 Hz) Rated power frequency/rated power voltage Minimum output current Efficiency Dimensions (W H D) Weight Quantity Life time Price Replacement Maintenance
SMA solar technology Sunny mini central 7000TL 7000 W 50 Hz/230 V 31 A 97.7% 468 613 242 mm 32 kg 3 25 years 2400 € 2400 € Null
5. Results and discussion Given the global solar irradiation and the clearness index at a certain site, HOMER calculates the net energy output of the PV system. A part of this energy is lost in the inverter. CF represents the ratio of the average power produced by the power station over a year to its rated power (CF = average power output of the system/rated power). The long-term seasonal variation of global solar radiation at the 46 locations is depicted in Fig. 4. An interesting characteristic of fig. 4 should be noted; the available solar potential almost coincides with the corresponding electrical energy consumption. According from Fig. 4, it
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is obvious that higher values of solar radiation were considered during summer months and minor in the winter months. The highest value of solar radiation (7.439 kW h/m2/day) occurred in July, with the lowest (1.401 kW h/m2/day), in December. Based on the values from the 46 areas, SDS, the long-term monthly mean values of global solar radiation and the monthly average daily clearness index over Greece are shown in Fig. 5. The electricity obtained from the PV panels and the CF for the 46 locations are given in Fig. 6. In relation to Fig. 6, the maximum value of renewable energy production (41.63 kW h/year) occurs in Tymbakion and the minimum value (33.35 kW h/year) occurs in Ioannina. According to the results obtained, in all circumstances energy from PV generators is quite high, although Crete (Tymbakion, Chania, Ierapetra, Iraklion, Rethimno, Sitia, Souda), Cyclades (Milos, Naxos, Paros, Siros) and Dodecanese (Rhodes) prefectures are the more attractive areas (prefectures are shown on the map of Fig. 2). The lowest energy and CFs values are obtained in Northern Greece; Thrace (Alexandroupolis, Komotini), Macedonia (Thessaloniki, Serres, Kastoria, Chrysoupoli), and Epirus (Ioannina, Konitsa, Arta). The COE is an important parameter in every power system. The cost of generating electricity in a PV power plant has only one main component, the capital cost, because the operation and maintenance costs are negligible (presumable result for a grid connected system). Generation cost per kW h energy depends on the solar radiation. As
The average montly solar radiation kWh/m2/day 12
1.5
1.5
1.5
12
2.0 2.0
11
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
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4 3 2
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Arta Athens/Filadelfia Agrinio Mitilini Araxos Athens/Hellenkion Chios Methoni Korinthos/Velo Kalamata Argostoli Naxos Pirgos Rethimno Milos Siros Paros Andravida Chania Argos/Pirgela Kithira Rhodes Iraklion Souda Bay Samos Sitia Ierapetra Tymbakion
1 Ioannina Thessaloniki Serres Trikala Imathias Kastoria Alexandroupolis Komotini Konitsa Chrysopouli Larisa Lamia Agchialos Skiros Limnos Kerkira Zakinthos Tanagra Patra Aliartos
Month
6.5
11
Location
Fig. 4. Seasonal variation of global solar radiation for each.
1
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J.G. Fantidis et al. / Solar Energy 91 (2013) 120–130 0.65 Daily solar radiation Clearness Index
7
0.60
6 5
0.55
4 0.50
3
Clearness Index
Daily solar radiation kWh/m2/d
8
2 0.45 1 0 December
October
November
Augdust
September
July
June
May
April
March
February
January
0.40
Month Fig. 5. Monthly variation of global radiation and monthly average daily clearness index over Greece.
depicted in Fig. 7, the results show that the Aegean Archipelago islands (Crete, Cyclades and Dodecanese) have the lowest production cost of about 0.122 €/kW h while the areas in the North Greece have the higher cost (Ioannina 0.152 €/kW h). The average COE for the 46 locations is around 0.135 €/kW h. In comparison, about 50% of Greece’s electricity comes from lignite power plants with electricity production cost of 0.035–0.039 €/kW h. However in the numerous off-grid Greek Islands, the electricity production cost ranges from 0.12 up to 0.6 €/kW h (Kaldellis, 2008). It is therefore obvious that a small PV power plant produces power at very competitive prices. According to the EurObserv’ER (2011), the PV capacity installed in the European Union was ca. 13,000 MWp in
2010, resulting in a total cumulative capacity of more than 29,000 MWp. Germany is the European leader in photovoltaic energy, having 7411 MWp of cumulative installed power in 2010. Greece offers very attractive conditions for the development of PV energy (abundant resource and large number of islands visited by tourists during the sunnier months), however the growth of the Greek PV market has been rather slow (Table 4). In order to compare the results with those of other countries, the same PV power plant with the same costs was simulated for 30 European countries. The comparison utilizes the average solar radiation in each country, based on data from the PVGIS web site (Sˇu´ri et al., 2007; PVGIS, 2008). The COE and the renewable energy production are shown in Fig 8. As observed, it is obvious that Greece has one of the highest potential for solar electricity generation with small variability of PV electricity generation at the national level. Based on the data from Table 4 and the results from Fig. 8, the proposal from German Finance Minister Wolfgang Scha¨uble that Greece could export solar electricity to Germany based on a multi-billion Euro solar project (YPEKA, 2011) is logical. The idea to use money from northern countries that have higher cloud cover to produce electricity from PV panels in sunnier climates makes more sense than producing it in the clouded countries. Replacing energy generated by conventional methods (lignite, mazut, natural gas or diesel) with PV electricity could provide further benefits to Greece in the form of reduced emissions of air pollutants and GHG as the PV panels has zero GHG emissions. HOMER is capable of estimating the amount of GHG which could be avoided as a result of usage of PV generators. HOMER has six pollutants as simulation outputs: carbon dioxide (CO2), carbon monoxide (CO), unburned hydrocarbons (UHCs),
Fig. 6. Annual energy production and CF for 46 locations in Greece.
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Fig. 7. Cost of energy (COE).
Table 4 Cumulated photovoltaic capacity at the end of 2010 and photovoltaic power per inhabitant for each European Union country in 2010. Country
Installed power (MWp)
Wp/capita
Germany Spain Italy Czech Rep. France Belgium Greece Slovakia Portugal Austria Netherlands United Kingdom Slovenia Luxembourg Bulgaria Sweden Finland Denmark Cyprus Romania Poland Hungary Malta Ireland Lithuania Estonia Latvia
17,370.000 3,808.081 3,478.500 1,953.100 1,054.346 787.457 205.400 143.809 130.839 102.596 96.900 74.845 36.336 27.273 17.240 10.064 9.649 7.065 6.246 1.940 1.750 1.750 1.670 0.610 0.100 0.080 0.008
212.3 82.8 57.6 185.9 16.3 72.6 18.2 26.5 12.3 12.2 5.8 1.2 17.8 54.3 2.3 1.1 1.8 1.3 7.8 0.1 0.0 0.2 4.0 0.1 0.0 0.1 0.0
particulate matter (PM), sulfur dioxide (SO2) and nitrogen oxides (NOx). From the total emissions, more than 99% are derived from CO2; all the other pollutants have negligible effect on the results. Considering that approximately 46.16% of Greece’s electricity comes from lignite power
plants and 24.82% from natural gas generation facilities (Greek PPC, 2013), the energy supplied by the PV power plant would replace mainly lignite or natural gas fuel. According to Efthimiadis et al., the efficiency of the lignite stations in Greece is about 33% (Efthimiadis et al., 2005) and based on CO2 emission factor for lignite (0.36 kg CO2/KW h) (Quaschning, 2005), the estimated GHG emission factor is 1.09 kg CO2/KW h. In the case of natural gas, the CO2 emission factor is 0.2 kg CO2/KW h with facility efficiency approximately 34%, so the estimated GHG emission factor is 0.59 kg CO2/KW h. Calculation of the annual reduction in GHG emissions – estimated to occur if the proposed 20 kW solar PV system is implemented – was performed. The amount of GHG reduction for the 46 locations is presented in Fig. 9; the highest GHG emissions mitigation of 45.37 tons/year and 24.56 tons/year were observed for Tymbakion (replacing lignite and natural gas respectively) and the lowest reduction was observed for Ioannina, with respective values of 36.35 tons/year and 19.68 tons/year. CO2 emission pollutes the environment and plays a significant role in climate change; an indirect or hidden cost of fossil fuels, is paid by human beings. In order to quantify the benefits of GHG emission reduction, an average damage cost of 5 and 20 €/t CO2 is considered (reliant on GHG emission reduction credit from previous work by Sardi and Kromidas (2005), Al-Badi et al. (2006), Dehmas et al. (2011). Based on these values, the COE for the 46 locations are calculated as presented in Fig. 10. If clean development mechanisms, and carbon tax is considered, and bearing in mind that oil and natural gas prices are continuously increasing while PV installed prices are falling, the COE from PV is expected to be lower than the grid in a short interval of time (Bhandari and Stadler, 2009; Branker et al., 2011).
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Fig. 8. The comparison of the photovoltaic solar electricity and COE in European countries and in Greece.
Fig. 9. Green house gases reduction due usage of PV systems for different locations.
6. Conclusion Greece has high energy production potential for PV power plants. This paper presented an extended study for placement of a 20 kW PV power plant in Greece. The long-term meteorological parameters for each of the considered sites are analyzed and the results corroborate that Greece has a high content of solar radiations throughout the year. The global solar radiation varies between a minimum of 4.04 kW h/m2/day in Thessaloniki and a maximum of 4.89 kW h/m2/day in Tymbakion, while mean value remained as 4.46 kW h/m2/day. The clearness index varied between 0.488 and 0.585.
The results of energy production analysis show that the minimum value of renewable energy production is 33.35 MW h occurs in Ioannina and its maximum value is 41.63 MW h occurs in Tymbakion. Also, the minimum value of PV power plant capacity factor is 19.4% in Ioannina and its maximum value is 24.4% in Tymbakion. The average values of energy production and capacity factor for all the sites are found to be 37.61 MW h/year and 21.9%, respectively. Based on economical indicators, Tymbakion was found to be the best site for the development of PV based power plant and Ioannina the worst. From an environmental point of view, it was found that on an average of 40.99 tons or 22.19 tons of green house
J.G. Fantidis et al. / Solar Energy 91 (2013) 120–130 No penalty 5 /t CO2 penalty replacing natural gas 5 /t CO2 penalty replacing lignite 20 /t CO2 penalty replacing natural gas 20 /t CO2 penalty replacing lignite
0.15
0.14
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Ierapetra Tymbakion
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Arta
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Tanagra Athens/Filadelfia Patra Aliartos Araxos Agrinio Mitilini Athens/Hellenkion Kalamata Methoni Korinthos/Velo Pirgos Chios Argostoli Naxos Rethimno Andravida Siros Argos/Pirgela Kithira Paros Milos Samos Chania Iraklion Souda Bay Rhodes
0.13
Ioannina Thessaloniki Trikala Imathias Kastoria Serres Alexandroupolis Chrysopouli Komotini Konitsa Larisa Lamia Agchialos Skiros Limnos Kerkira Zakinthos
COE ( /kWh)
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Fig. 10. The reduction on COE for different values of GHG penalties.
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