Designing an optimal solar collector (orientation, type and size) for a hybrid-CCHP system in different climates

Energy and Buildings 108 (2015) 10–22

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Designing an optimal solar collector (orientation, type and size) for a hybrid-CCHP system in different climates Masood Ebrahimi a,∗ , Ali Keshavarz b a b

University of Kurdistan, Sanandaj, Iran Mechanical Engineering Faculty, K. N. Toosi University of Technology, Vanak Sq., Molla Sadra St., Tehran, Iran

a r t i c l e

i n f o

Article history: Received 10 October 2014 Received in revised form 30 July 2015 Accepted 30 August 2015 Available online 1 September 2015 Keywords: CCHP Solar collector Residential building Climate

a b s t r a c t The purpose of this research is to determine the optimum orientation and size of a solar collector to be integrated with a basic-CCHP system. The basic-CCHP includes an internal combustion engine; absorption chiller and possible auxiliary boiler but the hybrid-CCHP is the basic-CCHP plus a solar collector to provide a portion of the thermal energy demand of the consumer. Maximum rectangle method is used to size the prime mover. Size of other components depends on the engine size and building demands. The building which the hybrid-CCHP is supposed to be designed for is a residential building. The optimum conditions for the solar collector are determined in five different climates, and the privileges of using a hybrid-CCHP system instead of the basic-CCHP system are discussed. Furthermore, the impact of full load and partial load operation of engine on the fuel energy saving ratio (FESR) of the basic-CCHP and hybrid-CCHP is discussed. The results showed that for the hybrid-CCHP more FESR is achieved in partial load operation of engine, on the contrary, for the basic-CCHP the FESR is higher when the engine operates in full load. © 2015 Elsevier B.V. All rights reserved.

1. Introduction Combined cooling heating and power (CCHP) which is also known as trigeneration, is a new technology that uses fuel and recoverable heat to produce cooling, heating, domestic hot water and electricity demands of a consumer. The basic-CCHP systems comprises of a prime mover that uses fuel energy to produce electricity. It also has a heat recovery system which can use the recoverable heat for heating or cooling purposes. The cooling system type depends on the recovered heat quality, and is usually chosen among different types of thermally activated cooling systems such as absorption and adsorption chillers. If the recovered heat does not meet the heating or cooling demands of the building, an auxiliary boiler can be utilized to compensate the lack of heat demand. In some cases, compression chiller can be used in conjunction with the thermally activated chillers to fulfill the cooling demand. The ability of CCHP systems to increase the overall efficiency, decrease the fuel consumption and pollution is well proven. In addition the CCHP systems can be designed to achieve economical profits through selling electricity in non-peak hours, and fuel consumption reduction.

∗ Corresponding author. E-mail addresses: [email protected] (M. Ebrahimi), [email protected] (A. Keshavarz). http://dx.doi.org/10.1016/j.enbuild.2015.08.056 0378-7788/© 2015 Elsevier B.V. All rights reserved.

A comprehensive study about the CCHP systems, the technologies used in these systems, environmental and economical indices are presented in [1,2]. They have also presented performance curves of the prime movers that are commonly used in the CCHP cycles. In addition [1] presented a study about different thermally activated cooling systems, their types, performances, costs etc. Ref. [3] also focused on the mini-, micro- turbines as an opportunity to be used in the cogeneration systems. This research also presents good data about the advantages, manufacturers, market, and the future of the mini-, micro-gas turbines in the cogeneration systems such as the CCHP applications. Ref [4] presented an energy, exergy, and economical evaluation of a CCHP cycle which is advised to be used for light commercial applications. The economical evaluations show a very good payback period of less than 3 years. Another advantage of the CCHP systems is their compatibility with different fuel sources such as land fill gases. Ref. [5] proposed a land fill gas (LFG) CCHP system. The LFG-CCHP system consists of three main sub-sections of LFG collection system, LFG processing system and the CCHP system itself. The composition of the LFG includes about 50% methane, 45% carbon dioxide, 5% nitrogen, and less than 1% oxygen. Other components include hydrogen sulfide (H2 S), halides, and non-methane organic compounds [5]. In this research the net present value is calculated for the economical evaluations; primary energy saving is calculated for the energy consumption evaluation and green house gas (GHG) reduction as the environmental assessment. Process capability can be

M. Ebrahimi, A. Keshavarz / Energy and Buildings 108 (2015) 10–22

Nomenclature A Aco AH ATD az G B C K CCHP CHP COP CSP D DL E FESR Fsg Fss H HR LAT MRM Q qu RH RI T UL

apparent extraterrestrial irradiation (W/m2 ) collector area (m2 ) solar angular hour (deg) aggregated thermal demand (kW) Azimuth angle (deg) atmospheric extinction coefficient boiler size (kW) cooling load (kW) ratio of diffuse radiation on horizontal surface to direct normal irradiation combined cooling heating and power combined heating and power coefficient of performance (%) conventional separate production of energy domestic hot water (kW) day length (HR) electricity (kW) fuel energy saving ratio (%) angle factor between surface and earth angle factor between the surface and sky heating load (kW) hour latitude angle of collector position (deg) maximum rectangle method heat (kW) useful heat gained by collector (W M−2 ) relative humidity (%) radiation intensity (W/m2 ) temperature (◦ C) upward heat loss coefficient (W m−2 K−1 )

Subscripts abc absorption chiller amb ambient co collector building demand dem dH diffuse radiation falling on a horizontal surface DN direct normal diffuse radiation d max,min maximum, minimum nom nominal size opt optimum absorber plate of collector p re reflectance rec recoverable rs recoverable and solar total horizontal irradiation tH t total solar irradiation Greek symbols  solar longitude (deg) transmittance of cover  g reflectance of the foreground

characterized by feasibility and flexibility of the system. Feasibility is prior to flexibility. Feasibility of a system refers to its ability to handle the energy demand at any time. Flexibility refers to the ability of a feasible system to handle different operation modes conditions. The feasibility and flexibility of the CCHP systems is studied in [6]. They focused on proposing a feasible and flexible CCHP system for a commercial complex building. A CCHP cycle which is operating based on a Rankine cycle and a jet ejector for the

11

cooling system is proposed by Ref. [7]. They calculated the energy and exergy criteria of the cycle. Solar systems can be used as photovoltaic panels to provide solar electricity or as heating collectors for heating purposes. To increase the advantages of the CCHP systems, they can be integrated with solar systems. Ref. [8] presented an experimental CCHP that combined a CHP with an ejector heat pump cycle to provide cooling, heating and power of a residential building. They presented two set-ups; one was connected to 20 m2 of solar collector and the other was connected to a gas burner. They also examined the impact of using three refrigerants of n-pentane, R134a and water on the cooling cycle performance. Ref. [9] presented a hybrid-CHP system that works with natural gas and solar heat. The cycle was tested with two working fluids of n-pentane and HFE-301 and finally the HFE301 was chosen as the working fluid. The overall efficiency of the systems presented by [8,9] is too low, because no proper designing procedure or optimization is applied to the cycle. A CCHP cycle that uses a steam turbine as the prime mover and solar energy as the only energy resource is presented by [10]. In this cycle a compound parabolic solar collector produces steam by vaporizing R123 as the working fluid. An extraction from the turbine is used in an ejector refrigeration cycle to produce the cooling load. The direction of the collector is also optimized to reach the maximum exergy efficiency and CCHP performance. Solar systems can be optimized to provide the domestic hot water as well. Finding the best criteria for evaluation of solar domestic water heater system has been the main concern of researchers [11]. They used energetic, exergetic, environmental and financial criteria as the optimization functions and compared their results to find the best criteria for optimization. A solar water heater can also be used as the heat source of thermally activated cooling systems. Coupling a thermal energy storage system can magnify the advantages of the solar system. A solar water heater is used as the engine of an adsorption chiller for the purposes of heat and mass recovery by some researchers [12]. A heat storage tank is also used to save the extra solar heat for the time when more heat is needed or solar radiation is weak. The heat is used to regenerate silica-gel in the adsorption chiller. Different aspects of solar photovoltaic technologies is reviewed and discussed in [13]. They discussed the light absorbing materials used in the photovoltaic cells, their reliability, performance, environmental aspects, control, and applications. In another application of solar systems, an adsorption chiller is couple with an activated carbon-methanol pair and the simulation is presented in [14]. A new CCHP cycle that proposed by [15] combined a closed gas turbine cycle with heat recovery and ejector refrigeration system at the exhaust of the turbine. The working fluid is CO2 which is heated through a heat exchanger that receives heat from a solar parabolic collector and auxiliary heater. In addition a heat storage tank is used to save the extra solar heat and reuse it when needed. Adsorption chillers are able to produce cooling with low quality heat sources below 90 ◦ C. Therefore they can be used as the heat recovery chillers to use the waste heat of prime movers in the CCHP systems. They are especially useful to be integrated with the CCHP systems based on the internal combustion engines, because they produce three quality levels of heat source in the exhaust, water jacketing of the engine and lube oil system. Ref. [17] presented an investigation about a solar powered double stage, four-bed silica gel-water adsorption chiller to be operated in Durgapur, India. For the heat source temperature of above 60 ◦ C the chiller operates as single stage, while at temperature lower than 60 ◦ C it works as double stage adsorption chiller. The solar system is plate collector or evacuated tubes. The results showed that the chiller was able produce cooling during the whole year even at heat source temperatures as low as 40 ◦ C. Researchers in [18], presented numerical and experimental investigation of a micro-CHP

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M. Ebrahimi, A. Keshavarz / Energy and Buildings 108 (2015) 10–22

Fig. 1. Schematic of hybrid-CCHP and CSP.

system. The results showed 21% and 27% of energy cost saving in mid-Atlantic and Great Lakes regions of United States. In addition the experimental and simulation results agreed with a good precision for similar load profile of a model building during different time spans of summer, spring, or autumn. Another experimental and simulation investigation on a micro-CCHP is presented by [19]. The micro-CCHP of this research consists of three main components of internal combustion engine, adsorption chiller, and thermal management controller. The thermal management controller is used to manage the heat recovery from the engine. It may be used for heating, cooling or releasing. They investigated the impact of some parameters such as partial load operation of the engine, hot water tank set point temperature, chilled

water temperature, cooling water temperature, etc. on the cycle characteristics. The present research is concerned about designing a hybridCCHP for the five different climates which presented previously in Ref. [20]. According to the previous researches presented in [21] the best prime mover for all of the five climates is internal combustion engine. Therefore the basic-CCHP cycle which was proposed in Ref. [22] is now combined with a solar collector. It means that natural gas and solar heat are the two main heating sources of the hybridCCHP system, while it makes use of the recovered heat from the engine exhaust, water jacketing and lube oil cooling as well. Since simulation models of the basic-CCHP components are the same as Ref. [22]; they are not repeated here to save space.

M. Ebrahimi, A. Keshavarz / Energy and Buildings 108 (2015) 10–22

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Fig. 2. Illustration of maximum rectangle method (MRM).

2. The hybrid-CCHP cycle description The schematic of the hybrid-CCHP system and the conventional separate production (CSP) are depicted in Fig. 1. An internal combustion engine is used to produce electricity in the hybrid-CCHP. As it can be seen a portion of water is heated through the solar system and the rest of it flows through the heat recovery exchangers to be heated for production of cool, heat or domestic hot water (DHW). Then they mix together and enter the auxiliary boiler, if needed the boiler starts heating water to reach an appropriate energy level according to the building demands, otherwise it would be bypassed to the cooling or heating systems. The output of auxiliary boiler can enter fan coil unit (FCU) for heating purpose, or absorption chiller to produce chilled water. The chilled water is sent to the FCU for cooling purpose. The DHW is extracted from the pipe just after the heat recovery exchangers, and the make-up water is also added to the main water line just before the auxiliary boiler to avoid overheating in the boiler.

B. The solar collector should be designed according to the recoverable heat from the engine and building demands. C. The auxiliary boiler size is determined according to the recoverable heat, solar heat and building demand. D. The absorption chiller size is determined according to the cooling demand of building. The steps are given below sequentially.

3.1. Sizing the engine by MRM MRM is used to size the prime mover [20,23]. This technique uses the hourly aggregated thermal load curve (ATD) and finds the maximum rectangle area under the hourly load curve as depicted in Fig. 2. The length and width of the rectangle represent the recommended full load operation time during a year and size of the prime mover correspondingly. The ATD and area of the rectangle (AMRM ) are determined as below:

3. Simulation ATD = Hdem + The designing procedure of hybrid-CCHP system includes four steps as below: A. The engine size should be determined by using maximum rectangle method (MRM) according to the aggregated thermal demand (ATD) for every climate.

Cdem + Ddem COPabc

AMRM (kWh) = ATD (kW) × time of year (%) × 8760

(1)

(2)

To find out the AMRM,max and Enom , the AMRM should be plotted versus the ATD as illustrated in Fig. 2.

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M. Ebrahimi, A. Keshavarz / Energy and Buildings 108 (2015) 10–22

Fig. 5. Sun coordination with respect to the collector at point O on earth.

The axis which earth spins about is tilted 23.45◦ (Fig. 4). In order to find the collector heat index, the declination angle ı is calculated (Eq. (3)).



ı = 23.45 sin 360◦ ×

Fig. 3. Plate collector and its components [16].

284 + N 365



(4)

in which N is the day number starting from N = 1 for the January 1st ending with N = 365 for December 31st. The sun coordination is determined by solar azimuth angle azs in the horizontal plane (angle HOS), and solar altitude  (angle HOQ in Fig. 5). Solar angular hour AH,  and azs are also calculated as below: AH = (Number of hours from solar noon) × 15◦





= 12 − time in hour × 15◦

sin  = cos(LAT ) · cos(ı) · cos(AH) + sin(LAT ) · sin(ı)

(6)

cos(ı) · sin(AH) sin azs = cos 

(7)

cos azs =

sin . sin(LAT ) − sin(ı) cos  · cos(LAT )

(8)

The incident angle  between the sun array (OQ) and the perpendicular axis to the collector (OP ) can be calculated based on ˙, the tilting angle of the collector (QOP ) and , the collector-sun azimuth angle:

Fig. 4. Representation of the declination angle.

cos  = cos  · cos  · sin ˙ − sin  · cos ˙

(9)

The  depends on the collector orientation, azs , and the collector azimuth angle, as below:

3.2. Simulation of the solar collector The collector considered for this research is a plate collector with two options of single or double glazing which should be chosen. Fig. 3 shows the plate collector and its components. The solar heat received by the collector is calculated according to the following equation: Qsolar = qu · Aco

(5)



east of south =

3.2.1. Collector heat index Collector heat index is the maximum average heat which the collector absorbs during a year in the optimum orientation.

morning

azs +

afternoon

azs +

morning

azs −

afternoon

 west of south =

(3)

In the above equation qu is the solar heat gain in watts per square meter of the collector area and should be calculated for each climate. In addition Aco is the collector size in m2 ; this parameter is calculated according to different strategies regarding the building demands.

azs −

(10)

(11)

The time of sunrise and sunset, and day length (DL) are required for solar heat calculations: DL =

2 arccos(− tan(LAT) · tan(ı)) 15

sunrise = 12 − 0.5DL sunset = sunrise + DL

(12) (13)

The direct solar radiation on the earth surface in a cloudless and clean sky is calculated by the following equation: RIDN = Ae−G/ sin



(14)

M. Ebrahimi, A. Keshavarz / Energy and Buildings 108 (2015) 10–22

in which A and G are apparent extraterrestrial irradiation and atmospheric extinction coefficient and are functions of date, and take into account the seasonal variation of the earth-sun distance and the air’s water vapor content. The magnitudes of A and G are curve fitted according to data presented in Ref. [16] as follow: 2

2

A = a1 · e−(N−b1 )/c1 + a2 · e−(N−b2 )/c2 ; a1 = 1187; b1 = 371.9; c1 = 225.9;

(15)

15

The data from Ref. [16] are curve fitted and interpolated to calculate , ˛ and UL as below:

=

⎧ 4 p  + p2  3 + p3  2 + p4  + p5 , single glazing ⎪ ⎨ 1 ⎪ ⎩

p6  6 + p7  5 + p8  4 + p9  3

+p10

2

double glazing

+ p11  + p12 ,

p1 = −5.084 × 10−8 ; p2 = 5.098 × 10−6 ; p3 = −17.57 × 10−5 ; p4 = 19.28 × 10−4 ;

a2 = 1144; b2 = −6.401; c2 = 206.2;

(23)

p5 = 86.83 × 10−2 ; p6 = 5.764e × 10−11 ; 2

2

G = a6 .e−((N−b6 )/c6 ) + a7 .e−((N−b7 )/c7 ) + a3 .e−((N−b3 )/c3 )

p7 = −1.388e × 10−8 ; p8 = 1.2e × 10−6 ;

2

a6 = 0.007325; b6 = 235; c6 = 22.82; a7 = 0.07095;

p9 = −4.696 × 10−5 ; p10 = 79.92 × 10−5 ;

b7 = 184.90; c7 = 99.03; a3 = 0.1409; b3 = 783.3; c3 = 3624;

p11 = −46.22 × 10−4 ; p12 = 77.04 × 10−2 ;

(16) ˛ = q1  8 + q2  7 + q3  6 + q4  5 + q5  4 + q6  3 + q7  2 + q8  + q9 The total solar irradiation RIt of a collector for any direction and tilting angle ˙ with an incidence angle of  is measured as follow: RIt = RIDN · cos  + RId + RIre

(17)

in which RIDN cos is the direct irradiation component, RId is the diffusion coming from sky and RIre is the reflected short wave irradiation from the foreground that possibly reaches the collector. To estimate the diffuse component, the dimensionless parameter K is defined that depends on dust and moisture content of atmosphere and changes through a year. It is defined by the following equation: K=

RIdH RIDN

(18)

in which RIdH is the diffuse component on a horizontal surface in a cloudless day. The following equation is used to estimate the diffuse irradiation on a collector with tilting angle of ˙: RId

(19)

in which K is curve fitted by using the data presented in Ref. [16], as below: 2

2

a4 = 0.08041; b4 = 187.4; c4 = 85.71;

(20)

a5 = 0.05888; b5 = 179.3; c5 = 589.6; Reflected component can be calculated as follow: RIre = RItH · g · Fsg , Fsg =

1 − cos ˙ 2

(21)

in which g is the reflectance coefficient and RItH is the total radiation on a horizontal surface. Bituminous surfaces reflect less than 10% of the total solar irradiation [16]. For simplicity in this investigation it is assumed RIre = (RIDN cos  + RId )/9. Finally the heat gained by the collector is calculated as below: qu = RIt (˛) − UL (Tp − Tamb (N, HR))

q3 = 1.416 × 10−10 ; q4 = −2.479 × 10−8 ; q5 = 1.575 × 10−6 ; q6 = −4.776 × 10−5 ; q7 = 65.62 × 10−5 ; q8 = −31.26 × 10−4 ; q9 = 0.96; (24)

U32 = 0.03083Tp + 5.517, U−12 = 0.025Tp + 5.5 for single glazing

(22)

To calculate the solar heat at every hour, the ambient temperature should be given in every hour (HR) of each day (N).

(25)

U32 = 0.01733Tp + 3, U−12 = 0.01556Tp + 2.678, for double glazing

UL = U−12 +

1 + cos ˙ = K · RIDN · Fss , Fss = 2

K = a4 · e−((N−b4 )/c4 ) + a5 · e−((N−b5 )/c5 )

q1 = −6.2 × 10−15 ; q2 = 4.873 × 10−13 ;

(26)

(U32 − U−12 )(Tamb (N, HR) + 12) 44

(27)

In order to find the optimum collector direction in which the maximum average annual solar heat is gained, the following procedure is followed. 1) After calculation of qu at every hour of daytime during a year, the yearly average value of qu for every pair of (˙, ) should be calculated (q¯ u,yearly ). 2) The angles (˙, ) in which q¯ u,yearly is maximum would be determined as optimum angles (˙ opt , opt ). 3) The maximum of q¯ u,yearly is the collector heat index and is shown by qs,opt = q¯ u,yearly,max , hence:

 qs,opt = max

365 N=1

sunset

q | sunrise u (˙, ) 365 DL N=1



0 ≤ ˙,

≤ 90◦

(28)

3.2.2. Collector size After calculation of the collector heat index, the size of collector should be determined, for this purpose the following four strategies are used. ATD strategy: the collector to be designed for providing the maximum aggregated thermal demand, ATDmax , therefore: Aco =

(ATDmax − Qrec,min ) for ATDmax ≥ Qrec,min qs,opt

(29)

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M. Ebrahimi, A. Keshavarz / Energy and Buildings 108 (2015) 10–22

H strategy: the collectors to be designed for satisfying the maximum thermal demand, Hdem,max , therefore:

Therefore, the auxiliary boiler size would be as below:

B = max max Aco

(Hdem,max − Qrec,min ) = for Hdem,max ≥ Qrec,min qs,opt

(32)

When the DHW system is integrated into the CCHP system (intgDHW) the first three strategies are applicable, but when the DHW is separated from the CCHP system (sprt-DHW) the last three strategies are applicable. Choosing the best strategy for collector sizing depends on the thermodynamical, environmental and economical evaluations. In this study the DHW is integrated into the CCHP system.

3.3. Auxiliary boiler size In order to calculate the size of auxiliary boiler, it must be known that, how much energy should be added to the solar energy and recovered energy to meet the building demands. This extra heat is produced by the auxiliary boiler. Hence:

 Cdem =



 Hdem =

0

if Cdem ≤ COPabc Qrs

Hdem − Qrs

if Hdem > Qrs

0

if Hdem ≤ Qrs

Qrec =

In the present paper, a four-floor eight-unit hypothetical residential building with total living area of 1200 m2 is considered. The specifications of the building are as follow: The average ceiling height and building weight are 2.7 m and 468.7 kg/m2 . The walls are medium weight with the overall U-value of 1.53 W/(m2 ·K). The overall U-values of floors above the unconditioned and conditioned spaces are 0.568 W/(m2 ·K) and 2.839 W/(m2 ·K). Each floor has fourteen double glazed windows, 6 mm argon gap type and each one has 2 × 2 m area. Total occupants are 32 people. The lighting is free hanging fixture type with the wattage of 20 W/m2 and the ballast multiplier of 1.25. The main electricity consumers and the corresponding power consumptions are as follow. The lighting index is 43 W/m2 , a TVLCD (160 W), a washing machine (2500 W), a refrigerator (130 W), a computer (250 W), iron (1000 W), and vacuum cleaner (1000 W). The demand factor of 0.76 is considered for the consumers. In addition the power consumption of water pump and chiller’s solution pump (sp) and refrigerant pump (rp) are also calculated according to the cooling and heating loads as below. ˙ rp = 0.007Cdem,max (kW), ˙ sp + W W ˙ water pump = 0.005 max(Cdem,max , Hdem,max ) W

(36)

The nominated cities of the five climates are mentioned in Table 1. The daily weather information including the maximum and minimum of dry bulb temperature (Tdb ) and relative humidity (RH) of the last five years is gathered from the Iran Metrological Organization for each city and used for calculation of the cooling and heating loads of the building. (33)

Qrs = Qrec + Qsolar



(35)

4. Case study

Ddem,max qs,opt

if Cdem > COPabc Qrs

The absorption chiller size equals the maximum cooling demand during a year. Hence:

(31)

D strategy: the collector to be designed for providing the Ddem,max , therefore:

Cdem − COPabc Qrs

(34)

COPabc

Cnom = max(Cdem )

(Cdem,max − COPabc · Qrec,min ) (COPabc · qs,opt )





3.4. Absorption chiller size

for Cdem,max ≥ COPabc · Qrec,min

Aco =

 Cdem

(30)

C strategy: the collector to be designed to fulfill the maximum cooling demand, Cdem,max , therefore: Aco =

 Hdem ,

5. Results

1.368EPM + 14.57, 30 ≤ E (kW) ≤ 500

5.1. Load calculations

1.854EPM , 0 ≤ E (kW) < 30 The hygrometric data such as the daily maximum and minimum of Tdb and RH which discussed previously in [20] is also used in this study. The building described in the case study is simulated in the HAP4.2 to calculate the cooling and heating loads. The heating, cooling, DHW and electricity consumption are shown in Figs. 6–10 for the five climates. These results show different patterns for the cooling and heating loads during a year for each climate. For example, Chabahar needs cooling throughout the year, while Ahwaz is

Qsolar = qs,opt · Aco

 Qrec =

1.368EPM + 14.57, 30 ≤ E(kW ) ≤ 500 1.854EPM , 0 ≤ E(kW ) < 30

Qsolar = qs,opt .Aco Table 1 Climate classification. Climates

Summer

Winter

City

Latitude (deg)

Longitude (deg)

TDC TSHT THT TDEC THC

Tropical and dry Tropical and semi-humid Tropical and humid Temperate and dry Temperate and humid

Cold Temperate Tropical Extremely cold Cold

Kerman Ahwaz Chabahar Kamyaran Bandar Anzali

30.28 31.33 25.28 34.80 37.46

57.08 48.66 60.64 46.93 49.46

H, C, D, E (kW)

M. Ebrahimi, A. Keshavarz / Energy and Buildings 108 (2015) 10–22

17

Electricity Cooling Heang DHW

100 80 60 40 20 0 0

10

20

30

40

50

60

Time of year (%)

70

80

90

100

H, C, D, E (kW)

Fig. 6. building demands during a year for Kerman.

4000 3550 3000 2550 2000 1550 1000 5 50 0

C Cooling H Heang D DHW EElectricity

0

10

20

30

40

50 60 Time of year(%)

70

80

90

100

80

90

100

80

90

100

80

90

100

Fig. 7. Building demands during a year for Ahwaz.

H, C, D,E (kW)

250

Cooling Heang DHW Electricity

200 150 100 50 0 0

10

20

30

40

50

60

70

Time of year (%) Fig. 8. Building demands during a year for Chabahar.

H, C, D, E (kW)

200

Cooling Heang DHW Electricity

150 100 50 0 0

10

20

30

40

50

60

70

me of year (%) Fig. 9. Building demands during a year for Bandar Anzali.

H, C, D, E (kW)

200

Cooling Heang DHW Electricity

150 100 50 0 0

10

20

30

40

50

60

70

Time of year(%) Fig. 10. Building demands during a year for Kamyaran.

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the hottest climate and cooling peak load occurs in this climate but cooling is not necessary in all seasons. Kamyaran is the coldest climate, and heating peak load occurs in this city. By comparing the yearly cumulative cooling load of the climates it is determined that Chabahar > Ahwaz > Bandar-Anzali > Kamyaran > Kerman. Also according to the yearly cumulative heating load of the climates it is revealed that Kamyaran > Kerman > Bandar Anzali > Ahwaz > Chabahar. In the calculations of the solar water heater collector, knowing the hourly temperature is necessary. The hygrometric data reported in [20] are curve fitted for each climate. The equations for the maximum and minimum of Tdb for the five climates are given in Eqs. (37)–(41). In these equations N is the day number stating from N = 1 for January 1st to N = 365 at the end of year. In order to calculate the hourly temperature in each day the Erbs’s model is utilized (Eq. (42)). This equation calculates the hourly temperature during each day according to the maximum and minimum of Tdb in the corresponding day.

Chabahar Tdb,min (N) = p1 N 5 + p2 N 4 + p3 N 3 + p4 N 2 + p5 N + p6 ; Tdb,max (N) = q1 N 5 + q2 N 4 + q3 N 3 + q4 N 2 + q5 N + q6 ; p1 = −2.741 × 10−11 ; p2 = 3.242 × 10−8 ; p3 = −1.346 × 10−5 ; p4 = 19.02 × 10−4 ; p5 = 62.08 × 10−4 ; p6 = 16.4; q1 = −7.308 × 10−11 ; q2 = 6.548 × 10−8 ; q3 = −2.086 × 10−5 ; q4 = 24.96 × 10−4 ; q5 = −28.2 × 10−3 ; q6 = 24.14; (39)

Kamyaran Tdb,min (N) = p1 N 7 + p2 N 6 + p3 N 5 + p4 N 4 + p5 N 3 + p6 N 2 + p7 N + p8 ;

Kerman

Tdb,max (N)

Tdb,min (N) = q1 N 6 + q2 N 5 + q3 N 4 + q4 N 3 + q5 N 2 + q6 N + q7 ;

= q1 N 7 + q2 N 6 + q3 N 5 + q4 N 4 + q5 N 3 + q6 N 2 + q7 N + q8 ;

Tdb,max (N) = p1 N 6 + p2 N 5 + p3 N 4 + p4 N 3 + p5 N 2 + p6 N + p7 ;

p1 = −8.94 × 10−15 ; p2 = 9.869 × 10−12 ;

q1 = −7.35 × 10−13 ; q2 = 8.156 × 10−10 ;

p3 = −4.008 × 10−9 ; p4 = 7.118 × 10−7 ; p5 = −4.811 × 10−5 ;

q3 = −3.241 × 10−7 ; q4 = 5.464 × 10−5 ;

p6 = −38.42 × 10−5 ; p7 = 0.2643; p8 = −8.653;

q5 = −41.21 × 10−4 ; q6 = 0.2764; q7 = −5.539;

q1 = 2.13 × 10−15 ; q2 = −3.826 × 10−12 ;

p1 = −5.879 × 10−13 ; p2 = 6.716 × 10−10 ;

q3 = 2.757 × 10−9 ; q4 = −9.812 × 10−7 ;

p3 = −2.776 × 10−7 ; p4 = 4.931 × 10−5 ;

q5 = 17.53 × 10−5 ; q6 = −15.19 × 10−3 ;

p5 = −41.1 × 10−4 ;

q7 = 0.7505; q8 = −2.802;

p6 = 32.24 × 10−2 ; p7 = 8.655;

(40)

(37)

Bandar e Anzali Tdb,min (N) = p1 N 6 + p2 N 5 + p3 N 4 + p4 N 3 + p5 N 2 + p6 N + p7 ;

Ahwaz Tdb,min (N) = p1 N 5 + p2 N 4 + p3 N 3 + p4 N 2 + p5 N + p6 ; Tdb max (N) = q1

N5

+ q2

N4

+ q3

N3

+ q4

N2

Tdb max (N) = q1 N 6 + q2 N 5 + q3 N 4 + q4 N 3 + q5 N 2 + q6 N + q7 ;

+ q5 N + q6 ;

p1 = −6.484 × 10−13 ; p2 = 7.342 × 10−10 ;

p1 = 4.826 × 10−11 ; p2 = −2.193 × 10−8 ; (38)

p3 = −2.807 × 10−6 ; p4 = 15.52 × 10−4 ;

q2 = −3.57 × 10

; q3 = 2.028 × 10

−6

−4

p5 = −30.45 × 10

p5 = 20.61 × 10−3 ; p6 = 6.882; q1 = 6.074 × 10−11 ; −8

p3 = −2.984 × 10−7 ; p4 = 4.996 × 10−5 ;

q1 = −9.933 × 10

;

; q2 = 1.088 × 10−9 ;

q3 = −4.321 × 10−7 ; q4 = 7.208 × 10−5 ;

q4 = 73.73 × 10−5 ; q5 = 0.1193; q6 = 15.6;

q5 = −44.73 × 10−4 ; q6 = 0.1569; q7 = .419;

600

AHWAZ BANDAR ANZALI CHABAHAR KAMYARAN Kerman

500

ATD(kW)

; p6 = 0.137; p7 = 3.112;

−13

400 300 200 100 0 0

10

20

30

40

50

60

70

80

Time of year (%) Fig. 11. Aggregated thermal demand during a year for the 5 climates.

90

100

(41)

AMRM(kWh)

M. Ebrahimi, A. Keshavarz / Energy and Buildings 108 (2015) 10–22

450,000

AHWAZ

400,000

BANDAR ANZALI

350,000

CHABAHAR

300,000

KAMYARAN

250,000

kerman

19

200,000 150,000 100,000 50,000 0 0

20

40

60

80

100

Time of year (%) Fig. 12. AMRM versus time of year for calculation of AMRM,max and Enom,MRM .

Enom(kW)

200

170

168

150 100

66

56

50

26

0 Kerman

Ahwaz

Bandar Anzali

Chabahar

Kamyaran

Fig. 13. Engine size recommended by the MRM for the 5 climates.

Tamb (N, HR) = Tavg + Tdiff (0.4632 cos( − 3.805) + 0.0984 cos(2 − 0.360) +0.0168 cos(3 − 0.822) + 0.0138 cos(4 − 3.513)  = Tdiff

2(HR − 1) , Tavg = 0.5(Tdb,max (N) + Tdb,min (N)), 24 = Tdb,max (N) − Tdb,min (N) (42)

depends on the cooling load of the building. Therefore the absorption chiller size is 105 kW, 361 kW, 159 kW, 236 kW and 145 kW for the above cities in that order. As a result, it can be concluded that, the basic-CCHP components size is significantly larger for the cities with higher cumulative cooling load and lower cumulative heating load. The basic-CCHP components size for the cities such as Kerman, Kamyaran and Bandar Anzali which have moderate cumulative cooling and heating loads is significantly smaller than Ahwaz and Chabahar. These larger components sizes mean higher initial cost which the residential consumers may not be able to come up with the money for. Therefore it is necessary for the government to pay subsides or proper loans for the climates such as cities of Ahwaz and Chabahar. In the next two steps we are supposed to combine the basic CCHP system with the solar water heater collector. To make use of the solar energy more efficiently, it must be placed in a particular direction to receive the maximum yearly solar energy. This is done in the next step. 5.3. Finding the optimum specifications of collector In order to find the optimum direction of the solar collector and glazing type, the following two steps should be taken:

5.2. Designing the basic-CCHP components size As mentioned previously, the MRM is utilized to size the internal combustion engine, which is considered as the prime mover of the CCHP system [21]. For this purpose the aggregated thermal demand, ATD is calculated, sorted and then plotted against the time of year for the five climates (Fig. 11). In the next step, in order to find the maximum rectangle area, the area of the rectangles calculated and plotted with respect to the time of year in Fig. 12. According to Fig. 12 the engine size for the specified building in the five climates of Kerman, Ahwaz, Bandar Anzali, Chabahar and Kamyaran is 66 kW, 127 kW, 26 kW, 168 kW and 56 kW (Fig. 13). The bigger the engines size the more the initial cost. Also bigger cooling load means bigger absorption chiller. Therefore the initial investment cost for the Ahwaz and Chabahar is considerably higher than other climates. According to the engine size proposed by the MRM, yearly FESR for the basic-CCHP with respect to the conventional separate production described in [22] is 28%, 28%, 28%, 32% and 31% for Kerman, Ahwaz, Bandar Anzali, Chabahar and Kamyaran correspondingly. It is assumed that the engine is operating in full load, unless it is mentioned. The auxiliary boiler size depends on the engine size, cooling and heating demands. According to the calculations, the auxiliary boiler size for the basic-CCHP system in Kerman, Ahwaz, Bandar Anzali, Chabahar and Kamyaran is 32 kW, 229 kW, 125 kW, 65 kW and 81 kW. The absorption chiller size

A. The yearly average of the solar heat gained (q¯ u,yearly ) by the collector should be calculated according to the procedure explained for Eq. (28). In this research we are supposed to determine the angles ˙ opt , and opt for the collector when it is facing southeast or southwest. B. Repeat all of the calculations in the first step for single and double glazing collectors. Number of glazing (single or double) is investigated to choose the best type and orientation for the five climates. Figs. 14–18 are presented as samples to show the optimum angles of ˙, for a double glazing plate collector which is facing southwest in five climates. As it can be seen there are angles of ˙, which the q¯ u,yearly is maximized in. The simulation is done for all of the climates, single and double glazing collectors, different angles from west of south and east of south. The brief results are given in Table 2. According to this table, the double glazing collector when it faces southwest receives the maximum solar heat in particular angles of ˙ opt and opt for each climate. The best conditions for the collector in each climate can be found in Table 2. This table also gives the collector heat index, qs,opt for each climate. As it can be seen among the five climates, the maximum qs,opt is received in the city of Ahwaz with the magnitude of 327.03 W/m2 .

20

M. Ebrahimi, A. Keshavarz / Energy and Buildings 108 (2015) 10–22

0.35

ψ=20

0.2

ψ=30

0.15

ψ=40 ψ=50

0.1

ψ=60 ψ=70 ψ=80

0 0

10

20

30

40 50 Σ(deg)

60

70

80

90

ψ=90

Fig. 14. Yearly average of solar heat gained per square meter of double glazing collector facing west of south in Ahwaz.

0.3

ψ=0 ψ=10

0.25 Qsolar(kW/(m2.year)

ψ=20 0.2

ψ=30 ψ=40

0.15

ψ=50 ψ=60

0.1

ψ=70 0.05

ψ=80 ψ=90

0 0

10

20

30

40 50 Σ(deg)

60

70

80

90

Fig. 15. Yearly average of solar heat gained per square meter of double glazing collector facing west of south in Bandar Anzali.

0.35

ψ=0

0.3

ψ=10 ψ=20

0.25

ψ=30 0.2

ψ=40

0.15

ψ=50 ψ=60

0.1

ψ=70 0.05

ψ=80

0

ψ=90 0

10

20

30

40

50

60

70

80

90

Σ(deg) Fig. 16. yearly average of solar heat gained per square meter of double glazing collector facing west of south in Chabahar.

0.3 ψ=0 ψ=10 ψ=20 ψ=30 ψ=40 ψ=50 ψ=60 ψ=70 ψ=80 ψ=90

0.25 0.2 0.15 0.1 0.05 0 0

10

20

30

40 50 Σ(deg)

60

70

80

90

Fig. 17. Yearly average of solar heat gained per square meter of double glazing collector facing west of south in Kamyaran.

Qsolar(kW/(m2.year)

Qsolar(kW/(m2.year)

ψ=10 0.25

0.05

Q solar (kW/(m 2.year)

ψ=10

ψ=0

0.3

Qsolar(kW/(m2.year)

ψ=0

0.3 0.25

ψ=20

0.2

ψ=30

0.15

ψ=40 ψ=50

0.1

ψ=60

0.05

ψ=70 ψ=80

0 0

10

20

30

40 50 Σ(deg)

60

70

80

90

ψ=90

Fig. 18. Yearly average of solar heat gained per square meter of double glazing collector facing west of south in Kerman.

This happens in optimum collector azimuth and tilting angles of 53◦ and 44◦ . Among the climates the minimum of qs,opt happens in Bandar Anzali with the magnitude of 255.95 W/m2 . In this case the collector azimuth and tilting angles are 49◦ and 46◦ . After determining the optimum type and direction of the collector in each climate, the collector is combined with the basic-CCHP to build the hybrid-CCHP. 5.4. Designing the hybrid-CCHP components size According to the previous discussions the collector size depends on the engine size, and the collector designing strategy. MRM that is used for engine sizing only depends on the ATD of the building. Therefore, using a solar collector does not change the engine size. This is a disadvantage of the MRM, because it does not consider economical and environmental criteria. It also neglects the impact of addition of other components to the basic-CCHP. Combining a solar collector with the basic-CCHP changes the economical, environmental and thermodynamical criteria of the basic-CCHP system. The authors of this article are aware of this dependency and concern about it. The main purpose of this paper is to focus on the solar collector optimization and its dependency on the engine size and building demands. Therefore the technique which is used for sizing the engine is not the main concern in this article. Although the authors are supposed to use the multi-criteria sizing method published in Ref. [22] in order to size the engine of a hybrid-CCHP system in the near future. In this research the DHW is integrated with the hybrid-CCHP system. Therefore three collector sizing strategies of ATD, H and C can be used to design the collector area in each climate. According to the equations derived for these strategies, the collector area decreases with increasing the engine size. It means that for small engine sizes which have small amount of recoverable heat, the collector area is large. A sample of this relation for the city of Kerman is shown in Fig. 19. It shows that for a particular engine size the collector size designed based on the Hdem is the smallest among the three strategies. This is due to the small heating peak load with respect to ATD and C. In addition the biggest collector size is proposed by the ATD (ATDdem,max > Cdem,max > Hdem,max ). Decision-making about the best strategy depends on the thermodynamical, economical and environmental criteria. The authors are supposed to propose a technique based on the multi-criteria sizing method in the near future for comprehensive decision-making about the strategy selection for collector sizing in the CCHP systems. This technique is a combination of thermodynamical, economical, environmental and the weight of these criteria. Additionally, Fig. 19 shows that for every collector designing strategy there is an engine size that for the engine sizes bigger than that the collector size would become zero. It means that the recoverable heat from the engine can satisfy

M. Ebrahimi, A. Keshavarz / Energy and Buildings 108 (2015) 10–22

21

Table 2 Optimum direction, type, and collector heat index (W/m2 ) in five climates. Single glaze, southeast qs,opt Kerman Ahwaz Bandar Anzali Chabahar Kamyaran

82.72 128.05 62.87 114.33 78.77

Double glaze, southeast



opt

qs,opt

opt

0 0 0 0 0

26 27 33 23 28

196.30 227.91 176.22 225.20 189.62

0 0 0 0 0

29 29 35 25 32

48 51 45 53 49

qs,opt

opt

37 41 39 37 39



opt

282.85 327.03 255.95 325.34 275.99

opt

53 53 49 57 51

43 44 46 41 45

50

ATD-based design Hdem-based design Cdem-based design

400 200 0 0

50

100

150

200

250

300

350

400

450

FESR(%)

Aco (m2)

120.87 190.37 93.44 173.21 118.24

Double glaze, southwest



opt

60

600

Enom(kW)

50 40 30 20 10 0

40

ATD H C no-collector

30 20 10 0

Fig. 19. Collector size versus engine size for three strategies of ATD, H and C, in Kerman.

FESR (%)

qs,opt

opt

800

0

100

200 300 Enom(kW)

400

500

Fig. 22. Fuel energy saving ratio for partial load operation of engine in Ahwaz. ATD-based design Hdem-based design Cdem-based design

0

50

100

150

200

250

300

350

400

450

500

Enom (kW) Fig. 20. Fuel energy saving ratio of the hybrid-CCHP for the three strategies of ATD, H and C in Chabahar.

B (kW)

Single glaze, southwest



opt

100 80 60 40 20 0

ATD-based design Hdem-based design Cdem-based design

0

50

100

150

200

250

300

350

400

Enom(kW) Fig. 21. Boiler size of the hybrid-CCHP for the three strategies of ATD, H and C in Kerman.

the building ATD, heating or cooling demands during year. Fig. 20 shows the fuel energy saving ratio of hybrid-CCHP system for the three strategies in Chabahar. This criterion is defined as following: FESR =

FCSP − FCCHP × 100 FCSP

(43)

in which F represents the fuel consumption. Heating demand of Chabahar is zero, therefore the collector size for this strategy becomes zero and this case is completely similar to the basic-CCHP system. As it can be seen the FESR for this case is smaller with respect to the ATD and C strategies which the collector size is not zero. It means that using collector for small engine sizes

results in more FESR. The boiler size of the hybrid-CCHP system is shown in Fig. 21. The boiler size changes slightly, because during night time solar energy is zero and the boiler size must be designed to compensate the lack of cooling or heating at anytime. The Aco , FESR, boiler size and chiller size for the climates are reported in Table 3. As it can be seen the Aco proposed by ATD in all of the cases is very large. Increasing the engine size decreases the collector size and initial investment cost (because the solar collector price per kW is higher than internal combustion engines), and increases the income due to selling electricity. According to Table 3 using solar collector does not make a significant difference in the FESR. This is due to full load operation of the engine. When the engine operates in full load, it can sell extra electricity to the grid, but when the engine size increases it produces lots of recoverable heat which may satisfy the building demand in most of times. In such condition, the hybrid-CCHP loses recoverable or solar heat when the Qrs is larger than ATD. If the engine operates in partial load, the hybrid-CCHP system reaches its maximum of FESR when the engine size equals the maximum of electrical demand of the building (Fig. 22). Also due to partial load operation, less recoverable heat is produced; therefore most of the recoverable and solar heat is used to meet the building demands. As a result the FESR of the hybrid-CCHP by using the engine in partial load increases (it reaches about 50% for ATD and C strategies). Also if no collector is used, the FESR of the basic-CCHP in full load operation is higher when it operates partial load (28% versus 20%). Partial load operation decreases the economical benefits of the CCHP, because the income due to selling electricity is totally omitted. As a result, if only fuel saving is

Table 3 Hybrid-CCHP components size and FESR. Kerman

Aco (m2 ) FESR (%) Boiler size (kW) Enom,MRM (kW) Chiller size (kW)

Ahwaz

Bandar Anzali

Chabahar

Kamyaran

ATD

H

C

ATD

H

C

ATD

H

C

ATD

H

C

ATD

H

C

252 28 22

0 28 32 66 105

161 28 22

1133 30 223

0 28 229 127 361

1050 30 223

810 34 125

67 30 125 26 159

708 34 125

371 32 58

0 32 65 168 236

290 32 58

541 32 79

112 32 79 56 145

442 32 79

22

M. Ebrahimi, A. Keshavarz / Energy and Buildings 108 (2015) 10–22

important, the engine is recommended to operate in partial load, but if economical benefits is also important, to have an economical hybrid-CCHP it must operate in full load at least for a period of time during a year. Another parameter that has significant impact on the FESR and economical benefits of hybrid-CCHP is the engine size. Larger engine size results in more electricity production to sell, smaller auxiliary boiler and collector size. It means the extra money paid for the bigger engine size can be compensated by decreasing the boiler and collector size. In reality, it is very difficult and costly to program a hybrid-CCHP according to the building demands to switch between partial load and full load operation. Because the building demands is highly fluctuating and switching between full load and partial load, results in losing efficiency, increasing operation and maintenance costs and increasing the price of control and regulation system. Furthermore a system which is supposed to be operated in residential buildings must have a simple and efficient control and regulation system. According to the discussion above the authors believe the engine size must increase and operate in full load until some constraints for economical criteria such as net present value and payback period are satisfied. 6. Conclusion and outlook A hybrid-CCHP is designed for a residential building in five climates. Maximum rectangle method is used for sizing the engine. The solar collector orientation and type is optimized for the five climates. The optimum azimuth angle and tilting angle for each climate is determined. In addition, the maximum receivable yearly solar heat per square meter of collector is determined in each climate. Four collector designing strategies based on aggregated thermal deman, heating, cooling and domestic hot water loads are introduced. A hybrid-CCHP is designed with the optimum direction, type and size of the collector. The results showed that increasing the engine size decreases the collector size. Using smaller engine size in hybrid-CCHP results in more FESR. Full load operation of engine in the basic-CCHP results in more FESR than partial load operation. On the contrary, partial load operation of the engine of the hybrid-CCHP results in more FESR than full load operation. However due to simpler control and regulation system, lower operation and maintenance cost, higher income due to selling extra electricity it is recommended to use bigger engine (with respect to the electrical demand of building) in full load operation. Choosing the best strategy for designing collector is another challenge which the authors are working on recently.

References [1] D.W. Wu, R.Z. Wang, Combined cooling, heating and power: a review, Prog. Energy Combust. Sci. 32 (2006) 459–495. [2] H.I. Onovwiona, V.I. Ugursal, Residential cogeneration systems: review of the current technology, Renew. Sustain. Energy Rev. 10 (2006) 389–431. [3] P.A. Pilavachi, Mini- and micro-gas turbines for combined heat and power, Appl. Therm. Eng. 22 (2002) 2003–2014. [4] Y. Huangfu, J.Y. Wu, R.Z. Wang, X.Q. Kong, B.H. Wei, Evaluation and analysis of novel micro-scale combined cooling, heating and power (MCCHP) system, Energy Convers. Manage. 48 (2007) 1703–1709. [5] X. Hao, H. Yang, G. Zhang, Trigeneration: a new way for landfill gas utilization and its feasibility in Hong Kong, Energy Policy 36 (2008) 3662–3673. [6] S.M. Lai, C.W. Hui, Feasibility and flexibility for a trigeneration system, Energy 34 (2009) 1693–1704. [7] M. Ebrahimi, A. Keshavarz, A. Jamali, Energy and exergy analyses of a micro-steam CCHP cycle for a residential building, Energy Build. 45 (2012) 202–210. [8] A.C. Oliveira, C. Afonso, J. Matos, S. Riat, M. Nguyen, P. Doherty, A combined heat and power system for buildings driven by solar energy and gas, Appl. Therm. Eng. 22 (2002) 587–593. [9] W. Yagoub, P. Doherty, S.B. Riffat, Solar energy-gas driven micro-CHP system for an office building, Appl. Therm. Eng. 26 (2006) 1604–1610. [10] J. Wang, Y. Dai, L. Gao, S. Ma, A new combined cooling, heating and power system driven by solar energy, Renew. Energy 34 (2009) 2780–2788. [11] G. Fraisse, Y. Bai, A.N. Le Pierre‘S, T. Letz, Comparative study of various optimization criteria for SDHWS and a suggestion for a new global evaluation, Solar Energy 83 (2009) 232–245. [12] H. Luo, A.R. Wangb, Y. Dai, The effects of operation parameter on the performance of a solar-powered adsorption chiller, Appl. Energy 87 (2010) 3018–3022. [13] B. Parida, S. Iniyan, R. Goic, A review of solar photovoltaic technologies, Renew. Sustain. Energy Rev. 15 (2011) 1625–1636. [14] H.Z. Hassan, A.A. Mohamad, R. Bennacer, Simulation of an adsorption solar cooling system, Energy 36 (2011) 530–537. [15] J. Wang, P. Zhao, X. Niu, Y. Dai, Parametric analysis of a new combined cooling, heating and power system with transcritical CO2 driven by solar energy, Appl. Energy 94 (2012) 58–64. [16] ASHRAE, chapter 33, solar energy use. [17] K. Habib, B. Choudhury, P.K. Chatterjee, B.B. Saha, Study on a solar heat driven dual-mode adsorption chiller, Energy 63 (2013) 133–141. [18] H. Lee, J. Bush, Y. Hwang, R. Radermacher, Modeling of micro-CHP (combined heat and power) unit and evaluation of system performance in building application in United States, Energy 58 (2013) 364–375. [19] J.Y. Wu, J.L. Wang, S. Li, R.Z. Wang, Experimental and simulative investigation of a micro-CCHP (microcombined cooling, heating and power) system with thermalmanagment controller, Energy 68 (2014) 444–453. [20] M. Ebrahimi, A. Keshavarz, Climate impact on the prime mover size and design of a CCHP system for the residential building, Energy Build. 54 (2012) 283–289. [21] M. Ebrahimi, A. Keshavarz, Prime mover selection for a residential micro-CCHP by using two multi-criteria decision-making methods, Energy Build. 55 (2012) 322–331. [22] M. Ebrahimi, A. Keshavarz, Sizing the prime mover of a residential micro-CCHP system by multi-criteria sizing method for different climates, Energy 54 (2013) 291–301. [23] S. MartiNez-Lera, J. Ballester, A novel method for the design of CHCP (combined heat, cooling and power) systems for buildings, Energy 35 (2010) 2972–2984.