A Comparative Assessment for the Potential Energy Production from PV Installation on Residential Buildings

sustainability

Article A Comparative Assessment for the Potential Energy Production from PV Installation on Residential Buildings

Sameh Monna 1 , Adel Juaidi 2 , Ramez Abdallah 2,* and Mohammed Itma 1

1 Architectural Engineering Department, An-Najah National University, P.O. Box 7, Nablus 007, Palestine; [email protected] (S.M.); [email protected] (M.I.) 2 Mechanical Engineering Department, An-Najah National University, P.O. Box 7, Nablus 007, Palestine; [email protected] * Correspondence: [email protected]

Received: 9 November 2020; Accepted: 4 December 2020; Published: 11 December 2020

Abstract: This paper targets the future energy sustainability and aims to estimate the potential energy production from installing photovoltaic (PV) systems on the rooftop of apartment’s residential buildings, which represent the largest building sector. Analysis of the residential building typologies was carried out to select the most used residential building types in terms of building roof area, number of floors, and the number of apartments on each floor. A computer simulation tool has been used to calculate the electricity production for each building type, for three different tilt angles to estimate the electricity production. Tilt angle, spacing between the arrays, the building shape, shading from PV arrays, and other roof elements were analyzed for optimum and maximum electricity production. The electricity production for each household has been compared to typical household electricity consumption and its future consumption in 2030. The results show that installing PV systems on residential buildings can speed the transition to renewable energy and energy sustainability. The electricity production for building types with 2–4 residential units can surplus their estimated future consumption. Building types with 4–8 residential units can produce their electricity consumption in 2030. Building types of 12–24 residential units can produce more than half of their 2030 future consumption.

Keywords: photovoltaic; energy demand; renewable energy; residential buildings; PV*SOL

1. Introduction Energy is considered one of the most important issues in both developed and developing countries [1]. Today, a large share of electricity is produced worldwide by renewable energy technologies [2]. Solar photovoltaic (PV) is one of the fastest-growing and most promising of these technologies and has many advantages [2]: (1) The solar PV is considered the most feasible renewable energy that can be successfully applied as distributed systems and building-integrated components in residential environments [3]. (2) The system performance can easily be modeled from the solar radiation depending on the orientation and tilting of solar PV [4]. (3) Solar PV technologies represent a safe, pollution-free, and environmentally friendly source of energy [5]. Several factors aﬀect the PV performance other than the orientation and tilting of solar PV such as wind speed, ambient temperature, relative humidity, and dust deposition [6–8]. Studies for the life cycle assessment of PV systems and other traditional and emerging technologies show that the PV systems environmental impact, with greenhouse gas emission of around 0.043 kg CO2 eq/kWh, is considered one of the most environmentally friendly systems when compared with

Sustainability 2020, 12, 10344; doi:10.3390/su122410344 www.mdpi.com/journal/sustainability Sustainability 2020, 12, 10344 2 of 17 traditional energy sources, and with newly available technologies such as hybrid solar plants, which combine solar power with another source of energy [9–11]. For example, even a solar hybrid gas turbine plant produces more emissions, 0.236 kg CO2 eq/kWh, than PV power plant, mainly because of the fuel used [12]. Globally, the growth of installed photovoltaic (PV) capacity reflects a strong commitment by scientists, researchers, industry, and governments to decarbonizing the economy for sustainable development [13]. For example, de-carbonizing of the building stocks by 2050 is one of Europe’s most important long-term targets that accounts for approximately 36% of the European Union’s CO2 emissions [13]. Photovoltaic technology plays an important role in the transition of buildings to becoming low-carbon ones [14]. The typology of urban areas has a profound impact on sunlight access and building energy efficiency and consumption levels [15–18]. Buildings in the European Union are now being designed and built to stricter building codes and standards to reduce their energy consumption and greenhouse gas emissions [19]. In 2019, Gaglia et al. mentioned that the residential buildings contribute to the higher percentage of energy usage in the building sector [20]. Residential buildings can use grid connected PV system, in this regard Sharma, Arvind, et al. (2020) introduced minimizing the energy cost of sustainable energy systems [21]. The promotion of rooftop PV systems can significantly reduce electricity bills [22]. In the Middle East, which is one of the regions with plenty of sunshine, PV potential is one of the highest in the world. In Palestine, solar energy is promising due to the high solar irradiation potential, and sunshine availability, which is about 3000 h per year [23,24]. On the other hand, Palestine imports almost all of its electricity needs [25]. In 2016, the energy supply in Palestine was (471Ktoe) were 91% of this supply was imported, and 9% were from local renewable and non-renewable energy sources [26]. Building energy consumption was about 60% of this imported energy, which is the highest consumption segment of final energy among the other Middle East and North African countries, and the share of electricity in Palestinian household expenditures is around 9% due to the very high price of electricity [27]. Additionally, Palestine suffers from electricity shortage and continuously blackout in the cold and hot seasons due to the very high demand for heating and cooling, the limited amount of imported electricity, and the weak infrastructure of the public electricity distribution companies. Electricity has the largest part of the Palestinian energy mix, at around 34%. In 2016, the average annual electricity consumption per household was 3672 KWh, and the monthly average was 306 kWh. As the main fuel used for heating, 39.4% of Palestinian households used electricity [26]. For cooling, Palestinian households used almost only electric energy to operate fans and air conditioning units [26]. Due to the growing urbanization and the rapid growth in population, the demand forecast for electricity consumption for a household in 2030 will reach 6536 kWh per year, with an average monthly consumption of 545 kWh [27]. Due to the increased urbanization, expensive energy, and the lack of natural resources in Palestine, there is an urgent need to find mitigation strategies for future electricity consumption in residential buildings [28]. Most households in Palestine have access to electricity: 93% for rural and 99% for urban households, which make grid-connected PV systems a feasible solution for residential buildings. In West Bank the residential buildings have almost 24 h access to power; however, in Gaza strip this access is limited to around 16 h [26]. Additionally, the supply is not always sufficient to cover the needs of the West Bank and Gaza Strip, which are growing rapidly (5–7%/year) especially for the Gaza Strip. The percentage of household units having solar water heating has decreased from 75% in 2001 to 57% in 2015. It is worth mentioning that one-third of these solar heating systems are out of order, which creates a high demand for electricity for heating especially in the cold season [29]. In Palestine, the government, private sectors, and NGOs are now supporting the investment in renewable energy by installing Solar PV on public buildings especially school buildings and investing in solar energy fields [30]. Other buildings sectors like residential buildings (the largest building sector) are still not getting the proper attention, despite the very high electricity consumption of this sector. This study will focus on selected typologies of existing and new residential buildings to integrate Sustainability 2020, 12, 10344 3 of 17

Sustainability 2020, 12, x FOR PEER REVIEW 3 of 18 PV systems, which can lead to a reduction in the final network’s electricity demand and provide an provide an investment in the renewable energy sector for the wide range of private residential investment in the renewable energy sector for the wide range of private residential buildings. buildings. The apartment buildings in Palestine represent the majority of residential households, 61.5%, The apartment buildings in Palestine represent the majority of residential households, 61.5%, 53% in the West Bank, and 65.6% in Gaza Strip as can be seen in Figure1. The typical apartments of 53% in the West Bank, and 65.6% in Gaza Strip as can be seen in Figure 1. The typical apartments of three and four bedrooms represent the majority of household units in Palestine (35% and 30% of the three and four bedrooms represent the majority of household units in Palestine (35% and 30% of the apartments), followed by two bedrooms (16%), and more than five bedrooms (15%) [26]. In Palestine apartments), followed by two bedrooms (16%), and more than five bedrooms (15%) [26]. In Palestine 85% of household’s units are owned by the residents, which makes the investment in the PV systems 85% of household’s units are owned by the residents, which makes the investment in the PV systems in residential buildings directly affect the ownership of the building [26]. in residential buildings directly affect the ownership of the building [26].

Figure 1. PercentagePercentage of of apartment apartment buildin buildingsgs compared compared to to other forms of residential buildings in Palestine. Data Data derived derived from Palestinia Palestiniann Central Bureau of Statistics (2017).

Residential buildings are usually found found in in Palestinian Palestinian cities cities in in clusters clusters and and neighborhoods neighborhoods [31]. [31]. Those buildings contain multiple forms of separate or semi-connected semi-connected residential apartments that are combined by by a a staircase staircase [32]. [32]. Such Such buildings buildings belong belong to to international international prototypes prototypes and and can can be befound found in otherin other countries countries but but with with different different shapes shapes and and size sizes.s. The The design design of of the the building building often often follows the planning and organizational laws of the lands into Patterns A, B, and C. These laws are provided by the Ministry of Local Government to to determine th thee proportion of the building and the number of floorsfloors [33]. [33]. Such Such laws laws are are supposed supposed to to control control the density of the buildings according to the planning goals for each region. The The following is is a brief explanation of the most used patterns for residential buildings in Palestinian cities [[34]:34]: − BuildingBuilding type A: residential buildings for single families consisting of a maximum of two floors floors − intendedintended for for single-family single-family use. use. These These buildings buildings are are usually usually located on sorted land plots with an areaarea of 500 500–800–800 m 2,, and and the the construction construction percentage percentage is is 30% 30% of of the the land land area area so so that the average roofroof area in this pattern is 200 m2 includingincluding the the stair’s stair’s roof. roof. This This pattern pattern could could contain contain buildings buildings inin the the form form of of two two common common units with a staircase and the roof area reachesreaches 300300 mm22. − BuildingBuilding type B: residential buildings for multiple-familymultiple-family apartment buildings. Such buildings − consistconsist of 5 5–7–7 floors; floors; each floor floor includes two to four apartments [35]. [35]. These These buildings buildings are located 2 onon sorted land plots with an area of 800 800–1500–1500 m 2 andand a a construction construction rate rate of of 50% 50% of the land area 2 isis permitted. permitted. Thus, Thus, the the average average roof roof area area of this of this pattern pattern is from is from 300 to 300 600 to m 600 including m2 including the stair’s the roof.stair’s roof. − BuildingBuilding type type C: C: residential residential bu buildingsildings for for extended extended families. families. Those Those buildings buildings consist consist of of 4 4 floors. floors. − EachEach floor floor consists of one apartment or two. Th Thee average average area area of the sorted land lots is 400 400–600–600 2 mm2——andand the permitted areaarea ofof thethe building building is is around around 49%, 49%, which which led led to anto an average average built built area area 180 2 180up toup 250 to 250 m2, m including, including the the stair’s stair’s roof. roof. For all the mentioned types of buildings, there are some common architectural and structural characteristics: Sustainability 2020, 12, 10344 4 of 17

For all the mentioned types of buildings, there are some common architectural and structural characteristics:

- Most of these buildings tend in their design to regular forms of square or rectangular shapes. The floors are usually distributed as parking in the basement or ground, and residential apartments on the upper floors. - Each floor consists of one or four apartments, and the building contains one or more vertical access units (staircase) in addition to the elevator and skylights, which are often in B and C patterns [36]. - The roof is concrete slab, normally flat, and has a parapet of 80 cm height. - The staircase roof is used for water tanks and solar water heating units. - The residential buildings envelope is not thermally insulated. The glass used for the window is single/double glazing with an aluminum frame. The walls use the typical components of stone, concrete, hollow concrete block, and plaster.

Due to the difficult political conditions, the shortage of natural resources, the population density and the financial crisis in Palestine, the energy sector is dependent on nearby countries and highly vulnerable compared to other Middle Eastern countries. Moreover, Palestine depends on neighboring countries for 100% of its non-renewable energy imports and for 87% of its electricity imports. Solar Energy potential in Palestine can open new perspectives for energy sector in order to prompt practices for sustainable development. Although the problems for energy sector in Palestine are well known, evaluating the solar energy production from PV installation on residential buildings typologies in this climatic and economic contest has not been done before. This research will contribute to the evaluation studies needed for decision making and scientific communities in terms of new results, evaluating the parameters affecting energy production from installing PV on residential buildings and a proposed approach to achieve energy sustainability.

2. Materials and Methods A new developed approach is used which brings together a combination of energy consumption in residential buildings; surveying the most used residential typologies; and renewable energy production for diﬀerent scenarios using a computer simulation tool (PV*SOL).

2.1. Selecting Residential Building Types The targeted residential buildings have been selected based on the most used types and shapes in the Palestinian cities. The numbers of household units for each building type and the available roof areas for installing PV systems have been selected in reference to the most popular apartment types in the Palestinian cities. According to the local government building legislation in West Bank and Gaza Strip, the residential buildings have been categorized into three main categories: A (maximum two floors, with one or two apartments at each floor); B (four-seven floors, with two or four apartments at each floor); and C (maximum four floors, with one or two apartments at each floor) [32]. The common area of each type was collected based on the local law of land lots in the Palestinian Land Authority [37]. Three to four bedrooms apartment has been selected as it represents the majority of household units in the Palestinian cities [26]. One and three apartments per floor for type B were excluded because these types are not widely spread in the Palestinian cities; these types are not likely to have three bedrooms for each apartment, which is not common in the Palestinian cities. Table1 below provides a summary of the selected residential building types and related information to install PV systems on the rooftop of these buildings. The roof area available for PV installation has been calculated by subtracting the shaded area (calculated by the PV *SOL premium 2020) and the area used for water tanks from the total roof area. Sustainability 2020, 12, 10344 5 of 17

Sustainability 2020, 12, x FOR PEER REVIEW 5 of 18 Sustainability 2020, 12, x FOR PEER REVIEW 5 of 18 Table 1. The most common types of residential buildings in Palestinian cities, classiﬁed according to Table 1. The most commonthe organizational types of residential regions buildings of the in Palestinian Ministry ofcities, Local classified Government. according to the organizational regions of the Ministry of Local Government. Table 1. The most common types of residential buildings in Palestinian cities, classified according to the organizational regions of the Ministry of Local Government. ) ) 2 2 ) ) ) 2 ) 2 2 2 ) ) ) ) 2 ) 2 2 Floor 2 2 / ) ) ) 2 2 2 ) 2 Stairs Roof Apartment (m / Building Type Building Shape Installation (m Installation Number of FloorsNumber of Stairs Roof Stairs Roof Total Roof Area (m Building Orientation Area available for PV for PV available Area The shaded Area (m shaded The Building Type Building Type Building Shape Building Shape Installation (m Installation Installation (m Solar Water Heating (m Number of FloorsNumber of Number of Floors Roof Area/Apartment (m Roof Area/Apartment Number of Apartment/floor Apartment/floor of Number Total Roof Area (m Total Roof Area (m Building Orientation Area available for PV for PV available Area The shaded Area (m shaded The Building Orientation Area available for PV The shaded Area (m Area-Used for Water Tanks and and Tanks for Water Area-Used Solar Water Heating (m Solar Water Heating (m Roof Area/Apartment (m Roof Area/Apartment Roof Area Number of Apartment/floor Apartment/floor of Number Number of Apartment Area-Used for Water Tanks and and Tanks for Water Area-Used Area-Used for Water Tanks and

South-North 14 169 A1 200 2 1 200 17 East-West 12 171 South-NorthSouth-North 1414 169169 A1A1 200200 2 2 1 1 200 200 17 17 East-WestEast-West 1212 171171

South-North 21 262 Sustainability 2020, 12, x FORA2 PEER REVIEW 300 2 2 150 17 South-North 21 262 6 of 18 A2 300 2 2 150 17 East-West 24 259 Sustainability 2020, 12, x FOR PEER REVIEW East-WestSouth-North 2421 259262 6 of 18 A2 300 2 2 150 17 Sustainability 2020, 12, x FOR PEER REVIEW East-West 24 259 6 of 18 Sustainability 2020, 12, x FOR PEER REVIEW 6 of 18

5–7 30–21.5 South-North 25 253 B1 300 5–7 2 30–21.5 22 South-North 25 253 B1 300 (6) 2 (25) 22 East-West 30 248 (6)5–7 30(25)–21.5 South-NorthEast-West 3025 248253 B1 300 5–7 2 30–21.5 22 South-North 25 253 B1 300 (6) 5–7 2 (25) 30–21.5 22 South-NorthEast-West 2530 253248 B1 300 (6) 2 (25) 22 East-West 30 248 (6) (25) East-West 30 248

5–7 30–21.5 South-North 29 501 B2 600 5–7 4 30–21.5 70 South-North 29 501 B2 600 (6) 4 (25) 70 East-West 35 495 (6)5–7 5–7 30(25)–21.5 30–21.5 South-NorthSouth-NorthEast-West 293529 501495501 B2B2 600600 5–7 4 4 30–21.5 70 70 South-North 29 501 B2 600 (6) (6) 4 (25) (25) 70 East-WestEast-West 3535 495495 (6) (25) East-West 35 495

South-North 14 149 C1 180 4 1 45 17 South-North 14 149 C1 180 4 1 45 17 South-NorthEast-West 1412 149151 C1 180 4 1 45 17 South-NorthEast-West 1214 151149 C1 180 4 1 45 17 East-WestSouth-North 1214 151149 C1 180 4 1 45 17 East-West 12 151 East-West 12 151

South-NorthSouth-North 2121 212212 C2C2 250250 4 4 2 2 31.25 31.25 17 17 South-North 21 212 C2 250 4 2 31.25 17 East-WestEast-West 2424 209209 South-NorthEast-West 2421 209212 C2 250 4 2 31.25 17 South-North 21 212 C2 250 4 2 31.25 17 East-West 24 209 East-West 24 209

The study used the selected building types in four cities in Palestine, which represent the diﬀerent governorates in the West Bank (North, Central, and South) and Gaza Strip, as can be seen in Figure2. Nablus (Latitude 32◦130 N, Longitude 35◦160 E, Altitude of 560 m and annual global irradiation of 1979 2 kWh/m ) in the Northern part of the West Bank; Jerusalem (Latitude 31.7683◦ N, Longitude 35.2137◦ E, Sustainability 2020, 12, x FOR PEER REVIEW 7 of 18

The study used the selected building types in four cities in Palestine, which represent the Sustainabilitydifferent governorates2020, 12, 10344 in the West Bank (North, Central, and South) and Gaza Strip, as can be6 seen of 17 in Figure 2. Nablus (Latitude 32°13′ N, Longitude 35°16′ E, Altitude of 560 m and annual global irradiation of 1979 kWh/m2) in the Northern part of the West Bank; Jerusalem (Latitude 31.7683° N, 2 AltitudeLongitude of 75735.2137° m above E, Altitude sea level andof 757 annual m above global sea irradiation level and of 2035annual kWh global/m ) inirradiation the central of part 2035 of thekWh/m West2) Bank;in the Hebron central (Latitudepart of the 31.5326 West◦ Bank;N, Longitude Hebron 35.0998(Latitude◦ E, 31.5326° Altitude N, of Longitude 930 m above 35.0998° sea level E, 2 andAltitude annual of 930 global m above irradiation sea level of 2054 and kWhannual/m global) in the irradiation Southern partof 2054 of thekWh/m West2) Bank; in the Gaza Southern (Latitude part 31.5017of the West◦ N, LongitudeBank; Gaza 34.4668 (Latitude◦ E, 31.5017° Altitude N, of Longitud 45 m abovee 34.4668° sea level E, andAltitude annual of 45 global m above irradiation sea level of 2 1977and annual kWh/m global)[38]. irradiation of 1977 kWh/m2) [38].

Figure 2. TheThe map map shows shows the thedifferent diﬀerent parts parts of Palestine of Palestine (West (West Bank and Bank Gaza and Strip) Gaza and Strip) the andselected the selectedcities. cities.

2.2. Estimating Electricity Electricity Consumption Consumption The averageaverage monthly and yearlyyearly electricityelectricity consumptionconsumption for the selectedselected householdhousehold has beenbeen identiﬁedidentified usingusing surveys for the households done by the Palestinian Central Bureau Bureau of of Statistics Statistics [26]. [26]. ItIt hashas beenbeen donedone byby identifyingidentifying thethe numbernumber ofof appliancesappliances perper householdhousehold andand thenthen approximatingapproximating daily consumption consumption by by usage. usage. For For the theresidential residential building building sector, sector, the main the usages main usages of electricity of electricity are air- areconditioned, air-conditioned, heating, heating,water heating, water fridge, heating, and fridge, lighting. and The lighting. average Theannual average electricity annual consumption electricity consumptionper typical household per typical (three household bedrooms (three and bedrooms househ andold householdmembers of members 5.2) was of 3672 5.2) waskWh, 3672 and kWh, the andmonthly the monthlyaverage was average 306 kWh was 306(442 kWh kWh (442for the kWh central for the region, central 294 region, kWh for 294 the kWh south for region, the south 272 region,kWh for 272 the kWh north for theregion, north region,and 265 and kWh 265 kWhfor Gaza for Gaza strip). strip). The The future future demand demand for for electricity consumption for a typical household in 2030, whichwhich will reach 6536 kWh per year, withwith anan averageaverage monthly consumption ofof 545545 kWh,kWh, waswas identiﬁedidentified basedbased onon aa studystudy byby thethe WorldWorldBank Bank[ [27].27].

2.3. Solar PV Simulation 2.3. Solar PV Simulation To calculate the potential electricity production from installing PV systems on the roof of the To calculate the potential electricity production from installing PV systems on the roof of the selected building types and orientation a simulation was done by the software PV*SOL premium 2020 selected building types and orientation a simulation was done by the software PV*SOL premium (R8). PV*SOL is specially designed for simulation and analysis of solar PV by Valentine Software [39]. 2020 (R8). PV*SOL is specially designed for simulation and analysis of solar PV by Valentine Software The software is produced and improved in Germany with 3D visualization and detailed shading [39]. The software is produced and improved in Germany with 3D visualization and detailed shading analysis for the PV systems, which is considered one of the leading countries in the solar PV industry analysis for the PV systems, which is considered one of the leading countries in the solar PV industry and technology. PV*SOL provides solar radiation data for nearly all the cities in the world and supplies and technology. PV*SOL provides solar radiation data for nearly all the cities in the world and an up to date database and electrical characteristics for most commercial PV module devices. From the supplies an up to date database and electrical characteristics for most commercial PV module devices. severalFrom the commercial several commercial PV modules PV available modules in available Palestine today,in Palestine JAM72S10-410 today, JAM72S10-410/MR/MR (high power rating(high 410power W andrating high 410 e Wﬃ ciencyand high 20.43%) efficiency is used 20.43%) based is onused information based on information from several from companies several companies operating in the local market that this module is highly eﬃcient and provides higher energy production per given area. Sustainability 2020, 12, x FOR PEER REVIEW 8 of 18 operating in the local market that this module is highly efficient and provides higher energy production per given area. The simulations were made for Grid-connected PV Systems for different cities (Jerusalem, Hebron, Nablus, and Gaza city) and buildings for two orientations (South-North and East-West). In designing array modules two significant aspects have to be considered for maximizing the solar power production and minimizing the shading losses: the optimum tilt angle for the specific location

Sustainabilityand the distance2020, 12 between, 10344 the arrays. 7 of 17 Three tilt angles were chosen for the simulation: (1) 27°: Since the Optimum tilt angle for the most cities in Palestine is about 27° [40], which is in line with the result from the study by Jacobson et al. The[6], but simulations it required were a relatively made for Grid-connectedlong distance between PV Systems the arrays for di fftoerent minimize cities (Jerusalem,the shading Hebron, losses; Nablus,(2) 1°: since and it Gaza is required city) and less buildings distance for between two orientations the arrays (South-North to minimize andthe shading East-West). losses. In designing It is also arraypreferred modules to choose two significant the tilt angle aspects more have than to 15º be to considered minimize for the maximizing soiling effect the [41]. solar (3) power 7°: To production maximize andthe power minimizing production the shading from the losses: limited the area optimum of the tilt roof angle by increasing for the specific the number location of and the themodules distance as betweenmuch as possible. the arrays. For all cases, the array spacing has been calculated for PV systems orientated to the southThree by the tilt following angles were equations chosen for the simulation: (1) 27◦: Since the Optimum tilt angle for the most cities in Palestine is about 27◦ [40], which is in line with the result from the study by Jacobson et d1 = h/tan(SA) (1) al. [6], but it required a relatively long distance between the arrays to minimize the shading losses; (2) 1◦: since it is required less distancetan(SA) between = thetan( arraysγ)/cos( toα) minimize the shading losses. It is also(2) preferred to choose the tilt angle more than 15º to minimize the soiling effect [41]. (3) 7 : To maximize h = bsin(β) ◦ (3) the power production from the limited area of the roof by increasing the number of the modules as muchwhere asd1 possible. is the array For spacing, all cases, b the is the array height spacing of the has solar been panel, calculated SA is forthe PVShading systems Angle orientated between to the southsun and by the the array, following h is equationsthe height of the tilted solar panel, γ is the solar elevation angle, and α is the solar azimuth angle as it can be seen in Figured1 = h3./ tan(SA)Usually, the solar elevation and azimuth angle (1)at 10:00 am or 2:00 pm on the winter solstice (21 December) are utilized for estimating the array spacing tan(SA) = tan(γ)/cos(α) (2) [42]. These times have been chosen to make sure there is no self-shading between these two hours during the worst case for the solar PV array orientath = bsin(ed βto) the south on the winter solstice. The PV*SOL (3) premium 2020 used another method of solar elevation and azimuth angle at noon to calculate the where d is the array spacing, b is the height of the solar panel, SA is the Shading Angle between the array spacing.1 γ α sun andFor theexample, array, hγ is = the35° heightand α of= 0° the at tilted noon solar for Hebron panel, cityis the at solarthe winter elevation solstice angle, (21 and Dec.).is the solar azimuthSubstitute angle asin itEquation can be seen (2): intan Figure (SA) 3=. tan Usually, (35°)/cos the solar(0°) = elevation 0.70 and azimuth angle at 10:00 am or 2:00Then pm substitute on the winter in Equation solstice (21 (3): December) h = 2.015*sin are utilized(27°) = 0.916 for estimating m (β = 27°) the array spacing [42]. These times have been chosen to make sure there is no self-shading between these two hours during the Finally substitute in Equation (1): d1 = 0.916/0.70 = 1.3 m (Spacing = 1.3 m) worst case for the solar PV array orientated to the south on the winter solstice. The PV*SOL premium but if 10 am is utilized for estimating the array spacing where γ = 30.3° and α = 26° then d1 = 1.4 2020m (spacing used another = 1.4 m). method of solar elevation and azimuth angle at noon to calculate the array spacing.

Figure 3. Solar angles tilt angles and distance between arrays (derived from PV*SOL software). Figure 3. Solar angles tilt angles and distance between arrays (derived from PV*SOL software).

ForIn this example, manuscript,γ = 35 ◦theand spacingα = 0◦ atbetween noon for arrays Hebron was city changed at the winter in order solstice to give (21 the December). maximum powerSubstitute output in in each Equation array (2): system. tan (SA) For= example,tan (35◦) /forcos building (0◦) = 0.70 type A1 with North-South building orientationThen substitute at a tilt angle in Equation equal 27° (3): the h = spacing2.015*sin was (27 1.4◦) = m.0.916 Because, m (β =in27 this◦) case, if the spacing was 1.3m,Finally then the substitute number inof Equationmodules will (1): dbe1 =the0.916 same/0.70 and= the1.3 power m (Spacing produced= 1.3 will m) decrease due to the But if 10 am is utilized for estimating the array spacing where γ = 30.3◦ and α = 26◦ then d1 = 1.4 m (spacing = 1.4 m). In this manuscript, the spacing between arrays was changed in order to give the maximum power output in each array system. For example, for building type A1 with North-South building orientation at a tilt angle equal 27◦ the spacing was 1.4 m. Because, in this case, if the spacing was 1.3 m, then the number of modules will be the same and the power produced will decrease due to the increase of the self-shading eﬀect. Another example for Building type A2 with North-South orientation at tilt angle Sustainability 2020, 12, x FOR PEER REVIEW 9 of 19 Sustainability 2020, 12, 10344 8 of 17 increase of the self-shading effect. Another example for Building type A2 with North-South orientation at tilt angle 27° the spacing was 1.3 m. Because, in this case, if the spacing was 1.4 m, this 27◦ the spacing was 1.3 m. Because, in this case, if the spacing was 1.4 m, this would result in the loss wouldof an array result of in modules the loss andof an thus array reduce of modules the power and produced. thus reduce the power produced.

3. Results Results The resultsresults for for potential potential electricity electricity production production from from installing installing PV panels PV onpanels residential on residential buildings buildingsin Palestine in to Palestine reduce the to energyreduce demand the energy on the deman publicd on electricity the public network electricity have beennetwork summarized have been for summarizedthe selected building for the selected types and building orientations. types and orientations.

3.1. Residential Residential Building Building Type Type A For buildingbuilding orientation orientation South-North, South-North, the the annual annual electricity electricity production production from installingfrom installing PV systems PV systemson the rooftop on the ofrooftop building of building type A1 type (two A1 residential (two residential units) in units) four di inff erentfour different cities at threecities diatff threeerent differenttilt angles tilt are angles in the are ranges in the 34,144ranges kWh–36,18934,144 kWh–36,189 kWh for kWh the for system the system installed installed power power of 22.14 of 22.14 kW kWwith with a tilt a angletilt angle of 27of◦ 27°;; 34,144 34,144 kWh–35,896 kWh–35,896 kWh kWh for for the the same same installed installed power power withwith aa tilttilt angle of 1717°;◦; and 40,284 kWh–42,245 kWh kWh for for the system installed installed power power of of 27.06 27.06 kW kW with with a a tilt tilt angle angle of of 7°; 7◦; where these ranges vary depending on the selected cities. There There is is a slight difference difference between the selected cities in terms of electricity production due to differences differences of solar radiations, where Hebron has the highest productionproduction ofof 42,24542,245 kWh kWh at at tilt tilt angle angle 7 ◦7°,, while while Gaza Gaza city city has has the the lowest lowest production production of of40,284 40,284 kWh kWh at the at samethe same angle. angle. The annual The annual electricity electricity production production for each for household each household unit (the electricityunit (the electricityproduction production for the whole for the building whole then building divided then by divided the number by the of number household of household units) is in units) the ranges is in the21,123 ranges kWh–20,142 21,123 kWh–20,142 kWh for the kWh system for withthe system tilt angle with 7◦ ;tilt 18,095 angle kWh–17,231 7°; 18,095 kWh–17,231 kWh for the kWh system for with the systemtilt angle with 17◦ ,tilt and angle 17,984 17°, kWh–17,072 and 17,984 kWh kWh–17,072 for the system kWh withfor the tilt anglesystem 27 with◦, where tilt theseangle ranges27°, where vary thesedepends ranges on thevary selected depends cities on as the can selected be seen cities in Figure as can4. Ifbe we seen compare in Figure the electricity4. If we compare production the electricitywith future production consumption with in 2030future and consumption the consumption in 2030 of 2016and forthe eachconsumption household, of this 2016 production for each household,represents 2.19this toproduction 3.29 times therepresents 2030 electricity 2.19 to consumption3.29 times the and 2030 represents electricity 3.34 consumption to 6.33 times and the representselectricity consumption3.34 to 6.33 times in 2016. the electricity These ranges consum varyption depending in 2016. on These the tilt ranges angle andvary the depending selected city,on the as tiltcan angle be seen and in the Table selected2. city, as can be seen in Table 2.

(a) (b)

Figure 4. For South-North orientation: ( (aa)) the the annual annual electricity electricity production production for for each household for building type A1 and ( b) the annual electricity production forfor each householdhousehold forfor buildingbuilding typetype A2.A2.

For building type A2 (four residential units) the annual electricity production is higher than A1 due to thethe factfact thatthat the the roof roof is is larger. larger. However, However, the the annual annual electricity electricity production production for eachfor each household household unit unitis less is thanless A1,than because A1, because the share the of share the roof of the is less roof than is less the sharethan the in building share in type building A1. This type production A1. This productionfor each household for each unithousehold is in the unit ranges is in the 14,108 ranges kWh–14,695 14,108 kWh–14,695 kWh for the kWh system for the installed system powerinstalled of power39.36 kW of 39.36 with akW tilt with angle a oftilt 7 angle◦; 12,769 of 7°; kWh–13,388 12,769 kWh–13,388 kWh for thekWh system for the installed system powerinstalled of power 33.62 kW of 33.62with akW tilt with angle a oftilt 17 angle◦; and of 12,70217°; and kWh–13,314 12,702 kWh kWh–13,314 for thekWh same for the installed same installed power with power a tilt with angle a tilt of angle27◦; where of 27°; these where ranges these vary ranges depends vary ondepends the selected on the cities selected as can cities be seen as can in Figurebe seen4. in This Figure production 4. This productionrepresents 1.62 represents to 2.29 times1.62 to the 2.29 future times electricity the futu consumptionre electricity forconsumption households for in households 2030 and represents in 2030 and2.47 represents to 4.44 times 2.47 the to electricity 4.44 times consumption the electricity of 2016consumption depending of on2016 the depending selected city on andthe theselected tilt angle. city and the tilt angle. Sustainability 2020, 12, 10344 9 of 17

Table 2. Total Electricity production and production for households for diﬀerent building types, orientation, cities, and tilt angles.

City Nablus Jerusalem Hebron Gaza year) year) year) year) / / / / year) year) year) year) / / / / 2016 (%) 2030 (%) 2016 (%) 2016 (%) 2030 (%) 2030 (%) 2030 (%) 2016 (%) Tilt Angle (kWh (kWh (kWh (kWh Orientation Building Type Production by Household Production by Household Production by Household Production by Household Production to Consumption Production to Consumption Production to Consumption Production to Consumption Production to Consumption Production to Consumption Production to Consumption Production to Consumption Total Production (kWh Total Production (kWh Total Production (kWh Total Production (kWh

27◦ 34,577 17,289 530 279 35,702 17,851 337 220 36,189 18,095 513 282 34,462 17,231 542 279 S-N 17◦ 34,414 17,207 527 277 35,475 17,738 334 219 35,896 17,948 509 280 34,144 17,072 537 276 7 40,602 20,301 622 327 41,638 20,819 393 257 42,245 21,123 599 329 40,284 20,142 633 326 A1 ◦ 27◦ 32,379 16,190 496 261 33,433 16,717 315 206 33,854 16,927 480 264 32,364 16,182 509 262 E-W 17◦ 32,130 16,065 492 259 33,134 16,567 312 205 33,543 16,772 475 261 32,033 16,017 504 259 7◦ 38,532 19,266 590 311 39,632 19,816 374 245 40,159 20,080 569 313 38,388 19,194 604 311 27◦ 50,971 12,743 390 205 52,484 13,121 247 162 53,257 13,314 377 207 50,808 12,702 399 206 S-N 17◦ 51,321 12,830 393 207 52,874 13,219 249 163 53,551 13,388 379 209 51,184 12,796 402 207 7 56,493 14,123 433 228 57,952 14,488 273 179 58,781 14,695 417 229 56,433 14,108 444 228 A2 ◦ 27◦ 47,587 11,897 364 192 49,073 12,268 231 151 49,709 12,427 352 194 47,481 11,870 373 192 E-W 17◦ 47,519 11,880 364 191 49,908 12,477 235 154 49,558 12,390 351 193 47,255 11,814 372 191 7◦ 57,628 14,407 441 232 59,047 14,762 278 182 59,881 14,970 424 233 57,357 14,339 451 232 27◦ 47,498 3958 121 64 48,813 4068 77 50 49,610 4134 117 64 47,471 3956 124 64 S-N 17◦ 47,670 3973 122 64 49,182 4099 77 51 49,792 4149 118 65 47,635 3970 125 64 7 54,440 4537 139 73 55,738 4645 88 57 56,510 4709 133 73 54,394 4533 143 73 B1 ◦ 27◦ 44,700 3725 114 60 46,047 3837 72 47 46,621 3885 110 61 44,597 3716 117 60 E-W 17◦ 44,653 3721 114 60 45,919 3827 72 47 46,496 3875 110 60 44,403 3700 116 60 7◦ 58,251 5825 178 94 59,631 5963 112 74 60,473 6047 171 94 57,820 5782 182 94 27◦ 95,497 3979 122 64 98,222 4093 77 51 99,671 4153 118 65 95,145 3964 125 64 S-N 17◦ 96,897 4037 124 65 99,760 4157 78 51 100,947 4206 119 66 96,542 4023 126 65 7 115,949 4831 148 78 118,569 4940 93 61 120,641 5027 142 78 115,215 4801 151 78 B2 ◦ 27◦ 93,181 3883 119 63 95,608 3984 75 49 97,355 4056 115 63 92,756 3865 122 63 E-W 17◦ 94,816 3951 121 64 97,635 4068 77 50 98,933 4122 117 64 94,372 3932 124 64 7◦ 114,846 4785 147 77 117,711 4905 92 61 119,369 4974 141 77 114,415 4767 150 77 Sustainability 2020, 12, 10344 10 of 17

Table 2. Cont.

27◦ 30,375 7594 233 122 31,217 7804 147 96 31,715 7929 225 124 30,373 7593 239 123 S-N 17◦ 30,694 7674 235 124 31,584 7896 149 97 31,943 7986 226 124 30,608 7652 241 124 7 31,794 7824 240 126 32,543 8009 151 99 32,916 8102 230 126 31,232 7684 242 124 C1 ◦ 27◦ 30,819 7705 236 124 31,631 7908 149 98 32,191 8048 228 125 30,738 7685 242 124 E-W 17◦ 31,252 7813 239 126 32,203 8051 152 99 32,626 8157 231 127 31,139 7785 245 126 7◦ 36,881 9220 282 149 37,890 9473 179 117 38,418 9605 272 150 36,699 9175 289 148 27◦ 41,452 5182 159 84 42,561 5320 100 66 43,047 5381 153 84 41,337 5167 162 84 S-N 17◦ 43,412 5427 166 87 44,713 5589 105 69 45,319 5665 161 88 43,254 5407 170 87 7 45,879 5735 176 92 46,602 5825 110 72 47,240 5905 167 92 45,317 5665 178 92 C2 ◦ 27◦ 41,022 5128 157 83 42,226 5278 100 65 42,925 5366 152 84 40,804 5101 160 83 E-W 17◦ 42,224 5278 162 85 43,464 5433 102 67 44,028 5504 156 86 42,000 5250 165 85 7◦ 47,121 5890 180 95 48,297 6037 114 75 48,955 6119 173 95 46,929 5866 184 95 Sustainability 2020, 12, 10344 11 of 17 Sustainability 2020, 12, x FOR PEER REVIEW 12 of 19

If we change the building orientation orientation to to East-West East-West for types A1 and A2 by rotating the building 90°90◦ counterclockwise thethe totaltotal electricityelectricity production production will will decrease decrease except except for for A2 A2 at aat tilt a tilt angle angle of 7 of◦ the 7° theproduction production will increase.will increase. The reductionThe reduction or increase or increase can be can justiﬁed be justified by thelower by the/higher lower/higher power installed power installeddue to the due new to PVthearrangement new PV arrangement on the rotated on the same rotated building same shape. building Consequently, shape. Consequently, the electricity the electricityproduction production share for eachshare residential for each unitresidential will decrease unit will in thedecrease range in of the 948 range to 1176 of kWh 948 /yearto 1176 for kWh/yearbuilding type for A1,building and in type the rangeA1, and of -284in the to range 998 kWh of -284 for buildingto 998 kWh type for A2 building depending type on A2 the depending tilt angles onand the selected tilt angles city and as can selected be seen city in Figureas can 5be and seen Table in Figure2. 5 and Table 2.

(a) (b)

Figure 5. For East-West orientation: ( aa)) the the annual annual electricity electricity production production for for each each household household unit unit A1 A1 and ( b) the annual electricity productionproduction for each household unit A2.

3.2. Residential Residential Building Building Type Type B For building building orientation orientation South-North, South-North, the the annual annual electricity electricity production production for building for building type B1 type (12 residentialB1 (12 residential units) in units)four different in four cities diﬀerent at three cities different at three tilt di anglesﬀerent are tilt in angles the ranges: are in 47,471 the ranges: kWh– 49,61047,471 kWh kWh–49,610 for the system kWh installed for the power system of installed 32 kW with power a tilt ofangle 32 of kW 27°; with 47,635 a tiltkWh–49,792 angle of kWh 27◦; for47,635 the kWh–49,792 same installed kWh power for the with same installeda tilt angle power of 17°; with and a tilt 54,394 angle ofkWh–56,510 17◦; and 54,394 kWh kWh–56,510 for the system kWh installedfor the system power installed of 39.36 powerkW with of tilt 39.36 angle kW 7°; with again tilt anglethese ranges 7◦; again vary these depending ranges vary on the depending selected cities.on the The selected annual cities. electricity The annual production electricity for each production household for unit each is household in the ranges unit 3956 is in thekWh–4134 ranges kWh3956 kWh–4134for the system kWh with for tilt the angle system 27°; with 3970 tilt kWh–4149 angle 27◦ kWh; 3970 for kWh–4149 the system kWh with for tilt the angle system 17°; withand 4533tilt angle kWh–4709 17◦; and kWh 4533 for kWh–4709 the system kWh with for tilt the angl systeme 7°; where with tilt these angle ranges 7◦; where vary depending these ranges on vary the selecteddepending cities on theas it selected can be citiesseen asin itFigure can be 6. seen If we in Figurecompare6. If the we compareelectricity the production electricity with production future consumptionwith future consumption in 2030 and the in 2030consumption and the consumptionof 2016 for each of 2016household, for each the household, production the represents production 0.5 torepresents 0.73 times 0.5 the to 0.73 2030 times electricity the 2030 consumption electricityconsumption and represents and 0.77 represents to 1.43 0.77times to 1.43the electricity times the consumptionelectricity consumption in 2016. These in 2016. ranges These vary ranges depending vary depending on the selected on the selectedcity and citythe andtilt angles the tilt as angles can be as seencan be in seenTable in 2. Table 2. For building type B2 (24 residential units) the annual electricity production is higher than B1 due to the fact that the roof is larger. However, the annual electricity production for each household unit is close to the building type B1, because the share of the roof is almost the same. This production for each household is in the range 3964 kWh–4153 kWh for the system installed power of 63.14 kW with a tilt angle of 27◦; 4023 kWh–4206 kWh for the same installed power with a tilt angle of 17◦; and 4801 kWh–5027 kWh for the system installed power of 81.6 kW with a tilt angle of 7◦; where these ranges vary depends on the selected cities as can be seen in Figure6. This production represents 0.51 to 0.78 times the 2030 electricity consumption for households and represents 0.77 to 1.51 times the electricity consumption of 2016 depending on the selected city and the tilt angle.

(a) (b)

Figure 6. For South-North orientation: (a) the annual electricity production for each household unit B1 and (b) the annual electricity production for each household unit B2.

For building type B2 (24 residential units) the annual electricity production is higher than B1 due to the fact that the roof is larger. However, the annual electricity production for each household Sustainability 2020, 12, x FOR PEER REVIEW 12 of 18

If we change the building orientation to East-West for types A1 and A2 by rotating the building 90° counterclockwise the total electricity production will decrease except for A2 at a tilt angle of 7° the production will increase. The reduction or increase can be justified by the lower/higher power installed due to the new PV arrangement on the rotated same building shape. Consequently, the electricity production share for each residential unit will decrease in the range of 948 to 1176 kWh/year for building type A1, and in the range of -284 to 998 kWh for building type A2 depending on the tilt angles and selected city as can be seen in Figure 5 and Table 2.

(a) (b)

Figure 5. For East-West orientation: (a) the annual electricity production for each household unit A1 and (b) the annual electricity production for each household unit A2.

3.2. Residential Building Type B For building orientation South-North, the annual electricity production for building type B1 (12 residential units) in four different cities at three different tilt angles are in the ranges: 47,471 kWh– 49,610 kWh for the system installed power of 32 kW with a tilt angle of 27°; 47,635 kWh–49,792 kWh for the same installed power with a tilt angle of 17°; and 54,394 kWh–56,510 kWh for the system installed power of 39.36 kW with tilt angle 7°; again these ranges vary depending on the selected cities. The annual electricity production for each household unit is in the ranges 3956 kWh–4134 kWh for the system with tilt angle 27°; 3970 kWh–4149 kWh for the system with tilt angle 17°; and 4533 kWh–4709 kWh for the system with tilt angle 7°; where these ranges vary depending on the selected cities as it can be seen in Figure 6. If we compare the electricity production with future consumption in 2030 and the consumption of 2016 for each household, the production represents 0.5 to 0.73 times Sustainabilitythe 2030 electricity2020, 12, 10344 consumption and represents 0.77 to 1.43 times the electricity consumption in12 2016. of 17 These ranges vary depending on the selected city and the tilt angles as can be seen in Table 2.

Sustainability 2020, 12, x FOR PEER REVIEW 13 of 18 each household is in the range 3964 kWh–4153 kWh for the system installed power of 63.14 kW with a tilt angle of 27°; 4023 kWh(a) –4206 kWh for the same installed power with (ab tilt) angle of 17°; and 4801 kWh–5027 kWh for the system installed power of 81.6 kW with a tilt angle of 7°; where these ranges vary Figuredepends 6. For on South-Norththe selected orientation: orientationcities as can: ((aa) )be the the seen annual annual in electricityFigure electricity 6. productionThis production production for for each each represents household household unit0.51 unit B1to 0.78 timesB1and the and ( b2030) ( theb) theelectricity annual annual electricity electricityconsumption production producti for foronhouseholds for each each household household and represents unit unit B2. B2. 0.77 to 1.51 times the electricity consumption of 2016 depending on the selected city and the tilt angle. ForAs inbuilding the case type of buildingB2 (24 residential types A1 units) and A2, the ifannu we changeal electricity the building production orientation is higher to than East-West B1 due As in the case of building types A1 and A2, if we change the building orientation to East-West tofor the building fact that types the B1roof and is larger. B2 the However, total electricity the annual production electricity will decreaseproduction except for each for B1 household at a tilt angle unit for building types B1 and B2 the total electricity production will decrease except for B1 at a tilt angle isof close 7 the to production the building will type increase. B1, because Consequently, the share theof the electricity roof is almost production the same. share This for each production residential for of 7°◦ the production will increase. Consequently, the electricity production share for each residential unit will decrease in the range of 330 to 274 kWh/year for building type B1 and in the range of 34 to unit will decrease in the range of −330 to 274 kWh/year for building type B1 and in the range of 34 to 99 kWh/year for building type B2 depending on the tilt angles and selected city as it can be seen in 99 kWh/year for building type B2 depending on the tilt angles and selected city as it can be seen in Figure7 and Table2. Figure 7 and Table 2.

(a) (b)

Figure 7. For East-West orientation:orientation: ( a) the annual electricity production for each household unit B1 and (b) the annual electricityelectricity productionproduction forfor eacheach householdhousehold unitunit B2.B2.

3.3. Residential Building Building Type Type C C For building orientation orientation South-North, South-North, the the annual annual electricity electricity production production for forbuilding building type type C1 C1(four (four residential residential units) units) in four in fourdifferent diﬀerent cities citiesat three at threedifferent diﬀ erenttilt angles tilt angles are in arethe inranges the ranges30,373 30,373kWh–31,715 kWh–31,715 kWh for kWh the system for the installed system power installed of 20.5 power kW of with 20.5 a kWtilt angle with of a tilt27°; angle30,608 ofkWh 27◦–; 30,60831,943 kWh–31,943kWh for the kWhsame for installed the same power installed with power a tilt withangle a tiltof 17°; angle and of 1731,232◦; and kWh 31,232–32,916 kWh–32,916 kWh for kWh the forsystem the systeminstalled installed power of power 25 kW of with 25 kW a withtilt angl a tilte of angle 7°; again of 7◦ ;these again ranges these rangesvary depending vary depending on the onselected the selected cities. The cities. annual The electricity annual electricity production production for each household for each household unit are in unitthe ranges are in 7593 the ranges kWh– 75937929 kWh kWh–7929 for the kWh system for with the system tilt angle with 27°; tilt 7652 angle kWh 27–◦7986; 7652 kWh kWh–7986 for the system kWh for with the tilt system angle with 17°; tiltand angle 7708 kWh 17◦;– and8229 7708 kWh kWh–8229 for the system kWh with for thetilt systemangle 7°; with where tilt these angle ranges 7◦; where vary thesedepending ranges on vary the dependingselected cities on theas can selected be seen cities in as Figure can be 8. seen If we in Figure compare8. If the we compareelectricity the production electricity productionwith future withconsumption future consumption in 2030 and the in 2030consumption and the consumptionof 2016 for each of household, 2016 for each thehousehold, production therepresents production 0.96 representsto 1.26 times 0.96 the to 1.262030 times electricity the 2030 consumption electricity consumptionand represents and 1.47 represents to 2.42 1.47times to 2.42the electricity times the electricityconsumption consumption in 2016. These in 2016. ranges These vary ranges depending vary depending on the selected on the selectedcity andcity the andtilt angles the tilt as angles can be as canseen be in seenTable in 2. Table 2. Sustainability 2020, 12, 10344 13 of 17 Sustainability 2020, 12, x FOR PEER REVIEW 14 of 18

(a) (b)

Figure 8. For South-North orientation:orientation: ((aa)) thethe annual annual electricity electricity production production for for each each household household unit unit C1 C1and and (b) ( theb) the annual annual electricity electricity production production for for each each household household unit unit C2. C2.

For building type C2 (eight residential units) th thee total annual electricity production is higher thanthan C1 due to the fact that the roof is larger.larger. However, the annual electricity production for each household unit is less than C1, because the household unit share of the roof area is less than the share share inin building type C1. This This production production for for each each household household is is in in the range 5167 kWh kWh–5381–5381 kWh for the system installed power of 29.52 kW with a tilt angle of 27°; 27◦; 5407 5407 kWh kWh–5665–5665 kWh kWh for for the the same same installed installed power with a tilt angle of 1717°;◦; and 5665 kWh kWh–5905–5905 kWh for the system installed power power of of 35.7 kW with tilt angle 7°; 7◦; where these ranges ranges vary vary depends depends on on the the selected selected cities cities as as can can be be seen seen in in Figure Figure 88.. This production represents 0.66 to 0.92 times the 2030 electricity consumption for households and represents 1.01.0 toto 1.781.78 timestimes the the electricity electricity consumption consumption of of 2016 2016 depending depending on on the the selected selected city city and and the thetilt angle.tilt angle. IfIf we change the building orientation orientation to to East-West East-West for building type C1 the total electricity production will increase, because the spacing between the arrays is higher which will increase the efficiency.efficiency. Consequently, the electricity production share for each residential unit will increase in the range ofof 9292 to to 1376 1376 kWh kWh/year./year. For For building building type type C2 theC2 totalthe total electricity electricity production production will decrease, will decrease, except exceptfor the for PV the system PV system at a tilt at angle a tilt of angle 7◦ the of production 7° the production will increase. will increase. The electricity The electricity production production for each forhousehold each household will change will inchange the range in the of range 14 to -214of 14 kWh to -214/year kWh/year depending depending on the tilt on angles the tilt and angles selected and selectedcity as it city can as be it seen can inbe Figure seen in9 andFigure Table 9 and2. Table 2. From the results above, it could be concluded that electricity production from the PV solar panel is totally dependent on the building type. The energy production for building type A and B is more for North-South orientation while building type C has more energy production for East-West orientation. The tilt angles 27 and 17 give almost similar results for the different building types and they give the best specific yearly yield (kWh production for each installed kW) since PV array production totally depends on the tilt angle (for maximum solar energy capture) and the space between the arrays (self-shading effect). Because the tilt angle 27 is the optimum tilt angle for achieving the highest energy for most cities in Palestine, it requires a further distance between the arrays, which has a negative shading effect by reducing the resulting energy. On the other hand, the angle 17 does not give the highest energy output, but it requires less distance between the arrays. Therefore, if there is enough spacing between the arrays and enough area(a on) the building roof then the best tilt angle for(b) maximum PV production is aboutFigure 27◦ for 9. For the East-West same kW orientation power installed.: (a) the annual However, electricity if there producti is limitedon for each space household between unit the C1 arrays, thenand the ( maximumb) the annual production electricity producti is at theon tilt for angle each 17household◦, for the unit same C2. kW power installed. For Example A1: South-North (Hebron city) the total production at 27◦ and space is 1.4 m is equal 36,189 kWh, whileFrom at 17 the◦, and results space above, is 1.2 it m could the total be concluded production that is 35,896 electricity kWh. production For A2: South-North from the PV (Hebron solar panel city) isthe totally total productiondependent aton 27 the◦ and building space type. is 1.3 The m is ener equalgy 53,257 production kWh, whilefor building at 17◦, andtype spaceA and is B 1.2 is mmore the fortotal North-South production isorientation 53,551 kWh. while While building the tilt angletype C 7 giveshas more the best energy yearly production kWh production for East-West for each orientation.m2 of the roof The area tilt sinceangles it has27 and the 17 maximum give almost installed similar kW. results for the different building types and they give the best specific yearly yield (kWh production for each installed kW) since PV array production totally depends on the tilt angle (for maximum solar energy capture) and the space between the arrays (self-shading effect). Because the tilt angle 27 is the optimum tilt angle for Sustainability 2020, 12, x FOR PEER REVIEW 14 of 18

(a) (b)

Figure 8. For South-North orientation: (a) the annual electricity production for each household unit C1 and (b) the annual electricity production for each household unit C2.

For building type C2 (eight residential units) the total annual electricity production is higher than C1 due to the fact that the roof is larger. However, the annual electricity production for each household unit is less than C1, because the household unit share of the roof area is less than the share in building type C1. This production for each household is in the range 5167 kWh–5381 kWh for the system installed power of 29.52 kW with a tilt angle of 27°; 5407 kWh–5665 kWh for the same installed power with a tilt angle of 17°; and 5665 kWh–5905 kWh for the system installed power of 35.7 kW with tilt angle 7°; where these ranges vary depends on the selected cities as can be seen in Figure 8. This production represents 0.66 to 0.92 times the 2030 electricity consumption for households and represents 1.0 to 1.78 times the electricity consumption of 2016 depending on the selected city and the tilt angle. If we change the building orientation to East-West for building type C1 the total electricity production will increase, because the spacing between the arrays is higher which will increase the efficiency. Consequently, the electricity production share for each residential unit will increase in the range of 92 to 1376 kWh/year. For building type C2 the total electricity production will decrease, except for the PV system at a tilt angle of 7° the production will increase. The electricity production Sustainabilityfor each household2020, 12, 10344 will change in the range of 14 to -214 kWh/year depending on the tilt angles14 ofand 17 selected city as it can be seen in Figure 9 and Table 2.

(a) (b)

Figure 9. For East-West orientation:orientation: ( a) the annual electricity productionproduction for each household unit C1 and (b)) thethe annualannual electricityelectricity productionproduction forfor eacheach householdhousehold unitunit C2.C2.

ForFrom building the results types, above, A1 it and could A2, be where concluded the share that electricity of roof area production for each from apartment the PV unit solar is panel high 2 (150–200is totally mdependent), installing on PVthe systemsbuilding at type. the optimum The ener tiltgy production angle of 27◦ forwill building provide type the building A and B withis more the electricityfor North-South with low orientation investment while (low installedbuilding power). type C The has production more energy for A1 production apartments for isaround East-West 3 to 5orientation. times its electricity The tilt angles consumption 27 and in17 2016 give and almost around similar 2 to 3results times thefor the consumption different building in 2030, dependingtypes and onthey the give selected the best city, andspecific the productionyearly yield for (kWh A2 apartments production is 2.5for toeach 4 times installed its electricity kW) since consumption PV array inproduction 2016 and 1.5totally to 2 depends times the on electricity the tilt consumptionangle (for maximum in 2030 dependingsolar energy on capture) the orientation and the and space the selectedbetween city.the arrays (self-shading effect). Because the tilt angle 27 is the optimum tilt angle for For building type C1 where the share of the roof area for each apartment unit is (45 m2), installing a PV system at the tilt angle of 17◦ will give the space to increase the distance between PV arrays and increase the total production. The production for C1 apartments is around 1.5 to 2.45 itis electricity consumption in 2016 and around 0.97 to 1.27 times electricity consumption in 2030. For building type C2 where the share of the roof area for each apartment unit is low (31 m2), installing a PV system at the tilt angle of 7◦ will give the best production to cover its electricity consumption. The production for each apartment is around 1.1 to 1.84 its electricity consumption in 2016 and around 0.72 to 0.95 times electricity consumption in 2030 depending on the orientation and the selected city. For building types, B1 and B2, where the share of the roof area for each apartment unit is low 2 (25 m ), installing a PV system at the lower tilt angle of 7◦ will give the space to install more power and increase the total electricity production. The production for B1 and B2 apartments is around 0.75 to 1.78 times its electricity consumption in 2016 and around 0.6 to 0.75 times the consumption in 2030, depending on the orientation and the selected city. The evaluation of the payback period and the economic benefits of installing PV systems, perform the analysis for all building types and all Palestinian cities taking into consideration different possibilities for tilt angles can be considered as limitations for this study. Moreover, it is recommended to examine the expected effect of installing these PV systems on the urban energy demands in the Palestinian cities since some building types can produce a surplus of their electricity consumption.

4. Conclusions Although the problems for the energy sector in Palestine are well known, evaluating the solar energy production for the targeted residential buildings typologies in this climatic and economic contest has not been done before. The results from this research can support the efforts toward future energy sustainability and the use of solar energy in residential buildings. The research used a new developed approach which brings together a combination of energy consumption in residential buildings, surveying the most used residential typologies and renewable energy production for different scenarios using computer simulation tools. This research will contribute to the evaluation studies needed for decision making and scientific communities in terms of new results, evaluating the parameters affecting energy production from installing PV on residential buildings and a proposed approach to achieve energy sustainability. Sustainability 2020, 12, 10344 15 of 17

The sunshine availability (around 3000 h/year) and the high solar radiation intensity, which can reach up to 2050 kWh/m2 in this region, make the PV system one of the best options for residential building owner’s to invest in renewable energy. A 1 kW system in Palestine installed at the rooftop at optimum tilt and orientation angles generates up to 1635 kWh/year in Hebron, 1613 kWh/year in Jerusalem, 1562 kWh/year in Nablus, and 1557 kWh in Gaza city. These results are in line with the results from another study in a neighboring country which gives around 1560 KWh annual production [43]. The annual kWh production per m2 for the Palestinian cities could reach 250 kWh/m2 per year. There is a small difference in power production by PV solar panels for the Palestinian cities. Hebron has the highest power production where Gaza city has the lowest. PV installation on the rooftop of residential buildings can provide electricity production compared to the buildings consumption in ranges between 0.5 to 6 times depending on the selected city, building type and shape, tilt angle, spacing between arrays, building orientation and installed power. These results can be adapted in similar climatic conditions and similar building types, especially in the east Mediterranean region. Residential buildings in urban areas in Palestinian cities have the potential to provide electricity production to mitigate the current and future increasing electricity demand in Palestine. Building types A1 with two residential units and A2 with four residential units can give an electricity production that surpasses their average current and 2030 future electricity consumption. While building types B1 with 12 residential units and B2 with 24 residential units can produce more than half their current and future electricity consumption. Building type C1 with four residential units can produce its future electricity consumption, and around double the electricity consumption in 2016. Building types C2 with 8 residential units can produce more than half its future electricity consumption for households in 2030 and represents its electricity consumption of 2016. Changing building orientation for the same roof area will result in different distribution on solar PV arrays and can result in decreasing or increasing the electricity production depending on the building dimensions (the building length on the S-N or E-W) and spacing between the PV arrays. The tilt angle can play an important role in determining the quantity of the PV installation based on the available roof area, the number of floors, and the number of residential units. The highest specific yearly yield from PV systems (kWh generated by 1kWp) occurs at the optimum tilt angle (27◦), however, the installed power and the total building electricity production is the lowest, due to the large distance between PV arrays. This can be the best option for building type (A) as there is enough area for electricity production (roof area/number of household units). The lower tilt angle of around 7◦ is the best option for low rooftop availability (roof area/number of household units) for installing PV systems, as it gives the highest installed power and the highest electricity production, this is because the distance between PV arrays is small which will allow for more PV power installation. This can be the best option for building types (B) and (C). If there is enough spacing between the arrays and enough area on the building roof, then the best tilt angle for maximum PV production is about 27◦ for the same kW power installed. If there is limited space between the arrays, then the maximum production is about 17◦, for the same kW power installed. The tilt angles 27◦ and 17◦ give almost similar results for the different building types and they give the best specific yearly yield (kWh production for each installed kW). While the tilt angle 7◦ gives the best yearly kWh production for each m2 of the roof area. The specific yearly yield could reach 2 2 1650 kWh/kW at tilt angle 27◦ and the kWh production per m could also reach 250 kWh/m /year for tilt angle 7◦.

Author Contributions: S.M., R.A., and A.J. conceived and performed the article. R.A., S.M. and A.J. simulated and analyzed the data; S.M., A.J., M.I. and R.A. wrote the paper. All authors revised the manuscript. They share the structure and aims of the manuscript, paper drafting, editing and review. All authors have read and approved the final manuscript. Funding: This research received no external funding. Conflicts of Interest: The authors declare no conflict of interest. Sustainability 2020, 12, 10344 16 of 17

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