A Comparative Analysis of Sunshine Duration Effects in terms of Renewable Energy Production Rates on The LEED BD + C Projects in Turkey

Abstract

Global warming has been on the agenda over the past few years. Solutions to global warming and energy efficiency problems have brought with them the need for green building market. Leadership in Energy and Environmental Design (LEED) is a certification system regulating the compliance of green buildings to certain standards and is essential for construction projects focusing on sustainability and innovation. This study investigates the effects of sunshine duration on construction projects reducing annual electricity consumption and increasing renewable energy production. In this study, the effects of sunshine duration times on construction projects are located in different cities in Turkey which has gained point from LEED BD+C (NC) (LEED, Building Design + Construction: New Construction) certificate were analyzed with the help of getting the impact of annual electricity consumption and renewable energy production rates. It was our aim that the results will be used for construction projects in compliance with the “Energy and Atmosphere” category of the LEED BD+C certification system.

1. Introduction

The increased consumption of natural resources in recent years has called for renewable energy sources. Due to the rapid development of human civilization and expansion of the global economy, fossil fuel energy is going to be exhausted [1]. Besides, the consumption of natural resources is expected to increase gradually in the coming years. According to IEA (International Energy Agency) (2018), the share of renewable resources in total primary energy will reach 15,91 Mtoe (Million tonnes of oil equivalent) between 2017 and 2025, and electricity consumption will be the highest with 44,94 Mtoe. According to IEA preliminary estimates, global energy demand grew by 2.1% in 2017, which is twice the growth rate in 2016 [2].

The widespread use of electricity and burning of natural fuels have increased the earth’s temperature 1 °C over the last century [3]. It is widely accepted that fossil fuel consumption leads to high rates of carbon emissions, resulting in global warming [4]. According to IPCC (Intergovernmental Panel on Climate Change), global warming should be kept at 1.5 °C levels [5].

Table 1. Causes and consequences of global warming [6].

Causes
Solar radiation	Greenhouse gas emissions	Using fuels	Natural disasters	Economic problems
Consequences
Temperature Rise	Sea Level Rise	Biodiversity and Ecosystem Transformation	Increased Ocean Acidity	Diseases
Extreme hot days	Melting of ice sheets	Extinction	Threats to ocean life	Malaria, Tuberculosis, HIV/AIDS
Droughts	Global sea level rise	Terrestrial land area transformation		Reduction in yields of cereal crops
Heavy precipitation	Exposure of small islands	Degradation of forests

shows the causes and consequences of global warming.

The share of the construction sector in the global economy stands at 15%, while it is about 9% in Turkey. It is, however, expected to be 10% and 17% in developed and developing countries, respectively until 2025 [7]. Many studies focus on the reduction of energy consumption and carbon emissions in buildings, which is one of the primary causes of global warming [8,9,10,11,12,13].

In recent years, energy saving methods in buildings have drawn significant attention for the prevention of global warming. The use of renewable energy sources in buildings is promoted across The European Union by support schemes applied to achieve sustainability, security of supply and improved competitiveness [14]. BP (British Petrol) Statistical Review of World Energy 2018 shows that the electricity demand increased by 6% and carbon emissions by 12.7% in 2017 in Turkey [15].

The study investigated the correlation between sunshine duration and renewable energy production in three LEED BD + C (NC) certified construction projects in which PV panels are used for renewable energy production. The results aim to encourage construction firms to use photovoltaic panels to reduce carbon emissions in buildings.

2. Literature Review

2.1. LEED BD + C Certification System

Recently, such concepts as green building and passive house have emerged, focusing on reducing energy consumption and carbon emissions in buildings. There are also some standards used to verify such buildings’ sustainability and energy saving and carbon reduction efficiency. Countries have developed rating systems to determine the level of green achievement. The main objective of these certification systems is to bring certain standards to the green building sector. LEED (Leadership in Energy and Environmental Design) is the most popular rating system. It is a framework that enables building owners and operators to identify and implement practical and measurable green building designs, constructions, and operations and maintenance solutions [16]. The LEED green building rating system rates designs based on sustainability, energy savings, and improvements in indoor environment quality [17].

A subcredit of the LEED BD+C certification system, referred to as New Construction, is mostly used to rate the construction projects in Turkey. There were 223 LEED certified projects in Turkey in 2017, 116 of which were certified under the category of LEED BD + C (New Construction). In other words, 52% of LEED certified projects applied for the New Construction category in Turkey [18].

2.2. Renewable Energy Generation in Turkey

Solar energy accounts for 3.28 percent of total electricity in Turkey (Figure 1). According to the Turkish Electricity Transmission Corporation data (2018), the total energy produced by PV panels is 4.726 MW [19].

Table 2. Energy production by renewable sources in Turkey (2017) [19].

Renewable Sources	GWh (Gigawatt Hours)	%
Renew waste + waste heat	2.972,3	3.37
Wind	17.903,8	20.32
Solar	2.889,3	3.28
Dam	41.312,6	46.89
N. lake and run of river	16.905,9	19.19
Geothermal	6.127,5	6.95
Total	88.111,4	100

shows the energy production by renewable resources in Turkey.

According to the Greenhouse Gas National Inventory (2008), the housing sector in Turkey accounts for 16% of national CO₂ (Carbon Dioxide) emissions (270 million tons) and 18% (48 million tons) of the energy sector. It is, therefore, of great importance to take into account building structures and exploit renewable energy systems to reduce energy consumption and improve thermal comfort [20]. Solar energy is abundant and clean; therefore, conventional energy systems should be replaced with solar power systems in buildings [21]. Solar power generation accounts for only 1% of all power generation in Turkey in 2017 (Figure 2).

Table 3. Power generation by energy sources in Turkey (2017) [19].

Energy Source	Generation (GWh)	Contribution (%)
Renew waste + waste heat	2.972,3	3.37
Wind	17.903,8	20.32
Solar	2.889,3	3.28
Dam	41.312,6	46.89
N. lake and run of river	16.905,9	19.19
Geothermal	6.127,5	6.95
Total	88.111,4	100

shows power generation by energy sources in 2017 in Turkey.

Photovoltaic (PV) systems have attracted significant attention in recent years. Turkey has long hours of sunshine and is, therefore, very suitable to use of solar power systems to generate electricity from PV panels. In Turkey, the maximum daily sunshine duration is 10.96 hours in July and the average daily sunshine duration is 7.5 hours. Moreover, the total installed capacity of the PV power plant was 4,726 MW (Megawatt) in June 2018 [22].

2.3. Photovoltaic Panels

Electricity demand will increase by about 2.6% with the most likely level of global warming arriving at 1.9 °C [23]. PV systems provide a reliable power supply in buildings with or without an electrical grid [24]. A photovoltaic power generation system consists of multiple components such as cells, mechanical and electrical connections, and mountings and means of regulating and/or modifying the electrical output. A PV system is rated in peak kilowatts (kWp), referring to the amount of power that it is expected to generate when the sun is directly overhead on a clear day [25]. Singh (2013) also suggested that the weather conditions affect the power generation of PV panels [26]. The main objective of this study is to compare the renewable energy production rates of LEED BD + C certified projects in terms of sunshine durations of cities in three climatic zones of Turkey. Three LEED BD + C (NC) certified projects were selected to understand and analyze the relationship between sunshine duration and renewable power generation by PV panels.

3. Methodology

Three LEED BD + C (NC) certified projects from three cities in different climatic zones of Turkey were examined in terms of the relationship between sunshine duration and renewable energy production. General information about the projects were presented. Then, the annual hours of sunshine in the cities were determined and presented in Graph. The sunshine duration data of the cities were obtained from the General Directorate of Energy Affairs of Turkey. Afterwards, the amount of electricity consumed and generated by PV panels was determined through interviews with firms. Renewable energy production rates were calculated and presented as follows:

$$RenewableEnergyProduction(\%)=\frac{E_P}{E_G}\times 100$$

(1)

E_P: The electricity produced (kW-Kilowatt)

E_G: The electricity generated (kW-Kilowatt)

One criterion for the selection of the projects was electricity production from PV panels. The general information about these projects are given below:

Project 1, which is in the city of Gaziantep, is the first passive house project in Turkey. The building is approximately 325 m² [27]. There are photovoltaic panels in the garden of the building to meet the energy demand. Project 2, which is in the city of Konya, is a 40.312 meter square project in which a 100 kW installed photovoltaic system is used to generate power. Project 3, which is in the city of Istanbul, is a 400 m² project in which 36 photovoltaic panels have been placed on the roof of a building to generate 27% of the electricity used in the building. Each panel has 200 watts of power. The data on the amount of energy produced annually by PV panels in Projects 1 and 3 was obtained. The data on the amount of energy consumed and produced annually (between May 2017 and April 2018) by PV panels in Project 2 were obtained from the Unilever company by personal interview. The data were compared with those reported by previous studies.

4. Results and Discussion

Table 4. Monthly variation in temperature in three cities between 1930–2018 [28].

	Months	Jan.	Feb.	Mar.	April	May	June	July	Aug.	Sep.	Oct.	Nov.	Dec.
Cities
Gaziantep		3.6	4.4	8.5	13.6	18.8	24.3	28.1	27.7	23.1	16.6	9.4	5.1
Konya		−0.2	0.8	5.5	11.0	15.7	20.4	23.6	23.4	18.9	12.7	5.8	1.6
Istanbul		5.8	5.5	7.3	11.2	15.7	20.5	22.9	23.4	19.9	15.8	11.0	7.8

and Figure 3 show the monthly variation in temperature and annual sunshine duration, respectively.

The cities have the most and fewest hours of sunshine in summer and winter months, respectively. July and December have the longest and shortest sunshine duration, respectively.

Table 5. Amount of energy consumed and produced monthly by PV panels in Gaziantep Green House Project (2017) [27].

Months	Electricity Consumption (kW)	Electricity Production (kW)	Renewable Energy Prod. (%)	Electricity Prod./ Electricity Cons.
January	2.638,00	1.430,00	4.51	54.21
February	2.046,00	2.167,00	6.84	105.91
March	1.632,00	2.466,00	7.79	151.10
April	1.017,00	3.094,00	9.77	304.23
May	1.003,00	3.312,00	10.46	330.21
June	1.188,00	3.584,00	11.31	301.68
July	2.120,00	3.476,00	10.97	163.96
August	2.336,00	3.308,00	10.44	141.61
September	2.198,00	3.220,00	10.17	146.50
October	1.595,00	2.611,00	8.24	163.70
November	2.047,00	1.629,00	5.14	79.58
December	2.700,00	1.379,00	4.35	51.07
TOTAL	22.520,00	31.676,00	-	-

shows the effect of sunshine duration on electricity production and consumption.

The PV panels in the Gaziantep Green House Project produce and consume the highest amount of energy in June (3.584,00 kW) and December (2.700,00 kW), respectively. The highest ratio of energy production to consumption is in May (330.21%).

Gaziantep is in the southeast of Turkey. It is sunnier in winter and hotter in summer in Gaziantep than in Konya and Istanbul. The minimum electricity consumption in Gaziantep is in spring due to reduced heating demand and longer use of daylight. However, electricity consumption is high in summer due to an increase in air conditioning use.

Table 6. The annual electricity consumption and production values of Konya Unilever Vector Admin Building.

Months	Electricity Consumption (kW)	Electricity Production (kW)	Renewable Energy Prod. (%)	Electricity Production/ Electricity Consumption
May 2017	11.041,7	8.000,00	7.22	72.45
June 2017	11.417,33	15.000,00	13.54	131.38
July 2017	12.873,92	15.200,00	13.72	118.07
August 2017	12.112,73	15.000,00	13.54	123.84
September 2017	11.276,94	13.000,00	11.73	115.28
October 2017	11.184,31	8.100,00	7.31	72.42
November 2017	12.886,78	6.100,00	5.51	47.34
December 2017	12.722,39	4.600,00	4.15	36.16
January 2018	15.764,27	4.100,00	3.70	26.01
February 2018	12.391,91	5.900,00	5.32	47.61
March 2018	10.436,17	7.900,00	7.13	75.70
April 2018	7.863,00	7.900,00	7.13	100.47
TOTAL	141.971,45	110.800,00

shows the amount of energy consumed and produced monthly by the PV panels in Konya Unilever Vector Admin Building.

The PV panels in the Konya Unilever Vector Admin Building Project consume the highest and produce the lowest amount of energy in winter months. They generate the highest amount of energy in July (15.200,00 kW). The highest ratio of energy production to consumption is in June (131.38).

The minimum electricity consumption in Konya is in spring and autumn due to reduced heating demand as well. The PV panels in the Konya Unilever Vector Admin Building Project generate a higher amount of energy than those in the Gaziantep Green House Project. It is cooler in Konya in summer evenings than in Gaziantep, resulting in a reduction in cooling demand in buildings.

Table 7. Amount of energy consumed and generated monthly by PV panels in Istanbul Erke Green Academy Building Project [29].

Months	Electricity Consumption (kW)	Electricity Production (kW)	Renewable Energy Production (%)	Electricity Production/ Electricity Consumption
January	3332	313	3.31	9.39
February	3143	438	4.63	13.94
March	2.994	698	7.39	23.31
April	2532	967	10.23	38.19
May	2801	1208	12.78	43.13
June	2850	1263	13.37	44.32
July	3435	1291	13.66	37.58
August	2886	1153	12.20	39.95
September	2929	875	9.26	29.87
October	1972	608	6.43	30.83
November	2618	369	3.90	14.09
December	3066	267	2.83	8.71
TOTAL	34558	9450

shows the amount of energy consumed and produced monthly by the PV panels in the Istanbul Erke Green Academy Building Project. Also, it is shown in Table 7 that the maximum electricity production/consumption value was gained in June. However, the renewable energy production rate was 13.66% in June. Of the three cities, Istanbul has the fewest hours of sunshine. Therefore, the PV panels in the Istanbul Erke Green Academy Building Project generate a higher amount of energy than those in the other two projects in winter due to an increase in lighting need in the building. The amount of energy generated in winter decreases due to a reduction in the number of hours of sunshine.

The three cities have the most and fewest hours of sunshine in summer and winter, respectively, and the average number of hours of sunshine over the year is 3.75. Almorox and Hontoria (2004) reported that global solar radiation correlations perform better in summer months [30]. Wang et. al. reported that the ratio of rural to urban dimming generally increases from 0.39 to 0.87 [31]. Hao et. al. (2007) also stated that solar radiation correlations perform better in summer and autumn than in spring and that annual correlations are similar to winter correlations but better than spring correlations [32]. According to Rehman et. al. (2007), the electricity demand patterns in Saudi Arabia are similar to the global solar radiation and sunshine duration data. These results indicate that PV-based power generation is an effective method to meet the peak load requirements in summer and in daylight hours throughout the year [33]. The results of this study show that the PV panels in the three projects produce the highest amount of electricity in summer, indicating that electricity generation by PV panels is highly correlated with sunshine duration.

The results show that there is a positive correlation between sunshine duration and renewable energy generation but that monthly variation in temperature also affects the amount of renewable energy generated. Project 1 generates 2.75% less energy than Project 2 in July, when both cities have almost an equal number of hours of sunshine. This is due to the fact that Project 1 needs more cooling than Project 2 in summer. The PV panels in the Projects produce a similar amount of energy in the months with similar average temperature and sunshine duration while they produce less energy in the months when electricity consumption increases.

5. Conclusions

This study analyzed the amount of energy consumed and produced by PV panels in three LEED BD + C certified projects in three cities to investigate the correlation between sunshine duration and renewable energy production. The results showed that PV panels can produce 10–15% of the energy consumed in cities with many hours of sunshine. Therefore, using PV panels in buildings especially in regions with warm winter and many hours of sunshine will promote renewable energy, reduce greenhouse gas emissions and mitigate the negative impacts of global warming.

The results indicate that the more hours of sunshine, the more electricity generation in winter and the more electricity consumption in summer. The results also indicate that electricity generation is higher in cities with many hours of sunshine in summer but with a low monthly average temperature.

Heat insulation materials and energy-efficient electrical fittings should be used, and buildings should be designed in a way to maximize daylighting in order to reduce electricity consumption and mitigate the negative impacts of global warming.