Designing of a Hybrid Photovoltaic Structure for an Energy-Efficient Street Lightning System Using PVsyst Software ^†

Abstract

With the depletion of traditional fossil fuels, their disastrous impact on the environment and rising costs, renewable energy sources such as photovoltaic (PV) energy are rapidly emerging as sustainable and clean sources of power generation. The performance of photovoltaic systems is based on different factors such as the type of photovoltaic modules, irradiation potential and geographic location. In this research, PVsyst simulation software is used to design and simulate a hybrid photovoltaic system used to operate energy-efficient street lightning system. The simulation is performed to analyze the monthly/annual energy generated (kWh) by the hybrid system and specific power production (kWh/KWp). Additionally, various PV system losses are also investigated. The hybrid PV system has 4 parallel strings, and each string has 13 series-connected (mono crystalline 400 W Canadian Solar) PV modules. The energy storage system consists of 16 Narada (AcmeG 12 V 200) batteries with a nominal capacity of 1600 Ah. The simulation results show that the total annual energy production and specific energy production, were calculated to be 26.68 MWh/year and 1283 kWh/kWp/year, respectively. Simulation results also show the maximum energy injected into the utility grid in the month of June (1.814 MWh) and the minimum energy injected into the utility grid in the month of January (0.848 MWh). The battery cycle state of wear is 84.8%, and the static state of wear is 91.7%. Performance ratio (PR) analysis shows that the highest performance ratio of the hybrid system was 68.2% in December, the lowest performance ratio was 62.7% in May and the annual average performance ratio of a hybrid PV system is 65.57%. After identifying the major source of energy losses, the detailed losses for the whole year were computed and shown by the loss diagrams. To evaluate the cost effectiveness of the proposed system, a simple payback period calculation was performed.

1. Introduction

Photovoltaic systems play a significant role in decreasing global warming and achieving climate change targets relating to carbon emissions and environmental issues [1,2,3,4]. The photovoltaic system has the ability to transform solar energy into electricity. The important aspect here is the need to store the electrical energy obtained from the sun in order to feed the system during non-sunny hours [5,6]. This objective could be achieved using a battery bank or connecting the PV systems to the utility system [7,8,9]. Industrial, commercial and domestic customers are highly benefitted by standalone or grid-connected PV systems to reduce their peak demand. The important parameters of a PV system are performance ratio, solar power yield and system loss. The performance ratio is a key indicator for analyzing the efficiency of the photovoltaic system. Performance ratio (PR) gives the relationship between the actual output of the solar energy and the theoretical output, regardless of different system losses, such as cell mismatch losses, PV module temperature losses, inverter efficiency losses, electric cable losses, etc. [10,11,12,13]. On days with high temperatures, the performance of photovoltaic (PV) modules are improved by using coolants that protect PV modules from overheating [14].

Generally, electricity from the utility grid has been used to power street lights. However, frequent blackouts and an intermittent supply of electricity to consumers often leads to a loss of lives and property due to continuous darkness on city highways as well as on local streets. Recent technological advancements have shown that renewable energy resources such as PV systems can be used to power street lights [15]. For public street lighting, a considerable number of standalone or grid-connected photovoltaic (PV) systems have been developed. One of the most viable street lighting systems is the photovoltaic street lighting system (PSLS), and PSLS provide a cost-effective power supply [16].

A centralized PV system consists of photovoltaic modules, inverters and a battery storage system. The energy generated by the PV system is distributed using electric cables to feed street lights in the inner city or adjacent areas. Using a centralized PV system, the occurrence rate of solar street lights vandalization or damaging will be reduced, and additional produced power will feed into the grid by net metering process. Therefore, in this article, the designing of a grid-connected hybrid photovoltaic energy generation system for energy-efficient street lights along the main road outside GC University is proposed.

PVsyst software [10] is used to determine the number of photovoltaic modules, hybrid inverter and storage capacity of hybrid photovoltaic energy generation systems for energy-efficient street lights.

2. Materials and Methods

The hybrid PV system for energy-efficient street lights is designed for the main road outside GC University Faisalabad, with a latitude of 31.394 and longitude of are 73.02. The length of the main road for the installation of energy-efficient street lights is calculated using Google Maps. The total length of a one-way road is 1.40 km (670 m on each side). An energy-efficient street lightning unit with a rated capacity of 30.0 watts is used with a distance of 15.95 m between adjacent poles of street lights. To cover both sides of the road, a total of 84 street light poles are required, with a total daily energy consumption of 20.16 kWh and a monthly energy consumption of 604.8 kWh. The lightning system is estimated to work for 8 h daily. Minimum average monthly peak sun hours are used to design the hybrid photovoltaic power system to ensure that photovoltaic modules can generate enough energy throughout the year. The photovoltaic array and battery bank are then chosen using the PVsyst software. Considering the system capacity, we selected a 400 Watt monocrystalline Canadian solar (CS1U400MS), a 10 KW hybrid Huawei inverter (SUN-10kTL) and a Narada (AcmeG 12V) battery bank from the PVsyst database. Meteorological data was collected from the Meteonorm database, and the PV modules were installed at a 15° tilt angle with 0° Azimuth. The hybrid PV system has 4 parallel strings, and each string has 13 series-connected PV modules. The energy storage system consists of 16 batteries with a nominal capacity of 1600 Ah.

3. Results and Discussion

The simulation results present the total annual energy production and specific energy production, which were calculated to be 26.68 MWh/year and 1283 kWh/kWp/year, respectively. The balance and main results of the hybrid PV system for energy-efficient street lights are shown in

Table 1. Balance and main results of the hybrid PV system.

	GlobHor	DiffHor	TAmb	GlobInc	GlobEff	EArray	EUser	ESolar	EGrid	EFGrid
	kWh/m2	kWh/m2	°C	kWh/m2	kWh/m2	MWh	MWh	MWh	MWh	MWh
Jan	88.3	44.8	11.27	108.3	102.6	1.728	0.67	0.669	0.848	0.001
Feb	106.3	46.8	15.38	125.4	119.2	1.95	0.605	0.605	1.161	0
Mar	147.5	67.8	21.16	163.2	155.1	2.461	0.67	0.67	1.592	0
Apr	165.6	79.1	26.56	172.6	163.9	2.527	0.648	0.648	1.692	0
May	186.5	98.9	32.17	186.8	177.3	2.679	0.67	0.67	1.812	0
June	187	101.5	31.95	184	174.6	2.652	0.648	0.648	1.814	0
Jul	169.8	97.2	30.81	167.5	158.8	2.445	0.67	0.67	1.581	0
Aug	167.2	94.6	30.22	170.5	161.8	2.491	0.67	0.67	1.63	0
Sep	156.8	75.9	28.02	169.2	160.7	2.485	0.648	0.648	1.648	0
Oct	130.9	65.6	24.75	149.6	142.2	2.234	0.67	0.67	1.366	0
Nov	100.3	48.2	18.01	123.1	116.7	1.903	0.648	0.648	1.067	0
Dec	86.6	42	13.15	110	104.2	1.74	0.67	0.67	0.87	0
Year	1693.0	862.3	23.66	1830.3	1737.0	27.296	7.884	7.883	17.08	0.001

. The annual horizontal global radiation at the proposed site is 1693.0 kWh/m^2, and the annual horizontal diffuse irradiation is 862.3 kWh/m² with an average annual ambient temperature of 23.66 °C. Annual effective energy at the output of PV array is 27.296 MWh, the annual energy consumed by street lights is 7.88 MWh and the annual amount of energy injected into the utility grid is 17.080 MWh. In Table 1, we show the maximum energy injected into utility grid in month of June (1.814 MWh) and the minimum energy injected into the utility grid in month of January (0.848 MWh).

The normalized productions per installed kWp of the hybrid PV system are shown in Figure 1a. The photovoltaic array losses due to the collector (Lc) are 1.42 kWh/kWp per day, the losses due to inverter system (Ls) are 0.31 kWh/kWp per day and at the inverter output, the useable energy production (Yf), is 3.29 kWh/kWp per day.

The performance ratio (PR) of the grid-connected hybrid photovoltaic system is shown in Figure 1b. PR is the ratio of the hybrid photovoltaic system final production to the hybrid system reference production. Performance ratio (PR) analysis shows that the highest performance ratio of the hybrid system was 68.2% in December, the lowest performance ratio was 62.7% in May and the annual average PR of a hybrid photovoltaic system is 65.57%.

The loss diagram of the hybrid PV system over the whole year is shown in Figure 2. The loss diagram outlines the major losses of the hybrid photovoltaic system designed for energy-efficient street lights. As shown in Figure 2, the annual global horizontal radiation was 1693 kWh/m², but the effective irradiation on the photovoltaic collector was 1737 kWh/m².

After the conversion of effective irradiation to energy under standard testing conditions of PV modules, the nominal energy of the photovoltaic array was 36.16 MWh and the efficiency of PV modules was 19.42%. Photovoltaic array annual virtual energy at a maximum power point was 27.30 MWh. At the inverter output, the available energy was 26.68 MWh, out of which 77.4% of energy was directly used, and 22.6% of the energy was stored in the battery bank. Finally, 7.88 MWh of the energy was consumed by street lights, and 17.08 MWh of the energy was fed into the utility grid.

4. Conclusions

With the proper selection of electrical components, the photovoltaic powered energy-efficient street lightning system is a feasible option for public lighting. The street light installed on the main road outside GC University Faisalabad is powered by a centralized grid-connected hybrid photovoltaic system. This method avoids the vandalism and damages of the PV system components that occur in single unit installations. PVsyst software was used to design the hybrid centralized photovoltaic system for energy-efficient street lights. The simulation results show the total annual energy production and specific energy production are 26.68 MWh/year and 1283 kWh/kWp/year, respectively. The annual energy consumed by street lights is 7.88 MWh and the annual energy injected into the utility grid is 17.080 MWh. The annual average PR of a hybrid photovoltaic system is 65.57%. The PVSyst simulation produced the best result, with a 2.6% loss of load probability.