Techno-Economic Analysis for the Role of Single End Energy User in Mitigating GHG Emission

Background End energy user relies on fossil fuel-based national grid to meet their energy demand; hence, indirectly contributing towards greenhouse gases (GHG) emission and causing climate change. This study aims to investigate the minute role of a single, end energy user in GHG mitigation by shifting to the green renewable energy source, photovoltaics (PV) through its techno-economic analysis. Method For the study impact, NASA Meteorological Data is used to select an ideal single energy user equipped with 10 kW PV system based on annual- average daily solar radiations and temperature through MATLAB/Simulink, among eleven populous cities of Pakistan. Helioscope software is used to select tilt and azimuthal angle to expose PV surface for most of the solar radiations. Afterwards, RETScreen software is used for cost, nancial and GHG analysis. and energy independency main at the same time.


Introduction
Energy serves as the backbone of the modern era, while developing countries face severe energy shortages [1]. On the contrary, across the globe, there is another movement with growing concern over energy production through conventional energy resources in context of global climate change [2] like, in Pakistan, a major energy share is of conventional energy resources [3][4]. Moreover, research analysis suggests increment of 2.9% and 2.0% in energy consumptions and carbon emissions, respectively, in 2018 [5]. Conventional energy production involves emissions of nitrous oxide (N 2 O), methane (CH 4 ) and water vapours (H 2 O) apart from carbon dioxide (CO 2 ) emissions. These greenhouse gases (GHG) blocks the re-emitted radiation from the Earth initially received by Sun, trapping the energy, hence raising the Earth temperature, cause of climate change [6][7]. In response, the world is implementing the solutions to reduce this cause without any change in demand and supply i.e. electric grids transformation from conventional energy resources to green renewable energy resources has moved due to environmental concerns [8]. Global efforts include Paris Climate Accord [9], Kyoto protocol [10] and European Union targets-2020, 2030 & 2050 [11][12][13] as its important conventions and energy/emission targets. This serves as the cause of investigation and aim of this paper to present the PV system feasibility for greenhouse gases mitigation at a single, end energy user. Moreover, careful selection of the best location for 10 kW PV system installation among eleven densely populated cities of Pakistan through Simulink based on daily solar radiation and ambient temperature, data retrieved from NASA Meteorological Data. In addition, the selection of optimal PV plant installation parameters to avoid e ciency drop through Helioscope software. Finally, RETScreen is used to analyze the degree of relief from high electricity pricing to end energy user in the project's 25 life-year span. For this purpose, cost analysis and nancial analysis is carried out. Moreover, user shift from main grid (MG) to PV system for its energy demand relaxes MG and supports GHG emission mitigation at his individual level. Proposed system is re ected in the form of the ow diagram in Fig. 1.
In south Asia, a developing country Pakistan is facing energy shortage problems since its birth, and in 2017 from 5 giga watt to 7 giga watt [14]. Pakistan energy sector is still burdened with circular debts [15]. The world is moving to green energy resources while Pakistan's major share of energy is from conventional energy resources [3][4] and over these conventional energy resources which involves GHG emissions and climatic concerns are discussed in literature as her energy analysis with their role in CO 2 emission [16].
However, because of Pakistan's unique geographical coordinates and seasonal pattern variations, it is ideal for green renewable energy production such as solar PVs and wind power plants. Pakistan's mean solar irradiation is 5-7kWh/m2 in a day and on the average sun shines for 8-10 hours/day for over and above 300 days in a year [17][18]. According to a careful estimation by Alternative Energy Development Board (AEDB) Pakistan contains 2900 GW solar potential [19]. This offers Pakistan with a tremendous possible solution to address its energy issues by green renewable energy resources in a timely manner to address its two major challenges at the same time. Conventional energy resources are not only expensive, but uctuations in oil prices burden the country's imports. With the increase in population, energy consumption has experienced an increase in the household share of [35][36][37][38][39][40][41][42][43][44][45][46].5% in last two decades, and the expected increase in energy demand will be 113 GW by 2030 with 8% annual growth rate [3,20,21]. Across the globe, developing countries and developed countries have initiated incentives-based support programs for faster penetration of green renewable energy sources i.e. distributed solar photovoltaic (PV) generation. Moreover, net-metering has been successfully implemented by Denmark, Belgium, Australia, USA, China, Brazil, Bangladesh, India, etc., for rapid market expansion of solar PVs [20]. In Pakistan, grid-tied residential PV generation systems installations are very slow; despite higher solar-irradiation, enactment of Net-metering by government and a signi cant decrease in solar PV module prices [20]. Renewable based energy generation will not only guarantee uninterrupted power supply but will also help to reduce the GHG emissions in broader ways.
The quantity of electricity produced at any location depends on the largest extent on the solar irradiation on the location [7]. However, the output of PV module linearly depends upon temperature as well; an increase in temperature causes e ciency loss, hence a decrease in PV output [22]. Literature suggests that the grid-connected solar PV systems are more feasible, reliable and economical than standalone systems [23]. And for the deployment of solar power plants, there is a need for techno-economic and environmental feasibility analysis, prior to making investment decisions [24]. For this purpose, a relatively easy and user-friendly software package to analyse various types of Renewable-energy and Energy-e cient Technologies inculcating PV systems, RETScreen is used. It is developed by Canada for multiple analysis such as energy, feasibility, emission, nancial and risk assessment, [25]. In literature, multiple studies are considered in RETScreen which provided valuable information of environmental assessment, emission assessment, feasibility assessment, technical assessment, economic assessment comprising of cost and nancial assessments of mega projects in multiple countries across the globe. For instance, Nigeria's 100 MW proposed PV system is assessed in country's twenty-ve location for nancial (pro t) assessment and its relative GHG emissions mitigation effectiveness [7], Bangladesh's 1 MW grid-connected PV system's nancial viability in fourteen regions of the country [26], Chile's 30 MW PV plant's nancial/sensitivity assessment at twenty-two locations of the country [27] Iran's 100 kW grid tied-PV system for economic assessment [28] and Pakistan's 10 MW PV system economic viability at eight sites of the country [3]. Literature provides an assessment of multiple regions of land-based on RETScreen. Table 1. compares the proposed approach with related PV system studies, speci cally carried out in RETScreen software. Literature is majorly focused on megawatt projects and minute role of single, end energy user, which is fed from conventional energy-based national grid is overlooked.

Literature Analysis and Proposed System Novelty
In literature, the best location for the installation of PV system is either decided by only a single parameter; average daily solar radiation or after all locations detail analysis. Proposed study uses relation of annual average daily solar radiation and temperature with PV system output in MATLAB/Simulink software for best location selection for detail analysis. Selection of tilt and azimuthal angle in literature is either selected to a xed value or locational latitude but proposed study used advance solar design software, Helioscope for best-t tilt and azimuthal angles. All analysis is carried out in RETScreen software.

Methodology
PV system feasibility and emission assessment at end energy user, a small part of the energy paradigm are necessary. End energy user consumes the energy but in case of PV system equipped home, trades surplus energy to the main grid. Surplus energy supplied by the user is not visible/monitored by the national control centre. However, it provides relaxation to the national grid in peak shaving, grid stabilization, lessening the dependence on conventional sources and importantly, end energy user small but signi cant role against environmental concerns. Therefore, the proposed PV system is on-grid system means no backup battery system involves. PV systems running cost as well as emission (CO 2 and H 2 O etc.) are zero.

Location Selection
Pakistan's eleven geographical sites; Peshawar, Multi Gardens (Wah), Multan, Lahore, Rawalpindi, Sargodha, Faisalabad, Bahawalpur, Bannu, D.I. Khan and Jhang, geographical data is provided by RETScreen, provided in Table 2. RETScreen utilizes meteorological data for any speci c location from its meteorological data inventory provided by NASA [25]. MATLAB/Simulink is used for best location selection at energy user based on two important parameters, affecting the output most; daily solar radiation and ambient air temperature [7,22] Simulink PV module parameters to verify the maximum possible power at each of eleven locations through daily solar radiation and temperature is provided in Table 3. A DC load is connected at PV output for the measurement of possible power output, a ramp load starting from 0 to 21.1. Watts in the presence of 4.02 kWh/m 2 daily solar radiation with 21.6 Celsius air temperature. Based on Simulink results, Multi-Gardens location is best for detail analysis of 10 kW PV system for single end energy user role in GHG mitigations.

Parameters Selection
NASA's complete meteorological data for proposed 10 kW PV system at Multi Gardens is provided in Table 4. It provides valuable data of multiple key factors like daily solar radiation-horizontal, air and Earth temperature, relative humidity, wind speed and atmospheric pressure over a whole year. Figure 2. re ects values of daily solar radiation-horizontal surface and air temperature factors at 5.19 kWh/m 2 /d and 22.8 Celsius for a whole year, respectively. These two factors play pivotal roles in PV systems output [32]. For a realistic assessment of the proposed 10 kW PV system at Multi Gardens, RETScreen must be provided with real project values, and these values were provided by technical workers working in the same energy domain. Multi-Gardens location has considerable dust pollution due to its vicinity to crushing machines, which can signi cantly affect PV system output. A value of 12% was chosen for PV array losses as miscellaneous losses. Since, azimuthal and tilt angle ensures the maximum extraction of energy from solar radiations, Helioscope, an advanced solar design software is utilized. Helioscope is used by the solar companies for the designing, engineering and selling solar arrays [33]. Since grid operates on 50 Hz alternating current, an inverter is required to invert DC to AC, which has losses involve in it as well. A modern, e cient inverter is considered with 98% e ciency. Plant data, PV system electrical speci cations and main inverter data is provided in Table 5, Table 6 and Table 7.

Cost Analysis
Capital cost analysis is required for the user in order to match it with his purchasing power. This cost analysis provides initial detail investment plan of the proposed 10 kW system at the best location, Multi Gardens. Cost analysis provides a complete knowledge of investment divided into the feasibility study, engineering cost, PV system cost, inverter costs and miscellaneous costs, which are 93$, 360$, 4924$ and 1959$, respectively. Table 8. Provides data for proposed 10 kW PV system after market survey of PV system and from same eld experts. RETScreen offers the right place to carry out either detail or short cost analysis. RETScreen detail analysis is used for this cost study. Feasibility study gives insights about site investigation, resource assessment, environmental assessment, detail cost estimate and report preparation. Engineering study about mechanical design, electrical design and civil structural support design. These are soft study. On the contrary, power system study asks input regarding photovoltaic-10 kW cost and its distribution box for net metering.
Finally, inverter and miscellaneous analysis are about inverter cost, installation cost, training and commissioning. These are broadly referred to as hardware study [34]. Table V. Shows PV system and inverter costs accounts more than 85% of capital cost for 10 kW proposed system at a speci ed location.

Financial Analysis:
Financial analysis involves costs like capital cost, electricity export rate, electricity export escalation rate, in ation rate, project life and debt ratio etc. RETScreen on these inputs generates a detail nancial analysis sheet for interested end energy user.
Government of Pakistan offers income tax and premium tariff exemption to support renewable projects [35], so the nancial study of the proposed PV system includes no income tax and premium tariff. Considering electricity export rate of 0.055$/kWh [36] for 25 years life span for the project. And electricity escalation rate is considered 6% per annum following its preceding electricity growth rate/pattern in Pakistan. Debt ratio range is suggested by RETScreen, but 50% debt ratio was utilized for nancial analysis for a proposed 10 kW PV system project.
Discount rate suggested by RETScreen for North America projects was used to select the discount rate for this project, and 9% was appropriate to value. Table 9. provides input value for the nancial assessment of the proposed project. Operation and maintenance cost is considered low due to no moving parts in the system; however, dealing with dust at the proposed project location is important to keep its e ciency maintained to an acceptable value. O&M cost for xed PV system was estimated to 460$ per year. These values and rest of values were carefully chosen after communication with workers in relevant elds.
Project total cost is 7337$, excluding O&M costs. Electricity exported to the grid is 16,832 kWh which earned 1,683$ at the electricity export rate of 0.055 kWh. The annual income/cost and cumulative net present cost of the project is illustrated in Figure. 3 (a) and (b), respectively. This project is nancially good as the initial cost is recovered in about ve years and investor/end energy users start earning in the following years.

Emission Analysis:
RETScreen provides emission analysis for green renewable energy resources and their equivalent GHG emission mitigation potential.
Since a number of gases (CO 2 , H 2 O, NO x etc.) are released while burning, however, RETScreen provides an equivalent annual amount of CO 2 to total emissions. It is processed by translating emission gases into CO 2 based on their global warming potential [6]. Table 10. provides 10 kW PV system net annual emission drops through its equivalent cases from the environmental point of view.
This proposed system is effective since it is equivalent to 1.3 cars & light trucks not used, 2958.7 litres of gasoline not consumed, 16 barrels of crude oil not consumed, 6.9 people reducing energy use by 20%, 1.6 acres of forest absorbing carbon, 0.6 hectares of forest absorbing carbon that could be emitted in case of conventional energy plants and nally equivalent to 2.4 tons of waste recycled. It is important to mention this data varies from location to location even if 10 kW PV system with same speci cations is considered as elaborated in Tables 5, 6 and 7 because daily solar radiation and air temperature varies location to location. RETScreen suggests annual GHG emissions reduction due to 10 kW PV system at speci ed location of Multi Gardens is equivalent to roughly 6.9 tons of CO2 with equivalent annual electricity exported to the grid scales to 16,832 kWh. Acres of forest absorbing carbon 1.6 Hectares of forest absorbing carbon 0.6 Tons of waste recycled 2.4 Annual GHG emissions reduction 6.9 tCO 2 Annual electricity exported to the grid 16,832 kWh

GHG Mitigation Effectiveness in Pakistan's Scenario
Pakistan's three provinces; Sindh [37], Punjab [38] and Baluchistan [39] literature suggests that four kWh of energy can be produced per litre from a 20-kW diesel generator. For the proposed PV system, 16,832 kWh per annum energy is produced through solar radiations in Multi Gardens, which is equivalent to the consumption of 4,208 litres of oil consumption or saving the same amount of oil. For the sake of simplicity, this project in its lifetime will avoid burning of 105,200 litres of oil on a single, end energy user with 10 kW PV installed system. This project can signi cantly reduce GHG emissions in its lifetime at the user end.

Conclusion
A single, end energy user importing energy from fossil fuel such as coal, oil and gas, based main grid to meet its energy demands, is contributing towards GHG emissions, indirectly. This end energy user is invisible to the main grid and shift in its energy source can change the dynamics of the power system role in GHG emissions. The aim of this study was to investigate the pivotal role of single, end energy user in GHG mitigation through its techno-economic analysis using tools like NASA Meteorological Data, MATLAB/Simulink, Helioscope and RETScreen software. This study utilized the real data from energy experts for detail analysis of single user among Pakistan's eleven populous cities. The 10 kW PV system in its 25 years lifetime recovered its 7337$ capital cost in about ve years and earned user 1683$ per annum by generating 16,832 kWh energy per annum. The system reduced GHG emissions equivalent to 2.4 tonnes of waste recycled, 16 barrels of crude oil not consumed, and 2958.7 litres of gasoline not consumed. Future work includes the detailed study of electric vehicles charging stations based on PV system to mitigate GHG emissions in the transport sector as well.

Declarations
Ethical Approval and Consent to participate: Not Applicable Consent for publication: We, authors allow publisher to publish our work.
Availability of supporting data NASA Meterological Data is provided by RETScreen Software. Tilt and azimuthal angle data is provided by Helioscope software.
Competing interests: Authors declare no competing interests Daily solar radiation and air temperature over a whole year at Multi Gardens.

Figure 3
Proposed 10kW system a) Annual income/cost, b) Cumulative net present value