Among the types of renewable energy, solar energy has received more attention due to its ability to be directly converted into electricity and heat, ease of use, possibility of storage, and its endless nature. Therefore, in recent decades, a lot of research has been done on solar energy systems in Iran and the world. Makran region, located in the southeast of Iran, has one of the greatest potentials of using solar energy among other regions of Iran. In this research, a one-megawatt power plant in Chabahar city, located in Sistan and Baluchistan province, on the southeast coast of Iran, has been modeled using RETScreen software and issues such as return on investment, internal rate of return (IRR), net present value (NPV) and carbon dioxide emissions. levels have been investigated. Finally, according to the considered conditions of the investment return period, according to the guaranteed purchase contract with a tender price of 73 dollars, the amount of carbon dioxide production in the region will be reduced for about 3 years and about 1009 tons per year.

This study presents a RETScreen based economic analysis of switching from grid electricity to solar photovoltaic (PV) system for a medium sized residential building located in Ado ekiti, Nigeria. The building has an existing 2kW solar PV system in place. Input parameters in RETScreen included the solar energy resources, cost and financial data. Two cases were evaluated using the maximum unit price of electricity for a forecasted 10-year period as the cost of grid purchase. The first case considered 24hr availability of electricity from the grid and results show that the PV system has an equity payback period of 9. 4 years with an internal rate of return (IRR) of 15. 3%. The second case took into consideration the epileptic nature of grid electricity in Nigeria. This condition increased the equity payback period to 16 years and 7% IRR. This shows that a solar PV is more economically rewarding in location with reliable grid electricity and relatively cheap cost of electricity.

Energy is one of the most critical factors in economic development, but achieving sustainable development is impossible without environmental protection and improving economic conditions. If a country is dependent on energy, any structural reform policies to reduce energy consumption may reduce economic growth. Saving energy consumption and the development and application of alternative technologies, especially renewable energy, has a significant role in controlling and reducing the consumption of fossil energy carriers and, consequently, reducing the emission of environmental pollutants and achieving sustainable development. This article deals with the feasibility of constructing renewable energy power plants in Khoy city. First, using RETSCREEN software, the economic and environmental conditions of the construction of renewable energy power plants in Khoy city are examined. Using PVSYST software, the requirements for constructing solar power plants are discussed in a specialized way. In this article, the inflation rate is 12%, and the interest rate is 4%. The construction of solar and geothermal power plants in this city can be prioritized based on the results. The solar power plant has a production capacity of 30 MW. 212194 meters of land, and a capital of 40 million dollars are needed to construct this solar power plant. The payback period of this project in Khoy city is estimated at 25 years.

The current study investigated the feasibility of renewable energy harvesting to meet the energy need of a dairy farm in Shahroud, Iran. Therefore, considering the available renewable resources including solar, wind, and biomass in the site and the electrical demand of the farm, the techno-economic and environmental analyses were carried out. By using Homer software, the optimized system was selected. It was shown that although there was wind potential within the farm site, the most economical system would be a system consisting of a 100 kW biomass power plant and a 169 kW PV plant. Furthermore, by using RETScreen software, the economic and environmental analyses for the selected system were carried out. The simple and equity paybacks were 5. 8 and 4. 2 years for the proposed system, which confirmed the economic feasibility of the proposed system. Moreover, the gross annual GHG emission would be reduced by 91. 5 %. The technoeconomic and environmental analyses conducted in the current paper confirmed that the proposed system could be easily extended for other dairy farms, which resulted in a significant increase in the energy ratio of the dairy farms.

The goal of this study is to evaluate a gas and solar power plants (photovoltaic) grid-connected in Ahvaz city, Iran. The results showed that the solar power plant has more economic advantages than gas power plants. A review of the scenarios concerning the replacement of the guaranteed purchase price of the solar power plant showed that even a 50% reduction in the guaranteed power purchase price did not make the project non-economic. In this case, a big value of NPV (about 68 billion rials) has been lost but the return on investment (22. 8%) would be reasonable. Of course, it should be noted that this is the most pessimistic case when using the project. Comparison on capital returns for a solar power plant, which is 30% of its guaranteed purchase price (4. 2 years) was reduced, and the same factor for the gas plant (2. 5 years in Table 5) gives us the choice of the solar power plant. The results of sensitivity analysis showed that the electricty price is more sesitive that other two economic factors. Using of solar power plants because of the microstats crisis in recent years in this region, can help to implement this method and increase the benefits of this environmental technique.

In this study, the economic analysis of the architectural part of the building, the use of both the solar thermal and solar electric systems in a poultry farm were discussed. In this economic analysis, the implementation of architectural solutions as well as the utilization of the solar thermal system considering the global gas price and the current gas rates in the country and finally the use of solar electric system with different subsidies were analyzed. Economic analysis was conducted using RETSCREEN software. The results showed that the internal rate of return (IRR) for the architectural solutions of using double-glazed windows and wall insulation, considering the global gas price, was estimated as 53.1% and, the investment return, taking into account the inflation and discount rates, was equal to 2.6 years, which is the break-even point of investing in this solution. Utilizing the solar thermal system and without considering the cost of the underfloor heating system, the IRR value is equal to 34.1%, and considering the cost of the underfloor heating system, the IRR value is equal to 27.9%, which is economic in terms of these solutions. This option proves to be cost-effective. When employing the solar electric system with an IRR of 4.4%, this solution proves uneconomical under all circumstances due to the IRR falling below the bank rate and yielding a negative Net Present Value (NPV). However, when considering a 50% government subsidy and a 1.5-fold increase in the electricity purchase tariff for the solar electric system, this solution approaches the threshold of economic viability

Sustainable Development Goal 13 is an activity committed with the intention of stabilizing greenhouse gas (GHG) levels in the environment to stop potentially harmful human meddling with the climate system. GHG are released into the environment from various non-renewable energy sources of power generation and many industries that cause extensive damage to the environment. Some countries have begun to implement various pollution prevention strategies, such as power generation from renewable energy sources, which emit no greenhouse gases (GHG) or CO2. This study focuses on an analysis of GHG emission reduction along with the financial feasibility of a grid-connected 100MW PV solar system. This study uses RETScreen software to evaluate the GHG emissions reduction analysis as well as a financial analysis of the system. The annual electricity supplied to the local grid of the proposed PV power plant is 137,481MWh. The cost of reducing CO2 emissions has a positive impact on the overall cumulative cash flow of the proposed system.

According to energy economists, increasing efficiency and utilizing renewable energy sources, especially solar energy, is the most effective way to achieve sustainable development goals, provide economic benefits, increase energy security and reduce environmental pollution. In the present study, technical and economic evaluation of the role of investment in the construction of solar power plants (photovoltaics) on sustainable development of Boroujerd city was used using engineering economics method and economic analysis method and RETScreen software. The results show that the assumed photovoltaic power plant has an economic justification with an assumed megawatt period with a return on investment of 4. 3 years, an internal rate of return of 28. 1%, a net present value of 645. 24 billion rials and a profit-to-cost ratio of 9. 8. This power plant will produce 2197 MWh of electricity per year (about 0. 39% of the total electricity required by the city) and 257 similar power plants are needed to provide the total electricity consumption of Boroujerd city. With the construction of this power plant, the annual emission of greenhouse gases equal to 365. 2 barrels of crude oil has not been reduced. Also, this one-megawatt power plant saves 8. 5 billion rials per year in fossil fuel, water and greenhouse gas emissions. This amount is equal to 11. 7% of the initial construction costs of this power plant, which in addition to selling electricity generated, has positive social effects on society. With the approximate extension of this power plant to a power plant that provides the total consumption of Boroujerd city, 21955. 65 billion Rials will be saved in the above cases every year. It is proposed that the government and the Ministry of Energy support the existing solar potentials in the city by providing the necessary funds and facilities for the construction of solar power plants (photovoltaics) with a capacity of one megawatt. Also, by doing this, a lot of savings will be made in the consumption of fossil energy resources, water and greenhouse gas emissions, and the interests of future generations of sustainable energy conservation and development in this city will be realized.