Concerns about greenhouse gas emissions from fossil fuels have made the use of renewable sources the world's most important energy challenge. Among renewable energies, geothermal energy has a special place due to its sustainable resources and shallow environmental impacts. These energy sources are classified as low‐grade thermal energy sources, so they cannot independently provide a high amount of thermal energy. Therefore, extensive studies have been conducted on practical methods of using geothermal energy for multigeneration productions. Studies on geothermal energy‐based systems to supply energy to various systems such as chillers, electrolyzers, turbines, and desalination units are reviewed in this study. As the methods, scenarios, and practical possibilities of multigenerational system (MGS) are limited, in this study, while expressing the limitations and problems of these systems, the most critical issues raised in this issue are examined and analyzed, and compatibility, products, Levelized cost of energy, energy and exergy efficiencies, and technical issues are summarized. Also, due to the limitations of geothermal energy sources in recent studies, their combination with other renewable energy sources has been evaluated. Therefore, the classification of studies conducted to combine renewable energy sources with the geothermal system to achieve multigeneration productions is thrown in the last part of this study. The results of the studies show that the combination of geothermal energy with other renewable energy sources is used in 90% of cases to provide heat and cold load and in 10% of cases to generate electrical power. These systems also improve energy and exergy efficiency and economic viability by increasing stability.

The environmental taxes, such as carbon tax, also affect other economic variables in a different way in addition to the main goal of politicians. The carbon tax aims to reduce energy consumption and pollutant emissions, while it can also reduce labor tax and labor costs which are incentives to create new jobs. It is necessary to evaluate the carbon taxation policy in Iran due to the special circumstances of the budget deficit mainly caused by the decline of exports and oil revenues. The present study is based on a general equilibrium model in the form of a nonlinear equations system. The model has been calibrated for the 2017 reference year using the data table adopted from Iran's economy. It has been shown that if the carbon tax revenue is employed to decrease the labor income tax, the environmental quality will be improved by reducing pollutant emissions on the one hand, and it will lead to positive effects on the welfare and employment on the other hand. In the present paper, the effect of applying this tax on two policies with redistribution (compensation) and without redistribution (no compensation) of income tax among the households is examined. Maximum, minimum, and optimal values of pollutant emissions reduction under the influence of carbon tax policies were calculated in both scenarios. The simulation results show that the taxation without redistribution of tax revenues decreases the welfare and household's actual consumed budget by 6.2%, but in policy with compensation of tax revenue, these indices will increase by 0.8%. The gross domestic product (GDP) decreases by about 1.7% and 2.1% in both policies, respectively, while the consumer price index (CPI) in both scenarios will increase by about 6.4% and 8%, respectively. According to this research findings, carbon taxation with the redistribution of revenue is a suitable policy to reduce greenhouse gas emissions and adhere to international commitments at the same time.

With the development of different generations of solar cell (photovoltaic) technologies, extensive research has been conducted to evaluate their performances, applications, and cost benefits. Despite these technologies being known as green technologies compared with fossil fuels, however, their environmental problems and damages have not been assessed and compared systematically in their whole life cycle. In this study, the environmental effects of different solar cell generations are assessed and compared using the life cycle assessment approach. Environmentally speaking, the results obtained from the software indicate that the first (polycrystalline) and third (transparent Perovskite) generation panels cause the greatest (1.43 × E⁻⁶ Daly) and least (4.56 × E⁻⁷ Daly) damage to human health, respectively. In addition, these two generations of photovoltaic panels have the most significant and least negative influence on the ecosystem with 2.18 × E⁻⁸ and 7.05 × E⁻¹⁰ Species.Yr, respectively. Regarding the environmental effect of damage to the resources, the third and second (cadmium telluride) panels have the least damage with 0.027 USD2013 and 0.0184 USD2013, respectively. The most negative midpoint effect is associated with the marine ecotoxicity of 0.101 kg 1.4‐DCB by the second generation panels. Concerning global warming as the most critical consequence, all three panels also severely impact increasing the global warming index by 399, 164, and 134 (gCO₂ eq), respectively. Based on perovskite technologies that are being rapidly evolved with extensive applications, replacing this technology with the current generations is expected due to its less environmental impacts.

Off‐grid renewable energy systems are a solution for power generation in areas where access to the grid is not possible or cost‐effective; in particular, low population rural areas located far away from grid lines or in rugged terrains. Furthermore, over‐reliance on fossil fuels for supplying global energy demand has led to the depletion of nonrenewable resources and environmental issues. This paper presents a feasibility assessment of an off‐grid hybrid renewable energy system for a remote rural area in Kohgiluye and Boyer‐Ahmad Province in Iran. Regarding the available energy resources in the region, a photovoltaic (PV)‐biomass energy system is considered. HOMER Pro software is utilized to find the optimized sizing of the PV‐biomass system to fulfill this load demand. The objective function in this optimization is the system's total net present cost. Due to the rapid fluctuation of economic factors in the country, several rates of inflation and discount rate are considered to investigate their influence on the costs of the system. The optimization result for the current inflation rate of 40% and the discount rate of 18% in the country proposes a hybrid energy system consisting of a 3 kW biogas‐fueled generator, 4.74 kW PV, 10 kWh battery, and 2.07 kW converter to meet the 2.64 kW peak load and 14.53 kWh/day consumption of the community. The total net present cost and cost of energy are $93,057 and 0.0933 $/kWh, respectively. Finally, the environmental assessment of the proposed hybrid system shows an annual CO₂ emission of 2.95 kg, which means 99.9% CO₂ emissions mitigation compared to a conventional coal‐based electrical plant.