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One of the necessities of human beings in this century is the potable water supply. This supply has more environmental benefits if the potable water is supplied by renewable energy resources. In this paper, a combination of combined cooling and power system (Goswami cycle), with the reverse osmosis and sodium hypochlorite plant powered by geothermal energy resources is proposed. The products of this system are electrical and cooling energy, potable water, hydrogen and salt. To investigate all of the system aspects, energy, exergy, economic, exergoenvironmental, and environmental analyses are performed. In environmental analysis, the social costs of air pollution are considered. It means that for the same amount of system electrical power produced by non-renewable energy resource power generation systems, the produced air pollution gases and their costs considering the social cost of air pollution are quantified. In this regard, four scenarios are defined. Results show this multi-generation system produces 1.751 GJ/year electrical energy, 1.04 GJ/year cooling energy, 18106.8 m 3 /year potable water, 7.396 Ton/year hydrogen, and 3.838 Ton/year salt throughout a year. The system energy and exergy efficiencies are equal to 12.25%, and 19.6%. The payback period time of this system is equal to 2.7 years.

This review showcases a comprehensive analysis of studies that highlight the different conversion procedures attempted across the globe. The resources of biogas production along with treatment methods are presented. The effect of different governing parameters like feedstock types, pretreatment approaches, process development, and yield to enhance the biogas productivity is highlighted. Biogas applications, for example, in heating, electricity production, and transportation with their global share based on national and international statistics are emphasized. Reviewing the world research progress in the past 10 years shows an increase of ~ 90% in biogas industry (120 GW in 2019 compared to 65 GW in 2010). Europe (e.g., in 2017) contributed to over 70% of the world biogas generation representing 64 TWh. Finally, different regulations that manage the biogas market are presented. Management of biogas market includes the processes of exploration, production, treatment, and environmental impact assessment, till the marketing and safe disposal of wastes associated with biogas handling. A brief overview of some safety rules and proposed policy based on the world regulations is provided. The effect of these regulations and policies on marketing and promoting biogas is highlighted for different countries. The results from such studies show that Europe has the highest promotion rate, while nowadays in China and India the consumption rate is maximum as a result of applying up-to-date policies and procedures.

Due to the harmful effects and depletion of non-renewable energy resources, the major concerns are focused on using renewable energy resources. Among them, the geothermal energy has a high potential in volcano regions such as the Middle East. The optimization of an organic Rankine cycle with a geothermal heat source is investigated based on a genetic algorithm having two stages. In the first stage, the optimal variables are the depth of the well and the extraction flow rate of the geothermal fluid mass. The optimal value of the depth of the well, extraction mass flow rate, and the geothermal fluid temperature is found to be 2100 m, 15 kg/s, and 150 °C. In the second stage, the efficiency and output power of the power plant are optimized. To achieve maximum output power as well as cycle efficiency, the optimization variable is the maximum organic fluid pressure in the high-temperature heat exchanger. The optimum values of energy efficiency and cycle power production are equal to 0.433 MW and 14.1%, respectively.

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