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Concerns about greenhouse gas emissions and global warming have raised the need to use renewable sources. The expansion of the use of renewable resources has a deep relationship with energy consumption, its price, and economic growth. Therefore, based on the threshold regression approach, this study evaluates the effect of price and energy consumption on renewable energy development in Iran's different economic growth regimes. In this regard, by collecting economic data in Iran over 30 years, using STATA software, and forming a threshold regression model, the asymmetric effect of energy prices on energy consumption is investigated. The results showed a threshold for regression equal to 7.28% in the annual GDP growth rate data. According to the threshold value, economic analysis is divided into two parts: economic growth below the threshold and economic growth above the threshold. The results show a negative and significant relationship between the energy price index and the share of renewable energy in Iran during high economic growth. The reason for this is related to the unstable and intermittent growth of the economy, unprincipled management of resources due to increased revenues due to rising energy prices, energy subsidies, and the private sector's reluctance to invest in cheap renewable energy fossil fuels.

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Policy‐making in improving the quality of the environment and social welfare and increasing the rate of economic growth to achieve sustainable development has been considered by policymakers in recent years. Punitive policies such as taxes on fossil energy consumption and incentive policies such as subsidies for investment in research and development are among the policies used to achieve sustainable development goals. In this study, using a computable general equilibrium model, two scenarios of subsidy to investment in research and development and subsidy with the taxation of fossil fuels, to double the ratio of investment in research and development GDP have been considered. First, the subsidy rate required to invest in research and development to achieve this goal is determined, and then, the economic, welfare, and environmental effects of the policies implemented are examined. This study shows that in the first scenario, the subsidy rate required to invest in research and development to achieve this goal is 10.74% and in the second scenario is 10.21%. Meanwhile, the required tax rate in the second scenario is estimated at 2.5% of fossil energy consumption. The results show that both the fossil energy tax policy and the research and development subsidy policy are able to reduce energy consumption, air pollution, and social welfare. The reduction in welfare in both scenarios is regardless of the social benefits of reducing greenhouse gas emissions.

Unacceptable environmental pollution from the fossil fuel energy sources is increasing the demands on green energy concept and developing alternative solutions and has encouraged the international community to employ clean and renewable energy sources such as wind energy. Among different types of wind turbines, Savonius vertical axis in spite of its fascinating advantages including low rotational speed and noise, self-start capability, and independency relative to wind direction has gained less attention in industry due to low energy conversion efficiency. This paper investigates the insertion of a one-way opening valve on the three-blade Savonius wind turbine to reduce generated negative torque on convex side of the blade. Position, size, opening direction, and the opening angle limitation are defined as design parameters and 17 different scenarios in five main categories based on these parameters are modeled, simulated, and analyzed. Concluding, unlimited counter-clockwise large valve in position III exhibits 14% improvement in performance, which is promising.