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Currently, there is widespread interest in developing efficient technologies for harnessing solar energy, both in direct conversion of solar energy into electrical energy and in solar thermal power plants (STPPs). STPPs are sustainable sources of electricity due to the accumulation of heat in a heat carrier, which can be water, molten salt, or oil. The key to increasing the attractiveness of this technology lies in replacing the method of directly generating steam by heating water with solar radiation, with a receiver method using an intermediate heat transfer fluid. The technology of transferring heat obtained from solar radiation through liquid salt (a mixture of potassium nitrate and sodium nitrate, among others) imposes high demands on the pipes of this system that carry the heat transfer fluid, particularly regarding their corrosion resistance and service life. Using pipes made of ordinary steel grades with a special anti-corrosion coating applied to their inner surface can significantly reduce costs and increase the service life of the pipes, as well as the efficiency and reliability of STPPs. The study demonstrates that the method of comprehensive plasma vacuum arc treatment of the inner surface of metal pipes of various configurations, and the application of special coatings, ensures high anti-corrosion protection. For instance, applying a thin-layer coating of austenitic steel with a high chromium content (up to 28%) to samples of martensitic steel pipes resulted in 100% retention of the original sprayed material composition. Thus, the mechanical strength of the base material of the metal pipes in salt STPPs is combined with the high anti-corrosion properties of the applied material. Recommendations are provided for using plasma vacuum arc technology to ensure high operational properties of the circulating pipe systems in salt STPPs. [ABSTRACT FROM AUTHOR]

Charcoal is a dominant energy source in urban areas of Uganda, and increases in retail prices in the past have led to social unrest. This paper assesses the relationship between charcoal and fuel prices to determine whether fuel prices influence the retail price of charcoal. We specify a transportation cost model for charcoal supply and derive the reduced-form equilibrium price function. We estimate an error-correction model for the equilibrium price with monthly data from July 2010 to January 2021 to determine whether there are long-term and/or short-term relationships between the retail and supply prices of charcoal and the prices of diesel and other fuel types. As the price data are integrated of orders zero and one, the autoregressive distributed lag (ARDL) bounds test is used. The results show that there is a long-term relationship (cointegration) between the retail price of charcoal and the supply price of charcoal and the price of kerosene, which is a substitute energy source for the end users. The prices of firewood and diesel are not statistically significant in the model. The long-term equation includes a positive trend, indicating that the retail price of charcoal is increasing more over time than implied by the supply price of charcoal and the price of kerosene. The increasing demand from a growing urban population and the reduced supply from deforestation are trends that will increase the equilibrium price of charcoal, as observed. [ABSTRACT FROM AUTHOR]