Financial Analysis of Low-Temperature Solar Thermal Energy Storage Systems to Supply Hot Water and Heating for Rural Colombian Households

In order to mitigate the effects of climate change, contribute to energy autarky and improve the quality of life of the population, Colombia has adopted the energy transition to renewable energy as a state policy. In this context, the use of solar thermal energy, which is abundant in the tropical zone, should be considered as one of the alternatives to be prioritised. A solar thermal energy storage system (STESS) has been developed for the supply of hot water and heating in paramo areas. The system is capable of storing energy in the form of latent heat using a renewable phase change material (PCM). The PCM reaches a maximum temperature of 70° C, allowing enough energy to be stored to take several hot showers and maintain a comfortable temperature in a room. This paper evaluates the performance of the developed STESS from a financial point of view, analysing the associated capital and operational costs. It is also compared with alternative technologies available in the area based on electric heaters and propane gas heaters. The operating cost analysis concludes that the performance of the STESS allows savings of variable operation cost up to 90 % compared to electric energy-based systems. These results become even more relevant considering that many of these areas are not connected to the national electricity grid and almost none of them have a reliable supply of propane gas. Regarding capital costs, although STESS requires an initial investment up to 20 times the value of alternative systems, its long lifetime, low operating costs and reliability make it an attractive alternative in this scenario.