Analysis of a sequential production of electricity, ice and drying of agricultural products by cascading geothermal energy

In this paper, it is presented an analysis for the sequential production of electricity, ice and drying of agricultural products, by the concept of cascade for medium and low temperature geothermal energy. To carry out the analysis, a set of practical assumptions for the integration of technologies operated by cascade method for geothermal energy were defined. The geothermal cascade is composed of three thermal levels, each one operating under different temperatures in decreasing form. Additionally, the thermal cascade is composed at the first level by an Organic Rankine Cycle (ORC) for electricity production. In the second thermal level, by an absorption refrigeration cycle for ice production, and in the third level includes a dehydrator for drying of agricultural products. The agricultural products considered for dehydration are: avocado, green chile and tomato. Once the main assumptions were set, five integration alternatives and five different modes of operation of the system were proposed. The alternatives have different features for the activation of the first thermal level of the cascade, different nominal capacities of electricity production, cold, and quantity of product to be dehydrated. Subsequently, a technical-economic analysis is carried out to obtain the performance and energy characteristics of the different thermal levels of the cascade, different modes of operation, carbon dioxide emissions, cost estimations and indicators of economic viability. The results indicate that the dehydration process improves drastically the economic profits of all alternatives, especially for dehydration of tomato, achieving simple payback periods of around one year, overall energy efficiency of up to 17.84% and greenhouse emissions reduction of 537.7 tonnes of CO2 per year. Concerning the modes of operation, it was determined that the one based on only-electricity production is not desirable due to the worst energy and economic performance.