Feasibility for the introduction of decentralised combined heat and power plants in agricultural processes. A case study for the heating of algae cultivation ponds

Abstract

The article analyzes the technical and economic feasibility of a biogas-fired Combined heat and power (CHP) plant used in the agricultural sector for the heating of algae cultivation ponds. Specific thresholds are set for typical Key Performance Indicators (KPIs): the cogeneration efficiency, the power-to-heat ratio and the Primary Energy Saving Ratio, which should be satisfied while maximizing the CHP unit’s annual electricity production. A new operation algorithm and a plant’s layout are formulated, with a water heat storage tank and a back-up heat production unit, examined alternatively with and without a biogas production facility, being the article’s main novelties. Alternative sizing scenarios are investigated, optimized versus economic indices. Payback periods close to 5 years are achieved for all investigating scenarios without the biogas production facility, while satisfying all KPIs’ thresholds. The high set-up cost of the biogas production facility affects negatively the investment’s efficiency. The electricity selling price from the CHP unit (higher than 0.12 €/kWh) and the biogas procurement price (lower than 0.046 €/kWhch) constitute critical parameters for the project’s economic viability. The proposed plant exhibits high technical and economic feasibility for similar agricultural applications, fostering the rational use of energy in this sector.