Combined cooling heating and power systems in greenhouses. Grassroots and retrofit design


Modern greenhouses are good candidates for combined cooling, heating and power generation (CCHP) systems. An analytical framework to assess the affordability of such systems for two different problems, is proposed; (a) the grassroots problem, i.e. the CCHP system is designed along with the greenhouse, and, (b) the retrofit problem, i.e. the addition of a CHP unit to an existing greenhouse. As a case study, the analysis is applied in three locations of Greece (North, Central, South) with different meteorological conditions, for two traditional products (tomato, cucumber). The results indicate that cogeneration is a cost-effective solution improving the economic and energetic efficiency of the facility. Furthermore, with the use of active cooling, the operating period of the greenhouse is increased, which significantly improves the cashflow. Product cultivation parameters and climatic conditions affect to a significant degree the overall performance. It is proved that the combined use of a CCHP and a conventional gas boiler for heating, is more profitable for tomato cultivation, achieving ROI 23%, 28%, and 27%, in North, Central and South Greece, respectively. The sensitivity of the investment’s feasibility is quantified in regards to energy prices, and pricing policies, which is one of the most important factors.