Temperature control of nutrient solution in floating system cultivation

Water temperature plays a relevant role in the growth and development of plants in floating system cultivation, thus affecting both productivity and quality. A model of a greenhouse which hosts ponds is described, in order to highlight the components of the energy balance and estimate the refrigerating power required to maintain the nutrient solution within acceptable limits. A water cooling plant powered by an electrical water chiller is considered. Results from this model include the prediction of the air temperature and nutrient solution temperature in transient conditions during the growth periods, together with the electrical energy absorption and related operating costs. After a validation by comparison with measured data, simulations are performed at six climate conditions, from typical warm Mediterranean to cold continental conditions. Important energy savings can be achieved by maintaining the water covered by boards during harvesting at the end of the growing cycle. Furthermore, the water cooling system can be designed to be reversible and perform air heating in winter time, with the aim of extending the growing period. The amount of heating power required by the heating system in winter time is thus estimated.