Evaluation of the feasibility of alternative energy sources for greenhouse heating

Four greenhouse heating systems were compared by computer simulation in seven European locations: a conventional fossil-fuel system and three hybrid systems, in which part of the heating demand was covered by solar collectors, a heat pump and a cogeneration system, respectively. Flat solar collectors were found to be of no interest for greenhouse heating. There were possibilities of economic feasibility for heat pumps in northern European countries with electricity/fuel-price ratios (when buying electricity from the grid) of between 2.1 and 3.0 (or lower). Cogeneration systems were found to have the best possibilities, especially in northern European countries with electricity/fuel-price ratios (when selling electricity to the grid) of between 2.3 and 3 (or higher). Heat storage improved the economical performance of the cogeneration systems: life-cycle costs decreased by about 4%. The electricity/fuel-price ratios are calculated with the prices of electricity and fuel which give the same amount of energy. (C) 1998 Silsoe Research Institute.