Performance assessment of photovoltaic, ground source heat pump and hydrogen heat generator in a stand-alone systems for greenhouse heating

The energy balance is one of the most important factors of the commercial greenhouses. Diesel, LPG and natural gas are generally used as fuel for greenhouses heating. A great amount of scientific research are focused on innovative renewable energy systems in the agricultural sector. The goal is to reduce the use of fossil sources and to change the energy mix of the traditional greenhouses heating system. However, the renewables energies sources and the micro-generation systems still play a niche role in the energy panorama, mainly due to the intermittence of the energy production. In particular, for the solar energy systems used for greenhouse heating applications, the energy produced must be storage and used at night. Stand-alone energy storage systems is necessary to overcome the discontinuity in the energy production and consumption. In this paper, the performance of the stand-alone renewable energy systems for greenhouse heating during the winter season was analyzed. The aims of this research is to compare the energies efficiency of two different stand-alone systems based on hydrogen. The first systems consist of a photovoltaic array connected to an hydrogen electrolyzer, a pressure tank, a fuel cell and a ground source geothermal heat pump. The second system is analogous to the first but a direct air hydrogen burner was used instead to the fuel cell and the heat pump. The second system was designed in order to shorten the energies chain and to simplify the plant. A performance analysis ware conduct in order to define the energy efficiency and the power productions of the both systems. The results show that the heating power produced by the first system is greater than 30% compared to the second one if the hydrogen production and consumption of the two solutions are the same and the coefficient of performance of the heat pump is 5. Furthermore, the first system increasing the greenhouse temperature by 6°C to 10°C compared with the ambient conditions, while the second system by 3°C to 7°C.