Thermal Insulation and Operation by Photovoltaic Solar Energy of a Bioreactor

This work concerns the thermal insulation of a digester with a capacity of 3000 liters operating in batch, with a rate of 600kg of the waste, and on the dimensioning of a photovoltaic installation which delivers the energy necessary for the operation of the equipment of heating and stirring of substrates. In the absence of being able to carry out the tests in an installation of 3000 liters, we carried out the fermentation in a digester of capacity of fliter and we then extrapolate the results on the real installation. Thus, the heat losses between the reaction and external environment were evaluated experimentally on a digester with a capacity of one liter with household waste fermented under mesophilic conditions. The thicknesses of insulation examined are 2, 4 and 6cm. The results showed that the optimum thickness necessary to maintain the digestion temperature between 35 and 40°C is 4cm. The numerical model proposed in this work to solve the transfer equations governing the thermal exchanges between the reactional and the external environment give the results which agree satisfactorily with the experimental results obtained. The photovoltaic system proposed to ensure the heating and stirring of the reaction environment is of autonomous type and is provided with a charge controller and an inverter. From a manual calculation on Excel, the optimal number of photovoltaic panels and batteries needed to supply a heating resistor and a mechanical stirrer are respectively 9 and 4. The estimation of the amount of biogas was made by the Hashimoto model. Thus, fermentation of 600kg of waste in the bioreactor with a capacity of 3000 liters can produce 22m³ of biogas.