Solar Biogas Plant Using Heat Accumulators and the Calculation Technique for the Main Units’ Parameters

Abstract

The energy efficiency of existing biogas plants (BGP) can be improved using solar energy. At present, more than half of the thermal energy generated by solar collectors in solar biogas plants remains unclaimed for directly covering the technological needs of biogas plants. A schematic diagram of a bioreactor plant with two bioreactors has been developed, which allows, regardless of the seasonal and daily irregularities in the supply of solar energy, to maximize the full potential of the thermal energy generated by solar collectors to ensure all the energy consumption of the technological scheme of fermentation of the feedstock. One bioreactor is fully operational all year round and the second during a period when the amount of thermal energy generated by solar collectors exceeds the total level of thermal energy required to compensate for all energy costs for biogas production in the first bioreactor. The connection (or disconnection) of the second bioreactor is carried out by a thermocontroller with servo drives installed on the pipelines for the circulation of the coolant, the supply of a daily dose of the raw material substrate to the bioreactor, and the discharge hatch into the liquid fertilizer tank. The round-the-clock maintenance of the optimal thermal mode of biomass fermentation in each bioreactor during periods of absence of solar energy is ensured by supplying the thermal energy of the discharge of a phase-transition heat accumulator installed in a reservoir with a liquid around each bioreactor. Using the example of raw materials—cattle manure (cattle) with a thermophilic mode of fermentation—the method of calculating the optimal values of the parameters of each bioreactor of a bioreactor, the area of solar collectors, and the amount of heat storage material is considered. Implementation of the proposed biogas plant makes it possible to reduce the area of solar collectors by more than two times and by 25% the total cost of the main biogas units.