Study of a Power Supply System Operation Based on Methane Generator Supported by an Energy Storage System, to Cover High Fluctuation Electrical Loads: Greenhouse Case Study

Abstract The operation of a greenhouse requires the consumption of high amounts of energy. The problem is strengthened by the energy crisis that characterizes our days. This article studies an energy management strategy based on the utilization of methane generators (MG) for energy saving in greenhouses. The management strategy includes covering the energy needs of a greenhouse unit (GHU) by directly injecting the energy produced by the generator units. If the energy produced from MG cannot meet the energy needs of the GHU, an energy storage system (ESS) or a backup (in case ESS is unavailable) is used to support the load, covering the gap between production and consumption. In case of excess energy, priority is given to charging the ESS, and the possible presence of excess energy is led to the network. The main objective of energy management is the optimal design of the MG-ESS system to minimize the possibility of energy excess and deficit. The analysis presented is based on actual GHU energy demand. The special feature of this load is the existence of strong daily fluctuations in energy consumption, especially during the summer months. This study presents a methodology for managing such loads with the main objective of maximizing the operating efficiency of MG. Briefly, this article brings a new look to the existing literature in the following areas: (I) a methodology for the efficient operation of methane generators in combination with ESS to cover both mild and intense power fluctuations has been developed, (II) The mapping of the load profile and its division into zones of different power levels providing the possibility of choosing different sizes of generators that will operate at their optimal power has been achieved and (III) a techno-economically optimal ESS to support the generators in meeting load needs and absorbing excess energy has been designed. The analysis based on the use of three different MGs in the three mapped load zones that will operate at constant power due to their support by an ESS led to the identification of the appropriate combination of MG-ESS for the autonomous operation of the GHU. The preliminary economic evaluation of the optimal MG-ESS combination based on LCOE showed that the proposed system (LCOE = 0.216 – 0.279) is competitive with the existing system (LCOE = 0.392) responsible for covering the load’s energy demand.