Optimal energy management of hybrid energy system for a commercial building

Abstract

High consumption of electricity in commercial buildings, is a global challenge, faced by many countries in the world. The high consumption of purchased electricity from the utility, results in high electricity bills for commercial consumers. The cost of energy consumed by the commercial buildings is high as an optimal power flow strategy to the load is not applied. The optimised on-site grid-tied hybrid renewable energy system under time of use tariff, has been found as the attractive option for solving this problem. As a result, this research work has focused on the development of an optimal energy management model, to minimise the electricity cost of a commercial building supplied by the on-site grid-tied hybrid photovoltaic-battery-diesel generator (PV-Battery-DG) hybrid renewable energy system (HRES), under time of use tariff. The selected solution methodology has consisted of a review of related literature, selection of an appropriate case study, optimal sizing of on-site grid-tied HRES, using Hybrid Optimization Model for Electric Renewable (HOMER), development of on-site grid-tied HRES model and simulations using realistic and measured data, as well as an economic impact assessment of scheduled grid load shedding, on commercial consumers. The optimum sizes are 18 kW for the PV, 18 kW for the DG, 6 Surrette 6CS25PS batteries and 15 kW for the bidirectional converter. The most economic NPC for the gridtied PV-Battery-DG configuration, obtained in this study, is $86740, while the LCOE is $169/kWh and the operating cost is $5212, for 25-year period. The daily economic analysis results, indicate that the optimal energy management of the hybrid system has a potential daily savings of 49.51%, based on the data provided and the assumptions made. Results have shown that the proposed grid-tied hybrid PV-Battery-DG HRES has the potential of mitigating the South African scheduled load shedding for a commercial consumer’s building. The optimal energy management of the proposed hybrid energy system under TOU has minimised both the grid consumption, as well as the consumer’s bill and the diesel fuel for running the DG. The main benefit of reduced electricity purchased from the grid, is the reduced electricity bill for the commercial consumers. Daily scheduled grid load shedding impacts differently on commercial consumers; this is due to the available renewable resources, battery SOC, as well as the amount of DG energy used. The author anticipates that, in future, Smart grid technologies will have a positive impact on commercial demand side management. These technologies may consist of communication systems, monitoring systems, control devices and on-site HRESs. They will enable a sustainable, efficient and secure electricity supply to a commercial building.