Design of an energy management system utilizing optimum energy consumption of a distribution level microgrid
Bisschoff, Wilhelm Andreas
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Currently within South Africa, net-metering policies are not yet widely implemented which hinders the adoption of residential microgrids. Without proper net-metering policies in place, the benefits of residential microgrids are limited to self-consumption as all energy fed into the utility grid is lost without remuneration. This leads to an inefficient and non-profitable microgrid system. To improve the efficiency and feasibility of a microgrid system in areas with no net-metering policy, it is of utmost importance that an energy management system (EMS) that optimises self-consumption, of the generated energy, be employed. This dissertation discusses the design, simulation, implementation, results obtained and feasibility of such an EMS. The EMS was designed according to a typical living standard measure (LSM) group 8 residence. A simulation model was designed to represent the load profile of the residence with and without the intervention of the EMS. The EMS employed various energy saving strategies along with a strategy focussing on self-consumption. Simulation results showed that in certain scenarios, the EMS would improve the self-consumption percentage from 83% to 98%. The EMS would also reduce the energy consumption off the utility grid from 35.6 kWh per day to 12.7 kWh per day. This would be possible by actively controlling the loads to operate at specific times during the day and by reducing the amount of running hours of certain loads. To verify the accuracy of the simulation model, the EMS was installed into an experimental test station with real-world loads. The microgrid was installed at a typical LSM group 8 residence in Potchefstroom and employed a 2 kW solar photovoltaic (PV) system with a grid-tie inverter. The control system which housed the EMS software was installed along with the solar PV and grid-tie inverter system. The control system consisted of a programmable logic controller (PLC) which controlled relays connected in series with the loads. Experimental results from the test station showed that in certain scenarios, the EMS improved the self-consumption percentage from 84% to 95%. The EMS also reduced the energy required from the utility grid from 34.2 kWh per day to 9.8 kWh per day. This was possible by efficiently controlling the loads according to the incoming solar PV profile and minimising energy consumption when little or no solar PV energy was generated. The feasibility of the integrated system depended greatly on the initial investment capital available. In the case that the integrated system could be funded without the need for a loan, the saving on electricity costs and the investment cost would reach a break-even point within four years. In the case that a loan would be used to fund the investment, the monthly repayment cost would be covered by the monthly electricity bill savings and the total monthly cost would still be less than the monthly electricity bill without the integrated system. The adoption of the integrated microgrid system would therefore be a feasible solution to counteract rising electricity costs.
- Engineering