Computation based Comparison of LVDC with AC for Off-Grid Energy Efficient Residential Building

Abstract

It is a fact that the renewable energy sources (RES) such Solar Photovoltaic (SPV) and fuel cells are inherently DC power sources. The importance of the switch to cleaner and renewable source of energy that is generated as local possible need to be acknowledged. However, a historically established distribution system that is AC based is prevailing. This requires DC-AC converters for the integration of solar energy to the existing power distribution infrastructure. Increasing usage of DC powered equipment and the introduction of electric vehicle charging stations in the power system will add to the further increase in consumption of DC Power. Due to the difference in the modes of power generated and consumed, clean and renewable DC power generated need to be converted to AC power for supply and distribution compatibility and later again forced to re-convert major part of the incoming AC power to DC power for end use for residential applications. This conversion and reconversion, results in adding losses and increasing complexity to the system. The DC-AC-DC conversions are reduced to a certain extent by introducing a Low Voltage DC (LVDC) system. This report investigates the potential for using LVDC system in residences with on-site solar PV power generation by calculating the net power drawn by a direct-DC powered house compared to a similar house with AC distribution, considering identical DC-internal loads. Also the number of PV panels required for supplying the load and the storage batteries is calculated for both AC and 48V LVDC system. It is clearly seen that over and above the savings in energy, there is an added advantage of huge savings on initial investments, which may unlock the resistance and give an extra mileage when performing the payback calculations for these upgrades.