Energy efficiency and cost performance of direct-current power supply systems in residential buildings by 2030s and 2050s

Abstract

In an effort to clarify the potential use and effectiveness of direct current (DC) power supply systems and further promote their usage, this study investigates the energy saving and cost performance characteristics of such a system for a detached house equipped with roof-mounted solar photovoltaic (PV) panels. Our evaluation considered different DC-powered appliances under different energy price conditions and made projections based on present, 2030s, and 2050s scenarios. Initial cost reductions were also considered based on assumed near-future technological developments. Our case study results show that the simple payback period is likely to be shortest in cases where DC power is only used for low-voltage appliances under present price conditions, when supplying DC power to cover interior space heating under the 2030s energy price scenario, and when covering all DC-powered appliances (including water heating) under the 2050s scenario. Taken together, these results indicate that it is desirable to set the introductory targets while projecting future energy price fluctuations and anticipating the cost reductions that will result from ongoing technological developments.