Concept for a DC-low voltage house

Abstract

The general expectation is that electricity will increasingly be generated decentrally, for example using solar cells. Solar cells provide direct current (DC) electricity at low voltages. Before this energy can be used in buildings, conversion is required to alternating current (AC). However, many AC-powered household appliances, work internally on DC. This implies the need for a transformer within the appliance, in order to convert the AC current of 230 V to (low voltage) DC current. Using PV this way involves two energy conversions with inherent energy losses. It is reasonable, therefore, to assume that introducing a DC (low-voltage) grid can mitigate these losses. The feasibility of this idea has been studied by ECN (Energy Centre the Netherlands), by comparing a grid-connected house to a stand-alone PV-powered house provided solely with DC electricity. The conclusion was that introducing a DC grid would not lead to a significant reduction of energy losses. The present study reveals that further analysis of the energy losses requires to include different conditions and circumstances. The main obstacles to energy loss reduction appeared to be that not every household appliance is suited for DC-low voltage electricity and that the use of a normal distribution system for low-voltage currents involves significant losses during transport. The focus of this research is thus, to find a solution for these problems and develop a concept with these solutions for a DC low-voltage system, which does reduce energy losses. The main points of interest studied are: • Alternative ways to transport DC low-voltage electricity in a single family house & minimal energy losses . • To think of the most efficient spatial lay-out and furnishing of a house in view of minimising the distance between generation and end-use of DC electricity. • To use a hybrid system consisting of an AC and DC grid connected to the various household appliances depending on their suitability for either form. • To find out the adequate scale for DC power storage and generation. The result is a conceptual design of a house incorporating stated points of interest. The design will be based on zero-energy houses, now being planned for a neighbourhood in the city of Zoetermeer, the Netherlands. The design aims at mitigating energy-losses in the house and neighbourhood without loss of comfort for the inhabitants. Besides, the oral presentation will focus on the economical consequences of the concept(s). 1 Delft University of Technology, Faculty of Architecture, MTO/BT, The Netherlands, A.vanTimmeren@bk.tudelft.nl 2 Delft Institute for Sustainable Energy, Faculty of chemical technology & Bioprocess Technology, Delft University of Technology, The Netherlands, J.Schoonman@tnw.tudelft.nl