Coordinated charging of electric vehicles

Abstract

Electric vehicles recharged from renewable energy sources will play an important role in reducing the key adverse impacts of transport: air pollution, depletion of oil resources, and CO2 emissions. But they will also add to the demand for electricity. Most electric vehicles will be charged at home, overnight. If they all charge at the same time, during the evening peak, they could cause the electricity supply of households or streets to become overloaded. Increases in peak demand ultimately require upgrades to the transmission and distribution infrastructure, which add significantly to the cost of electricity. Time-of-use tariffs can encourage users to shift their demand to times when electricity is cheaper because demand is usually lower. But to better manage the demand for electricity and control peak demand, we need appliances, including electric vehicles, that respond in real time to changing supply conditions by shifting their demand. Ultimately, having demand that can respond to the available supply will allow greater use of variable, renewable energy sources. An electric vehicle will typically need to charge for a few hours overnight. Coordinating the charging of electric vehicles distributed over many premises in an area can smooth the total demand in that area. In this paper we describe a simple load control system that uses signals broadcast from street transformers, typically servicing 30-50 premises, to influence the behaviour of smart appliances in the supplied premises to control the demand profile.