Reading ‘Die Welt’ over breakfast on my way back from Nuremberg, I was alarmed by an article which implied that Germany was very close to running out of electricity during the last week of January. Like the UK, the country has made significant strides towards renewable energy options and its shift away from conventional and nuclear power generation means wind and solar power are crucial elements of the power mix.
On those late January working days, however, climatic conditions were totally adverse. A cold, still air mass sitting over almost all the country reduced wind power to negligible levels and severely limited solar generation, all at a time when customer demand, particularly for heating, was increasing. It’s probably rare for the majority of the UK to have the same weather but it could happen here, so it set me thinking on the implications for electric bus operations.
Small battery packs with opportunity charging reduce vehicle weight but need electricity at peak times, so tend to increase the need for peak generation capacity during the working day. Overnight charged vehicles, on the other hand, draw electricity when capacity is available and fill the demand troughs created by peak time users. Filling these troughs also allows base load power stations to work more efficiently at a more constant output. The current downside of course is vehicle weight but as battery technology continues to develop, this can be expected to reduce.
A German report a few years ago suggested that if all buses went over to rapid opportunity charging, peak electricity generation capacity would need to double whereas overnight charging makes better use of existing assets and encourages their replacement with non time and weather dependant base load plant using renewable fuels. But then why not run directly on renewable gas from waste digestion and get many of the environmental benefits at much lower cost?
There is an alternative take on overnight charging, the opportunity to use power stored in vehicles not required in service to meet depot requirements at a lower cost during the day….