Recently the website insideevs.com published a story about an energy storage innovation award won by the company EVgo which is creating a network of fast charging stations for electric vehicles. In cooperation with UC San Diego they set up an electric charging station powered by PV panels on the station sunroof connected to used lithium ion batteries from BMW i3 electric cars.
The story claims that the solar energy falling on the station roof can charge approximately 15 cars per day, but does not say whether this is the yearly average or whether this represents the peak Summer charging rate.
EVgo is planning to open its first 350kW ultra-fast public charging station in June of 2017 in Bakersfield, California. This station will have four 350kW chargers and will also feature a sunroof connected to lithium ion storage batteries.
A casual reader might get the impression that this station will charge vehicles using only the solar energy which falls on the sunroof. However, it is pretty clear that such is not the case. The capital expense of these high power chargers will not be justified by charging a few tens of cars a day. Nor will customers be happy about their ability to charge up depending upon how many cars happened to use the station in the previous few hours. Including solar panels and used EV batteries may save some amount carbon emissions, but clearly the intention is to hook up this station to the grid and have year round day and night service.
A 100% solar powered transportation system will require a lot more solar panels than can be included on the sunroofs of charging stations. It will also require some means of dealing with long term variations (e.g. seasonal variations due to the the tilt of the earth’s axis and long term variations in cloud cover) in the solar energy flux. Insofar as the costs of lithium ion battery storage are driven down by a cycle life measured in the thousands, they are not a practical tool for dealing solar flux variations on these long time scales.
rogerkb at energyevolutionjournal dot com