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Smart charging of electric vehicles using 'green' power at Fraunhofer ISE

Electric vehicles make most sense if their batteries are charged using electricity from renewable energy sources – but the supply of ‘green’ electricity is not always adequate. Researchers at the Fraunhofer Institute for Solar Energy Systems ISE in Germany have now developed an intelligent charging station, which can adapt recharging times to suit energy supply and network capacity.

Germany aims to have one million electric vehicles – powered by energy from renewable sources – on the road by 2020, as it pushes towards CO2-neutral electromobility.

However, as more solar and wind energy is incorporated in the power grid, the proportion of intermittent electricity is increasing. There is also a growing risk that the rising number of electric vehicles will trigger extreme surges in demand at rush hour.

‘What we need is a smart grid that carries information in addition to power,’ says Dominik Noeren of the Fraunhofer ISE. The structure of the grid has to change from being based on energy demand, to being based on production output.

‘Electric cars are best equipped to meet this challenge,’ Noeren believes.

But since battery electric vehicles would on average be parked for at least 20 hours out of 24, this offers an opportunity to recharge them when the wind picks up or when electricity demand is low.

The ‘smart’ charging station developed by Fraunhofer ISE enables electric vehicles to be recharged when the system load is low and the share of energy from renewable resources is high. In this way, load peaks can be avoided, and the contribution of solar and wind power fully exploited.

‘For us, it is important that end consumers are completely free to decide when they want to recharge,’ Noeren emphasizes. ‘We do not want them to suffer any disadvantages from the controlled recharging of their vehicles’ batteries.’

This is why Noeren favors electricity rates that adapt to the prevailing situation in the power grid – more expensive in periods of peak demand, and particularly cheap when there is a surfeit of renewable energy.

The person using the ‘smart’ charging station could then choose between recharging immediately, or opting for a cheaper, possibly longer, recharging time.

For the latter, they just need to enter the time when their vehicle has to be ready to drive again. The charging station takes care of everything else, calculating the costs and controlling the recharging process.

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