Smart storage of solar power using electric cars

Solar energy is essential to realise the energy transition, but what happens when the sun doesn’t shine? Simply use another element of the energy transition instead: the growing numbers of electric vehicles. An electric car can still supply electricity to the grid while it’s parked. That’s not only useful when the sun isn’t shining; you can also use the stored electricity to compensate for fluctuations in demand and avoid using a carbon-emitting power plant to generate additional electricity. Smart charging of car batteries, as well as home- and community batteries, will make it all possible, according to the calculations of energy scientist Wouter Schram. He will earn a PhD based on his research on 10 July. “If we only drove electric vehicles in the Netherlands, and if we optimised the charging process, on average it would contribute more to the peak demand than all of the Netherlands’ coal-powered plants combined.”

Foto van twee auto's die naast elkaar aan een laadpaal staan
Photo: iStock/Sjo

Smart charging involves considering the cost of the electricity at that moment: when will the electricity be generated for free through solar power? With the phasing out of net metering for solar panels, it is becoming increasingly attractive to consume the solar power yourself instead of selling it to the grid. And storage in batteries is a form of self-consumption. But smart charging also means that batteries will play a role in reducing CO2 emissions.

Schram’s research analysed examples of model neighbourhoods in eight European countries equipped with solar panels, a neighbourhood battery, electric cars and heat pumps. “These technologies can reduce the neighbourhood’s CO2 emissions by 55% to 73%, depending on the country”, according to the PhD candidate’s calculations. The variation in the percentages is due to the mix of energy sources: how much pollution is created through energy production. In a country such as the Netherlands, which primarily uses coal and gas for electricity generation, the switch to solar energy would have considerable impact. “So make sure to charge your batteries with clean electricity from solar panels, or it won’t make a difference from a CO2 emissions perspective.” Schram has developed optimisation algorithms to reduce costs and CO2 emissions simultaneously.

If we only drove electric vehicles in the Netherlands, and if we optimised the charging process, on average it would contribute more to the peak demand than all of the Netherlands’ coal-powered plants combined.

Greenhouse gas emissions

The use of home- and neighbourhood batteries does increase the energy community’s greenhouse gas emissions, however. “That’s due to the manufacture of the batteries and so-called ‘conversion losses’ during use: part of the solar electricity is lost in the form of heat during charging, and when the battery is discharged it also produces heat, and therefore loss. There’s another reason to use batteries intelligently, because by charging them when there’s plenty of clean energy available, you can use the stored electricity at moments when electricity generation would otherwise emit a lot of greenhouse gases.” Recycling raw materials, or even complete batteries, can help reduce greenhouse gas emissions from their manufacture even further. “Car batteries are subject to strict performance requirements, but once they no longer meet the requirements for use in cars, they can still be used as a home battery. There’s no market for used batteries at the moment, but that might change in the future.”

Foto van een elektrische auto die aan het opladen is, in een straat in de stad
Photo: iStock/Tunart

Conditions

There are some conditions for the smart use of batteries. “Most cars cannot feed-in electricity to the grid at the moment, so carmakers have some work to do. And charging stations have to be made suitable for two-way traffic.” At least as important as these technical conditions are the government’s measures to encourage their implementation. “In contrast to coal-fired power plants, you can quickly turn any number of batteries on and off. But if you want to charge batteries as sustainably as possible, there isn’t a stimulus for that right now. With the right infrastructure, you can make it possible for the idealistic consumer to reduce their CO2 emissions with smart charging. Or you could imagine an economic stimulus, for example by having a market party install batteries in your home, where you can use them to store electricity from your own solar panels in exchange for supplying electricity when demand is high.” Once all of these conditions have been met, batteries would be able to dramatically increase the contribution of solar energy when demand for electricity peaks. “Because then you wouldn’t have to burn coal to generate electricity.”