The rise of the electric car has grabbed many headlines as a major step towards decarbonization. After all, personal transportation is one of the biggest contributors to global CO2 emissions. But for many with domestic charging, the EV could become part of an environmentally focused ecosystem centered around the home, which could also include solar panels, a domestic battery, a heat pump, and potentially other devices in the future. I talked to E.ON’s Timo Feger about how the car forms the hub of this electrically powered network.
Feger runs the TestingLab, a facility in Essen operated by E.ON to validate domestic electrical equipment, particularly home EV chargers. This is a business that remains in a “wild west” mode. If there has been a massive uptick in EVs to choose from in the last four years, the increase in charger brands has been even more pronounced. At its basis, an EV charger is a device to deliver high power over an extended period while communicating with a vehicle’s control circuitry.
This doesn’t sound that challenging, so firms already in the electronics business have pounced on it as a new area of business. But that’s a massive underestimation of the challenges involved. Safety and reliability can be quick casualties. This isn’t necessarily due to cheap engineering. It can be due to misunderstanding the factors involved. For example, one charger design that the TestingLab analyzed was overheating because the engineers had done too good a job isolating all the high voltage components but didn’t allow space for their cooling.
Unfortunately, there are no EU-wide regulations regarding EV chargers. Different countries have their own requirements, such as the use of non-conductive wooden backboards in the Netherlands. Feger noticed that the certification process was more like shallow corporate training than a rigorous safety-focused process. So TestingLab started certifying charger installation engineers properly, and then training trainers to spread the capabilities more widely. TestingLab now trains 100-150 trainers per year, with partners including BMW, Volkswagen and Harley Davidson. The company can test chargers from across Europe to pinpoint an issue. For example, this helped pinpoint a charging failure with BMW’s seminal i3, due to a change in the way it was initializing a cycle.
The home isn’t the only focus of the E.ON TestingLab. It also puts public DC chargers through their paces and has been working on a solution for charging trucks. The problem with large vehicles like this is how hard they are to maneuver. It’s very easy to accidentally damage a charging device by crashing into it. E.ON’s solution is to put the charging cable on an overhead gantry, so the device itself is tucked away somewhere safe. The truck drives under the gantry and then the cable is brought down from above to charge it.
Another concern for public charging is whether the grid can cope. On average, it probably can. The big problem is peak demand and the lack of high wattage grid connections, or at least the lengthy process involved with getting one installed. E.ON’s solution to this is a public DC charger with a built-in battery to buffer for peaks. One version is designed to work with only a 30kW grid connection, sporting two 100kWh batteries on board servicing two 125kW DC connections. This could allegedly charge 40 Renault Zoes in a row before its battery buffer is depleted – which will of course replenish once the charger is idle.
A second version includes the same duo of 100kWh batteries but is aimed at an 80kW grid connection. This can service two 300kW DC connections. It’s worth noting that few vehicles will hit close to this for long when charging. The curve will drop down well below this, tailing off towards more like 50kW over about 50% charge. This will change as cars capable of maintaining faster charging for longer arrive, such as the XPENG G9, but the majority don’t have this capability yet.
The wider problem that Feger identified was how chargers fit into an increasingly complicated electricity supply system. In the home, this revolves around their digitization. If a charging device doesn’t use wired Ethernet, and relies on WiFi instead, a customer might change their home router and not realize they’d cut their EV charger off in the process. This is problematic as smart charging tariffs become more prevalent, where cheaper overnight power is used to charge an EV. When the energy supplier controls the car and charger, this service can even be dynamic, taking advantage of temporary moments of surplus supply. But it needs network access to the charging device to operate properly.
That’s just the beginning, however. Reducing charging costs gets more complicated if you have home solar panels, a home storage battery, and a heat pump to factor in as well. Then there’s the possibility that the huge battery in your car could be made available to your local power supplier to balance the grid, charging when power is abundant and discharging back to the grid at times of peak demand. Called Vehicle to Grid, this technology is still very much in its infancy, but it has been shown to work in limited trials. E.ON’s version has been trialing the concept in Cranfield, and Octopus Energy has been running its Powerloop trial since 2018. It has the potential to solve the intermittency problem of renewable energy without the need for large public battery storage provisions. The UK is seen as a test case for this.
In 2021, E.ON acquired smart grid intelligence company gridX. This company’s software has commercial and consumer applications, which are increasingly interwoven. For the consumer with a full suite of electrified smart home appliances, the software enables them to focus on whether the balance they prefer prioritizes low CO2 emissions, lowest cost, or a warmer house (when a heat pump is included). However, the energy supplier can also tap into this and reduce some heavy usage devices such as the heat pump or car charger to lower power, such as 4.2kW, if the grid is in danger of exceeding its limits.
It’s clear we are entering a phase where integration is king. Those with home charging and a smart energy tariff have realized the benefits of a more connected relationship between their EVs and the charging in their homes. But there’s much more on the horizon. The EV is set to become part of a home energy ecosystem that is not only interconnected internally, but responds to the national supply system as well.
