EV cars charging at street side charging station

Flexible charging can help the UK grid accommodate 60% more EVs—and make them even cleaner

 February 21, 2019 

Electric vehicles (EVs) are more efficient and less polluting than comparable rides powered by traditional internal combustion engines—even when EVs are charged on relatively dirty grids; plus, the greener that grids get with renewables, the cleaner EVs get with their associated emissions.

But there’s been the nagging question of whether, as sales continue to ramp up, EVs could become too much of a good thing for the power grid. For example, after 1.1 million new electric vehicles hit the roads globally in 2017, Bloomberg New Energy Finance forecasts that worldwide annual EV sales will hit 11 million by 2025 and 30 million by 2030. Can the electricity grid handle the coming wave of EVs and all the charging—some slow, some fast, and some superfast—that will come along with it?

A 2018 study from the UK’s Office of Gas and Electricity Markets (Ofgem) found reason for optimism—assuming that mass EV uptake comes hand-in-hand with intelligent charging systems. Ofgem found that “smart, flexible” charging solutions could allow at least 60% more EVs to connect to the existing UK power grid than would be the case without intelligent charging systems. With flexible fast charging, up to six times more EVs could connect, the authors found.

That’s possible, Ofgem says, because unlike inflexible EV charging—which blindly fills a big battery from the time it’s plugged in until it’s either topped off or the plug is pulled—flexible EV charging pays some attention to what’s happening beyond the outlet.

Charging flexibility makes all the difference

Inflexible EV charging, the authors say, increases peak demand, risks local outages, reduces system diversity, constrains areas that are already constrained, and forces all energy consumers to pay for new electrical infrastructure needed because of the added demand of EV owners.

Flexible EV charging, on the other hand, lowers the increase in peak demand, enables the more efficient use of existing assets, improves system diversity, defers or avoids power-infrastructure expansion, and can reward consumers—in pounds and pence (or dollars and cents, on this side of the Atlantic)—for their flexibility.

That’s a lot of cons and pros, but the big one has to do with peak demand. Depending on when peak demand occurs, and—more importantly—what power plants are called upon to meet that demand (often an expensive, polluting, fossil-burning peaker plant), there could be big implications for marginal grid emissions that risk casting a bit of a cloud over the clean EV story.

Keep in mind that the above doesn’t take into account vehicle-to-grid technology, which could harness EVs as a stored energy source, tapping into parked cars rather than peaking plants. For example, a Tesla Model 3 battery stores four to five times more electricity than a Tesla Powerwall battery. And overall, EVs that charge using a 240-volt outlet draw about as much power as six microwave ovens running simultaneously. Then imagine all that energy and capacity at coordinated scale. “As a pooled resource, the growing number of EV batteries could provide a wider range of valuable grid services, from demand response and voltage regulation to distribution-level services, without compromising driving experience or capabilities,” the Ofgem team explains.

How flexible charging unlocks greater grid value—while reducing emissions

Closer to home, the U.S. Department of Energy’s INTEGRATE study has estimated that with 3 million EVs—half of them using flexible charging and EV batteries as energy storage—peak demand would fall 1.5 percent. You read that right: adding 3 million electric cars could cut peak demand. Electricity costs would decline by 1 percent to 3 percent. In addition, renewable-energy curtailment would shrink by 25 percent and overall grid emissions could shrink, too.

That last bit about renewable energy curtailment and grid emissions is vitally important. Curtailment means wasting renewable energy that would otherwise be generated because the grid can’t accommodate it at a particular time.

Renewable energy’s contribution to the grid can change minute-by-minute. So, when we consider how to do smart, flexible charging of EVs for the optimization of power delivery, we should be asking not just if and how the grid can handle that demand but also what sources of generation are on the margin and/or at risk of curtailment at any point in time. In other words, how can smart, flexible EV charging help electricity grids from the UK to the U.S. not only handle more EVs but potentially do so while lowering their marginal emissions by charging at times of cleaner energy and avoid times of dirtier energy.

This sits squarely in the sweet spot of WattTime’s Automated Emissions Reduction (AER) technology. The software—including a recently updated EV charging module—uses a combination of real-time grid conditions and historical emissions data to track the precise mix of renewable and fossil energy coursing through a device such as an EV charger, in 5-minute increments.

This is especially important when it comes to EVs and marginal emissions. Yes, we can measure EV emissions based on overall grid mix in a particular region. But what arguably matters much more is marginal emissions. When I plug in my EV to charge (or unplug my EV to drive away), what power plant turns on or off in response to that demand? And can we ensure—through a combination of smart, flexible charging and the right signal, such as AER—that EVs are using as much clean energy as possible while avoiding dirty energy?

With the kind of smart, flexible charging envisioned in the UK Ofgem report and WattTime’s AER technology, the answer is yes. And that’s as big a story, we’d argue, as the UK grid being able to handle 60% more EVs.