Sun. Oct 2nd, 2022
An air/water heat pump nestled in a corner.
enlarge An air/water heat pump nestled in a corner.

A spicy slogan for the energy revolution is to “electrify everything” – to replace fossil fuel applications with electrical appliances that can be powered by a clean grid. Of course, most grids are nowhere near zero-emission, and this can complicate the impact of electrification. Is it certainly the case that an electric car, with the electricity that is available to you, will, for example, cause fewer emissions than a fuel-efficient car that runs on gas?

While that question can be frustrating for a consumer, it is could be even more thorny for policy makers. If networks need to become cleaner for the “electrify everything” strategy to be beneficial, programs that encourage things like electric cars may not have the intended effect. To answer this question more clearly, a team led by Florian Knobloch from Radboud University did the math to find out what green EVs and heat pumps for home heating are like in different countries.

Pump up the heat

If you’re unfamiliar, heat pumps operate on the same basic principle as an air conditioner: they use cooling coils to dump heat from one side to the other. But instead of just discharging the heat from your home to the outside air like an air conditioner does, they can also run the other way and dump heat energy from the outside air (or ground) into your home, even when the outside temperatures are low. This process is extremely energy efficient, even when compared to high-efficiency gas stoves.

The researchers divided the world into 59 regions, using data about the power plants that use their grids, as well as the types of vehicles and home heating methods in use. They then used estimates for total life cycle emissions (including production and use) from the range of electric vehicles and heat pumps available. This was connected to a detailed economic model that simulated a realistic introduction of these technologies from 2015 to 2050, using several different scenarios.

The first scenario simply sees a continuation of current trends. The grid will be only 16 percent cleaner by 2050, in terms of emissions per kilowatt hour of electricity. Electric vehicles are growing modestly to about 19 percent of road transport, and heat pumps cover 16 percent of residential heating demand. The second scenario represents a strong emissions reduction policy, pushing EVs to half of road miles, heat pumps to more than a third of home heating, and making the grid 74 percent cleaner. A third scenario is a combination of the first two: strong policies that encourage the use of electric cars and heat pumps, but no policy to clean up the grid. That tests whether “electrifying everything” could backfire.

The results show that conditions where EVs or heat pumps increase emissions are rare, even today. The average breaking point is around 1,000 grams of CO2 per kilowatt hour of electricity, which is roughly the efficiency of the oldest and dirtiest coal-fired power stations. As long as you’re just a little bit cleaner than that, EVs and heat pumps should cut emissions. So for 53 of the 59 regions analyzed – which represent about 95 percent of road transport and residential heating – it is already true that replacement with electric vehicles or heat pumps is beneficial.

Some exceptions allowed

There is a wide range of results here. Compare, for example, Switzerland’s exceptionally low-carbon network with Estonia’s, which mainly runs on oil shale† If you exchange a vehicle with a combustion engine in Switzerland for an electric one, emissions are reduced by 70 percent and a heat pump by about 88 percent. But in Estonia an EV increase emissions by 40 percent and a heat pump pushes that to a dazzling 120 percent.

A more significant exception can be found in Japan. In the scenarios with little progress in grid emissions, a decade from now, the combination of Japan’s dirtier electric grid and preference for hybrid vehicles means that EV swapping doesn’t quite pay off.

Maps for the three scenarios: current trends with no policy support, an aggressive policy effort on both grid emissions and uptake of EVs and heat pumps, and an end-use only scenario with no additional policies for the grid but increased uptake of EVs and heat pumps.
enlarge Maps for the three scenarios: current trends with no policy support, an aggressive policy effort on both grid emissions and uptake of EVs and heat pumps, and an end-use only scenario with no additional policies for the grid but increased uptake of EVs and heat pumps.

But on average around the world, EVs already represent about 31 percent emissions savings per kilometer, and heat pumps are a 35 percent savings per heating unit. Even in the scenario where these technologies are promoted but the grid is not cleaned much, there is a significant advantage until 2050. And that is clearly greater in the scenario where policies also reduce emissions from the grid more. Total vehicle emissions are reduced by about 30 percent in this scenario and home heating emissions are reduced by about 45 percent.

The model assumes continued efficiency gains for fossil fuel-powered cars and furnaces, as well as their electric counterparts, but emissions from fuel-burning machines are mostly unavoidable. Electric vehicles and heat pumps are already cleaner (unless you live in Estonia) and can improve further as the grid improves.

As time goes on, emissions from electric vehicle production account for a larger proportion of their total life cycle emissions, the researchers note. You can make the vehicle efficient and clean the power grid, but you’ll also have to clean up the industry to keep reducing that carbon footprint.

Nature Sustainability, 2020. DOI: 10.1038/s41893-020-0488-7 (About DOIs).

By akfire1

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