Storing renewable energy means going electric

To increase the share of wind and solar in the energy mix, we need efficient storage solutions for when energy is abundant (at sunny or windy days) and for delivering it back when energy is scarce. One group of solutions that grows in popularity is battery storage. Static batteries are installed with solar power plants to operate as a buffer. Batteries in electric vehicles are also used as temporary storage for renewable electricity. A second group of solutions for storage is the dynamic management of electricity demand. Refrigerated warehouses can decrease their temperature with one of two degrees when renewable energy is abundant or demand is low. In the same situations, energy companies can remotely switch-on household equipment such as washing machines or dishwashers to ‘store’ renewable energy. Other storage solutions are for example pumping water in a reservoir to use it later for hydropower.

Limitations of electricity as carrier of renewable energy

In all of the above storage cases, electricity has become the carrier of renewable energy. But electricity is not always a usable carrier. In the heavy-duty transport sector, electricity doesn’t work. The power demand is too high in comparison to their storage capability for electricity. Trucks and ships consume so much energy and travel such long distances that they would need to fill their entire cargo space with batteries to complete their itinerary. For commercial aircraft, batteries are simply too heavy to lift.

Heavy-duty transport will account for about 40% of CO2 emissions in 2050 if we continue using fossil energy*. Hence, we need other ways to make renewable energy available for this purpose.

Power-to-gas

Wind and solar electricity is already used to create hydrogen from water. Hydrogen can be converted back to electricity e.g. in hydrogen powered electric cars. However, during the hydrogen production process, one can also add CO2. This process is called Power-to-gas (P2G) and creates methane gas which is equal to the gas used domestically for heating and cooking.

Methane gas is increasingly used as fuel replacement for oil and diesel in heavy-duty transport. Manufacturers produce trucks and buses that are powered with methane gas. Standard gasoline engines can be easily modified to use methane gas. New cargo ships are equipped with engines that run on methane gas as well. The combustion of methane emits less CO2 and other undesired particles than traditional fuels such as diesel and gasoline.

When methane is produced from solar and wind electricity, we can power heavy duty transport vehicles in a completely renewable way with zero CO2 emissions. Next to the zero CO2 benefit, there are some other advantages: Since power-to-gas methane is equal to fossil methane, existing infrastructure (e.g. gas grid distribution, engine technology) can be reused. And the power-to-gas production can be boosted during peak moments of renewable energy, thus operating as a storage facility as well.

There is still some ground to be covered before the production of Power-to-gas is economically viable. But at various pilot production sites, today engineers make good progress in bringing the Power-to-gas efficiency to a level where it can compete with fossil methane. This will bring a significant next break-through in the energy transition: we enable a further growth of renewable energy by adding a new storage solution and we allow a large energy-demanding sector to let go the use of CO2 emitting, fossil sources.