What is required for realizing energy transition – perspective on energy storage

Energy transition to a renewable energy system will not be easy and will require the deployment of sustainable electricity generation, such as wind and solar power, on a massive scale. Electrification, combined with the rethinking of how and especially when we use energy, is required to reduce carbon dioxide emissions to the atmosphere. Already wind and solar power are becoming the cheapest sources of electricity in many parts of the world, but their share cannot be increased beyond certain limits without destabilizing the electricity grids.

We drastically need some methods to store the electricity when large amounts of wind and solar power are available, to be utilized during the night and when there is no wind. Currently, the state-of-the-art technology for electricity storage is to pump water uphill and run the water through a turbine to produce electricity when required. Unfortunately, it has been estimated that the pumped hydro storage capacity of the world could be increased only by a factor of 2, due to the limited availability of areas with sufficient height difference. This will not be enough to satisfy the need for energy storage required by an energy system relying only on solar and wind power. Therefore, alternative electricity storage methods are required.

Development of batteries has taken significant leaps during the last fifty years, but the most significant breakthroughs happened already more than 30 years ago, resulting in a Noble prize in chemistry in 2019. State-of-the-art technology, lithium-ion batteries, is well suited for powering portable devices, electric vehicles, as well as for some specific grid support services, but I doubt that these batteries will play a major role in grid-scale energy storage, simply because limited supply of raw materials such as cobalt, nickel, lithium and even copper or phosphates. 

The year 2021 was the first year since the early 1990s when the cost of battery raw materials increased due to the growing demand. Li-ion batteries are required for the electrification of transport and cannot be spared for grid-scale storage. This highlights that alternative technologies based on materials able to fulfill the so-called terawatt challenge are urgently needed. As the scale of the energy storage required in the terawatts, we are limited to materials that are very abundant and widely available.

At the moment no perfect solution exists yet, but I believe that materials able to fulfill all the criteria for sustainable energy storage will be developed in the future.

Fortunately, there is some light at the end of the tunnel. Batteries based on sodium and sulfur, as well as sodium-based salt batteries have been developed, and for example, flow batteries offer a very wide range of new chemistries. At the moment no perfect solution exists yet, but I believe that materials able to fulfill all the criteria for sustainable energy storage will be developed in the future. This work is accelerated by the development of advanced computational tools for accelerating materials design and discovery, including quantum chemical calculations and machine learning based analysis. I remain optimistic that in the next 10-20 years materials design will take huge steps forward, resulting in sustainable materials for batteries. 

Batteries are only a solution for energy storage for up to a couple of days, so the question of how to arrange electricity storage for weeks or even for seasons is still unanswered. There, I believe that advanced materials design efforts will allow the production of chemical fuels, such as hydrogen. This will enable energy transition, accelerated by the design of new materials also for sustainable power generation. But acceleration and intelligent design of materials will be the key to realizing this future.

Pekka Peljo

Associate professor, University of Turku