Choosing between technologies will depend on storage capacity and the power discharge time (= response time) from a performance perspective. From the investor’s perspective, it will probably be determined by the cost of storage and the return on investment (ROI). For grid scale energy storage, pumped hydro is so far the most common in bulk storage in both the US and Europe. For other newer technologies such as batteries, we still lack a positive business case to support the investment. It is not just because of the initial high cost of new technologies, the current market framework cannot give a true value of energy and storage. This leads to a lack of interest from investors.
The European Commission recognizes that energy storage is needed for a larger uptake of renewables and a super grid cannot go without energy storage. What we need from the EC are standards and regulation, and the most important thing – a feasible business model for the energy industry.
Trial for largest battery in Europe
Nevertheless, there are some good demonstration projects going-on now. The world’s largest Li-ion batteries with 32 MW storage capacities were installed next to an onshore wind farm in West Virginia, United States to provide fast-response frequency regulation on the grid. A 6 MW Li-ion battery will be installed in eastern England.
This project received £20 million from Ofgem’s Low Carbon Network Fund. Once it is complete, it will become the largest battery storage system in Europe.
In the UK, we are also looking at the potential of using liquefied air as the storage medium. A 350kW pilot plant hosted by Scottish and Southern Energy (SSE) has been in operation since April 2010. The working principal of this storage method is to compress and cool down the air to liquid form for storage. The merits of this method are lower risk as it relies on a mature component assembled into a new process; the provision of large scale storage where smaller sites are required; no limitation of geographical location on the plant and the stored energy, and liquefied air is transportable.
Another new storage technology which will also have high potential is Power-to-gas (P2G). P2G converts excess renewable generation into renewable power, fuel or heat via an electrolysis process. Electrolysis produces hydrogen or synthetic natural gas which can be directly injected into the gas pipeline, distributed onsite as fuel, or further processed to produce methane and heat. This storage method is suitable for countries like Germany and the UK which have extensive use of gas in both industry and homes.
Could the future be the past?
Sometimes we may be too focused on new technologies and overlook conventional ones. We have already been using thermal storage for a number of years. Night storage heaters are a simple and cost effective way to store energy. A study conducted by Glen Dimplex and SSE to assess the potential for smart electric storage system (SETS) showed that by applying advanced electronic command and control capabilities, SETS can have a 20% efficiency gain compared to the current night storage heater.
SETS has a potential to provide 55GW controllable demand if all night storage heaters in the EU- 27 are replaced, comparing to the current storage capacity of 51GW in the EU-27.
Scientists and engineers are working very hard on various storage technologies. What seems to be missing is a clear direction from policy makers to establish the right framework which allows investors to see the true ROI. Then we can get closer to our aspiration of a low carbon network, with confidence in the security of supply.