New technologies to enable longer duration energy storage offer much-needed optimism in the race to Net Zero, but they may come with planning challenges. Louise Leyland, associate at PWA Planning, explains more.
Long duration energy storage has the potential to reduce the cost of achieving net zero by storing excess low carbon generation for longer, helping to manage variations in generation, such as extended periods of low wind.
Recognising the potential of this, the government recently announced it will implement a policy on long duration energy storage by 2024, demonstrating how this technology will be key to meeting the UK’s 2050 Net Zero target.
What is long duration energy storage?
The industry has struggled to agree on a definition for long duration energy storage (LDES), but it is now generally understood to be storage capability of more than 10 hours, and potentially up to 200 hours.
Effectively, this would give electricity a longer shelf life than that enabled under current short and medium duration battery energy storage schemes. It means grid operators can use it more effectively and for longer when taking into consideration changing customer demands, climate, extreme weather events and seasonal changes.
Why is energy storage needed?
We’ve previously explored how energy storage can help the UK meet carbon reduction targets by overcoming grid constraints which occur when the power generated on parts of the system exceeds the physical capacity of the local grid to export the power.
These constraints have been increasing over recent years, mainly due to the increase in wind generation outpacing the development of the necessary grid capacity.
Longer duration storage facilities with renewable generators would provide a source of local demand for any surplus electricity, reducing the need for curtailment. The stored electricity could then supply the grid when the network is less congested.
Are longer term energy storage technologies commercially ready?
In short, yes, but in limited cases. The government has continued to pledge funding into the technologies to increase their availability and productivity. Some longer-term storage technologies being developed and tested include:
Flow batteries – These batteries work by converting electricity into chemical energy. In a rechargeable battery, the processes used to convert electricity to chemical energy can be reversed when the device discharges. Flow batteries have shown promise in the UK. They store chemical energy as liquid and this is then pumped out of the internal battery system into external storage tanks, which decouples the capacity from the power. This enables the battery to store more chemical energy and discharge electricity for longer periods of time.
Hydrogen – Low carbon hydrogen can be stored in large quantities and converted back to electricity when needed on the grid. It could also be used directly in industry, heating and transport applications.
Hydrogen can be stored as gas in underground salt caverns. There are also considerations for hydrogen to be stored in depleted gas fields and underground aquifers. Hydrogen can also be converted to other gaseous or liquid synthetic fuels, which may be easier and cheaper to store and transport.
Thermal storage – These technologies store energy as heat in various materials such as water, concrete or rocks. The government is supporting innovation on a small scale with local thermal storage technologies. Storage of subsurface heat in underground aquifers has already been deployed oversees and now to a limited extent in the UK.
Mechanical storage – This is where electricity is converted into mechanical energy, relating to an object’s kinetic energy or gravitational position.
Getting planning consent for long duration energy storage schemes
Achieving planning consent for flow batteries and some types of hydrogen storage will be similar to the numerous applications our Energy Planning team have worked on for the more standard battery energy storage schemes, depending on the scale of the projects.
In the main, these have not required an Environmental Impact Assessment and have been dealt with by the relevant local planning authority. Key issues tend to include landscape and visual impact, noise and ecology.
The planning process for mechanical and thermal storage are likely to be more in depth and may require applicants to go through the NSIP (Nationally Significant Infrastructure Projects) process, again depending on the particulars of the project, where applicants are determined by the Planning Inspectorate.
Such applications are subject to more stringent submission and assessment requirements, and longer timeframes. With thermal storage in particular, it will be necessary to investigate impacts on hydrology and hydrogeology, as well as some of the more common planning constraints such as visual impact and local amenity.