This month in our Back to Basics series, we uncover the ways in which energy generated by wind and solar farms can be stored and how this technology will shape the future of our energy systems.
How is energy stored?
‘Applications are becoming more diverse and widespread geographically with the growth of variable wind and solar energies, decentralisation of the power system and the need for resilience in the network.’ [1]
Energy storage refers to a broad family of technologies with varying characteristics that affect the charging and discharging rates, and the scale or form of energy that may be stored [2]. Often, energy is converted from one form into another during the storage process.
Energy storage technologies can be grouped into five broad categories [1]:
- Batteries
- Thermal
- Mechanical
- Pumped hydro
- Hydrogen
Currently, pumped hydro is the most prominent energy storage technology worldwide [2].
Why do we need to store energy?
- Geopolitical and economic security
- System resilience and stability
- Meeting demand and efficient network utilisation
Primarily, energy storage technologies have been developed to reduce imbalances between energy demand and energy production. Storage makes renewable sources of power such as wind and solar PV more accessible and reliable. Generally, the maximum output of solar energy is during the middle of the day. However, the biggest consumer demand peaks are in the morning and evening when people are in their homes. In addition, the winter months see a significant increase in daily demand, but this is a time of year when it is more likely to be overcast and the daylight hours are reduced. Traditionally, fossil fuel plants are engaged to help manage peaks and troughs in demand for electricity, but as we grow ever closer to net zero target dates, we must ensure that flexible low carbon solutions are available instead [1, 3].
Figure 1. Renewable energy icon. [9]
What does the future of energy storage look like?
Smart grid technology has become an important focus for energy systems of the future. Within this, the grid is becoming increasingly decentralised. This means that there is an increase in small scale energy systems, such as rooftop solar, which opens the opportunity for excess energy to be stored locally and fed back into the grid as required [4]. In this fashion, smart grid technology monitors and controls the flow of electricity, which allows for a more sustainable distribution of energy. To some extent, this strategy can reduce the need for investments in expensive transmission infrastructure developments. The flexible grid structure also allows consumers the opportunity to invest in renewable energy systems for their homes and receive a return from excess power that is produced. However, a smart grid structure calls for increased cybersecurity to ensure that digitisation of energy systems remains safe for users [5].
Last year, the UK’s planning system listed over 1,000 battery projects (93 already operational) which means that many of these will become operational in 2024 and beyond. Batteries fit well into the smart grid structure, providing crucial decentralised grid links. Lithium-ion facilities are currently the most economically viable option for localised grid developments. This type of battery has already seen immense growth with the increasing accessibility of electric vehicles, which is only set to accelerate further. However, some sources state that lithium-ion batteries carry high costs storage costs and self-discharge, making them unsuitable for the long-duration storage that will be required to support seasonal cycles of renewable energy production [6, 7]. Batteries are also prone to overheating which is a real safety concern for large scale facilities.
By 2050, it is estimated that anywhere between 11-56TWh of large-scale non-battery storage may be required [8]. A number of other technologies, more or less suited to utility-scale, are contending for a place in supporting the renewable grid of the future. These include:
- Compressed air energy storage including isothermal deep ocean compressed air [7]
- Mechanical gravity energy storage
- Flow batteries
- Hydrogen energy storage
Conclusions
The ramping up of renewable energy facilities may be explained as a shift to decentralised energy generation. Energy storage plays a crucial role in the renewable energy transition, by addressing intermittency, managing peak demand, improving grid stability and reliability, and facilitating the integration of small-scale renewable energy systems into the grid [1]. Smart grids will become commonplace as we approach net zero deadlines.
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References:
[1] The different types of energy storage and their opportunities, J. Spencer Jones (14 May 2024), Accessed on: 11/04/2024, Available at: https://www.smart-energy.com/industry-sectors/storage/the-different-types-of-energy-storage-and-their-opportunities/
[2] Energy Storage Roadmap, Supergen & Birmingham Energy Institute, December 2020, Accessed on: 11/04/2024, Available at: https://ukesr.supergenstorage.org/chapters/energy-storage-technologies
[3] What is battery storage?, National Grid, Updated 9 May 2023, Accessed on: 11/04/2024, Available at: https://www.nationalgrid.com/stories/energy-explained/what-is-battery-storage
[4] Energy Storage 2023: State of the Art and Trends for the Future, Future Electronics, 20 March 2023, Accessed on: 11/04/2024, Available at: https://www.futureelectronics.com/blog/article/energy-storage-state-of-the-art-and-trends-for-the-future/
[5] Smart grid and smart meter: Business trends and opportunities, Future Electronics, 25 January 2023, Accessed on: 11/04/2024, Available at: https://www.futureelectronics.com/blog/article/smart-grid-and-smart-meter-business-trends-and-opportunities/)
[6] The Future of Energy Storage, MIT Energy Initiative, https://energy.mit.edu/research/future-of-energy-storage/
[7] Isothermal Deep Ocean Compressed Air Energy Storage: An Affordable Solution for Seasonal Energy Storage, J. D. Hunt et al., 29 March 2023, Energies, 16(7), 3118, Accessed on: 11/04/2024 https://www.mdpi.com/1996-1073/16/7/3118
[8] UK needs at least 50GW of energy storage for net zero by 2050, National Grid ESO says, C. Murray, 19 July 2022, Accessed on: 11/04/2024, Available at: https://www.energy-storage.news/uk-needs-at-least-50gw-of-energy-storage-for-net-zero-by-2050-national-grid-eso-says/
[9] Logo Renewable Energy, M. Maecker, 5 May 2020, Accessed on: 11/04/2024, Available at: https://commons.wikimedia.org/wiki/File:Logo_Renewable_Energy_by_Melanie_Maecker-Tursun_V3_bgGrey.svg
