What is Higher Ground NI?
The Higher Ground project is being progressed by Mutual Energy and is exploring the potential for developing a local Pumped Hydro Energy Storage (PHES) scheme in Northern Ireland.
Already used successfully elsewhere in the world, PHES is a form of clean energy storage that is ideal for energy systems that are already harnessing wind and solar power.
The technology is designed to absorb surplus renewable generation at times of oversupply for later release when the output from wind and solar is low. This would help improve Northern Ireland’s energy security and mitigate renewable curtailment issues. Essentially the scheme would act as a large-scale, water-based ‘battery’ for storing renewable energy.
While currently no PHES projects exist in Northern Ireland, it is an established technology globally, including in Great Britain and the Republic of Ireland, accounting for over 94 per cent of installed electricity storage capacity worldwide (International Hydropower Association), and can offer a wide range of benefits to the electricity system.
Feasibility study
Supported by a team of experts, phase one of the Higher Ground project is a feasibility study expected to last two years and will examine the potential for developing Pumped Hydro Energy Storage in Northern Ireland.
This initial study will provide a detailed understanding of the engineering, financial and regulatory viability of the scheme, including its suitability for Northern Ireland, as well as the potential benefits it could offer in supporting decarbonisation and wider ‘green’ economic growth.
The outcome of the study will be used to inform the Northern Ireland Executive and the Utility Regulator and to help Mutual Energy determine if the project merits being further progressed.
If the results of the feasibility study are positive, any future development of the scheme would be subject to the relevant planning, consulting and permitting requirements for this type of large-scale energy infrastructure.
FAQs
Pumped hydro energy storage is a form of low carbon energy storage that is ideal for energy systems that have a growing renewable energy industry.
It can be thought of as a water-based ‘battery’ that can be used to store otherwise surplus renewable generation for later release when it is needed by the energy system. The technology utilises two water reservoirs each at a different elevation. When there is surplus renewable generation and the price of electricity is low, water can be pumped up to the upper reservoir where it is stored for future use. It can then be released and flow, by gravity, from the upper to the lower reservoir powering turbines to generate electricity, reducing the cost of electricity when renewable output is low.
The energy storage capacity depends on the size of the scheme’s reservoirs, while the amount of power generated is linked to the size of the turbine.
Pumped Hydro Energy Storage is an ideal storage solution for electricity system operators seeking to integrate increasing volumes of renewable generation technologies.
As a storage technology, it is not subject to increasing degradation with use, unlike lithium-ion batteries and other chemical energy storage technologies. This means development of a PHES scheme can provide energy storage and other critical system services across a life span of well over fifty years.
It is therefore not surprising that it is currently the most used energy storage technology globally. The International Hydropower Association (IHA) estimates that pumped hydro projects worldwide store up to 9,000 gigawatt hours (GWh) of energy, accounting for over 94 per cent of installed global energy storage capacity, well ahead of lithium-ion batteries and other storage technologies
Higher Ground is an exciting project and could provide a technical solution to some of the major challenges facing Northern Ireland in its efforts to decarbonise. If built, the scheme would have the ability to store at least circa 3GWh of otherwise wasted renewable energy.
During periods of low renewable output, at the flick of a switch, this energy could be released to provide carbon free electricity, offsetting the need to run carbon emitting thermal generation. Using the water stored in the upper reservoir of the scheme would release a volume of energy equivalent to the power consumption of 400,000 homes for a day.[1]
The scheme would then refill during the next period of high renewable output, absorbing surplus renewable energy from wind and solar generation.
Development of the project could provide significant stability and flexibility to the energy system, reducing renewable curtailment and improving the security of NI energy supplies.
Other major advantages of the scheme include:
- Its large-scale storage capacity can help balance intermittent renewable energy resources with electricity demand, assisting the delivery of a constant and reliable decarbonised power supply to Northern Ireland.
- As a well-established, proven technology it can support delivery of Northern Ireland’s emission reduction targets and help accelerate the transition towards a cleaner and more sustainable energy sector by:
- Increasing renewable energy output by reducing curtailment
- Facilitating the further integration of renewable generation technologies
- It has an impressive life span of well over fifty years, longer than most other storage technologies.
- It offers long charging and discharging durations of more than 6 hours
- Its storage capacity will not reduce with use – i.e. as a technology it is not subject to cycling limitations or degradation like electro-chemical based storage solutions
- It has the potential to deliver a lower lifetime cost per MWh than other storage technologies
- If the scheme is feasible, and if delivered by Mutual Energy, its operating profits would be reinvested to further the long-term interests of Northern Irish energy consumers.
SONI as the electricity system operator has highlighted a need for substantial investment in energy storage to deliver upon Northern Ireland’s emission reduction targets in its Tomorrow’s Energy Scenarios 2023 report.
As part of the feasibility study, the optimal power rating for the scheme will be investigated, as well as options to increase its energy storage capacity. Increasing storage capacity will help reduce the cost per MWh of developing the scheme while, at the same time, increasing the benefits it can deliver to the energy system.
[1] Assumes an annual average consumption of 2700kWh per household.
The majority of Pumped Hydro Energy Storage (PHES) schemes utilise freshwater. This however significantly restricts the opportunities for their development.
In the case of Northern Ireland, a freshwater scheme is unlikely to be feasible due to the remote locations of potential sites and their poor grid infrastructure. The use of seawater however offers the possibility of developing a scheme in proximity to the Greater Belfast conurbation, at an already established major electrical hub.
The core principles of a seawater Pumped Hydro Energy Storage scheme are the same as freshwater. However, the salinity of the water means that the scheme will need to be capable of operating within a more corrosive marine environment.
Tidal barrages, such as Rance Tidal Power Station in Northern France already operate turbines to generate electricity in such environments, while corrosion protection is used to protect offshore wind farms and tidal generators, such as the MeyGen project in Scotland.
Seawater based PHES schemes are also currently being investigated in other parts of the world, including Australia, Chile, the Philippines and the United States.
Given the substantial benefits a Pumped Hydro Energy Storage scheme could deliver to Northern Ireland, in terms of accelerating the decarbonisation of our economy and improving the security of our energy supplies, it is important that the potential opportunity presented by the Higher Ground project is properly investigated.
There are a diverse range of Pumped Hydro Energy Storage schemes operating across the UK and Ireland, Europe and globally. The UK has several notable hydropower projects, including the Dinorwig Power Station in Wales, which is one of the largest pumped-storage hydroelectric facilities in Europe with a maximum power rating of 1,728 MW.
In Ireland the Turlough Hill Power Station in Co Wicklow, operated by the Electricity Supply Board (ESB), has played a crucial role in balancing supply and demand on the Irish electricity grid for almost 50 years. It provides up to 292MW of rapid-response electricity during peak demand and helps integrate renewable energy sources by storing surplus energy.
Seawater based Pumped Hydro Energy Storage projects are less common with the most notable being the Okinawa Yanbaru Seawater Pumped Storage Power Station in Kunigami, Okinawa, Japan operated by the Electric Power Development Company. The Okinawa station was the world’s first facility using seawater and served as a pioneering project demonstrating the feasibility of seawater-based schemes. Other seawater based projects are currently in development including;
- Repower Energy Development Corporation (REDC) is developing a 320 MW seawater pumped storage facility in Real, Quezon in the Philippines. This project, in collaboration with Austria-based Gugler Water Turbines, will utilize the coastline for its lower reservoir, marking a significant advancement in the region’s renewable energy infrastructure
- The Espejo de Tarapacá project in Chile involves a 300MW project pumping seawater from the Pacific Ocean to two inland reservoirs at 600m above sea level.
- Oceanus Power and Water, in partnership with EDF, is developing a combined pumped hydro storage and desalination system in the Andes region. This system will use seawater to generate hydropower during peak demand and produce freshwater via reverse osmosis, powered by wind and solar energy. They have also identified several viable locations for this integrated system in the US, including Southern California, Puerto Rico, and Hawaii.