Power supply
Scoping potential new sites Meanwhile, Rebecca Ellis, energy policy manager at the International Hydropower Association (IHA), citing the Australian National University (ANU)’s Global PSH Atlas, notes there are currently an estimated 616,000 potentially feasible off-river PSH sites globally with storage potential of about 23m gigawatt-hours. “In addition to potential new sites,” says Ellis, “existing plant modernisation can prolong the life of the assets and increase the range of flexibility services that hydropower assets can provide to the electricity system.”
“IHA are currently supporting the XFLEX Hydropower project, an EU Horizon 2020 project,” she adds. “This is a demonstration project to showcase the means in which hydropower and PSH assets can provide a range of invaluable grid services to ensure that local and regional power grids remain reliable and resilient to current and future disruptions.” Hydropower provides very low-cost electricity over its long lifetime, despite the relatively high construction costs upfront. The big questions, however, are over whether costs will continue to come down as a result of technological advances and whether business use cases can be made. For Ellis, there’s a simple answer. “Based on levelised cost of electricity (LCOE) analysis by the International Renewable Energy Agency (IRENA) from 2022, hydropower is regarded as the second-cheapest renewable energy. This is especially important when considering the long lifetime of the assets – both machinery and civil works.” However, Ellis also sounds a note of caution. “Because of the large upfront costs, investors are exposed to a significant proportion of the lifetime cost of the project before revenues commence,” she says. However, public sector financial measures to support projects, and international good practice like the Hydropower Sustainability Standard, can be used to help mitigate risk for investors.
“Lack of remuneration for the essential grid services that PSH and hydropower currently provides – and will provide in the future – is something that national governments need to address in order to help hydropower projects,” Ellis reiterates. However, “electricity markets, especially during the context of the energy transition, are immensely difficult to predict, meaning there is a lack of predictable revenue streams over the long period of project development; thereby making it difficult for developers”.
Gravity check
While PSH is firmly established, it is by no means the only game in town when it comes to energy storage solutions, particular when viewed in the longer term – the case in point being the emergence of underground gravity energy storage (UGES). Where safe and technically feasible, there is significant potential to repurpose previously operational mines – one example
World Mining Frontiers /
www.nsenergybusiness.com
being Dinorwig, a repurposed slate mining facility in northern Wales that operating since 1984, which provides a 1,728MW PSH, according to Ellis. Another example is in Estonia, where Festi Energia is in the planning phase of repurposing a mine in Ida-Virumaa County, using the limestone rubble and closed tunnels previously deployed for mining oil shale. Ultimately, it’s expected to have a capacity of 225MW and is slated to begin operations in 2026.
Noteworthy too is the Kidston project in Australia, which is currently in stage two of development and is the first energy storage project that will make use of an abandoned gold mine. It’s projected to produce 250MW and will incorporate solar PV. In the meantime, the UGES model proposed by IIASA researchers, for example, uses existing elevators to raise and lower containers full of sand. Mines are well-suited to such batteries – principally because they already have deep shafts that can be used to drop a weight. UGES generates electricity when the price is high by lowering sand into an underground mine and converting the potential energy of the sand into electricity via regenerative braking and then lifting the sand from the mine to an upper reservoir using electric motors to store energy when electricity is cheap.
The main components of UGES are the shaft, motor and generator, upper and lower storage sites, and mining equipment. The deeper and broader the mineshaft, the more power can be extracted from the plant, and the larger the mine, the higher the plant’s energy storage capacity, according to IIASA.
Energy storage in the long term The key takeaway here, however, is that while energy storage methods – such as batteries – lose energy via self-discharge over long periods; using sand enables ultra-long time energy storage ranging from weeks to even several years. As IIASA’s Julian Hunt points out, “Comparing SPHS and UGES, there are several SPHS plants worldwide, particularly in
$329bn
The value of the global pumped storage hydropower industry in 2022. Straits Research
31
The Kidston project in Australia will be the first energy storage solution to make use of an abandoned gold mine.
Genex Power
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