Text by Daan Marselis, Trouw
Groningen Company Builds a ‘Reservoir’ for Energy Storage
Ocean Grazer is developing a ‘battery’ that can store large amounts of energy using hydropower.
Frits Bliek has his eye on three former sand excavation sites—three massive pits in the ground that have now filled with water. He’s not yet revealing the exact locations, but these pits make the ideal test sites for his Ocean Battery: a type of hydropower plant designed for areas without mountains but with plenty of surface water or open sea—a country like the Netherlands, for example.
Hydropower energy, also known as ‘pumped hydro storage,’ is a proven method for storing energy. Europe has traditionally been a leader in this, thanks to reservoirs in the Alps, Scandinavia, and Spain. The technology is relatively inexpensive and fully developed. It works as follows: On days with abundant sunshine and wind, you pump water into a high-altitude reservoir. On dark winter days, you release the water, which then rushes past a generator, producing electricity. Pumps for pushing water uphill have existed for decades, as have turbines that generate energy from the downhill flow of water. However, there is a problem: in its current form, hydropower energy is difficult to scale up. Dams must be custom-designed to fit between mountains, and building a large reservoir can quickly cost several billion euros. Additionally, energy is needlessly lost due to evaporation from open reservoirs. A large part of Europe is also relatively flat, making it challenging to build a reservoir between gentle slopes.
Three Components
With the invention from Bliek’s company, this is now possible. He hopes to prove this in one of these old sand excavation sites. Once the permits are in place, his company, Ocean Grazer, can begin constructing a prototype battery. The prototype consists of three components: a horizontal underground tunnel containing water at a depth of 150 meters, a vertical flow pipe, and a flexible water bladder located on the floor of the sand excavation—underwater and thus conveniently out of sight for local residents and visitors.
When energy prices are low, pumps push water from the tunnel into the higher-placed bladder. When electricity prices are high, water flows down through a generator in the vertical pipe. The electricity generated can then be sold back to the grid. It is a closed system, so water cannot evaporate. The water is also treated to remove any organic material, which helps minimize energy loss and keeps maintenance costs low. Approximately 80% of the energy stored can be recovered.
A small version of the Ocean Battery was tested in 2022 in the Eemshaven. For the new test, Bliek wants to build a full-scale version of the battery. The tunnel will have a diameter of 15 meters, but Bliek is keeping the length of the tunnel confidential for now, as it is part of a patent application.
The battery can eventually be as large as the customer desires. This can be achieved by using larger tunnels or connecting multiple tunnels to create an increasingly long water reservoir. The longer the tunnel and the larger the bladder above, the more water can be stored, and thus more energy can be stored in the battery. It is somewhat similar to the mega-battery recently announced by Tennet, but in the form of water storage.
Bliek believes his hydropower battery can compete well with lithium-ion batteries. “Our battery doesn’t require critical metals that are sometimes difficult to obtain, like lithium, cobalt, or nickel found in chemical batteries. We use water and gravity, creating a form of energy storage that the whole world can benefit from,” says Bliek.
His goal is for humanity to have an abundant supply of energy even after the fossil fuel era, but with clean energy from renewable sources like wind and solar.
Energy storage is a crucial link for bridging periods of unfavorable weather, such as windless periods or cloudy days. In a future power grid that relies heavily on solar and wind energy, matching supply and demand becomes much harder. Currently, a gas-fired power plant can ramp up on demand when there is a higher need for electricity; that luxury will soon be gone.
Flywheels, batteries, and forms of ‘mechanical energy storage,’ including hydropower, must provide that flexibility in the future, alongside nuclear energy and long power cables connecting EU countries. Batteries can supply electricity for a maximum of 4 hours; an Ocean Battery can supply electricity for at least 8 to 10 hours, says Bliek.
Energy companies and traders can make money by buying electricity when it is cheaply available and selling it again when prices rise. But for the energy storage market to grow rapidly, the technology used to store energy needs to become cheaper, according to a report from the Energy Transition Expertise Centre (Entec), co-authored by the research institute TNO.
Conventional hydropower plants are currently twice as expensive per stored megawatt-hour as lithium-ion batteries, Entec researchers calculated. However, these are custom-built hydropower plants designed to accommodate the shape and height of certain mountains, says Bliek. He wants to create a hydropower battery that is fully standardized and, in principle, applicable anywhere.
He expects the construction costs for the Ocean Battery to be roughly comparable to those of lithium-ion batteries, “with the important difference that lithium-ion batteries need to be replaced after 5,000 to 10,000 charge cycles, while our Ocean Battery can be charged an unlimited number of times and thus last for decades without major costs.”
“It looks much better if you install the bladder on the lakebed because then you’ll have a few ducks swimming above it.”
Promising
The planned practical test in the sand excavation is particularly important for Bliek to demonstrate that this calculation is correct. “We want to show potential investors and energy companies that we can stay within budget,” says Bliek.
The development of the Ocean Battery dates back to 2018, when researcher Wout Prins from the University of Groningen invented a device that could generate energy from ocean waves. Hence the name ‘Ocean Grazer.’ The university still holds a quarter of the company’s shares.
Part of Prins’ design included a plan to store energy in the seabed. This form of energy storage seemed the most promising, and so Bliek and his colleagues decided to continue with it.
The storage market needs to grow rapidly in the coming years, says Bliek, pointing to a chart from the European Association for Storage of Energy. Currently, there is about 80 gigawatts of storage capacity in the EU. To meet the EU’s climate goals, that needs to reach about 200 gigawatts by 2030 and around 600 gigawatts by 2050, according to the industry association. Nearly half of that could be provided by hydropower, says Bliek. Lithium-ion batteries and other forms of energy storage will still be needed.
In recent years, Bliek and his team have developed the Ocean Battery for use in offshore wind farms. They could be buried near the wind turbines and use the same power connection as the wind farm. But now, he is preparing the practical test in the sand excavation with energy company RWE, which has made Bliek think.
He surveyed the number of lakes in Europe—more than 500,000 in total. A small portion already generates sustainable energy, about 2,000 in total. “If we equip all of them with an Ocean Battery, that would provide 100 gigawatts of storage capacity,” he says.
“We want to show potential investors and energy companies that we can stay within budget.”
The plan now is to further develop the battery for use on land first. “Installation at sea is really step 2,” says Bliek. However, he wants to stick to installation ‘underwater.’ “It looks much better if you install the bladder on the bottom of a lake because then you’ll just have a few ducks swimming above it,” he says.
There will indeed be a bladder on the lakebed. The effects on the lakebed ecosystem need to be studied. “In the first test in the Eemshaven, the edges of the bladder turned out to function as an artificial reef, where seaweed and mussels settled. Starfish feasted on this banquet. It’s possible that the bladder will actually enhance marine life.”
More Attention
The coming months will be crucial for Bliek and his team, as he needs to get local residents, municipalities, provinces, landowners, and investors on board with his plans. “With an underground hydropower battery, we’re really doing something new,” says Bliek. If all goes well, the first real Ocean Battery can be built in 2025, so the test setup can be operational by 2026.
He hopes the test will also generate more attention for this form of mechanical energy storage. Currently, energy companies and governments are mainly looking at conventional batteries, which rely on chemical substances and critical metals, the future supply of which is not always certain. “A lot of money is currently flowing abroad for these battery technologies because that’s where the raw materials and battery cells come from, whereas our battery can simply be made in the Netherlands.”
Source: Daan Marselis, Trouw