Recent developments to do with pumped hydro, liquid air and kinetic energy storage technology hold out the promise of inexpensive, widely available energy storage. If realized, deployments could be the catalyst that fuels growth of solar, wind and other emissions-free, renewable energy capacity to new, significantly higher, heights, proponents say.

Pumping and storing water from lower to higher elevations and then releasing it to drive turbine generators is one of the oldest, most efficient and widely used means of generating baseload electricity known. An Australian National University (ANU) research team found no less than 530,000 potential short-term, off-river pumped-hydro energy storage sites worldwide that could be used to support low-cost, renewable energy zones and power grids. “Pumped hydro accounts for 97 percent of energy storage worldwide, has a typical lifetime of 50 years and is the lowest cost large-scale energy-storage technology available,” pointed out Bin Lu, a project team member and PhD candidate at the ANU Research School of Electrical, Energy and Materials Engineering (RSEEME).

Another promising large-scale energy storage technology recently emerged in news reports, one that, akin to pumped hydro, is based on fundamental principles of Newtonian physics taught to undergraduate college students. About an hour’s drive south of Milan, Italy, Energy Vault intends to use cranes to lift 35-metric ton bricks from ground level to build a tower, then release the stored potential energy by lowering them again to drive turbine generators.

In a third instance, Highview Power is out to prove that its liquid air energy storage systems (LAES) can provide gigawatt-hours (GWh) worth of cheap, highly efficient energy storage for five-10 hours per day. “At giga-scale, energy storage resources paired with renewables are equivalent in performance to—and could replace—thermal and nuclear baseload in addition to supporting the electricity transmission and distribution systems while providing additional security of supply,” according to the company.

Cheap, reliable pumped hydro energy storage sites abound

An untold wealth of cheap, efficient pumped hydro energy storage sites exist worldwide, sites that could be linked with solar or wind power systems to create emissions-free electricity grids, according to the ANU’s latest, most ambitious, audit. The findings run contrary to conventional wisdom.

“The perception has been there are limited sites for pumped hydro around the world, but we have found hundreds of thousands,” said lead researcher Matthew Stocks, PhD and Research Fellow at the ANU College of Engineering and Computer Science. “Only a small fraction of the 530,000 potential sites we’ve identified would be needed to support a global, 100 per cent renewable electricity system. We identified so many potential sites that much less than the best one per cent will be required,” Stocks highlighted.

Significantly, the pumped-hydro energy storage sites the ANU team identified don’t necessarily need to be located near rivers or other waterways. According to the researchers’ analysis, their terrain is suitable for the construction of lower and upper water reservoirs, which would then be connected to tunnels or conduits to pump water up-slope and then down to drive hydroelectric generators to provide baseload grid electricity, or released on-demand when grid conditions warrant.

Solar or wind power generation could be used to pump the water from the lower to the upper reservoirs, thereby storing energy cheaply and efficiently. High-voltage transmission lines could be built to deliver electricity, thereby creating zero-emission grids , according to the research team.

Creating renewable energy zones and zero-emissions power grids

There are many opportunities for renewable energy zones (REZ) to be created around the world where there wind, sun and pumped hydro opportunities are good, Andrew Blakers, research team member and director of the ANU Centre for Sustainable Energy Systems, said in an interview. They include areas of U.S. states, such as Arizona, Colorado and Texas, as well as some 3,000 others across Australia.

“The cost of transmission can then be shared across wind, solar and pumped hydro. The pumped-hydro storage ensures that the power line runs at full load even in the middle of the night, which reduces transmission costs and also allows existing transmission to be much better utilized…We provide a geographical survey of potential sites, and the constraints we apply [set aside] national parks or urban areas,” Blakers explained.

“As we state in the disclaimer, geological, environmental and other factors will rule out many sites. However, there are so many sites that we can afford to be choosy—fewer than 1 percent of sites will need to be developed to support 100 percent renewables. Costs for transmission, water supply and road-access are significant, but [they] are not the dominant costs for most sites. The larger the site, 50 or 150 GWh for example, the less important are these costs.”

Typically, the off-river, pumped-hydro energy storage sites identified in the study could dispatch maximum power anywhere from five to 25 hours depending on the size of the reservoirs, Blakers continued. Construction methods are well known and proven and pumped hydro provides fast energy response of just a few minutes. Furthermore, the water required for pumped hydro energy storage paired with solar PV or wind power generation would require much less water than a fossil fuel power plant as they don’t require water for cooling, Blakers noted.

Maps showing the locations of potential STORES (Short-Term Off-River Energy Storage) sites, along with more regarding the research team’s analysis are available at: http://re100.eng.anu.edu.au/global/.

Raising bricks to build energy-storage towers of power

Akin to Highview’s LAES technology, Energy Vault’s kinetic energy system is inherently scalable with excellent economies of scale. The amount of energy stored depends on the number and mass of the bricks and the height to which they are raised, then lowered.

At around a few U.S. cents per kilowatt-hour (kWh), the cost of energy storage over the lifetime of the “tower of power” system could be seven times lower than that for equivalent lithium-ion battery systems , according to a news report.

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Even with the rapid decline in lithium-ion battery energy storage, it’s still difficult for today’s advanced energy storage systems to compete with conventional, fossil-fuel power plants when it comes to providing long-duration, large-scale energy storage capacity , Energy Vault co-founder and CEO Robert Piconi was quoted by Fast Company. Energy Vault won Fast Company’s 2019 World Changing Ideas Awards in the Energy category.

The CEO says Energy Vault’s technology fulfills that need, and in a way that’s much more environmentally friendly. “Now you can couple PV and low-cost wind with our storage and for the first time replace fossil fuels with renewables 24 hours a day,” he was quoted.

Highview Power’s gigawatt-scale, cryogenic energy storage technology

London, U.K.-based Highview Power sees similar potential for its LAES technology. Management recently announced the company entered into a joint venture with multinational engineering, procurement and construction (EPC) company TSK to develop large-scale LAES projects in Europe (Germany, Italy and Spain), the U.K. and the U.S., as well as in Nigeria and various West African countries, such as Mauritania and Senegal, CEO Javier Cavada told Solar Magazine.

When it comes to the levelized cost of energy (LCOE), that for Highview’s LAES is less than half that for equivalent lithium-ion battery energy storage systems, according to Cavada. Lithium-ion battery systems can do an excellent job of providing very fast response (in milliseconds) and highly efficient energy storage capacity, but only for up to four hours. Due to the nature of the technology, the operations and maintenance costs of systems rise quickly beyond that, which makes the economics less and less feasible, Cavada explained.

Highview’s LAES can resolve two big issues constraining faster growth of solar, wind and other emissions-free energy resources, Cavada continued. “LAES can give solar and wind more room for growth. Today, I think renewables provide around 17 percent of global power generation capacity. Just to get to 50 percent would require three times more than is installed today. Reliable, large-scale, long-duration storage is the missing piece of the puzzle,” Cavada asserted.

Highview’s standard system design provides 50 megawatt-hours (MWh) of energy storage capacity for 8 hours a day. Its systems can be run for 10 or 20 years and, in large part, be managed remotely with much less in the way of operations and maintenance costs, the CEO pointed out.

Itemizing the attributes of Highview’s LAES

Ramping up from zero to 100 percent operating power capacity comes in under 10 seconds, which Highview demonstrated in Manchester, according to Cavada. In the fastest moving electricity markets, Highview can readily pair its LAES with flywheels or lithium-ion battery systems to achieve instantaneous response, he added.

Adding to the attractiveness of LAES, the method and technology used to compress air to liquid form and distribute it are well known and used widely in industry and commerce, Cavada pointed out. That makes for easier, faster systems deployments and integration, which in turn lowers overall deployment costs.

“There are millions of liquefaction stations that operate in a temperature range identical to what we need,” including at hospitals and by industrial and manufacturing companies that make use of liquid oxygen or nitrogen, Cavada said. “And when you cool down the air, you also clean it because you remove the CO 2 , which has a higher liquefaction point than oxygen,” he added. “There are millions of liquefaction stations that operate in a temperature range identical to what we need,” including at hospitals and by industrial and manufacturing companies that make use of liquid oxygen or nitrogen, Cavada said. “And when you cool down the air, you also clean it because you remove the CO, which has a higher liquefaction point than oxygen,” he added.

That CO 2 can be used, and sold as a by-product to produce soda pop and other types of carbonated beverages, for example, he pointed out. Highview is working with a U.K. brewery in south Wales to do just that as part of one of the projects in its development pipeline, Cavada added.

The company sees a variety of use cases in which its technology can be readily applied. “We have a full, ancillary [grid] services model, like lithium-ion batteries, but much larger, so it also has much better potential for capacity markets. We can really make wind or solar power fully dispatchable 24x7x365—that can only happen if you have enough storage capacity. The same goes for solar. We have several projects in development in Italy,” Cavada said.

LAES’ value proposition is different in developing or lesser developed countries. There, Highview’s technology can substantially boost national and rural electrification initiatives, as well as make substantial contributions to the achievement of national and international renewable energy and climate change goals.

On a mission to achieve the emissions-free, renewable energy transition

LAES can also enhance natural gas, or even coal-fired power stations, which could prolong their lives and prolong a transition to zero-carbon energy. The technology can be installed to run in sync with natural gas peaker plants, for instance. In such situations, the natural-gas peaker would only need to be run when a genuine crisis existed, Cavada explained.

That runs contrary to the company’s guiding and informing mission and strategy, however. “We can store and deliver electrons from any generation asset, renewable or not, but we’re here to accelerate growth of renewables and displace fossil fuels and nuclear. That’s our target. We aim to make more wind or solar happen. Many oil and gas companies [are] fully aware of that and we are working with them to do so.”

Cavada added that Highview and TSK executives have a meeting with Shell at its global headquarters in the Netherlands in a couple weeks. “They’re fully aware of the need for more renewables now. The biggest solar company in Africa today is Total. We’re going to help these companies make the energy transformation happen,” Cavada said.

Government energy authorities and utilities in a variety of countries are showing strong interest in Highview’s LAES, he added. The company has designed a 50 MW/400MWh plant coupled to a wind power farm as part of a feasibility study in the U.S.. Highview has already signed up a utility off-taker and expects to be able to announce the signing of a deal soon.

Having deployed two, smaller-scale, systems in the U.K., Highview is also working to develop a 50-MW/250-MWh system there. “The beauty of this technology is that you can add to it easily—increase a system’s energy storage capacity from 8 hours to 10 hours, for example. It’s akin to hydroelectric power in that sense,” Cavada concluded.

* Cover photo: Highview Power