| Energy storage
renewable energy sources with our Compact Molten Salt Reactor. But we also cannot simply shelve an opportunity to aid countries with access to renewables in accelerating this deployment. Thus, we decided to place the energy storage work into a sister company, so we can advance both at a fast pace.” Nis Benn emphasises three key benefits of Hyme’s NaOH based technology and says “these are the advantages we are trying to find the right market fit for”: low price of the storage medium; compactness; and high operating temperature. Thus far, the company has made quite a lot of the low price of the NaOH storage medium itself. Sodium hydroxide is a commodity produced from seawater as a byproduct of chlorine production and is therefore very much cheaper than the standard salts typically used for molten salt storage. Also, hydroxides can accommodate more heat per unit of salt, reducing the amount of salt needed. Hyme estimates that 1 GWh of molten salt storage employing nitrate salts costs around $8- 11 million for the storage medium alone. Use of NaOH reduces this cost by as much as 90%. For some projects, eg new build CSP, with an expensive steam turbine, the cost of the storage medium may be a relatively small proportion
of total costs. It however becomes more of a consideration for retrofit projects, where the steam turbine and other equipment is already in place, and for heat only applications where there is no power generation.
Compactness is particularly important to utilities based close to cities, “which don’t have that much space to expand if they want to store energy”, says Nis. “We can fit in most places because we take up significantly less space” – perhaps 30% or even less of that required for an installation using conventional molten salt technology – and because the system is more compact there are savings in materials and equipment costs, eg tanks.
“Molten hydroxide has excellent capabilities when it comes to storing vast amounts of heat”, Nis observes. For example, a 1 GWh NaOH based facility is estimated to occupy no more space than the plot of a family house. And then there is what Nis calls the “temperature advantage” of sodium hydroxide. The melting point of NaOH is 318°C so the lowest temperature of the molten NaOH in the Hyme storage system will probably be around 350°C, while the maximum is 700°C, as already noted. “So that gives us a temperature span of
350°C within which we can heat our salt”, Nis explains. For comparison, nitrate salts “can go from around 290°C, maybe 300°C, to somewhere between 500°C and 550°C and usually they don’t go to 550°C because they decompose at 565°C”, so “they have an optimistic temperature span of around 250°C’’, Nis suggests. “That’s one of the reasons why you need more nitrate salt to store the same amount of energy and why our technology is more compact.”
He also mentions a further benefit of NaOH: it has better heat transfer characteristics than nitrate salts, “so, basically, it’s easier to get your heat exchanger to work.”
Another key aspect of the temperature advantage is inherently increased efficiency arising from the high operating temperature attainable with molten NaOH, raising the power output of a typical CSP steam turbine by perhaps 5% relative to a nitrate based system. This would “give you 5% more revenue from exactly the same input and the same capital investment, which would of course be of huge potential value to the CSP sector.” So, it’s “one of the many things that we’ll be exploring over the next year and a half before we choose how we will actually go to market”, says Nis.
LDES Council: leading the charge for novel long duration technologies
Launched at COP26, the CEO-led Long Duration Energy Storage Council’s stated aim is to provide “fact-based guidance to governments and industry.” In November, the Council published its first report, jointly authored with McKinsey, focusing on the role of LDES in electrical power systems
The report (Net-zero power: long duration energy storage for a renewable grid) includes analysis based on more than 10 000 data points submitted by LDES Council members outlining the cost and performance of their technology.* The data was aggregated and processed by an independent third-party team. Council members provided cost and performance data for two projected trajectories for how these metrics would change from a “progressive” to a “central” scenario: progressive scenario, reflecting ambitious cost-reduction trajectories and learning rates; and central scenario, reflecting conservative cost-reduction trajectories and learning rates. The main findings can be summarised as
follows:
The world is not on track to limit the rise in global temperature to 1.5° Celsius. To achieve the commitments made in the Paris Agreement, significant efforts must be made to reduce emissions across all sectors. The power
sector, which accounts for roughly one-third of global emissions, will be central to global decarbonisation, with many suggesting that it will need to achieve net-zero emissions by 2040. As a result, innovative solutions will be essential to meet three critical challenges for the power sector: tripling the amount of electricity produced to meet rising consumption; transforming the power system from fossil-powered generation to renewables; and meeting the social and economic cost of the transition. Based on the more than 10 000 cost and performance data points, the study shows that long duration energy storage technologies (LDES) can play a crucial role in helping create the system flexibility and stability required by an increasing renewable share in power generation, alongside other technologies such as lithium-ion batteries and hydrogen turbines.
LDES encompasses a range of technologies that can store electrical energy in various forms
for prolonged periods at a competitive cost and at scale. These technologies can then discharge electrical energy when needed — over hours, days, or even weeks — to fulfill long-duration system flexibility needs beyond short-duration solutions such as Li-ion batteries.
The various LDES technologies are at different levels of maturity and market readiness. The report focuses on the ‘novel’, relatively nascent, mechanical, thermal, chemical, and electrochemical storage technologies, rather than li-ion batteries, dispatchable hydrogen assets, and large-scale above-ground pumped storage hydropower (PSH). The rapid integration of large RE capacities with their inherent variability creates large challenges for the power system, including potential imbalances in supply and demand, changes in transmission flow patterns, and the potential for greater system instability as the built-in inertia provided by fossil generation is removed. All of these call for new solutions to
www.modernpowersystems.com | January/February 2022 | 27
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45
