Energy storage | hot news from Denmark Molten NaOH:
At first sight, NaOH (aka caustic soda), with its challenging corrosive properties, would not seem to be a good candidate material for molten salt energy storage. But a Danish start-up, Hyme (a contraction of hydroxide and melt) is founded on the belief that it could be the basis of a disruptive new low-cost technology for compact high temperature thermal storage at grid scale
Hyme Energy was launched late last year by Copenhagen based nuclear power plant design company Seaborg, backed by an investment of over 10 million euro from current Seaborg shareholders.
Not lacking in ambition, Hyme hopes to have a commercial energy storage facility employing molten NaOH as the storage medium under construction within three years, and to have a pilot/demonstration plant in operation within 18 months.
It is saying it can “halve the price of long-term and large-scale energy storage facilities.” Remarkably, because of its excellent neutronics properties, Seaborg is proposing to use NaOH as the moderator in the inherently- safe next-generation reactor it is developing, the Compact Molten Salt Reactor.
This has required it to fully get to grips with the corrosion problem, using “a method of chemistry control that holds the corrosion by sodium hydroxide at bay”, and this is the core IP in the company.
Hyme has been granted the rights to mature the concept for energy storage applications and to take it from the laboratory to the global market, “leveraging several patents to deploy hydroxide salts as an inexpensive, grid-scale energy storage medium.”
The concept Hyme is proposing stores electricity as heat at 700°C. This heat could be employed in a variety of ways: CHP (Rankine cycle); heat-to-power (Brayton cycle); compact heat storage for district heating; and industrial process heat. The NaOH would be heated using, for example, surplus power from renewables. The basic configuration envisaged is the well established two-tank molten salt storage system encountered in CSP (concentrated solar power) plants.
The scaleable energy storage capacity for the Hyme technology is estimated to be from 250 MWh to 5 GWh, while heat loss is calculated to be 0.5-1% per day.
Pilot project
An important step forward was announced recently with the award to Seaborg and sister company Hyme of a public grant from the Danish Energy Technology and Demonstration Program (EUDP) to support construction of the pilot/ demo facility, the world’s first NaOH based energy storage facility.
This will be located in Esbjerg, with completion in 2023 and a total budget of 3.3 million euros (DKK 24.6million).
The project, which aims to “validate key technologies of Seaborg and Hyme outside the laboratory”, has attracted a roster of distinguished participants: Sulzer; Alfa Laval; SAN Electro Heat; Kirt x Thomsen; Aalborg University; Energy Cluster Denmark; and Esbjerg utility company DIN Forsyning, which is providing the site for the demonstration plant. “We are very happy to be the hosts of this pioneer project within energy storage and are also hoping we can together find short-cuts to bring the technology even more rapidly to market”, said Claus Nielsen, business development director, DIN Forsyning. The EUDP-financed project aims to demonstrate system and component integration of the technology in a demonstration plant that will “serve as a stepping stone for commercial
plants.” Main goals of the pilot/demo include: ● construction of a functional demonstration plant designed for scalability;
● demonstration of high temperature molten salt storage, at above 600°C;
● design, integration, and testing of all key components; and
● validation of the scalability of design and subsystems for plants with 1 GWh thermal storage capacity.
Another recent significant development was the award of a research grant to Aalborg University to develop an optimal design of NaOH-based molten salt heat store system (based on Hyme’s technology) for the continuous production of 180-220°C steam for industrial processes (eg in paper/wood processing applications). The project will be hosted by GreenLab Skive. Funding comes from the Villum Foundation, which has granted 20 million DKK to support a new national research and demonstration platform at GreenLab. Day-to-day management of the platform will be the responsibility of GreenLab and DTU (Danish Technical University). The focus of the project is the heat exchanger design, which “basically, must go from the 700°C of the NaOH storage medium to the required steam temperature in as few steps as possible, without becoming too complicated”, says Nis Benn, co- founder and chief commercial officer of Hyme. GreenLab Skive is a green industrial park, which Nis describes as “focusing heavily on developing new types of symbiosis so resident companies improve energy efficiency by utilising each other’s waste streams and also creating common value where possible (eg, building storage together and/or for multiple purposes).” During the project, Hyme plans to work with GreenLab on wider issues, exploring “how storage can also support energy planning, symbiosis and synergy between companies in the industrial park.” This is of particular interest to Hyme as their “technology is a strong fit with trigeneration – power, steam and district heating.”
Why NaOH?
“Thermal energy storage with molten salts is not new”, notes CEO and co-founder of Seaborg, Troels Schönfeldt, “but as a technology it struggles commercially due to the price of the so-called solar salts. Many alternatives have been investigated, but normally no chemist in their right mind would look at anything as corrosive as sodium hydroxide. However, in the development of our reactor, we needed to use sodium hydroxide and were forced to develop these methods.
Hyme NaOH-based energy storage, the basic concept (CHP example)
26 | January/February 2022|
www.modernpowersystems.com
“Somewhat counterintuitively, a breakthrough like this puts us in a pickle. On one hand, we cannot let it defocus Seaborg’s current mission to power regions with poor or no access to
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