From pv magazine 08/2021

Energy storage remains one of the big challenges of the 2020s, as the adoption of renewables, the cheapest and most sustainable form of power generation, continues to become the norm.

A default approach to storing these intermittent energy sources, however, is less clear. Long term storage continues to require longer term for economic viability and market presence. Battery storage dominates thinking today, while the possibility of hydrogen as a viable solution of the future is a goal, but not yet a reality.

Thermal energy storage (TES) offers a decarbonization route, and electrothermal storage offers clear advantages in terms of high energy density and longer duration. Despite the feeling that it will be an indispensable part of the overall storage market, especially with the potential provision of heating and even cooling, commercialization is slow.

Ignition path

The estimated future market for thermal energy storage shows that billions are on the table to support renewables. The International Renewable Energy Agency (IRENA) estimates a 2027 global market at $ 10.1 billion. In its November 2020 report, IRENA noted that the global TES market could triple in size by 2030, with more than 800 GWh installed, compared to 234 GWh of total installed capacity in 2019, mainly in solar towers and concentrated molten salt solar installations. . IRENA also noted that technological developments could “unlock rapid growth in the deployment of TES”.

Raymond Decorvet, senior account manager at MAN Energy Solutions (MAN ES) in Switzerland, told pv magazine that there is insufficient investment in all areas of energy storage, including TES. Of course, this limits new ideas, innovations and concepts.

“Everyone is now investing in photovoltaic or wind power. We already have a surplus of power in the Nordic countries. We pay duress payments – we all know that. Said Decorvet.

“Why is there no investment in energy storage? The most damaging problem facing power generation today is lack of storage. Big investments in storage today will pay off when the gold nuggets of photovoltaic and wind power are gone. It can’t be batteries – they just aren’t durable in my eyes. Fully durable options that last 50 years are a must. “

In Europe, the main network operations – classified as distribution system operators (DSOs) and transmission system operators (TSOs) – are not allowed to build storage other than battery energy storage systems. (BESS) under the current rules. This prevents a large investment in alternative storage options.

“Any other good storage, more durable storage, is not allowed to be built. The question is, why? Decorvet asked. “We need politicians in Brussels to build more than just batteries. If investors are still trying to invest in PV or wind, and they are not already, these new investors will fall into second place. If they invest in storage, their time will come. TSOs and DSOs will love it: you can integrate, sell, then finally, when policies change, even sell storage to grid operators. They will pay for it. If I were an investor, I would invest in storage.

Hot competition

Jonas Eklind is the CEO of Azelio, a Swedish manufacturer of Stirling engines that focused on TES solutions in 2016. Eklind believes the best design for long-term storage is thermal.

“The basic idea I had, and the company had, was to create long-lasting energy storage for distributable renewables, and an optimized solution for everyday cycling. To do this, the best design for a long life is a thermal energy storage system.

Eklind, former CEO of Swedish battery maker Nilar, said the problem with battery storage is duration and scale.

“You can’t combine batteries to increase the duration because of the cost,” he explained. “If you double the duration [of storage], you double the cost. Triple duration, triple the cost. It’s completely different from thermal storage.

With sustained electricity production from TES solutions, the cost of storage would be “extremely lower” compared to batteries. Yet batteries currently dominate the storage market.

From prototype to development

The early players in the TES industry are moving from pilot designs and proof of concept to full commercial developments and agreements.

MAN ETES: MAN ES has developed a large-scale Electrothermal Energy Storage (ETES) system in collaboration with ABB Switzerland, operating at comparatively lower temperatures to ensure trigeneration: the simultaneous storage, use and distribution of electricity, heat and cold.

Using MAN’s existing skills with turbomachines, including compressors and heat exchangers, the system stores electrical energy both as heat up to 150 ° C and as cold in insulated tanks, in using CO2 as a medium. The system generates electricity during a discharge cycle, while the stored heat and cold can both be used in industrial applications. The system has a coefficient of performance (COP) of three and is applicable to large scale sizes, the standard configuration storing 128 MWh of electrical energy.

With basic electrical regeneration and varying heat and cooling requirements depending on the desired industrial use case, the suggested cost of the MAN ETES range of configurations ranges from “10 million euros to between 30 and 40 million euros. euros, ”Decorvet said.

The company won its first major project in Esbjerg, Denmark. The MAN ETES system will replace coal-fired cogeneration for district heating. Two heat pumps will provide an overall heating capacity of 50 MW, with an emissions-free approach, using renewable energy from nearby wind farms and seawater as a heat source. The system will be the world’s largest heat pump using CO2 as a refrigerant.

Decorvet has confirmed that the system will be commissioned in the second half of 2023, with approximate costs for Esbjerg’s municipal utility, DIN Forsyning, to be somewhere around ‘high end’.

Azelio: Azelio booked its first commercial project in Dubai in March 2021, installing its first TES system, known as TES.POD, to provide 300kW storage of photovoltaic solar panels.

The system stores heat in aluminum up to 600 ° C, liquefied in a container. Azelio’s Stirling engines convert heat into electricity and can provide industrial heating between 55 ° C and 65 ° C, lasting 13 hours.

Another project in Sweden was announced in March, providing for the storage of a 446 kW rooftop photovoltaic solar installation, as well as the supply of industrial heat.

Jonas Eklind explained that the system is fully modular, with each module providing 13kW of electrical power, with the company considering projects ranging from 100kW to 100MW.

“You can connect as many modules as you want and then connect them in clusters, so you can connect eight. [for 100 kW], you can connect 800, or you can connect 2000 modules, to give you the level of power you need. We can build any size from 100 kW and up – any multiple of 13 kW, ”Eklind said.

“And if you want 1 MW, you will still have the duration of 13 hours for 1 MW. Electricity production is therefore around 13 MWh from 1 MW, and a 10 MW will give you 130 MWh, and so on.

Azelio quotes an LCOE 59% cheaper than diesel generators and 31% cheaper than BESS.

Industry growth

Other players in different markets continue to develop their own TES systems, hoping to turn pilots into large-scale programs.

Siemens Gamesa commissioned a pilot project in Hamburg, Germany in 2019 with 30 MW of nominal power, storing 130 MWh of energy for up to a week in 1,000 tonnes of Norwegian volcanic rock. The electricity is converted into hot air and blown over the rock, reaching temperatures of 750 ° C. The project generated later interest, with Siemens Gamesa citing a long-term thermal energy storage cost of 40-50 € / MWh, and further installations are planned. The system remains operational.

Berlin-based Lumenion installed its new TES steel block in 2018. A first 450 kWh prototype installed at the University of Applied Sciences (HTW) in Berlin was followed by a 2.4 MWh system for power supply and local heating, and operated by Vattenfall. The company plans to develop systems up to 500 MWh. The steel block can be heated to temperatures up to 650 ° C or higher, as needed.

In Australia, 1414 Degrees began a journey to a TES fused silicon solution, opting for a much higher phase change material operating temperature of 1414 ° C. Following pilot testing, the company announced in 2020 that its proprietary TES system (known as TESS) would require additional development work to be “commercially robust”. Its next pilot is now scheduled for 2023.

Malta, a company from Alphabet’s moonshot factory, X, has raised $ 50 million in funding, in addition to a previous $ 26 million round held in 2018. Malta aims to store energy electric in molten salts and cold liquid. It aims to put its first commercial project online in 2024-25.