Vattenfall investigates SaltX storage process

4 July 2019

Vattenfall, together with the Swedish company SaltX Technology, has commissioned an industrial scale, 0.5 MW/10 MWh, pilot test facility at its Reuter power plant employing SaltX’s patented thermal energy storage technology.

The technology developed by SaltX employs “nano-coated” salts. Heat energy is stored chemically, by separating salt from water, and then released by combining them again. SaltX summarises the process as follows:

  1. When the nano-coated salt is “uncharged” it is a mixture of salt and water.
  2. The nano-coated salt is “charged” by heating it up to 500°C. The water evaporates from the water and the dry salt is now charged.
  3. As long as the nano-coated salt is dry it is charged. The salt can be stored at normal room temperatures, and the stored energy used hours, days, or months later.
  4. The nano-coated salt is “discharged” by adding steam or water to the salt, with the resulting chemical reaction producing temperatures of up to 450°C.

The technology allows thermal energy to be stored at “scales ranging from individual processes to large scale storage for municipalities and cities”, says SaltX Technology.

The idea behind the nano-coating, according to SaltX, is to “prevent the salt from becoming sticky, making the salt retain its original single crystal form.” This means that the system can be charged and discharged thousands of times without losing performance. The nano-coating also provides protection against corrosion, the company says.

SaltX says it is testing various combinations of nano-coating and salts to achieve optimal performance. “Nanocoating salts is not an easy task” and each salt requires a different approach.

The tests at Reuter are planned to run until the end of summer 2019. Test data will then be evaluated, and the results presented by the end of the year.

The SaltX pilot testing is part of a long-term rebuilding programme underway at the Reuter power plant. In the course of 2019, Vattenfall also plans to start operation of what it describes as Europe’s largest power-to-heat facility at the site, employing hot water storage. During 2020, Vattenfall will take the Reuter C coal unit out of service, which is a further step in the plan to completely phase out coal from Vattenfall’s Berlin district heating operations by 2030.

Vattenfall in addition already has an operating power to heat facility in Hamburg (Karoline).

SaltX, meanwhile, has recently announced redundancies as part of a cost cutting exercise, saying it is taking longer than hoped to achieve positive cash flow. It is planning to focus efforts on large-scale storage, “especially in light of the successful opening and start-up of the [Vattenfall] pilot plant.” 

Energy storage to go from Aggreko 

Aggreko, provider of temporary power, temperature control and energy services, is adding mobile and modular energy storage to its 10 GW fleet of distributed energy assets. The Y.Cube is a fully integrated, ready-to-install lithium-ion battery system, building on the expertise of energy storage pioneer Younicos, which Aggreko acquired in 2017. Housed entirely within a standard 20 ft container, the 1 MW units can be delivered and quickly deployed worldwide.

The system can cover a variety of applications from 1 MW up to multi-MW power output and is available in two versions: a 30-minute “power” unit; and a 60-minute “energy” unit. The 20 ft container houses batteries, inverters, HVAC, fire protection and auxiliary components, controlled by “intelligent software.” It is designed for a wide ambient temperature range, from -20°C to +50°C to match the often-challenging requirements of remote sites.

“It is designed to fit seamlessly within the Aggreko existing fleet and can be easily combined with solar and thermal products to provide our customers with the lowest cost of energy”, said Dan Ibbetson, managing director, Global Products and Technology at Aggreko. “We are now building a fleet of Y.Cubes, which will enable us to quickly deploy at short notice.” The Y.Cube is available for short-term needs for as little as six months or for periods of years under Aggreko’s “Energy-Storage-as-a-Service” model. It can also be bundled with Aggreko’s other hardware systems as part of the company’s “Microgrids-as-a-Service” offer.

Karim Wazni, managing director, Aggreko Microgrid and Storage Solutions (AMSS), said: “We’re already seeing considerable interest from a range of sectors and applications. One of the most economically attractive propositions is to combine the Y.Cube with natural gas and solar generation in off-grid applications. This could include remote mining sites, in weak grids like islands, or, with gas generators only to provide bridging power – for example in datacentres.”

Aggreko will be deploying the Y.Cube as part of its hybrid microgrid solution at the Granny Smith gold mine in Western Australia, as well as in several African mining projects. AMSS is also working with island communities and datacentres to introduce the Y.Cube. 

SaltX pilot facility at Vattenfall’s Reuter power plant
SaltX nano-coated salt
Nano-coated salt achieves high energy density

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