Thermal energy storage TWEST enables CO2-free electricity production at thermal power plants

E2S Power, a joint venture between Swiss SS&A Power Group and German company WIKA, has presented its innovative thermal energy storage technology, TWEST, which provides a solution for intermittent production from renewable energy sources and enables thermal power plants to switch to CO2-free operation. The presentation was held at E2S Power’s demonstration facility in Serbia’s capital Belgrade.

The E2S Power thermal energy storage technology has been validated in the E2S demonstration facility in Surčin, near Belgrade, and it enables the conversion of coal power plants into green energy storage facilities and producers of CO2-free electricity.

E2S Power  is currently developing three pilot projects: one in the troubled Montenegrin power plant Pljevlja (target is 2022), a 50 MWh storage plant with EP Power Europe (target is 2022), and an additional pilot project with a US utility. E2S Power is also in talks on several commercial-scale projects in Europe, the US, and Canada.

The implementation of the solution for existing coal power plants would involve the installation of the Traveling Wave Energy Storage Technology (TWEST) system that includes, in a single module, the following: electric radiating heaters, MGA storage blocks, and steam generators. The system stores energy from wind farms or solar power plants in the form of heat. The heat, when necessary, is converted into steam to run existing steam turbine generators to produce electricity.

“Our solution combines heaters, storage, and steam production in one compact unit. Electricity is converted to heat and back to electricity without using air or other media,” said Fabrizio de Candia, E2S Chief Operating Officer.

He added that it is very important the solution can transition coal power plants to clean energy utilizing existing infrastructure and employees.

The solution is based on traveling temperature wave principle, and Miscibility Gap Alloys (MGA)

The thermal energy storage TWEST is based on traveling temperature wave principle to maintain a constant steam temperature, and Miscibility Gap Alloys (MGA) a storage medium with superior energy density compared with other thermal energy storage materials.

The traveling wave principle utilizes two sets of storage blocks. During the charging process, the first set of storage blocks is heated to a very high temperature, of 700 degrees Celsius, while the second set is heated to the temperature required by the steam turbine, said Saša Savić, E2S Power CEO.

The system is based on the traveling wave principle utilizing two sets of storage blocks

In the discharging process, steam is initially generated in the first set of blocks at the temperature close to 700 degrees Celsius and then is cooled down by the second set of blocks to the turbine inlet temperature. During the process the heat is moved in the form of traveling waves from the hotter to the moderate thermal storage blocks.

Energy storage materials are based on Miscibility Gap Alloys (MGA), which have been developed by Australian partner MGA Thermal. These blocks consist of graphite and aluminum, said Savić, adding that the materials used have a long life, and are abundant, safe, and recyclable.