| Energy storage
infrastructure, thus eliminating carbon dioxide emissions while utilising an otherwise stranded asset.
During the charging process, electricity from renewable sources powers the electric heaters, which heat up the MGA storage blocks to a temperature near 700°C.
During the discharge process, heat stored in the MGA blocks is transferred to feedwater via the embedded steam generators, which then supply steam with properties matching the requirements of existing steam turbines to generate electricity.
The system is designed to make maximum use of existing plant infrastructure to minimise costs, including high voltage switchyard, existing steam turbine and associated balance of plant equipment (condensers, cooling towers, generators, transformers, etc).
With E2S Power’s “Travelling Wave” technology (see Figure 5) one set of blocks is heated to about 700°C, while a second set of blocks is heated to a temperature near the host plant steam turbine requirements. During discharge, the steam transfers heat from one set of blocks to the other set, maintaining a constant temperature at the exit.
Compact, simple and efficient E2S Power offers a cost-effective and easy-to- integrate solution for transforming fossil fuel power stations into thermal storage systems. Some of the key advantages include compact and simple system design – with minimum disruption to existing plant.
The components employed and the design ensure a long life, estimated at 30 years, with negligible performance degradation, while the MGA thermal storage materials are abundant and recyclable.
In addition, by reusing the existing synchronous generators of the host plant, the technology is better able to provide voltage and frequency support than batteries. The TWEST system can generate steam in minutes and can potentially provide heat to keep the steam turbine on hot standby for faster startup.
The storage efficiency (conversion of electrical energy into heat) is higher than 99% as there is
good heat transfer via radiation and therefore almost no losses in this process. The roundtrip efficiency, which depends on the existing steam cycle efficiency, is typically around 40%.
Tapping into a large market After successfully validating the thermal energy storage concept in their demonstration facility
in Belgrade, E2S Power is currently developing three utility scale pilot projects with major utilities in Europe and North America. At the same time, E2S Power is pursuing full commercial projects with power companies worldwide.
Just recently the company signed a memorandum of understanding with SNC- Lavalin to explore opportunities with North American power companies.
This collaboration aims to tap into the huge market represented by over 200 GW of coal fired capacity in North America that may be decommissioned in the coming years by combining E2S Power’s technology with SNC-Lavalin’s EPC and plant integration expertise.
Left: Figure 5. The Travelling Wave principle. One set of blocks (TWESB1) is heated to about 700°C, while a second set of blocks (TWESB2) is heated to a temperature near steam turbine requirements. During discharge, steam transfers heat from one set of blocks to the other, maintaining a constant temperature at the exit
www.modernpowersystems.com | November/December 2021 | 33
Figure 3. How modules are stacked together, 18 x 50 MWh example
Enclosure ventilation
Steam line
Single module
Supporting structure
Water supply
Foundation
The 50 MWh energy storage modules are stacked in layers with a structural steel supporting structure.
Figure 4. TWEST™ is designed to be readily integrated into an existing coal plant, essentially replacing the boiler
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