GTI-Storage Rapid Response system offers a low cost solution for Combined Cycle Gas Turbines (CCGT) to provide frequency regulation without losing capacity or efficiency compared to current CCGT operation. The system can boost output power by over 10% in under 5 seconds.
Speed of Response
The Rapid Response system is designed to react quickly to fluctuations in power demand, which enables operators to deliver grid services such as frequency response. The UK Grid Code specifies the technical requirements for frequency response for all units. In order to comply with the code, current CCGTs must typically run below their peak output at around 90% capacity. This is so that they can increase their output to meet a sudden increase in demand.
With Rapid Response CCGTs can run at full capacity and rely on energy storage to increase or decrease output at will. Output can be increased to 110% within 5 seconds.
Rapid Response provides 2x the rate of response from 100% load
Pipes instead of Caverns
Underground salt caverns are often proposed as containers for compressed air in energy storage systems. The main disadvantage with salt cavern storage is that it requires very specific geology and hence projects are geographically constrained. Furthermore, salt caverns take many years to develop and often face environmental concerns. Isentropic Ltd makes use of pipework and cylinders which are commercially available to produce a Compressed Air Energy Storage (CAES) system which can be installed almost anywhere.
Rapid Response System Diagram
During the charging process, gas is bled from the exit of the compressor in a conventional gas turbine. The compressed air is then passed through an Isentropic
Thermal Store transferring its heat to the crushed rock. After passing through the thermal store, the compressed air is pumped to pressure using a conventional reciprocating compressor into steel cylinders at up to 250 bar. On discharge, the gas returns from the pipe store, via a throttle valve, picking up heat through the thermal store before being injected back into the gas turbine.
- The system has a low capital cost compared to other storage systems due to utilisation of the existing gas turbine machinery to produce the majority of the system work. Parsons Brinkerhoff estimate the capital cost of the Rapid Response system to start at $400/kW for a First of a Kind (FOAK) system and drop to $200-$300/kW for a Nth of a Kind (NOAK) system.
- The system can boost CCGT output by over 10% within 5 seconds, while the CCGT is generating at full load. The faster reaction time is advantageous for frequency response. The ability to provide this service while generating at full load is a benefit to the power plant owner (improved capacity and efficiency/heat rate).
- All system components except the Isentropic Thermal Store are commercially available or based on existing technology. This reduces technical risk.
- 20 year life. As the system utilises turbo-machinery and mechanical components, the design life for the system is expected to be at least 20 years, with proper maintenance and operation.
- Potentially short turbine downtime during installation. The storage system can be installed before connection is made to the gas turbine. This reduces the GT down time.