Marrying fuel cells with combined cycles

Mitsubishi Heavy Industries, Ltd. (MHI) announced recently that it would develop basic technologies for a triple combined cycle power generation system, which integrates solid oxide fuel cells (SOFCs) with a gas turbine combined cycle (GTCC) power generation system.

(Diagramatic representation of a completed 90-MW triple combined cycle power generation system that uses SOFCs)

In partnership with Hitachi, Ltd., MHI aims to develop a 90-MW-scale plant with generation efficiency of 60 percent or more by the end of fiscal 2014. The company expects to introduce the plant to the market in fiscal 2017, and also develop a 400-MW-scale plant in the future.

The budget envisaged for the project is in the order of 3 billion yen. The triple combined cycle system is said to be equipped with SOFCs, which will be installed upstream of a gas turbine. It is expected to generate power by sending liquefied natural gas (LNG) through the SOFCs and the gas turbine unit. The system will apparently extract air from exhaust heat recovered from the gas turbine and circulate it in the SOFCs for reuse for power generation. Residual exhaust heat is planned to be used to drive a steam turbine. MHI estimates that a 400-MW plant can possibly achieve 70 percent or higher generation efficiency.

The company intends to establish technologies to improve the output and durability of cells built inside the SOFCs as well as their mass production technology. It also plans to develop control technology to re-circulate part of exhaust heat from the gas turbine to improve the generation efficiency of the SOFCs. Meanwhile, Hitachi will undertake feasibility studies with an eye to future development and introduction of gas turbines and combustors dedicated to 90-MW-class triple combined cycle power generation systems.