High efficiency power generation with low emissions

Imagine a scenario in which massive electricity pylons no longer dominate the countryside. Instead, a large number of small, highly efficient, low emissions power plants serve local communities. A far fetched dream? Not according to Professor John Young, who sees the possibility of 'distributed power generation' as a very likely way forward over the coming decades. He explains:

"The world's first power station generating electricity for public use was built in 1882 in Holborn Viaduct in London. Steam raised in a boiler (coal-fired with manual stoking, of course) was used to drive a reciprocating steam engine and the station efficiency was probably about 6%. Then came the more efficient steam turbine invented by Sir Charles Parsons (a Cambridge educated engineer) and this dominated the 20th century. Both coal and oil were used as fuel and by 1975 the efficiency of the best power stations was around 40%. In the 1980's, the discovery of large natural gas reserves, the development of heavy-duty industrial gas turbines and the de-regulation of the electricity supply industries all contributed to the development of the gas and steam turbine 'combined-cycle' resulting in a current best station efficiency of just under 60%. This huge efficiency improvement of almost 20 percentage points has occurred over the last 15 years and is an astonishing engineering achievement not fully appreciated by the public."

"Combined-cycle power generation has proved extremely successful but it does require both gas and steam turbines. Capital cost would be reduced if the gas and steam cycles were integrated so that only one turbine was required. In the Hopkinson Laboratory of the Engineering Department, we are working on advanced thermodynamic cycles which have the potential to achieve this objective. These so-called 'wet' gas turbine cycles include the STIG cycle (steam injected gas turbine), the HAT cycle (humid air turbine) and, best of all, the TOPHAT cycle. Wet cycles are well-suited to the smaller 'aero-derivative' gas turbines built by companies like Rolls-Royce. A wet aero-derivative with an efficiency of 55-60% would provide strong competition for a conventional combined-cycle and, being of smaller scale, would find favour in a market seeking to exploit the advantages of distributed power generation. There are, however, many technical problems to overcome and, apart from our work on different cycle configurations, we are developing computational methods for analysing different methods of turbine blade cooling, the effect on compressor performance of droplet evaporation, and the operation of air-water saturators."

[Research carried out by Professor John Young and Dr. Alex White]

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