Since the introduction of electricity supply systems and distribution by a grid network the
economies of scale have been recognized. Generating plant have become progressively larger
culminating in unit outputs of 1300 MW from nuclear and even some fossil-fuelled plant. The
relatively recent availability of natural gas at economic prices has led to the development of
extremely large gas turbines in combined cycle generating at thermal efficiencies of up to 60
per cent. It is therefore surprising that a niche market has appeared for micro-turbine
generators (MTGs) with output power of 20-500 kW.
Their appearance on the generation scene has been made possible by the development of their
component parts. Tiny radial compressor and turbines are notoriously inefficient and prone to
excessive tip leakage. Modern precision manufacturing techniques and design methods using
computational fluid mechanics (CFD) has substantially improved their performance. Highspeed
permanent magnet alternators and bearing systems have made possible the direct drive
arrangements, which remove the cost and complexity of gearboxes. Lastly, but most
importantly, modern, solid-state, power electronics has enabled the potentially unsteady kHz output to be converted to a highly stable voltage at grid frequency.