Power & Utilities can be categorized by the type of energy source used and the scale of the assets.
Conventional Thermal Power is typified by coal fired power station but also includes any electricity generation derived from a heat cycle such as steam turbines using the ranking cycle to provide the motive power to turn a generator. Increasingly gas fired combined cycle units with heat recovery from exhaust gases are being built due to the inherently lower green house gas effect from burning methane rather than coal. For conventional thermal power any review must start by establishing the true efficiency of electricity generation from the total energy input from the fuel. Many combined cycle power stations claimed to have very high thermal efficiencies but these can vary dramatically if the off-taker for heat is not stable. Any investment in conventional thermal power must concentrate on the long-term fuel price (contractual and market) as well as the agreed off-take tariff. Additional features of conventional thermal power units are site logistics, materials of construction and long-term maintenance history. In the case of coal-fired units change in the source of coal can dramatically impact on the aging of metallurgy and also the environmental permitted emissions.
Unconventional thermal power includes non-renewable nuclear, and many renewable feedstocks from woodchip to bio-gas as well as geothermal. In the case of thermal plants, which burn the feedstocks in conventional grid furnaces, the power conversion from thermal energy to electrical energy is often the same as for conventional power. Caution must be taken in understanding the variability of the calorific value of the fuel source, which can vary widely due to environmental conditions (such as moisture content in wood and age and composition of refuse in land gas). Whilst good engineering advances have been made to homogenize feedstock energy content this has a more complex impact on fuel pricing. For geothermal there are typically two schemes: low surface solar collection or deep hot well technology. In both cases the geology and heat transfer capabilities of the land utilized has a major impact on the real heat recovery achieved. Experimental schemes such as solar boilers using salt towers show some promise but none are currently commercially active.
Electricity generation non-thermal; these are exclusively renewable such as hydro wind, photovoltaic and wave and tidal power. In every case except photovoltaic the motion of a fluid (caused by a natural phenomenon) is the motive power to turn the generator. These schemes benefit from engineering simplicity and high energy conversion efficiency but tend to be very high capital investments per MWh installed. The clear advantage is free fuel but increasingly the feed-in tariffs used to attract investment are being reduced as the technology matures. Run of the river hydro schemes and similar tidal plants appear to be approaching conventional thermal power economics. Any review must center on the reliability and availability of the natural fuel source as the key underpinning assumption for future power generation capability.