Wind energy conversion - an introduction

Abstract

The global wind-energy resource is very large and widely distributed; and, within Europe, wind energy has the potential to provide an energy output equal to about three times the present electricity consumption. Although the wind is not very reliable as a source of power from day to day, it is a reliable source of energy year by year, and the main role for future wind-energy systems will be operating in parallel with electricity grid systems or, in remote locations, in parallel with diesel engines, so saving fuel. Systems integration studies indicate that existing utility grid systems could accept a contribution of about 20% from wind turbines, although, with changes to the future plant mix, the potential contribution is substantially greater: and similar percentage fuel savings are possible in remote locations with wind/diesel systems. Recent progress in the development of wind turbines is reviewed and the cost data now becoming available indicates that medium-sized machines, i.e. ~ 20-40 m diameter and with power ratings in the range 50-500 kW, offer the most attractive economics for land-based applications in the near future, giving energy costs in the range 2.8-5.6 p/kWh, for a typical site where the annual average wind speed is 5.5 m/s (measured at the normal 10 m height); in windier locations energy costs will be lower. Corresponding capital costs for installed wind turbines are in the range £750-1500/kW (with average outputs equal to about 30% of the rated). The UK, in common with some other countries, has a large offshore wind-energy potential, but, to be economically competitive, offshore systems will need to use multimegawatt wind turbines with diameters of 100 m and larger. Prototype machines in this size range already exist, but considerable further development is needed before the construction of large offshore wind turbine arrays can commence, although this is a realistic prospect for the 1990s. The economics of wind-energy conversion systems are already encouraging, and commercial applications already in evidence, most notably in the USA and Denmark where more than 2000 wind turbines with a total installed capacity in excess of 150 MW have been installed in the past two years. However, further operational experience is required to demonstrate that reliable operation can be sustained over periods of many years. As this experience is accumulated, and as the cost benefits associated with quantity production are achieved, the market for wind turbines can be expected to expand rapidly.