S.R. Allen

Energy analysis and environmental life cycle assessment of a micro-wind turbine

The life cycle energy use and environmental impact of an installed micro-wind turbine for domestic (residential) electricity generation has been determined. The turbine examined was a horizontal-axis wind turbine, which has a rotor diameter of 1.7 m, a power rating of 600 W at 12 m/s, and an assumed lifetime of 15 years. The system boundaries for the study encompass energy and material resources in the ground and extend to the point of delivery of electricity. The energy output of the turbine in different terrains has been estimated via a dataset of hourly measured wind speeds, and the environmental impact of producing and maintaining the micro-wind turbine was determined. The environmental performance of the turbine was assessed by assuming that each unit of electricity generated displaces (avoids the use of) a unit of grid electricity. The whole life cycle performance of a micro-wind turbine was found to be dependant on a number of factors, primarily the geographical positioning of the turbine, the available wind resource, and the use of recycled materials within the production of the microturbine.

The thermodynamic implications of electricity end-use for heat and power

Thermodynamic (energy and exergy) analysis can give rise to differing insights into the relative merits of the various end-uses of electricity for heat and power. The thermodynamic property known as ‘exergy’ reflects the ability to undertake ‘useful work’, but does not represent well heating processes within an energy sector. The end-use of electricity in the home, in the service sector, in industry, and the UK economy more generally has therefore been examined in order to estimate how much is used for heat and power, respectively. The share of electricity employed for heat and power applications has been studied, and alternative scenarios for the future development of the UK energy system were then used to evaluate the variation in heat/power share out to 2050. It was found that the proportion of electricity used to meet these end-use heat demands in the three sectors examined were likely to be quite high (∼50–60%), and that these shares are insensitive to the precise nature of the forward projections (forecasts, transition pathways or scenarios). The results represent a first indicative analysis of possible long-term trends in this heat/power share across the UK economy. Whilst the study is the first to consider this topic within such a timeframe, some of the necessary simplifying assumptions mean there are substantial uncertainties associated with the results. Where end-use heat demands are met by electricity, energy and exergy analysis should be performed in parallel in order to reflect the interrelated constraints imposed by the First and Second Laws of Thermodynamics. An understanding of the actual end-uses for electricity will also enable policy makers to take account of the implications of a greater end-use of electricity in the future.