Energy and carbon audit of a rooftop wind turbine

Abstract

Microgeneration is being promoted as a means of lowering carbon dioxide (CO2) emissions by replacing electricity from the grid with production from small domestic generators. One concern over this drive is that the use of smaller plant could lead to the loss of economies of scale. Partly, this relates to cost but also in terms of energy consumed and CO2 emitted over the life cycle of the microgenerator. Here, an analysis is presented of a life-cycle audit of the energy use and CO2 emissions for the ‘SWIFT’, a 1.5 kW rooftop-mounted, grid-connected wind turbine. The analysis shows that per kilowatt-hour of electricity generated by the turbine, the energy intensity and CO2 emissions are comparable with larger wind turbines and significantly lower than fossil-fuelled generation. With energy and carbon intensities sensitive to assumed levels of production, assessments were carried out for an annual production range of 1000–4000 kWh, representing capacity factors of 8–31 per cent. For the manufacturer's estimated production of 2000 to 3000 kWh and, giving credit for component recycling, the energy payback period was found to be between 17 and 25 months, whereas the CO2 payback was between 13 and 20 months. Across the full production range, the energy and carbon payback periods were 13–50 months and 10–39 months, respectively. A key outcome of the study is to inform the manufacturer of the opportunities for improving the energy and carbon intensities of the turbine. A simple example is presented showing the impact of replacing one of the larger aluminium components with alternative materials.