22 June 2012
Californian study shows how green technologies can cut emissions by 90%
California has been used as a case study for research showing that existing technologies, such as wind and solar power, could dramatically cut greenhouse gas emissions with only moderate rises in the cost of producing electricity. The research, published in the journal Environmental Science and Technology, is the first study to quantify the cost and environmental impact of adopting renewable energy on a very large scale. It suggests that big cuts in emissions can be made without the need for new nuclear plants or carbon capture and storage. The biggest gains can be made if customers change their habits too, for instance, by doing their laundry on windy nights.
The study conducts an hour-by-hour analysis of California’s wind and solar resources and electricity demand. It shows that the state could use renewable energy to reduce greenhouse gas emissions from electricity and light vehicles by 90% below 1990 levels by 2024. The least expensive system that could be built by 2024 would produce power at an average cost of 10.5 cents per kilowatt-hour, but the proposed system with 90% emission reductions would produce power at a cost of 13.3 cents per kilowatt-hour – just 27% more, according to the study.
It reports that electricity costs could be pegged especially low if customers used electrical devices when renewable resources were in plentiful supply or electricity demand was low: for instance, running washing machines or charging electric vehicles on windy nights. It finds that if electric vehicles were adopted on a large scale and charged at the right times, larger shares of renewable energy could be used at a lower cost with greater benefits to the environment – and this would approximately halve the cost of motoring as compared with current gasoline prices.
Study author Dr Matthias Fripp, Visiting Associate Researcher at the University of Oxford’s Environmental Change Institute and Assistant Professor of Electrical Engineering at the University of Hawaii, argues that the cuts can be achieved by using renewables with back-up from established conventional technologies, such as natural gas.
He says the study presents a realistic alternative to the oft-quoted view that nuclear plants, carbon capture or large-scale storage of renewable energy are the only means by which to avoid man-made large-scale climate change.
Millions of different combinations of wind, solar and conventional power plants could be built in any large power system, which makes estimating the cost of achieving any particular emission target seem almost impossible. However, Dr Fripp has designed computer software that solves this thorny problem. His software, ‘Switch’, can identify a specific portfolio of projects which reduces emissions at the lowest cost while continuing to provide a reliable power supply for all customers.
His model reveals that the least expensive way to achieve deep emission reductions would be to build large numbers of wind and solar facilities, while also building nearly enough conventional power plants to meet peak electricity demands. Wind and solar power would then be used most of the year to save on fuel and emissions, with natural gas power being used to fill in during periods of low wind or no sun.
This approach is shown to be surprisingly cost-effective in the California case study partly because wind power is projected to cost less than natural gas power, and partly because the cost of building natural gas capacity is quite low compared to the cost of actually running that capacity.
Dr Fripp explains: ‘This model enables power system planners to identify the least expensive options out of millions of different permutations. This hour-by-hour, project-by-project model is the first software with enough detail to allow long-term planning for large power systems with large shares of renewable energy sources. Many people assume that renewable power can’t be used on a large scale, but this study – the first to use hard data to address this question – shows that it can.
‘I expect research in other states and countries to reach similar conclusions, though the ideal mix of resources is likely to vary from region to region, depending on the amount of solar, wind, geothermal or other resources available.’