Keith Barnham: Here’s a fact you won’t have heard from the main parties during the UK’s election campaign: the nation doesn’t need a new generation of expensive nuclear reactors or a dash for shale gas to keep the lights on. An all-renewable electricity supply can provide energy security. Germany’s Kombikraftwerk project showed the possibilities as long ago as 2006. This was a simulation, in which the country’s electrical power demand throughout the year was fed into a computer in real time, scaled down and compared with the power supplied by a group of real wind and solar photovoltaic (PV) generators. The simulation then matched electrical power supply to demand 24/7 for the full 52 weeks of that year by turning to biogas generators and the power stored by, or recovered from, a hydro-storage system when necessary. Biogas is made by anaerobic digestion of farm or food waste to biomethane. This provides extremely low-carbon electricity that is far better than fracked gas, because it avoids greenhouse gas emissions from waste rotting on farms or in landfill. A hydro-storage system pumps water up to a reservoir and releases it to generate electricity on demand. The outcome of the experiment? PV and wind provided around 80 per cent of the power, with about 15 per cent from biogas and 5 per cent from hydro-storage. So Kombikraftwerk also dispelled the myth that renewables require a lot of storage. The project is still running, now as Kombikraftwerk 2 simulating a grid covering Germany, with similar results. Both show the feasibility of a 100 per cent renewable electricity supply for all of Germany, which has pledged to shut its nuclear plants. In the UK, many remain wedded to the idea that nuclear and natural gas are necessary to keep the lights on. To try to bust this myth, I have developed a computer programme, Get it from the Sun (GIFTS), to apply the German approach here. The source of the input data is the hour-by-hour power demand on the UK electricity grid for a year, and the wind and sunlight resources for the same hours, provided by the Centre for Alternative Technology. GIFTS directs excess electrical energy to hydro-storage, which can then produce power to feed back to the grid when wind and PV supply fall below demand. The simulation then calculates the contribution required from bioelectricity generation to plug any gaps. The result? Just like Kombikraftwerk, an all-renewable electricity supply can cope, even with an extended period of low wind and high demand. A particularly challenging example came in the week leading up to Christmas 2010, when wind dropped dramatically for three days. GIFTS copes by first using bioelectricity to meet demand, so hydro-storage remains full until wind power reaches its trough. The overall mix in 2010 was 75 per cent wind and PV, 19 per cent bioelectricity and 6 per cent storage. Clearly the backup to wind and PV power has to be flexible. Nuclear power is expensive and inflexible and would often have to compete with electricity from cheap, excess wind and PV to boost storage. GIFTS disproves the myth that the UK needs nuclear power. And if you still think solar power isn’t reliable, GIFTS shows that had there been an all-renewable power supply in 2010, around 10 per cent of Christmas dinners would still have been cooked by PV. The nation could also have relied on the wholesale electricity price being cheaper that lunchtime. As first observed in Germany, solar supply and daytime demand are highest around noon, so PV reduces peak wholesale electricity prices. Renewable expansion, including PV, has now cut the wholesale price of UK electricity. The rate of fall is consistent with lower prices seen in Germany, which has more renewable power.
New Scientist 7th June 2017 read more »