Oh boy, was last week a blustery time for the future of British energy! Wind is a free resource and the sheer abundance of it across the UK during the past seven days highlights how important renewables can be for future energy strategies.
Over 9% of the UK’s electricity was generated by wind turbines on the 19th , 20th and 22nd of November. However, the total amount would have been higher because this value does not take into account turbines connected to local grids. On the morning of 22nd November, energy generated from wind-farms was more than gas. Indeed, wind power on that morning contributed over 4GW to the national grid, which is equivalent to four nuclear power stations.
This percentage of the UK’s daily electricity demand equates to around 90 GWh. That is as much as you get from burning 30,000 tonnes of coal, which would produce 90,000 tonnes of carbon dioxide because coal is pretty much pure carbon. When burning it, carbon atoms are combined with two oxygen to make a CO2 molecule. One carbon dioxide molecule has the atomic mass of 3.7 carbon molecules. Therefore by burning 1kg of coal you produce more than 3kg of CO2.
Wind is already making a valuable contribution to our energy supply. The growth rate is impressive. There is now over 6 Gigawatts of capacity compared with 2 Gigawatts in 2007. However, to create the type of low carbon energy system described in CAT’s Zero Carbon Britain 2030 report, we will need to see continued rapid deployment of onshore and offshore wind. And further changes to our energy system will be required, such as storage so that wind power can continue to supply ever greater quantities of clean energy.
Sceptics often claim that wind farms are not nearly as carbon efficient because wind needs to be backed up by burning fossil fuels. They argue that when the wind is blowing, gas turbines will have to be switched to a lower efficiency that negates any carbon savings. Combined cycle gas turbines (CCGT) are one of the most efficient gas-fired turbines in use. In a recent study, Loughborough University researched how different operation profiles influence the energy efficiency of a modern 800MW CCGT. The results show that when the turbine output modulates between 400MW and 800MW then the carbon footprint of the gas turbine per unit of electricity produced is only increased slightly compared to optimal constant operation at full 800MW capacity. This illustrates that when the wind blows harder and wind turbines produce more electricity we can reduce the amount of gas we use in turbines without having to pay a significant penalty in terms of turbine efficiency.
The evidence suggests that when we have more wind power we burn less gas and emit less CO2. The truth is that for every megawatt hour of wind generated energy, gas-powered electricity is reduced by the same amount. But how would the variable nature of wind fare during times of high demand if it became a primary resource? Well, current work by the ZCB team suggests that even with offshore wind farms spread all around the UK there will be times when almost no power is produced, and sometimes this will happen at times of high energy demand. On the other hand, it is worth noting that the UK is Europe’s windiest country so a lot of the time energy production from wind will exceed demand.
The ZCB team are busy researching methods of storing this excess energy chemically in the form of hydrogen or methane. Electrolysis can be used to split water into hydrogen and oxygen, using renewable electricity. The benefit of this is simple. It produces an energy store that can be re-used when demand requires it. Unfortunately, hydrogen is more difficult to store and handle than the natural gas (mostly methane) our gas grid uses today. The good news is that there are chemical processes to produce ‘synthetic’ methane gas from hydrogen and CO2. Methane produced in this way could be a great substitute for natural gas, which is a fossil fuel, and could be used as fuel for backup gas power stations to keep the lights on when the wind doesn’t blow. The Department of Energy and Climate Change(DECC) certainly seem to think this solution has potential as they have just awarded ITM Power a research grant to investigate this exact process. ZCB are very excited by the possibilities of synthetic methane. You can read more here.
And to end on a bit of extra good news – A major wind turbine manufacturer is now planning to open a factory in Scotland. The country is the windiest in the UK and politicians there have previously spoken out in defence of wind-farms. This deal is expected to create 750 jobs so let us hope this bolsters more interest in British wind power and aids further job creation within the renewable energy sector.