This month's meeting addressed the problem of power generation when the sun does not shine and the wind does not blow. The answer was to store energy in the times of excess so that it is available to address times of energy shortfalls.
When there is a shortage of electrical energy the first thing is to ramp up the use of gas as it is easy to switch on and off, but of course the downside is that it generates carbon dioxide. The next stage is to maximise the use of biofuels and nuclear power but these take up more time to start up their supply. We can use our interconnected power cables that run across the North Sea and equally we can export power through these cables when there is an energy deficiency on the Continent.
However it is better to develop methods of storing energy that can be readily switched on and off, to balance demand. The current options are pumped hydro, compressed air, flywheels, sand batteries, free flow batteries and hydrogen, many of which are in the early stages of development.
We have had small scale pumped storage in Scotland and Wales for many years, but now is the time to increase the size and scale of these projects.
Pumped storage involves pumping water up to a high level reservoir during times of low energy demand and then letting the water flow down the hillside to power turbines at the time of high demand.
The Foyers pumper storage scheme in Scotland was designed to be used 600-700 times a year, but last year it was used 6500 times.
New larger 1.3GW projects are planned to be able to power 3 million homes for 24 hours. A new company RheEnergise has developed a similar system which used a mineral rich fluid with a density of 2.5, so that plant can be installed in small hills. They have identified 6500 potential site installations within the UK.
An alternative scheme is to use compressed air which is stored in underground caverns. The air displaces water up into a surface reservoir. When extra power is required water is released back into the cavern forcing the air out through a turbine to generate electricity. A major project of this type has been installed in California. This unit will run at full power for eight hours.
For years flywheels have been seen as a mechanical means of storing energy. Now they are being adapted for power generation. Giant flywheels are mounted vertically on axle bearing and they drive electric motors/generators. There is one project in China involving 120 of such units having a combined capacity of 30MW. Another application under consideration is for the use of smaller units to rapidly charge electric cars to give an additional 100 mile range.
A Finnish company has built a two sand battery systems, a small unit (2 MW) and a much larger unit (10 MW). The sand is heated up to 1000 degrees C and this heat can then be used to power district heating systems, steam generation, compressed air or to generate electricity according to location and need.
Flow batteries are more well known through the concepts of Tesla’s impact wall units and large scale industrial battery projects. Many companies are now coming forward with novel ideas for the battery material. Tesla and many others use lithium batteries but one British company uses vanadium flow batteries as these do not carry the same fire risk and can be used over and over again without major reduction in capacity to hold charge.
Government policy is to extend flow battery storage up to 23 GW by 2030, up from 4.5 GW currently; yet there are 221 GW batteries being proposed by commercial companies trying to get their battery systems connected to the grid.
Finally hydrogen is being touted to store energy. It can be easily stored and produced when there is excess power and then used to generate electric when power is needed. The process also produces oxygen helping to improve the environment.
The future is coming and our electricity power will be using renewable energy balanced by any one of the above systems at times of peak demand.