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Electricity storage

Each of the different technologies used in the process of generating electricity have their own strengths and their weaknesses. Coal, biofuels, geothermal, diesel and nuclear all work by heating water to create steam to drive a turbine that spins a coil in a magnetic field to create electricity. Wind and hydro work by a flow of moving air or water rotating turbine blades much the same way. Gas works by expanding gas driving a turbine, much like a jet engine. PV solar works quite differently, turning the energy of light into electrical energy using photo-voltaic cells.

One problem is that it is really hard to stop and start the bigger steam-driven turbines. Realistically both coal and nuclear power stations need to function 24 hours a day, 7 days a week to avoid massive wear and tear on components. Hydro and gas can both be quite effectively switched on for a peak period and then switched off when not required. The problem with both PV solar and wind is that are intermittent supply: great when the weather is on your side, fairly useless otherwise. The key is to be able to generate electricity cheaply, store it somehow and supply it when the demand is highest.

Pumped hydro is an existing, proven technology for storing electrical energy that has been adopted all around the world, and is ideal for the Hunter Valley. The technology has been around since the 1890s so is well proven and established by now. Ideally, you need two large storage dams, one at a higher elevation that the other. Two disused open cut pits would do very nicely, and we will soon have plenty of those.

Water is stored in the lower level dam, and then pumped up to the higher level dam using solar or wind power to run the pumps. Once the water is in the higher dam, it can be run back to the lower dam through turbines to generate electricity on demand.

Essentially, solar / wind generated electricity is stored as water (stored potential energy) when the demand of electricity is low but generation is high, and then released as flowing water (released kinetic energy) when the demand is high with no fuel other than sunshine and the wind. Refilling the top dam could also be done using the off-peak overnight electricity that is generated by a coal fired power station, making use of the currently unwanted electricity.

Hydrogen gas is another option for storing electricity. Once again the surplus electricity is used to store energy, in this case in the form of compressed hydrogen gas. Here water is split into its two component parts of hydrogen and oxygen by electrolysis with the hydrogen gas compressed and stored. When there is a demand later, the hydrogen is used as a fuel which when burnt, just produces water as a water product: not CO2 making it ideal for motor vehicles and is already traded internationally. This technology is already in use, often making use of the cheap electricity available at night.

Battery technology is improving all the time. The famous Big Battery in South Australia is there mainly to smooth out the peaks and troughs of production and demand, and has proven itself to be very effective and cost-efficient. It is saving South Australia $50m a year. The technology is improving all the time, especially with household sized systems connected to PV solar panels to store daytime's electricity to use in the higher demand evenings. Prices are coming down all the time.

A range of other technologies for storing energy to be released later as electricity also exist wth specific applications – flywheels, thermal storage (pumped heat energy) and liquid air all have applications where surplus electrical energy can be stored for later use.