A battery that has been discharged down to 25 percent of its capacity may hold, say, 3.6 gigajoules of electrical energy. 'Recharging' the battery, adding more energy, could increase the energy stored to, say, 14.4 gigajoules of electrical energy. This is the same as 4 megawatt-hours of electricity.
Another option for energy storage doesn't need a battery.
Think of brown coal as a 'battery' that has been almost completely discharged.
The amount of brown coal that can deliver 3.6 gigajoules of electrical energy - if it is burned in a coal-fired power station - contains about 380 kilograms of carbon.
Instead of burning the brown coal, energy can be added, in a similar way a battery can be 'recharged', so that it can deliver 15.5 gigajoules of electrical energy when needed - if it is burned in a combined-cycle gas turbine power station.
There's no need to understand the chemical reactions in a battery when it is being charged and discharged. There are many types of batteries and the chemicals and chemical reactions in each type are quite different.
When renewable energy is stored by adding it to brown coal, chemical reactions also take place, and achieves the same result as recharging a battery - but without the need for the battery.
|Simplified process flow diagram of the supercritical gasification system developed by Gensos.|