Of all non-carbon based forms of renewable energy, wind energy is the most globally available. Not every country has a coastline to provide access to wave and tidal power. Not every country has the geography for hydropower. And not every country gets regular sunshine. But every country has wind.
Not surprisingly, wind energy is being increasingly incorporated in the energy mix of countries worldwide. But as the proportion of electricity production produced from wind increases, so does the problem of maintaining supply stability. Because wind is by nature a fluctuating resource: sometimes there is more than enough, sometimes there is none at all.
Of course, fossil fuels can be used to compensate when the wind drops. But this is neither a sustainable solution nor a particularly logical one. More logical and surely smarter from the environmental perspective, would be to store the electricity generated by the wind when it blows a lot, for later use when the wind drops.
A technical difficulty arises however. Electricity is energy in motion, and motion cannot be stored. Instead, the moving electric current has to be converted into a stationary form of energy, such as potential energy in a raised weight, or as chemical energy in a battery or molecule, or as heat in a reservoir – energy that can be stored when there is too much wind, and converted back into electricity when there is too little wind.
One of the methods for storing wind energy, namely as heat, is the subject of a research project being organised by the Danish Energy Authority and Energinet.dk, the state-owned company which operates the national grid. They are looking for 300 Danish homeowners who are replacing their old oil-fired central heating with modern heat pumps, to join a study that will look at the practicalities of using heat pumps to store electricity from excess wind energy as heat in hot water reservoirs beneath the houses, and how such a system could be networked together as a large-scale energy storage facility.
The Danish Energy Association writes in its daily newsletter that already there are 200 homeowners who have signed up to join the study, so the target of 300 looks like it will be easily reached. Of course, such a small number of heat pumps will not be able to store that much excess wind energy as heat. But if the network were scaled up to include all 80,000 heat pumps currently in operation in Denmark, it could store enough surplus wind energy to equal the output of a sizeable power station when re-released as electricity.