Malta of Google X- Ingenuity in Renewable Energy Storage
The Rush for Green Energy
Quest for cheap energy storage is like the “Alchemy’ of the old, or the ‘gold rush’ of the US history. Anyone who can hit upon a scheme for storing energy will hit a gold mine. Storage of energy, not fuel, has become very important since the advent of renewable or alternate energy sources especially solar, and wind. Both sun and wind are abundant and relatively inexpensive with the added advantage of being green and clean. This has led to rush to create commercial and domestic renewable energy.
Abundant but Not When Most Needed
But sun and wind are not continuously available. Availability of solar and wind energies cannot be controlled by humans, and their peak and off-peak hours do not coincide with those suitable to humans. As a result, it is reported that state of California had to dump 300 GWh of energy generated from solar and wind projects. According to data of 2015, Germany could not utilize 4% of its wind energy, and China had to let go of 17% of its renewable output. Hence, excess solar and wind energy must be stored during peak availability to be used during peak demand hours. Among various initiatives, this led to Malta, not the Island Malta, but Project Malta.
Malta is a project of lab Alphabet, formerly Lab X, a secretive lab which created the google driverless car and google glass, among other possible initiatives. The project code-named Malta uses very basic principles of physics. It uses solar thermovoltaics with a difference. Electric power produced in excess of need is converted to thermal energy and stored away in insulated tanks. The energy is then reclaimed when need and converted from thermal to electrical energy.
So What is special About Malta?
To this extent, there is nothing new in Project Malta. But according to the limited information released, it is being done very ingeniously. A heat pump operates on electricity to produce a stream of hot air, and one of cold air. The former is used to heat a reservoir (of two tanks) of molten salt, the usual favorite for such applications due to its specific heat and high boiling point. The cold stream is made to cool a reservoir of (two tanks again) of antifreeze liquid.
All four tanks are well insulated thermally, so that there is no heat leakage. When there is demand for electricity, the reverse action is allowed at the flip of a switch. Jets of hot and cold air respectively from the two reservoirs rush towards each other possibly driving a turbine loaded with a generator to produce electricity. This electricity can be fed into the grid in no time. Company plan to store close to 790 MWh this year has declared. It is also estimated that global capacity could possibly touch 45 GWh in the next seven years.
The Two-Temperature Advantage
The ingenuity lies in storage of energy at two temperatures, above and below the ambient. This means lesser energy losses for the same quality of insulation, or more energy storage for a given level of insulation because the temperature differential with ambient is reduced by two times.
Specific details of how things are done have not been released. What type of heat pump is used? That is wide open. Indeed, there is a possibility of a better heat pump being available tomorrow. Similarly, what heat machine will be used to convert back to electricity can again change with technology developments. However, the idea of two temperature storage above and below the is indeed very good.