Battery Killers: Grid-Interactive Water Heaters

grid interactive water heatersGrid-interactive water heaters (GIWHs) add bidirectional control to electric resistance water heaters, allowing a utility or third-party aggregator to rapidly toggle them off and on. This functionality turns a fleet of water heaters into a flexible energy-storage medium, capable of increasing and decreasing the load on the grid on a second-by-second basis.

GIWHs are currently the least expensive form of energy storage available. Utilities can use fleets of grid-enabled water heaters for load shifting, demand response, arbitrage, ancillary services, or to respond to unexpected grid-stabilization events. Traditional dissemination of new water heater technology has been a painstakingly slow process, but water heater rental programs may greatly accelerate this process.

Read more: Battery Killers: How Water Heaters Have Evolved into Grid-Scale Energy-Storage Devices, David Podorson.

Related: How sustainable is stored sunlight?

Solar Powered Grain Mill

solar milling

“Graining cereal crops is a basic, century old business and it will continue to be as important as ever before for centuries to come. Before the age of oil grain milling was entirely based on renewable energy. It was either done by wind energy, hydropower, animals or manpower. For the last century the traditional grain milling has been mainly replaced by electricity and fuel driven milling.”

“The Solar PV Grain Mill works to the same principle like any conventional, electrically driven mill. The mill has a very efficient 3-phase AC motor which is directly coupled to the graining system. The main invention of the system is, and that makes it unique among PV systems, that it is a “direct drive system” without the need of batteries. The Solar PV generator converts solar radiation into electricity, and the generated electricity is directly feeding the motor drive. There are no additional conversion losses, such as energy storage losses in batteries, battery maintenance or replacement costs, which are a common problem in conventional Solar PV off-grid systems.”

Read More: Solar Milling. Via Engineering for Change.

I would like to add that the direct drive system also eliminates the high energy use caused by the production of the batteries, which can make solar PV off-grid systems everything but sustainable. Therefore, storing work instead of energy — the solar mill only operates when the sun shines — is a very interesting strategy in sunny regions.

Related:

The Energetic Implications of Energy Storage

“When renewable energy sources such as solar and wind farms generate more electricity than consumers need, storing the excess doesn’t always make sense. Large, grid-scale batteries capable of storing the extra electricity are resource-intensive and costly to manufacture and maintain — sometimes more so than the energy they’re used to store.”

The energetic implications of curtailing versus storing solar- and wind-generated electricity, Charles J. Barnhart et al, Energy & Environmental Science, Issue 10, 2013. Open access. Via Eurekalert and Yale Environment 360.

Rail Energy Storage

“ARES is a rail-based technology that stores energy by raising the elevation of mass against the force of gravity and recovering the stored energy as the mass is returned to its original location. Specifically, ARES energy storage technology employs a fleet of electric traction drive shuttle-trains, operating on a closed low-friction automated steel rail network to transport a field of heavy masses between two storage yards at different elevations.”

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Archimedean Energy Storage

mechanical battery“Forget batteries with complex chemistries or precision-tuned flywheels. A growing number of energy storage start-ups are promoting the idea that the most economical, most expedient ways to store power revolve around harnessing the four elements of the ancient world: earth, air, water and fire.”

Read more: The most important man in energy storage? Try Archimedes.

Sand-Powered Water Wheel

“Out in the Bodie mining district, California, they have a peculiar motor in use. It is called an arastra, and consists of an overshot wheel operated by sand instead of water. A windmill runs a belt containing buckets, which carry the sand up to a big tank, just as grain elevators carry wheat in a flouring mill. A stream of sand is let out upon the overshot wheel and it revolves just as it would under the weight of a stream of water. The arastras move steadily at their work. When there is much wind, sand is stored up for use when calm weather prevails, so the arastras are never idle. It is perhaps needless to say that the sand is used because water is scarce. The arastra is an invention of a miner named Townsend.”

Quoted from: The Manufacturer and Builder, Volume 0016 Issue 2 (February 1884).