Power Storage: the options

Power Storage: the options

In Stephentown, New York, Beacon Power has build a 20MW / 5MWh plant consisting 200 carbon fiber FlyWheels.
These FlyWheels make between 3000 and 5000 cycles per year through their input in the frequency regulation market.

Power Storage: The world does have a lot of options but its still expensive.

In order to manage supply and demand our renewables, we need to store the electricity when the wind is blowing hard and the sun shines brighter than there is demand.

For instance, Berkeley wind energy experts suggest a likely average cost reduction of between 24% to 30% by 2030 and 35% to 41% by 2050 across the three wind applications studied — onshore wind, fixed-bottom offshore wind, and floating offshore wind.

There is a further 10% chance that cost reductions could be more than 40% by 2030 and more than 50% by 2050. BetterWorldSolutions offers you a number of actual, technically available options.

1. Pumping stations

Electricity is used to pump water into a higher reservoir. With increasing demand, this water flows back down where Francis turbine generators boost power generation. A 25 m deep tank with a diameter of 1 km can store around 10,000 MWh of electricity. This storage is the worlds most widely used technology for large-scale electricity storage.

The Bath County Storage Station in the US state of Virginia is the largest pumped storage power station in the world with a peak power (at full reservoir) of 3,000 MW and a capacity of 24,000 MWh.

2. Chemical storage / batteries

At the moment, there are already a lot of different batteries capable to store energy from renewables. Often high efficient but expensive when used for large-scale storage.

There are a few large-scale battery systems.

  1. According to the magazine Clean Technica, you can find the largest battery storage in the Chinese city Zhangbei. It is a building containing thousands of LFP batteries (lithium iron phosphate), which together have a capacity of 140 MW and a storage capacity of 36 MWh.
  2. Japan Wind Development used sodium sulfur batteries which are storing the wind energy with a capacity of 34 MW.
  3. In February 2016, the American AES opened in the Netherlands an installation consisting of 45,000 lithium ion batteries that can store 10 MW. With the completion of the Netherlands Array and the 10 MW Kilroot Array in Northern Ireland, the AES Advancion solution now powers the largest fleet of advanced energy storage in Europe.

In mobile applications, such as in cars and laptops, the energy is very important. The more per watt-hours per kilogram, the better. In large-scale, static storage is less important and are heavier, cheaper batteries a better option.

3. Compressed Air

Compressed air systems compress air at high pressure and stores it (mostly underground). There are few projects and they are huge.

An electric motor is compressing the electricity in a tightly enclosed space, such as a cave or a mine shaft. When the air is released (sometimes heated)  the air is able to generate electricity in a gas turbine with a generator.

When the heat generated by compression is being reused for heating, the yield increases from 40% to 80%. Such a system is possible, by storing the heat in a saline solution. When a sealed space is used and the heat is recycled, a compressed air system will have a theoretical yield of 100%; In practice it is usual 70%.

  1. Since 1978 the air of a nuclear power plant with 72 bar in stored in a salt mine in Germany Huntorf. This installation can provide 321 MW of peak power in four hours. The yield there is due to the lack of heat storage, only 40%.
  2. The second compressed air storage was built in 1991 in McIntosh, Alabama with technology from Dresser-Rand (Power South Energy Cooperative, 2015).

4. Flywheels

Energy storage by Flywheels is a storage to watch right now. A flywheel converts electrical energy to kinetic energy. An electric motor/generator starts a heavy rotating disk that converts a lot of energy because of its high mechanical inertia.


In order to prevent frictions, systems are built with magnetic bearings and the flywheels are placed in a vacuum.

  1. In 2011, Beacon Power, opened a plant with two hundred flywheels generating up to 16,000 revolutions per minute each. Together they have a capacity of 20 MW.

Such a system can respond faster comparing with batteries and are primarily intended to prevent large fluctuations in the power grid. DNV GL finished a large-scale study in Europe combining flywheels and batteries. The batteries provided the capacity and flywheels the peak power.

5. Power to Gas (P2G)

Power to Gas is promising. Especially in Europe with its natural gas grid.

E.ON Germany has built two power plants of 2 MW and 1.5 MW. The plants convert the excess electricity of wind turbines into hydrogen using the electrolysis of water. The gas is injected into the natural gas grid.
The yield is 75% and can be increased up to 85% using the recycling of heat.

It is also possible to use the hydrogen into a fuel cell or to convert again to electricity.
The European Power-To-Gas consortium expects a large-scale conversion of CO2 and hydrogen into methane in the future. This process means an extra waste of 5 to 10%, but the produced methane can replace the conventional natural gas.

6. Other storing options

The boost of wind and solar power is a great incentive for storage systems researches.

  1. The German Aerospace laboratory DLR is working on a system which is used for heating of liquid salt from 280 to 560°C.
  2. The US state Nevada plans to run a train up to the hill; when the train is driving down the hill, the stream should be delivered again.
  3. With cryogenic energy storage, air must be cooled down -196°C: the temperature when the air converts into a liquid. Evaporating again it can drive an expansion turbine. In the UK, a CES (cryogenic energy storage) plant shores energy with a peak power of 300 kW and a capacity of 2.5 MWh


Have you seen this?

Renewable Energy Storage Systems (dossier)

Pros & Cons of (renewable) energy sources (dossier)

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