Power storage
Denmark is world leading in wind power. A clean energy resource, but on days with low electricity consumption a lot of clean energy goes to waste. How can this energy be stored?
Could an artificial atoll outside of Copenhagen be a way to store energy? (Illustration: Gottlieb Paludan)
Europe has committed itself to major cuts in greenhouse gas emissions and to increase the share of renewables in the energy mix. Wind farms play a large role in the restructuring of the energy grid towards renewable energy, with huge developments either planned or under way. Though wind power is an excellent source of clean energy it is still unreliable. If the wind is not blowing, there will be no electricity. But the opposite can also be the case, the wind may be blowing at times energy needs are low, creating an excess of electricity. What if this energy could be stored for later use?
Danish atolls
This is exactly what the consultants and architects at Danish firm Gottlieb Paludan together with Risø DTU, are suggesting by proposing the construction of huge artificial “atolls” off the coast of Denmark. The idea is that when energy demand is low, typically during nighttime, wind turbines will instead be used to power pumps emptying large basins of sea water. At daytime the basin will be refilled with seawater, and in the process the seawater will run through turbines generating electricity.
The concept is called pumped storage hydropower and the project is called Green Power Island. The technology is well known, as it has been around for over a hundred years. Pumped hydro was first used in Italy and Switzerland in the 1890s. The technology is in other words already available, and Gottlieb Paludan calls it an “instant and low tech answer to green energy overflow”.
Well known concept. Pumped hydro is all about taking advantage of the difference in elevation. Empty the basin during night, and let the water flow in during the day, when energy need is high (Illustration: Gottlieb Paludan)
Large scale
Though low tech, the scale of the project is humongous. The plant envisioned constructed outside Copenhagen will occupy an area of nearly five square kilometers. It will be an artificial atoll with a gigantic floating solar power plant in the middle. The water reservoir will hold 22 million cubic meters of water with a generation potential of 2300MWh of electricity. This is nearly the total energy consumption of all the households in Copenhagen. The artificial island also serves as a platform for recreation for Copenhagen’s inhabitants and as a site for production of biomass. This solution will require both huge investments and will occupy large areas.
Energy from buried balloons
Two other Danes are trying to show that the answers to big questions are not necessarily big solutions. The two inventors Asger Grambow and Jan Olsen are about to start the second phase of their energy storage concept. Their idea is similar to that of Gottlieb Paludan, but on a much smaller scale.
On days when electricity is cheap, water from the fjord will be pumped into large bags buried under thousands of tons of dirt. When electricity price rise again the valves open, and the pressure from the soil forces the water through turbines generating electricity.
So far they have only tested it in small scale, but they are convinced it also works in large scale, they told the newspaper Jydske Vestkysten. A full scale energy storage will be 500 x 500 meters, cost 200- 250 million dkr and have an effect of 30Mwh. The company is called GODevelopment and the project is supported by Risø DTU and Energynet.dk.
