From 2GreenEnergy Intern Fabio Porcu: A Big Dam for Big Storage
Storage systems play an increasingly important role for renewable energy development in our modern society. Their primary function is to store energy produced from variable energy sources, i.e., those which, by their nature, are discontinuous since they are linked to the presence of wind (in the case of wind energy) or sunlight (photovoltaics). Thanks to storage systems it is possible to stockpile electricity, to be delivered onto the grid at a time that it is needed to harmonize supply and demand.
Even large traditional power plants (e.g., nuclear power and fossil fuel) need energy storage because they cannot be switched off. In the hours of low demand, generally night and on holidays, this off-peak energy would be dissipated. Instead, hydroelectric reservoirs are used in which, when there is surplus production, water is pumped from a reservoir downstream to one that is upstream, to be released and converted back into electricity when needed.
Undoubtedly, one of the most impressive projects that is being developed for the storage of energy is the Strathdearn dam in Scotland. This huge project, about 300 meters high and 2 km long, will about 4.4 billion cubic meters of water. The energy that could be delivered is 6,800 GWh, enough capacity to balance and back up the wind and solar generators in all of Europe, where there is now 128.8 GW of installed wind energy capacity. With this capacity, the dam could provide supply for more than two days the energy production of wind farms in case of lulls.
The idea is to use a large pumping system to bring, through channels, the sea water directly into the basin of Strathdearn. The project involves the use of a station in Inverness, pumping sea water to the dam and another at the foot of the dam. The flow rate through pipes and canals is around 51,000 cubic meters per second (equivalent to the discharge of the Congo River).
The development of a project of this magnitude will certainly help raise the energy production from renewable sources, as it enables the elimination of the uncertainty of wind and sunlight. Therefore it will be possible to decrease the production from non-renewable sources.
The transmission analysis shows that at distances of less than 1000 km the losses are acceptable; with 800 kV at this distance being ideal and recommended for service for Scotland, England, Wales, Ireland and parts of Germany, France, Belgium, Norway and Denmark. So the capacity of the dam can be even enough to support wind farms for all of Europe but transmission is not feasible with good efficiency for the rest of Europe.
The project from the technical point of view seems to be practical and convenient, but it is necessary to analyze even the problems that this big project can cause:
Usually it is not good to provide all one’s energy from a single source, but to distribute it across several different resources. This would be the largest concentration of energy generation on the planet. It would be more convenient to use more and smaller sites.
From the environmental point of view the use of sea water could create profound changes in the ecosystem. The seawater would enter the land spreading into the valley. This will pollute the groundwater of the surrounding areas with the risk of polluting Loch Ness. This is a big issue but if it is possible to waterproof the lake it can be solved.
It’s not very realistic to build such a “mega-facility,” and it’s a stronger idea to convert to a number of storage dams currently in the area. We should also try to diversify both energy storage and its production, perhaps with biogas production or with the development of electric or hybrid cars that need the use of chemical batteries in the “vehicle to grid” mode; on average, a car is parked more than 23 hours each day.
