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February 2009 |
Issue #48 |
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How Do You Store Electricity? Why do the batteries always run out?! When I was a child, my parents decided that caravanning holidays were the thing of the future! We bought a caravan and, come the school holidays, all piled in and were free to stop off at any destination which took our fancy. The one issue which always proved to be our Achilles heel, however, was the need for an electric hook-up to re-charge the caravan leisure battery before it ran flat and left us without lighting, without a fully operational fridge and without running water (since we were dependant on an electrical water pump). Despite the best of intentions to find a hook-up point, numerous evening meals on holidays were spent huddled around a torchlight! The Problem with Storing Electrical Energy Power storage technologies are still very much in a developmental stage. However, they are used on a far greater scale than purely for domestic appliances like torches, remote controls and leisure batteries. Electrical energy storage is unlike gas storage, since, unlike gas molecules, electricity is not a physical substance. Gas can be stored in a pipeline or cavity if it is not needed right away. However, electricity is defined as the flow of electrons along a wire or other conducting material. If those electrons stop flowing, then there is no electrical energy there. As such, to store electrical energy, you must first convert it to another form of energy which can be stored. The best example of this is the battery, where electrical energy is stored as chemical energy until it is needed, at which time it is converted back to electrical energy. The problem with power storage is that each time energy is converted from one form to another, energy is lost in the transfer. For this reason, storage is not always economically prudent way of maintaining a supply and demand balance on the National Grid. The benefits of electrical storage applications Energy storage has potential in the following areas:-
Limitations in technology Many current energy storage technologies are in a relatively primitive developmental state, and as such are not very energy efficient. The process of converting electrical energy to another form in which it can be stored and then back to electricity inherently uses energy, so the electrical power that is returned at the end is often significantly less than that which was put in. This renders current energy storage technologies not very economically viable for commercial use.
Good examples are the pumped storage
sc The key issue with developing new storage technologies is that of seeking technologies which return a higher proportion of the energy that initially was put in. The Market for Storage is growing More recently, research into better power storage technologies has been accelerating, driven by a mixture of operational and commercial drivers in changing electricity markets. Issues such as market liberalization, short-term energy trading, and changing market structures tend to increase the commercial benefits that may be gained from power storage, while increasing use of renewable generation and distributed power increase the operational benefits. This has recently led to further investment in power storage technologies. Current Storage Technologies Power storage in the form of hydrogen cells and compressed air storage are two of the more recent technologies which are being developed at present: There has been a lot of research into the development of Hydrogen fuel cells in recent years. With the decline of oil, hydrogen systems are one of the most prominent contenders for a renewable, more environmentally friendly power source. Scientists working on power storage have piggy-backed upon this advancement to develop the use of hydrogen cells for power storage. Electricity can be converted to hydrogen and stored as a fuel cell before being released again as electrical power. Electricity can be stored in this form almost indefinitely, however at present the efficiency is still relatively low; only about 50% of the power put in is returned. Development in this field is still rapid, however, and this efficiency is expected to increase rapidly as research continues.
Competitors to Energy Storage The major competitor to energy storage is simply new power generation, transmission and distribution. Energy storage is particularly useful in guaranteeing supply at peak-shaving times, but the economics of gas-fired turbines are strong and, at present, out-compete storage viability. Having said this, increasing demand on national grids as new developments and businesses come online, means that if we rely largely on new generation to meet peak demand, then costly transmission upgrades are a necessity. If instead we look to localized power storage, the distribution networks do not need nearly as much maintenance or upgrading. Nevertheless, it has also been argued that the most economically viable method of storing energy is by doing so in fossil fuels! In other words, why generate power until you need to use it. This way, you don’t lose any as you by converting it to another form. For this reason, the other major competitor to energy storage is localized power generation. This embraces the idea that instead of a small number of massive power stations providing the majority of a nation’s energy, power should be generated at more localized substations. This would reduce the cost of transmission upgrades. However, there would a fairly high initial outlay for many electricity supply systems if there was a drastic change the way in which power was generated; from being very centralized to more localized; and localized power storage is perhaps a more economically viable middle ground at present. Researched and written by Tom Wolstenholme |
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hemes
that are used in some systems, such as the Dinorwig and Ffestiniog
power stations in Wales. These schemes use electrical energy to
pump water up a hill, which is then stored as gravitational
potential. As the water is released to run back down the hill, it
drives a turbine which generates electricity as it does so.
However, for every 4 units of electricity that are taken from the
grid to pump the water, only 3 units are returned. This wastage,
and the environmental issues associated with large pumped storage
facilities, limits the use of the technology round the world. 
Another
storage technology, compressed air storage, takes advantage of
electricity being cheap typically at nights and weekends. Large
quantities of electricity are used to compress air into underground
storage. This is then released to drive a turbine and re-generate
electricity at peak times. This type of storage is particularly
useful to reduce the volume of gas needed for power generation at
peak demand times. However, compressed air storage typically makes
use of the same type of salt cavities that are used to storage
natural gas (and sometimes other hydrocarbons), leading to some
competition for suitable sites.