Industrial scale renewable energy conversion devices such as wind turbines and solar panels are forecast to contribute significant amounts of electricity to the growing need.
As well as delivering green electricity these devices also add considerable uncertainty of supply for Grid Managers; those responsible for balancing countries electrical demand with availability. Owing to its unpredictability, wind and solar based renewable electricity is known as intermittent energy.
For the renewables industry this label is unwelcome but currently unavoidable; if the wind isn’t blowing and/or the sun isn’t shining these renewable energy harvesters are redundant. What’s more, Murphy’s Law dictates that when the wind is blowing and the sun shining their is demand for their electricity and vice versa.
The effect of this intermittency for both the grid and utilities is highlighted by the following statements:
Undersupply:
2010: The largely wind free months of April – July lead to a 30% reduction in forecast output. Similar issues have confronted utilities in the first quarter of 2011.
Oversupply:
2011: A £900,000 payout was shared by 6 wind farms in April 2011 to stop producing electricity for several hours over a two day period. Reacting to this problem, a director of the Renewable Energy Foundation said that “the variability [intermittency] of wind power poses grid management problems for which there are no cheap solutions. In future we need greater electrical energy storage facilities.” He went on to say that “a re-think is needed about the scale and pace of wind power development before the cost of managing it [pay-outs] becomes intolerable and the scale of waste scandalous”
Such intermittency/unreliability/variability is adding to the fears among grid managers that, without a storage solution and regardless of the size of the so called ‘wind fleet’, the United Kingdom will never be able to reduce its conventional generation fleet below peak load plus a margin of approximately 10%. Were that to be the case it would be a blow to the renewables industry and to government targets.
A means must therefore be developed by the renewables industries to store the low to zero value electricity being produced when it is not needed, so that it can be sold on at a time when it is in demand.
Scientists have long since pointed to hydrogen as a potential energy storage solution. It can be made relatively cheaply and at scale by electrolysis, a proven technology. The hydrogen produced could then be shipped to power stations to be burned or converted back to electricity through a fuel cell at a time when it is useful and demands a higher price.
This process is often referred to in clean energy circles as a ‘carbon free chain’. It particularly applies if the resulting hydrogen is passed through a fuel cell to generate electricity which is then fed to satisfy a local demand. This process is currently being tested for Scottish island communities.
So why isn’t everybody making hydrogen in this way?
Storing hydrogen in commercially (and environmentally) viable quantities (6%/wt) is currently a lot harder than it sounds.
The current solution, which has been ‘optimised’ for fuel cell vehicles, is to pressurise the hydrogen to 350 - 700 times atmospheric pressure. That requires huge amounts of energy, creates a not insignificant bomb and results in relatively small amounts of hydrogen being stored. This renders the process energy inefficient, impractical and potentially lethal.
Hydrogen also has a habit of escaping, relatively harmlessly, through seals - resulting in the not uncommon scene of a scientist returning to his ‘full’ bottle of carefully stored hydrogen to discover that it is now half empty. Incredible to think that car companies believe we will adopt this ultra high pressure means of fuelling their, soon to be released, hydrogen powered cars.
So, industry and government must identify, fund and develop a commercially viable material that will store and release hydrogen.
There are already plenty of well funded teams around the world looking to find this holy grail of materials. However, even those few materials identified that are capable of storing commercially viable quantities of hydrogen still require ultra high pressures and/or ultra low temperatures to store it and then tend to release it too slowly.
Until about 12 months ago we were somewhat despairing at the lack of viable breakthroughs in this area and then we received a telephone call from a UK government scientist, which changes everything!
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