At one time our gas was derived from the destructive distillation of coal. The process was devised by William Murdoch, one of those Victorian fellows who invented lots of things in the nineteenth century though he is hardly remembered today.
Bituminous coal was heated in retorts and broken down into gases, tars and coke. The process is still carried out today but whereas in the past, coke was a by product, today the coke is the primary product for the reduction of iron ore in blast furnaces.
The gas was mostly hydrogen with lesser amounts of methane, ethylene and deadly poisonous carbon monoxide. Those of us old enough remember the evil smell, which was hydrogen sulphide (again poisonous).
After being purified the gas was primarily used for lighting in the early days. Contaminants in the gas meant that it burned in fishtail burners with a bright luminous yellow flame. Later, further purification meant that a gas mantle was needed as the luminosity disappeared. (The story of the gas mantle is itself worth following up, some of them being radioactive and others carcinogenic.)
The gasworks also produced a vast range of byproducts used in the manufacture of fertilizer, dyes, explosives, sulphur, ammonia, tar, napthalene, hydrogen cyanide and hydrogen sulphide. Less useful was arsenic and mercury together with some radioactive substances; lead and radium. The gasworks are long gone, leaving behind ground that is so contaminated as to be unusable for any purpose.
Back in 1965, natural gas was discovered in large amounts under the North Sea, mostly methane and of double the energy value. It may be found associated with oil or on it’s own. It often has to be processed to remove carbon dioxide and “condensate gases”.
To make use of this, new pipelines were constructed, and new storage facilities though some of the old coal gas “gasometers” were used. Some of our gas is stored in the national grid pipelines at high pressure. The gas production in our part of the North Sea is now declining, we now import large amounts of our gas from Norway and by cryogenic tankers from the Middle East.
Our main gas storage is in a depleted gas field to the North East of Hull which is “refilled” with gas from elsewhere. Technical problems have recently arisen with this arrangement, involving leakage; the consequences are not yet fully apparent. However the outlook is not good.
The government has recently decreed that from 2025 no new gas boilers will be fitted in new-build houses and from 2035 no new gas boilers will be fitted anywhere, ie the use of gas domestically is to be terminated after over 200 years.
It has to be said that this will end the domestic gas explosions we frequently hear about.
So what is the thinking behind this? It all comes back to efficient use of energy and the new combined cycle gas fired electricity power stations.
In the traditional coal or oil fired power station, coal/oil is used to raise steam which drives steam turbines which drive the generators. Efficiency is around 30% and that only by extremely complex and expensive design.
In a combined cycle power station, gas is used to drive a gas turbine which drives a generator. The hot exhaust gases from the turbine are then used to raise steam which drives a steam turbine which drives yet another generator. This means that two “bites” are had, raising efficiency to around 60% ie, twice as much electricity for the same energy input. There are other savings in fuel storage, handling and maintenance. CO2 emissions are around half that of equivalent coal fired plants. Pollution is very much less than coal fired plants and what there is is more easily dealt with. There is no ash disposal problem. They are more suitable to run in parallel with renewable energy sources.
So how then are our homes to be heated? The answer is by use of electricity. This would be completely unviable except that use is to be made of heat pumps. These multiply the heat energy derived from the electricity by around three. (The Coefficient Of Performance.) A “refrigeration” cycle pumps heat from outside the house to inside. To keep installation costs down, the source of the heat is usually the air, though heat stored in the ground can also be utilised. Heat pumps are being fitted even now, the air source ones have a large box with a fan located outside the building. The building needs to be well insulated, have a high thermal mass and ideally underfloor heating. Some heat pumps are reversible so the house owner can enjoy the benefits of air conditioning too. The technology is yet improving.
The problem with air source heat pumps is that they become less effective as it gets colder. The problem with ground source heat pumps is expense of installation.
The benefit of this energy policy is, as regards home heating, that overall we get six times the bang for our buck as regards energy consumption.
Energy losses transporting electricity are significantly less than for gas. The gas grid will eventually cease to exist, however our existing electricity grid will need significant upgrading, especially if we are also to embrace electric cars.
Photo by STML