I like the GridCarbon iPhone app from www.ideasproject.info. This simple app takes data from the Elexon website and presents you an updating view of where the electricity being consumed in the UK comes from and what each source’s carbon foot print is.
If you look at this snapshot you’ll see that by far the biggest source of electricity is coal. This is the normal situation in the UK. So how do we generate electricity from coal? Well we dig it out of the ground, put it in a big furnace and burn it. The resulting heat is then used to boil an enormous kettle that produces steam, the steam is run through a turbine which drives a generator before being vented to the atmosphere. All very nineteenth century, the Victorian would be proud of it.
Next down the list in this snapshot is Nuclear – surely this is a much more high-tech source of electricity? Well no, the sophisticated control systems apart basically a nuclear power station splits atoms releasing enormous amounts of energy which is used to boil water to create steam that is put through a turbine which drives a generator – you get the picture.
These “thermal technologies” only convert 30-40% of the heat input into electricity, the rest of the energy is exhausted as waste heat usually to the atmosphere. Some more progressive countries capture this heat and use it in district heating schemes for houses and businesses.
So what about “clean gas”? You ask. Well gas is used in two ways; the first is to heat water … you know the rest. The second is in a combined cycle gas turbine (CCGT). The CCGT works more like a jet engine with the gas being burned in the turbine and the resulting hot gases used to drive the turbine to run the generator. Some of the waste heat is used to boil water etc. This means that the CCGT is more efficient than a basic coal or nuclear fired steam turbine but it still requires burning large amounts of fossil fuel. So what about the alternatives – renewable energy? If you use the app you’ll notice wind and hydro-electric appearing further down the list. Solar PV despite the recent installation frenzy isn’t large enough to make the list yet.
Both wind and hydro-electric turbines use the same principal – put a turbine in a moving fluid (air or water) and the motion of the fluid turns the turbine which powers a generator. Design of the turbines is engineered to suit the characteristics of the fluid that flows past them of course. These generators are extremely efficient at turning the input energy into useable electricity greater than 70% for a well-designed hydro-electric scheme. There is no waste heat or CO2 released either. And the fuel is free.
Solar PV is much simpler. It is s true twentieth century technology. A simple semi-conductor device (a much simplified version of the chips in your mobile phone and computers) turns sunlight directly into electricity. No moving parts, no noise. Admittedly the best commercially available solar cells are only about 20% efficient at turning sunlight into electricity but as your fuel is zero cost and enough sunlight falls on the surface of the earth in one hour to power the entire world for a whole year it is in plentiful supply.
It is time that we started thinking of renewable energy technologies as our primary source with fossil fuels and nuclear as curiosities to be put in a museum along with the other exhibits from our industrial past.