Tag Archives: electricity

UK Energy Mix

A lot of people get confused between the electricity they use and the energy they use.

It’s easy to forget that the majority of people use natural gas for heating (e.g. a gas-fired central heating system) and cooking and petrol for transport; electricity only makes up a small part of the mix.

The graph below shows how the UK’s “energy mix” has changed over the last forty years.

Electrification peaked between 1994 and 1998, the same time that nuclear power was at it’s peak in the UK. Greater electrification would be a benefit to the environment as electricity is a low-carbon fuel, especially when nuclear and renewables make a large contribution to the fuel mix. Also the “Dash for Gas” in the ’90s is clearly visible as a very marked increase in the size of the blue section.

Electricity consumption in the production of aluminium

Aluminium is a very useful metal; it is the most widely used non-ferrous* metal in the world. It has a very low electrical resistance and a very good strength-to-weight ratio and has therefore found many applications: from packaging in drinks cans and foil wrapping to aeroplane parts and power lines.

Luckily, aluminium is very common, making up about 8% by mass of the Earth’s crust (only silicon and oxygen are more abundant). Unfortunately aluminium is also very reactive so is never found in isolation like gold and silver are, but rather as a compound in one of 270 different minerals.

Aluminium is usually produced by extracted from bauxite, an ore made from a mixture of aluminium hydroxide, iron oxide, titanium dioxide and kaolinite.† Because it is so reactive aluminium cannot be extracted economically using chemical processes; instead it is extracted by electrolysis in the Hall-Héroult process.

A bank of Hall-Héroult cells

The Hall-Héroult process uses a huge amount of electricity; hundreds of thousands of amperes are used in each cell and a single plant may contain hundreds of cells connected in series. According to Alcoa, the world’s largest producer of aluminium, the best smelters use about 13 kilowatt hours (46.8 megajoules) of electrical energy to produce one kilogram of aluminium; the worldwide average is closer to 15 kWh/kg (54 MJ/kg).

Worldwide production of aluminium in 2010 was 41.4 million tonnes. Using the figures above this means that 621 billion kilowatt hours of electrical energy were used in the production of aluminium. To put that in perspective, the total world production of electrical energy was 20261 billion kilowatt hours, meaning that more than 3% of the world’s entire electrical supply went to extraction of aluminium.

During the same period Australia, one of the world’s largest producers of aluminium‡, produced about two million tonnes of aluminium and 250 billion kilowatt hours of electrical energy; this means that more than 12% of its electrical supply was used to extract aluminium.

The output of the Kárahnjúkar Hydroelectric Plant in Iceland is devoted entirely to the Fjardaál aluminium smelter. There has been a great deal of conflict about the environmental impact that the building of this dam has created. (via @declanfleming.)

* The ferrous metals are those that contain iron; steel is the most common ferrous metal.

† Bauxite contains aluminium in gibbsite, boehmite and diaspore; iron in goethite and haematite; aluminium and silicon in kaolinite; and titanium in anatase.

‡ Australia is the world’s fourth largest aluminium producer and the largest producer, by a very substantial margin, of both aluminium oxide and raw bauxite; the red colour of Australia’s deserts comes in a large part from the presence of bauxite.

Fuel Mix and CO2

Since 2005 UK electricity suppliers have been legally obliged by Ofgem to provide information about the fuel mix they use to generate electricity and the carbon dioxide they produce in the process.

The UK average fuel mix; heavy on gas and coal.

The “Big 6” energy suppliers supply 99% of the UK population between them; most have a fairly similar energy mix, but one stands out from all the rest.

Most of the Big 6 are heavily reliant on natural gas and coal; but EDF stands out by generating more than 60% of its electricity from nuclear power. The effect that this has on the amount of CO2 that it creates for every kilowatt-hour of energy produced is very noticeable.

EDF Energy is a subsidiary of Électricité de France, so it’s no surprise to see it relying on nuclear power; France generates 78% of its electricity from nuclear power and is the world’s largest electricity exporter. This has enabled Électricité de France to become the world’s largest utility company.

Source for fuel mix data: ElectricityInfo.org

This is why you always put a 1kΩ resistor in series with an LED

It’s always a good idea to wire a 1kΩ resistor in series with any LEDs you use in order to limit the current, and this is why:

Usually the resistor just burns out, but this LED was entirely different – it split right in half! I’m still not quite sure why, but Occam’s Razor states that it’s more likely to be a manufacturing defect rather than some new phenomenon.

Thanks to my colleague PAS for bringing this to my attention.

Pylon of the Month

This month’s Pylon of the Month is a beauty, even if it is only an artist’s impression.

Designed by Hugh Dutton Associates for a competition run by the Italian electricity transmission company Terna, the new pylons would cost three times as much as standard pylons, but would still save money by reducing the overall length of the power lines.

Images taken from the HDA flickr stream.