Physics can be difficult to learn, but this blog aims to help you get into physics by connecting your GCSE physics lessons with things you see in the world around you.

## Wednesday, 28 September 2011

### A Fair Exchange Is No Robbery

In today’s world where electricity can be had at the flick of a switch or the push of a button it’s all too easy to ignore how it gets made, and that for the most part in the UK, we use fossil fuels to produce it. How we convert coal into something that can be used without any fuss, mess, or heat is pretty much a mystery to the general public, but never fear, I’m here to help you answer your burning questions (groan) on getting power from that black stuff.

It all starts with the raw materials, coal in this case, being burned in a huge oven. The heat is the useful part, and this is used to heat up water via a heat exchanger. This involves pumping water through a series of pipes that come into contact with the heat. The larger the surface area the better the heat exchange will be.

This creates high pressure steam from the cold water and this is what is needed to drive the turbines, much like trains used to be powered by steam before the petrol engine was invented. The steam is forced through the turbines, which makes them spin. This spin can then be used to create electrical power through the dynamo effect.

The electrical power then goes directly into the National Grid, from where it goes to anything that needs it. Seems like a simple enough process but let’s just look at the drawbacks too. Firstly, this relies on fossil fuels, which are becoming more scarce, and secondly, there are a lot of energy exchange processes going on here.

The problem with energy exchange is that it’s never a perfect swap, some of the energy is always lost as heat, light or sound and here is no exception. This process is a very hot one, so heat is the biggest way this process loses energy, with some to light as well. The more steps the worse the loss is. Let’s imagine each phase is 70% efficient, and see how much energy we come out with at the other end.

So in this example, only 35% of the energy in coal actually goes to making electricity. Whilst this amount is quite shocking, it’s not too far from the mark in some cases, like really old power stations. Newer versions are slightly more efficient, but surely one way to protect our natural resources would be to really maximise the energy that we do get?