POWER!

PylonsThis was originally written as a comment to this post by Robert Llewellyn. However as you can see, it got completely out of hand, so I had to turn it into a blog post and then create a blog to post it on. I blame Mr. Llewellyn for this and intend to find some way to punish him in the future!

The main problem with the media coverage of future energy issues is that it is impossible to do it sensibly in a three minute slot on the Today or any other program. Power engineering is an enormously complex subject, with many factors to take into consideration before making decisions. Very few people understand these factors outside the industry, because nobody is given the time or attention to explain them.

Well I’m going to have a go at explaining some of them and how they link together. I started my career with the Eastern Electricity Board (remember them?) and I’ve spent most of my time since doing electrical engineering of one sort or another. This is mainly an attempt to show the number of factors that push and pull at every decision in power engineering, not an endorsement for either side of an argument.

The factors that have to be taken into account can be split into four types:

 

Power Budget

This is a calculation of all the losses in a power generation, distribution and consumption chain. It’s where some people (including myself) would consider the ‘real’ engineering gets done, but it has to be done with reference to the other three types of factor below in all cases.

Energy is lost in all stages of the system. Here are a few examples of how that happens:

Conversion loss

Whether you’re converting wind energy to electricity, chemical energy to motive power or nuclear energy to heat, there are always losses. Most of these losses are in the form of heat, but they can also include inefficiencies in wind turbine blade design or the effects of dirt on solar panels. Conversion losses also happen at the consumption end of the chain and these are usually greater than the generation losses.

 Distribution loss

In electrical energy distribution systems this is caused by heating (I┬▓R) losses in conductors. By increasing the voltage and decreasing the current in the grid, losses can be reduced to a minimum without having to use prohibitively thick conductors. However, this then means that you have to build huge pylons to hold the conductors far enough apart to avoid arcing. Superconductors have next to no loss, but they have to be kept at a very low temperature to work, which in itself takes power. Superconducting materials are also very expensive.

Cost

All energy and materials are free! Sounds good doesn’t it, but in most cases you have to dig it out of the ground to use it, with all the manpower and environmental cost that entails. Engineers always have to be mindful of these costs and the customers willingness to pay when designing a system.

A good example of this is the cost of copper in a distribution system. If you could halve the losses in the grid by doubling the conductor size (this is not quite true), would it be worth doing? First you have to dig up a huge amount of copper ore and then process it. These two operations are hugely costly in manpower and environmental damage. You also have to strengthen all the pylons to cope with the extra weight and wind loading. This also has a huge manpower and environmental cost. Then you have to install the new conductors. This just isn’t economically viable and there are much more cost effective ways to increase the efficiency of the system.

One way to reduce the cost of materials is to use energy sources you don’t need to dig or pump out of the ground. Wind, wave, solar and water current energy are all freely available with no manpower cost involved in obtaining them. However, they do have the drawback of not being transportable or in most cases storable. The power conversion must always take place on-site at the time it is available. This increases the distribution losses and costs, which is where this all started for god sake!

There is also a cost at the end of a generation or distribution systems life. With nuclear this can be more the the total cost of production.

Reliability

All forms of energy are useless unless they are available in the amounts required and at the times they are needed. This is a big problem with electricity. If you are reading this on a computer plugged into the mains, then the power you are using was generated less than a tenth of a second ago. No more and no less power can be fed into an electricity distribution system in any moment than is being used by the consumers in that moment. The storage of large amounts of electrical energy is currently too inefficient and costly to be viable, although this may change in the future. That does not mean all types of electrical generation have to be supplying a constant and reliable amount of energy all the time.

The grid is fed by coal, gas , nuclear, wind, solar, oil, hydro and other types of generators. All of them have to be balanced for cost, environmental impact and risk as they are being used by the distributors. But most importantly, they have to be used in such a way that reliability of supply can be maintained with widely fluctuating demands.

Risks

This includes risks to life and limb, the environment and other infrastructure. This is where politicians and pressure groups really queer the pitch! Engineers (and most normal people) define risk as the probability of something harmful happening based on what has happened previously. All human activity has potential risk, unfortunately most of us confuse our fears with risk. You may be afraid of flying, but it’s far more probable that you will die whilst driving to or from the airport than in a plane crash.

Coal mining, drilling for oil and burning the products of both have a huge risk to life and limb of both the workers and the public, as well as the environment. Wind turbines and solar panels have low risks, but they are by no means risk free. There are always potential dangers when you are trying to control huge amounts of power and these can never be entirely mitigated.

Contrary to popular belief, nuclear energy has proved to be a relatively low risk to life and limb. What most of us think we know about nuclear energy has come to us through pressure groups and science fiction, but the reality is that very few people have been killed or injured by nuclear power generation. Again, I stress that I am talking about measurable risk, not fear.

 

That is a by no means complete set of factors involved with power engineering. But I think it should give a taste of the complexity of the problem. I hope it has informed more than it has confused.

If you want to learn more, a Google search is a good place to start. I also recommend having a look at some of the papers on the IET and IEEE web sites, they’re written by far brighter people than me.

You might like to take a look at the Fully Charged series by Robert Llewellyn on YouTube. He’s a bit thick, but he does have some properly clever people on the show. That’s the first part of my revenge!

If you disagree with anything I’ve written or you think I’ve missed something out, then please do let me know in the comments below. Although I will try not to censor any disagreement with me and my efforts, I will moderate all comments for bad language and general nastiness.

2 thoughts on “POWER!

  1. You mention copper in the distribution system. As I understand it, the conductors running between pylons are made of aluminium. Not quite as good a conductor as copper but a lot lighter, reducing the mechanical load on the pylons.

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