Wednesday 25 November 2015


Getting steamed up about heat loss

Like most people you are probably horrified by the recent increases in gas and electricity prices.

Power station: Steam from cooling towers could be used to heat housing

EDF Energy has announced rises of 22 per cent for gas and 17 per cent for electricity. Centrica, the owner of British Gas, has announced a whopping increase of 35 per cent in the price of domestic gas.

For the owner of the average house this will take the energy costs of running a house to well above £1,000 and push an increasing number of families into “fuel poverty” (where they spend more than 10 per cent of their disposable income on heating and electricity).

For many people this is causing them to change their energy use. Suddenly installing insulation, turning down the thermostat, replacing light bulbs, and switching off computers, routers and televisions at night, is becoming a serious proposition because doing so can make a significant difference to one’s outgoings.

But what if I told you that the electricity generators actually throw away and waste 60 per cent of the energy contained in the gas or coal that they burn in their power stations? Would you be completely outraged?

Would you be tempted to steal one of those useless “For Sale” placards from one of the houses further down your street, turn the panels round, write “Electricity Generators Are Profligate Toerags”, and lay siege to the Palace of Westminster in much the same way as the truckers did recently?

As common sense takes hold, however, we need to ask some questions. How on earth can profitmaking companies, in a competitive business environment, with activist shareholders, be so incredibly wasteful? Why isn’t there some bright spark out there who can find a way to up the efficiency? Surely that would be a license to print money.

To understand this, we need to explore how electricity generation works.

An electricity power station consists of three parts. First we have a boiler where coal, gas, or nuclear fuel is “burnt” to generate very hot gas (steam, for example). The huge pressure generated by heating the gas is then used to turn a turbine that generates the electricity.

Finally, the spent steam is condensed to water – those white clouds that billow from the huge cooling towers that stand beside our power stations are not pollution – just clouds of moisture billowing in the breeze.

What we are doing, in essence, is using the temperature difference between the boiler and the cooling tower to drive the turbine that generates the actual electricity. The efficiency of such a system is something that physicists have worried about for almost 200 years, ever since engineers started building the steam engines that drove the Industrial Revolution.

It boils down to this: the efficiency of an engine (or of a power station) is determined by the temperature difference itself – the bigger the difference, the more efficient the engine.

If you look at the latest gas turbine technology, you can reach efficiencies as high as 60 per cent. But in practice, and particularly with our older power stations, 40 per cent is very common.

So what happens to the rest of the energy? That’s the elephant in the room: it is just wasted – as heat. It is just dumped into rivers, or forms those clouds that warm the atmosphere around the power station.

You might be tempted to ask why we don’t use a refrigerator to increase the efficiency? The problem is that we need energy to run the fridge and so the process is self-defeating.

There is no way round this problem. It is an immutable fact of our universe – it is the Second Law of Thermodynamics. So perhaps the power generators aren’t perpetrating quite the con I was suggesting at the outset – they are just doing the best they can in the circumstances.

But wait a second. Most of us only use electricity to run the lights, the cooker, and the television in our houses. We still need to heat them.

What if we took all that wasted heat from the power stations and used it to heat our homes? In that case the heat would not be wasted. We just wouldn’t need those expensive condensing boilers in our houses and would get the heat almost for free as a side-product of electricity generation.

This is precisely the idea of combined heating and power (CHP), a way in which the efficiency of a power station can be increased to close 90 per cent. But with power stations located many miles away in the countryside – think of all those concrete cooling towers you see as you drive along the motorway, which dwarf even the new wind turbines that are springing up all over the country – there is no way to pipe that heat into people’s homes.

This is something we need to think about at a time when many of our power stations are coming to the end of their useful life, when North Sea oil and gas are running out, and where concerns about our national security and the environment suggest we should be using all of our fuels as carefully as we can.

What we need is a rethink about the way we generate electricity. Once upon a time electricity power stations were located in the middle of our cities – just in London think of what is now Tate Modern or the magnificent wreck of Battersea Power Station.

In those days, had anyone thought of it, it would have been possible to provide heating and hot water for the neighbourhood, as well as the electricity.

Over time, however, rising land values and the smoke produced by the old coal-fired plants meant that we moved all of our power plants to the country where the “waste” heat is just thrown away.

But because of this distance we have to run cables for hundreds of miles across the country. The electricity running through those generates even more “waste” heat, reducing the efficiency of our electricity system even further.

Can we change this? Yes we can, and we can do that without having to build power stations the size of Tate Modern in a place like Kingsnorth.

The answer is to generate electricity locally and export any excess to the local energy grid. UCL, the University I work for, for example, heats and powers its entire campus using combined heating and power (CHP), saving itself huge sums every year, not to mention carbon emissions.

It outrages me to see big housing developments going up around London advertising “luxurious underfloor heating”. The electricity, energy that we could all be using to run our domestic appliances, lights and electronics, is instead deliberately turned into the least useful kind of energy of all – heat.

If each of these blocks of 20 or more flats had its own CHP plant they could generate all their own electricity, and in many cases export it to the Grid, while providing free heating and hot water for residents.

In the summer time the waste heat could be pumped into the ground and stored in the rocks deep underground, to be recovered in winter. In doing so, they would halve their fuel requirements, and therefore their running costs.

But this costs money. The big developers have little interest in the long term costs of their buyers, but care a lot about maximising returns to their shareholders. So naturally they want to build their developments as fast and as cheaply as possible, perhaps putting a couple of solar panels on the roof as a kind of greenwash to attract the punters.

The fact is that electrical underfloor heating systems can be laid in minutes and then be marketed as a “luxury” benefit. By contrast, putting in heating pipes and power plants adds to their construction costs, which they are terrified of passing on to their buyers, even if, in the long run, it would make an enormous difference to the energy bills for the residents.

But by not investing in CHP from the outset, we are seeing some incredible wasted opportunities to reduce our need for oil and gas, more and more of which will be imported in the future as our North Sea reserves are depleted.

It is a kind of passive decision that will have enormous foreign policy implications in the future (where are we going to get our gas from as the North Sea runs out? And what kind of compromises will be forced into by the countries we buy them from?)

It is also a huge wasted opportunity to reduce our carbon emissions painlessly without requiring us to go back to living in caves.

But before everyone runs out to get their local plumber to replace their boiler with a micro-CHP plant, a few words of caution. It is not for everyone. Because it requires significant infrastructure investment it is only effective if applied on a large scale.

There are domestic microCHP units for sale (for example, the WhisperGen Heat and Power system), but initial tests by the Energy Saving Trust have been disappointing and the benefits of these small systems appear to be, at best, marginal.

But it is quite a different matter if blocks of flats or new large new developments are heated and powered by a larger unit. The savings are then quite spectacular.

So what should we do? We have to lobby the Government to introduce requirements that all new developments, domestic or commercial – shopping centres, office blocks, housing estates, blocks of flats – be equipped with CHP plants. We need to press our energy suppliers to open up to a new model of powering our country.

And aside from the efficiency gains, a Grid powered by a large number of smaller power units distributed discreetly all over our cities is likely to be far more robust to breakdown, failure, even terrorism, than what we have now.

Small power stations integrated into buildings will get around the planning problems that dog our major energy infrastructure projects. And using fuels more efficiently will both improve our energy security while helping us achieve those ever more elusive climate targets.

Dr Andrea Sella is a lecturer at University College London

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