Original URL: http://www.theregister.co.uk/2008/12/02/smart_fridges_silly_government/

Gov beta test for grid-friendly, carbon-saving smart fridges

'Dynamic demand' could save you several pounds a year!

By Lewis Page

Posted in Science, 2nd December 2008 15:06 GMT

Dynamic demand technology, in which domestic appliances adjust their drain on the national grid so as to smooth out collective spikes and dips, is to get a widespread UK trial next year.

The Guardian, reporting on the new initiative from the Department of Energy and Climate Change, says that three thousand intelligent demand-smoothing fridges will be given away free by the government in a sort of energy-policy beta test.

As any fule kno, the UK national grid's frequency rises and falls from its base level of fifty Hertz in response to demand variations against supply. As more electric power is used, the frequency changes. Once a certain limit is passed, more power stations will come on line and the frequency will move back to the nominal level.

The idea of "dynamic demand", or "intelligent" appliances is that they contain circuitry which monitors the mains frequency. A fridge normally waits until it has warmed up to a certain amount above set temperature, then runs its pumps until it is a certain amount below.

A smart fridge, though, would also take account of the grid frequency. When the grid was under strain it might not bother cooling all the way down - it might stop as soon as it reached, say, the middle of its normal temperature band. Immersion heaters and air conditioning are other examples where dynamic-demand hardware could be useful.

Dynamic demand doesn't reduce the amount of energy required over time - it merely spreads the demand out so as to make things easier on the grid. This is why the government's 2009 smart-fridges must be given away free; they won't offer any savings for their users.

But the quick-response gas turbine power stations used to iron out sudden gaps between supply and demand are dirtier than most - efficient combined-cycle kit can't be thrashed up and down the output scale the way these plants have to be. Thus the government reckons that dynamic-demand tech could could reduce UK carbon emissions, perhaps by as much as 2 million tonnes annually - a little over 1 per cent of the total. That sounds pretty high - even Friends of the Earth, great boosters of this idea, have previously suggested just half a million tonnes a year (one-third of one per cent).

And the power industry would save money on maintenance for thrashed turbines and backup plant which is left idle much of the time, so they're very much in favour of someone else paying to smooth out consumer demand for them.

Greens such as the FoE people like dynamic-demand too, as it could make life easier for renewable power. The thinking goes that the nation's fridges, aircon, immersion heaters etc could be set to take power when the wind was blowing or the sun shining and the grid was thus overpowered, rather than essentially randomly as they do now.

The idea is examined by Professor J C MacKay of Cambridge University in his book Sustainable Energy - Without the Hot Air, just published in hard copy. He says that's not really true.

Popular soap operas such as Coronation Street and EastEnders typically generate TV pick-ups of 600–800MW … automatically switching off every fridge would nearly cover these daily blips of concerted kettle boiling.

Fluctuations in wind power will be a different matter.

MacKay, and other serious analysts who have considered a future UK grid using a high percentage of renewables (probably wind, given the climate), expect significant national supply variations to occur on a scale of days rather than an hour - which is the longest time that dynamic-demand appliances can put off their needs before food begins to rot.

So dynamic-demand consumer appliances aren't a solution for a renewable grid. They offer only minimal carbon savings in the present power picture. And the idea doesn't offer any direct savings for the consumer. Yet the idea is for consumers to pay for it, probably involuntarily - the plan would be to make the tech compulsory on new appliances at some point.

However, the government is keen to suggest that power companies might pass on their savings on maintenance and spare capacity plant in the form of reduced 'leccy bills.

So, if they did, how much would a normal household save?

Well, the Guardian spoke to Paul Lazarevic, whose company will make the dynamic-demand gear for the upcoming government trial. This is, then, an estimate at the higher end of the scale.

"The national grid forecasts a spend of £544m on balancing the grid for the year 2008-09," he said.

"This is passed on to consumers and works out at about £2 on each bill ... Dynamic demand technology could dramatically reduce this charge."

There were 25 million households in the UK as of 2004, so the most a £544m annual cost could add to monthly bills would be £1.81. But in reality domestic customers use less than half the electricity consumed in the UK. If you take it that industry bears a similar responsibility for grid balancing, and accept Mr Lazarevic's figures on cost, the annual saving to the consumer of completely eliminating the need for grid balancing would be in the order of £10.

Since dynamic demand can't do that (completely eliminate the need for grid balancing), we'd be looking at perhaps a few pounds per year at the moment; the tech could theoretically pay its way in the case of an appliance lasting years, as it wouldn't cost much.

In the wind-heavy grid of the future, unfortunately, we'd be looking at a very serious increase in balancing costs, whether from dirty inefficient turbines or (more expensively yet) from nice clean pumped-storage hydropower. Clever fridges may be able to iron out demand spikes, but not the much bigger ones to be expected from a renewable supply side.

The Guardian piece is here. ®