- Climate change
Image source, Khalid AbdullaImage caption, Khalid's hot water tank automatically switches on when power is most plentiful – and cheapest
Imagine your future home as an energy hub storing electricity from the grid when clean wind power is plentiful, and then selling it back – at a profit – when demand surges elsewhere.
For Sussex grandmother Kate Giammatteo, that future is happening right now.
She has batteries bolted to the front of her Worthing flat that do just that, and they are forecast to cut her energy bill by £173 a year.
And what's good for Kate will be good for the country, because as the UK shifts to electric heating and electric cars to meet its climate goals, the demand for electricity is expected to double by 2050.
Already the sector is under pressure to ramp up renewables, because Prime Minister Boris Johnson has mandated that all electricity must come from zero-carbon sources by 2035.
Much of the extra energy will be generated by wind power, which is clean and cheap – but – of course – dependent on the wind.
That leaves an intermittent hole in supplies. This can be by increasing energy storage using batteries or other technologies – but experts say part of the gap can be filled by enabling consumers to use electricity more flexibly.
That's where Kate fits in. The tale of her giant battery offers a glimpse of an energy future in which appliances will use power when it's plentiful, and conserve it when it's scarce.
Image source, Kate GiammatteoImage caption, Kate has a battery at home that can store up energy from renewable power sources
So, you could allow your freezer to turn off for a short time to save power, and your washing machine to switch itself on in the afternoon to use cheap power.
Khalid Abdulla, an engineer from Edinburgh, has a hot water tank from a firm called Mixergy that's automatically switched on by his energy supplier's computer when power is cheapest (it can be overruled manually).
The tank's insulation ensures the water remains hot whenever Khalid's ready for a shower. In effect, he's storing energy in hot water.
It will save Khalid money. And the technology has brought a bonus – the new system has allowed him to dispense with his second water tank, and free up storage for the paraphernalia that accompanies a new baby.
But this energy revolution stretches beyond the home, because more and more businesses are being paid by electricity suppliers to use the grid differently.
When supplies are plentiful, big refrigeration plants can utilise the power to chill their freezers even harder. Then when there's a surge in demand, they can power down as the freezer temperatures slip back to normal.
They are paid in effect for storing energy through cold. Some hotels do the same with their air conditioning. Some asphalt plants are super-heating the asphalt when power is cheap – then allowing the temperature to drop as demand peaks.
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Big prices are charged by firms volunteering to turn off their power for a spell when it's needed elsewhere. The steel giant Corus has offered to switch off its supply from time to time for £45,000 per Megawatt. One estimate suggests the value of the flex-elecs market by 2030 will be £2.4bn a year.
One firm involved in a UK government trial, Geo, claimed it showed a DSR system could save 49% on utility bills for homes with electrical heating and electric cars. There would be CO2 savings, too.
"They are pretty amazing figures, but they are achievable in the majority of homes as time goes on," its CEO, Steve Cunningham, told me.
What's more, those savings were achieved using only major contributors such as home heating and hot water. Even more cash would have been saved, he said, if appliances such as freezers and washing machines were fitted with smart plugs so they could also be controlled individually from afar.
He said smart thermostats costing £25 could save gas heating by learning how fast a house heats up and cools down, and adjusting boiler use accordingly. "It's tragic that people who most need tech like this can't afford to access it," he said.
So how big a role can reducing demand play in smoothing the peaks of electricity use? Sara Walker, reader in energy at Newcastle University, says it needs a big push from policy-makers.
She told me: "There's great potential but there appears little attention on the subject at government level. We really need a strong policy signal – and we're not getting it."
Follow Roger on Twitter @rharrabin
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