Coping with Variability

Demand Flexibility, Micro-CHP and the Informated Grid

Dr Bob EverettOpen University EERU

The privatised UK electricity industry has concentrated on the mass production and distribution of electricity

Perhaps it should be looking more at how the energy service requirements of their customers; illumination, warm homes and refrigeration can be made more flexible to help cope with variability of supply

If variability and two-shifting is such a problem, why don’t we get rid of some of it by promoting off-peak heating? - as the French did in the 1970s and 80s….

What are the problems of the variability of wind power?

Problem 1: The wind blows for a bit and then stops..

…and then starts again

Simulated Wind Turbine O/PMilton Keynes - December 1982

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But it isn’t totally random...

In this data set there is a slight daily cyclic variation and another of approximately 5.5 days

Wind power autocorrelation functionMilton Keynes winter 82/3

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Time lag - days

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Problem 2:

It may be possible to predict accurately the strength of approaching winds in a weather front, but not exactly when it will arrive plus or minus an hour

So we’d like:

Some long term demand flexibility of the order of several days

Lots of short term demand flexibility of around an hour

What’s on offer?

During the 1999 solar eclipse UK electricity demand fell by 2.2 GW in 20 minutes - just because lots of people found something better to do than work

Picture: National Grid

This A++ rated freezer will keep your food frozen for 64 hours after a mains interruption - alas its only rated at 115 watts

Picture: Miele

In my home I have water heating using an off-peak water heater with a 3 kW element. I don’t care exactly when it is heated up as long as I get a hot bath in the morning

My fridge is rated at 150 watts and cycles approximately once every three-quarters of an hour. I’m sure that it could be delayed by 30 minutes without any problems

The company Dynamic Demand has been promoting the use of fridges in conjunction with mains frequency sensors, essentially to carry out the standing reserve function of ‘frequency service’

This report argues that it makes no sense to sell electricity without a parallel flow of information about its use - we need a proper ‘informated grid’

If it can be put in place then new ways of buying and selling electricity will arise

Domestic metering is stuck in a bygone age

We have advanced only slightly from this mid-Victorian (gas) meter

This is my home electricity meter (installed 1997)

A spinning disk meter (invented circa 1890) with a radio controlled tariff time switch.

Even this does not actually control when my immersion heater comes on - that’s controlled by a timeclock set by me.

There have been UK studies on the problems of metering, for example net metering of domestic PV, but there is an unwillingness to pay for the necessary complex meters.

So - how will we get to an ‘informated grid’?

A new factor - Domestic Micro CHP

Philips StirlingEngine200W

generator1950

Whispergenpackaged

1.2 kW CHP2004

Experimental1kW CHP unit

1991

In the early days of small scale (circa 100 kW) CHP in the 1980s equipment reliability was transformed by ‘informating’ it.

Modem links to the suppliers allowed on-line monitoring and fault diagnosis. Servicing and rapid repairs could be carried out before problems became serious, expensive and embarrasing.

The market potential for domestic micro-CHP units is reckoned to be in the millions. This represents at least a gigawatt of generation capacity

Will this be the first domestic plant to be ‘informated’?

On-line monitoring could give increased reliability and consumer confidence and allow the design to be pushed to higher efficiencies

Picture: Whispergen

Once the information link is there then there is no reason why domestic CHP plant and other domestic devices such as fridges should not be remotely and flexibly controlled

This just leaves the questions: ‘Who will do the controlling?’ ‘How will they interface with the

current market structure?