Tuesday, 9 September 2014

How to avoid brown-outs this winter

Since four EDF nuclear reactors are likely to be shut down until next year the chance of brown-outs this winter is looking increasingly likely [1]. There just isn't enough generating capacity on the grid to allow for any more problems. However, there are only a few hours a day when electricity demand is at its peak. Is there something we can do about this?


The chart below shows the electricity demand through the day in December 2013 - normally the worst month of the year. The solid line shows the mean demand and the dashed line shows the maximum on any day. The peak is at about 5.30pm in both cases. That is about the time when offices and businesses are starting to shut down but domestic demand is picking up. The total demand rises rapidly and tails off more slowly. It is still pretty high at 7pm.
Total electricity demand in December 2013 [2]
The peak on the solid line is about 46.7GW and on the dashed line it is 51.6 GW.
The next chart shows average household demand from the Household Electricity Survey (HES) in December 2010. This chart is based on 61 households that were monitored at that time. The HES was a very detailed survey where instead of measuring just the whole house electricity consumption most appliances were monitored individually. This means we have a reasonable idea of how much is being used for what [3].
Electricity demand from 61 households in the Household Electricity Survey in December 2010 [3]
The peak starts ramping up about 5pm and it is mostly lighting, cooking and audiovisual appliances - TVs, hifi, games machines and so on. There is also an increase in unknown consumption: appliances that were not monitored. We have no idea what that is - it could be more lights or other things.

Now the HES was conducted in 2010/2011 and things might have changed a bit since then. For example, maybe we have replaced more of our lights with energy efficient ones - but maybe also we have more TVs and games consoles with bigger screens.

The overall peak demand from the HES is about 1.1 kW per household (on average). Since there are about 27 million households, if the HES is representative they would be using about 30 GW. This is about two thirds of the total electricity consumption at that time. Offices and businesses can help too but households can make a big difference. So what can we do?

Convert to energy efficient lighting now
Which light fittings do you use on dark winter evenings? Have they all got CFL or LED light bulbs in them? If not - why not replace them now? If you replace a 60W incandescent with an 11W CFL and you use it 4 hours per day then it will save you about 18p/week. It will pay for itself in less than three months.

Don't switch on the TV unless you are actually going to watch it
Do you automatically switch the TV on when you come in, then wander into the kitchen to start cooking, or go and check on the children, or... Well don't! If you aren't going to watch it, don't turn it on. That goes for the children too - if they have homework to do then they don't need the TV on until they have finished. The same goes for lighting. Don't turn the living room lights on unless you are going to stay in it.

Don't run the washing machine between 5 and 7pm
If you can, leave running the washing machine, tumble dryer or dishwasher until after 7pm. This is only about 7% of the peak demand but it is probably the easiest to shift to off-peak.

Use the slow cooker
Cooking comes to about 12% of the peak domestic demand, even though many people use gas which is not relevant here. Using a slow cooker probably doesn't save electricity overall but it does shift demand out of the peak time. So maybe if there is a brown-out warning you could do a slow-cook casserole that day instead of baking something in your electric oven.

Make sure that you buy energy efficient appliances.
Buying energy efficient appliances may or may not save you money at today's energy prices but they use less energy. This insulates you against future price rises and, for appliances that are on at peak times, it also reduces peak demand. For example fridges and freezers are on all the time and contribute about 5% of the peak domestic demand.

Also, you can do things at work to reduce demand more quickly between 5pm and 7pm.

Switch off lights at work even if you aren't the last to leave
One or two people left in the office don't need all the lighting left on - just the bits where they are working. So, when you leave you can turn things off that no-one else is using. Then the last people left in the office should turn off the last lights.

Also, it is not too late for your firm to take part in the Electricity Demand Reduction Pilot, and remember that there are tax advantages for investing in energy saving measures in businesses.

Some of these ideas save energy overall and some of them just shift it. Most of these ideas are things you could do every day, and some are things you might do just when we have a brown-out warning.

I remember the power cuts in the 70s due to the miners' strike. Even though I was just a kid then and it was quite fun eating supper by candlelight the cuts weren't all good. I couldn't do my homework or watch TV. Boiling water for tea on a primus stove took ages. My parents didn't think it was fun at all. Well we probably won't have much actual power cuts this winter - and we certainly won't if we  take a bit of extra care.


[1] What exactly is a brown-out and is Britain going to have them (Guardian) Sep 8 2014
[2] Historical Demand Data (www2.nationalgrid.com)
[3] Household Energy Survey Spreadsheet Tools For Users (www.gov.uk) July 2014

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