‘Shaving the Peak’
or
How energy conscious people can help keep the lights on for everybody
Chris Goodall
When electricity demand is high, the UK has little spare generating capacity
Source: National Grid Winter Outlook, October 2014
Expected supply
Reserve
Peak demand in the AVERAGE winter
Spare Other sources that can be called on
58.2 GW 55.0 GW
3.4 GW of margin
When electricity demand is very high, the UK has almost no spare generating capacity
Source: National Grid Winter Outlook, October 2014
Expected supply
Reserve
Peak demand in A VERY COLD winter
Spare Other sources that can be called on
58.2 GW 56.3 GW
2.1 GW of margin
So we have a bit spare?
• Probably
• But
• National Grid really underestimates the increasing frailty of UK power generation capacity, particularly old nuclear.
• And assumes that about a quarter of the UK’s maximum wind power is arriving at the time of peak demand
• So, particularly for the next few years, it makes sense to ‘shave the peak’
0
10
20
30
40
50
60
UK electricity demand 23rd January 2014*
Source: BM reports
Gigawatts
* Highest electricity demand this year
0
10
20
30
40
50
60
Falls a bit to 3.30 pm
UK electricity demand 23rd January 2014
Minimum about 31 GW at 4.30 am
Reaches 46 GW by 9am
Rises sharply to peak of over 52 GW between 5 and 6 pm
Falls back below 46 GW by 9pm
Gigawatts
Source: BM reports
UK electricity demand 23rd January 2014
0
10
20
30
40
50
60‘ Shaving the Peak ’
Gigawatts
40
42
44
46
48
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52
54
3.30 4.00 4.30 5.00 5.30 6.00 6.30 7.00 7.30 8.00 8.30 9.00 9.30
Gigawatts
UK electricity demand 23rd January 2014 - portion
7 GW increase over less than 2 hours
Does shaving the peak matter?
• Yes
• Means we are less likely to have power cuts
• And the UK has to spend less on building power stations to meet peak needs. (Overall electricity demand is falling).
• And, importantly, we’ll not have to build as much extra network capacity to move electricity from one place to another
• Charges from National Grid to buy and sell power to match supply and demand will fall
• Will also reduce CO2 emissions
• The peak is powered by fossil fuels• The process of ramping fossil fuel plants up and down wastes energy• Unexpected peaks can result in grossly inefficient generators – using large amounts of fuel –
being brought into operation
Extra demand between 3.30 and 5.30 pm
23rd January
Gas fired power stations turned on
Coal increase
‘Pumped storage’ increase
7.3 GW1.3 GW
0.5 GW4.6 GW
0.9 GW
Other
Includes 0.2 GW ofOil. Only used in emergencies
How did the UK supply the extra electricity at peak on 23rd January?
Source: DECC Household Electricity Survey: a study of domestic electrical product usage
The shape of electricity demand from homes
12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12
800
600
400
200
0
700 watts at 5.30
400 watts at 3.30
Average household electricity demand in winter
Watts
Time
Midnight Noon Midnight
Source: Stylisation of previous chart
• 300 watts increase between 3.30 and 5.30pm.
• 27 million UK households
• 300 watts times 27 million households = 7.1 GW
Surely 300 watts per household is pretty unimportant?
• No
7.3 GW7.1 GW*
Total increase in electricity demand,
3.30 to 5.30, 23rd
January
Estimated increase in household electricity use,3.30 to 5.30 on average
winter day
The increase in household energy use is the reason for the peak in electricity use
* Without considering the extra effect of power losses in the Grid
Where is the household demand coming from?
Data from coldest day of study period in 2010
Source: DECC Household Electricity Survey: a study of domestic electrical product usage
Average winter day Coldest winter day
700 watts
850 watts
Household electricity need is even greater on days of peak demand
Source: DECC Household Electricity Survey: a study of domestic electrical product usage
Cooking
Lighting
Audiovisual kit
Cold appliances
250 watts
220 watts
110 watts
60 watts
Total of these four appliance types About 640 watts
Contribution to household electricity demand on the coldest day
How much might reducing these figures mean for total UK electricity demand?
2.1 GW
National Grid 2014 forecast of spare
capacity at peak in very cold winter
Cut peak household demand by 200 watts
Cut peak household demand by 100 watts
2.7 GW
5.4 GW
• Can we persuade people to
• Cook with gas not electricity (65% ovens are electric)?
• Cook after 6.30 (shaving peak)?
• Buy induction ovens if they still want to use electricity (saves c. 30%)?
• Or use a slow cooker with timer (takes majority of energy need off the peak)?
• Use microwaves, not hobs (saving up to 80%, depending on food)?
• All good ideas. Probably impractical?
Cooking is the biggest contributor to evening peak household demand
A fancy new induction oven – only £699.99
Audovisual is the third biggest source of known electricity demand at peak
• A lost cause?
• LED televisions use much less electricity in use than LCDs
• Plasma uses more
• Don’t think we’re going to get people to watch TV later or buy a new LED screen in order to shave peak demand
If every home had a 60 inch plasma TV on at the same time – 4 GW demand
What about putting in solar panels and then using surplus power early in the evening?
• A good idea in theory
• But in deep winter, little electricity to store for the 5.30 pm peak
• And very expensive – Germany system shown here costs many thousands of Euros. Not yet competitive with simply reducing early evening demand
Sonnenbatterie – 4.5 kWh
That leaves lighting and cold appliances …..
• Lighting – move from standard energy saving bulbs to LEDs. Focus on switching halogens out
• Fridges and freezers – automatically turn them off when UK electricity demand gets too high
Fridges and freezers
• 60 watts average per house. At peak, possibly about 1.5 GW
• (But on coldest day, when electricity demand is highest, will fridges and freezers actually not need to work as much as on average??)
• A good idea, but can probably only be done extensively with new fridges/freezers?? Replacement cycle is 10+ years
Minor hardware changes to make fridges and freezers turn off when demand is high
Lighting: should we ban halogen bulbs?
• Probably the easiest and cheapest way to get substantial peak shaving
• Most important change is to move from halogen bulbs to LEDs
• Some cost to homeowners but quick payback
What do halogen bulbs look like?
or
LEDs are similar in size and shape
Probably 500 watts of halogen lights in this kitchen…
Modern kitchens and bathrooms are chock-full of halogens
Why does switching to LEDs make sense?
Halogens are slightly more efficient incandescent bulbs than the old GLS type.
Source: US Energy Information Agency
• LEDs – now about 6 times as efficient as halogen bulbs
• Still only a bit more efficient than Compact Fluorescent, but getting better all the time
• (IKEA will only sell LEDs by end 2017 – it’s not mad to talk about banning halogens).
Mostly halogen now
Some halogen
Where do we put halogen bulbs?
Source: DECC Household Electricity Survey: a study of domestic electrical product usage
Over half total installed wattage of lighting in UK homes now appears to be halogen (This is a considered guess on my part)
The average amount of halogen wattage is probably about 500 watts per home
160 watts
320 watts
Kitchen
Elsewhere
Wattage Percentage on at peakelectricity demand
60%60%
20%
= 96 watts
= 64 watts
160 watts
Average usage at peak
How much could shave peak household demand switching from halogens to LEDs?
Replace 8 * 20 watt halogens in kitchen with 8 * 4 watt LED
Cost About £60
Benefit
Reduce electricity use by 100 kWh/year About £13
Reduce bills for buying 2-3halogens/year About £5
Total About £18
Payback About 3 years, 4 months
The economics look reasonably good
Usage now of halogen at peak about 160 watts
Replacing with LEDs will reduce to about 30 watts
Saving about 130 watts
Across all UK homes will shave peak by about 3.5 GW (nearly tripling spare capacity in coldest winter)
(Technical note will reduce UK capacity payment requirement by about £10 a home a year)
The social benefit
What does this mean for Cambridge University?
• A campaign to replace halogens (and possibly ‘energy-efficient bulbs) with LEDs in colleges, laboratories and offices
• A wider pressure group to start removing halogen bulbs from sale. (After all, they are almost as bad as the old incandescent light bulbs)
• More generally, a much closer look at how Cambridge can benefit from reducing its peak needs to control its electricity bills
Chris Goodall
www.carboncommentary.com
@ChrisGoodall2
+44 7767 386696