‘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

50

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

chris@carboncommentary.com

@ChrisGoodall2

+44 7767 386696