A reality check on renewables David MacKay

when the Industrial Revolution started

the amount of carbon sitting underneath

Britain in the form of coal was as big

as the amount of carbon sitting under

Saudi Arabia in the form of oil and this

carbon powered the Industrial Revolution

it put the great in Great Britain and

led to Britain’s temporary world

domination and then in 1918 coal

production in Britain peaked and has

declined ever since

in due course Britain started using oil

and gas from the North Sea and in the

year 2000 oil and gas production from

the North Sea also peaked and they’re

now on the on the decline these

observations about the finiteness of

easily accessible local secure fossil

fuels this is a motivation for saying

well what’s next what is life after

fossil fuels going to be like shouldn’t

we be thinking hard about how to get off

fossil fuels another motivation of

course is climate change and when people

talk about life after fossil fuels and

climate change action I think there’s a

lot of fluff a lot of green wash a lot

of misleading advertising and I feel a

duty as a physicist to try to guide

people round the claptrap and help

people understand the actions that

really make a difference and to focus on

ideas that do add up let me illustrate

this with what physicists call back of

envelope calculation we love back of

envelope calculations you ask a question

you write down some numbers and you get

yourself an answer it may not be very

accurate but it may make you say hmm so

here’s a question imagine if we said oh

yes we can get off fossil fuels we’ll

use biofuels problem-solve transport we

don’t need oil anymore

well what if we grew the biofuels for a

road on the grass verge at the edge of

the road how wide would the verge have

to be for that to work out okay so let’s

put in some numbers let’s have our cars

go at 60 miles per hour let’s say they

do 30

per gallon that’s the European average

for new cars let’s say the productivity

of biofuel plantations is 1200 litres of

biofuel per hectare per year that’s true

of European biofuels and let’s imagine

the cars are spaced 80 metres apart from

each other and they’re just perpetually

going along this road the length of the

road doesn’t matter because the longer

the road the more biofuel plantation

we’ve got what do we do with these

numbers well you take the first number

and you divide by the other three and

you get eight kilometers and that’s the

answer that’s how wide the plantation

would have to be given these assumptions

and maybe that makes you say hmm maybe

this isn’t going to be quite so easy

and it might make you think perhaps is

an issue to do with areas and in this

talk I’d like to talk about land areas

and ask is there an issue about areas

the answer is going to be yes but it

depends which country you are in so

let’s start in the United Kingdom since

that’s where we are today the energy

consumption of the United Kingdom the

total energy consumption not just

transport but everything I like to

quantify it in light bulbs it’s as if

we’ve all got 125 light bulbs on all the

time 125 kilowatt hours per day per

person is the energy consumption of the

UK so there’s 40 light bulbs worth the

transport 40 light bulbs worth for

heating and 40 light bulbs worth for

making electricity and other things are

relatively small compared to those three

big fish it’s actually got a bigger

footprint if we take into account the

embodied energy and the stuff we import

into our country as well and ninety

percent of this energy today still comes

from fossil fuels and ten percent only

from others greener possibly goona

sources like nuclear power and

renewables so that’s the UK and the

population density of the UK is 250

people per square kilometer and I’m now

going to show you other countries by

these same two measures on the vertical

axis I’m going to show you how much

light bulbs what our energy consumption

per person is and we’re at 125

lightbulbs per person and that little

blue dot there is showing you the land

air

year of the United Kingdom and the

population density is on the horizontal

axis and we’re 250 people per square

kilometer let’s add European countries

in blue and you can see there’s quite a

variety I should emphasize both of these

axes are logarithmic as you go from one

gray bar to the next great bar you’re

going up a factor of 10 next let’s add

Asia in red Middle Eastern North Africa

in green sub-saharan Africa in blue

black is South America

purple is Central America and then in

pukey yellow we have North America

Australia and New Zealand and you can

see the great diversity of population

densities and of per capita consumptions

countries are different from each other

top left we have Canada and Australia

with enormous land areas very high per

capita consumption 200 or 300 light

bulbs per person and very low population

densities top right Bahrain has the same

energy consumption per person roughly as

Canada over 300 light bulbs per person

but their population density is a factor

of three hundred times greater a

thousand people per square kilometer

bottom right Bangladesh has the same

population density as Bahrain but

consumes a hundred times less per person

bottom left well there’s no one but

there used to be a whole load of people

here’s another message from this diagram

I’ve added on little blue tails behind

Sudan Libya China India Bangladesh

that’s 15 years of progress where were

they 15 years ago and where are they now

and the message is most countries are

going to the right and they’re going up

up and to the right bigger population

density and higher per capita

consumption so we may be off in the top

right hand corner slightly unusual the

United Kingdom accompanied by Germany

Japan South Korea the Netherlands and a

bunch of other slightly odd countries

but many other countries are coming up

and to the right to come and join us so

we’re a picture if you like of what the

future energy consumption might be

looking like in other countries - and

I’ve also added in this diagram now some

pink lines that go

down and to the right those are lines of

equal power consumption per unit area

which I measure in watts per square

meter so for example the middle line

there 0.1 watts per square meter is the

energy consumption per unit area of

Saudi Arabia Norway Mexico in purple and

Bangladesh 15 years ago and half of the

world’s population lives in countries

that are already above that line the

United Kingdom is consuming 1.25 watts

per square meter shows Germany and Japan

is consuming a bit more

so let’s now say why this is relevant

why is it relevant well we can measure

renewables in the same units and other

forms of power production in the same

units and renewables is one of the

leading ideas for how we could get off

our 90% fossil fuel habit so here comes

from renewables energy crops deliver

harper watt per square meter in european

climates what does that mean and you

might have anticipated that that result

given what I told you about the biofuel

plantation a moment ago

well we consume 1.25 watts per square

meter what this means is even if you

covered the whole of the United Kingdom

with energy crops you couldn’t match

today’s energy consumption wind power

produces a bit more 2.5 watts per square

meter

but that’s only twice as big as 1.25

what’s the square meter so that means if

you wanted literally to produce a total

energy consumption in all forms on

average from wind farms you’d need wind

farms half the area of the UK I’ve got

data back to back up all these

assertions by the way next let’s look at

solar power solar panels when you put

them on a roof deliver about 20 watts

per square meter in England if you

really want to get a lot from solar

panels you need to adopt adopt the

traditional Bavarian farming method

where you leap off the roof and coat the

countryside with solar panels to solar

parks because of the gaps between the

panel’s deliver less they deliver about

5 watts per square meter of land area

and here’s a solar Park in Vermont with

real data delivering 4.2

watts per square meter remember where we

are 1.25 watts per square meter wind

farms 2.5 solar park about five so

whatever whichever of those renewables

you pick the message is whatever mix of

those renewables you’re using if you

want to power the UK on them you’re

going to need to cover something like 20

percent or 25 percent of the country

with those renewables and I’m not saying

that’s a bad idea we just need to

understand the numbers I’m absolutely

not Antti renewables I love renewables

but I’m also Pro arithmetic

concentrating solar power in deserts

delivers larger powers per unit area

because you don’t have the problem of

clouds and so this facility delivers 14

watts per square meter

this 110 watts per square meter and this

one in Spain five watts per square meter

being generous to concentrating solar

power I think it’s probably credible it

could deliver 20 watts per square meter

so that’s that’s nice of course Britain

doesn’t have any deserts yet so here’s a

summary so far all renewables much as I

love them are diffused they all have a

small power per unit area and we have to

live with that fact and that means if

you do want renewables to make a

substantial difference for a country

like the United Kingdom on the scale of

today’s consumption you need to be

imagining renewable facilities that are

country sized not the entire country but

a fraction of the country says a

substantial fraction there are other

options for generating power as well

which don’t involve fossil fuels so

there’s nuclear power and on this

Ordnance Survey map you can see there’s

a size well be inside a blue square

kilometer that’s one gigawatt in a

square kilometer which works out to a

thousand watts per square meter

so by this particular metric nuclear

power isn’t as intrusive as renewables

of course other metrics matter to a

nuclear power has all sorts of

popularity problems but the same goes

for renewables as well here’s a

photograph of a consultation exercise in

full-swing in the little town of

Pennycook just south

just outside Edinburgh and you can see

the children Penacook celebrating the

burning of the effigy of the wind wind

so people are anti everything and we’ve

got to keep all the options on the table

what can a country like the UK do on the

supply side well the options are I’d say

these three are renewables and

recognising that they need to be close

to country size other people’s

renewables so we could go back and talk

very politely to the people in the top

left-hand side of the diagram and say we

don’t want renewables in our backyard

but please could we put min yours

instead and that’s a serious option it’s

a way for the world to to handle this

issue so countries like Australia Russia

Libya Kazakhstan could be our best

friends for renewable production and a

third option is is nuclear power so

that’s some supply-side options in

addition to the supply levers that we

can push and remember we need large

amounts because at the moment we’ll get

90 percent of our energy from fossil

fuels in addition to those levers we

could talk about other ways of solving

this issue namely we could use demand

and that means reducing population I’m

not sure how to do that

all reducing per capita consumption so

let’s talk about three more big levers

that could really help on the

consumption side first transport here

are the physics principles that tell you

how to reduce the energy consumption of

transport and people often say oh yes

technology can answer everything we can

make vehicles that are a hundred times

more efficient and that’s almost true

let me show you the energy consumption

of this typical tank here is 80 kilowatt

hours per hundred person kilometers that

that’s the average European car eighty

kilowatt hours can we make something a

hundred times better by applying those

physics principles I just listed yes

here it is is the bicycle it’s 80 times

better in energy consumption it is

and there are other options in between

because maybe the lady in the tank would

say no no that’s a lifestyle change

don’t change my lifestyle please so well

we could persuade her to get into a

train and that’s still a lot more

efficient than a car but that might be

lifestyle change or there’s the eco car

top left it comfortably accommodates one

teenager and it’s shorter than a traffic

cone and it’s almost as efficient as a

bicycle as long as you drive it at 15

miles per hour in between perhaps a more

realistic options on this lever

transport lever are electric vehicles so

electric bikes and electric cars in the

middle perhaps four times as energy

efficient as the standard petrol powered

tank next is the heating lever heating

is a third of our energy consumption in

Britain and quite a lot of that is going

into homes and upper buildings doing

space heating and water heating so

here’s a typical crappy British house

it’s my house with the Ferrari out front

what can we do to it well the laws of

physics are written up there which

describe what how the power the power

consumption for heating is driven by the

things you can control the things you

can you can control the temperature

difference between the inside and the

outside and there’s this remarkable

technology called the thermostat you

grasp it you rotate it to the left and

your energy consumption in the home will

decrease I’ve tried it it works some

people call it a lifestyle change you

can also get the fluff men in to reduce

the leakiness of your building put fluff

in the walls fluff in the roof and a new

front door and so forth and the sad

truth is this will save you money that’s

not sad that’s good but the sad truth is

it’ll only get about 25 percent off the

leakiness of your building if you do

these things which are good ideas if you

really want to get a bit closer to

swedish building standards with a crappy

house like this you need to be putting

external insulation on the building as

shown by this block of plants in london

you can also deliver heat more

efficiently using heat pumps which use a

smaller bit of high-grade energy like

electricity to move heat from your

garden into your house the third demand

side option I want to talk about the

third way to reduce energy consumption

is read young meters and people talk a

lot about smart meters but you can do

yourself use your own eyes and be smart

read your meter and if you’re anything

like me it’ll change your life here’s a

graph I made I was writing a book about

sustainable energy and a friend asked me

well how much energy do you use at home

and I was embarrassed I didn’t actually

know and so I started reading the meter

every week and the old meter readings

are shown in the top half of the graph

and then 2007 is shown in green at the

bottom and that was when I was reading

the meter every week and my life changed

because I’d started doing experiments

and seeing what made a difference and my

gas consumption plummeted because I

started tinkering with the thermostat

and the timing on the heating system and

I knocked more than a half off my gas

bills there’s a similar story for my

electricity consumption where switching

off the DVD players the stereos the

computer peripherals that were on all

the time and just switching them on when

I needed them knocked another third off

my electricity bills

so we need a plan that adds up and

I’ve described for you six big levers

and we need big action because we get

90% of our energy from fossil fuels and

so you need to push hard on most if not

all of these levers and most of these

levers have popularity problems and if

there is a lever you don’t like the the

use of well please do bear in mind that

means you need even stronger effort on

the other levers so I’m a strong

advocate advocate of having grown-up

conversations that are based on numbers

and facts and I want to close with this

map that just visualizes for you the

requirement of land and so forth in

order to get just 16 light poles per

person from four of the big possible

sources so if you wanted to get sixteen

light poles remember today our total

energy consumption is 125 lightbulbs

worth if you wanted sixteen from wind

this map visualizes a solution for the

UK it’s got 160 wind farms each one

hundred square kilometres in size and

that would be a 20-fold increase over

today’s amount of wind nuclear power to

get 16 lightbulbs per person you’d need

2 gigawatts at each of the purple dots

on the map that’s a four-fold increase

over today’s levels of nuclear power

biomass to get 16 lightbulbs per person

you need a land area

something like three and a half whales

is worth either in our country or in

someone else’s country possibly Ireland

possibly somewhere else

and the fourth supply-side option

concentrating solar power in other

people’s deserts if you wanted to get

sixteen lightbulbs worth then we’re

talking about these eight hexagons down

at the bottom right the total area of

those hexagons is to Greater London’s

worth of someone else’s Sahara and

you’ll need power lines all the way

across Spain and France to being to

bring the power from the Sahara to sorry

we need a plan that adds up we need to

stop shouting and start talking and if

we can have a grown-up conversation make

a plan that adds up and get building

maybe this low-carbon revolution will

actually be fun thank you very much for

listening