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
powered by biofuel by Weetabix
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