\section{SI Units}
\begin{quotation}
{\bf{The watt}}.\index{watt}
This SI unit is named after James Watt.\index{Watt, James}
As for all SI units whose names are derived from the\index{nomenclature}
proper name of a person, the first letter of its symbol is\index{capitalization}
uppercase (W). But when an SI unit is spelled out, it should\index{spelling}
always be written in lowercase (\ind{watt}),
with the exception of the ``degree \ind{Celsius}."
\par
\hfill
from wikipedia
\end{quotation}
\noindent
\ind{SI} stands for Syst\`eme International.
SI units are the ones that all engineers should use,
to avoid losing spacecraft.
\begin{table}[h]
\figuredangle{
\begin{tabular}{cc}
\begin{tabular}{lll} \toprule
\multicolumn{3}{c}{ \SI\ units
}\\ \midrule
energy & one \ind{joule} & 1\,J \\
power & one \ind{watt} & 1\,W \\
force & one \ind{newton} & 1\,N \\% = 1\,J/m \\
length & one \ind{metre} & 1\,m \\
time & one \ind{second} & 1\,s \\
temperature & one kelvin & 1\,K \\
%temperature & one degree Celsius & 1\degreeC \\
\bottomrule
\end{tabular}&
\begin{tabular}{*{10}{c}} \toprule
%% SI-Prefixes
prefix
%& yotta & zetta
& kilo
& mega
& giga
& tera
& peta
& exa
%& %hecto
\\ \midrule
symbol
% & Y & Z
&k&M&G&T&P&E
% E & P & T & G & M & k %& %h &
\\
factor
% & $10^{24}$ & $10^{21}$
& $10^{3}$
& $10^{6}$
& $10^{9}$
& $10^{12}$
& $10^{15}$
& $10^{18}$
%& $10^{2}$ \\ \bottomrule
\\ \bottomrule
\\ \toprule
prefix & centi & milli & micro & nano & pico & femto \\% & atto \\
%& zepto & yocto \\
\midrule
symbol & c & m & $\mu$ & n & p & f \\%& a \\
% & z & y\\
factor & $10^{-2}$ & $10^{-3}$ & $10^{-6}$ & $10^{-9}$ & $10^{-12}$ & $10^{-15}$ %% & $10^{-18}$
% & $10^{-21}$ & $10^{-24 }$
\\ \bottomrule
\end{tabular}
\end{tabular}
}{
\caption[a]{SI units and prefixes}
}
\end{table}
\beginfullpagewidth
\section{My preferred units for energy, power, and transport efficiencies}
\begin{oldcenter}
\begin{tabular}{llll} \toprule
\multicolumn{3}{c}{ My preferred units, expressed in SI
}\\ \midrule
energy & one kilowatt-hour & 1\,kWh & 3\,600\,000\,J \\
power & one kilowatt-hour per day & 1\,kWh/d & (1000/24)\,W $\simeq$ 40\,W \\
force & one kilowatt-hour per 100\,km & 1\,kWh/100\,km & 36\,N \\
time & one hour & 1\,h & $3600$\,s \\
& one day & 1\,d & $24 \times 3600$\,s $\simeq 10^5$\,s \\
& one year & 1\,y & $365.25 \times 24 \times 3600$\,s $\simeq \pi\times10^7$\,s \\
% mass & one ton & 1\,t & 1000\,kg \\
force per mass & kilowatt-hour per ton-kilometre & 1\,kWh/\tkm & 3.6\,m/s$^2$ ($\simeq 0.37g$) \\
\bottomrule
\end{tabular}
\end{oldcenter}
\section{Additional units and symbols}
% In this book I use the following additional \ind{units}:
\begin{oldcenter}
\begin{tabular}{llll} \toprule
Thing measured & \index{units}unit name & symbol & value \\ \midrule
humans & person & p &\\
mass & ton & t & $1\,{\rm{t}} = 1000\,\kg$ \\
&gigaton &Gt & $1\,{\rm{Gt}} = 10^9 \times 1000\,\kg = 1\,{\rm{Pg}}$\index{Pg}\index{petagram} \\
transport & person-kilometre & p-km \\
transport & \tonne-kilometre & t-km \\
volume & litre & l & 1\,l $ = 0.001\,\m^3$ \\
area & square kilometre & sq km, km$^2$ & 1\,sq km $ = 10^6\,\m^2$ \\
& hectare & ha & 1\,ha $ = 10^4\,\m^2$ \\
& Wales & & 1\,Wales $ = 21\,000\,\km^2$ \\
& London (Greater London) & & 1\,London $ = 1580\,\km^2$ \\
% http://en.wikipedia.org/wiki/Greater_London
% & London (up to M25) & & 1\,M25 $ = 2300\,\km^2$ \\
energy & \ind{Dinorwig} & & 1\,Dinorwig = 9\,GWh \\
\bottomrule
\end{tabular}
\end{oldcenter}
\ENDfullpagewidth
% CUTTABLE
% For example, a bus that travels 10\,km with 20 people on board has
% delivered an amount of personal transportation equal to
% 200\,p-km.
% A truck that shifts 10\,tons of stuff a distance of 100\,km
% provides 1000\,t-km of transport.
% END CUTTABLE
% Energy costs
% When I write 1\,km$^2$ I mean 1\,(km)$^2$, not 1000\,m$^2$.
\section{Billions, millions, and other people's prefixes}
Throughout this book ``a billion'' (1\,bn) means a standard
American billion, that is, $10^9$, or a thousand million.
A trillion is $10^{12}$.
The standard prefix meaning ``billion'' ($10^9$) is ``giga.''
% In
% Don't confuse
% Giga, trillion, and billion.
% A billion is a giga- ($10^9$).
In \ind{continental Europe}\index{Europe!continental},
the abbreviations \ind{Mio} and \ind{Mrd}
denote a \ind{million} and \ind{billion} respectively.
Mrd is short for \ind{milliard},
which means $10^9$.
The abbreviation \ind{m} is often used to mean million, but this abbreviation is
incompatible with the SI -- think of mg (milligram) for example.
So I don't use m to mean million. Where some people use m,
I replace it by M\@. For example, I use \ind{Mtoe}\index{toe} for million \tonnes\ of oil equivalent,
and \ind{Mt}\,\COO\ for million \tonnes\ of \COO\@.
% The abbreviation \ind{bn} is often used to mean billion.
% I prefer \ind{b}.
% But perhaps I should stick to \ind{bn}.
\section{Annoying units}
There's a whole bunch of commonly used units that are annoying
for various reasons. I've figured out what some of them mean.
I list them here, to help you translate the media stories you read.
% \beforeqa
\qa{Homes}{
\noindent
The ``\ind{home}''\label{pHOME}
is commonly used when
describing the power of renewable facilities.
%the one of the most common units used to describe the power of a new
%\windfarm.
For example,
%% http://news.bbc.co.uk/1/hi/scotland/glasgow_and_west/6031995.stm
``The \pounds300\,million
Whitelee \windfarm's 140 turbines will generate
322\,MW -- enough to power 200\,000 homes.''
%I think that a `home' is about 0.6\,kW, or 14\,kWh per day.
%This guess is consistent with the above quote, assuming that
%the turbines will actually generate about 35\% of 322\,MW.
%% http://www.eon-uk.com/images/Buildingasustainablefuture.pdf
The ``home'' is defined by
%E-ON and
the British Wind Energy Association to be a power of
%4700\,kWh/y, or 13\,kWh/d.
% However, says a home is
\Red{4700\,kWh per year}
% household
[\myurlb{www.bwea.com/ukwed/operational.asp}{http://www.bwea.com/ukwed/operational.asp}].
That's 0.54\,kW, or \Red{13\,kWh per day}.
%% 12.87\,kWh/d
%% they assume 860g CO2/kWh for coal displacement.
(A few other organizations use 4000\,kWh/y per household.)
% That means one ``home'' uses 0.46\,kW or \Red{11\,kWh/d}.)
The ``home'' annoys me because I worry that people
confuse it with {\em the total power consumption of
% 2.5 people,
the occupants of a home} -- but the latter is actually about
% 125 * 2.5 / 13 = 24
24 times bigger.
The ``home'' covers the average domestic {\em{electricity}\/}
consumption of a household, only.
Not the household's home heating. Nor their workplace. Nor their transport.
Nor all the energy-consuming things that society does for them.
% If I announced a new renewable source that would
%provide enough power for ``all the homes in Britain,''
%I bet people would think that all Britain's power was covered.
%But using the standard exchange rates, the amount of power would be
%just 14\,GW, which is only one third of current electricity consumption,
%and only one twentieth of the total power consumption of the UK.
% CUTTABLE ***
Incidentally, when they talk of the \COO\ emissions of a ``home,''
the official exchange rate appears to be 4 \tonnes\ \COO\ per home per year.
% and 770\,g\,\COO\ per kWh.
% CHECK?
}
% 1TWh/y - enough to power more than 200,000 homes
%% http://news.bbc.co.uk/1/hi/sci/tech/4620350.stm
%% CUTTABLE ***
\qa{Power stations}{
\noindent
Energy saving ideas are sometimes described
in terms of \ind{power station}s.
For example according to a BBC report on putting
new everlasting LED lightbulbs in traffic lights,
``The power savings would be huge --
keeping the UK's traffic lights running requires the equivalent of
two medium-sized power stations.''
\myurlb{news.bbc.co.uk/1/low/sci/tech/specials/sheffield_99/449368.stm}{http://news.bbc.co.uk/1/low/sci/tech/specials/sheffield_99/449368.stm}
% `Replacing 50 per cent of the lighting in the UK with
% Gallium Nitride light-emitting diodes
% would save the energy produced by
% five medium-sized power stations' (Cambridge University press release,
% 2 June 2003).
\marginfig{
\noindent%
\mbox{\epsfxsize=50mm\epsfbox{../data/coalC.eps}} \\[-2.5mm]
\begin{center}
{\small{\sf Power (MW)}}\\
\end{center}
\caption[a]{
Powers\index{power station!coal}\index{Drax}\index{Eggborough}
of Britain's coal power stations.\index{coal power station}
%% of this 30GW, 20.6GW is ``opted in'' as of 2007. 8.7 is opted out.
I've highlighted in blue 8\,GW of generating capacity that will close by 2015.
% 3.4\,GW of nuclear power will also close by 2015, and
% source http://www.publications.parliament.uk/pa/cm200506/cmselect/cmenvaud/584/584we48.htm
% date 21 sept 2005
% another 5.8\,GW by 2019.
2500\,MW, shared across Britain,
is the same as 1\,kWh per day per person.
} \label{fig.coalC}
}
What is a medium-sized power station? 10\,MW? 50\,MW? 100\,MW? 500\,MW?
I don't have a clue. A google search indicates that
some people think it's 30\,MW, some 250\,MW, some
500\,MW (the most common choice),
and some 800\,MW\@. What a useless unit!
%% http://www.cabinetoffice.gov.uk/strategy/downloads/work_areas/energy/submissions/OxfordTrust.pdf
%% http://archive.nics.gov.uk/eti/000623c-eti.htm
%% http://www.iop.org/EJ/article/1402-4896/1999/T80B/038/physscr9_T80B_038.pdf
%% http://nucnews.net/nucnews/2002nn/0203nn/020312nn.htm
%% http://forum.cygnus-study.com/archive/index.php/t-534.html
%% http://www.iop.org/Jet/fulltext/JETR99013.pdf
%% ``1 million tonnes of C02 emissions within one year. This is equivalent to the pollution belched out by one medium-sized power station.''
%% http://www.prnewswire.co.uk/cgi/news/release?id=185285 (which means 200MW)
% I feel that there might be a case for making `a big power station'
% a standard power unit -- equal to one gigawatt, say. Many nuclear power
% stations put out one gigawatt. But I think
% `Medium power stations' are an
% especially useless unit, since
% Nobody knows
% how many medium power stations our country's power consumption
% corresponds to.
Surely it would be clearer for the article
about traffic lights to express what it's saying as a percentage?
``Keeping the UK's traffic lights running requires 11\,MW of electricity,
which is 0.03\% of the UK's electricity.''
This would reveal how ``huge'' the power savings are.
% The only problem with expressing traffic lights in such precise terms
% instead of hiding them behind the fuzzy veil of ``medium-sized power stations''
% is that the resulting statement would not sound like
% ``huge'' power savings any more!
%% data/coalpowerstns
Figure \ref{fig.coalC} shows the powers of the UK's 19 coal power stations.
% \myurl{http://www.ukqaa.org.uk/PowerStation.html}
}
\qa{\ind{Cars taken off the road}
}{
\noindent
Some advertisements describe
reductions in \COO\ pollution
in terms of the ``equivalent number of cars taken off the road.''
For example, Richard Branson says that if Virgin Trains' Voyager fleet
switched to 20\% biodiesel -- incidentally, don't you feel it's outrageous
to call
% Fri 8/6/07
a train a ``green bio\-die\-sel-powered train'' when it runs on 80\% fossil fuels and
just 20\% biodiesel? --
% and that they call a product ``biodiesel'' even though is only 20\% biodiesel?
sorry, I got distracted.
Richard Branson says that {\em{if}\/} Virgin Trains' Voyager fleet
switched to 20\% biodiesel -- I emphasize the ``{\em{if}}'' because people like Beardie
% and BP
are always getting media publicity for announcing that they are {\em{thinking of}\/} doing
good things, but some of these
fanfared initiatives are later quietly cancelled,
such as the idea of towing aircraft around airports to make them greener --
% http://www.virgin.com/News/Articles/VirginAtlantic/2006/04122006.aspx
% http://www.timesonline.co.uk/tol/news/environment/article3516551.ece
sorry, I got distracted again.
Richard Branson says that {\em{if}\/} \ind{Virgin Trains}' Voyager fleet
switched to 20\% biodiesel,
then there would be a reduction of 34\,500 \tonnes\
of \COO\ per year, which is equivalent
to ``23\,000 cars taken off the road.''
% incidentally they say that B20 biodiesel cuts coo by UP TO 14%
This statement reveals the exchange
rate:
\begin{center}
``one car taken off the road'' $\longleftrightarrow$ $-1.5$\,\tonnes\ per year of \COO\@.
\end{center}
}
\qa{Calories
}{
\noindent
The calorie is annoying because the diet community call a \ind{kilocalorie}\index{kcal}
a \ind{Calorie}\index{calorie}.
1 such food Calorie = 1000 calories.% = 4200\,J\@.
$2500\,\kCal = 3\, \kWh = 10\,000\,\kJ = 10\,\MJ.$
}
\qa{Barrels
}{
\noindent
An annoying unit loved by the oil community, along with
the \tonne\ of oil.
% Barrels are annoying because
Why can't they stick to one unit?
A barrel of oil is 6.1\,GJ or 1700\,kWh.
Barrels are doubly annoying because there are multiple definitions
of barrels, all having different volumes.
Here's everything you need to know about barrels of oil.
One barrel is 42 U.S.\ gallons, or
159 litres.
One barrel of oil is
0.1364 \tonnes\ of oil.
One barrel of crude oil has an energy of 5.75\,GJ\@.
One barrel of oil weighs 136\,kg.
One \tonne\ of crude oil is 7.33 barrels
% this is consistent with 0.1364
and 42.1\,GJ\@.
% Sat 15/12/07 alternate view:
% ORNL \tinyurl{2hcgdh}{http://cta.ornl.gov/data/appendix_b.shtml} say
% 1G barrel is 6119 PJ k M G T P
% 1 barrel is 6119 MJ
The carbon-pollution rate of crude oil is
400\,kg of \COO\ per barrel.
\myurlb{www.chemlink.com.au/conversions.htm}{http://www.chemlink.com.au/conversions.htm}
This means that when the price of oil is \$100 per barrel,
oil energy costs 6\cents\ per kWh.
% This means that when the price of oil is \$90 per barrel,
% people are paying \cents5.4 per kWh,
% and they are paying \$225 per ton of \COO\ emitted.
If there were a \ind{carbon tax} of \$250 per ton of \COO\ on fossil fuels,
that tax would increase the price of a \ind{barrel of oil} by \$100.
}
\qa{Gallons
}{
\noindent
The \ind{gallon} would be a fine human-friendly unit, except the Yanks
% Americans
messed it up by defining the gallon differently from
everyone else, as they did the \ind{pint} and the \ind{quart}.
The US\ volumes are all roughly
five-sixths of the correct \ind{volume}s.
1\,US gal = 3.785\,l = 0.83\,imperial gal.
1\,imperial gal = 4.545\,l.
}
\qa{Tons}{
\noindent
Tons\index{ton} are annoying because there are short \tonnes, long \tons\ and metric \tonnes.
They are close enough that I don't bother distinguishing between them.
1 short ton (2000\,lb) = 907\,kg;
% 1 short ton (2000\,lb) = 907.2\,kg; 2.2047 lb per kg
1 long ton (2240\,lb) = 1016\,kg;
1 metric ton (or \ind{tonne}) = 1000\,kg.
}
\qa{\ind{BTU} and \ind{quad}s}{
\noindent
British thermal units are annoying
because they are neither part of the {\em{Syst\`eme Internationale}},
nor are they of a useful size. Like the useless joule, they are too small,
so you have to roll out silly prefixes
like ``quadrillion'' ($10^{15}$) to make practical use of them.
1\,kJ is 0.947\,BTU\@.
1\,kWh is 3409\,BTU\@.
A ``quad'' is 1 quadrillion BTU = 293\,TWh.
% and it is almost exactly 1EJ
% terawatt-hours.
}
\section{Funny units}
\beforeqa
\qa{Cups of tea}{
\noindent
\index{cup of tea}Is this a way to make solar panels sound good?\index{cup of tea}
``Once all the 7\,000 photovoltaic panels
are in place, it is expected that the solar panels will create 180\,000
units of renewable electricity each year -- enough energy
to make {\bf nine million cups of tea}.''
This announcement thus equates 1\,kWh to 50 cups of tea.
As a unit of volume,
1 US \ind{cup} (half a US \ind{pint}) is officially 0.24\,l;\index{litre}\index{volume!units}
but a cup of \ind{tea} or \ind{coffee} is usually about 0.18\,l.
% an imperial cup (half an imperial pint) =
% I confirm that to
To raise
50 cups of water, at 0.18\,l per cup, from
15\degreesC\ to 100\degreesC\ requires 1\,kWh.
So ``nine million cups of tea per year'' is another way of saying ``20\,kW.''
}
\qa{Double-decker buses, Albert Halls and Wembley stadiums}{
\noindent
``If everyone in the UK that could, installed cavity wall insulation,
we could cut carbon dioxide emissions by a huge 7 million
\tonnes. That's enough carbon dioxide to fill nearly 40 million
double-decker buses or fill the new Wembley stadium 900 times!''
% http://www.energysavingtrust.org.uk/resources/useful_statistics
From which we learn the helpful fact that
one \ind{Wembley} is 44\,000 \ind{double decker bus}es.
% The bowl volume of wembley is 1\,139\,100 m^3
% http://www.wembleystadium.com/brilliantfuture/learningResources/
% Wembley Stadium has approximately 180,000sq metres of internal floor space
% Area of roof: Metal Roof = 40,000 m2, Single Ply Roof = 12,000 m2
% Pitch dimension and technology Including run off area:10,096m2
Actually, Wembley's bowl has a volume of 1\,140\,000\,m$^3$.
%\subsubsection{Albert Halls}
%% http://www.greenenergy.uk.com/site/environment/Energy%20Conservation.aspx
%If everyone in the UK installed just one energy saving light bulb, the
%savings in \COO\ emissions would fill London's Royal Albert Hall
%nearly 3,000 times.
``If every household installed just one energy saving light bulb,
% the
% electricity saved in a year could power the Blackpool Illuminations
% for nearly 900 years and
there would be enough carbon dioxide saved
to fill the \ind{Royal Albert Hall} 1,980 times!''\index{Albert Hall}
(An Albert Hall is 100\,000\,m$^3$.)
% As I pointed out on \pref{photairvolume},
Expressing amounts of \COO\ by volume
rather than mass is a great way to make them sound big.
Should ``1\,kg of \COO\ per day'' sound too small,
just say ``200\,000 litres of \COO\ per year''!
\margintab{
\begin{tabular}{r@{\ $\leftrightarrow$\ }c}\toprule
% \multicolumn{2}{c}{\sc{ }} \\
mass of \COO & volume \\ \midrule
2\,kg \COO & 1\,m$^3$ \\
1\,kg \COO & 500\,litres \\
44\,g \COO & 22\,litres \\
2\,g \COO & 1\,litre \\
\bottomrule
\end{tabular}
\caption[a]{
Volume-to-mass conversion.
% every 44\,g of \COO\ occupies 22\,litres.
}
}
}
%\section{Volumes and areas}
\section{More volumes}
% 1 US gallon = 3.785 litres. 1 imperial \ind{gallon} = 4.546 litres.
A \ind{container} is 2.4\,m wide by 2.6\,m high by (6.1 or 12.2) metres long
\marginfig{
\begin{center}
\begin{tabular}{@{}c@{}}
{\mbox{\epsfxsize=53mm\epsfbox{../../images/TEU.eps}}}
\\
\end{tabular}
\end{center}
\caption[a]{A twenty-foot container \par
(1 TEU).
}\label{TEU}
}%
(for the \ind{TEU} and \ind{FEU} respectively).
% Can take 24\,000\,kg.
% exterior vol seems to be 38mmm
One \ind{TEU}\index{volume} is the size of a small 20-foot
\ind{container} -- an interior volume of about 33\,m$^3$. Most
containers you see today are 40-foot
containers with a size of 2\,TEU\@.
A 40-foot container weighs 4\,tons and can carry
26\,tons of stuff; its volume is 67.5\,m$^3$.
% Container ship freight is roughly 2.4 billion kg per y.
% Prices start at \$500 per container, which works out
% to \$0.02 per kg.
A \ind{swimming pool} has a volume of about 3000\,m$^3$.
% 50 25 2.5 is 3125
% An Albert Hall has a volume of roughly 100\,000 cubic metres.
% one \ind{Wembley} is 44\,000 \ind{double decker bus}es.
One \ind{double decker bus} has a volume of 100\,m$^3$.
One hot air \ind{balloon}\index{hot air balloon} is 2500\,m$^3$.
% BP say 1 hot air balloon = 4 tonnes of CO2
The great \ind{pyramid} at \ind{Giza}\index{great pyramid}
has a volume of
2\,500\,000 cubic metres.
\section{Areas}
The \ind{area} of the earth's surface\index{earth!area} is
\margintab{
\begin{tabular}{cl} \toprule
hectare &$= 10^4\, \m^2$ \\%&$= 10^{-2}\, \km^2$\\
acre &$= 4050\, \m^2$ \\%&$= 0.004\, \km^2$\\
square mile % &$= 2.6\times 10^{6}\, \m^2$
&$= 2.6\, \km^2$\\
square foot &$= 0.093\,\m^2$ \\%&$= 9.3\times 10^{-8}\, \km^2$\\
square yard &$= 0.84\,\m^2$ \\%&$= 8.4\times 10^{-7}\, \km^2$\\
\bottomrule
\end{tabular}
% }{
\caption[a]{Areas.
% The population density of England is
% 380 people per km$^2$, or 2630\,m$^2$ per person.
}
\label{tab.area}
}% }\end{table}
$500\times 10^{6}\,\km^2$;
the land area is
$150\times 10^{6}\,\km^2$.
A typical soccer field has an area of 8000\,m$^2$.
An American Football field has an area of 5350\,m$^2$.
% In the UEFA Champions League a football field must be exactly 105x68m, which is an area of 7,140 m². An American Football field, including both end zones, is 360 ft by 160 ft, or 57,600 square-feet (5,351.2 m²).
My typical British 3-bedroom house has a floor area of 88\,m$^2$.
In the USA,
% in the last 25 years, the average size of a single-family house
% has increased from 1740 square feet (162\,m$^2$) to 2330 square feet (216\,m$^2$).
the average size of a single-family house
is 2330 square feet (216\,m$^2$).
%we should include a {\dem\ind{sunniness factor}\/}
% of $1/3$}}.%
\begin{table}[btp]
\figuremargin{
\begin{center}
\begin{tabular}{lrl} \toprule
Land use & area per person & percentage \\
& \multicolumn{1}{r}{(m$^2$)} & \\
\midrule
-- domestic buildings & 30\phantom{.6} & \phantom{8}1.1 \\
-- domestic gardens & 114\phantom{.6} & \phantom{8}4.3 \\
-- other buildings & 18\phantom{.6} & \phantom{8}0.66 \\
-- roads & 60\phantom{.6} & \phantom{8}2.2 \\
-- railways & 3.6 & \phantom{8}0.13 \\
-- paths & 2.9 & \phantom{8}0.11 \\
-- greenspace & 2335\phantom{.6} & 87.5 \\
-- water & 69\phantom{.6} & \phantom{8}2.6 \\
-- other land uses & 37\phantom{.6} & \phantom{8}1.4 \\
\midrule
Total & 2670\phantom{.6} & 100 \\
\bottomrule
%% cf agricultural area per person in the UK is 2800
%% IDEA - remove the percentages, add link to that figure.
\end{tabular}
\end{center}
}{
\caption[a]{Land areas, in England, devoted to different uses.
Source:
Generalized Land Use Database Statistics for England 2005.
\protect\tinyurl{3b7zdf}{http://www.communities.gov.uk/publications/planningandbuilding/generalizedlanduse}
}
\label{tabLandAreas}% referred to in notes of solarnotes.tex
}
\end{table}