-
Notifications
You must be signed in to change notification settings - Fork 2
/
short.html
128 lines (122 loc) · 5.2 KB
/
short.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
<html>
<title>A little knowledge</title>
<style>
body {
margin: 5%;
}
a.footnote {
vertical-align: super;
font-size: 50%;
}
a.footnote:before {
content: "[";
}
a.footnote:after {
content: "]";
}
h3 {
display: inline;
font-size: 100%;
}
span.source {
font-size: 50%;
color: #ccc;
}
div.note, div.note a {
color: #999;
}
div#citation {
margin-top: 50px;
}
</style>
<body>
<h1>A little knowledge</h1>
<p>In my daily life at DECC, I find it useful to bear these facts in mind.</p>
<h2>Four facts</h2>
<ol>
<li>Energy is more than just electricity: Less than a fifth of the energy we
consume is electricity.
<div class='note'>
Source:
<a href='https://www.gov.uk/government/publications/digest-of-united-kingdom-energy-statistics-dukes-2012-printed-version-excluding-cover-pages'>Dukes
2012</a>
Chart 1.5: UK 2011 final energy consumption by fuel, electricity is 18.5%.</div>
</li>
<li>The UK uses about 2500 TWh of energy per year.
<div class='note'>
Source:
<a href='https://www.gov.uk/government/publications/digest-of-united-kingdom-energy-statistics-dukes-2012-printed-version-excluding-cover-pages'>Dukes
2012</a>
Table 1.1: UK 2011 total primary demand. Exact figure is 2469 TWh.</div>
</li>
<li>The maximum rate at which energy is used by the UK is about 400 GW,
the minimum rate is about 100 GW.
<div class='note'> This is pretty
approximate. See <a href='http://decc.github.io/numbers-for-decc/HighLowDemandWorkings.xlsx'>spreadsheet
of workings</a>.</div>
</li>
<li>The UK spends £130 billion on energy each year.
<div class='note'>
Source:
<a href='https://www.gov.uk/government/publications/digest-of-united-kingdom-energy-statistics-dukes-2012-printed-version-excluding-cover-pages'>Dukes
2012</a>
paragraph 1.22: UK 2011 £134 billion spend on energy by final
consumers; does not include spend on energy using equipment like cars,
boilers or kettles.</div>
</li>
</ol>
<h2>Four conversions</h2>
<ol>
<li>A TWh (terawatt-hour) is a billion kWh (kilowatt-hours). A kWh is the unit
on my electricity bill.
<div class='note'>In general: T means tera- which means trillion; G means
giga- which means billion; M means mega- which means million; k means kilo-
which means thousand.</div>
</li>
<li>A GW (gigawatt) is a million kW (kilowatts). A kW is the rate at which my small fan heater produces heat.</li>
<li>A GW (gigawatt) of power, running non-stop for an hour, produces a GWh
(gigawatt-hour) of energy. Running non-stop for a year, it would produce
just under 10 TWh (terawatt-hours) of energy.
<div class='note'>If a
1 kW solar panel ran flat out, non-stop, all year it would produce 1 kW
× 24 hours × 365 days = 8760 kWh of electricty. It doesn't
run non-stop, nor flat out. Darkness and clounds mean that, on average, it
runs for 10% of the time, so it produces 1 kW × 24 hours ×
365 days × 10% = 876 kWh of electricty. Almost nothing runs
flat-out, non-stop, all year.</div>
</li>
<li>A billion pounds is £16 for each man, woman and child in the UK.
<div class='note'>Exact figure:
£15.82/person. Source: <a href='http://www.ons.gov.uk/ons/rel/census/2011-census/population-and-household-estimates-for-the-united-kingdom/index.html'>Office
for National Statistics UK census night 2011 population estimate</a> of 63.2
million.</div>
</li>
</ol>
<h2>Units</h2>
<div>There are surprisingly many commonly-used units for energy. </div>
<div class='note'>You may see: kilowatt-hours (kWh), tonnes of oil equivalent
(toe), tonnes of coal equivalent (tce), therms, British Thermal Units (BTUs),
and joules (J). All of these may occur with the usual prefixes, eg, Mtoe
(million tonnes of oil equivalent), or PJ (petajoules).</div>
<h3>Hint:</h3> If you given told a number in units other than TWh (or kWh) ask
for it to be converted. Wait until the conversion is done: otherwise the number
will be meaningless to you.
<h2>A caution</h2>
<div>I don't trust claims that something is better because it is more efficient
— I need to understand exactly what is going on to be sure.
<div class='note'>For instance: The same device can be claimed to be more or
less efficient depending on whether its efficiency is 'gross' or 'net'. Even
though turning natural gas into heat is almost 100% efficient, while turning
gas into electricity is only 60% efficient, turning gas into electricity
isn't always wasteful; perpetual motion machines are impossible, but it is
possible to say a machine is more than 100% efficient.</div>
</div>
<div id='citation'>This is version 0.3 updated on 19 June 2013 by Thomas
Counsell and James Geddes
(<a href='mailto:[email protected]'>[email protected]</a>). The
latest version is available
from <a href="http://decc.github.io/numbers-for-decc/short.html">http://decc.github.io/numbers-for-decc/short.html</a>. If
you want to report bugs or propose fixes, you can do so
at <a href='http://github.com/decc/numbers-for-decc'>http://github.com/decc/numbers-for-decc</a></div>
</body>
</html>