A little knowledge
In my daily life at DECC, I find it useful to bear these facts in mind.
Four facts
- Energy is more than just electricity: Less than a fifth of the energy we
consume is electricity.
Source:
Dukes
2012
Chart 1.5: UK 2011 final energy consumption by fuel, electricity is 18.5%.
- The UK uses about 2500 TWh of energy per year.
Source:
Dukes
2012
Table 1.1: UK 2011 total primary demand. Exact figure is 2469 TWh.
- The maximum rate at which energy is used by the UK is about 400 GW,
the minimum rate is about 100 GW.
- The UK spends £130 billion on energy each year.
Source:
Dukes
2012
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.
Four conversions
- A TWh (terawatt-hour) is a billion kWh (kilowatt-hours). A kWh is the unit
on my electricity bill.
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.
- A GW (gigawatt) is a million kW (kilowatts). A kW is the rate at which my small fan heater produces heat.
- 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.
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.
- A billion pounds is £16 for each man, woman and child in the UK.
Units
There are surprisingly many commonly-used units for energy.
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).
Hint:
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.
A caution
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.
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.