Summary:
Book on the scale of the energy channels. Not sufficient to know that a source of energy is "huge". We need to know how it compares with another "huge", namely, our huge consumption. Comparing numbers for demand with numbers for supply using renewables. Because renewable energy is so diffuse (between 0.1 and 14 W/m^2), it takes an enormous area of land (or sea) to provide the required 125 kWh/day per person. Provides four different energy plans to meet this need, each with different emphases (no carbon emissions, strong nuclear, no nuclear, etc.).
Currently reading.
Notes:
Preface
- Three different motivations drive today’s energy discussions
- fossil fuels are a finite resource
- seems possible that cheap oil (on which our cars and lorries run) and cheap gas (with which we heat many of our buildings) will run out in our lifetime
- given that fossil fuels are a valuable resource, useful for manufacture of plastics and all sorts of other creative stuff, perhaps we should save them for better uses than simply setting fire to them
- security of energy supply
- using fossil fuels changes the climate
- Climate change is blamed on several human activities, but the biggest contributor to climate change is the greenhouse effect produced by carbon dioxide (CO2).
- Most of the carbon dioxide emissions come from fossil-fuel burning.
- main reason we burn fossil fuels is for energy. So to fix climate change, we need to sort out a new way of getting energy
- climate change motivation runs in three steps:
- one: human fossil-fuel burning causes carbon dioxide concentrations to rise;
- two: carbon dioxide is a greenhouse gas;
- three: increasing the greenhouse effect increases average global temperatures.
- fact: the burning of fossil fuels is the principal reason why CO2 concentrations have gone up
- critics: burning of fossil fuels sends about seven gigatonnes of CO2 per year into the atmosphere, but biosphere and the oceans send about 1900 gigatonnes and 36 000 gigatonnes of CO2 per year into the atmosphere!
- misleading because only quantifies the natural flows of CO2 into the atmosphere, not mentioning that approximately the same amount flows back out of the atmosphere into the oceans and biosphere
- the natural flows cancel themselves out; burning fossil fuels creates a new flow that is not cancelled
- consensus of the best climate models seems to be that doubling the CO2 concentration would have roughly the same effect as increasing the intensity of the sun by 2%, and would bump up the global mean temperature by something like 3 deg C
- there is no doubt that such a rise is a bad thing
- such temperatures on earth have not been seen for at least 3 million years
- conceivable that the ecosystem will be so significantly altered that the earth stops providing some of the goods and services that we currently take for granted
- In the year 2000, world greenhouse gas emissions stood at about 34 billion tons of CO2 equivalent per year
- about 5 or 6 tons per year per person
- equivalent to every person burning one and a half tons of coal per year
- but: We don’t all emit 6 tons per year
- US: ~25 ton/year/person; UK: ~12 ton/year/person; China: ~ 4 ton/year/person
- i.e. US: ~4 times average; China
- Historical cumulative emissions
- Some countries like Britain have committed to a 60% reduction in greenhouse-gas emissions by 2050
- with such a reduction, climate scientists reckon it’s more likely than not that global temperatures will rise by more than 2 deg C
- global emissions need to fall by 70% or 85% by 2050 to avoid such a rise
- means Britain needs to get down from its current 10 or so tons of CO2 per year per person to roughly 1 ton per year per person by 2050
- This is such a deep cut that the best way to think about it is ‘no more fossil fuels’
- Yardstick #1: average current emissions are 1 ton of carbon per year per person
- or roughly 4 tons of CO2
- note: a round-trip intercontinental flight emits nearly two tons of CO2 per passenger (which is about half a ton of carbon), i.e. half of the average person’s annual carbon emissions
- Yardstick #2: we need average emissions to be 1/3 ton of carbon per year per person
- i.e. more than one intercontinental round-trip
- Debates about energy policy are often confusing and emotional because people mix together factual and ethical assertions
1. The balance sheet
- energy and power - units used in book
- energy: kWh
- aka ‘one unit’ on electricity bills
- cost ~10p in 2007
- individuals typically use a few kWh/day
- power: kWh/d; occasionally Watt or kiloWatt
- rate at which we use or produce energy
- 1 kWh/d is roughly the power you could get from one human servant
- 40 W ~ 1 kWh/d
- i.e. a 40W light bulb left switched on all day uses about 1 kWh/d, costing the consumer about 10p/day
- i.e. a 1000W toaster uses 1 kWh/h, or costs about 10p/hour, or 240p/day
- 1kW ~ 25 kWh/d
- Joule: standard international unit of energy
- too small to work with: 1 kWh ~ 3.6 MJ
- 1 W = 1 J/s
- most commonly used units in public documents
- terawatt-hours per year (TWh/y)
- 1000TWh/y per United Kingdom is roughly equal to 45 kWh/d per person
- gigawatts (GW)
- 2.5GW per UK is precisely 1 kWh/d per person
- million tonnes of oil equivalent per year (Mtoe/y)
- 2 Mtoe/y per UK is roughly 1 kWh/d per person
2. Cars
- power consumed by daily car user
- energy used (50km) = 40 kWh/d
- km travelled per day * energy per litre of fuel / km per litre of fuel
- energy per litre of fuel, or calorific value of petrol
- km per litre of fuel
- km travelled per day
3. Wind
- maximum conceivable wind power per person = 200 kWh/d
- assuming 100% coverage
- = wind power per area x area per person
- power per unit area of windfarm is about 2W/m^2
- for average windspeed of 6m/s (22km/h)
- population density
- 8 kW per person = 200 kWh/d per person
- more realistic: maximum conceivable wind power = 20 kWh/d per person
- assuming 6m/s and 10% filling
- conclusions:
- if we covered the windiest 10% of the country with windmills, we might be able to generate half of the energy used by driving a car 50 km per day each
- Britain’s onshore wind energy resource may be “huge,” but it’s not as huge as our huge consumption
- windmills required to provide the UK with 20 kWh/d per person are
- fifty times the entire wind hardware of Denmark;
- seven times all the windfarms of Germany;
- double the entire fleet of all wind turbines in the world
- Whitelee windfarm being built near Glasgow in Scotland
- has 140 turbines with a combined peak capacity of 322MW in an area of
55 km2 - that’s 6W/m2, peak
- if we assume a capacity (load) factor of 33% then the average power production per unit land area is 2W/m2
4. Planes
- assuming one intercontinental round-trip per year (2 x 10,000 km):
- average energy consumption per person per day = 30 kWh per day
- i.e. flying once per year has an energy cost slightly bigger than leaving a 1 kW electric fire on, non-stop, 24 hours a day, all year
- would air travel consume much less energy if we travelled in slower propellor-driven planes?’
- no: planes are already almost as efficient as they could possibly be
5. Solar
