Some Myths and Surprises
about energy and carbon emissions
Nicola Terry
http://nicola.qeng-ho.org
http://energy-surprises.blogspot.com
Energy and Carbon Emissions: the way we live today
This presentation was prepared using s5. Type 't' for outline mode with explanations.
Contents
- Some interesting facts from my book: A Fact Book of Energy and Carbon Emissions (published May 2011)
- Wide range of topics, mainly personal activities in the UK
Tidal/Wave/Wind energy resource
Myth: We don't need ugly wind turbines because there is plenty of power in the tides, or nuclear ...
Data from
DECC 2050 pathways analysis - limit of practicability, regardless of cost.
- Nuclear limit is how much can be built by 2050
- 146 GW = 120 Sizewell B's
- potential longer term uranium supply issues
- and still waiting for disposal facility for radioactive waste
- Tidal energy dissipated globally is 3.75 TW. World energy usage is 15 TW.
- Friction means the moon is receding from the earth and day length is increasing.
Being a veggie(1)
Myth: Becoming a vegetarian will help save the planet
grammes CO2e per 100g except 2 eggs or 50g cheese
|
|
|
|
|
| 780 |
560 |
550 |
440 |
90 |
| pork |
chicken |
eggs |
cheese |
lentils |
Cheese, milk, cream and eggs are just as bad as meat
because animals are inefficient protein concentrating machines.
To help save the planet: Eat less animal products of all kinds.
Being a veggie(2)
Myth: Becoming a vegetarian will help save the planet
grammes CO2e per 100g
|
|
|
|
|
| 30 |
100 |
240 |
60 |
460 |
 |
 |
 |
 |
 |
| Fresh |
Frozen |
Local |
Madrid |
Nairobi |
- Exotic fruit and vegetables can be just as bad as meat if imported by air.
- Importing by road, train or ship is not nearly so bad.
- Frozen and canned vegetables are roughly similar in carbon emissions depending on distance travelled (heavy can) and time frozen.
Organic is good
Myth: Organically grown food is more sustainable
Organic:
| Wheat needs less energy
| Tomatoes need more energy
|
| Lamb generates less GHGs
| Beef generates more GHGs
|
| Green manure crops 'mine' earth minerals |
Sustainability requires using only renewable inputs and recycling all the nutrients.
- Wheat needs lots of fertiliser - chemical fertiliser has lots of energy
- Organic tomatoes (grown in greenhouses) have lower yield per unit area so higher heating cost
- Bigger differences in yield from different varieties
- Organic sheep and cattle both need less energy
- Organic cattle grow more slowly
Energy payback for Solar Panels
Myth: Solar PV panels take as much energy to make as they generate in their lifetime
Solar panels: 3-6
|
CCGT power stations: 2-5
|
Wind turbines: 9-34
|
Nuclear power: 14-16
|
- The payback for solar panels is not great but definitely positive and coming down. The Sahara Solar Breeder project would reduce carbon emissions for PV.
- For CCGT, the energy payback is just as bad as for solar panels if you count the energy used to locate, extract, process and transport the fuel.
- The energy payback for wind turbines is similar to nuclear power but the wind farms probably have lower carbon emissions than nuclear.
Sources for energy payback:
Hydro Quebec 2005 and
Energy Enviro Finlad 2006
Sources for Carbon emissions: getme.
Sources for Sahara Solar Breeder
New Scientist. It is a joint project by Algerian and Japanese universities.
<--!>
Roof insulation
Myth: From an uninsulated house you will lose 25% of your energy through the roof.
|
True but irrelevant. Only applies to 1 in 30 houses!
Every house is different.
|
|
- For Victorian house with solid walls and 50mm insulation
- walls lose heat 4 times as fast as the roof (per unit area)
- more roof insulation saves perhaps 7% overall.
- The first 50mm of insulation cuts heat loss by 75%.
- The first 100mm of insulation cuts heat loss to about the same as a filled cavity wall.
Kettles
Surprise: Buying an eco kettle can pay back embodied carbon emissions in days
|
- Modern kettle has low minimum fill and accurate measures
- Avoiding 1 extra mug full (0.25 litres) saves 16g CO2
- Embodied emissions in kettle say 2000 gCO2
- Payback after 2000/16 = 125 uses
- 5 times a day: 125/5 = 25 days
|
Cars
Surprise: A new eco-car will take years to pay back embodied carbon emissions (Unless you drive an awful lot)
Toyota Prius Hybrid
|
- Manufacturing 5,700 kg CO2
- says Toyota - How Bad are Bananas says 13-17 tonnes
- Running: 89 gCO2/km - cf 190 for oldish diesel
- Payback 5,700/(.190-.089) km
= 57,000 km
|
TV vs. Book
Surprise: Watching TV generates less carbon emissions than reading a book
|
| Book 
| TV 
|
| Embodied CO2
| 2.5 kg (Penguin)
| 220kg (How Bad are Bananas)
|
| Time used
| 10 hours
| 2 hours/day 5 years = 3650 hours
|
| Embodied CO2/hour use
| 250g
| 60g
|
| Usage CO2/hour
| 0
| Assume 80W -> 40g
|
| Total CO2/hour use
| 250g
| 100g
|
| If 2 people watching
| 250g
| 50g
|
| If read book 5 times
| 50g
| 50g
|
Library books are read on average 4.6 times per year.
Horse vs. Van
|
Surprise: For the same useful energy, a horse needs 150 times as much space as an electric van
|
Area needed to generate 1 kWh/day (square metres)
| Solar PV | Horse pulling cart |
| First approximation (horse generates 750W for 8 hours, needs 2 hectares)
| 2.1
| 3370
|
|
Payload efficiency (van 1.0/3.5, horse 0.72/1.0)
| 7.2
| 4700
|
|
Electric motor is only 80% efficient
| 9.3
| 4700
|
|
Allow for embodied energy (van 42 MWh over 10 years, horse working life 5-15 years)
| 33
| 5400
|
- The van is powered by solar pv panels. 2.1 m2 supplies 1 kWh/day
- Payload efficiency:
- The unladen van is 2.5t and it can carry 1t load.
- The horse can pull 1t of which 280kg is cart and driver.
What does this tell us?
- Beware extravagant claims
- Don't jump to conclusions
- Do look at the figures - you might be surprised
- Use your imagination
- Look forward rather than back
Your thoughts?
Recycled
Reused