Whenever a renewable power facility is described they always say how many 'homes' it will power. Today's news says The 100MW Glendoe Hydro Scheme will be able to power around 250,000 homes – equivalent to a city the size of Glasgow.
I think this 'homes' description is really misleading, because I bet people confuse 'powering all the homes in Glasgow' with 'powering all Glasgow's electricity' or even 'powering all Glasgow's energy'.
Let's do a simple calculation.
The average expected power from Glendoe is 180 GWh per year [source]. Now
if we take 180 GWh per year and share it between a Glasgow of people
(616,000 people), we get 0.8 kWh/d per person.
OK; what is the average electricity consumption per person (including all forms of electricity, not just domestic)? Answer: 16 kWh/d per person. So Glendoe actually provides 5% of the electricity consumption of Glasgow.
So if people get the impression from the press releases that Glendoe will power Glasgow, they have been misled by a factor of twenty!
This is a bigger factor than the normal factor by which people are usually misled. The statement
that Glendoe (180 GWh/y) would power 250,000 homes implies that each 'home' uses just 720 kWh per year. But the normal assumption in press releases about wind or tide is to assume the average home uses 4000 kWh/y or 4700 kWh/y. What's going on? The ratio between 720 kWh and 4000 kWh (18%) is suspiciously similar to the ratio between the average power production of Glendoe (180 GWh/y) and its capacity (100 MW is equivalent to 877 GWh/y). Methinks that someone at Scottish and Southern must have screwed up (or deliberately misled the public) by pretending that Glendoe will produce 100MW 100% of the the time, whereas in fact it will have an average load factor of 20%.
Monday, January 7, 2008
Thursday, December 27, 2007
Carbon Carousel Fraud
Letter to the editor
The Independent Sent 27 December 2007
Sir,
the article 'My carbon-free year' (Independent Thursday 27 December 2007) claims that Donnachadh McCarthy's home was `carbon-negative for energy' during 2007. This would be great if it were true, but the claimed carbon footprint of -141 kg was obtained only by using a carbon carousel fraud.
The home sometimes exported and sometimes imported green electricity. For every kWh of electricity exported, the net footprint was credited with -430g of CO2. Fair enough. But when the home imported a kWh of electricity, the effect on the footprint was declared to be zero. This is a fraud, since under this accounting system a building that imports 1 kWh on Monday and exports 1 kWh on Tuesday (and thus makes no net contribution) would be judged to have removed 430g of CO2 from the atmosphere! When this error is corrected, we find that Donnachadh McCarthy's impressive home is not carbon negative. It has a CO2 footprint of +24 kg.
It is a terrible struggle to make a British home carbon neutral!
yours
David MacKay
PS
Here are the details of the correct spreadsheet
``How the eco-savings add up''
PPS - They didn't publish my letter.
The Independent Sent 27 December 2007
Sir,
the article 'My carbon-free year' (Independent Thursday 27 December 2007) claims that Donnachadh McCarthy's home was `carbon-negative for energy' during 2007. This would be great if it were true, but the claimed carbon footprint of -141 kg was obtained only by using a carbon carousel fraud.
The home sometimes exported and sometimes imported green electricity. For every kWh of electricity exported, the net footprint was credited with -430g of CO2. Fair enough. But when the home imported a kWh of electricity, the effect on the footprint was declared to be zero. This is a fraud, since under this accounting system a building that imports 1 kWh on Monday and exports 1 kWh on Tuesday (and thus makes no net contribution) would be judged to have removed 430g of CO2 from the atmosphere! When this error is corrected, we find that Donnachadh McCarthy's impressive home is not carbon negative. It has a CO2 footprint of +24 kg.
It is a terrible struggle to make a British home carbon neutral!
yours
David MacKay
PS
Here are the details of the correct spreadsheet
``How the eco-savings add up''
| CONSUMED | CO2 footprint | |
Gas usage | 609 kWh | 116 kg |
NET export of green electricity (598-384) | 114 kWh | -92 kg |
Solar electricity produced and used on-site | 420 kWh | zero |
(Other items in the table all as before, zero.) | ||
Net footprint | +24 kg | |
PPS - They didn't publish my letter.
Tuesday, October 30, 2007
Life-cycle analysis database
Yippee! I've been trying to find a free database of LCA information (to answer questions like 'what's the embodied energy or embedded energy of a fluorescent light bulb?') and now I think I have found one - http://lca.jrc.ec.europa.eu/lcainfohub/introduction.vm
Sadly the EU database didn't seem very user friendly. I've now found the
The University of Bath database
which looks small but useful.
Update...
Sadly the EU database didn't seem very user friendly. I've now found the
The University of Bath database
which looks small but useful.
Climate change in our lifetime
My first blog. (I've been writing webpages for ages, but I thought a blog might be useful for my soon to be finished book.)
1998 was a record hot year (the hottest in the last few decades). Today I heard in a talk by Vicky Pope that the climate models of the Hadley Centre predict that from 2010 onwards, every year has a 50% chance of being hotter than 1998.
Vicky Pope also showed a graph by Eleanor Burke showing predicted droughts. The graph showed the percentage of the world predicted to have "severe drought". In the past this percentage has bobbled around 2 or 3%. By 2060 it was projected that the percentage would be up to 20%.
I hadn't seen climate change expressed by climate scientists in such strikingly 'soon' terms.
1998 was a record hot year (the hottest in the last few decades). Today I heard in a talk by Vicky Pope that the climate models of the Hadley Centre predict that from 2010 onwards, every year has a 50% chance of being hotter than 1998.
Vicky Pope also showed a graph by Eleanor Burke showing predicted droughts. The graph showed the percentage of the world predicted to have "severe drought". In the past this percentage has bobbled around 2 or 3%. By 2060 it was projected that the percentage would be up to 20%.
I hadn't seen climate change expressed by climate scientists in such strikingly 'soon' terms.
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