week 9: Some Sums What I Did
Enviado: 25 ago 2011, 14:00
week 9: Some Sums What I Did
"Robert tries to work out how much electricity his Leaf is using, and how much CO2 he's emitted so far.
By Robert Llewellyn on June 27, 2011 10:00 AM
The solar panels on my office roof have been operating for one month now and so far they have generated 253-kilowatt hours of electricity. If you consider what the UK weather has been like over the past four weeks – rain, clouds, rain, oooh, look, the sun, oh no it’s gone, rain, low clouds, rain etc, etc I think you’ll agree that’s not bad. According to British Gas, the people who installed the panels, the average UK household (a three bedroom semi) uses around 10 kWh daily. So it’s not quite there – an average house would use in the region of 300 kWh a month.
In the same four week period we have driven the Nissan Leaf 1,326 miles and as I now have a dedicated meter telling me how much power the car is drawing, I am getting a much more accurate picture.
The car has used 335 kWh, which my calculator tells me means the car is using roughly 0.25 kWh per mile. I want to point out here that I have many failings and weaknesses, but maths is my biggest. However, I was very thrilled to discover that the official reading on the car’s energy calculator states 0.25 kWh per mile average, so I’m chuffed, thank you Mr Billsborough (the primary school teacher who pushed me very hard to pass the 11 plus.)
Another way of looking at it, and this is particularly relevant with the plethora of recent ‘Electric Cars not Green After All!’ stories and the endless repetition of ‘Yeah, but Bobby, you have to burn coal to make the electricity’ is that the car has used 82 kWh of power from the filthy, coal burning, massively polluting, unregulated carbon chundering grid. (Just to clarify I’m using sarcasm here, the grid is heavily regulated and carbon emissions are reducing rapidly).
To give a rough cost, I charge the car between midnight and 7am (using the Nissan Leaf’s built-in charge timer) and the cost per kilowatt-hour off peak is just under 5p. So that’s £4.10p. To drive 1,326 miles.
But far more importantly, the Co2 output per kilometer, and this is going to tax my calculator skills, is as follows:
If you take the most pessimistic calculations for an electric car charged solely from the grid, the suggested figure for what is released into the atmosphere to generate the electricity is about 80 grams of Co2 per mile. (I hotly dispute this and have seen wildly varying figures, most common is closer to 40 grams per mile, but I’m being generous, I’ll clench my little fists and accept 80).
Accepting that 335 kWh produces 80 grams of CO2 per mile when used in a car, I’ve driven 1,326 miles but only used 82 kWh of carbon emitting electricity, if I divide those numbers I come up with a rather astonishing result. The Nissan Leaf has been emitting 0.06 kilograms of CO2 per mile.
I’m a bit hesitant, so I’ll try another way of coming up with a reliable figure. I’m going to say one third of the electricity I used to power the car came from the filthy, smoke-belching grid (only 30% of our electricity in the UK is generated from burning coal, and the carbon capture technology being introduced is dropping the Co2 outputs of these plants dramatically, but hey, I’m being generous). I’m going to divide the total kWh usage by 3, which results in 111.6 kWh. I’ll now divide 1,326 miles by 3, which is 442 miles.
I know that 111.6 kWh is way more than 82 kWh, but it’s close enough for my rubbish calculations and it’s erring on the side of caution rather than optimism. So 442 miles at 80 grams per mile is 35.36 kilograms. But I actually drove 1,326 miles, so divide 35.36 kg by 1,326 and you get 0.02 grams of Co2 per mile. If I am even vaguely right, even in the same basic municipality, let alone ballpark, that is a truly astonishing 0.02 grams per mile. I’m anxious now, I can see Mr Billsborough looking over my shoulder and sadly shaking his head. How many times has he explained? Why do the numbers go into a blur, why wasn’t I diagnosed as having dyscalculia when I was 11. Life would have been so much easier.
Okay, so just in case, if I divide 1,326 miles by 35.36 kg I get 37.5 grams per mile.
One of them is right, both of them are very, very low.
Finally, let me just remind you, because I’m annoying and I’m not allowed to talk about this in the kitchen at home – at the very best, the most super, clean burn, catalytic encumbered petrol/diesel car is chucking out 90 grams a mile, and that is of course not including what is released before the fuel reaches the pump. But that’s my pointless hobbyhorse so I won’t go on.
I await your comments with some dread."
Em: http://www.thechargingpoint.com/opinion ... i-did.html
"Robert tries to work out how much electricity his Leaf is using, and how much CO2 he's emitted so far.
By Robert Llewellyn on June 27, 2011 10:00 AM
The solar panels on my office roof have been operating for one month now and so far they have generated 253-kilowatt hours of electricity. If you consider what the UK weather has been like over the past four weeks – rain, clouds, rain, oooh, look, the sun, oh no it’s gone, rain, low clouds, rain etc, etc I think you’ll agree that’s not bad. According to British Gas, the people who installed the panels, the average UK household (a three bedroom semi) uses around 10 kWh daily. So it’s not quite there – an average house would use in the region of 300 kWh a month.
In the same four week period we have driven the Nissan Leaf 1,326 miles and as I now have a dedicated meter telling me how much power the car is drawing, I am getting a much more accurate picture.
The car has used 335 kWh, which my calculator tells me means the car is using roughly 0.25 kWh per mile. I want to point out here that I have many failings and weaknesses, but maths is my biggest. However, I was very thrilled to discover that the official reading on the car’s energy calculator states 0.25 kWh per mile average, so I’m chuffed, thank you Mr Billsborough (the primary school teacher who pushed me very hard to pass the 11 plus.)
Another way of looking at it, and this is particularly relevant with the plethora of recent ‘Electric Cars not Green After All!’ stories and the endless repetition of ‘Yeah, but Bobby, you have to burn coal to make the electricity’ is that the car has used 82 kWh of power from the filthy, coal burning, massively polluting, unregulated carbon chundering grid. (Just to clarify I’m using sarcasm here, the grid is heavily regulated and carbon emissions are reducing rapidly).
To give a rough cost, I charge the car between midnight and 7am (using the Nissan Leaf’s built-in charge timer) and the cost per kilowatt-hour off peak is just under 5p. So that’s £4.10p. To drive 1,326 miles.
But far more importantly, the Co2 output per kilometer, and this is going to tax my calculator skills, is as follows:
If you take the most pessimistic calculations for an electric car charged solely from the grid, the suggested figure for what is released into the atmosphere to generate the electricity is about 80 grams of Co2 per mile. (I hotly dispute this and have seen wildly varying figures, most common is closer to 40 grams per mile, but I’m being generous, I’ll clench my little fists and accept 80).
Accepting that 335 kWh produces 80 grams of CO2 per mile when used in a car, I’ve driven 1,326 miles but only used 82 kWh of carbon emitting electricity, if I divide those numbers I come up with a rather astonishing result. The Nissan Leaf has been emitting 0.06 kilograms of CO2 per mile.
I’m a bit hesitant, so I’ll try another way of coming up with a reliable figure. I’m going to say one third of the electricity I used to power the car came from the filthy, smoke-belching grid (only 30% of our electricity in the UK is generated from burning coal, and the carbon capture technology being introduced is dropping the Co2 outputs of these plants dramatically, but hey, I’m being generous). I’m going to divide the total kWh usage by 3, which results in 111.6 kWh. I’ll now divide 1,326 miles by 3, which is 442 miles.
I know that 111.6 kWh is way more than 82 kWh, but it’s close enough for my rubbish calculations and it’s erring on the side of caution rather than optimism. So 442 miles at 80 grams per mile is 35.36 kilograms. But I actually drove 1,326 miles, so divide 35.36 kg by 1,326 and you get 0.02 grams of Co2 per mile. If I am even vaguely right, even in the same basic municipality, let alone ballpark, that is a truly astonishing 0.02 grams per mile. I’m anxious now, I can see Mr Billsborough looking over my shoulder and sadly shaking his head. How many times has he explained? Why do the numbers go into a blur, why wasn’t I diagnosed as having dyscalculia when I was 11. Life would have been so much easier.
Okay, so just in case, if I divide 1,326 miles by 35.36 kg I get 37.5 grams per mile.
One of them is right, both of them are very, very low.
Finally, let me just remind you, because I’m annoying and I’m not allowed to talk about this in the kitchen at home – at the very best, the most super, clean burn, catalytic encumbered petrol/diesel car is chucking out 90 grams a mile, and that is of course not including what is released before the fuel reaches the pump. But that’s my pointless hobbyhorse so I won’t go on.
I await your comments with some dread."
Em: http://www.thechargingpoint.com/opinion ... i-did.html
