I listened with amusement last night to a CBC Ideas show featuring a story about an allegedly solar powered house in Toronto (the Ravina Project). I am always skeptical when I hear claims of how people have gone off the grid, especially when they live in cities. And for good reason: it takes a lot of energy to do ordinary household things like boil water for tea and make toast.
For example, let’s say you have friends over and want to make a pot of tea. Your teapot holds 1 liter, so you have to boil one liter of water. Well, it takes around 3.97 British Thermal Units (BTUs) to raise the temperature of one liter of liquid water by one degree celsius. Water boils at 100°C. So if you started with water that was at a temperature of say 15°C, you’d need around 337 BTUs to boil it (3.97 BTUs x 85°C).
What is the cleanest way to get those 337 BTUs? The Ravina Project house is, allegedly, now less dependent on grid electricity, so we can assume that its owners consider gas to be the better way.
Is it? Let’s compare the carbon dioxide (CO2) emissions involved in boiling one liter of water using natural gas versus those of using Ontario electricity.
According to the U.S. EPA, a million BTUs of natural gas will, when burned, emit 116.39 pounds of CO2. I’m Canadian, and use metric units. So a million BTU of gas will emit roughly 53 kilograms of CO2.
That works out to roughly 0.053 grams of CO2 per BTU. Remember from above that we need 337 BTUs to bring a liter of water from 15°C to 100°C. So if we got those 337 BTUs from natural gas, we would emit roughly 17.8 grams of CO2.
And if we got the 337 BTUs from an electric stove powered by electricity from the Ontario grid? Well, the grid’s CO2 intensity per kilowatt-hour tends to vary during the day, depending on the generators that make the electricity. Right now (ten a.m. on Saturday, August 4, 2012), CO2 intensity of Ontario electricity is roughly 140 grams of CO2 per kWh.
Our 337 BTUs work out to roughly 0.09 kWh. So 0.09 kWh of Ontario electricity at 140 grams CO2 per kWh comes to just over 13.83 grams of CO2.
So to get 337 BTU from gas and electricity, here’s the comparison:
|Natural gas||Ontario electricity|
|17.87 grams CO2||13.83 grams CO2|
The upshot: if you use a gas-fired stove to boil your tea, you’ll release slightly more CO2!
It turns out that the aforementioned house indeed uses a natural gas stove. And not just a gas stove. They heat their water and dry their clothes using natural gas as well.
Sorry, but that’s not green.
They would be greener if they just stayed on the grid.
More important is the fact that around 85 percent of the 140 grams of CO2 per kWh of Ontario electricity right now come out of natural gas-fired generating plants.
If there were less gas and more nuclear feeding the Ontario grid, the 140 grams of CO2 per kWh would drop.
And what if the water is preheated to 22 C. in a solar water heater? Then the off-grid house uses very little natural gas to heat to boiling and so uses much less CO2 than the grid. Your smug attitude is typical of the shills who maintain the status quo. I have been living off the grid for nearly 30 years and I guarantee it is much less a strain on the natural world than burning fossil fuels to create electricity so that millions of morons can boil their water.
Jonathan: if the water is preheated to 22°C then you need 309.66 BTUs, which works out to 16.42 grams (309.66 x 0.053) of GHGs. Still more than if you used Ontario electricity.
Off grid is only cleaner if (1) the grid is fed mostly with fossil-fired power and (2) you’re not using a car more.
I repeat: if electricity comes out of a grid that is fed primarily with zero-carbon sources, then it is much cleaner than burning gas. That is the case in Ontario. As I write this, Ontario generators are putting 17,203 MW into the grid. More than 72 percent of our electricity is coming from nuclear (9,769 MW) and hydro (2,665 MW). That’s the biggest reason that our carbon intensity right now is just under 124 grams GHGs per kWh. See http://www.ieso.ca
I can tell you from practical experience from relatives in Texas that virtually no one with “solar homes” outside green-zealot hermits totally detaches from the grid or portable generators, especially when a pinch comes — and it often does with more Co2 plus. If solar technology was as totally providing as its supporters claimed, nations would’ve been dumping all their power plants left and right long ago.
Years ago there was a Harrowsmith magazine article on a Toronto couple who had beautifully renovated an old corner store into a home. One of the couple had severe allergies, so they had used all sorts of low-vapour-emission paints/varnishes. So far, so good, but they proudly proclaimed how they significantly reduced their use of nuclear-generated electricity (Ontario Hydro at the time) by employing a wood stove! Using a wood stove in an urban environment, particularly when one of them had allergies!?!
Steve, do you know the story about the economist who walked across a river with AVERAGE depth of three feet — and drowned? That river depth is exactly as meaningful as your AVERAGE carbon-intensity of the Ontario electrical grid. When we put a pot of water on an electric stove, the grid doesn’t generate another AVERAGE tenth of a KWH, it generates an INCREMENTAL tenth of a KWH. Under normal sane circumstances, NONE of that electricity is from nuclear, hydro, or wind, because all of those sources are inflexible = “baseload”, used fully regardless of demand (even if we have to sell some at a loss).
At present ALL of the power to boil that extra pot of water — the pot that otherwise would be boiled on a natural-gas stove — is provided by fossil-fueled generators.
Think it through, please!
Norm, the drowned economist can be theoretically brought back to life by the successful crossing of at least two subsequent economists, thereby bringing the average drowned-per-crossing to less than one.
But seriously, your argument implies that the three-quarters of Ontario’s energy that comes with zero emissions are of no consequence. That is utterly wrong. You apportion GHGs to consumers on the basis of emission intensity (in grams per kWh) at time of use. The friends could show up for tea at ten p.m. on a Sunday, or at four-fifteen p.m on a Tuesday. How do I know? So I used average emission intensity.
That also covers the possibility—which it appears you overlooked—that the IESO dispatched a (zero-carbon) hydro station to handle the extra load, or that one of Bruce B’s (zero-carbon) generators was ramping up after ramping down earlier via steam bypass.