Many of our tech-savvy friends — the kind of folks who nurse along the beowulf clusters our climate models run on — are scratching their heads over some cheeky shrieking that recently appeared in a WIRED magazine article on Rethinking What it Means to be Green . Crank up the A/C! Kill the Spotted Owl! Keep the SUV! What’s all that supposed to be about?
Let’s take air conditioning for starters. Basically WIRED took a look at the carbon footprint of New England heating vs. Arizona cooling and jumped to the conclusion that air conditioning was intrinsically more efficient than heating. To see where they were led astray let’s consider a house sitting where you need to cool it by 20 degrees to be comfortable. The heat leaks into the house at a rate that is approximately proportional to this temperature difference, and the heat leaking in needs to be removed. Now, in order to move that heat from inside to outside, energy has to be expended. Given a fixed electric power usage (in watts), a better air conditioner can remove more heat per day than a worse one, but every air conditioner needs to expend some energy to move the heat. That’s just thermodynamics.
Efficiency of air conditioners is measured by a SEER rating, which is the ratio of heat moved to the outside (in BTU/hr) to the electric power consumption (in Watts). A typical modern air conditioner has a SEER rating of 10, We can convert this into nicer units by converting BTU/hr into Watts, which means dividing the SEER rating by 3.413, which then gives us a Coefficient of Performance, in units of Watts of heat moved per Watt of electricity used. For the aforementioned efficiency, we move heat at a rate of 2.92 Watts if we expend 1 Watt of electric energy. An air conditioner is just a heat engine run in reverse: instead of making use of a temperature differential to use heat flow from hot to cold to do work, we expend mechanical work in order to move heat from a colder place to a hotter place. Thus, an efficient heat engine is an inefficient air conditioner. That’s basically why the Coefficient of Performance gets smaller when the temperature difference between indoors and outdoors is greater — with bigger temperature difference heat engine cycles tend to get more efficient, which means that air conditioner cycles tend to get less efficient. That’s also where the “S” in SEER comes from. It stands for “Seasonal,” and reflects the fact that efficiency must be averaged over the range of actual temperature differentials experienced in a “typical” climate. Your mileage may vary.
This situation can be contrasted with heating. If that same house were in an environment that were too cold instead of too warm, so that it had to be kept 20 degrees warmer than the environment, then the amount of heat leaking out of the house each day would be about the same as the amount leaking into the house in the previous case. That heat loss needs to be replaced by burning fuel. Now, generating heat is the only thing that can be done with 100% efficiency. Old furnaces lose a lot of heat up the chimney, but modern sealed-combustion burners– the kind that can use PVC pipes instead of a chimney — lose virtually nothing. With a heat exchanger between the air intake and the exhaust, they could closely approach the ideal. But still, in this case we are generating heat rather than just moving it, so it takes 1 watt of heat power from fuel burning to make up 1 watt of heat loss. That would seem to make heating a factor of 2.92 less efficient than air conditioning.
But wait, the story doesn’t stop there. First, there’s the fact that air conditioning almost invariably runs off of electricity, and the increased electricity demand is a big source of the pressure to build more coal-fired power plants. A house can be heated by burning natural gas, and right there air conditioning becomes 1.8 times worse than heating, because natural gas emits only 55% of the carbon of coal, per unit of heat energy produced. And it gets even worse: Coal fired power plants are only 30% efficient at converting heat into electricity, on average, so there you get another factor of 3.3 in carbon emissions per unit of energy transferred between the house and its environment. Finally, figure in a typical electric line transmission loss of 7% and you get another factor 1.075. Put it all together with the energy efficiency of the air conditioner itself and air conditioning comes in at a whopping 2.19 times less efficient than heating. for a given amount of temperature difference between house and environment. That means that so far as carbon emissions go, heating a house to 70 degrees when the outside temperature is 40 degrees is like cooling the same house to 70 degrees when the outside temperature is 83.7 degrees.
And that’s still not the end of the story. A house in need of air conditioning has other heat inputs besides the heat leaking in from outside, and all that extra heat needs to be gotten rid of as well. For example, heat is a waste-product of all energy use going on in the house. Four people produce 400W that needs to be gotten rid of, and then there’s the heat from hot water, lighting, the TV, cooking and what have you — all the energy usage within the house, plus 100W of biological heat per person needs to be gotten rid of. On top of that, you’ve got direct radiative heating from the sun, both from the sunllight getting through windows and solar heating of the exterior surfaces of the house, some of which will leak in through the insulation. Energy must be expended to remove all this heat. In contrast, in the heating season waste heat is subtracted from the energy needed for home heating.
So, WIRED got the story egregiously wrong, and not just because they did the arithmetic wrong. In their rush to be cute, they didn’t even make a half-baked attempt to do the arithmetic. But what if they had been right and air conditioning really were intrinsically more efficient than heating. Would that justify their conclusion that you can just "crank up the A/C?" without worry? No, of course not, because cranking up the A/C would still use additional energy and still lead to the emission of additional carbon. For the conclusion to be justified, it wouldn’t be enough for A/C to be more efficient than heating; it would have to be so much more efficient that the incremental energy usage from cranking it up were trivial. WIRED didn’t even try to make that case. If they had, they might have spotted their errors.
Is there any real conclusion that could have been drawn from more clear thinking about the heating vs. air conditioning issues danced around in the article? Yes, in fact. The conclusion is that it makes a lot of sense to build houses in places where the environment requires neither much heating nor much cooling. This is in fact why Los Angeles scores pretty well in carbon footprint per capita, despite all the driving (as noted recently in The Economist.). Another conclusion to be drawn from the carbon footprint of New England heating is that there are probably a lot of leaky homes up there heated by inefficient oil-fired furnaces. Fixing that situation represents a huge untapped virtual energy source.
What’s more, for a magazine that purports to be written by and for tech geeks, WIRED missed the biggest and most interesting part of the story: the same intrinsic efficiences of heat pumps can be run in reverse to give you the same economies for home heating as you get for air conditioning. To do this effectively, you’d have to run the heat pump off of natural gas rather than electricity (or perhaps run it off of locally generated solar power or wind). You’d also have to deal with the fact that heat pumps become less efficient when working across large temperature gradients, but that’s where geothermal heat storage systems come in, making use of the fact that the deep subsurface temperature remains near a nice 55F all year around. Now that would have been a nice story for a tech magazine to cover. And by the way, the decrease in efficiency of heat pumps as the temperature differential increases has another implication that WIRED missed: not only does global warming increase the basic demand for air conditioning, with all the attendant pressures on electricity demand, but it exacerbates the situation by decreasing the efficiency of the entire installed base of air conditioners.
Now about that spotted owl. This refers to a claim that industrial tree plantations take up carbon faster than old growth forests; Since spotted owls require the large trees found only in old-growth, the supposed implication is that if we want to soak up carbon we ought to damn the spotted owl and cut down all the old growth. WIRED really committed serial stupidities on this one. First of all, the article they cited in support of their claim was about carbon emissions from Canada’s managed forests, not from old growth. Now, it’s true that a rapidly growing young tree takes carbon out of the atmosphere more rapidly than a mature forest which more slowly transfers carbon to long term storage in soil. However, to figure out how much net carbon sequestration you get out of that young tree once it’s chopped down, you need to figure what happens to it. Lots of trees wind up in paper, carboard boxes, shipping palettes and other things that rapidly sit around decomposing or get burned off (or worse, turn into methane in landfills). Even the part that turns into houses has a relatively short residence time before being oxidized. Anybody who has maintained an old Victorian house knows about the constant battle against rot, and the amount of wood that needs to be replaced even if (knock wood) the thing doesn’t burn down or turn into a tear-down. So, WIRED is totally off the mark there, unless, to use the colorful language of my colleague Dave Archer, they can get trees to "drop diamonds instead of leaves."
Worse, they ignore the abundant literature indicating that old growth forests can be a net sink of carbon even in equilibrium, whereas the soil disturbance of clear cutting and industrial forestry can lead to large soil carbon releases. A classic article in the genre is "Effects on carbon storage of conversion of old-growth forests to young forests" (Harmon et al. Science 1990) . They state "Simulations of carbon storage suggest that conversion of old-growth forests to young fast-growing forests will not decrease atmospheric carbon dioxide (CO2) in general, as has been suggested recently.". For more recent work, take a look at what Leighty et al. (ECOSYSTEMS Volume: 9 Issue: 7 Pages: 1051-1065. 2006 ) have to say about the Tongass:.
- "The Tongass National Forest (Tongass) is the largest national forest and largest area of old-growth forest in the United States. Spatial geographic information system data for the Tongass were combined with forest inventory data to estimate and map total carbon stock in the Tongass; the result was 2.8 +/- 0.5 Pg C, or 8% of the total carbon in the forests of the conterminous USA and 0.25% of the carbon in global forest vegetation and soils. Cumulative net carbon loss from the Tongass due to management of the forest for the period 1900-95 was estimated at 6.4-17.2 Tg C. Using our spatially explicit data for carbon stock and net flux, we modeled the potential effect of five management regimes on future net carbon flux. Estimates of net carbon flux were sensitive to projections of the rate of carbon accumulation in second-growth forests and to the amount of carbon left in standing biomass after harvest. Projections of net carbon flux in the Tongass range from 0.33 Tg C annual sequestration to 2.3 Tg C annual emission for the period 1995-2095. For the period 1995-2195, net flux estimates range from 0.19 Tg C annual sequestration to 1.6 Tg C annual emission. If all timber harvesting in the Tongass were halted from 1995 to 2095, the economic value of the net carbon sequestered during the 100-year hiatus, assuming $20/Mg C, would be $4 to $7 million/y (1995 US dollars). If a prohibition on logging were extended to 2195, the annual economic value of the carbon sequestered would be largely unaffected ($3 to $6 million/y). The potential annual economic value of carbon sequestration with management maximizing carbon storage in the Tongass is comparable to revenue from annual timber sales historically authorized for the forest."
So, it looks like that old Spotted Owl and its kindred old-growth denizens are in fact sitting not just on a nest, but on a treasure trove of carbon credits worth potentially more than the timber harvest.
And should you keep that SUV? This blurb in fact contains some useful advice, buried amidst some fuzzy reasoning and published over a witless tag line stating that "pound for pound" a Prius takes more energy to manufacture than a Hummer. The apparent implication of that tag line is rebutted in the article itself, but why give the reader that as a 32-point type take-home point when the WIRED editors don’t even themselves believe it’s an important statistic? This factoid refers to the energy used in the nickel component of Prius batteries, but it’s irrelevant because "pound for pound" doesn’t count if your point is moving 4 people from point A to point B. What transport value do you get from transporting four people plus the weight of the Hummer? Now, the rest of the fuzziness in the logic is a bit more subtle. The author notes quite rightly that there is a very significant carbon emission from manufacturing a car, which is indeed more for a Prius (at least for the moment) than it is for comparable sized non-hybrids.. Thus, if you are faced with ditching your existing car (whatever it may be) and buying a Prius, you need to consider how much you drive per year and see how long it takes to "pay back" the carbon emission from manufacturing the Prius. So far so good. But this is more a statement about the transition to more efficient cars, and how to deal with mistakes of the past, rather than a statement about what is intrinsically desirable in the fleet. As far as carbon emissions go, we’d still be better off if everybody who needed a car were in a Prius, except maybe for people who drive very little per year — who should then be into shared hybrids via iGO or ZipCars, Maybe if you drive very little and live out in a rural area where there are not going to be any shared cars, getting a compact non-Hybrid might make sense. There must be at least a dozen or two people out there in that category, I guess.
The rest of the advice WIRED gives makes even less sense. They say that if you want to be green, you ought to buy a used Civic or something like that, not a Prius. That’s because the used car already has the manufacturing carbon emissions "written down" (or, I guess at least the carbon guilt accrues to the original owner, not that the atmospheric radiative forcing is going to care much about that). However, this advice, sensible-sounding though it is — ignores the fact that to make that used car available to you, the original owner almost certainly had to buy something else, and probably that was a new car, or at least a newer one. So, for the scheme to work, you’d have to buy your used Civic from somebody who was giving up driving altogether. I no longer own a car myself, but I’m sorry I wasn’t able to participate in a scheme like this; by the time I gave up our remaining car ten years ago, it was suitable only for the crusher, and in fact had to be towed there.
The real implication is that manufacturing costs count, so most people should buy a small, efficient hybrid and keep it until it runs into the ground. The implication is also that durability of cars counts for nearly as much as gas mileage, since an efficient car that needs to be replaced every five years isn’t really all that efficient.
Along with all the nonsense is a certain amount of true (if by now commonplace) advice. Among this is the basic truth that urban living is inherently green, and if more people lived in cities (and if more cities were kept livable so people would want to move there). then per capita carbon emissions would go down. Even there, the Economist managed to be both more informative and more iconoclastic with its surprising analysis of the pattern of urbanism in Los Angeles. The other truism in WIRED is that nuclear power deserves a second look, and probably has an important role to play in a decarbonized energy future. Still, if you compare the cost of making all those chilly New England homes efficient with the total true cost of building more nuclear plants, well, let’s just say I’m buying stock in argon-filled low-e window manufacturers rather than Areva, much as I like their track record on nuclear electricity.
Re #44 Tim Joslin, Raypierre, it’s important to add that it is ecologically healthy for forests to have 1% or 2% blowdown every year, creating sunny clearings where rarer organisms conduct their intermittent life cycles — including some beautiful woodland flowers which it takes you luck to find. Further, the rotting wood is an absolutely necessary part of the life cycle and the food chain of a huge number of soil microbes, insects and insectivores. Moreover, occasional fires may be necessary to release minerals on decadal-or-longer cycles, and to coincide with the population-density requirements of various species. The optimal frequency for fire differs with the type of forest.
Picking on mature forests, not to mention old growth, for the rotting wood as a CO2 problem, is a bit like advocating the bulldozing of the world’s great cathedrals and mosques because this would provide sites for nice power plants.
Wired’s larger point, as I take it, is that environmentalists must accept compromises.
Certainly not, if the arguments are this silly.
OT: what happened to https://www.realclimate.org/index.php/archives/2007/10/oregon-institute-of-science-and-malarkey/ – I’m getting a 404.
TIA.
[Response: works for me…. – gavin]
Thank you for helping to refute Wired’s assertion that logging older forests and replacing them with tree farms can help fight global warming. I would just like to supplement Raypierre’s piece with some additional information.
1) Wired says “A tree absorbs roughly 1,500 pounds of CO2 in its first 55 years. After that, its growth slows, and it takes in less carbon.” The idea that all trees suddenly slow in growth after age 55 is ridiculous. There are myriad variables that control tree growth including species, climate, soil conditions, land-use history, etc. Many trees, including the dominant tree species in the Pacific Northwest where the northern spotted owl lives–Douglas Fir–do not slow in growth until they are considerable older than 55. (See Curtis 1994 USDA http://www.treesearch.fs.fed.us/pubs/20584)
2) Wired goes on to say that “Left untouched, [a tree] ultimately rots or burns and all that CO2 gets released.” This statement shows a complete lack of understanding of forest carbon dynamics. When a tree decomposes, some of the organic matter is incorporated into soil. This is why older forests contain significantly more carbon in their soils than younger forests do. (See Zhou et al 2006 Science http://www.sciencemag.org/cgi/content/abstract/314/5804/1417)
3)The only pool of carbon mentioned in by Wired is that of trees. But forest carbon sequestration is much more complicated than the growth of individual trees—live tree biomass is but one carbon pool in a forest. Other carbon pools include dead organic matter and soil, which together usually comprise the majority of a forest’s carbon. The amount of carbon a forest stores in live biomass, soils and dead organic matter all increase with forest age in temperate forests, like those in the United States, and tropical forests. In boreal forests, like those in Canada and other cold climates, older forests continue to sequester massive amounts of carbon in their soils as they age (See Pregitzer and Euskirchen 2004 Glob.Ch Bio. http://www.ingentaconnect.com/content/bsc/gcb/2004/00000010/00000012/art00010).
4) As Raypierre pointed out, the Canadian study mentioned in the Wired article is for managed Canadian forests only. The forests of Canada are boreal, which have different carbon sequestration cycles than forests in the United States, which are temperate forests. Therefore, its findings are not particularly relevant to forest management in the United States. Second, it is ironic that Wired would cite this study because the main reason why Canada’s managed forests may be a negligible carbon sink in the near future is because of increased risk of fire and pest outbreaks. These risks could very well increase if older forests in the United States were converted to tree farms. Tree farms tend to be densely planted and have little genetic diversity, which increases the chance of fire and pest outbreaks for a variety of reasons including a) increased risk of drought stress. Drought stress increases the chance that a forest will burn, the intensity of the burn and increases the likelihood that pests will overrun the forest. b) Older forests contain more diversity in plant an animal, and often contain many insectivorous species such as spiders that control pest outbreaks. c) Older forests have trees of different ages, heights, genetic diversity and spacing, which helps prevent crown fires from spreading. (See for ex. Odion et al. 2004 Cons. Bio. http://www.blackwell-synergy.com/doi/abs/10.1111/j.1523-1739.2004.00493.x?journalCode=cbi and Coyle et al 2005 Ann. Rev. Ent. http://www.treesearch.fs.fed.us/pubs/8380)
Perhaps the worst aspect of the Wired article is that it insinuates that there is a scientific basis for its conclusions by linking to scientific studies. None of the studies Wired links to or mentions support the idea that logging old-growth forests could fight climate change. For example, the study linked by the words “Clear the oldest trees” does not mention older forests, let alone advocate logging them. The studies that have addressed the issue (none of which are linked to by Wired) all conclude that logging older forests would be a poor strategy to fight global warming, even when wood products and replanting are taken into account. Furthermore, Wired does not mention that many recent scientific studies that utilize new technology allowing the measurement of forest carbon fluxes. These studies show that older forests tend to be carbon sinks and that the only forests in the United States that are consistently net sources of carbon to the atmosphere are young forests regenerating after a major disturbance like a clearcut or stand-replacing fire. Here is just a sample of the studies showing that older forests in the United States are usually carbon sinks and that young forests can be sources of carbon to the atmosphere for decades.
Valentini, R., et al. 2000. Respiration as the main determinant of carbon balance in European forests. Nature 404, 861–865.
Law, B.E. et al. 2002 Environmental controls over carbon dioxide and water vapor exchange of terrestrial vegetation. Agricultural and Forest Meteorology. 113:97-120.
Law, B.E., O.J. Sun, J. Campbell, S. Van Tuyl, and P.E. Thornton. 2003. Changes in carbon storage and fluxes in a chronosequence of ponderosa pine. Global Change Biology 9:510-524.
So let me see. We own a Toyota Corolla, which is almost 8 years old. It gets 30-35 mpg on the road and perhaps 25 mgp in the kind of city driving we do. Because of age, arthritis, and other issues, we use the car in circumstances where previously we might have used public transportation, but we still don’t drive all that much. I do use I-Go, but it is often difficult to find a car within easy walking distance—somewhat shorter than it once once was before spinal steonosis set in—and even then I may end up with a Honda Element. We shop using Peapod. I don’t know if that saves energy or not—one delivery van dropping groceries off at many locations as opposed to many individual trips—but it sure saves wear and tear on arthritic bodies. Other food shopping is done by walking to local markets, and other shopping is done wherever possible in the local area. I do bicyle for exercise, but I would need a more practical bike to use for shopping, something I haven’t got yet because of our condo’s rules about storage.
Given all that, should we replace our Corolla with a Prius? It only has about 50,000 miles on it, so it can go quite a bit longer. So far, I’ve reasoned that the increase in gas mileage would not be large enough to compensate for the cost. If your analysis is correct, we should first drive the Corolla into the ground, until it ends up being only fit for junk, or until neither or us is able to drive.
Any comments?
[Response: It’s easy to compute the impact of a decision like this on personal carbon footprint, but the more relevant decision factor is impact of the decision on the long-term carbon emissions of the vehicle fleet as a whole. The complexity there is that the result depends a lot on what other people do. For example, if everybody decides to buy a Prius, then there will be so many used cars dumped on the market that a lot would be junked, and there would be wastage in that. On the other hand, if your used Corolla goes to somebody who was driving an inefficient old Buick Electra that then gets junked, your decision will ultimately lead to reduction in fleet emissions, as long as your Prius stays on the road long enough (in your hands or others who get it as a used car) to pay back the carbon cost of manufacturing. It’s quite possible that buying a new Prius would reduce the net long term fleet emissions, but then again you’d have to weigh the personal money cost of doing this against other things you could spend your money on that would potentially reduce carbon emissions more — e.g. donating to some local church to help them pay for a replacement air conditioner. –raypierre]
Nuts to Wired. They could have pointed out something useful, instead, like replacing eroding plowed fields of corn and soy with perennial woody agriculture. An old friend wrote this long ago. I’ve never seen it referenced. It should be:
http://books.google.com/books?id=TOu4GmExgGAC&printsec=titlepage&vq=woody+ag&dq=%22Philip+A.+Rutter%22&lr=&source=gbs_toc_s&cad=1#PPA208,M1
re: # 49
“What does a nuclear pile tend uncontrollably to do?”
It depends significantly on the specific ‘nuclear’ materials (and non-nuclear materials if present) that comprise the ‘pile’ and the configuration in which these are arranged.
The question cannot be answered without additional specific information.
A factor that could come into play by the use of ACs and not in the use of space heating is a possible slight(or maybe not so slight?) feedback effect.
As the average global temperature increases it’s reasonable to expect greater use of air conditioners, and if fossil fuels are used as an energy source,then this will lead to more global warming and more use of ACs and so on. I guess “Wired” didn’t take this into consideration, either.
Wired magazine brings up an interesting point that it requires more energy to build a Prius than a Hummer, this raises further questions:
1. Over the useful lifetime of the car, how much more energy will a Hummer expend per miles driven versus a Prius? At what point does driving a Hummer use more energy than building a Prius?
2. Given that the Prius batteries must during the lifetime of the car be replaced:
http://townhall-talk.edmunds.com/direct/view/.ef2b471/0
how much energy is used in the recycling process?
[Response: It doesn’t take more energy to build a Prius than a Hummer. It only takes more energy per pound, which is a very different thing. The links that other commenters have given will take you to a full lifecycle analysis of hybrids. Assuming both the Prius and the Hummer are driven to the end of their natural lifetime, the Hummer is a dead loser. The more relevant question is lifecycle carbon emission of a hybrid vs. an equivalent-sized efficient conventional gasoline car, or perhaps a diesel. –raypierre]
Leonard Evens wrote: “… I do bicycle for exercise, but I would need a more practical bike to use for shopping …”
How about a four-wheel, two-seat, hybrid electric-pedal powered bike?
Maybe this is the European in me but instead of trying to figure out the most carbon footprint-friendly car, why don’t we all car pool more and use public transportation more often? It’s certainly cheaper. And maybe makes the case for a more urban lifestyle.
“What do you do when you get to the point where you have to take off the tee-shirt and shorts and it’s still too hot? Wasn’t there a Shel Silverstein poem on that theme? Anybody remember it? –raypierre”
Wasn’t it Bob Dylan?
“The answer, my friend, is blowing in the wind”..?
;-)
Thank you for explaining today’s xkcd to me.
Unfortunately we still use mainly coal here in Denmark. We do have a slightly better overall efficiency (I believe) by piping the cooling water from the plant around the city for heating. Though … that means heating is so cheap that in many homes it isn’t profitable to improve insulation. (Not that I’ve noticed it – my bill seems be going up and up – I bet it’s my neighbours running around in the nude all year. Damn communal billing.)
While the calculations at “Wired” are naïve, the calculations here are, shall we say, semi-naïve. Let me just do some quick numbers for residential use.
The A/C load is roughly 13% of the spacing heating load for the country. Convert that to energy at the generator and it is still bit less than 50%. Now just looking at the average rates of the A/C load per population-weight-cooling-degree-day versus the space heating load per population-weight-heating-degree-day, the A/C is about 35%. There are more CDDs, population weighted, than HDDs. (This should be done on an energy, HVAC-consumption weighted basis, but I have seen those numbers and I am not going to calculate them for a blog comment.) Then roughly a one degree warming adds 180 to the CDD total for the year and removes 180 from the HDD total. This would give us a serious energy savings… Except that the demand for heating energy is roughly linear in temperature while that for cooling energy has a positive second derivative. Now for the Northeast (NEPOOL: where I have a good regional load and temperature dataset) this is roughly a factor of 2 at 25 CDD (90 degrees F). But over all the cooling days for the 25 year period, the factor is merely 1.02. Thus over the year the quadratic effect isn’t going to contribute much.
Finally, with regard to coal versus natural gas/fuel oil/LPG, coal burning releases about 60-75% more CO2 per BTu than natural gas, a bit less for LPG, and about 25% for oil. And with the increased natural gas prices and proclivities of utilities planners, coal-fired units are the choice for new plants. However, the incremental cooling load will make the load shape more peaked, and for increases in the pure summer peak, simple-cycle gas-turbines are the new plant of choice. Thus, while it is true that an increase in temperature with the concomitant increase in cooling load will lead to more coal plants, regulations allowing, it is also true that well less than 50% of that incremental cooling load will be supplied by coal fired units. Without a nation-wide production cost simulation of the load increase, it is hard to refine that number much.
Putting that altogether, a uniform increase in the temperature of one degree F (equal increases in CDDs as decreases in HDDs) is probably going to cause a small decrease in the carbon emissions for US residential consumers.
Now that is only the residential sector. The industrial sector HVAC is probably similar, but it is not that important because the HVAC (but not the process heat) part of the industrial energy load is much smaller. However, the commercial sector is about the same size, and the publicly available data is a bit ambiguous. Thus, there could be a bigger (in absolute) size effect there in the opposite direction. But whatever the effect is, if you want to calculate it you need for drop the engineering calculations and look at the actual demands for energy for A/C or space heating.
In comment 49 Lee A. Arnold included,
Four concrete cubes, each (76 m)^3 … yes, the size seems right. Most who are reading this probably have seen 20-storey apartment buildings about that tall, but not extended that far along two horizontal axes, and not solid.
Large pieces of concrete don’t hold together all by themselves; they need steel tension cables to keep the concrete, which has essentially no tensile strength of its own, in compression. Since steel is denser than concrete, this would reduce the size a little.
OK, 76 of these concrete cubes, rising in the day until their bottom surfaces are, as Arnold says, 18 times 15 feet, 45 m, off the ground. Yes, that could work.
The largest existing solar power stations have a much smaller capacity than 1 gigawatt-year per year, so they might get away with just one or two of these hyperhoists and ultracubes.
So the hoist that lifts this block of concrete, as tall as a 20-storey apartment tower and as heavy, I guess, as a small cityful of them … so the hoist that lifts it through most of its own height, and is able to let it down on command, will have neither an uncommanded nor a wrongly commanded letdown, “no matter how long”, and this is guaranteed by building codes.
I think I understand.
In comment 56 Dan Hughes said,
But it can: beta decay. Turning a fission reactor on at 1 watt and keeping it there for 1 hour, then stopping it, causes 0.0061 watt-hours of uncontrollable delayed energy release in the following hour, 0.0018 watt-hours in the second post-shutdown hour. These numbers are given by the integral of the Untermyer and Weills equation that is given in http://www.rertr.anl.gov/FRRSNF/TM26REV1.PDF and said to originate in USAEC Report ANL-4790, 1952.
Denmark is the world leader in offshore wind, right?
http://www.renewableenergyworld.com/rea/news/infocus/story?id=46749
Whilst a nuclear reactor emits no CO2 in the production of electricity, the mining and milling of the fuel certainly does. Not to mention the construction and eventual decommisioning of the plant. The burning of fossil fuel is a large part of the nuclear cycle that we conveniently ignore.
If the grade of ore was consistently high then this might not be a problem. But most of the Earth’s high quality ore has already been used up. And when you’re forced to mine and mill the lower grades, the CO2 balance goes into debit. That is, more CO2 is emitted than would be the case if you just burnt the fossil fuel conventionally to generate electricity.
Storm van Leeuwin and Smith claim that if the world hypothetically went totally nuclear tomorrow, the rich ores would be consumed in less than a decade, after which the CO2 benefit of nuclear energy would be gone.
Here’s an article from the Australian Government’s CSIRO Sustainability Network Newsletter. “Nuclear Energy: We don’t need it”
http://www.bml.csiro.au/susnetnl/netwl53E.pdf
John, interesting CSIRO piece. I’ve copied over the footnotes from it, for the basic points you mention:
http://www.naturaledgeproject.net/NAON1.aspx; citation on page 37
http://www.oprit.rug.nl/deenen/ “Nuclear Power: the Energy Balance”
http://www.yesmagazine.org/article.asp?ID=1064 (Burns) http://www.yesmagazine.org/article.asp?ID=1065 (Lovelock)
No one ever built a breeder reactor that didn’t require reprocessing spent fuel, as far as I know. Canada’s thorium/deuterium design seems to be history.
Re Denmark: in 2006, it generated 54% of its electricity from coal, 21% from natural gas, 13% from wind (down from 18% in 2005), and imported a tad.
It would be easier to accept Storm van Leeuwin and Smith if they had ever submitted their work to peer review. Their results counter all studies I’ve ever seen that have been peer reviewed, which show nuclear power over its life cycle producing as much GHG/kWh as wind, less than solar, and that we essentially have more uranium + thorium than we have coal.
The CSIRO author cites them. Meanwhile, pretty much everyone making climate change plans is assuming that the peer-review analysis holds and that nuclear power is an important low-GHG source.
Of much more interest is the recent IEA report, Energy Technology Perspectives. IEA estimates that wind could be almost as important as nuclear between now and 2050, and that we will need 32 GW in new nuclear power every year between now and 2050.
IEA argues that we need to remake the world economy, unprecedented levels of cooperation, etc, etc, etc to get a 50% reduction by 2050. A 50% reduction brings in a best-guess reduction to 400 ppm. Not enough.
(Had to skip over some comments, sorry for repeating if this is a repeat:) So the COP of a sample air conditioner is 2.92?
The ideal COP of a heat pump (no production of entropy) can be found from these equations:
Qc + W = Qh
Qc/Tc = Qh/Th
Where
Qh is heat flow in (out) at temperature Th (the hot end),
Qc is the heat flow out (in) at temperature Tc (the cold end),
W is the work (usefual energy) produced (consumed).
Let DT be Th-Tc
Solving for W and Qh:
W = (1 – Tc/Th) Qh = Qh (Th-Tc)/Th = Qh DT/Th
Solving for W and Qc:
W = Qc (Th/Tc – 1) = Qc (Th-Tc)/Tc = Qc DT/Tc
For an ideal heat engine, relative to the heat source, the efficiency is DT/Th. If you wanted to run a heat engine off of a limited supply of cold in a hot environment, you might care more about the efficiency relative to the heat sink, DT/Tc.
For an ideal heat pump, the Coefficient of Performance (COP) for the hot end is Th/DT. The COP for the cold end (of interest for air conditioners) is Tc/DT.
For cooling or heating a home, Tc and Th are relatively close so the COP of ideal heat pumps for heating and cooling are nearly the same.
—-
But the ideal COP for, say, 20 deg C (36 deg F) temperature difference with the Tc ~ Th ~ 300 K is going to be ~ 15. I’m not that familiar with the actual practicalities involved in the technology, and wouldn’t expect to get very close to ideal COP values, but 2.92 seems rather pathetic. (Although only a bit more pathetic than the ~ 30 % efficiency of coal power plants, considering that the temperatures involved should allow for much higher efficiencies.)
Also, it occurs to me that it is at least possible (if not yet practical?) to roughly double the COP of a device if, instead of a single heat pump, one has several with a working fluid running through at progressively different temperatures from intake temperature to goal temperature. (PS two fluids running past each other in opposite directions with progressive warming or cooling makes a heat exchanger).
In addition to the role of internally generated waste heat (which, for lighting, can be reduced with daylighting (sunlight is ~ half visible light, and if the windows could reflect IR and UV, or convert them to electricity, well, then… :) ) and high-albedo interiors), there is another assymetry between heating and cooling: when the dewpoint is high, the amount of heat that an air conditioner has to pump for a given set of Tc and Th and mass of air can increase because of the latent heat of condensing water. (For winter humidity needs, their is perspiration (not much), cooking of pasta, and showers, etc.)
Having a home with greater cooling needs than heating needs might tend to be ‘greener’ because more solar power is generally available in summer than winter; of course, this depends on other available energy sources, energy storage, and individual preferences, etc… And with that, comment 6 is on to something.
Instead of breeder reactors, we should be building breeder solar PV manufacturing facilities:
Yes, this revolutionary new concept… wait – what’s that date?
The solar breeder, Lindmayer, J., Photovoltaic Solar Energy Conference, Luxembourg, September 27-30, 1977
Re:#60 “…… why don’t we all car pool more and use public transportation more often?….”
Because that would ruin Will Rogers’s prediction that the U.S. would be the first country in the world to drive itself to the poorhouse in an automobile.
Actually the real answer to this commonsense approach of conservation and efficiency lies partly in the insidiousness of the oil industry and its public relations propaganda,with the help of some(not all) of the mainstream media who insist on taking a so called “balanced” stance on AGW,by presenting the “other side”. Which, to me, is like looking at the other side’s view on a Heliocentric solar system.
I would question the “100%” efficiency rating for the gas furnace,the real world condition in combustion testing reveals more like 85-89% combustion efficiency, to have a even near 100% efficiency, the gas would have to burn at stoichiometric air fuel ratios, and no burner is that good, they all need to have excess air due to design limitations. Keep in mind all condensing furnaces have 2 fan electric fan motors, and one with a pre/post purge function that will remove heat, so you have 2 energy inputs not just a singular source such as on the a/c to calculate your “carbon footprint”.
Re 68
Actually, water can absorb IR and UV; maybe solar water heaters could double as skylights.
Re 68
… of course, if you value white Christmasses, maple syrup, and don’t want to worry about killer bees, black widow spiders, or dengue fever, moving to sunnier warmer climates might not be the right choice. On the other hand, you’d be closer to the oranges and cacao trees (although the processessing of that chocolate might take awhile to follow you?). Etc… PS written near 45 deg Lat.
When I wrote Re 68, I was refering to my own comment (Re 69)
19. It is very unfortunate that our present government is so totally opposed to your nuclear ambitions (I am assuming you are Iranian, although similar logic applies to the rest of the Arab world). It is clear that with the current administration in Washington no change is likely. There have been proposed compromises, such as letting foreigners (Russia mainly) handle the reprocessing, which aside from national pride, and a potential, but low probably fear that the fuel supply could be cut off, should be sufficient (at least given a change of leadership in Washington). Another avenue that I think would work spectacularly well (if National pride is the main issue), would be to develop a Thorium based Nuclear cycle. This would be an important contribution to the worlds energy future, as well as being a way to have control over your fuel cycle, and alleviate proliferation concerns.
Now, back o the Prius. It is incorrect to assign the energy cost of the batteery to the lifecycle energy cost, as the batteries will be recycled (the materials are too valuable not to). Also Toyota is currently warranting the batteries for 150,000 miles (and confident of typical lifetimes of at least 200,000). The only real fly in the ointment is hybrid production capability. Currently hybrid battery production capability is in short supply. I expect the hybrid market will be production limited for at least the next five years. That implies that the most effective usage requires selfselection of buyers (i.e. only those who drive a lot should buy a hybrid). A Prius (and probably some other serial hybrids), have additional potential savings. As battery prices decrease, and gasoline prices increase, at some point it will be worthwhile to upgrade existing Priuses to plugins -all that will be required is a charger, better battery capacity, and modified control software.
Re #64, G.R.L Cowan, I misunderstood your objection! From your example I thought you were talking about a human tragedy adjacent to the site, such as from a dam water release without warning, or a nuclear reactor explosion. I had not considered that it will be impossible to design mechanical safety features to prevent a concrete block from sliding down inside a silo! “He must be talking about the collapse of the whole building,” I thought, hence, “Follow the building codes!”
I’ve been trying to think of a simpler way to highlight the basic issue in the decision of whether you help reduce carbon emissions more by keeping your car or selling it off and buying a hybrid (or other new car with better gas mileage). Let’s call the new car a Prius, for the sake of argument.
Assuming the Prius to have lower lifetime carbon emissions (including manufacturing) than the fleet average, then the best thing for long term carbon emissions is to turn the fleet over into Prius’s. That can’t happen if NOBODY buys a new Prius. I.e. the situation where everybody buys a used car and feels virtuous does not get you where you want to go in terms of carbon emissions. Another way of putting it is that if everybody bought used cars, there would be no new cars entering the fleet, and eventually the stock of used cars would be exhausted, as they age and die. That mean that somebody has to buy new cars, and those new cars ought to be Prius’s.
That means that somebody who buys the new Prius is performing a service by injecting an efficient car into the fleet. The question then comes down to what is the ideal rate of injecting Prius’s into the fleet? Clearly you can overdo it since if everybody goes out and buys a new Prius, a lot of fairly efficient and usable used cars will get scrapped before their time.
So, any takers on how to figure the optimum rate at which Prius’s should be entering the fleet? Once you figure the best number, you can figure out WHO should be the ones to actually buy those cars — the WHO meaning WHO in terms of what kind of car they already own. Perhaps you’d then want to add a dose of reality by constraining the WHO question by personal financial resources.
I think this is an interesting optimization problem, though perhaps academic if the supply of hybrids is going to be limited by manufacturing capability for an extended period of time.
Re #4: Sure, hundreds of thousands of homes in Sweden are heated by heat pumps already, taking heat from the groundwater by drilling a well about 300 ft deep and circulating a heat medium down that well. You get at least 3W of heat for every W of electricity that way, so it is very, very profitable for the houseowner, another example of that “green” does not mean “expensive”. Sweden today uses only 50% of the oil compared to 1975 – and we have not had to go back to the stone age to achieve that.
Raypierre, thanks for your response to my #44 – I totally agree with your view that we need more not less natural forest.
The reason I thought you meant “old tree” rather than “young tree” was that it seems to me the best way to look at this sort of problem is to ignore for the moment processes that operate on longer timescales than decades to centuries, and consider that a given area of land has a certain capacity to store carbon removed from the atmosphere by photosynthesis. If the carbon is stored it is not in the atmosphere to contribute to global warming. Our aim should be to implement policies to maximise the amount of this carbon storage capacity that is used, on average over time. My thoughts on these lines for biofuels (i.e. why they’re a really bad idea) are available at: http://unchartedterritory.wordpress.com/2008/06/16/the-biofuel-papers/
WIRED’s provocative proposal to sell a few extra copies is to suggest that removing old trees to allow more vigorous growth will keep more carbon out of the atmosphere than just leaving the forest alone. This is not the case. A hectare of forest might hold 150 tonnes of carbon in the form of trees. If we remove this and allow new growth then we have to add two curves: the carbon uptake of the young trees and the loss of carbon to the atmosphere of the trees that have been taken out. An example of the carbon uptake over 100 years appears in: http://www.eccm.uk.com/httpdocs/pdfs/TD11.pdf
The ECCM paper shows that it takes about 10 years before the new trees take up carbon at anywhere near the most rapid rate (of around 3.5 tonnes/hectare/year in their example) and nearly 50 years before it stores even half the 150 tonnes of carbon that has been removed. The question is whether the rate of loss of carbon from the extracted trees exceeds the rate of uptake of the new trees. It seems to me that decay is almost bound to exceed growth for most of the (say) 100 year lifetime of the new trees. Even if the old trees are used entirely for “furniture and houses” (to quote WIRED) there will be a large proportion wasted immediately and then a slow loss over time. Very likely much less than 50% of the carbon will stay out of the atmosphere for 50 years, for example.
Towards the end of the 100 year lifetime of the new trees there may be a small gain represented by the small percentage of wood surviving for a century. But then we propose to repeat the process and once more go into carbon deficit. To ensure a steady harvest of wood the forestry industry keeps various plantations at different stages. We therefore need to take an average over the lifetime of the trees – 100 years in my example – of the total carbon kept out of the atmosphere per hectare as a result of the forestry process. This average, I suggest, will be significantly less than the amount of carbon stored in the original natural forest.
There are other arguments in favour of leaving as much land as natural forest rather than managed forest. In particular, the carbon stored in natural forest is significantly higher than the peak amount stored in a managed forest, for various reasons. In other words we may destroy a natural forest storing 150 tonnes C/hect and replace it with a plantation that at peak stores 100 tC/hect, and most of the time much less than this. To compensate we would have to preserve an awful lot of antique furniture! Valid points are also made in #51 and #53.
#50 alludes to the release of carbon as the planet warms. If we ignore the slow process of long-term storage of carbon in soils, we can consider forests to be in equilibrium, like any other chemical process. Raising the temperature would be expected to move the reaction towards carbon release, in agreement with what is observed (in high latitudes this may be outweighed by increased growth rates) – a carbon-cycle feedback.
But increasing atmospheric CO2 tends to move the reaction towards carbon uptake (that is an increasing amount of biomass in a given forest area) – this is the “CO2 fertilisation effect” which is currently keeping the rate of increase of atmospheric CO2 to about 2ppm/year rather than around 2.5ppm/year which the discussion in AR4 implies it would be otherwise. As we continue to destroy the world’s forests and cultivate the land instead, we progressively prevent the CO2 fertilisation effect from operating.
#78, I beleive that company cars would be a good way to progress. Get the critical mass for economic production from offering them as company fleet cars. However lots of motorway miles in a Prius might not be that good an idea as they are not that efficient on long haul journeys as they use the petrol engine and people tend to travel fast on motorways reducing efficiency further.
It needs to be a way of getting people doing lots of urban short journeys (mums and stuff on the school and shopping run) to obtain them primarily.
Re Prius etc. I think the private automobile as a form of mass transportation is the wrong paradigm. It will not work for the majority of the 6.5 billion people currently on the planet. It is not sustainable regardless of the energy source used to power it. I think XKCD has the right take on this topic. http://xkcd.com/437/
Re 79:
I was looking at the amount of energy (ignoring all efficiency and conversion losses, etc) in 1,000 gallons of water at the daily high (about 100F these days) and the overnight low (about 75F these days) and it came out to be about as much electricity as I buy from the grid in 3 days. Since solar collectors have outlet temperatures in excess of the daily high, I’m thinking I’m aiming my sights a bit low — and 1,000 gallons isn’t that much, perhaps 130 cubic feet, or less than 6′ on a side.
Because public transportation is often crowded, uncomfortable, unreliable, and slow even when it does work. I’m a long-time bus rider and I’ve ridden buses and trains in many cities; I know. There’s also the fact that with public transportation, you can’t plan the route or make side-trips. Americans like cars because they like having some control over their transportation. Cars aren’t going to go away any time soon.
Let’s assume, as raypierre says, that you need to emit more CO2 to cool a house by 1ºC than to warm it by 1ºC. There is still another important factor. The use of the air conditioner will directly cause only a little warming (the machine warms a bit because it is not 100% efficient). The heating system on the other hand causes warming directly. So the question would be: will the extra CO2 emitted to cool the house be as important for global warming as the actual fact of warming the house in winter? Therefore, if we are going to reduce our welfare, is it better to be 1ºC colder in winter or 1ºC hotter in the summer? How do we “heat” less the planet, with the CO2 emission or with the direct warming?
re: # 79
In 2005 about 92% of Sweden’s electricity was based on hydro and nuclear, 8% fossil. From.
In response to closure of a 2-unit nuclear plant,
And
re: #64
By stating ‘fission reactor’ you have implicitly specified both the composition and geometrical configuration of the materials that comprise the ‘nuclear pile’ and the physical boundary conditions. You have additionally specified some the previous history of he state of the pile and the initial conditions for the ‘uncontrollably to do’ aspects.
#81: I agree. Figuring out whether to buy a Prius or your next Corolla is a problem for a privileged few in the world (though many of this privileged few may be living in the US). Lots of people in the world at large don’t own cars and have to rely on public transportation. For many people in Europe and the Middle East, owning a car is not the problem but driving one is because gas costs about 4 times more there than it does here in the US.
I think the real solution lies in making public transportation more available and comfortable in the US. I think solving problems like how Earth-friendly is it to own a Prius may be considered a little lofty when even the Prius still produces greenhouse gases (though less) and a lot of people really don’t (can’t) own cars because they don’t have the financial resources to make the choice between a Prius and another car.
Plus Prius or not, it seems some are still considering driving the private vehicle when that, among other things, is what got us in this climate mess to begin with, isn’t it?
But soon the price of gas is going to become so unaffordable that this discussion is going to be moot and we all will have to learn to ride the bus or our bikes if our spirits are so independent :) Let’s hope we don’t do irreversible damage to our planet by then, if we haven’t already.
Furthermore, how much of the energy that I transfer to the outside of the house becomes energy lost to space because of increased radiation of the outside of the house? A black body with one half at 22 degrees and another half at 20 degrees radiates more energy than a black body with uniform 21 degrees temperature, as radiation changes with T^4. Could an actual loss of energy for the Earth system be a result of the use of my air conditioner, I mean, locally, independently of the energy used to “move” the heat?
For anyone interested in geothermal heat systems, the Canadian government has a nice primer:
An Introduction to Residential Earth Energy Systems
http://www.canren.gc.ca/prod_serv/index.asp?CaId=193&PgId=1190
Some musings on geothermal (aka earth energy) heating/cooling systems. One could conceivably do even better than using the 55F deep ground as a heat source/sink by storing the winter cold and summer heat.
Suppose you have a shed with a very large tank of full of water. The base of the tank has antifreeze filled pipes leading to a heat pump in the basement of your house.
In winter, you open the doors to shed, allowing cold air to eventually freeze it into a solid block of ice. Then you wrap the ice block in insulation and seal up the shed to store all that coolth for use later in the year. When you need air conditioning in summer, you run your heat pump using the block of ice (eventually very cool water) or the deep ground as the sink, whichever is cooler.
In another shed, you have a well-insulated tank with water that you heat up in summer using a rooftop solar water heater. In winter, your heatpump uses that tank as the heat source (or the deep ground, whichever is warmer).
#84 [BPL] “Because public transportation is often crowded, uncomfortable, unreliable, and slow even when it does work.”
Not when it’s properly funded and run, as in much of Europe (sadly, not the UK).
“Americans like cars because they like having some control over their transportation. Cars aren’t going to go away any time soon.”
Similarly, Americans (and western Europeans, Japanese, etc.) like using far more than their fair share of the world’s resources, including its ability to absorb pollution. If we can’t be persuaded to moderate our greed considerably, everyone’s stuffed.
There really are a wide variety of options for making both large buildings and small residences energy-independent. Not only is this good for climate, it is also a real economic necessity in an era of steadily increasing fuel prices.
http://www.usatoday.com/money/industries/energy/2008-06-15-power-prices-rising_N.htm
The two large-scale solutions to that are concentrated solar power plants and wind turbine farms. The small-scale solutions are energy-independent homes that also use solar and wind inputs.
For a nice design for a home-scale wind turbine system, see:
http://www.treehugger.com/files/2008/06/wind-power-urban-architectural-microturbines.php
All in all, what is needed is a new architectural mentality that places energy efficiency and conservation at the center, and designs the structure around that. As you can see, many people are doing this already.
In comment 87 Dan Hughes included,
“Nuclear pile” once, I guess up to about 1955, meant fission reactor. I don’t think it ever meant anything else.
Arnold asked what uncontrollable tendencies the things so called had; I gave the complete list for typical ones. They don’t have any bad habits in re control of fission itself, witness the natural Oklo reactors’ remains’ appearance of having burned evenly for millennia, and witness also the good behaviour of the San Francisco‘s engine when that boat stove in its front end on a seamount.
The elephant in the room that would need to be removed is the ever increasing human population…unless we limit our propagation, the earth’s resources will become depleted and no longer sustain us in the multiple billions. As Walt Kelly’s Pogo said “We have met the enemy and he is us!”.
Comment 85
Logically, I may have a problem with the idea
expressed, it must be my misunderstanding. My
thought is to that impart 1 Deg of change to a slug of
atmosphere whether higher or lower then the ambient
temperature, should not differ. Only the energy
conversion system imparting the temperature change is
important.
Systemically, direct heating endothermic output of the
complete combustion of methane (Natural Gas) to H2O
and CO then CO to CO2 as compared to the indothermic
biologic processes are not much higher then any other
process then it misses it by a small margin.
(Probably only Solar Cell Hydrolysis and combustion of
the by products are likely higher.)
On the other hand, it appears either Air-Air or
Water-Air Heat Pump systems as the most popular /
appropriate solution in the highly humid regions where
the tropical temperatures from Global Warming are most
likely to make uninhabitable, if what the science
tells us is true. For cooling, either of these
systems require a conversion of combustion (chemical
energy) to steam (thermal energy) from steam to a
turbine (mechanical energy) from a turbine to a
dynamo (electrical energy), then we have the
resistance of distribution (thermal energy leakage)
and finally the conversion from electrical energy to
mechanical energy to power the exchange of thermal
energy.
There is yet a different system with much fewer steps
though it still would require combustion (chemical
energy) to achieve thermal energy exchange. By using
the Absorptive/Evaporative refrigeration process it
would need to provide a high thermal input to drive
the thermal energy exchange. In either case cooling
has more conversion steps then direct heating.
What I think is being suggested is that the heat per
unit of air being passed through the heat exchanger is
lower for cooling then it is for heating and that has
more to do with the initial temperature of the heat
exchanger inputs. However, if a furnace was designed
that recirculated the combustion gases until they
reached about 30 to 40 degrees above ambient before
reigniting the burner I think the argument presented
could be easily countered. A recirculation furnace
with a pulsed burner would be much greater in
efficiency systematically.
Hence, a good reason for many to look toward Gas
Packs, (Air-Air Heat Pump Gas Furnace combinations)
for their HVAC needs. If it were not for the economic
reasons required to improve the furnace portion, the
idea of a pulsed burner and combustion chamber
recirculation control system would have been developed
years ago. (Keeping in mind that the biggest concern
is the possibility of heat exchanger combustion gases
leaking into the buildings air return, resulting in
possible CO poisoning.) Which could be remedied by a
internal CO detector which would shutdown the Gas
Furnace and activate the Emergency Electrical heating
strip while annoying the building manager/homeowner
with one of those aggravating warning alarms.
As to comment 89, the higher heat energy at the
surface is not going to get through the green house
gases any faster then lower temperatures, if I
understand the science correctly. Hence, 1 Deg. more
may not do much more then warm the middle troposphere
a little more as the surface region of re-emission
into space has not changed. Now if the added heat
would raise the region being heated so that the
surface area increased rather then the temperature
that would be different. Though we probably would not
be having this discussion if that were true…
So, did I explain my concern and address things
correctly or was the intent something different?
Cheers!
Dave Cooke
I understand that many people consider solar power one solution to greenhouse gas emissions.
However, has anybody ever considered that to purify the silicon for the typical PV panel requires significant electrical energy that comes for the most part from coal fired plants?
In other words, PV solar power is not without it’s carbon foot print.
Secular Alarmist commented
————————————————————–
Leonard Evens wrote: “… I do bicycle for exercise, but I would need a more practical bike to use for shopping …”
How about a four-wheel, two-seat, hybrid electric-pedal powered bike?
——————————————————-
I have considered various alternatives, including tricycles. Some of these would be practical all weather vehicles for short trips. I am not yet in such bad shape that I need electric power. The problem is where to put it. I only raise that issue because it is likely to be a problem for any apartment dweller with limited storage space. In our case, we do have some alternatives, but they could be costly, but most would have even fewer alternatives than we do. Of course, if you live in a detatched house, this won’t be a problem, but more and more of us live in apartments, something that will be more common as the disadvantages of dispersed housing become more apparent.
In comment 97 Andrew says,
Depending where it is made, the electricity might or might not have a large fossil fuel component.
However, although solar PV electricity is very expensive, it is not so expensive as to suggest conventional energy invested exceeds output. Also, direct comparison of electricity in and electricity out yields, IIRC, a payback time of about two years.
Storage to make intermittent PV input into continuous output, such as a silicon purifier might need, would waste some of the intermittent input and extend this payback time to ~3 years, and some of the PV cells the factory would make would spend their whole lives paying off the electricity debt incurred in the factory’s construction; but this would be small compared to the energy it would use in its working lifetime. So net energy should start coming out within five years.
CSP is quicker.
Re #96 Dave,
My doubt in 85 is, OK, we use more energy in cooling than in warming, but do we actually WARM more by cooling than by warming? When we try to warm, all of the energy used causes warming, directly (temperature increase) and indirectly (GHG emissions). When we try to cool, however, only some of the energy will cause warming.
As for what I said in 89, I’m not sure you understood it. The energy radiated by a body depends on its surface temperature, but it is by an integral calculation of the temperature of the surface, not by just taking the average of it. Again, if I have a black body which is 22 degrees and another one which is 20 degrees, the total emissions from both will be higher than if each of them was 21 degrees. And I don’t need to change their sizes or any other properties than their temperatures. If I manage to transfer energy from one to the other so that one gets a higher temperature while maintaining the average of the 2, the result is a faster energy loss from the overall system due to energy radiation.
If the outside of my house is warmer, it emits more energy to the outer space. That principle is what will make the planet’s warming stop at some point: as we warm, we radiate more and in the end we will reach a new (hotter) equilibrium. I hope you are not trying to negate this.
[Response: It’s only the greenhouse gas emissions that are a significant warming factor. The warming due to direct thermal output of all human energy use is negligible on the global scale, though in dense environments it can contribute significantly on a local level, making the urban heat island effect worse. –raypierre]