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 Richard Wakefield @134: ” I’m getting one [ground-source geothermal system] put in my place, getting off NG. 10 verticle holes 100ft down. The system will cost about $25K, but at current prices pay back can be as low as 7-10 years. Priceless when NG supply drops.”
Indeed, and very good for you, Richard. We’re in an older urban neighborhood with ultra narrow lots and drives. Impossible to get a drill rig to the back, which leaves only the ultra small front yard. I’ve been discussing with our councilor the city starting a program to drill the wells along the city-owned boulevard as a form of public (or 3P) infrastructure, just like water and sewers, and charging homeowners to hook up. Not as far fetched as you might think as Toronto is already using a pioneering deep-water heating/cooling system for the downtown core. See: http://www.toronto.ca/environment/initiatives/cooling.htm
On the solar side, WISE, a citizen organized cooperative group here (see: http://wise.ourpower.ca/portals/wise/ourpower.aspx ), recently formed to promote and facilitate residential solar PV and thermal water heating installations by arranging group financing rates and bulk equipment purchase and installation contracts. In it’s first year WISE literally doubled the installed solar base in the city, although that may not be saying all that much given how little there was.
Henning #138:
If you are working in the car industry, you should have known better. Of course it’s all about marketing. People buy a certain car to advertise their personality and social status. The choice of car is for 95% an emotional one. So whether the Prius offers ‘bang for the buck’ in terms of features, safety, performance is not really important. It’s a billboard shouting: “Look at me how progressive and green I am!!”. Why do you ever think the SUV became such a resounding success?
Ok, now for some hard data. You claim there are a whole bunch of cars that emit the same or less CO2 than the Prius. I am curious which ones. Can you give a few examples (with figures)?
Why would prevention of terrorist attacks on nuclear power plants not be for the sake of the people working there? They would be most at risk.
There might be public discussion of the plants’ supposed attractiveness to terrorists by government officials because those officials would prefer natural gas. It costs 40 times more than uranium, so its royalties, by themselves, exceed the whole cost of uranium. People on public payrolls are partly funded by those royalties, so they have an incentive to try to raise fear of nuclear energy.
Those “other (severe) hazardous incidents” are driven by the uncontrollable beta-decay above discussed. So far they have harmed only equipment. In light of the fact that the alternative to nuclear risks is not no risk but alternative risks, this is, I think, very significant. I think you’ll find, if you look for them, cases where people who find it rewarding to promote fear of nuclear power act as if they did not fear it personally.
RE:150
Most nuclear power plants I am aware of in the US use a molten sodium heat exchanger, as direct heating of water within a nuclear pile may have a higher potential failure rate and could result in a higher chance of radioactive gas release. (There is an issue that the running a reactor at higher temperatures could result in the heat of the reaction causing the disassociation of hydrogen from oxygen (the coolant) and could lead to more or a higher incidence of releases of radioactive gases or potential disasters such as 3 Mile Is.) Must not be a problem for the Navy… (Though I often wonder if the heat signature trail can actually be minimized simply by running cool and cooling often…)
The biggest reason that throttling is not considered worthwhile in a nuclear system is the amount of time required to throttle down or up the pile. Though the reaction may terminate when you install the control rods the residual energy would take greater then 8 hours to cool hence the rate of change between input and output involve several hours due to the mass of the pile.
It always seemed that if you were to define the statistically lowest demand and run the nuclear reactor at maximum to reach this systemic demand level, such as 700M watts and use an adjacent 500 M watt CNG plant running at 1/2 throttle, you would get the greatest efficiency from the nuclear system. At the same time reduce more then 3/4 of the CNG demand and have significant headroom to meet potential increases in demand. The difference is, with the CNG I can shutdown the throttle and begin the cool down within 1 hour and I can start it up again in a similar time frame.
The “people in the business” I have talked with suggested this as a different operation model. Using a Round Robin system, a couple of the regional Operating Companies would always have a CNG system on line, ready to go, so if anything happened to one of the groups nuclear systems there would not have to be a black out should an unplanned shutdown occur. The point is, I believe the earlier statement I made is correct, based on experts I have talked with and what I have read over the years. (Did you read the other post in your “in the business” link…?) Now if they could only get consensus and government assistance to fix the National Grid…
Cheers!
Dave Cooke
SecularAnimist, but you should not ignore the fact that Americans, at least until recently, did actually “want” huge, expensive, gas-guzzling SUVs, Madison Ave. or not.
G.R.L. wrote: “… the alternative to nuclear risks is not no risk but alternative risks …”
Your first link is to a story about one worker being killed and another injured when a wind turbine tower collapsed. The second points to a list of articles about carbon monoxide poisonings, including the use of carbon monoxide to euthanize animals at a shelter and several articles about the apparently deliberate carbon monoxide poisoning of some children by their father.
Are you seriously suggesting that these “risks” are comparable to the risks of catastrophic nuclear power plant accidents, or terrorist attacks on nuclear plants? Or the risks of accidents or attacks on nuclear fuel storage and transport? Or the risks of nuclear weapons proliferation? Or the risks from the toxic pollution associated with mining and refining uranium?
Given the choice between the risks of nuclear power and the “risks” of wind turbines, concentrated solar thermal power plants and photovoltaics, I will gladly accept the “risks” of wind and solar, any time. (You will note, by the way, that there has never been demand for any such thing as a “Price-Anderson Act” by which the federal government — which is to say the taxpayers — provides insurance against catastrophic destruction from wind or solar facilities; while without the actual Price-Anderson Act which provides this insurance for nuclear power plants, not one single nuclear power plant would exist in the USA.)
It makes no sense whatsoever to accept the toxic pollution and grave dangers of nuclear power if we don’t have to. And we don’t have to. The USA has ample wind and solar resources to generate more electricity than the entire country currently uses. Even something as simple as recovering waste heat from industrial processes could generate more electricity than all the nuclear power plants in the USA. There is no need for nuclear, and thus no need to deal with its serious harms and grave dangers.
Re: G.R.L. Cowan @150: “So if nuclear power plants really weren’t throttleable, it would be atmospherically better to run them always at 100 percent, and shunt their unwanted electricity through large on-site resistors”
And here thought the plan was to use the off-peak excess generation to produce hydrogen for transport fuel.
As cold as possible.
During the winter, when the full-sun daytime temp is in the 70’s (measured IN THE SUNSHINE), Vmpp (Voltage — maximum power point) is in the 85VDC range for my system. Right now, with the full-sun temperature closer to 100, Vmpp is is 80VDC. The sun is way off-axis due to being almost at the extreme north of the equator, so I’m close to “winter” angles between sun and panel, but they are also hot, so I’m really losing out (except that I get about 12 hours of sunshine on my panels) and daily production from my 2100 watt array is 8 or 9 KWH.
Your idea is great, but other than supercooling and solar concentration, you’re not going to see results. It costs energy to move the cooling fluid, and my own experiments with a garden hose showed that the volume of cooling water per minute was pretty hefty. One time, very close to solar noon, I hosed down my entire array until it stopped steaming, then watched the output climb to 10% above the previous value (about 200 watts DC). Within 15 minutes the output had fallen back to its previous value.
Re 143:
Most likely you are buying all sorts of carbon-emitting power with offsets used to make up whatever they can’t provide when you need it exactly.
The wind I buy for my house (because I don’t make all of my power via solar. Yet :) ) probably comes from West Texas. But if the wind stops, the power has to come from somewhere, and that’s probably a coal plant somewhere nearby.
Re Anne @152: It’s a billboard shouting: “Look at me how progressive and green I am!!”
For some no doubt it is. For others it’s a billboard shouting: “Yes, the Prius is a real car using real off-the-shelf higher efficiency, lower CO2 emission technology that real people can buy here and now.”
In comment 157 Jim Eager said,
Perhaps that would be better still. Cars powered by pure hydrogen have existed since the mid-1970s. Do you get around in one? Do you want to?
Please keep in mind that diesel fuel in the US is of lower quality than in Europe, and that those nice TDI diesels sold in the US are modified to work with the fuel available here. There’s an efficiency drop, and they are more polluting, than their European counterparts.
We’re mandating higher quality (lower sulpher, I believe?) diesel here in the US and the switchover is soon, and that disadvantage will disappear.
And don’t dismiss hybrid technology so quickly. VW’s made a TDI diesel hybrid prototype that does extremely well.
For those who keep saying stuff like “my ford fiesta gets 50mpg and it’s not a hybrid” please keep in mind that comparing it to a prius is a bit of an apples-to-oranges comparision? That a hybrid version of your fiesta would see the same increase in mileage that toyota squeezes out of a Prius compared to an equivalent-sized conventional car?
A TDI diesel hybrid Smart Car would rock for my urban driving needs. Which don’t amount to much, since I telecommute … :)
Jim #159:
I know, I own one. But read this:
http://www.usatoday.com/tech/science/discoveries/2006-08-06-brain-study_x.htm
When asked about their motives for a decision, most people will try to bring up logical justifications. I guess that is because it is the cognitive part of the brain being activated when you must answer a question.
The discussions above about nuclear are a good example. In my opinion you like nuclear or you hate it (emotion) and then you go looking for as much arguments (logic) to support your preference. The pro-nuclear people will attach much value to the low emissions and downplay the risks, while the contra-nuclear people will attach more value to the risks and downplay the low emissions by pointing out that there are alternatives.
But of course, facts and logic can change your emotions. I bet a lot of people turned anti-nuclear after 26 April 1986.
re: #154
There are no nuclear reactors used by public utilities to produce electricity in the US that have a ‘molten sodium heat exchanger’. None.
All nuclear reactors used by public utilities to produce electricity in the US heat coolant water by ‘direct heating of water within a nuclear pile’. Everyone of them.
Well in Arizona you can use swamp coolers due to the dry air. Swamp coolers are significantly more efficient air conditioners than what you can use in other places.
How much more efficient? About 10x.
RE: 158
Thanks for your observations “Herder”. I had suspected this to be true; however, I am not able to get a value from the manufactures. The solar water heater design I was going to employ was similar to a 1973 Popular Mechanics design. They had suggested getting a piece of copper plate about 1/16th thick and solder copper tubing to it. Then you were to coat it with a dark maple green paint, housing the whole think in a expanded styrene box with a sheet of glass over the top. I looked it over and decided to try a copper sulfate/charcoal mixture in a flat varnish back then, it was a mess. (You were supposed to used a solvent to cloud the tacky surface…) The the styrene would not take the exposure. So I have modified the design a bit.
I can get a refrigerator ice maker kit with about 30 feet of 1/4th inch dia. copper tubing and fill it with sand bending it with a radius of about 2-2.5 inches. I expect to use two kits per panel. Next is to silver solder them to the copper plate. As I can not get copper plate I fear I am out of luck. (A friend turned me on to a source for brass/copper plated stainless steel for about 1/3 the price of brass plate.) I am to solder the coils to the plate using a propane torch. The design calls for (2) ball check valves, one in the bottom where the water enters. The operation is supposed to be water enters and heats up, pressure builds, the water expands out the top check valve and falls to an accumulator. The pressure builds again and steam is released, pressurizing the accumulator until the coil is empty then the bottom check valve opens and more water enters.
The idea for controlling how much heat builds up in the collector is the height of the reservoir tank in relation to the bottom check valve. High and most of the coil is liquid, lower and more of the coil is vapor. The idea is to reduce the vapor if you want the panel the coolest; however, it also means the output is cooler. So somewhere in between would be about optimum. And that was what I wanted the recommended or optimum heat value of the solar cell for.
I am able to get several different steel plate mounted solar cell panels (ranging from 60 to 170 watts peak at 24VDC) and I am thinking of trying lithium grease to thermally bond them to the back of the solar water panel. Since the tubing is now pointed at the ground and the heat comes from the solar cell side I do not need to coat the tubing. Though it is recommended that you use a fiberglass or high temperature foam insulation over the tubing. Also if you have no intent on producing steam with the system you would want to use a anti-freeze mixture as the working fluid.
When all is said and done you simply take a exterior 2×4 and using a rip/cutoff saw and a Dado blade cut a slot up the wide side from end to end. Then you cut the ends to form a 45 degree frame, apply a little exterior/marine adhesive, slide the plates in the slots, tap in a few nails and Wa-La make your connections and go.
It is just that before I invest the roughly 1400.00 (USD)(to use a 170 watt PV panel) in this project I wanted to get an idea of the temperature I needed to target and then find out if it would be achievable. (With my math skills being poor I have to do most things empirically….) If I have to go to a R410a refrigerant, a water bath or geothermal heat exchanger may not work and as you said it would take more power to drive it then what would come out. I have been playing around with using a Stirling engine; but, that is taking the idea way over the top.
Cheers!
Dave Cooke
Regarding post 37 on pumped storage.
I’ve been fighting a local pumped storage project largely because it is unprofitable (confirmed by FERC and a few other reports), at best returns only 80% of the energy put in (that number is uncomfirmed), appears to be used to allow a small group of entreprenuers to bypass California’s transmission line authorization procedures, and (my biggest reason) it as well as it’s transmission line (a major incterconnection called the Talega/Escondido-Valley/Serrano interconnect) will be built in the Cleveland National Forest.
Though the proponents claim they will buy wind-generated electricity to fill the reservoir, a plant that will lose $124 million per year (FERC’s numbers) must be ready at times of peak demand and therefore will probably need to set up long-term contracts with more reliable sources, such and coal or oil burning plants, rather than hope the wind is right.
In researching this, we’ve collected a lot of documents on the financial drawbacks of pumped storage. Our website (the oppostion) is http://www.stopleaps.info; the proponents websites are http://www.evmwd.com/depts/admin/public_affairs/leaps/default.asp and http://www.leapsforward.org/
John Garrett
Cold climate air source heat pump:
http://www.gotohallowell.com/technical.html
dhogaza wrote: “For those who keep saying stuff like ‘my ford fiesta gets 50mpg and it’s not a hybrid’ please keep in mind that comparing it to a prius is a bit of an apples-to-oranges comparision? That a hybrid version of your fiesta would see the same increase in mileage that toyota squeezes out of a Prius compared to an equivalent-sized conventional car?”
Well, that would be me boasting about my 1991 Ford Festiva. I am not trying to say that it is a better car than the Prius with regard to efficiency or emissions or anything else (although it is a darned fine little car, still running like a champ at age 17). My point is that the mainstream, major automobile manufacturers have had the technology to build 50 MPG conventional gasoline-fueled cars for 20 years, but have chosen not to build and sell such cars — not in the USA, anyway. It is my understanding that Europeans have long had the choice of buying small, ultra-efficient gasoline or diesel fueled cars that get 60 MPG or better, but these cars are not sold in the USA.
For my own needs and preferences, the Prius is too big, too expensive, and too complex. If I had to buy a new car, what I would want would be a pluggable-hybrid version of the Honda Fit, or the Toyota Yaris, or perhaps as you suggest the Smart Car — preferably designed like the Chevy Volt with an all-electric drive train and the combustion engine serving only as a generator. I have heard that an electric version of the Smart Car is planned for the US market in a few years.
Actually I had hoped that Toyota would make a battery-electric version of their low-cost compact car the Echo (which was replaced by the Yaris). The only reason being that I like the sound of “Electric Echo”.
Off-topic, where-ever I place this, but certainly relevant to RealClimate.
Locally my view to the west is unimpeded except by the curve of the earth. So with these long afternoons and evenings at about 47 degrees north latitude, the sunlight passes through hundreds of kilometers of the atmosphere. While I have noticed what I take to be more water vapor in the air in the past couple of years, yesterday afternoon and evening was quite a shocker.
The water vapor produced a substantial umbra of yellow glow around the sun, extending at least six sun appearent diameters in every direction.
While used to seeing “red sky at night, sailor’s delight” fairly frequently, this is something completely new to me, occurring with nary a cloud in the sky.
Others?
For anyone who wants to find out all about solar PV performance, and setting up your own system, one of the best sites is:
http://www.powerfromthesun.net/book.htm
For example, to compare solar cell performance at 25C, 50C, and 75C:
http://www.powerfromthesun.net/chapter5/Image170.gif
The main area where this raises problems is in concentrated solar system that focus large amounts of sunlight onto small, high-efficiency cells.
To see how photovoltaic output varies with incident sunlight (and to see why solar is the perfect solution for any equatorial country):
http://www.powerfromthesun.net/chapter5/Image168.gif
Those are I-V curves, which describe the current through the cell (amps) as well as the voltage potential across the cell at different latitudes.
Power output (watts) is current times voltage. For the net energy delivered, multiply by time (kilowatt-hours). Your electricity bill lists your power consumption in kilowatt-hours – but how many people know how many watts their houses are drawing at any given time? There’s a simple solution that should be included in the building codes: an electric meter that hangs on your wall and tells you your current energy consumption, in both watts and dollars. “At your current rate of energy consumption, your monthly energy bill will be: ____ ”
That would motivate people to conserve energy, I do believe.
Controlling heat loss is important, but every PV manufacturer knows this and takes it into account. The basics are the same as in climate science:
Electricity is an unusual beast in that power output is closely connected to electrical load resistance – the optimal solar panel performance occurs when the load is perfectly balanced with the solar output (think of this as the optimal gear setting on your bicycle, say).
That’s why “smart electrical grids” on the large scale, or peak power point tracking systems on the small scale, are critical components of any solar system.
The same is true for wind power systems – in both cases, the electrical system has to be able to store up excess energy delivered by the turbines or by the solar panels. This is where the various energy storage systems come into play – pumping water up hills, large spinning flywheels, high-capacity deep-cycle batteries (they need careful maintenance!), and so on.
To get back to the cooling and warming the house issue, it is possible to build very low-power AC units that run off as little as 5 amperes – they’re very popular in the middle east:
Iraqis beat the heat with low-power air conditioners
Oakland Tribune, Apr 12, 2008 by Hannah Allam
Just some quick notes:
#91, those tanks would be huge.. A ton of cooling is the amount of heat required to melt a ton of ice in 24 hours(288,000 btu). The average house has a 2 ton load.
Re the geothermal.. Don’t use the waterfurnace site as an example, if I used Exxon as a an accurate source for examples of responsible fossil fuel environmental stewardship, everyone would go ballistic..The problem with geothermal, is that you need a huge heat “field” or sink. If the weather turns cold very quickly and you draw down the field quickly, you build ice around the field tubing, and your rate of transfer from the field slows dramatically and efficiency drops down quickly. The other problem is you have to add in the cost and both fiscal and environmental of the field loop liquid, usually glycol or methanol, and the tubing which is plastic, drat more petroleum based products.. There is no free lunch…
The interesting thing about the air conditioners though as compared to other devices, as the house temperature gets higher, the efficiency and capacity goes up with a rise in suction pressure, the mass flow rate increases with a denser suction gas.
Also there are hydronic and steam heating, both gas electric and solar, without pumps typically one pipe gravity return systems, they have fallen out of fashion because of the real estate they take up.
David Benson, Are you sure it is water vapor? Could you be seeing increased aerosols from Asia? Satellite maps are quite impressive. What you are describing sounds like a halo, but that would typically be at 22 degrees around the sun. Do you have a photo?
Re Anne van der Bom @162: “Jim #159: I know, I own one.”
So do I, Anne, and I can honestly say ‘image’ was a very, very minor part of our decision to buy a Prius. We bought it because it was time to replace our 10-year old Subaru wagon with 200K km on it. With Fed and Prov rebates, the Prius actually cost a bit less than replacing the Sub in kind. It doesn’t have quite as much cargo capacity (I often use the car for work and need the room for gear and tools), but it does have just enough, so its size met a requirement for us rather than being a minus. Plus it can carry a canoe–but only just, because of the curved roof line. The only drawback was it’s not 4WD, which can matter in Great Lake winters, but we didn’t want a hybrid suv. It did ok this past winter, though.
And it was certainly hard to beat the mpg–about double the old Sub. The clincher was knowing that it would definitely produce a smaller carbon footprint than another Sub would, which IMO is worth far more than worrying about how long it will take to pay for itself. At the very bottom of the list was image, and the image we wanted to project was the one I stated previously: this is a real car using real off-the-shelf higher efficiency, lower CO2 emission technology that real people can buy here and now.
Hybrids are definitely not perfect, they’re only a step in the right direction, and I know even smaller, more efficient ones are just around the corner and even better choices will be available in the very near future, but it was the best choice available at the time we needed to replace an existing aging car.
Re:#136 “A/C is less energy intensive than heating? Well, it’s true.”
This flys in the face of Raypierre’s mathematical analysis and conclusion that air conditioning is 2.19 times less efficient than heating, for a given temperature difference between the inside and the environment.
It’s well to think outside of conventional solutions but we have to live within the given constraints of the real world, not only for thermodynamics but for socio-economic and political pressures as well. The pressures right now ,as has been pointed out above, are to develop shale oil, tar sands and coal liquefaction resources in light of the current price of oil. Even though these alternatives are an environmental nightmare.
[Response: The arithmetic leading to 2.19 was just a way of showing that looking at the SEER rating (which WIRED probably had in mind, but didn’t actually bother to explain) is misleading. You have to think about everything that happens along the way to delivering the electricity to your air conditioner, and all those numbers matter. Showing the arithmetic for one set of numbers was a way of focusing discussion on what the real issues are, and from the subsequent discussion here I’m very happy with the way that exercise turned out. If you ask just about anybody what the biggest issue in CO2 emissions is, they’ll tell you it’s coal, and it’s equally clear that increase in electricity demand — driven in part by air conditioning — provides the main impetus to build more coal-fired power plants. –raypierre]
in 121: [Response: The sooner the conventional oil is used up the sooner people will turn to tar sands and coal-to-oil in a big way. But I have indeed heard economists make the argument that conservation of oil makes little difference since the worldwide demand is so huge that reductions in usage here just lower the price and lead to increases in usage elsewhere. I’d like to see some numbers put on that argument, though. –raypierre]
Well, even at a steady inflation adjusted price of $20/barrel (about the median price over the last 50 years) we don’t see demand growth much higher than 3%. The US uses about a quarter of the world output so cutting the US use by a quarter cuts world demand by 6%, and that would certainly be a strong reduction in world demand. After that first step, which would send the price of oil way down, we’d only need to cut by about an eighth or so further each year to balance typical world demand growth while keeping oil prices low during our transition off of oil. With a bit of cooperation with some other nations that want to get off oil, we might be able to stretch the low cost transition out to fifteen years at low oil prices, about the amount of time needed to convert a transportation fleet.
The thing is, even if oil is free, you still need a car to use it and you only get 24 hours in a day to drive it. So, there is a limit on how quickly demand can grow based on how quickly people can afford cars, which are still not cheap. So, to say that a strong reduction in US oil use would have no effect is not correct. We have the leverage to force oil prices to the bottom owing to our large consumption.
But, if we don’t do this soon, then the oil supply will be so poluted by expensive to produce oil, which we are encouraging now with high prices, that we will not be able to force prices down. So, we’ll need to make the same transition, but we’ll have to do it on expensive oil rather than cheap oil.
I’ve said a little bit more about this here: http://mdsolar.blogspot.com/2008/06/oil-is-too-expensive.html
RE: 170
Hey Ike,
Thanks for the values in the 25/50/75C chart. It looks like the best solution will be a water/glycol liquid only system and mounting the reservoir high would keep the panel the coolest, though it would be closer to 50 Deg C rather then 25 Deg. C. It appears that the idea of some type of refrigerant system would best serve reducing the heat of the PV panel though…. (I just do not have a good source of ammonia and hydrogen, nor do I feel competent enough to carry this one off.)
I looked at your Solar PV reference and noticed a few broken links (IE: Chapter 7). Hopefully they can be resolved easily.
I also looked over the mini split system article you linked in and I am curious. I have looked over most of the mini’s in the last two weeks for my step son and have not found anything smaller then 15 amps at 115VAC in the 10,000 BTU range. (Generally, the 15 amp units are of the 9,000 – 12,000 BTU units class and can be reverse cycle as well.) From what I see, even the 5,000 to 6,500 BTU units still draw better then 5 amps at 115VAC.
Now if the idea is to use a European 230VAC unit there might be one or two manufactures with 5-9K BTU models in the 5 amp range. I guess the main point is a several small window systems at 4-5 amp/115VAC versus a single mini split compressor at 5 amps and 230VAC with a choice of multiple mini air handlers of 2 amps ea. is the big news. Though other then being ductless this would not be much different then a standard European 1 ton split Air-Air Heat Pump system….
Again thanks for the PV info. I think this is going to be a good Fall project for a 60 watt PV panel….
Cheers!
Dave Cooke
I weighed in at #122 about Prius mileage because of some previous comments I found doubtful. Others have kicked around the same topic, with model comparisons. To promote brevity and a pleasant atmosphere, I’ll just note gently that some claims above fail to note which vehicle is discussed, and others that mention a model are rather strikingly optimistic compared to official figures, and even compared to claims made by those selling a used car of that model. Let the reader beware.
By and large, most or all of the commenters agree on goals.
The problem with the Prius approach can be summed up with a little arithmetic. If you get 60 mpg, and you replaced a 20 mpg vehicle, and your mileage remained unchanged, what reduction in fossil fuel use would you achieve? 10 gallons gets you 600 miles, while it used to take 30 gallons with your old vehicle. That’s a 66% reduction in fuel use – sounds pretty good.
However, if we look at that in terms of national gas consumption, and we reduce national petroleum consumption by 66%… well, that would mean that the 20 million barrels of petroleum we consume per day would be reduced to some 6.6 million barrels… and it would also have zero effect on coal and natural gas consumption.
Realistically, to slow climate change appreciably, you have to eliminate fossil fuels more or less entirely. For transportation, the only way to do that is have electric cars powered by sunlight or wind-based systems (which does include biological photosynthesis). Biofuels, however, don’t have much potential for large-scale energy production – one of the main reasons being that crop yields seem to be taking hit after hit on a global basis right now – floods and heat waves being the culprit. That really leaves solar and wind as the two plausible replacements. (And no, PV panels don’t need pumped cooling systems, as anyone could have told you – although the notion of mixed solar water heating / solar photovoltaic system is intriguing, since most natural gas consumption outside of industry is used for heating).
The basic fact is that solutions which don’t have as their goal the almost complete elimination of global fossil fuel combustion are really nothing more than a game of musical chairs on the Titanic. However, the U.S. Congress has so far failed to renew the renewable energy tax credit programs:
Congressional stalemate over renewable energy – Zachary Coile, Chronicle Washington Bureau Wednesday, June 18, 2008
The oil depletion allowance, however, remains unchanged. Tax credits for petroleum production are set in stone, but those for renewable energy are persistently blocked… you might want to give your representative a call on this one.
Ric Merritt #177:
I agree with you. Their is usually a lot of boasting about mpg’s. Most often an dream scenario mileage is portrayed as the year-round average. Or they report the mpg indicator on the dashboard. The only correct method is the Excel-method: registering distance and fuel at the pump and put that in a spreadsheet and then calculate the average over an entire year.
A comment on the difference between claimed mpg and rated mpg: My experience is 1. that it is possible and 2. that there are large differences between cars. For instance I have owned a Volkswagen Polo 1.9 SDI for four years and got a consumption of 4.3 l/100km (using of course the Excel method). The rated consumption was 4.7 l/100km. For a Honda Jazz (Fit in USA) 1.3 CVT these figures were 5.5 and 5.9 respectively. For my Prius it is 4.7 and 4.3.
Why can’t I achieve the rated consumption in my Prius? I have two explanations. The negative one is that Toyota optimized the Prius for achieving a low official consumption rating. The positive one is that an economic driving style has less effect in a Prius because it is what the hybrid stuff already does for you automatically.
Edward Greich’s sociopathic statement that Chernobyl killed only 52 people speaks for itself. Nuclear power is NOT cheaper, the French plants ARE old and in trouble, and one of the biggest red flags is that all the people pushing nuclear power now have Margaret Thatcher as a role model – There Is No Alternative, and you pagans that don’t worship Ayn Randite market gods have no say, because we say you don’t.
#178 Ike, I agree with you about using food crops to provide biofuels. You need far too much agricultural land. Most of the current ethanol projects are excuses for more subsidies to agriculture.
However the use of algae to provide biofuels is far more promising. At current fuel prices it is not far from being economically viable. They also require far less land. They could supply our liquid fuel needs, at least enough for long distance transport.
I’ve seen the results of some of the experiments on algal biofuels. I expect they will be available in quantity, enough to make a difference, within the next 20 years. That is being pessimistic
Ike Solem #178:
Your reasoning sounds like ther is no use in taking small steps. Each journey begins with the first step. More fuel efficient cars are simply the first step, nothing more nothing less.
Funny b.t.w. that you mention the Prius in your first sentence. I think the significance lies not in its fuel economy but because it is the prelude to electrification of personal transport. You can already see it happening by the plug-in conversion kits that are being offered by more than one company. I therefore dare to say that the Prius fits your vision like a glove.
Marion
http://www.who.int/mediacentre/news/releases/2005/pr38/en/index.html
This from the WHO. It IS 52 as of 2006. That figure might go up to 4000 (this is their worst case senario by the way)once everybody directly connected with the disaster dies. The WHO number does not include children with thyroid cancer (radioactive iodine accumulation) since this can actually be avoided once people become aware of it (it IS included in the 4000 figure though). So actually Edward is right to quote 52 but maybe should have given the second figure with an explanation.
The story behind the report is pretty interesting too since when they first came up with 52 deaths they couldn’t believe it and went back to do more checks. All the preconceptions about kids with horrible genetic mutations turned out to be false. This was further confirmed by looking at the wildlife population living close to chernobyl; no mutant rabbits. Nothing. And they’d been there for years! Yet again it provided a valuable lesson that biology doesn’t always react linearly. Given our knowledge of the effects of radiation at high doses we had expected to see a dose proportional effect so that there would be a correlation between exposure and genetic mutation/death at ALL doses. So even low level radiation would be bad news. It’s doesn’t look like this is happening at all. The suggestion is that low level radiation switches on all the repair genes and these get upregulated until at higher doses they get overwhelmed. It’s an area of considerably research because the implications of being able to switch on these genes by another method has opened up alternative ways of looking at cancer or degenerative disease.
So I’m afraid Edward is no sociopath. It’s just that we don’t understand as much as we thought we did about radiation. The fear of radiation turns out to be a little irrational. What it means is that nuclear energy (in these terms) isn’t quite as bad as is often suggested. It’s just sad that it took 52 deaths to find that out.
Oh and the “Chernobyl couldn’t happen in the West” is accurate. Our reactors are designed to self-quench if a runaway starts to occur in the way that the Russian reactor did. We can’t have the same accident; just a different one that’s much much harder to do. It’s pretty clear with the right design and oversight nuclear is relatively safe froma generating point of view. Radioactive waste is fine too if people are willing to make a decision about what to do with it. Some countries ahve bitten that bullet, some haven’t. In the UK we still sit on the fence.
Hope this clears up some of the confusion.
raypierre (response @18) wrote:
“Building a whole new kind of world, seeing how you can live well and put out less carbon, well what’s cooler than that? Lots of opportunities to think outside the box, and many of them a lot of people are going to make a lot of money out of as well. Like maybe heat pumps for home heating. They exist, but the creative engineering on them has just barely begun.”
On that note, I recently read Cradle to Cradle – Remaking the Way We Make Things (McDonaugh and Braungart) who have some interesting (dare I say radical?) ideas on how we ought to be making things (everything from drinks bottles to buildings) with the specific intention that *every* part of them is able to be re-used.
http://www.mcdonough.com/cradle_to_cradle.htm
Thanks also to those here (Lee A Arnold, Doug Heiken and scott_g) who point out the widespread fallacies inherent in the new growth plantation vs. old growth forest argument. Carbon sequestration is far too important an issue to be left to the devices of government state forestry departments or various elements of the logging and timber industry, and the need to keep the biological truth at the forefront of the public and government minds has never been more pressing. It seems a pity (to me) that in the headlong rush to promote all sorts of carbon sequestration ‘fixes’ the one thing governments and individuals alike forget is the role of biodiversity in the regulation of the planet’s climate.
Mark posts:
Secular posts:
Okay, make it “production.”
America produces 25% of world GDP. That’s why it uses 25% of world resources. The “America is only 5% but uses 25%!” trope would only be a problem if America were somehow sucking up resources (net) from other countries for its own benefit, as if America were the only old country in the world and the rest of the world were its mercantilist colonies. That’s true in the zero-sum-game worldview of Marxists like Nick Gott, but not true in the real world.
Keith #183:
This was further confirmed by looking at the wildlife population living close to chernobyl; no mutant rabbits. Nothing. And they’d been there for years!
Now to be honest, what is the life expectancy of a mutant rabbit? Thanks to the law of survival of the fittest, it would probably not make it through its first week. I think the visible lack of mutant animals around Tsjernobyl does not prove they do/did not exist. I can agree with the other arguments though.
@Anne
You are right and I wasn’t thinking. Of the 18 models we rate higher than the Prius, only one is available in the US. However with changing consumer preferences, American fuel prices closing in on Eauopean levels and hopefully the Japanese and European producers seeing it, this will change soon. Modern diesel engines are very efficient. The Smart 42 (also not available as a diesel in the US) officially ranks highest with a mere 88g/km which means more than 70mpg. However our own cycle takes the typical driving pattern for a specific model into account, which leads to the Smart falling down to 5th place because the city and short-trip rate is higher than the standard cycle reflects. With VWs BlueMotion models and BMWs x18d/x20d, we rate long-range-driving higher because these cars are typically driven by sales/service people and long-range commuters and therefore share the top spots. For the Prius there seems to be a typical customer personality rather than a typical driving pattern (in their forums over here, they discuss things like whether a 5 or 7 meter distance behind a truck provides the best slipstream and whether buying toothpaste at your trip’s destination is more efficient than taking it with you). It would certainly take a shot at the pole position if it was primarily driven in cities but it isn’t. For European cities, its simply too big and too expensive (roughly the equivalent of 40.000$ if decently equipped) and would never return the investment on the relatively short distances typically driven around towns – and serious environmentalists living in cities wouldn’t use a car anyway if they can take a bus or subway. Personally, I see the biggest problem with non-plugin hybrids in the enormous technical effort which yields little and only in special circumstances but leads to a high pricetag effectively keeping it from making a noticable difference on a global scale. I wonder why Toyota sells Lancruisers, Camrys and Hiluxes but doesn’t develop an affordable Prius with all its light-weight, low rolling resistance and aerodynamical advantages, but with a simple, small, light, cheap, clean and efficient diesel engine (they do know how to build those). Probably because it would easily outperform the hybrid in almost every respect apart from pure city driving – but would be too much of a dull, every day product to make it into the garages of filmstars and politicians and would therefore blur the Prius hype. I’m not a Greenpeace believer by any means but when it comes to judging the global importance of hybrids, I think they’ve got it about right.
What I don’t see at all is the Prius triggering EV development. All the major players invest huge sums into that essential technology and have done so since long before the Prius. Neither the electric car nor the hybrid is a Toyota invention and I’d not bet my money on them being the first to come up with the real thing just because they took a step in between that others didn’t think of as profitable enough. The race for efficient and safe energy storage dominated the past years and it looks like rather conventional but “intelligently” managed Lithium Ion finally won, at least for the first generation, over hyped but delayed promises in nano and capacitor technology. We’ll see how it all turns out. 2011 will be an exciting year for the industry.
Thank you for the great post discussing the relative energy usage associated with heating versus air conditioning. It is a very interesting question sitting here in New England to ask whether (other things being equal) energy usage (and associated GHG emissions) will go up or down as the climate warms given the trade off between less heating and more air conditioning?
I found the information in the two reports cited below to suggest that energy usage is likely to go up. One aggravating factor in this is that retailers are now offering very low cost (initial purchase price) window A/C units to those of us without potentially more efficient existing whole house systems with heat pumps. A few really hot days and people in New England that have never had A/C buy the low cost window units and start using them, first on very hot and humid days and then maybe on days that prior to that they would not have.
Regarding the question of whether future climate warming will result in more or less heat-trapping gas emissions when decreased heating needs are balanced against increased air conditioning needs: “As a whole [USA] increases in carbon emissions from higher air conditioning needs more than offset decreases in carbon emission from reduced heating needs” — summary from EOS v. 87 No. 37, 12 Sept. 2006 Mohi Kumar, Staff Writer. See Also: Hadley, S.W., Erickson III, D.J., Hernandez, J.L., Broniak, C.T., and Blasing, T.J., 2006, Responses of energy use to climate change: A climate modeling study: Geophys. Res. Lett., v. 33, p. L17703, doi:10.1029/2006GL026652.
This isn’t about GDP and economic or industrial production. Just because Americans are rich (“produce so much”), this does not give them the right to overuse earth’s natural resources or to pollute the atmosphere. The atmosphere belongs to the whole world. The US has the lead in greenhouse gas emissions worldwide and only 5 % of the world’s population lives in the US. That’s what people are talking about. Nothing Marxist about that.
RE: 163
Hey Dan,
Thanks you are correct, of the 35 remaining units all appear to be PWR or BWR units. I responded too quickly and referenced the memory of an old 1965 text image regarding proposed designs, forgetting the change over that occurred in the late 1960’s design theory. (Must be a combination of CRS and old age…)
http://www.eia.doe.gov/cneaf/nuclear/page/analysis/nucenviss2.html
The primary point remains though that the time required to cool the pile exceeds the cycle time required to respond to peak and minimum demand. This still suggests that an adjunct system must be part and parcel to respond to demand changes…
RE: 178
Hey Ike,
Granted the use of a refrigerant such as R-123 (last production date 2020…) in a PV system cooling system may be a little over the top. However, when coupled (in a two stage system) with a glycol/water radiant or a swamp cooler system, it would increase the peak voltage and offer a hvac/water heating alternative as well as to help peak the PV. (For the swamp cooler stage you could even couple a small, low rpm, wind turbine such as a VAWT to provide the mechanical drive for the roller…)
Cheers!
Dave Cooke
Megan Boris-
How much does composting impact your carbon footprint?
Excellent article, and nice to see that at least some posters understand how a Prius works. And that you understand that the argument about buying a used car is at best incomplete and misleading as it is typically stated.
A few comments:
Argonne national labs (and others) have pretty consistently estimated that production and scrapping of traditional passenger vehicles accounts for roughly 10 percent of vehicle lifetime energy use. Focusing on the energy used in vehicle manufacture is just totally backwards. To a pretty close approximation, higher mpg = less energy used, lifetime. See figure 5 of this publication:
http://www.transportation.anl.gov/pdfs/TA/106.pdf
Discussions of the Prius and the Prius battery always omit a life-cycle perspective. Traditional cars use *more* metal in their batteries than the Prius uses in its batteries — over the life of the car. That’s because a typical sedan can expect to use three starting batteries over its lifetime (at 25 lbs of lead each), while a Prius can expect to use one traction battery (30 lbs nickel) and possibly two (small) lead-acid batteries used to boot the computer at startup and modulate the 12-volt (“hotel”) loads, at 12 lbs of lead each. (The Prius lead-acid battery is not subject to the peak load of starting the engine, so it lasts longer.)
Finally, no discussion of carbon footprint is complete without mentioning food. My estimate is that my family reduced our carbon footprint as much by changing our diet as we did by switching to a Prius.
In the US, transportation accounts for about 25 percent of total energy use. Depending on whose statistics you believe, food — farming, processing, distribution, and preparation — accounts for roughly 17 percent, although that figure will vary quite a bit depending on what is included and how it is calculated. (And that 17% obviously overlaps with transportation).
Foods vary enormously in terms of the fossil fuel (k)calories required to deliver an edible (k)calorie. Grain-fed beef is typically cited as the worst offender due to the inherent inefficiency of converting grain to beef combined with the large amounts eaten in the US, although it is not the worst in terms of input to output ratio (think diet soda in an aluminum can, or coffee and tea, for that matter.)
My contention is that, for most US residents, there is more low-hanging fruit for energy savings in the area of diet than anywhere else. Mainly because few think of the energy requirements for food production and distribution. And as far as I can tell, there’s a pretty broad consensus that number one on the list of easy energy savings is minimizing consumption of grain-fed animal products. No investment needed, no hassle, just a conscious choice. FWIW, the figure most commonly cited for production of grain-fed beef is 35 to 40 fossil fuel (k)calories for every edible (k)calorie. Assuming for the moment that’s roughly correct, a nice six-ounce (cooked weight) sirloin (~1000 edible (k)calories) embodies more fossil fuel than a gallon of gasoline (~32,000 (k)calories). Most of it isn’t liquid transport fuels, it’s other fossil fuels. But I hope you get the point — if the estimates on fossil fuels required for production of (e.g.) grain-fed beef are even close to correct, the impact of dietary choices is large and should be brought up in any reasoned discussion of green living.
Regarding the use of paper and other wood products I think that the best strategy to combat climate warming may be to use as much as you can, don’t recycle, rather, bury in landfills where the carbon will be stored for a long time (if methane is produced it should be collected and burned for energy production). The more paper and wood products that are used the more land that will be valued for and maintained as, or converted to forests. This will result in the sequestration of more carbon over the long term in soils, buried wood products, and aboveground biomass than would otherwise be the case if these lands were converted to other uses. Forested lands are also preferable to the alternatives for a host of other reasons that have been mentioned.
The article also falsely implies that organically grown produce requires higher shipping costs than conventionally farmed produce. Isn’t this a false dichotomy? Many consumers can purchase locally grown organic food at their local farmers market, it isn’t necessarily shipped from California. Also, they didn’t make any actual effort to compare the fossil fuel inputs for organic versus conventional produce. I’m not sure how they’d compare in total, but the claim that shipping costs overrides the benefits of pesticide-free production is specious.
The difference, of course, is that energy efficiency is immediately functional to the owner of a hybrid, whereas the off-roading capabilities of SUVs are only very rarely used by their owners. In practice, the former is functionality-driven while the latter is primarily image-driven.
RE the Prius issue, my common sense and cents told me that since we only drive about two to three thousand miles a year, we’d be better off waiting for the plug-in hybrids or complete electric cars to come out, and buy one of those. Then we could plug it into our 100% wind-powered electricity. It still wouldn’t make much economic sense if the car costs a lot more than an equivalent I.C.E. car (although EV maintenance and running costs are a fraction of ICE maintenance and running costs), but it would make environmental sense.
I had, however, wondered about the AC v. heater issue, and am glad you clarified it. However, even if the increases in AC usage entailed less increase in CO2 than the decrease in CO2 from decrease in heater usage in a globally warming world (i.e., even if it were a negative feedback), there are still so many other harms that GW would be causing, and so many other positive feedbacks that the AC-heater question is moot before you sit down to do the calculations.
Barton Paul Levenson wrote: “America produces 25% of world GDP. That’s why it uses 25% of world resources. The ‘America is only 5% but uses 25%!’ trope would only be a problem if America were somehow sucking up resources (net) from other countries for its own benefit …”
Forgive me but I totally do not get your point.
How is this 25 percent of world GDP that the USA “produces” — consuming 25 percent of the world’s resources in the process — NOT “for its own benefit”? Sounds to me like we five percent in the USA are consuming that 25 percent of world resources so we can live mighty high on the hog, enjoying the fruits of that 25 percent of world GDP.
And how is it NOT a problem that we five percent in the USA are “sucking up” 25 percent of the world’s oil production, meanwhile “producing” 25 percent of the world’s greenhouse gas emissions?
re: #191
Hello David, I don’t know where you’re getting your information about the number of operating reactors in the US, but you need to find a more up-to-date accounting. The EIA Web site has the info here. The information is also available at the NRC Web site.
There are 104 reactors operating in the US; 69 PWR and 35 BWR.
“Barton Paul Levenson Says:
19 June 2008 at 6:25 AM
America produces 25% of world GDP. That’s why it uses 25% of world resources.”
So the US produces 25% of the worlds resources because they spend 25%? That makes no sense.
IIRC, the US farming used 1 calorie of oil to produce 3600 calories of food. Now it is 1 calorie oil to 1 calorie of food.
Not looking so good, really.
A little more back on track, please remember that the SUV/Prius comparison was *per pound*. Well, given that it weighs a ton (which is why it gets 8mpg), this isn’t really helping much.
Add into that the occupancy rates are no better for the SUV and you see the comparison makes no sense: you drive one car each, not one prius or half an SUV…
As to “we need it for the kids” well, we were a large family (numerically and in width) and we sat in the standard UK saloon. If you MUST, then just RENT a really big people carrier for those long holidays.