Wednesday, July 28, 2010
Nissan Leaf
I got email from Nissan the other day. The date for ordering our Leaf will be in January, 2011. Can't wait! Our 2002 Prius is a fine car, a bit thin on the acceleration side though better than stock with the Pulstar plugs. But having a car that runs totally on clean, solar electric is something I've been looking forward to. Hopefully, it will not totally demotivate me from riding my bike.
Sunday, July 25, 2010
More on Costs
I've refined the carbon footprint calculations and cost estimates for our previous carbon reduction measures and for the post 2011 projection after the system remodel and electric car. My previous cost calculations have been based on the cost per kg. carbon reduced over the next year. That isn't quite a fair comparison, since if we had continued to use fossil fuel, we would have generated carbon every year and payed the cost of the fossil fuel every year. So in these calculations, I've calculated the cost per kg. carbon reduction over the projected lifetime of the reduction measure. As a rough estimate, I've used 10 years for the electric cars since the battery life is probably that long, though it might be longer or shorter, and 30 years for the measures on the house. For the new refrigerator, I've estimated 15 years and for the solar hot water system, 20 years. Also, I've ascribed the cost of the reduction measure for making an electric car into a zero carbon emitter to the solar PV, since the lifetimes of the solar PV and the car are so different (10 years for the car, 30 years for the solar PV).
First, the refined carbon footprint calculations:
The most effective reduction measure in our current plans is the solar PV. It results in a 17% reduction, causing the total reduction from the estimated 2002 base line to increase from 54% to 71%. The next most effective reduction is the electric car, at 13%, followed by the insulation and on-demand hot water heater, at 6%. It seems that natural gas usage is the most difficult carbon emission to offset.
Here's what the evolution of our carbon footprint looks like:
As discussed in my previous post, the solar PV contributes more zero carbon energy to the grid than the house uses, making the electricity footprint negative and offsetting the natural gas and gasoline footprints from heating/cooking and transportation.
Finally, the per kg. cost of the reduction measures calculated over the projected lifetimes:
The most cost-effective reduction measures here tend to be the hybrid/electric car, followed closely by the solar hot water and the new solar PV. The old solar PV and the pluggable hybrid are next, followed by the measures taken to reduce gas consumption from heating, including the double pane windows and reinsulating the house. Finally, the refrigerator is last.
The refrigerator was the most expensive because we bought a high end fridge in order to avoid having to reconfigure the kitchen for something else. The kitchen has a Subzero sized hole exactly where the fridge would fit, anything else would have involved some cabinetry work to reconfigure the hole. I can't say I am a big fan of high-end fridges, but the kitchen looks pretty nice the way it is, so we just decided to go for it. The cost of the measures taken to reduce the heating are also no surprise. We are basically ripping out the walls and putting in new insulation. It's a big, dirty job and it involves a lot of hand labor, hence the expense. But, as a practical matter, we need to put some steel in the hallway ceiling anyway to prevent the drywall from cracking, so we would have had to pay for the scaffolding, etc. for that anyway.
The cost of the plug-in hybrid is higher than the hybrid and electric cars because we got no subsidy for it. Neither the state of California nor the Federal government was giving out subsidies for plug-in hybrid conversions in 2008 (they since have changed policy and it is now eligible). The subsidies make all the difference, the Nissan Leaf would be around $10K more expensive without the subsidy. Hopefully the need for the subsidy will diminish over time as battery costs decline.
Surprisingly, the solar PV and solar thermal systems are close to the most cost effective. Most commentators rate them as expensive, and rate efficiency measures as more cost effective, but what such commentators are talking about is maybe putting weather stripping around your windows, not removing the walls and putting in more insulation. In reality, you need both. Reducing electricity demand by plugging power vamping appliances into power strips and turning off the appliances on the strip, replacing frequently used lights with CFLs, and buying new, power-efficient Energy Star appliances is necessary to reduce the electricity demand to the point where solar PV can completely offset the demand. Otherwise, the cost of solar PV is too high.
Natural gas use for heating and cooking remains the most difficult carbon generation source to remove. The work we're planning to reduce natural gas use for heating involves quite a disruptive change in our house, essentially replacing the insulation in the thermal envelope, but it will not reduce carbon emissions from that source to zero. We will still need some heat. If we had gone through with our plans to install a geothermal heat pump, the cost would have been even higher, much higher in fact. These considerations point up the carbon cost of our preferred built environment style for family residences in the US: single family housing with all four walls and roof open to the elements. With more multiple family housing, the cost of heating can be reduced substantially, though, of course, at a much higher expense due to the replacement of the existing built environment infrastructure.
The 10% carbon emissions that we can't reduce is about equally split between transportation and heating/cooking: 887 kg for transportation and 1300 kg. for heating/cooking. For now, it seems like we are at the limit of what we can do with current technology and our pocketbook. We need a car to get out of town. We could get a Chevy Volt which has much better gas mileage than the plug-in Prius, but our plug-in Prius works fine so it seems there is no need to buy something new (besides, I have a fondness for Toyota products). And, as mentioned, the cost of removing the heating/cooking carbon emissions from natural gas is simply too high. So, our only choice is to offset our carbon emissions by buying carbon offsets. The graph also shows the cost of buying carbon offsets from CoolIt.org and PG&E's Climate Smart program. In each case, the cost is pennies or fractions of pennies per kg. carbon offset. Carbon offsets are, by far, the most cost effective way to reduce carbon emissions.
Which brings up the interesting question: why not simply buy carbon credits and forget about taking the reduction measures? The reduction measures are from 10x to 100x more expensive. Many commentators are skeptical to negative about carbon offsets, because in the early days of carbon offsetting some projects were scams or would have proceeded anyway even without the offset. But both CoolIt.org and PG&E seem to have credible programs where the projects are solid and specifically designed as offsets, and PG&E's is even tax deductible (tax deduction was not included in the per kg. cost of the figure). If everybody bought offsets and nobody took any real, concrete measures to reduce carbon, we would be left with a built environment and transportation infrastructure that generated exactly as much carbon pollution as today. In reality, as with efficiency and solar PV, you need both concrete reduction measures and offsets. Implement the highest degree of reduction measures you can afford and use carbon offsets to take care of the rest.
First, the refined carbon footprint calculations:
The most effective reduction measure in our current plans is the solar PV. It results in a 17% reduction, causing the total reduction from the estimated 2002 base line to increase from 54% to 71%. The next most effective reduction is the electric car, at 13%, followed by the insulation and on-demand hot water heater, at 6%. It seems that natural gas usage is the most difficult carbon emission to offset.
Here's what the evolution of our carbon footprint looks like:
As discussed in my previous post, the solar PV contributes more zero carbon energy to the grid than the house uses, making the electricity footprint negative and offsetting the natural gas and gasoline footprints from heating/cooking and transportation.
Finally, the per kg. cost of the reduction measures calculated over the projected lifetimes:
The most cost-effective reduction measures here tend to be the hybrid/electric car, followed closely by the solar hot water and the new solar PV. The old solar PV and the pluggable hybrid are next, followed by the measures taken to reduce gas consumption from heating, including the double pane windows and reinsulating the house. Finally, the refrigerator is last.
The refrigerator was the most expensive because we bought a high end fridge in order to avoid having to reconfigure the kitchen for something else. The kitchen has a Subzero sized hole exactly where the fridge would fit, anything else would have involved some cabinetry work to reconfigure the hole. I can't say I am a big fan of high-end fridges, but the kitchen looks pretty nice the way it is, so we just decided to go for it. The cost of the measures taken to reduce the heating are also no surprise. We are basically ripping out the walls and putting in new insulation. It's a big, dirty job and it involves a lot of hand labor, hence the expense. But, as a practical matter, we need to put some steel in the hallway ceiling anyway to prevent the drywall from cracking, so we would have had to pay for the scaffolding, etc. for that anyway.
The cost of the plug-in hybrid is higher than the hybrid and electric cars because we got no subsidy for it. Neither the state of California nor the Federal government was giving out subsidies for plug-in hybrid conversions in 2008 (they since have changed policy and it is now eligible). The subsidies make all the difference, the Nissan Leaf would be around $10K more expensive without the subsidy. Hopefully the need for the subsidy will diminish over time as battery costs decline.
Surprisingly, the solar PV and solar thermal systems are close to the most cost effective. Most commentators rate them as expensive, and rate efficiency measures as more cost effective, but what such commentators are talking about is maybe putting weather stripping around your windows, not removing the walls and putting in more insulation. In reality, you need both. Reducing electricity demand by plugging power vamping appliances into power strips and turning off the appliances on the strip, replacing frequently used lights with CFLs, and buying new, power-efficient Energy Star appliances is necessary to reduce the electricity demand to the point where solar PV can completely offset the demand. Otherwise, the cost of solar PV is too high.
Natural gas use for heating and cooking remains the most difficult carbon generation source to remove. The work we're planning to reduce natural gas use for heating involves quite a disruptive change in our house, essentially replacing the insulation in the thermal envelope, but it will not reduce carbon emissions from that source to zero. We will still need some heat. If we had gone through with our plans to install a geothermal heat pump, the cost would have been even higher, much higher in fact. These considerations point up the carbon cost of our preferred built environment style for family residences in the US: single family housing with all four walls and roof open to the elements. With more multiple family housing, the cost of heating can be reduced substantially, though, of course, at a much higher expense due to the replacement of the existing built environment infrastructure.
The 10% carbon emissions that we can't reduce is about equally split between transportation and heating/cooking: 887 kg for transportation and 1300 kg. for heating/cooking. For now, it seems like we are at the limit of what we can do with current technology and our pocketbook. We need a car to get out of town. We could get a Chevy Volt which has much better gas mileage than the plug-in Prius, but our plug-in Prius works fine so it seems there is no need to buy something new (besides, I have a fondness for Toyota products). And, as mentioned, the cost of removing the heating/cooking carbon emissions from natural gas is simply too high. So, our only choice is to offset our carbon emissions by buying carbon offsets. The graph also shows the cost of buying carbon offsets from CoolIt.org and PG&E's Climate Smart program. In each case, the cost is pennies or fractions of pennies per kg. carbon offset. Carbon offsets are, by far, the most cost effective way to reduce carbon emissions.
Which brings up the interesting question: why not simply buy carbon credits and forget about taking the reduction measures? The reduction measures are from 10x to 100x more expensive. Many commentators are skeptical to negative about carbon offsets, because in the early days of carbon offsetting some projects were scams or would have proceeded anyway even without the offset. But both CoolIt.org and PG&E seem to have credible programs where the projects are solid and specifically designed as offsets, and PG&E's is even tax deductible (tax deduction was not included in the per kg. cost of the figure). If everybody bought offsets and nobody took any real, concrete measures to reduce carbon, we would be left with a built environment and transportation infrastructure that generated exactly as much carbon pollution as today. In reality, as with efficiency and solar PV, you need both concrete reduction measures and offsets. Implement the highest degree of reduction measures you can afford and use carbon offsets to take care of the rest.
Saturday, July 24, 2010
Miscellaneous Items
Looks like the drywall removal is set to start on Monday, a month after the job was supposed to start. But because we removed the geothermal heat pump from the plan, the job should actually complete about two weeks before the original plan. I'm certainly happy that things are finally getting started.
On the other hand, less thrilling is the fact that the US government now has completely and totally abdicated doing anything serious about climate change. The Senate has dropped any attempt at pricing carbon and now is contemplating a few minor changes, primarily around responding to the Gulf oil spill disaster. It's business as usual on the policy front: we are completely on track for the IPCC's Business as Usual scenario in which the world roasts by 2100.
What happened? Obama basically gave up. He could have come out with a strong speech rallying wavering Democrats and even trying to corral a couple of Republicans who have been sympathetic, like Lindsey Graham. But he did nothing. Peculiarly, something similar happened with his ambitious plans to reform NASA. He unveiled plans in February to scale back on Bush's moon program because the plans were so grandiose and the technology being proposed so deficient that the US wouldn't have reached the goal until 2030 if then. The amount of money needed was much larger than the US could afford. His plan was to turn development of Earth to orbit transportation over to the new, entrepreneurial companies that are building rockets more cheaply than the government can. But he failed to push the plans, compromised at the first sign of opposition, and now the House wants to continue the Bush plan but at a lower funding level (practically guaranteeing that nothing will happen) purely as a jobs program.
Is there any commonality in these two occurrences? They both involve policy making about science and technology that require difficult decisions in which some political pain will be involved. In the case of pricing carbon, the price of carbon-based energy will go up. In the case of NASA, government employees will lose their jobs. In both cases, it seems the US government wants an easy political out, like buying an iPod for 400 bucks, rather than the hard and difficult work of making policy that will be expensive but, in the end, will make the country and the world a better place. The problem, particularly with climate change but also with space, is that the physics and economics aren't subject to compromise. For climate, if we continue on the BAU path, the planet will cook, and the only way to get off that path is to make carbon-based energy more expensive. For space, the government's record of technology development over the last 40 years has indicated that it can't develop economical solutions to the problem of getting to orbit. So it's back to where we were 2 years ago with the Bush administration as far as climate change goes.
What might the world look like after 2100 when the oil runs out and the ice caps are melted? An interesting perspective can be found in the science fiction book The Windup Girl (warning: don't follow the link if you don't want the plot revealed) by Paolo Bacigalupi. The book is set in 2100's Bangkok. Energy is supplied by windup springs, biogas, and human and animal labor, plus coal that is carefully rationed to avoid making global warming even worse. Bangkok is kept from flooding by enormous dikes and coal-fired pumps. Since mechanical technology no longer has any energy source to power it, the world has turned to genetic engineering and the results are environmental catastrophes in which most of the world's original biodiversity is gone and has been replaced by genetically hacked organisms. Like all science fiction, this book takes artistic license with the possible reality in order to generate a good, engaging story, but the general setting sounds plausible to me.
I think we can now reasonably concluded that neither the Democratic nor the Republican party are going to do anything about climate change.What will it take to get the government to finally put in place the policy changes needed to stop the world from cooking?
On the other hand, less thrilling is the fact that the US government now has completely and totally abdicated doing anything serious about climate change. The Senate has dropped any attempt at pricing carbon and now is contemplating a few minor changes, primarily around responding to the Gulf oil spill disaster. It's business as usual on the policy front: we are completely on track for the IPCC's Business as Usual scenario in which the world roasts by 2100.
What happened? Obama basically gave up. He could have come out with a strong speech rallying wavering Democrats and even trying to corral a couple of Republicans who have been sympathetic, like Lindsey Graham. But he did nothing. Peculiarly, something similar happened with his ambitious plans to reform NASA. He unveiled plans in February to scale back on Bush's moon program because the plans were so grandiose and the technology being proposed so deficient that the US wouldn't have reached the goal until 2030 if then. The amount of money needed was much larger than the US could afford. His plan was to turn development of Earth to orbit transportation over to the new, entrepreneurial companies that are building rockets more cheaply than the government can. But he failed to push the plans, compromised at the first sign of opposition, and now the House wants to continue the Bush plan but at a lower funding level (practically guaranteeing that nothing will happen) purely as a jobs program.
Is there any commonality in these two occurrences? They both involve policy making about science and technology that require difficult decisions in which some political pain will be involved. In the case of pricing carbon, the price of carbon-based energy will go up. In the case of NASA, government employees will lose their jobs. In both cases, it seems the US government wants an easy political out, like buying an iPod for 400 bucks, rather than the hard and difficult work of making policy that will be expensive but, in the end, will make the country and the world a better place. The problem, particularly with climate change but also with space, is that the physics and economics aren't subject to compromise. For climate, if we continue on the BAU path, the planet will cook, and the only way to get off that path is to make carbon-based energy more expensive. For space, the government's record of technology development over the last 40 years has indicated that it can't develop economical solutions to the problem of getting to orbit. So it's back to where we were 2 years ago with the Bush administration as far as climate change goes.
What might the world look like after 2100 when the oil runs out and the ice caps are melted? An interesting perspective can be found in the science fiction book The Windup Girl (warning: don't follow the link if you don't want the plot revealed) by Paolo Bacigalupi. The book is set in 2100's Bangkok. Energy is supplied by windup springs, biogas, and human and animal labor, plus coal that is carefully rationed to avoid making global warming even worse. Bangkok is kept from flooding by enormous dikes and coal-fired pumps. Since mechanical technology no longer has any energy source to power it, the world has turned to genetic engineering and the results are environmental catastrophes in which most of the world's original biodiversity is gone and has been replaced by genetically hacked organisms. Like all science fiction, this book takes artistic license with the possible reality in order to generate a good, engaging story, but the general setting sounds plausible to me.
I think we can now reasonably concluded that neither the Democratic nor the Republican party are going to do anything about climate change.What will it take to get the government to finally put in place the policy changes needed to stop the world from cooking?
Saturday, July 17, 2010
Projected Carbon Footprint
Since we removed the geothermal heat pump from the system remodel plan, I've recalculated the projected carbon footprint we can expect from our house plus cars next year, after we have the remodeling work completed (hopefully) and have an electric car powered by solar (again hopefully).
The assumptions I'm making are the following:
The chart shows an almost 90% reduction in carbon emissions from the estimated pre-2002 baseline. This includes extra capacity in the new solar PV (around 1131 kg/yr) which the house will not use and will therefore offset some of the natural gas emissions from heating.
Notice that the electricity footprint is now negative because the house is generating more carbon-free energy that it consumes. This offsets the natural gas and gasoline usage. One car will be completely carbon free, since it will run off electricity generated by the sun, but our current plug-in Prius will still require gasoline.
The cost takes into account the federal and state subsidy for the Nissan Leaf, which brings the price below $20,000.
The assumptions I'm making are the following:
- The reinsulation reduces gas usage by 30% below current average (around 350 therms per year for heating). Several years ago, I constructed a spreadsheet model of the house and calculated what the reduction in energy use would be for changing the insulation to closed cell foam. It came out to about 30%. This ignored the floor, which we will have done, and included the kitchen and master suite, which we won't, though the kitchen ceiling is now at R-30 using fiberglass batt.
- The on-demand electric hot water heater provides backup hot water heating in winter so that total hot water gas reduction including solar thermal and backup on-demand electric is 20%. The electric hot water heater will be offset from the solar PV.
- The heat recovery ventilation system is around 800 kwh per year (running in winter only) and is offset by solar PV.
- We swap out our current, 6 year old polycrystalline 165 watt per panel 18 module solar PV system for a new system consisting of 20 Sunpower 315 watt per panel modules.
- The Nissan Leaf which we are hoping to purchase next year uses 0.25 kilowatt-hours/mile and we drive it around 8000 miles per year, which is about what we usually drive our "commuting car" (as opposed to our long distance car which is more like 10,0000 miles per year).
The chart shows an almost 90% reduction in carbon emissions from the estimated pre-2002 baseline. This includes extra capacity in the new solar PV (around 1131 kg/yr) which the house will not use and will therefore offset some of the natural gas emissions from heating.
The contributions from each component (electricity, gas, and cars) to the total household footprint can be seen in this graph:
Notice that the electricity footprint is now negative because the house is generating more carbon-free energy that it consumes. This offsets the natural gas and gasoline usage. One car will be completely carbon free, since it will run off electricity generated by the sun, but our current plug-in Prius will still require gasoline.
Finally, the bottom line: the cost. The following graph shows the cost per kg carbon eliminated:
The cost takes into account the federal and state subsidy for the Nissan Leaf, which brings the price below $20,000.
The efficiency measures here are the most expensive. Reinsulating the house requires taking off the drywall, blowing in closed cell foam insulation and otherwise sealing up any air leaks, putting back the drywall, and installing a ventilation system to ensure that the house gets enough fresh air in the winter when the windows are all closed. This is expensive and disruptive work, but, unfortunately, there is no way around it if we want to reduce the energy use due to heating.
So by the time we finish next year, we should have achieved almost 90% reduction beyond the estimated pre-2002 baseline. Environmental groups are calling for an 80% reduction by 2050, and this is the aspirational target for governments, though, the steps they've been taking are laughable so far. We will have beat the deadline by almost 40 years. The house and cars will not be total net zero energy, but they will be as close as we can get them, given:
- We need some way to get out of town with the car, and gasoline or diesel are the only realistic fuel choices right now. We could do an under the table conversion of the plug-in Prius to E85, but unfortunately there is very little E85 available in California.
- We have little choice with the heating but to continue using natural gas. The complexity of installing a geothermal heat pump doesn't match the architectural configuration of this house. The house simply does not have enough room for the complex machinery. And the cost of a geothermal heat pump is far and away above the value it provides (something like $700 per kg of carbon eliminated). The amount of money we'll have put into the house for the upgrades even without the geothermal heat pump probably exceeds the resale value, not that we are thinking of selling it of course. Green remodeling does not yet pay in terms of resale value, at least according to a friend who is in real estate. As for cooking, continuing to use a gas stove is a choice: we both prefer gas to electric, and the existing gas stove is still in pretty good condition so we don't see any point in replacing it.
Now, I wish the contractors would finally get started on our system remodel! We are still waiting on a second bid for the drywall removal.
Saturday, July 10, 2010
Or Perhaps Not
We've been moved into the back bedroom and kitchen now for two weeks and the job still hasn't started due to unforseen complications. These are, of course, the bane of any remodelling project, but we seem to have them early and often.
As a consequence, we've decided to make a couple of changes in the plans. We will not put in a geothermal heat pump and we will not put in the skylight in the living room. I dearly wanted the geothermal heat pump and The Lovely Wife dearly wanted the skylight. So we both don't get what we really wanted, but, on the other hand, we may end up having a more successful experience.
The problem with the geothermal heat pump is that it is a complex and expensive technology which, as far as I can tell, is really not yet mature. For example, it requires a water storage tank that stores 6 gallons of heated or chilled water per ton of conditioning. Such a buffer is an invitation for energy loss, as you can see from my post last year on our solar thermal hot water system. The reason for this buffer is because the pump can't handle cycling two 300 foot columns of fluid over multiple short periods without possibly burning out sooner than it otherwise would. In colder climates, the buffer isn't needed because the pump stays on longer. But nothing I read in the literature about geothermal heat pumps indicated the need for such a tank. Besides the energy loss, it also takes up space in our garage. We already have a 80 gallon tank for our solar hot water heater, I don't see much point in another, or, more precisely, if we had known about this we could maybe have figured out how to integrate the two.
Another indication of the immaturity is that we will need two ventilation systems, one for the air conditioning from the heat pump and one for the heat recovery ventilation. This is a needless amount of waste. A properly designed ventilation system would have a heat exchanger built into the air handling system for the air conditioning, so that fresh air could be brought in from outside rather than recirculating stale air. In winter, when the radiant heat in the floor is on, the air handler would bring in fresh air and recover the heat without actually heating the incoming air. Now, the heat recovery ventilation and air conditioning are two separate systems, making them more expensive and more complicated to install, because essentially two separate sets of ducting are needed.
The complexity also leads to a certain amount of uncertainty. For example, suppose the drilling for the geothermal wells runs into a rock 100 feet down. We would have to drill another well to fill out the additional 200 feet (required depth is 300 ft.). But our driveway is not very big, so we might end up not having space, or having to go into the front garden. Of course, the cost would then skyrocket and there would be more delay. We (and especially The Lovely Wife) have very little tolerance for things going wrong, especially when they might run up the bill.
So we've decided to focus on securing the thermal envelope of the building so that it doesn't leak heat and air. This will require the heat recovery ventilation but that is relatively energy efficient and should not require too much in the way of installation. Not putting in another skylight (we already have 5) will help, since skylights are essentially R-3 holes in the R-30 insulation of the roof. We had planned for the skylight to have had a thermal shade, and we are also planning on putting thermal shades on the three existing ridge skylights to stop them from acting as radiators of heat into the sky at night in winter because they are so high up on the roof, but even with a thermal shade there would likely be more heat radiated out than if the roof is left intact.
On a more philosophical level, I recently returned from a business trip to Berlin, and had David Owen's book Green Metropolis along. Owen's thesis is that fancy technology, such as geothermal heat pumps, isn't the answer to climate change. The answer is a denser built environment. He believes that New York is, in effect, the greenest city in the US because driving is so unpleasant that people must take mass transit and walk, and the density of dwellings allows less energy for indoor conditioning. The message really struck home in Berlin, where my hotel was within walking distance of scores of great restaurants and the Ku Damm, which had lots of shopping. On the other hand, the hotel itself was a small European hotel without air conditioning and the temperatures were in the mid-90's with almost 100% relative humidity making the indoor temperature very uncomfortable especially at night, so there are downsides to the European style of building too. After my stint on the local Sustainability Task Force two years ago, I actually came to share Owen's opinion about density, but the barriers to making a denser built environment in the US are daunting. Practically every attempt to densify in our suburban town runs into a buzz saw of opposition from existing property owners. Given a choice, people really don't want to live close enough to their neighbors and shops that they can walk, they are perfectly happy using the car. In any case, thinking over our own efforts to reduce our carbon footprint while still living in a largely suburban built environment re-enforced the idea that we should rather concentrate on energy efficiency than fancy renewable energy technology, even if, in the end, our efforts were less effective than if we were to live in a denser built environment like New York.
And now for some "eye candy" after a somewhat depressing batch of text:
On the train from Berlin to Frankfurt, kilometer after kilometer of wind turbines outside the window as we pass. The Germans are really serious about renewable energy, unlike us lazy Americans.
As a consequence, we've decided to make a couple of changes in the plans. We will not put in a geothermal heat pump and we will not put in the skylight in the living room. I dearly wanted the geothermal heat pump and The Lovely Wife dearly wanted the skylight. So we both don't get what we really wanted, but, on the other hand, we may end up having a more successful experience.
The problem with the geothermal heat pump is that it is a complex and expensive technology which, as far as I can tell, is really not yet mature. For example, it requires a water storage tank that stores 6 gallons of heated or chilled water per ton of conditioning. Such a buffer is an invitation for energy loss, as you can see from my post last year on our solar thermal hot water system. The reason for this buffer is because the pump can't handle cycling two 300 foot columns of fluid over multiple short periods without possibly burning out sooner than it otherwise would. In colder climates, the buffer isn't needed because the pump stays on longer. But nothing I read in the literature about geothermal heat pumps indicated the need for such a tank. Besides the energy loss, it also takes up space in our garage. We already have a 80 gallon tank for our solar hot water heater, I don't see much point in another, or, more precisely, if we had known about this we could maybe have figured out how to integrate the two.
Another indication of the immaturity is that we will need two ventilation systems, one for the air conditioning from the heat pump and one for the heat recovery ventilation. This is a needless amount of waste. A properly designed ventilation system would have a heat exchanger built into the air handling system for the air conditioning, so that fresh air could be brought in from outside rather than recirculating stale air. In winter, when the radiant heat in the floor is on, the air handler would bring in fresh air and recover the heat without actually heating the incoming air. Now, the heat recovery ventilation and air conditioning are two separate systems, making them more expensive and more complicated to install, because essentially two separate sets of ducting are needed.
The complexity also leads to a certain amount of uncertainty. For example, suppose the drilling for the geothermal wells runs into a rock 100 feet down. We would have to drill another well to fill out the additional 200 feet (required depth is 300 ft.). But our driveway is not very big, so we might end up not having space, or having to go into the front garden. Of course, the cost would then skyrocket and there would be more delay. We (and especially The Lovely Wife) have very little tolerance for things going wrong, especially when they might run up the bill.
So we've decided to focus on securing the thermal envelope of the building so that it doesn't leak heat and air. This will require the heat recovery ventilation but that is relatively energy efficient and should not require too much in the way of installation. Not putting in another skylight (we already have 5) will help, since skylights are essentially R-3 holes in the R-30 insulation of the roof. We had planned for the skylight to have had a thermal shade, and we are also planning on putting thermal shades on the three existing ridge skylights to stop them from acting as radiators of heat into the sky at night in winter because they are so high up on the roof, but even with a thermal shade there would likely be more heat radiated out than if the roof is left intact.
On a more philosophical level, I recently returned from a business trip to Berlin, and had David Owen's book Green Metropolis along. Owen's thesis is that fancy technology, such as geothermal heat pumps, isn't the answer to climate change. The answer is a denser built environment. He believes that New York is, in effect, the greenest city in the US because driving is so unpleasant that people must take mass transit and walk, and the density of dwellings allows less energy for indoor conditioning. The message really struck home in Berlin, where my hotel was within walking distance of scores of great restaurants and the Ku Damm, which had lots of shopping. On the other hand, the hotel itself was a small European hotel without air conditioning and the temperatures were in the mid-90's with almost 100% relative humidity making the indoor temperature very uncomfortable especially at night, so there are downsides to the European style of building too. After my stint on the local Sustainability Task Force two years ago, I actually came to share Owen's opinion about density, but the barriers to making a denser built environment in the US are daunting. Practically every attempt to densify in our suburban town runs into a buzz saw of opposition from existing property owners. Given a choice, people really don't want to live close enough to their neighbors and shops that they can walk, they are perfectly happy using the car. In any case, thinking over our own efforts to reduce our carbon footprint while still living in a largely suburban built environment re-enforced the idea that we should rather concentrate on energy efficiency than fancy renewable energy technology, even if, in the end, our efforts were less effective than if we were to live in a denser built environment like New York.
And now for some "eye candy" after a somewhat depressing batch of text:
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