this old house

"My building has every convenience
It's gonna make life easy for me
It's gonna be easy to get things done..."

-- "Don't Worry About the Government," Talking Heads

I was in Berkeley, California, this weekend to attend a conference on the physics of sustainable energy sponsored by the American Physical Society (with the added bonus of getting to meet Chris Clarke, who writes one of my favorite blogs: Creek Running North). I drove up from Santa Barbara Friday afternoon in my shiny red Prius. It fits right in here among all the "Greenies." Let the naysayers knock the Prius if they must, but thanks to the onboard computer and real-time graphical display, I'm now hyper-aware of how much energy I consume by driving, and how much even tiny changes in design, behavior or terrain/environmental conditions can result in big savings (or big losses) over the long haul.

For instance: Accelerate gradually, and you'll use slightly less energy than if you put pedal to the metal in a vain attempt to go from 0 to 60 in a few seconds. In general, the faster you go, the more energy it takes to maintain that speed, so driving just at (or slightly under) the speed limit can also result in energy savings. Driving uphill uses more energy than coasting downhill (any avid bicyclist could tell you that much), and driving into a high wind uses up more gas than driving with the wind at your back. (This is also why it takes less time to fly cross-country going East to West, than it does going West to East.) Don't even get me started on what a 10-hour drive from Salt Lake City to LA in gusting crosswinds through the mountain pass did to my average miles per gallon. (*shakes fist impotently at sky*) Damn you, Nature!

As I wrote when I first bought the Prius last year (after two decades of not owning a car at all), the key to the car's efficiency lies not in one big technological breakthrough -- although that would certainly be nice! -- but in a series of incremental improvements in the overall design of the "system": lighter materials to reduce overall weight (so less energy is required to get the car moving); a braking system that recovers as much wasted heat energy as possible; and using the energy recovered from the brakes and from the motion of the wheels to keep the battery juiced, for example. It's not a perfect design -- there are lots of hidden costs, such as importing some of the raw materials, and those are reflected in the sticker price. There's loads of room for further improvement, but it's a start. For the kind of driving I do in Los Angeles, it's an excellent choice. Plus it provides a handy segue into one of the prevailing themes of this weekend's conference: adopting a systems-based design strategy to eke out every last bit of energy efficiency in our buildings (residential and commercial), industrial complexes, cars and so forth.

We don't really think of a building as an energy system; frankly, even physicists don't spend a great deal of time considering the basic physics of buildings. David Hafemeister (CalPoly), one of the conference organizers, has given the issue of heat transfer in his home a great deal of thought, bemoaning the fact that "We no longer teach such practical things in physics." His talk walked us through an increasingly elaborate calculation of his home's heating needs, trying to take into account a dizzying number of variables (square footage, ceiling height, inevitable thermal losses, local climate, double-paned windows, air ducts, furnace efficiency, body heat given off by inhabitants, etc). I learned a fascinating fact: there is a "free temperature" effect, in which it is 3 degrees F warmer inside the house than it is outside. Based on Hafemeister's calculations, this means that no furnace heating is needed to maintain an indoor temp of around 65 degrees F until the outside temp hits 35 degrees F.

[UPDATE: my notes were unclear, and thus so was the above sentence. It should read: "Based on Hafemeister's calculations, this means that no furnace heating is needed to maintain an indoor temp of 68 F until the outside temperature hits 65 F. If the internal heat is doubled (more people and more electronics) and the total insulation is increased by a factor of five in a super-insulated house, then the furnace won't go on until it is 35 F outside."] That's not likely to happen in southern California, but people in Michigan, take note!

All those factors combine to determine a home's total energy usage -- ergo, it's a system. And just like the Prius, small incremental improvements in energy efficiency in a building "system" can add up significantly over time. Just ask Danny Harvey of the University of Toronto, who spent years developing climate change models before turning his attention to building efficiencies. After all, he reasoned, in developed countries, buildings account for as much as one-third of energy-related greenhouse gas emissions. Much progress has been made on maxing the efficiency of individual devices commonly found in structures: pumps, motors, fans, heaters, chillers, lighting, air ducts, major appliances, and so forth.

But Harvey maintains that putting them all together in the most optimal way could result in systems-level savings many times higher than what can be achieved if we simply continue to address just the individual components. Take your standard heat pump technology, designed to transfer warm air to cooler air. There are some fundamental physical limits to how efficiency the heat pump can be; thermodynamics is a harsh mistress. But Harvey found that by cutting the flow rate through ducts or pipes in half, he could reduce the electricity needed by a factor of 6 or 7. There's always a trade-off, of course, in this case, a slight loss in efficiency -- otherwise, there might be a reduction by a factor of 8. It's still a considerable savings, and worth the tradeoff in efficiency. No wonder he advocates an integrated design process for future urban planning, complete with computational fluid dynamics modeling. The couple who designed and built the Florida Solar Cracker House near Interlachen would agree. The link is to their Website, detailing everything they did to use as little fossil fuels, and be as energy efficient, as possible.

Lighting is another big energy suck in homes, office buildings, and urban areas (street lights, etc), consuming 22% of all the electricity produced in the US. We could realize huge savings by investing the capital needed to install solid state lighting, i.e., light-emitting diodes. That's a technology whose time has come, frankly, thanks to some major breakthroughs in recent years to improve efficiencies and produce white LEDs with the same broad spectrum as conventional incandescent bulbs, making them commercially viable for the first tie.  Right now, researchers are getting 152 lumens per watt with efficiencies between 65% and 85%; by 2012, they think they can reach 280 lumens per watt with 90% efficiencies. At those levels, a solid state lighting system would pay for itself within a couple of years; right now, it takes about five years to recoup the capital investment.

The problem is, they're still pretty expensive, in part because they're made using the same clean-room fabrication techniques used for semiconductor wafers. But LEDs are already a $2 billion a year market. Look around you and you'll see them in all kinds of consumer niche applications: flashlights, cell phone displays, street signage, and several cities are using them in street lights and for the red and green portions of traffic lights. The film and TV industry is very interested in white LEDs because they don't generate heat -- the actors don't have to sweat under hot lights. And spectrally, they're very pure, unlike fluorescent light, which we all know makes us look a bit pale and jaundiced. Nor do they emit UV light, making them ideal for museums (UV light can damage paintings).

All the talk about optimization called to mind one of talks presented at the American Association of Physics Teachers meeting a month or two ago. Students at Issaquah High School in Washington state were on hand with their teacher, Thomas Haff, to present their rather ingenious solution to all that wasted hot water that disappears down the drain during our morning showers. Specifically, they designed a prototype holding tank that stores hot waste water until the heat is dissipated throughout the house, there by cutting down on heating costs.

Haff broached the problem to members of the Student Energy Conservation Group, but he first got the idea 10 years ago, when he spent a year living in rural Japan. Barely 50% of the population there had flush toilets in their home; they relied instead on built-in indoor outhouses (I know, it seems like an oxymoron). These were little more than holding tanks equipped with fans to (ahem) vent the methane and any excess heat out of the house. Once a month the truck would drive through the area and pump out the accumulated waste. (Jen-Luc Piquant thinks that is the ultimate suck-y job.) His first few years back in the US, he lived in a home with no heat in the bathroom, and took to leaving the hot water in the tub after his kids took their baths until it reached ambient room temperature -- a nifty way to solve the bathroom heating problem. And he thought it should be possible to literally collect the waste water from hot showers and use it as a heating source. "People tend to forget that heat is energy," he told me.

That's where Haff's students came in. First they had to determine their basic parameters. Just how long does it take hot water to travel from showerhead to drain? Between five and 15 seconds. Within a minute, all the hot water has entered the municipal waste stream. (Many cities, like Seattle, recycle waste water, but to my knowledge, there's no widespread system anywhere to recapture the wasted heat in that water.) Then they had to determine values for how much water is used during the average shower, starting and ending temperatures of the water collected, and so forth. They then devised a mathematical model and tested it experimentally in the lab. The model and the data matched perfectly. Science! It works!

Their apparatus is a fairly simple design, based on Haff's vision of a holding tank. The tank is made of galvanized steel that fits neatly between the walls of a building. Instead of flowing directly out of the house, hot water from the shower drains into the holding tank. A thermometer monitors the temperature, and when it hits a certain level, the system opens a solenoid valve -- just like those used in dishwashers and sprinkler systems -- which allows the heat to dissipate through the house. You can add vents and blowers and such to the basic passive system to speed the rate of dissipation, but you'll lose some of the benefits, because doing so would reduce the overall efficiency of the system (those add-ons require energy to operate). Haff is now looking into scaling up the prototype for real-world use on a much larger, commercial scale.

See what a systems approach can do for you when it comes to optimizing energy efficiencies? Heck, just unplugging all your "vampire appliances" could result in significant savings to your energy bill, and substantially less carbon emitted into the atmosphere as a result. We're all part of the global energy system, after all.

IMPORTANT REMINDER:

June Cleaver sez SAVE THE DATE! March 14 is the first annual Talk Like a Physicist Day!

Comments

[eingram]

I'm confused. I don't mean to be picky, but I thought the major jet streams flowed west to east, thus aiding easterly flights.

[Jennifer Ouellette]

No, I'm confused. I can never remember which way I gain time. :) Thanks for the correction.

[Peter Morgan]

The Prius certainly seems to be the best production hybrid car ever, but I was primed by the following comment, from a BBC News story today about an experimental hybrid sports car, at http://news.bbc.co.uk/2/hi/technology/7265267.stm, "Hybrid cars already use regenerative braking - normally it restores about 10% of the energy, ... Lifecar is aiming for 50%." to question your claim that the Prius has a "braking system that recovers as much wasted heat energy as possible" (my emphasis). Googling "Prius braking energy" got a few interesting sites (the first two, "http://privatenrg.com/" and "http://thuledingles.com/?p=163" seemed worth a look to me; I particularly liked the latter's account of "prius rage" against drivers who drive very conservatively), but not immediately any info on the efficiency of the Prius's restoration of braking energy.

On buildings, the 1920s Condo I live in has been working on our steam heating, to little avail on efficiency. I believe we would have to convert the existing system to hot water instead of steam, at a cost of over $100K and considerable disruption that none of the owners want to undertake. Getting real savings without knocking down all the old buildings in the country seems very difficult.

[eingram]

No worries, mate about the time confusion. maybe you were remembering that you actually span 4 time zones from NY to LA (or any west coast locale)

[Jennifer Ouellette]

"As much energy as possible" for the design of the Prius, was my point. Obviously the technology is still improving. I would HOPE that the Prius braking system, as well as its other features, are continuously being improved upon, both by Toyota and other manufacturers. "Prius rage" is a behavioral problem that is not limited to the Prius... it annoys me that I can be going 75 MPH in a 65 MPH zone -- hardly driving conservatively -- and STILL have drivers tailgating me impatiently because I'm too damned slow for them. Clearly, "speed limit" does not mean what I think it means. :) At any rate, traffic in LA is so bad, that this is only an issue on road trips. Generally, I hit an LA freeway and find traffic moving at a steady 45 MPH or thereabouts. If it slows down to a steady 35 MPH, I get KILLER gas mileage (around 70 MPG if I time things right). Let the road ragers vent their spleen; I get the last laugh. Like I said, I used to be one of those drivers. The Prius has made me much more aware of the raw energy costs of locomotion. Maybe road ragers should be forced to drive a Prius for a month or two. :)

As for very old buildings -- I owned a 1918 condo myself when I lived in DC, so I hear you on the cost of retrofitting. The point I was trying to make is not that any one person needs to realize "considerable" savings, but that tiny improvements, changes in behavior, and so forth can add up rather quickly. If everyone in the world unplugged their vampire appliances when they weren't using them, that would have a significant impact on carbon emissions into the atmosphere.

ALthough at some point, the situation could become serious enough where that $100K investment (and more) might be well justified, even key to survival. In the meantime, why not try to squeeze out as much efficiency as we can, weighing the cost and inconvenience against the very real gains to be made? A recurring theme at the conference was that there is no "silver bullet" -- rather, it's more like "silver buckshot." :)

[Deepish Thinker]

"In general, the faster you go, the more energy it takes to maintain that speed, so driving just at (or slightly under) the speed limit can also result in energy savings."

The faster you drive the more power (energy per unit time) is required to maintain your speed. Of course it also takes you less time to get from A to B.

There is a trade off between power required and distanced covered. Beyond a certain point slowing down will actually reduce overall fuel efficiency as the increased time required to travel a given distance will outweigh the reduced rate of fuel burn. In other words, an hour at 60mph will probably burn less fuel than two hours at 30mph.

The optimum travel speed will vary from car to car. Fancy cars, like say a Prius, have fuel flow meters that allow the driver to determine by experiment the speed that yields the best gas mileage. Less fancy cars sometimes have their most efficient speed printed in the handbook.

For the rest of us, 60mph or maybe a little bit less is probably not a bad guess. The important thing is that we don't want those hippie types out there getting the idea that cruising the freeway at 30mph will save the planet. Not only is it annoying, it's probably counterproductive.

[Chris Clarke]

The important thing is that we don't want those hippie types out there getting the idea that cruising the freeway at 30mph will save the planet.

Not to worry: their kind is suffering attrition proportional to the attrition of 1960s-era VW vans. Sadly, the cell-phone talkers are picking up their slack.

It was wonderful getting together, Jennifer. With Sean next time!

[Jon H]

I think mileage readouts should be required to be standard on all cars, and there should be a tax credit for having one installed on late model cars.

Having that display of instantaneous and average MPG really does increase your awareness of how driving style and mileage are connected. Totalling up your mileage when you refill the tank just doesn't cut it.

I think this would really help people reduce their gas usage.

[Jon H]

"There is a trade off between power required and distanced covered. Beyond a certain point slowing down will actually reduce overall fuel efficiency as the increased time required to travel a given distance will outweigh the reduced rate of fuel burn."

I think a lot of wasted gas happens when people gun their engines when the light turns green, or when they keep on the gas and then brake at the last minute rather than gradually slowing to a stop.

A mileage readout really makes this obvious.

[merce]

"Based on Hafemeister's calculations, this means that no furnace heating is needed to maintain an indoor temp of around 65 degrees F until the outside temp hits 35 degrees F." I give up. This 'free heat' is supposed to result in a 3 degree difference between indoor and outdoor temperatures, according to the sentence that precedes this one, but this example represents a 30 degree difference. 3 degrees is an insignificant amount of temperature difference, really - it probably represents some primitive level of insulation, but 30 degrees seems in violation of the second law of thermodynamics. What is the story here?

[Jennifer Ouellette]

Honestly, the calculations were difficult to follow, with lots of variables, and I'm not entirely convinced about this "free heat' thing anyway. Ergo, the lack of details. Mostly, I liked the fact that Hafemeister had bothered to run so many calculations on heat transfer in his house. Should he post his slides somewhere in the near future, containing the gory details, I'll link to it with an update....

[Steve McChesney]

As an automotive engineer, historic vehicle racer, and an avid "car guy" I will say this:

There will be no signifigant improvement in the total efficiency of automobiles until ...

the elimination of testosterone.

There, I said it. Doubleplusthink carbon offset credits to me.

-steve

[Jennifer Ouellette]

Steve, your comment is amusing, and no one denies the influence of testosterone, but I've never bought into the notion that testosterone excuses aggressive behavior -- any more than I buy into the notion that PMS excuses bad behavior by women. We are influenced, not RULED, by our hormones. We are still responsible for our choices and actions.

There. I said it. TRIPLEplusthink carbon offset credits to ME. :)

[BobP]

"We no longer teach such practical things in physics."

Aaah, but the principles are still taught. Further, somewhat north of the Physics Department, in Etcheverry Hall, the Mechanical Engineering Department spends a fair amount of time worrying about it...

[Porlock Hussein Junior]

I am very confused.

"Take your standard heat pump technology, designed to transfer warm air to cooler air. There are some fundamental physical limits to how efficiency the heat pump can be; thermodynamics is a harsh mistress. But Harvey found that by cutting the flow rate through ducts or pipes in half, he could reduce the electricity needed by a factor of 6 or 7. There's always a trade-off, of course, in this case, a slight loss in efficiency -- otherwise, there might be a reduction by a factor of 8."

If I didn't know that was written by a physicist, I'd figure it was the product of erious ignorance. (Cf. Jane Harman: she who celebrated a law that will get rid of those notoriously inefficient [her words, at least in essence] 100-watt bulbs. Perhaps she should find out what "efficient" means, and read some labels and learn to do division and compare the output per unit input for different sizes of incandescent bulb. Bah! But I digress.)

OK, so it uses 6 to 7 times less electricity, and it's less efficient? That means it produces 8 (or more) times less output??? Not necessarily a desirable result. No, that can't be it.

So what does it mean? Efficiency here is computed as what over what? And does either "what" relate to the massively reduced electrical input?

I know there's a good answer to this, just can't figure it out.

[Rich A]

Regarding your comment on LED lighting, as used in street lights or traffic lights, there is a serious reliability issue here.
In two local cities, all the stop lights have been replaced with LED lights.
Over the last 4 years or so I have observed really huge failure rates of LEDs going dark. That is, of the 100 or so LEDs making up one red light, one to
1/3 of the total LEDs will just go dark, kind of randomly.
Over the course of 12 months after an install, I guesstimate that any
given intersection has at least one red light with significant burnouts.

The burned out lights look quite dilapidated. It is like looking at a building
with broken windows. You notice it is basically working, but why all the
dark lines and spots? It looks broken down.

Now I doubt the LEDs themselves are failing at this rate. More likely
an environmental factor, such as the physical mounting and electrical contact
of the LEDs, perhaps.

I would say the LED lights must really be expensive with such failure rates.
Further the mfg should be providing free replacements for every burnout,
so that increases costs too.

FYI, Rich