I have a confession to make. When we moved into our current house three years ago, we had to sell our clothes dryer due to gas/electric incompatibility (happens every time we move!). So we lived without a dryer for three years, hanging clothes out to dry, and generally being frugal about washing vs. re-wearing clothes. Well, after several weather-induced trips to the laundromat this winter, we (or can I lay this all at my wife’s feet?) finally broke down and bought a used washer/dryer set on Craigslist. We’ll still let the sun dry our clothes 95% of the time, but have other options now.
Even though this little vignette does relate to the common Do the Math theme of low-energy lifestyles, the actual point of bringing it up is that the washer/dryer came from a house that had just been on display as a model for energy efficiency—including the washer and dryer. At the house, we met Jason Beckman, of Classic Residential, Inc., who had carried out many of the efficiency upgrades to the house. I thought it would be instructive to have him perform an energy audit at our home—especially a blower door test to expose ventilation issues.
As a bonus, after the nominal audit activities were over, I was able to spend some quality time with the blower door, doing extensive tests in virtually every room in the house. What I found was certainly instructive for me, and hopefully will be useful to a broad audience as well.
If you want to make your house more efficient at repelling the unpleasantness outdoors (whether hot or cold), what should you do first? Insulate the walls? Insulate the ceiling? The roof? Better windows? Draft elimination? What has the biggest effect? While I have regrettably little practical experience tightening up a house (it’s on my bucket list), I at least do understand heat transfer from a physics/engineering perspective, and can walk through some insightful calculations. So let’s build a fantasy house and evaluate thermal tradeoffs at 1234 Theoretical Lane.
When it comes up in casual conversation that I do not generally heat or cool my house, people either move to another seat or look at me with some mixture of admiration and disbelief. When non-Californians then find out that I live in San Diego, they might huff or spew, which often involves some embarrassing projectile escaping their mouth. But the locals are more consistently impressed—more so by my forsaking heat than AC (San Diego has very mild summers by U.S. standards). This summer, I turned on the AC for the first time since we bought the house three years ago. All in the name of science! I was blown away. Here is what I learned.
Part of the argument that we cannot expect growth to continue indefinitely is that efficiency gains are capped. Many of our energy applications are within a factor of two of theoretical efficiency limits, so we can’t squeeze too much more out of this orange. After all, nothing can be more than 100% efficient, can it? Well, it turns out there is one domain in which we can gleefully break these bonds and achieve far better than 100% efficiency: heat pumps (includes refrigerators). Even though it sounds like magic, we still must operate within physical limits, naturally. In this post, I explain how this is possible, and develop the thermodynamic limit to heat engines and heat pumps. It’s a story of entropy.
Ever wonder how efficient it is to heat water? Of course you have! Ever measured it? Whoa, mister, now you’ve gone too far!
I recently devised a laser-phototransistor gauge to monitor my natural gas meter dial—like ya do. As a side benefit, I acquired good data on how much energy goes into various domestic uses of natural gas. Using this, I was able to figure out how much energy it takes to heat water on the stove, cook something in the oven, or heat water for a shower. Together with the knowledge of the heat capacity of water, I can compute heating efficiency from my measurements. What could be more fun? I’ll share the results here, some of which surprised me.
Infrared image of a cold left foot (25°C with 19°C toes), compared to a warm (33°C) right foot.
One of the more bothersome aspects of living in an unheated house (with tile floors in much of the house, in my case) is having cold feet. Spring has arrived, so perhaps this post is not as timely as it might otherwise have been. But let’s consider the energy costs of various approaches to warming up cold feet.
The main problem I have with cold feet is that they make it hard to go to sleep. Otherwise cold feet don’t seem to distract me from normal activities. But let’s say that your feet are cold and that you cannot stand it any longer, and therefore must warm them up. I’ll look at a number of options, assessing how much energy is consumed for each. We’ll try hot water in the sink, a space heater (or blow dryer) under a blanket, a heating pad wrapped around the feet, or good-old metabolic energy.
If you are on-board with the sentiment that we should strive to reduce the amount of energy we consume as a means to relieve pressure on a world suffering impending energy scarcity, then you probably want to know how one might proceed. In this post, I will describe the single-biggest energy-saving strategy I have employed in my home in the past five years, which slashed my natural gas consumption by almost a factor of five.
Last week, I described how to read gas meters, in the process discovering how onerous pilots lights can be. As a result of initial exploration of my energy footprint in the spring of 2007, I shut off the furnace pilot light for the summer, which I figured accounted for two-thirds of my warm-season natural gas use. When winter came, my wife and I challenged ourselves to hold off on re-igniting the pilot light until it got too cold for us to bear. That day never came. The result was a dramatic reduction in natural gas use.
In this post, I will talk about some of the ups and downs of adjusting to a colder house in the winter. Granted, we live in moderate San Diego, and could not get away with the same tactic in many locales. Even so, I will quantify the gains one might expect elsewhere for similar living conditions.
Who hasn’t enjoyed heat from the sun? Doing so represents a direct energetic transfer—via radiation—from the sun’s hot surface to your skin. One square meter can catch about 1000 W, which is comparable to the output of a portable space heater. A dark surface can capture the energy at nearly 100% efficiency, beating (heating?) the pants off of solar photovoltaic (PV) capture efficiency, for instance. We have already seen that solar PV qualifies as a super-abundant resource, requiring panels covering only about 0.5% of land to meet our entire energy demand (still huge, granted). So direct thermal energy from the sun, gathered more efficiently than what PV can do, is automatically in the abundant club. Let’s evaluate some of the practical issues surrounding solar thermal: either for home heating or for the production of electricity.
The Earth started its existence as a red-hot rock, and has been cooling ever since. It’s still quite toasty in the core, and will remain so for billions of years, yet. Cooling implies a flow of heat, and where heat flows, the possibility exists of capturing useful energy. Geysers and volcanoes are obvious manifestations of geothermal energy, but what role can it play toward satisfying our current global demand? Following the recent theme of Do the Math, we will put geothermal in one of three boxes labeled abundant, potent, or niche (puny). Have any guesses?