E-mail Sherry Listgarten About this blog: Climate change, despite its outsized impact on the planet, is still an abstract concept to many of us. That needs to change. My hope is that readers of this blog will develop a better understanding of how our climate is evolving a... (More) About this blog: Climate change, despite its outsized impact on the planet, is still an abstract concept to many of us. That needs to change. My hope is that readers of this blog will develop a better understanding of how our climate is evolving and how they want to respond, and will feel comfortable asking questions and exchanging comments on the topic. It is important that we develop a shared understanding of the basic science and impacts of climate change, to make sense of our actions and policy options going forward. My background is not in climate science, and I'm not even particularly green; my hope is that helps to make this blog more relatable. I studied math and neurobiology on the east coast before moving out here in 1987 for grad school in computer science. After working in the tech industry for about 25 years, I retired a few years ago to better align my time with my priorities. I love spending time outdoors, and feel deeply our responsibility to this incredible planet that we call home. (Hide)
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The individual units shown in pictures 5 & 6 are used in many motel rooms. Dual heat & AC settings. Is the heater/AC/front windshield defroster used in automobiles basically the same concept but smaller? The mini-split design for separate rooms has been around for a long time.
@ R.Cavendish In gasoline cars, the heater is providing waste heat from the engine (that's why my Prius' heater takes a couple minutes in the morning to heat up). And the car "AC" is providing cooling by running a one-way chiller compressor with on-board mechanical power or on-board electrical power. The heat pumps in the blog are different because they all use electrically driven two-way "air conditioners" that extract heat from yard air in the winter, and extract heat from the building in summer. They are efficient because their advanced design lets them use one unit of electrical energy to gather 2 or more units of heat energy and move all 3 or more units of total energy (as heat) into the home in winter, or out of the home in summer.
Great minds think alike. @Sherry, While you were writing this week, so was Ian Bogost for the Atlantic in this article explaining the heat pumps and the "electrification movement". Web Link He mentions how heat pumps are a no brainer for California homes as their gas furnaces need replacing or as the the homes start wanting cooling from a two for one device.
We have a detached, finished garage (400 sq ft) converted to an exercise studio, and it is now conventionally gas-heated and window-ac-cooled. I'm thinking of putting in a heat pump. But we only heat and cool the space when we are about to be using it, so in the winter this means bringing it up 5-10 degrees, and summer it means bringing it down about 5 degrees. All for about an hours' exercise time. Is this a good use for small heat pumps? We have a heat pump system in the house, and it seems to be most efficient if we keep the temp pretty constant. Suggestions welcome.
@John, that's a great question. I'm not an expert, but my guess is (1) you would need to turn the heat pump on a few hours before you were going to use the gym; and (2) the heat pump would run longer but not use more energy than your gas furnace or A/C because its output is smaller. So I think it would be an okay fit if you were able to turn it on a while before you use the room.
Lets not headline killing birds. They are having enough trouble with climate change,cats, and humans.
How noisy are these units? Traditional in-window air conditioning units can be quite loud - extending that noise to a constant presence year round might not be a welcome change. There are lots of resistive electric and natural gas heating solutions whose output is not measured in Decibels.
@fixate: Great question! I got to listen to several of the mini-splits (inside and out), and I asked almost everyone I spoke with about the sound. Universally they all seemed kind of surprised I was even asking because there is so little sound. The sound is louder the more work they are doing (they have variable speed motors), but it's fair to say these are much quieter than a typical fan and it's common to not even be sure it's on. The sound from a mini-split is nothing like an in-window A/C. I haven't listened to the all-in-one versions though (see footnote 1). @Valerie: Ugh, you are right. Especially with birds so active right now. If you come up with a great alternate headline, I'll change it!
We built a 300 sq ft ADU in our backyard, and heat/cool it with a mini-split - it works quite well. As it is used as an office, we don't have the heat pump on a lot of the time, including most nights - adding very little cost. It was the most affordable choice to install, as we didn't want to have a separate heater. The installer didn't make it leak proof the first year, unfortunately, so they had to seal it up and add more coolant after only a year. Otherwise, it's very effective and quiet. I did read that in Texas, heat pumps are a primary way to heat homes. During the cold spell a few weeks ago, this drove the electricity demand way up; it was one major contributor to their huge power outage problems (the other being frozen everything). I think we aren't vulnerable in the Bay Area to that sort of cold spell, but heat pumps seem to be less efficient when there is a big temperature differential. I wonder what the solution would be for a place like Texas, that normally doesn't get that cold, but can - a backup system?
@Alan, that's a great question. Electric heating is very popular in the south, but it is more often electric resistance heating than electric heat pumps. (Electric resistance is much less efficient.) I think wider adoption of heat pumps would have helped Texas. Their performance is getting better every year in cold temperatures. They aren't as efficient as in warmer temperatures, but they still work, even in places like Canada. (A heat pump may come in two models, a regular model and a "cold" model.) Here is one article on that, from the Rocky Mountain Institute. Here is a map from a Nature article, based on Zillow data, about where heat pumps are used. I'm sure Zillow data is pretty imperfect, but it's interesting nonetheless.
Another point to make: because the ADU is usually not occupied at night, we try to take advantage of natural temperature swings to minimize the electrical power we use. We have an attic fan. In the summer, upon night fall, I'll use it once the temperature outside is a little on the cool side. In winter, in the late morning, if it's warmer outside than inside the unit, we'll open it up to heat it more quickly. Taking advantage of the natural temperature swings and good controllable ventilation and insulation can really keep the electricity usage minimal; a heat pump is only part of the whole strategy.
Sherry - that map is very interesting. I based my belief that heat pumps were common in Texas based on a comment in an IEEE discussion on the Texas power failures - but electric heat may have been more common. I have a friend in Indiana (a climate-change denier friend, no less), who installed a heat pump using the ground, rather than the air, as the heat sink, because he hated spending money on heating bills. It was a bit expensive up front, but it is a more efficient way to cool. His heat bills had been extremely high, and he says he is recovering his expense.
My wife and I were discussing this just this week. For the map, it reflects more the source of abundant energy as much as climate - Heat pumps make sense in the Pacific NW, and there is a lot of inexpensive hydropower there, too. When it gets cold, the heat pumps become inefficient, so it is better to use a simple resistance heater. Perhaps they just switch to a resistance heat mode? But it makes sense that newer homes in Texas would like the combined heating and cooling, to go with their wind power. :) Thanks for the good information. We have an old house, but with good insulation and double paned E-windows (and foam roof), it is usually very comfortable. We would add a system to get some cooling in the living room in the summer, and some heat to an adjacent bathroom in the winter. It is interesting to contemplate replacing the gas furnace, but it is only 24 years old.
Now Ms. Listgarten has got me thinking... These Mitsubishi portable room units cost around $650.00 per unit & I would need about 7-8 of them in order to eliminate the conventional furnace system in the house + we would now have an AC option. A coolant line (for the AC) needs to be run between the units so that probably involves seeking professional services to get behind the walls for interconnections. The conventional heater ducts still work OK but there are times during the off-season when they seem to be little more than some sort of subway system for rodents passing through. And even if I were to run with this Mitsubishi 'motel system', the old heater ducts would still be in place for the rodents to travel. The compactness of the Mitsubishi units is attractive and minimalist. Web Link
@Alan, yes, using shades and fans and windows makes a huge difference and costs nothing! Thanks for pointing that out. Also, yes, geothermal is an amazing energy source if you can handle the size/cost of the project. Re your climate-denier friend, it just shows that it's so much easier to electrify when the economics make the case. @RMRN: Yes, I think it makes a lot of sense to add one or two of these for cooling, then also use them for heat in the winter to get your emissions down. FWIW, I don't think it's true that electric resistance is better for heating than a heat pump when it's cold, at least wrt heating air. For these mini-splits, the efficiency gets worse in the cold, but not as bad as electric resistance. Check out the graph below from this article. You can see that even at cold temps, the COP (Coefficient of Performance), which is normally around 3 for mini-splits on a cool day, isn't going to get close to 1 (which is the value for electric resistance). Water heaters do come in hybrid (with backup electric resistance) because hot water is used differently and takes more energy to heat. @R: Yes, these are pretty mainstream technology, and a good fit for our area and for the homes we have. It's really nice to get efficient cooling and no-emission heat with one appliance. Not sure what to do about rodents in the ducts, though :)
Thanks for the efficiency plots. Looks like the typical measurement point is 45 degrees outdoors, 70 indoors. 85% of that efficiency at 20F outdoors is impressive to me. I must have old, old data in my head, and midwest cold standards. (Does it work the one day of the decade it's at -15 in the morning.)
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