Random thought of the day

Almost everyone knows that leaving the refrigerator door open in the summer doesn’t, on the whole, make your house cooler. But did you know that in the winter you could use your freezer to make ice, store it in the ice-house for summer use, and make more ice you would be using the refrigerator as a heat pump and warm the house? This would make more efficient use of the electricity for heating than if you used that same electricity to heat your home directly with an electric furnace or baseboard electric heat. Part of the heat comes from the electricity used to run the freezer and the rest of the heat comes from the water you put in the freezer. You remove heat from the water, causing it to freeze, put the heat into the air, which raises the temperature of the air.

Plus, when you use the ice you stored in the winter the next summer you save on your summer electric bill as well.

Yeah, I know. What a geek. That what you get when read the blog of someone who thought their thermodynamics class was fun.


51 thoughts on “Random thought of the day

  1. Heck yeah!

    Of course, the progressive answer would be to make a law requiring appliance manufacturers to make more efficient refrigerators.

    • That’s already the law here. In fact, for the last bunch of years, the city will pay you to get rid of your old refrigerator.

      • Except the process works no matter how efficient the refrigerator is at cooling the contents. Some heat is generated out the back of the refrigerator over and above the heat pulled out of the food you put in the refrigerator or freezer. That heat makes the kitchen warmer, and if you’re putting water in the freezer and taking ice out to the ice house you’re getting almost a double benefit — the kitchen is warmer, and there is ice for the summer.
        Of course that means you need a really insulated building to store the ice in.

  2. A thermal battery. Makes sense, and is economical as well assuming that you have enough well-insulated storage space at a reasonable price. I’m pretty sure that a large highly insulated room would cost less than a conventional battery of equivalent energy storage capacity. Be interesting to see an good economist run all the numbers (including things like wear on the freezer compressor, etc).
    Sort of a heat-pump that shifts thermal energy over time rather than walls.

  3. What about heat loss each time you open the door to take ice cubes out to the icehouse?

    • You do it once a day when you leave for work or get the mail and the additional loss is minimal. Or put you make the ice “house” a well insulated room in the basement and you just shovel them into the room through chute, with a well insulated door, from the main floor.

  4. Wouldn’t it be cheaper to not run your refrigerator at all if you have an icehouse? Why would you even need a refrigerator? Just store all your stuff in your icehouse and you’d save all the electric costs

    • No. Assuming you are using electricity for space heat already the you could even just throw the ice away and save money on the days you heat your home using the freezer output.

      The summer time use of ice for cooling/food-storage is just a bonus. Plus, where did the ice in your ice-house come from? If natural sources then you are partially correct. But the scheme still works in areas where it never, or seldom, freezes such as many parts of the southern U.S.

      • I don’t know anyone who uses electric for heat unless they are forced to. Almost anything else (natural gas, etc.) is cheaper than electric.

        • In the Pacific Northwest hydroelectric power is pretty cheap. Almost all the apartments are heated with electricity. And outside the city many homes are too.

          • Regardless; you’re paying something for heat, no matter the source. You’re talking about a price difference on energy sources, whereas the actual energy movement issues are the same, BTU for BTU.

            Traditional ice houses used sawdust, a waste product of the time, as insulation. There was always some loss of course, but ice could be stored all summer. The melt water still has a lot of potential for cooling, so if that were captured and cycled through the living space you’d still get some real benefit from it. Water has a very high specific heat, so even though you’d be missing out on some of the change of state capacity, there’s still a lot left afterward.

            As for wear and tear, you have some of that on any system. You’re trading W&T from one system to another, so we’re getting down to splitting hairs. A good compressor system lasts for years and years and years, or even decades, anyway and the replacement cost is trivial compared to your typical energy costs. My current fridge is at least twenty years old. If it only lasted ten years what’s that, 700 bucks in ten years, or 70 dollars per year? Big deal. I spend many times that each month for energy. Or pick up a used one for fifty dollars, or a used freezer like the one I got for fifty bucks, and dedicate it entirely to ice production.

  5. I had a question on a science test that was roughly “You can cool yourself on a hot day by standing in front of an open freezer”?
    Since it was T/F, not leaving room for “Yes, until the room and freezer reach equilibrium after which it is counterproductive”, I said “true” and had the question marked wrong for my trouble. Had a long discussion with the teacher afterwards, and he really honestly seemed to believe that one would be instantly hotter by standing in front of an open freezer. I asked him to demonstrate with the lab-fridge, but he said there was no point.

    • I remember my High School physics teacher talking once about how leaving the refrigerator door open is really heating the house. . .
      As for “no point”, this is exactly the situation experiments are intended for. There is a dispute about what the result of a certain action will be, and an experiment will provide data as to the actual result.
      I suppose your teacher taught science as revealed wisdom, which is what they do in Sunday School and in the Madrasses.

      • Well, if the refrigerator heats your house, I guess the same thing could be said about air conditioning since what is an air conditioner?

        I have a friend who teaches college level thermodynamics (has a PhD from Caltech) and he probably could explain this whole thing in layman’s terms. Science just isn’t my thing.

          • In order to make the ice to put IN the icehouse, which is for *storing* ice, not *making* ice.
            Put another way: how much ice can you pick up outside the door of your house, right now, in the middle of winter, if you walk outside to get some for the icehouse that magically just appeared next to your front steps?

        • The air conditioner moves the heat outdoors. The refrigerator/freezer does not. It has coils in the back that get warm as it cools the interior of the unit. Those coils put the heat removed from the inside of the unit into the room. It pumps heat from the inside of the unit to the outside of the unit. An air conditioner pumps heat from the inside of building to the outside of the building.

          My dad recently installed a heat pump that uses about a half-mile of outside, underground pipe. In the summer it heats the ground and cools the house. In the winter it cools the ground and heats the house.

          Using your home freezer and an ice-house is just a crude way of doing the same thing as the heat pump at my dad’s place.

          • Hell, here in Bellevue, you don’t even need to geothermal aspect for a heat pump, as it never gets cold or hot enough. Heat pumps work just fine with the ambient air.

            Now back when I lived in WI…

    • I always hated those type of questions. You had to guess as to how smart/knowledgeable the person writing the quiz was. When it was the instructor of the class you were taking you could pretty safely assume to only include information presented in the most recent lessons. But when it was a standardized test given to all the kids in the state/nation I was never sure. Should I use my knowledge of quantum physics or limit it to Newtonian physics? What about the phase angle between the current and voltage? Just assume D.C. or a phase angle of zero?

      And, of course, telling the test giver their test was broken and unanswerable with the given information never went over well.

      • Depends on the teacher. When I’m teaching, if I make a ambiguous or bad question, if you showed your work or could explain it well enough to demonstrate you clearly understood it, I’d be more than happy to give full credit for an answer that wasn’t what I originally though was the “right” one. Occasionally I even tossed the question completely, and I always encouraged educated, intelligent argument. But then, I’m not a typical teacher. Maybe that’s why I’m a sub.

        • You were never one of my teachers in school. I don’t remember having that problem in college. High school wasn’t too bad. Grade school was hell for me. Ask me about it sometime if we have the time for an hour-long rant.

          • Part of the reason I’m a terrible speller is Mrs Dawson. She didn’t like people asking how to spell words, she’s always say, with her pinched up face, “Go look it up!”
            Gee, that really helps me with ptomaine, doesn’t it, lady? Not that I’m bitter or anything. 🙂
            Intentional public humiliation for doing something stupid I’m fine with, but not for asking honest questions.

  6. someone who thought their thermodynamics class was fun

    Do you mean to tell me that there are people who didn’t find Thermodynamics fun?!

    Next you’ll tell me there are people who don’t like math!

    Sub-humans, I tell you! Absolutely not fit to participate in civil society.

    • For most people, there is not a lot of overlap in the Venn diagram of fun, thermo, and easy. I thought calc was fascinating, but never easy, for example.

      • Just because it ain’t easy doesn’t mean it isn’t fun!

        Hell, mix some chemistry in with your thermodynamics & who cares how hard it is, the fun at the end is soOoOoOo worth it!

  7. I recall reading an article about using phase change materials as insulation in the walls. Something like wax that absorbs heat during the day & melts, then releases the heat at night as it solidifies.

    Just gotta keep the stuff from leaking all over…

  8. Joe @ 11:10 What about the phase angle between the current and voltage?

    Sorry, I can’t resist the ice-making & electricity tie-in: ELI the ICE man. I feel better now. Those of you who don’t get it, ask an electronics geek. Or me, if you wanna get bored and/or confused.

    • They didn’t teach that when I went to EE school. We had to do it the hard way, derive it from Maxwell’s equations.


      I just think of V = L di/dt and know that with a sine wave current the voltage is a maximum when the current is crossing zero. And similarly I = 1/C dv/dt.

      • Joe @ 4:43 You big showoff 🙂 everyone knows Maxwell just made coffee. Yeah, we covered L di/dt but just for background as we were only gonna be lowly technicians. I remember getting so excited when I got ELI/ICE and why it’s called a sine wave and which way the lines of force run at what angle of rotation and and and (sits down to breath into a paper bag). I don’t understand why people look down on geeks who get excited about stuff.

    • OK bore and confuse us.

      I read in a physics book that an inductive load such as a motor was giving you, somehow, a certain amount of un-metered, and therefore free, energy, that the power companies knew this and just accepted it. Could you explain that one? I’m confused, but far from bored given the fact that the possibility of a new understanding is never boring.

      • Um, no, my understanding doesn’t go that far. I know there ain’t no such thing as a free lunch in the end. In an inductive load, voltage will lead current which means that for a brief time, you’ll have some voltage present at the load without current flow. Most of the power company’s load is inductive, hence the big boxy capacitors scattered about to introduce some capacitance into the system in an attempt to bring the power factor back to something more efficient. If anyone can expound on the “free energy” thing, I also would like to hear about it. Sorry, this is getting far afield from thermowhatsits.

        • The power station is of course looking at all those big transformer primaries, but the book was addressing the function of the meter that’s connected between the secondary on that last transformer on the pole outside and the loads in your home. Unfortunately I passed that book around so much that I lost track of it.

          • Hmm. The old style meter is itself a little motor, so maybe they were looking at the squintillionth-of-a-second lag twixt current flow and physical movement of the meter? I dunno. The new meters are digital (a pox on ’em as it’s one more feeble piece of electronics that’ll break) so the above may be irrelevent. The load presented by your house is still (I believe w/o any real evidence) rather inductive, so the power factor is still, er, a factor. If anyone still following this thread knows the scoop, let us know. Cheers.

      • An inductive load doesn’t really give you free energy. It increases the losses in the power companies distribution system (the generator, wires, and transformers) without increasing the measured power that you consumed.

        It’s a little hard to explain but I’ll try using a mechanical analogy. Imagine you have a heavy weight on frictionless wheels on a level surface. Push on it (voltage) and it starts moving (current). At the very start of the push there exists a force without any movement. As it moves you gradually ease off on the pushing and then start to push it in the opposite direction until it stops and reverses direction. You then push in the original direction long enough for it to stop in the original position.

        From the power companies viewpoint they were supplying energy when it was being pushed in one direction and it was getting energy back (infinitesimally increasing the speed of their generators) when it was being pushed in the other. It got exactly as much energy back as it sent. Therefore the electric bill is zero. But both the original delivery of energy and the return of energy incurred losses in their system. These losses are on their side of the meter and hence you are not billed for them.

        Now imagine instead of a level surface you have a U-shaped curved surface (the analog of a capacitor). The weight starts at one tip of the U and rolls down one side and up the other. As it starts up the other it slows down, stops, and reverses direction. As it rolls back and forth no outside forces are required beyond that to overcome the losses such as the real life friction in the wheels and the windage losses from it moving air aside as it rolls back and forth.

        In the first case the power company exerts a force in the first direction and resists a force in the other. In one direction it delivers energy and in the other it receives it. The net result on your side of the meter are only the losses on your side of the meter. But the power company absorbs the cost of the losses on their side of the meter. These losses are some large multiple of the power measured by your meter.

        In the second case the power company only delivers energy to get the load started and to make up for the losses. All of this energy is consumed on your side of the meter. The power company still has losses on their side of the meter but they are some fraction of the energy measured by your meter.

        Does that help?

        • Thanks for the explanation, Joe. So, it’s “free energy” in the sense that the utility distributes it and we don’t pay for it; we also don’t get to use it as it just due to losses. No such thing as a free lunch, darnit. Let’s talk about “zero-point” energy next! Who needs Tesla when we have the fantasy-du-jour available?

          • With the added emphasis that the losses the power company is concerned about occur on the power company side of the meter. Any loss on your side of the meter you do pay for.

          • Good point about load-side losses.

            Actually, let’s not talk about “zero-point” energy as I’ve managed to display my ignorance quite well enough already, thankew. 🙂 Invigorating discussions like this one beat the heck out of a vapid tv show.

  9. The limiting factor, and it is a big one, in this theoretical ice battery system is the power output of the typical home fridge. It’s pretty tiny compared to the 240V high Amperage electric furnace (or the power used by any heating system. We’re talking on the order of a few hundred Watts compared to several thousand (IIRC my electric furnace’s consumption is around 7KW). There’s at least an order of magnitude difference, I’d say, even if you take duty cycle into account. Point being you’d need an industrial capacity freezer to make a big difference.

    Your dad’s heat pump will be on that order of capacity, though it won’t be taking advantage of the change of state for the most part.

    Additional ice could be made in the colder weather by simply exposing water to the outdoors. A gigantic ice machine if you will, similar to the one in your home. On a large enough scale this could in theory provide much “free” cooling in summer.

    Any heat flow can be used to do other things as well, so the possibilities are many. A mountain of ice on a hot day could be used to make electricity for example.

    There’s a huge amount of “free” energy all around us, all the time, but it is usually so widely dispersed that it would require huge engineering projects to collect it in useful amounts, meaning it isn’t really free. We could say that oil is “free” too– Just find it, drill down to it, pump it out of the ground, refine it, ship it, store it, dispense it, and there you are. “Free” energy.

    Same goes for tidal power. I mean holy cow, how much energy is being expended to make all the oceans of the planet rise and fall many feet twice per day, to say nothing of the land masses that also rise and fall a certain amount? It’s right there for the taking, right? Just try harnessing it in global economically useful amounts though. Oh, then there’s OTEC. TeraWatts there, but again it requires gigantic, large scale engineering.

    Still there are simple, very practical things that can be done outside the grid, especially if you have a clean slate so you can design from the ground up. And waiting around for governments to try to force these things on people is a loser’s game. If it can’t be metered and sold by a huge company, and controlled, governments will be against it. There’s nothing in it for them, and if it leaves them out of the picture they’ll hate it with a burning passion.

    • OK, so when does someone bring up Tesla? Actually, please don’t bother. I’m sick of hearing about it. Show me first, then talk about the magic secrets of free energy for everyone, known only to Tesla, captured and hidden by the FBI after his death. But you can’t. So shut up. Go build a fucking a tesla coil and make sparks, and keep it to yourself.

    • The freezer “power output” in BTU’s is greater than the power input from the electrical system. This is because it is taking energy from the tap temperature water. I don’t have real numbers nor the time to look them up right now but it is plausible that a 1 KW (electrical input) heat pump could deliver 7 KW of heat at 100 F using a constant source of 50 F water. 6 KW comes from the energy of the water and 1 KW from the electrical input.

  10. Since we have freezers and refrigerators for cooling our food and heat-pump water heaters, why hasn’t somebody combined the 2 or 3 of them?

    Get your hot coffee/tea/chocolate water from a tap in the door of the fridge. Plumb a hot water line to the faucet or dishwasher.

    Though this is coming from a guy who won’t buy new energy-efficient appliances because he can’t make the numbers add up to justify dropping the $’s on them.

    • Cuz you want your tea-water boiling hot and the warm coil on the back of your fridge is merely warm. Not enough of a differential to make a difference.

      • It could be used to pre-heat water, except for the fact that, again, your regular old fridge doesn’t dissipate enough energy to make a big difference in any of these scenarios. Anyway; whether it’s heating water or the living space won’t much matter to your power bill, all by itself. No sense in borrowing from Peter to pay Paul.

        Although it should be noted that in climates like North Idaho or NE Washington where we heat some eight months of the year, any “more efficient appliance” that sits in the living space isn’t saving you one bit during the heating season, i.e. most of the year. The difference in heat loss (more efficient means less heat output) must be made up entirely by the furnace. Same goes for those super efficient LED lights– it only means your furnace is working that little bit more to heat the space. Only in the non-heating months can you save any remotely significant amount of energy on any appliance that sits in the living space by making it more efficient. You make a light or a TV or a fridge more efficient by x, and the furnace will work harder by essentially that same x. The exception would be on total hot water USAGE where the hot water is being dumped outside the living space after you paid to heat it, as in washing. The efficiency of an electric water heater that sits in the living space is utterly irrelevant during the heating months (up to three fourths of the year in much of the U.S.) because, again and again! it’s waste is in the form of heat that goes into the living space that you’re heating anyway.

        The politicians who have a habit of nudging us this way and that have absolutely no clue what we’re even talking about, I might add. The dumbest person in the room is the one most interested in calling the shots.

  11. I guess all this discussion explains why air conditioning capacity in the US is measured in “tons” – I guess meaning “cooling equivalent to x tons of ice melting in 24 hours”. 🙂

  12. I thought the winter was when you tried very hard not to make everything into ice, where you live.

    But if taking perfectly good melted ice and refreezing it is an efficient way to keep the house from turning into one giant popsicle box, I say go for it.

  13. They actually ARE currently making heat pump domestic hot-water heaters. In areas where home heating is a relatively small part of the energy consumption, and you’re air-conditioning for most of the year (as opposed to where I live in Minnesnowta), it can actually make sense.

    Many homes in warm-climate areas don’t even have a combustion-type heating system, depending either on air-to-air heat pumps or resistance heating (electric baseboards, for example) for heating the house. The vast majority of time their either ventilating or actively cooling (air-conditioning) their living spaces. Their only option for domestic hot-water heating is electric. A heat-pump hot water heater is essentially cooling the air in the house in order to heat the water. For folks in warm climates this makes sense. After all, most human activities generate heat (as noted, so does your in-the-house fridge and freezer), including all electrical appliances (feel the back of your TV, or computer). The hot-water heat pump is essentially a self-contained basement air conditioner that’s sticking the heat into the hot-water storage tank instead of dumping into the ambient air via the outdoor condensing unit.

    As noted, a heat-pump hot water heater is more efficient at heating the water than a resistance-type heater. In warm climate areas without natural gas running to the house, and without a propane supply, those are about the only two choices available.

    This would make zero sense in my house in my climate (I’ve got a natural-gas-fired hot-water heater) since my basement is currently, after three weeks of sub-zero temperatures, right around 45F to 50F (depending on where you measure it). I sure as heck wouldn’t want a heat pump sucking what little warmth there is in that space out of it and putting it into my hot water. No, I depend on the “waste” heat in the radiator pipes and surfaces of the furnace and hot water heater to keep the basement warm. It’s also a great place for incandescent bulbs, since they not only provide light, but most of their energy use goes into warming the air in the basement (something the eco-fanatics have disregarded in their diktat to eliminate light bulbs). If I were required by the eco-fanatics to put in a hot-water heat pump, I’d have to heat that air back up via my furnace just to keep the air in the basement above freezing…this would be the essence of “not making sense”.

    Air-to-air heat pumps are terribly inefficient once the ambient temperature drops too far. Below about 0F, they’re no more efficient than resistance heating (which is terribly expensive in electricity use). In northern climates, having separate heating (combustion-type) and cooling (A/C) systems makes more sense. These are most often combined into what LOOKS like a single system, with a forced-air combustion-fired furnace that has an air-conditioning coil (the “A” coil) stuck on top of the plenum.

    Because my house is old (1901-built) with radiators, I don’t even have ducting. To use A/C, I’ve added a “mini-split” system with an outside condensing unit and multiple indoor fan/coil units, individually controlled. Those units can also be run in heating mode (as an air-to-air heat pump), but for my climate it’s far more economical to just fire up the furnace, since heating with natural gas is far cheaper than running the A/C as a heat pump. It is nice to have it as a back-up heat source, should the furnace ever fail but it would be next to useless at this time of year with an outside temperature of -17F.

  14. Let’s get silly, then… Put the icehouse in your basement. Have the automatic ice maker drop the ice into a chute that drops directly into the ice house. It fills during the winter, while you heat your house…

    Then, you run a recirculating duct system in your house forced air connected to a fan, connected to a thermostat switch, that recirculates air through the ice house and into your house during the summer. Run a floor drain in the ice house to the outside for melt water. Basically, you run the air through the ice house, into your living area, and then recirculate it over and over again, keeping your house cool.

    100% automated. You wouldn’t even have to look at it, unless something went wrong. It would use a metric shit ton of water, though, so it may not be cost-effective depending on how much you get charged for water by your municipality. Ranging from essentially free if you’re on a well to insanely expensive to you poor bastards in Arizona.

    • Why would you want to throw away the melt water? It’s clean, yes? Make the ice house/basement two layer, with the melt dropping through a porous floor to the tank/pool below it. Then just recycle it. Return it to the house as cold water, or to fill the ice maker, or use it for outside yard use, or even a swimming pool. Some attention would have to be paid to ensuring cleanliness of the system, but proper initial design should help a lot. Having a large store of potable water, that is not accessible to outside influence, could be a life saver in bad times.

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