Human powered heater?

November 1, 2009 5:43 PM

Is there such a thing as a self powered/manual heater?

I figured this would be useful as my family normally stays in one room during the winter to save on energy costs - a small heat source is generally enough to keep it comfortable. Or possibly when the power goes out to generate some heat.

I keep thinking- this is a good idea, yet something tells me that it's completely stupid.

Google only brings up a bunch of patent listings.

posted by wongcorgi to home & garden (15 comments total)

An exercise bike would fit the bill, the quieter the better. Since all the input energy in to the device has to go *somewhere* and an exercise bike doesn't produce terribly much noise, sound, radio waves, etc, it's nearly a 100% efficient human-powered heater.

That being said, it's really not going to do much for you. A normally-fit human can only produce about 200 watts of (output) power for a long period time, less than half the power output of even a small space heater. The person doing this relatively strenuous exercise isn't going to want the room temperature very high anyway, so you'd be better off just having everyone do jumping jacks since the human body produces a lot of waste heat anyway.
posted by 0xFCAF at 5:53 PM on November 1

It's a lot less than 200 watts.
posted by fixedgear at 5:56 PM on November 1

Hmm, running in place? A bellows (if you have an actual fire there)? Good question, but I think this is one of those things humanity has been trying to solve for millenia.
posted by bebrave! at 5:59 PM on November 1

The good thing is that people produce heat. The bad thing is that people exercising don't produce all that much more heat. 100 watts is a reasonable assumption for the heat a person brings to a room, but keeping up exercise to produce 200 watts is hard hard work over time. So, instead of buying a bicycle and peddling it for three hours every night, you come out ahead if you spend that money on beverages and snacks and have one friend over for the same amount of time.
posted by meinvt at 6:20 PM on November 1

My buddy says that burning wood is good...
It heats you twice, once whan you chop it...
posted by Drasher at 6:26 PM on November 1

I call them blankets. We keep our house cool and I heat this tiny little space over my lap with a rectangle made of sheep hair.
posted by advicepig at 7:07 PM on November 1 [2 favorites]

Like humans, animals produce some heat. My cousin's stable is basically heated by the cows inside. But I doubt you'd want to live in a stable.
posted by Monday, stony Monday at 7:14 PM on November 1

My Uncle John had a metal box located in his workshop on the farm that was maybe 1'x1' square that he stuffed straw into.....I remember him telling me that as the straw decomposed it gave off heat.......I was young maybe 5 or 6 but I remember that box being pretty darn warm.
posted by HappyHippo at 7:33 PM on November 1 [1 favorite]

I call them laptops. We keep our house cool and I heat this tiny little space over my lap with a rectangle made of aluminum.

Also, HappyHippo, really? What an interesting idea. I remember farmers worrying about barn fires for the same reason, and being told that we can't bail wet hay for this reason.
posted by Area Control at 7:37 PM on November 1 [1 favorite]

Install excellent insulation and good air infiltration barriers.
Add an air-to-air heat exchanger, and a CO2 concentration sensitive
ventilation control system. Good, insulating blinds, and good
automation or bureaucracy with regard to their use.

Done right, you should be able to do fine on the waste heat from your
appliances and some passive solar heat, and the hundred watts apiece
that your hot flesh provides.

Location, number of occupants, square footage, subfloor construction
details (slab floor, crawlspace or basement), and number of hours
of occupancy per day per occupant, along with a list of appliances in the
same room would be required to provide more particulars.
posted by the Real Dan at 9:00 PM on November 1

I have a super-insulated passive solar house that uses very little heat, but it still needs some active heating. I use wood or a non-electric propane furnace that uses outside air for combustion. If you're just looking for a quick fix that will provide backup heat in power outages, you might look at a little propane or natural gas heater. Just make sure you get one that uses outside air for combustion, which will require cutting a hole in an outside wall for the vent, and make sure it doesn't require any electricity.

More creatively:

The decomposing straw reminds me of a hot box, used for starting plants early: Build a box. Shovel in fresh manure (must be fresh). Layer straw and other dry stuff on top. As the manure turns into compost, it will warm up. Any well-built compost pile will heat up. Mine used get nice and toasty when I added duck poop.

You could add some ventilation holes near the bottom and a ventilation pipe to the top so the, um, aroma would rise and go up the pipe. Non-electric composting toilets do this. In fact, you could just build a composting toilet in the middle of your living room and...

Some people with really big compost piles will run liquid-filled metal pipes through the pile to absorb the heat and deliver it somewhere else. That somewhere else could conceivably be a small radiator or whatever indoors that could, maybe, warm a pair of feet.

There are also plans on the net for window box heaters, which are insulated boxes with glass or plastic on top and a dark, quick-heating material (like black metal) near the bottom. You build them so they stick out of the bottom of a double-hung window. The sun heats the air and metal in the box and the warm air rises into your room. Its contribution would probably be minimal, and I would instead work on getting more sun directly into the room itself and providing mass to absorb it.
posted by PatoPata at 9:38 PM on November 1

Heating elements require a tremendous amount of energy because they work through electrical resistance. Reminds me of an interesting story ...

In 1946, there was a feeling among many French women that the best way to move on from the horrors of the war was to bring STYLE back. As the city woke up, hair salons reappeared. However, there was a problem -- no electricity. So what did they do?

If you went into a hair salon in Paris in 1946, you would see women sitting with their heads in the big hairdryers. These dryers were connected by wires to basement rooms, full of young men pedaling for hours at a time on stationary bicycles. That's France for you.

Anyway, you're probably best off just bundling up ...
posted by dacoit at 9:58 PM on November 1

The exchange rate for conversion of energy of motion to heat is really poor. One way you can get a sense of just how poor is to put you hand close to your brakes after you stop your car. The disc itself is very hot (DON'T touch it!), but when you think that you just converted the motion of a ton of steel moving 60mph into that piddling amount of heat you feel just a few inches away, you start to realize how hard it would be to heat yourself. If you need more convincing, many science museums have bicycle-powered light bulbs -- I think you'd have to be in pretty good shape to keep a 200W bulb lit for more than a few minutes. And whatever you save in electric bills would be made up for in increased food consumption.
We recently installed solar panels, and most days we generate more than we use. But if we do a couple of loads of laundry in the clothes dryer we're lucky to break even. Electrical appliances that generate heat are the things to pay attention to when you are trying to save energy.
On the other hand, with a bit of exercise you'll certainly feel warmer.
posted by Killick at 5:39 AM on November 2

I don't think the numbers are in your favor, but keep in mind, the numbers people are quoting here for the power output of a human being are typically being measured at the end of a bike chain. The rule of thumb I've seen is that 2x as much energy is being dissipated as heat.
posted by Good Brain at 9:14 AM on November 2

It's a dumb idea because, as a warm-blooded mammal, you are already your own space heater.
posted by chairface at 10:40 PM on November 2