Posts Tagged ‘Appliances’

Silly "Green" Products, Part I

October 22, 2009

Here’s a silly “green” product, sold by a major “green” retailer whose catalog arrived in the mail yesterday:


This is basically a 25¢ plastic tray, sold for $16, which holds water. It alleges to “sustainably” “save your home” from “parched winter air.”

My critique: Firstly, my home does not need to be saved from being “parched”. What part of the house is damaged by dry air? Perhaps they mean save the home’s inhabitants from being parched– in that case, I refer the reader to last year’s posts discussing why it is not winter that causes air to feel dry– it is over-heating the house (here, here, and here.) Yes, if you insist on a hot house in winter, you will parch yourself. So you should turn down the thermostat, rather than buy gadgets to add artificial humidity to artificially hot air.

Secondly, the purveyor’s assertion that their “ingenious” plastic pan moisturizes the house “without… a single watt of power” is misleading. True, you don’t have to plug it in. But turning liquid water to vapor requires large quantities of heat, no matter how you do it. The fact that the unit does not have its own source of heat does not change the amount of heat it needs to do its job. In this case, that heat is supplied by the baseboard heater over which the device is located. Whatever fuel is being used to heat the house– electric, gas, oil– some of that will now be used to evaporate the water, at the expense of warming the room. Specifically, for every gallon of water poured into the device, you’ll need to burn close to an extra pint of fuel oil (or equivalent) just to make water into steam. And you don’t get that back as warmth– before long all that water vapor finds its way outdoors, and the heat poured into making it is lost.

In the final analysis, this device is no greener, or more sustainable, or even more useful, than gently simmering water in the tea kettle you already have on the cooking stove you already have. But again, I don’t recommend that, either.

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Toilets, Fridges, Heat

October 21, 2009

The other day Housemate came to me and said, “You aren’t doing that ‘if it’s yellow, let it mellow’ thing again, are you?” So I see it’s time for my annual diatribe against the heat-wasting effects of winter toilet-flushing (here’s last year’s).

I thought this year it might be instructive to compare the (unknown-to-most) evil of winter toilet-flushing to the (extremely well-known) evil of “letting all the cold air out of the refrigerator.” I am sure almost all of you can remember standing in front of an open fridge looking for a particular item, while a parent, a spouse, or maybe even the voice inside your own head says “Hey! Don’t let all the cold air out of the fridge! You’re wasting energy!”

So let’s look at this with hard data. Which wastes more heat– swapping out the fridge air for room-temp air, or flushing the toilet? Write your answer here before you read on: ________________

Okay. Here are the assumptions for this thought-experiment. To give all possible advantage to conventional wisdom, we will assume you have a super-efficient, ultra-low-flush toilet model that uses only 1.6 gallons per flush (our actual toilets use 3 gpf; really old ones use 5), and that you have a huge, cavernous fridge, such as this one. In fact, we’ll assume that you’re not only letting the cold air out of the fridge compartment (15.6 cu ft), but also out of the freezer (6.3). We’ll assume that the fridge is kept at 36ºF, and the freezer at 0ºF. Assume that the cold tap water to the house comes in at 50ºF. And, lastly, we’ll assume that you have not been reading this blog and so you still keep your house at 68ºF in the winter.

So now we need to find the heat difference between a fridge(+freezer) full of cold air, compared to room-temp air, then do the same for a flush worth of toilet water. Here it is:

1) The fridge: 15.6 cu ft of air x .081 lbs/cu ft = 1.26 lbs of air. Temperature differential between fridge & room = (68º – 36º) = 32º. Heat capacity of air is 0.24 BTU per pound per ºF. So the heat loss = (1.26 lbs x 32º x 0.24) = 9.7 BTU

2) The freezer: 6.3 cu ft of air x 0.87 lbs/cu ft = 0.55 lbs of air. Temperature differential = (68º – 0º) = 68º. So the heat loss = (0.55lbs x 68º x 0.24) = 9.0BTU

3) The toilet: 1.6 gal of water x 8 lbs/gal = 12.8 lbs of water. Temperature differential = (68º – 50º) = 18º. Heat capacity of water is 1.0 BTU per pound per ºF. So the heat loss = (12.8 lbs x 18º x 1.0) = 230.4 BTU

So, we find that the total heat loss for replacing all the fridge plus freezer air with warm air is 18.7 BTU, while the heat loss from one toilet flush is 230.4 BTU. In other words, you could “let all the cold air out of the fridge” a dozen times before you have committed a heat-crime as great as flushing the toilet once.

What can you do about this? I left suggestions in last year’s post. And don’t fret about the fridge. And you might consider joining the Brazilians, who are being encouraged to pee in the shower (in their case, to save water– but same idea.)

(P.S. For those really interested: if you pee a pint into the toilet and let it cool down to room temp without flushing, you get back 1.6 BTU of free heat!)

Musings

October 5, 2009

The two things that plagued my Cold House mind most, last winter, were the heat lost from hot showering/bathing/dishwashing/clothes-washing water, and the heat lost from the clothes dryer.

I (crudely) addressed the first issue by keeping the shower water in the freestanding iron tub till it got cold, and collecting the hot dishwasher/washing machine discharge in 10-gallon pails (keeping them until cold.) The new house doesn’t have such a convenient tub; it’s built-in, and against an outside wall, so getting water heat back through it will be less efficient. However, I have schemes in mind for rigging up a full graywater heat reclamation system (it involves a couple of 55 gallon steel drums, if I can find such.)

The dryer issue, however, remains problematic. Some propose that you can “reclaim” the heat from your dryer simply by venting the dryer into your house, instead of outdoors. There are even commercial gizmos such as this one for the purpose. Since the dryer exhaust is hot, it seems intuitive that diverting it to stay inside the house would allow you to reclaim the heat. Unfortunate it’s not really that simple– because the vast majority of the heat of the dryer exhaust is contained in gaseous water, not in the air. If you

redirect that into the house, the water vapor quickly condenses to liquid water, probably mostly on your windows and cellar floor. That gives off heat, indeed. But then it will again eventually re-evaporate, taking with it the same amount of heat you “reclaimed”. (If it doesn’t eventually re-evaporate, perhaps because your house is incredibly well-sealed, then you will wind up with a warmer but sopping wet house.)

Anyway, the only way to really get the heat back from dryer exhaust is to condense the water contained within it, and then dispose of that water before it evaporates again. Not easy to do. Last winter I experimented with counter-current condensers, in which a six-foot aluminum pipe carrying the dryer exhaust ran inside a larger-diameter aluminum pipe carrying the dryer intake air (the theory being that the water in the exhaust would condense, and drip out the far end.) But it was a miserable failure– only about a tablespoon of the 1+ gallons of water actually condensed. The moral: you need a huge amount of concentrated coldness to absorb the amount of rapid heat produced by the dryer evaporation.

The closest I came to success was by using another electrical appliance to suck up and spit back the heat of the first. By directing the dryer exhaust through a dehumidifier, I managed to condense about 80% of the evaporated water in real-time. This was pretty promising. The dehumidifier, of course, used some additional electricity of its own; but used in this fashion, it spits back much more heat than its own electric draw. The primary problems with this set-up were (1) no matter what I did with filters, lint started to clog the dehumidifier; and (2) there was too much technology, and too many moving parts.

All summer (while we’ve been using a clothes line, mostly) I’ve been wracking my brain for a better way to get condense the dryer vent moisture and get back that heat. But I haven’t come up with one that is cheap and both thermodynamically and functionally practical.

Tub Water

February 22, 2009


Surely one of the most criminal things you can do it take a hot bath in the winter, then pull the plug and run all the still-warm water down the sewer pipe.

I came home yesterday all wicked sore from skiing, and the big hot bath was pretty mandatory. You might think this is quite the waste of energy, all that hot water, but it isn’t at all if you use it to heat the house after you use it for bathing. And that’s easy to do: you just leave the plug in until the water cools to room temp.

Bubbling in the narcotic warmth of the tub, I got to doing mental calculations of the heat in the tub water, and how much it could warm up the bathroom (assuming the bathroom is a sealed system). That required some thought about the heat capacity of various components of the bathroom.

Here’s a pie chart that shows the findings, roughly. It is specific to my bathroom, which is about 7×9 ft with an 8ft ceiling, with tiled floor, and contains a heavy iron tub, small iron radiator, and ceramic toilet and sink. I’ve assumed that about 20 gallons of water has been run for a bath, and that the room is well-insulated beyond the sheetrock (which isn’t really the case, but, you know, just for illustration.)

So, once the temperature of the bathroom equilibrates, about 1/3 the heat will be contained in the tub water, 1/3 in the walls and tile floor, and 1/3 in the sink, toilet, radiator, and tub together. The actual air in the room is what “feels” warm or cold to a person walking around, but it actually contains only a tiny fraction of the room’s heat.

In practical terms, the fact that the tub water has about 1/3 the heat capacity of the rest of the room means that for every degree the water cools, the room will warm by 0.5 degrees. So if you start with tub water at 100F, and the room at 50F, you would eventually end up with both water and room at 50 + ((100-50)*.33) = 66.5F.

But in reality, you can extract more heat than that, because the bathroom is connected to the rest of the house, and given enough time and a coldish house, the bath water will cool further. If you keep the house close to the temperature of incoming cold tap water, you get back as house-heating almost all the energy you put into making the hot bath. Plus, you get a hot bath. Nice.

36 Hour Experiment

January 18, 2009

My housemate went away for the weekend… leaving me to my own devices. So I tried having the furnace and all space heaters off for 36 hours (Friday eve to Sunday morning), just to see what would happen. We were at the tail end of a cold snap on Friday (below zero F), but now it’s warmed up considerably outside, to 18F/-8C.

The only significant sources of heat created in the house during this time were:
a) Making one mug of coffee each morning
a) A hot shower Saturday afternoon (hot water turned on about 20 minutes)
b) Metabolic body heat of myself (roughly 100W) part-time and three well-insulated cats (estimated total 40W) full-time.
a) The electric blanket: Used at half-power (approximately 90W) about 8 hours each night– Friday night on the sofa in the bunker, Saturday night in bedroom.

And here’s the graph of temps outside, in the kitchen/bunker, and the bedroom.
As you can see, the house really doesn’t cool off very fast. Saturday morning the bedroom actually warmed slightly, of its own accord, which is mysterious– could be because it gets some morning sun? You can see that making coffee has a rapid effect on the air temp, though in terms of actual heat this is pretty trivial and is rapidly absorbed into the tile and steel heat-sinks of the kitchen.

The electric blanket kept me extremely warm (I had to turn it down several times last night), in spite of using only a lightbulb’s worth of electricity. Interestingly, the e-blanket set on 50% power has roughly the same warmth as another human being sharing the bed… perhaps not a coincidence.

CO

January 16, 2009

When my kitchen bunker is really on the chilly side, just making coffee and oatmeal on the stove can raise the temperature several degrees. And the other night, when I made a pizza (with a pizza stone) in the oven, the kitchen went up a delightful 10F. Considering these experiences, and the fact that burning natural gas (as my kitchen stove does) is ultimately a much more efficient source of heat than electricity, it’s tempting to maximize the use of the stove/oven in the kitchen and minimize the use of the space heater.

We all know that unvented gas cookstoves produce tiny amounts of carbon monoxide, which theoretically could cause toxicity. On the other hand, who gives a second thought to keeping the oven on for an few hours to roast a turkey, or keeping a stove burner on for hours while simmering a stew? This is never suggested to be dangerous. So how much oven/stove use is safe?

This is not easy to find out. Google searches on the topic produce only repeated warnings that “gas cookstoves should NEVER be used for heating”, because this will for sure kill you. But nowhere is it suggested that, say, baking six consecutive batches of bread could be even remotely dangerous– though if I did that in my kitchen, I’d be way overheated. I suppose the “do not use for heating” warning probable assumes that one would be trying to get the whole house up to tropical temps, and so running the stove full-bore 24/7. Obviously that’s a bad idea. But I can’t find much information on the location of the boundary between “perfectly safe” and “deadly” durations of stove use.

I suppose I could get a CO detector and find out empirically. But for the moment, I’m going assume that baking a pizza is no more dangerous than it ever was– even if it happens to warm up the kitchen nicely.

Another Wrinkle

January 13, 2009

I was pondering my recent electric bill again, still trying to think what electrical appliances I could possibly be using less when the house is cold. Then I realized that the most obvious one of all had escaped my attention: the furnace.

The furnace burns oil, but the oil burner and pump run on electricity. The contraption makes a considerable whooshing racket when it’s running, so it occurred to me that it might use a non-trivial amount of electricity. I went down cellar to read the labels.

And it’s true. The various electrical parts of the oil furnace together draw 7.5 amps, or 900 watts. The burner says it will burn 1.05 gallons of oil per hour, if running non-stop. Some quick math reveals that for every 100 kWh of heat the furnace extracts from oil, it also uses 2.7 kWh of electric. In other words, the oil furnace is roughly 2.5% electric. Of course, that electricity does get turned into heat, too, but most of it stays in the cellar where I don’t really want it anyway.

In dollars and cents, it’s also non-trivial. If we burn 100 gallons of oil in a month (which I quite easily did, midwinter, in the old days) that requires 86 kWh of electricity, which adds about $13 to the month’s electric bill. It’s about equivalent to 15 loads of laundry in the electric dryer. I think this clears up some of the mystery of why my bill last month was less than I expected.

Culture-Bound Delusions

January 6, 2009

Delusion, as defined in DSM-IV: “A false belief based on incorrect inference about external reality that is firmly sustained despite what almost everybody else believes and despite what constitutes incontrovertible and obvious proof or evidence to the contrary. The belief is not one ordinarily accepted by other members of the person’s culture or subculture.” (emphasis added).

Apropos of that, Green Grrl just posted the link to this excellent article in a comment below, but I thought it was worth moving up front. It shows how the belief that one can go through winter without central heat can be considered delusional, dangerous, and unstable in one culture, while being perfectly normal in another.

While Mr. Sakamoto’s town in Japan goes about its barely-heated winter as usual, here in New England pleas for fuel-oil assistance are approaching record levels. Some quick math from that article reveals that, as of December 22, almost 9% of all households in the state had already been approved for government aid for heating oil. And winter’s only half over. Even more fascinating, the article says that “the average benefit is expected to be about $940”– which I’m pretty certain is much more than I’ll spend, total, on heat this winter. Kind of shocking.

I have no issue with spending taxpayer money to keep people from truly getting hypothermic. That is money well spent. But perhaps the first question that should be asked, on the “emergency” fuel assistance application, is, “How much of your home have you decided to keep cold for the winter? If none, why?”

[P.S. I am definitely going to build a kotatsu for next winter.]

More On The Fridge? Really?

January 6, 2009

The fridge post incited sufficient controversy. We start to come up against matters of theory vs. practicality. Here are two:

1) “Why not put the fridge in the coldest place in the house, instead of the warmest?” This is a good question. I can see two competing arguments: (a) It makes no sense to store things you want cold, like beer, in a room you want warm, like the kitchen; but also, (b) It seems to make no sense to keep a net-heat-producing appliance, such as a fridge, in a room where the heat it gives off of no human use, such as an unheated spare bedroom. We can all agree that cold things should be kept in cold places, and warm things in warm places– but the fridge is both cold and warm at once. So where does it belong?

My instinct on theory is to stick with the fact that the fridge is a net-heat-producing object, not a stably-cold object, so long as it’s running at all. And thus it should stay in the kitchen. If you have a place where it doesn’t need to run at all, you don’t need a fridge at all– you just need some shelves. So the whole problem goes away.

But, practicality outweighs theory on this one anyway. First, it’s obviously not so practical to have the fridge far from the kitchen (though if that was the only argument, I’d overrule it.) More importantly, it seems the average fridge/freezer combination isn’t designed to function properly in much-colder-than-usual-room-temp. See here. I can attest, in fact, that this is true: in the weeks when I had my kitchen in the range of 48-50F (9-10C), I struggled to find settings for the fridge that would keep the freezer contents frozen, without freezing all the veggies in the fridge. So. I am settling on the idea that, if you’re going to own a fridge, it’s ideal to keep it in a place that is occupied by humans, and neither too warm nor too cold. Which seems to be my kitchen.

2) This debate about whether throwing fridge-temperature water back outdoors is a waste of heat, or not. Gets mind-numbing. Gets into the difference between heat and temperature, which aren’t the same. In fact, bringing a bucket of icy water (or even ice) in from outdoors will simultaneously cool the house and add energy to the house. Amazing, but true, and due to the different heat capacities of air and water (and other materials). A liter of water and a liter of air, for example, might be at the same temperature– but the amount of heat they contain is enormously different, by a factor of over 3,000. In other words, letting the liter of water cool 1ºF will release over 3,000 times as much heat (calories, kWH, BTUs) as letting the liter of air cool the same 1º.

So, in terms of contained heat, swapping a 2L bottle of fridge-temp water for 2L worth of outdoors-temp air is muchmore significant than swapping equivalent volumes of air at those temperatures. Even swapping 2L of cold water for 2L of hot air is a bad deal, heat-wise. In fact, by my [very rough] math, to break even on the swap you’d need to get 2L of air that was approaching the surface temperature of the sun (just very roughly). Good luck finding that (and if you can, I don’t advise putting it in a soda bottle.)

Here’s another way of thinking about it. Suppose I offer you an attractive five-ton piece of solid iron which you can put in your house for the winter, or until you tire of it. This hunk of metal comes to you at at temperature five degrees lower than your current indoor temperature. It will of course have to displace an equal volume of your room-temp air when we install it, but otherwise, there is no cost to you. So– do you want it? (For reference, iron has a heat capacity about 3/4 that of water, and 2,700 times that of air.)

J. and I discussed this last night. She refused my offer. I said I’d gladly take it if she didn’t want it. This, I think, because we were considering the situation from two different angles: heat (me), and temperature (J.)

J’s argument: the relatively-cool meteorite, with its enormous heat capacity, will draw heat out of the air and all the other objects in her house. Once they reach a new equilibrium, the overall house temperature will be lower than she started with, which makes her unhappy. If she wants to get back to her starting temp, she’ll have to supply more heat to re-warm the house (and the iron), which also makes her unhappy. So, she rejects the plan, on valid grounds.

My argument: the meteorite, as is, contains a vast quantity of heat– certainly more than the warm air it will displace, and quite possibly more than the entire rest of my existing house structure and contents combined. It’s like free money. So long as I don’t dispose of the iron when it is warmer than I accepted it, it won’t cost me anything. And if I wait till the whole system (house and iron) has cooled below the original iron temperature, then I will have sucked some free heat out of it. All I have to do is remember to roll the meteorite out of the house when it’s as cold as possible– perhaps when I return from a week of vacation and the heat has been set to minimum for a week.

P.S. On A/C

January 5, 2009

I was just perusing our federal government’s [rather limited] tax credits for homeowner energy-conservation measures. I was somewhat unhappy to see that we give credits for purchasing “energy-efficient” A/C systems. And even more unhappy to see that this credit ($300) is twice the credit for energy-efficient heat furnaces ($150). And did I get any tax credits for the three $30, 100W window fans that I use instead of A/C? Nooo.

Wouldn’t it make more sense to pay people $500 to have no A/C? Or give such people free fans? Or at least a letter of merit? One has to suspect the long arm of the A/C industry lobby when you see these sorts of things.