Towards a better tinyhouse

Inventing to freedom?

Archive for September 2010

A house is *Not* an investment.

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A house is not an (monetary) investment, though it may or may not be better than renting, depending on the area. I just pulled those links from a quick search. I’m sure there are many more. I’m not going to introduce any pet economics theory here, just point out that the honest experts all agree. Though I do find it very odd that they fail to include much about the mortgage interest rate.

Yes, the appreciation or depreciation will affect the total cost of ownership, so that is one of many factors that need to be included in the cost.

But. When you own a home, especially with a mortgage, you spend money to do so, money that you will not ever see again. The more expensive house, the more you spend. A lot more.

The magic of modern finance does not change this.

However, from what I have read, it is true that mobile homes, which are considered “chattel” live in a less favorable financial climate. However, some counties in the US have started taxing them as real estate, which is good. And they did by themselves, without being asked, by all accounts.

Turns out there is apparently a sort of self-reinforcing cycle of depreciation and poor finance as a result of being considered chattel, that can be broken. When you change the way the government treats it taxwise, the banks change their treatment loanwise, and the market changes their treatment depreciation wise, and it’s much like a regular house now, financially.

So I think it would be a really good idea to get potrable tinyhouses considered real estate as soon as possible, then they could end up being even cheaper over the long run.

Also, anyone who thinks using or living in a bighouse is somehow going to make them money, or not cost much more, is a being very silly person.


Written by gregor

September 23, 2010 at 14:48

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Cheaper solar power collector array

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Solar panels are just too expensive. This(edit: I put the wrong link in somehow, corrected now) site says the cheapest are $1.55 a watt. In Ottawa here, for a very modest 3.6 kwhr per day ( a normal house uses 24-36), a 1kw array gives you about 2.4 kwhr in winter (search “solar atlas”, also “solar NREL data” gives some actual data, I have to look into it, but hourly data would be really nice), or $2325. And that’s the very cheapest panels, who knows if you could actually get them.

A while back I looked into whether or not using a mirror or tracking system would reduce costs, and by how much, and how to do it inexpensively.

The increased output varies by quite a bit, but it’s usually about 40% more for a sun tracker, and obviously for mirrors it depends on the configuration of mirrors. What I meant, though, is something fairly cheap and easy to build, and which can make use of normal solar panels, since I’m assuming high temperature solar collectors would end up pretty expensive and hard to obtain. Is it economical?

Well, for mounting a tracking system and mirrors on top of an ordinary roof, a whole lot of factors come into play, mostly damage during storms, installation costs, and that most people wouldn’t consider them “attractive”. Unfortunately cosmetic appearance is critical in a tinyhouse, even more than elsewhere, with the uphill battle against bad zoning (still meaning to write a post about that).

But if you could accommodate that somehow, or if it’s a relatively remote area, especially if you can just put them on the ground, or you plan ahead when designing the house, so it is easier to attach the system… The numbers are pretty clear. A combination of tracker and mirrors should be easily less than half the cost, even less in highish latitude like here.

For a tracking system, one of the problems with commercial systems is that they use these fancy actuators, and they use another one for each 600W or so of panels. What if you connect them all together with cables (like fishing line you can get some pretty strong stuff that is very hard to stretch, like dyneema line, which is about as stretchy as steel!) so they move in unison with a single actuator?

Plus, once you have a tracking system, you can use mirrors effectively. Again, wish I could draw this in 3D. Drawing it in 2d in paint probably wouldn’t help much.

Anyway, consider the figure one on this page. Now consider just the left half of the figure. You have the mirror and the PV panel – why not put another mirror, doing the same sort of reflecting, on the other side of the panel? And 2 more above and below the panel? Ignoring reflector efficiency, that gives you 4 times more sunlight on your panel. I don’t know why they don’t do this.

In january, in Ottawa here, we get about 350 watts peak per square meter of sunlight, (perpendicular to the sun, i.e. the optimal configuration to intercept sun). You multiply that by 4, and it isn’t going to damage the panel or anything. The standard test conditions are 1kW/sq meter. The ambient temperature is obviously very low, so it can dissipate heat fine. If the temperature gets too high in summer, if you don’t want to remove some/one of the mirrors, the sun tracking system can detect that and tilt the whole thing so that the panel is shaded a bit more.

Yes, it increases the temperature of the panel a bit, so the efficiency goes down, but you’re still going to get way more power out of the panels. I wonder about the possibility of using infrared reflective film material over the panels to reduce heating. Or maybe IR transmissive mirrors. Or just a fan directed at the back of the solar panel.

But what about a really cheap way to do the sun tracking system? Oh boy, sun tracking systems are really expensive, there’s no way that could ever be economical, some people will say. I don’t believe a word of it.

Suppose you take a mounting system a bit like the one shown in that page’s Fig. 2. It has to be adjusted, ideally, manually with the seasons, but who cares. A little exercise twice a year isn’t gonna kill you. Use some door hinges (well greased) and some wood. Then you need the actuator and the tracking electronics. To keep the cost down, use only one actuator, with the cable tethering thing. The tinyhouse’s programmable logic controller (search this blog for a post on that) can do the sun tracking. Not only does it have a clock in it, but it can measure the the output from the panel to make sure it is optimal. The tracking does not have to be very accurate. The actuator? Well, seriously, all you really need is a gear motor and a spindle. Get some rope, and have it wind up the rope using the spindle (like a winch), ideally with it winding out the rope at the same time, if you see what I mean. If you wrap the rope in the opposite direction on the same spindle, you can get it to both release rope, and to take up the other end of the up rope at the same time. This allows you to exert some tension on the rope without exerting a net force on the gearmotor (the force being exerted to pull the rope off the spindle is canceled out by the force to pull the other end of the rope off the spindle, resulting in no net torque) . You need some tension to prevent any wobbling, maybe you could avoid the need for a spring tensioner by using relatively stretchy rope.

You can get winches pretty cheaply, at $60, it might as well make a handy actuator. The PLC can control it directly.

I have not seen, with a fair bit of searching, any reason anywhere why this would not work. You could surely get 2 or 3 times as much energy harvested each day, when you combine the 40% increase from tracking, and multiply with the hypothetical 400% from reflectors.

A tracking system also reduces the need for batteries, because sunlight is available sooner in the morning, and later in the evening. Especially for a relatively large collector array, like for a tinyhouse village, it could save some serious money over an unassisted array.

Edited to add on 2010/11/11: I remember seeing a document with an insolation vs. power out put graph for a solar panel. Looked again, couldn’t find a graph like that, which would easily show the fallacy of assuming that reflectors couldn’t work.

Also found a fairly good article about the greenhouse gas emissions associated with solar panel production, which obviously using reflectors helps with:

Written by gregor

September 22, 2010 at 00:59

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MBR for domestic greywater

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I found this system almost serendipitously. I just searched “tinyhouse greywater recycle” to see if my own website was being indexed yet, an this caught my eye in the search results. Great… I had previously searched for “membrane bioreactor domestic” etc several times, an this never showed up. And this isn’t the first time this sort of thing has happened. I have officially lost all faith in Google’s supposedly leet ability to find what you are looking for.

Anyway, it’s interesting. They use flat plate modules, and it filters about 600 l per day, apparently. We only need 70 per person, so you can imagine if you divided the system size by 9 it would be a fairly manageable size. Just need to get a hold of one of the membrane modules they use. Maybe you could buy one from them as a spare part….
You would want some polishing with activated carbon and ion exchange resin to use it for showering, of course, and a redundant disinfection stage.

Written by gregor

September 21, 2010 at 14:40

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Laundry for tinyhouses or off grid

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Okay, so to start with, some cool technologies you may or may not have heard of :

centrifugal dryer

Cold water detergent (mind you, reviews of how well it actually works seem to be mixed, but I quite enjoyed the ingredients section of that site)

Ultrasonic washing machine I’m wondering if the latter could be used for clothes, even though it is for vegetables.

hand operatedplunger washer

ventless dryers includes centrifugal
Some thoughts:

The wash and rinse cycles are, I think, basically processes which get the clothing into equilibrium with the surrounding water (or water- detergent mixture aka “wash liquor”). Certainly the rinse cycle, anyway. I’m not as sure about the wash cycle, because the way it goes, is the greasy substances on the clothes come off into the water as “micelles”, colloidal sized globs of greasy stuff surrounded by detergent. Does all the greasy stuff get converted into this form? Well, not all of it, some must stay on the clothes, but I wonder how much…. If it all got converted, then in 1 wash cycle, the amount of greasy stuff that goes along with on the clothes would be proportional to the amount of water in the clothes divided by the amount of wash liquor in the chamber. So the wash cycle is a divide-by operation – divide contaminants on the clothes by (total wash liquor volume)/(liquor volume absorbed by clothes).

This matters, because 2 half size divide by operations can get the clothes cleaner than 1 full size operation, if the divide by is more than 2 (which it is). (x/2)^2=x^2/4 instead of just x. This could be used to get the clothes just as clean, with a lot less water and detergent. Same applies to the rinse cycle if you wanted to do a better rinse with less water.

Another thought is that the micelles can be removed from the water, while leaving the rest of the detergent in. Ultrafiltration can remove them. Not all the detergent gets used up in forming micelles, because there is a certain amount of detergent that must be present in the water before micelles even start to form. Only the detergent that is added In addition to that amount can be used to form micelles. If this worked, you could save the micelle-free water for the next round of washing, or use just a very small amount of wash liquor in the wash chamber, and as the wash cycle proceeds, continuously run the wash liquor through the, this could be used to greatly reduce the amount of detergent and water used. However, dissolved stuff would still accumulate…

Okay, but with regards to the machine, I was just thinking, if you have centrifugal drying machine, you don’t really need a machine with a spin cycle, do you? You might have to take the clothes out and put them through the centrifugal dryer in between the wash and rinse cycles, though (because this reduces the amount of wash liquor in the clothes, thusly increasing the value of the divide by operation mentioned above). There must be a lot of “broken” front loading machines around that can wash, but not do the high speed spin, that would be cheap or free.

You might be able to actually rinse the clothes in the drying machine, though, and save a bunch of water at the same time. Suppose the dryer is spinning. The clothes are pressed up against the side of the machine. You spray water on the inside layer of this wall of clothes, and it gets centrifuged through the clothing, displacing the dirty water. Voila. No dirty water in the clothes. Keep spinning until they are dry. You can get motor controllers that could be used to slow down the speed of the dryer while you do this, if the full speed is too high to safely open the lid. I just bought 2 of them for greenhouses, you just plug the motor into them, and they have a dial to adjust. They work much the same as a light dimmer, you can buy fan speed controllers at the hardware store too, which require you to wire them in. One problem with this is that it wouldn’t rinse out any particles or lint, but might be worth trying….

You can use the rinse water from the last load as the wash water for the next load, that’s fairly common.

I remember seeing a bigger version of that ultrasonic washer somewhere, called the “xcube”. Could be more suited to clothes.

I remember reading a nasa paper while doing research for the water recycler, that said the reason the ISS doesn’t have a laundry machine is because the detergent would be too taxing on the (physico chemical based, a biological recycler would have no problem with it) water recycler. Mire had a washing machine. However, the authors said that ozone actually works pretty good in place of detergent. Could be worth further investigation.

Lastly, apparently that “laundry alternative” machine doesn’t work for beans, so forget that…

Written by gregor

September 21, 2010 at 14:14

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inexpensive off grid air conditioning for a tinyhouse

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Okay, so I was wondering how to do this, and I put together a spreadsheet. I’m no spreadsheet ninja, and this is the first time I have used Calc, but you can put your own data in, and see for yourself how these things could apply to your own situation. I got my data from here . It would be interesting to look at a hotter climate, and see what sort of approach would work there, and I tried to find some data for California, but no dice. The data I use here is for July, the hottest month here. See the last graph for the actual temp. data plotted.


Scroll way to the right, there are the graphs and stuff, and the assumptions like the U value of the walls and stuff, that you can adjust. I’m assuming a third of the walls are getting pretty hot from the sun, 45 degrees, but it turns out it doesn’t have that much effect anyway.

There are a couple of ways of cooling without electricity, and you have no doubt heard of thermal mass storage, which I have been calling thermal closeting, though turns out that is not a very common term for it. Whoops. Also, evaporative cooling . The spreadsheet includes a basic simulation of both these approaches. Definitely basic. But it tells you more or less what you can expect. But first we need to know the cooling requirements:

The reason the graphs are so spiky, rather than having a smoother increase in the amount of cooling required as the ambient temperature goes up, is that it turns out, surprisingly, that by far the biggest load is the heat produced inside the house by electronics, cooking, all that stuff, plus solar gain from the windows. By far. I assumed it is 200W at night and 400w during the day for electronics, and a sort of arbitrary 100w for solar. If the temperature is below 23 degrees out, hypothetically, you can just dissipate the heat by dumping it outdoors. When the temperature is higher than that (or whatever you consider to be the maximum), all of a sudden, you need to produce that lower temperature, to remove the heat. The contribution to the cooling requirements that dehumidification and the need for ventilation imposes do change more smoothly.

The interior of the house isn’t enough thermal mass to take full advantage of thermal mass storage, as you can see below. This graph is with a 1 ton of water, I would think more than the interior of a tinyhouse, and it still leaves some days unconditioned (the heat capacity of wood is about half of water’s). Even if you are willing to settle for 25 degrees, it doesn’t get you though day 5 or 6, because the temperature the previous night was too high. Plus, if you are using the interior of the house, that ignores the fact that you are cooling the thermal mass to an uncomfortably low temperature sometimes, and need to blow a lot of air through the house to recharge the mass. Also, I did not include anything to take into account the possibility of it helping with the latent heat needs, because it would have no effect anyway in this climate. It would have to go below about 14 degrees during the previous night. Maybe in the desert, though.

Strictly speaking, there should be some factoring in of the thermal resistance between the thermal reservoir and the house, but I ignored that for now. In effect, that would slow the rate at which the reservoir absorbs heat, a couple degrees before it was full. You could use phase change material, and that could make it a bit more practical than a ton of water, but to make a good decision about what types and how much you’d have to look at more data, I think, but 20 kg of phase change material would really help with those times when the night temperature is really close to the max. permissible indoor temperature.

Oh, by the way, I got some bad news about the heat exchangers. Turns out the manufacturer’s lie through their teeth about the efficiencies Looks like 60% for sensible heat, and 40% for water vapor is more reasonable. It does go up, though, if the airflow is lower, and in this calculation the airflow is 8 CFM (223 LPM), rather than the 120 or so that the exchangers are usually tested at, so you can change the heat exchanger efficiency in the sheet if you want.

One thing is, though, that it might turn out that they are pretty expensive, though. In that case you would go for the smallest one around, I guess.

Another, kind of unfortunate effect of the fact that it is the heat produced inside that is the main problem, is that you can’t easily distribute the cooling power through the ventilation system as is done in a forced air system. The 8 CFM of air would have to be pretty cold to transfer the necessary amount of energy, especially during the daytime. Which would pretty much require electrical cooling.

Instead you would have to either put cooling coils in the wall or something, or, I think probably more practical, is to use a fan blowing over an air-water heat exchanger. I remember seeing a tinyhouse with a ceiling fan once. That could work fine, just put the exchanger above it. Or, I noticed there are fairly cheap “evaporative air conditioners” out there, which by all accounts don’t work for jack, but they have the air-water heat exchanger and a fan in them. Maybe that or some other consumer product could be used.

They might work as an evaporative cooler, too, but you have to put the evaporator outside…. The problem with their design is that the evaporator is indoors, so it increases the humidity in exchange for reducing the sensible heat (eg decreasing the temperature of the air), which is exactly the opposite of what you want.

It’s pretty amazing how much cooling power you can get from water, though, the system below uses about 10-15 liters per hot day. I plotted it in 100s of ml so it would show up on the graph. You can see it’s far from perfect, though, it’s no good on the days humidity is high. This device is made to cool the water, not the air, then you pipe the water around wherever and use it to absorb heat. Unlike a swamp cooler, it does not add water to the indoor air.

The system in the spreadsheet, uses a regenerator to improve it’s efficiency. To see what would happen without it, set the efficiency to zero. Basically something like the Ultra cheap ERV I just posted, but you don’t have to worry about the smell of the regenerator media, so you could use polyester quilt filler material, or sewn together sweatshirts or something. But it can’t ever cool below the outdoor dew point – or rather an outdoor dew point.

An idea occurred to me, that if you did a whole bunch of evaporative cooling during the night, when the dew point is lower, using it to cool down a thermal reservoir to the ambient dew point during the night, then it could be cold enough to be used to do some dehumidification during the day (when the dew point rises). Unfortunately it looks like that wouldn’t do much good in this climate. What you really want to do is to remove water from the indoor air, as it comes out of the heat exchanger (heading to the interior of the house). The dew point during the previous night has to go below the dew point of the indoor air the next day before it even starts working. Well, I guess you could dehumidify the air going into the exchanger from the outside, and that could help just a bit on some days. Hm, sounds like worth looking into, if it helps enough to open up other options elsewhere….

Another, more useful idea (for me) is to use an electrical heat pump like a compressor cooler to handle the dehumidification. If you are off grid, chances are you will have a solar panel somewhere, which means you’ll have extra power available in the summer. Might as well put it to use. The compressor in a cooler might not be powerful enough, though, but it could be worth checking. You’d need to have a way to get it to do just the dehumidifying, without the need to release the cold air (since it has to cool the air down first before it starts to extract water). You could use a… I know, I know, not another one, but, a counterflow heat exchanger. The air goes through it, into the cold chamber where water condenses out, then back through the exchanger again, and out. This one would be a cheap one, because you only need it to exchange sensible heat. You can make such an exhanger with Al tape and Al foil and some cardboard, just fold it like an accordion, and one fluid flow goes on one side, and the other on the other side.

Heck, if you had a big enough solar collector, after thermal mass storage, you might be able to use an electrical air conditioner, I remember seeing a 5000 BTU one somewhere, and you can get really small 12v ones for truck cabs, as a low cost replacement for a broken main AC system. 4000 BTU/hr is about 1000 watts, IIRC, so that’s just about right, and it should take 300 watts or so to run.

Another way would be to use a solar powered desiccant system . Liquid, or the desiccant wheel thing if you can swing it, they don’t seem to say so on that web site but with heat input, the desiccant wheel can be used to actually pump water vapor, too. You heat the air that is on it’s way out of the system directly before it passes through the wheel. Apparently they have an efficiency of 10% or something, but you don’t need much power here anyway. With the wheel system you can use a lower temperature, so you can use a flat panel collector, whereas I think the liquid ones need vacuum tube collectors. Might be hard to get a hold of a suitable one, or the carbon stuff, though. It doesn’t have to be a wheel, you can use 2 or 4 stationary beds of adsorbent material, and use an air switch to switch the direction of airflow between them. I wonder if you could make you own adsorbent by dousing some activated carbon with calcium chloride.

For the liquid system, take some tangled fish netting, or something similar, and by dripping water on it, that can form an evaporator (or absorber), just as a way to present a large surface area of water to the air. Then the water goes off to be heated by the sun, driving the water out, and back to absorb some more.

The last cool possibility that I was thinking of is a personal cooling device of some sort. As long as you can keep your body temperature down, you stay comfortable. I don’t know if you’ve ever walked out of an over conditioned theater into a really hot day, but it’s actually pretty pleasant at first. Until your body temperature rises because you can’t dissipate enough heat (or, if it is above 37 degrees, because heat is even being conducted into you, too).

“Personal cooling system” finds plenty of examples. I wasn’t impressed with any of the ones I saw, though. Not very efficient, so you have to lug around a big cooling reservoir. Also, I wonder if having the cold tubing against your skin would be very comfortable.

It seems like the best way from a comfort standpoint would be to only have air in contact with the skin. Basically, to shrink the air conditioned room down to the size of a vest. It would have comfortable elastic cuffs around the arms and waist, and a turtleneck around the neck to seal it. There is no need for any ventilation, though, because you are not breathing the air. You can just have a fan or something blow air around, through a tube on the back of the garmet to the right side, then into the vest, across your torso, gets sucked in the other side, to the cooling coils or whatever, then back for another run. Or maybe use tubing made of a water vapor permeable material (the tubing does not contact your skin), and flow cold water or a desiccant material through them. Water vapor then diffuses into the tubes, and the heat, and flows away, keeping everything comfy. It can then be cooled with evaporation if a desiccant, or ice for water – the advantage of using a desiccant is that it does not have to be at a low temperature to absorb water, so it can be cooled purely by evaporation. Evaporation gets you about 10 times as much cooling power for the same weight, and you don’t need a fridge to keep producing ice. Mind you, if you are indoors, that would raise the humidity…

Lastly, personally, I noticed something this summer, which struck me as pretty handy and useful – I, for reasons I won’t go into, had a bunch of wet clothes laid out on my bed. It was really uncomfortably hot and humid. The air conditioning is intermittent here, and it was not turned on, though I don’t remember the exact temperatures, checking the weather records wouldn’t have meant much, because I’m pretty sure it was hotter inside than outside (I didn’t want to open the windows because the noise is really bad here). I was resigned to spend a night sweating. So, anyway, I went to go to bed, and they were still wet, and, being pretty tired, I was faced with a dilemma: Put clothes away or no? At first I assumed I better put them away, because I fuzzily recalled sleeping on wet clothes is uncomfortable (yes, this had happened before). But then I realized that was only because it was so cold. So I tried it, and it was actually really comfortable all night. I slept better than usual, even. It’s amazing how they seem to stay wet and cold all night long (previously very annoying). I think this could be really useful in Ottawa here, where there are usually only a relatively few nights a year where it is really too hot, or for tinyhouses with no AC at all.

They weren’t fully wet, they had been in the dryer, but the “automatic dry” feature screwed up, and they were not dried fully. They were definitely heavier, just to give you an idea of the water content. Wetter clothes would work fine, I guess, just from after the spin cycle. You would think mildew would grow, but it didn’t. Having just been washed inhibited it enough, I think, and maybe because there was still some detergent on them.

Essentially this is a bit like a wet bulb thermometer. You are the thermometer, and of course the clothes are the wet cloth.

Written by gregor

September 20, 2010 at 02:50

Posted in Uncategorized

Ultra cheap energy recovery ventilator $20?

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The mini homestead. Unfortunately this place would be very difficult to heat and cool, a quick back of the envelope indicates about 3.5 kg ($7, $210 a month) of propane a day (at 0 deg out and 25 deg in) and more than 35 kg of ice (at 22 in and 28 out for 8 hours a day) each day (osb has a u value of about 1, figure 70 m^2 wall area, use the heat of combustion for propane and latent heat of fusion for water). Much more if it is badly sealed. You might be happy in this instance with some insulation and no ventilation, but I got me thinking: How could you make a really cheap energy recovery (heat exchanging) ventilator? That could allow you to build a cheap passive house.

Okay, it could use regenerators, which are used in units like this , but you don’t need the desiccant. And you don’t need it to move. The desiccant can improve efficiency (without it the air going out during cold weather would usually be at 100% relative humidity, whereas the air coming in is at a lower humidity, so you loose some water)

Instead, you just use a regular fixed matrix regenerator. Actually 2, because you need to have air flowing into the building at the same time that air is flowing out.
Then you need to reverse the air flow periodically.
Then you need some sort of motive force to push the air through the regenerators, wind would do nicely and cheaply here. To estimate how much wind you would need, you can think about the regenerators having an “equivalent free area”(EFA), if it has an EFA of x many square centimeters, then the same amount of air will flow through it as if you had a hole in the wall with that area, x. You can make the beds shallow and wide,o so that would not impede the airflow much. Theoretically it doesn’t affect the thermal characteristics, it is only the thermal mass of regenerator material that matters. And even then, that just determines how often you have to reverse the flow through the regen (it gets “full” of heat faster).

This method recovers not just the sensible heat, but a lot of the latent heat too. Water condenses on the heat exchanger material on the way out, then evaporates again when air is drawn back. I’m pretty sure the only practical way to get the latent heat back is to re-evaporate the water into the incoming air stream. You don’t get all the water back, because the air exiting the regen on the way out of the building will be at it’s dew point (so 100% RH), but no lower. As it’s going out, it cools down to the dew point, water starts to condense out (and accumulate on the regen media), and during this process the rh can’t go below 100%.

The regen media can be aby fibrous stuff that doesn’t emit smell into the air, fiberglass (maybe taked from and insulated duct so you know it is odor free) cotton, polyester clothing, polypropylene wool, etc. so it’s pretty cheap.

Then you need to harness the wind. You can see by one of the diagrams that this is being done just by orienting the intake and outtakes of the system so wind gets blown through.

Then the hard part is periodically reversing the airflow through the regens, let’s call them the left one and the right one.

I think a simple wind powered mechanism would do fine. The one shown in the diagram works like this: You have an “air switch”. This is basically 4 air valves (the seals don’t have to be very good or anything) connected together so they all switch at once. In the schematic vies shown in the figure, it goes like this: valve a and d are turned on, allowing air to pass, air flows into the building through the left regen and out through the right. Then, c and b open, and for a brief period air just sort of short circuits,going straight from the incoming air line to the outgoing air line – this serves no purpose, of course, it’s just a result of the way the air switch works while it is transitioning. Then, a and d close. Now, air is going out through the left regen and in through the right. Perfect.

Now you need a way to actuate the switch, so I suggest this:
you have a 6 bladed turbine (for lack of a better term), which is located between the air switch and the regens, one side of it is exposed to the air stream going to the left regen, and the other side to the air stream going to the right regen, these streams area going in the opposite direction, so the turbine turns.

As it turns, it winds up some fishing line or string. When it has wound it all up, the string becomes taught, and pulls, causing the valve to switch. The turbine has to have some momentum, so you might need to add some weights, because during the switching process there is no air flow to power it (because air short circuits briefly). Then, after the airflow has been reversed, the turbine starts turning in the opposite direction. Repeat.

Because the turbine rotation keeps reversing, you don’t need any bearings, either, you can just suspend it with some string. It gets twisted and untwisted a bit…

In between the air switch and the turbine you can imagine you need to do some air ducting to connect the output of the switch to the input of the turbine section, just connect the outputs of a and b together, and c and d.

So as you can see, it’s all pretty cheap… and would give you pretty good efficiency, too, there are some companies selling rotary (but no desiccant, I think) heat exchangers that claim 95% efficiency.

Hey, I bet this could have applications in the developing world, for homeless shelters, and other really cheap shelters. Combine it with some uncovered foam insulation on the inside of the wall of the mini homestead, and some great stuff for sealing all the cracks, and the whole place might not need any propane at all most of the time. It would pay for itself in only a few months.

Written by gregor

September 12, 2010 at 12:20

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Tiny House Hour real time chat with audio/video conference

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I was just thinking of a sort of online tinyhouse conference and how you might host it.

It could be text only like e.g. IRC, audio or video. Just one way could be to try to mimic the coctail party scenario, where there are groups of people, with however many people in them that can communicate at once without it getting too hectic, and you can hear or see what is going on in other groups, talk to each other at a different volume, etc. Turns out there is nothing like that out there that I could find.

I looked around, and there are a great number of video conferencing options, usually limited to 6-16 people per room. Then there are various pieces of chat software, less sophisticated than the conferencing stuff, but maybe still usable.

Before I started searching, I decided on the following features that seemed like a good idea:
-Multiple rooms (a lobby area), ideally with the ability to see some of what is happening in each room.
-Voice capable for people why are slow typists.
-Shows you what has been said when you come in the room, allowing you to join the discussion faster.
-Web based, no installation and multi-platform.
-Can cost money, but should have a free trial to verify it works, I’d pay for the first month, then there could be a paypal donate whip-round if people want it to continue.

I think, rather than setting up the system and just leaving it up and on all the time, it might be a better idea to have a designated time, like 6:30 pm wednesdays, or whenever the largest fraction of the english speaking population starts to watch TV, or whatever. Otherwise, with no agreed upon time and place, people may come at all random hours of the day, see there is no one else around, and leave. No discussion happens. People stop checking and the concept dies. With a designated time, people are much more likely to show up at the same time.

Below is my take on the software options I found, I started out not taking notes, just assuming I would keep looking until I found what met my requirements, but then I realized it didn’t seem to be anywhere, so I started keeping track, to decide on the best one. Just go straight to the demo if you want to see what it is, the websites are usually not very good about telling you., this is one of the first ones that I came across that looked good, but the number of people supported is too small, plus they want a lot of money for it. Seems to have a lobby feature, but doesn’t seem to allow the users to create new rooms, rather the moderator has to. I don’t like that. Would be a lot of work for the moderator to do a good job on that, and more than likely it just takes power away from the participants. Unclear whether it supports video or audio. It is the only one I saw that shows you what has been said in the room when you first come in. Untested., Audio but no video. Multi room support. Many users supported, if the conference grew, something like this could be needed. seems to work okay but only supports a single room and doesn’t show newcomers what has been said, still, we could simply post in the comments of a blog post Tinyhouseroom1, tinyhouseroom2, etc. as the rooms fill, though that isn’t perfect because you still have to join a room to see what is happening. Funnilly enough, this might be the best, I think. Doesn’t seem to work, no error message or anything, just doesn’t work, tried it on 2 different computers Does not support multiple rooms, but might be worth looking into deeper. I tried the free demo, and it’s pretty buggy. looks like only offers one meeting room 6 people max. same deal, one room 6 people. Tried the live demo, doesn’t seem to work, also only 1 meeting room.

Yahoo chat groups, at an appointed time.

Audio only using skype “group call” feature, if someone wants to call in from a land line, though, that costs 12 cents a minute or so, per person calling in, which the host of the group call has to pay.

It’s frustrating to realize that the sort of features you thought were basic requirements are not available. It didn’t occur to me that *group* meeting software might only support 6 people at a time without the hassle of getting and paying for another software license or something.

The tinychat-based approach looks like the best, though, I think. Now to decide on the ideal time. Any ideas?

Written by gregor

September 11, 2010 at 12:31

Posted in Uncategorized