I don't think a computer fan running on a cheap variable voltage wall-wart is very complex, and it's reliable, cheap and effective :) I also very much doubt that the heating due to friction is significant for ceiling fans. A more likely reason is that a low speed breeze is just as effective as a fast one for cooling, and obviously uses less energy. You can make a computer fan go slower by dropping the voltage, or putting two in series. Bigger fans move more air for a given voltage. Ok, having got the negatives out of the way, I like your ideas - you are thinking outside the box (does that make sense for a terrarium?). Let me share a few things with you. Firstly, there are two general kinds of fluid flow we can talk about: Laminar and turbulent. Laminar is 'more efficient', in that you can get more airmass moving (momentum) for a given input of energy. Turbulence chews up a considerable amount of energy, you can see this if you compare the water flowing out of a tap with a hose connector at the end, vs one without. The hose connector reduces the turbulence, increasing the rate at which the water can escape. However, if you want to get the air close to a surface you need turbulence. Without the turbulence the air forms a boundary layer (on a windy day you'll notice that the air is more still closer to the ground, even in the middle of a paddock). In your example of stomata breathing you wanted to get the air closer to the leaf's surface, this would require turbulence. (Having said that, I think the gas diffusion rate for CO2 in air is faster than you'll be able to blow air, so I don't think this is really a problem.) To get turbulence you are better off with a narrow stream of fast moving air hitting some kind of obstacle. This leads on to "matching". In electronics we have an idea called 'impedance matching', the same idea appears in fans and ducts, in water flows, in sound systems, pipe organs and car engines. The idea is that if you directly connect a thin tube with high 'whatsit' to a large tube with low 'whatsit' you'll get a reflection occuring at the boundary. This reflection causes signal loss, or energy loss (the same thing really :). In the little gramophone that we wound round and round we used an exponential horn to match the sharpish needle's high pressure, small volume sound to the room's low pressure, large volume. You have the same problem with your fan. Water falling is a relatively high pressure, low volume fluid flow. We want to match that to the low pressure, high volume fluid flow of air. There are many simple ways to do this. All of your nifty ideas have been mechanical (converting the falling water to mechanical motion, and then back using a primitive fan (propellor type fans are vastly more efficient than ones that work by flapping, or by impulse means, btw). Can we do the impedance match any other ways? When I go and visit

I agree with MichaelsAd that reverse osmosis is the most effective way to filter drinking water. Our problem, as I stated above, is that DH believes this wastes a lot of water. I also agree with dcarch that distillation removes impurities with boiling points above that of water (212F at sea level). That leaves most petroleum distillates which are a problem for our water supply. There are stories of contamination of our underground water by leaking fuel tanks. Distillation would do nothing for this kind of problem, where the contaminants have BPs well below that of water. These impurities can be very dangerous indeed. However, for anyone considering water filtration or softening, I strongly second the standard advice on the plumbing forum. Have your water analyzed before doing anything. Know what you are dealing with. You may find that the impurities in your water are harmless. They may not make your water taste good, but are not dangerous. Iron compounds are one example. The city of Bath in England has been famous since Roman times for its water which contains high levels of iron and other minerals. When I drank it (they charged 50p for a glass!) I didn't like it at all. And it made horrible tea. Water hardness is caused by calcium carbonates which are beneficial to many people. They also leave deposits in pipes, which is why some install water softeners. When we lived in Massachusetts we had no need for a softener, though lots around us had them and worried about the very low levels of calcium in the water. Sorry, I just don't get the hysteria. Cheryl This post was edited by jadeite on Tue, Jan 15, 13 at 9:30

Putting an indoor pool in without a commercial size dehumidifier would be a huge, costly mistake that you would surely regret one day. They are extremely expensive to install so it is understandable that you are looking for alternative solutions but the reality is that you need one. Also worth noting is the running costs of these units. They are INSANELY expensive to run. You have not received much info about the rusting / corrosion concerns you have mentioned. You need to make sure that every last metal component in the entire room is on a bonding grid. Everything. Then you need to install sacrificial anodes inline in the pool system as well as mounting anodes basically everywhere to limit galvanic corrosion. You should also consider adding an automation system to regulate your chlorine levels. You do not want an indoor pool that occasionally has way more chlorine than it needs as this will make corrosion issues much worse. Indoor pools are a huge pain, and a huge expense, but if you have money to burn then they are obviously great to own. If you cant afford every protection for your house, such as a dehumidifier from Dectron, then you should not install a pool indoors. Maybe install one outdoors with a pool enclosure around it.

Funny, most vegans I meet are secretive and don't like talking about it. Probably result of shocked reactions (guilty as charged) and related bullying. I can see why a financial analyst might try to use NPV for this but it adds assumptions other than regular investor meeting or beating market. Comparing a tankless gas heater to a large tank heat pump water heater with different fuels and performance details is not that simple. Who cares about negative NPV with tankless lag and cold water sandwiches or HPWH making an important area less comfortable. Is positive NPV more important than possibly poisoning your family with cheap gas tank combustion exhaust? Sure money is more valuable in the future including appliance cost and replacement labor. Hassle of emergency replacement is part of reason cheapo heaters exist. Better planning includes durability, especially when health is at risk. A 6 year life for a gas tank is more unsafe than 6 year life for electric tank. I'm guessing Bry's bean counting didn't include infrastructure or monthly utility fees either. I've heard some gas fees are as high as $30 a month/$360 per year even with no gas usage. Some have low infrastructure costs, but it's not uncommon for deeply buried gas supply lines, trenching and backfill to run in the thousands for our area, mainly for challenging lots. Our HVAC contractor charges a per appliance drop charge fee for gas supply pipe in the house, roughly half the cost of the cheapest water heater. Don't forget venting! It's not just about energy efficiency, paybacks and investment. This decision involves health and life-safety. Bry's water heaters and wonderdog's most economical suggestion are atmospherically vented gas heaters. These are dangerous appliances because they backdraft combustion exhaust regularly: Picture from above link 3 problems with atmospherically vented appliances. They are most dangerous inside a home. Garage installations are certainly more acceptable but they are still unsafe. Most attached garage-to-home interfaces are not airtight. Prevailing wind, stack effect, bath fans, dryers and most notably kitchen vent hoods suck garage air into the home. Having an open flame pilot light, inside the garage which is sometimes exposed to flammable fumes is not safe either. I have a friend that was tragically effected by this exact situation. If the garage is well ventilated to the outdoors, has no living space above, does not face prevailing winds has an airtight connection to house and is not exposed to flammable liquids or fumes that makes them more acceptable but all of that is such a stretch it's safer to say never. In case others like wonderjack have missed it, my next recommendation after a HPWH is a big, electric-resistance tank (or two smaller ones) which can be very affordable and high performance. Using electric tanks with switches, timers, Time-of-Use metering or Automated Demand Response are ways to use energy more appropriately while increasing the safety of a home. I realize good situations for gas exist but for the most part, it's not the cheapest way to heat anymore. It doesn't make sense for most new, code-built homes or those considering upgrading infrastructure for existing appliance replacement.