Comment by jcrawfordor | Hacker News Reader

Comment by jcrawfordor | Hacker News Reader

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Swamp coolers always work by displacing the indoor air with outdoor air, if they recirculated indoor air they would drive the humidity up until they were ineffective (one pass through my cooler already puts the indoor RH at 50-60%, vs. about 10% outdoors). The difference is that, in addition to replacing indoor air with outdoor air, a swamp cooler can also use evaporation to cool the outdoor air so that this is effective even when it's warmer outdoors than indoors. This does mean that you have to have windows open for a swamp cooler to function... visit a house in Albuquerque and the combination of swamp coolers and crime mean that you'll see window iron or wooden props everywhere so that air can go out without burglars coming in! The blowers in swamp coolers are powerful too, often producing a constant indoor breeze. Mine slams doors if I'm not mindful.

A normal practice for cooling is to run the blower when outdoor temps are lower than indoor, and then both the blower and pump when outdoor temps are higher. Thermostats are available but not very common on swamp coolers, one reason is that independent control of the pump and blower makes them a bit more complicated than an "on/off" behavior, and another is that they take time to displace the indoor air so they work best if you anticipate the daily trends by cooling the house farther than target before temps really climb in the late morning. During weather like we have in Albuquerque right now, lows in the '70s and highs in the '90s, you will run the blower 24/7 but might stop the pump when the house gets cool enough.

I've thought about it a bit and I can't really see how what's described in the article is different from the normal "best practice" for swamp coolers - bringing in outside air, with or without additional evaporative cooling depending on the outside temperature. He refers to the advantages of closing up the house to retain the cool air, but if that's sufficient (and it is for a while in spring and fall) you just turn off the swamp cooler and close the windows during the day, no extra hardware is needed.

Author here: I don't know very much about how swamp coolers are used in practice, so I could easily be missing something. I do know that they're basically never used up here in the Northeast (Boston) because they work by increasing humidity and in the summer we tend to have pretty high humidity already. We also tend to have daytime highs high enough that the air leaving a swamp cooler would be warmer than the temperature of a structure that's been cooled overnight with a whole-house fan, plus more humid, which means during the hotter parts of the day you don't want to bring in outside air. So, how could a swamp cooler be used without increasing the daytime humidity of the house?

What I'm imagining is running a swamp cooler overnight to cool the structure of the house as close to the wet bulb temperature as possible, then in the early morning run it a bit in fan-only mode to bring in drier outside air (accepting that this will warm the house up a bit), and then shut the house up and turn the cooler off for the day.

What we currently do is run a whole-house fan overnight, and shut the house up during the day, with no swamp cooler. I'm trying to figure out whether adding some evaporation to the system could make sense.

There are two approaches worth considering.

Evaporative cooling is not worth doing in Boston for the space in a residence. It can be used, however, to improve the efficiency of refrigerated air units. Take a look at air conditioner misters that spray hose water onto the radiators for refrigerated air units. Although I suspect a good percentage of that heat is carried away simply by conduction rather than evaporation, it could conceivably cut your air conditioner bills. Water-cooled whole-house air conditioners are high maintenance, otherwise they'd be commonplace.

The other approaches involve tag-teaming a refrigerated air unit with a swamp cooler. The air intake for a refrigerated air system would work a lot better at 80 degrees, 80% humidity than 90 degrees, 60% humidity. I am told this is commonplace in Phoenix.

One other often-overlooked characteristic of the "swamp cooler zone" is that it tends to be at high altitudes, which aside from keeping things dry and cool enough to have a shot at good-enough cooling, requires doubling the size of refrigerated air units to keep pace with design specs. The air is thinner enough up here that the radiator can't keep up as well. This shifts the balance slightly in the direction of swamp. This has been what feels like an unusually hot and humid summer in Albuquerque, and our household finally sprung for a room air conditioner, run in parallel with the swamp.

You should look into building elements with micro encapsulated phase change materials. They're becoming popular nowadays, and you can find ceiling panels and wall panels from commericals suppliers. The pcm melts during the day cooling down the room, you recharge it at night by using a whole house fan to continuously pass cool air throughout the house.

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