Yeah, you know, evaporative coolers get a lot of hate as not being true "air conditioners". Since they do not blow ice-cold air, people think they don't work. But, this misses the point. They are an energy-efficient way to reduce the ambient temperature, and they do this very well, with some caveats, as long as you understand how they actually work. Unlike an AC unit, you can't just turn it on and expect it to work.
First, the lower the relative humidity, the better they work. I lived in on-post housing for a while in Arizona, and that is how those houses were cooled. They did not chill the house, but they brought the temperature from completely unbearable to just bearable. So, when considering one of these for use on a boat, most of us live in areas where the RH stays fairly high, reducing the benefit (but not negating it). But ...
Unlike an AC system, a properly-functioning evaporative system brings air in from outside, cools it, and forces air out of the space at some other location (like a cracked window). This is because the cooled air is also more humid (due to the evaporation). It doesn't take long before the air is pretty saturated and then the unit cannot cool at all. Portable units (like the Lowes unit) fail in this regard because they just recirculate indoor air. In areas with very low humidity, this can actually be fine for a little bit - cooling the space down - but as humidity climbs, the unit stops cooling and the space eventually heats up ... on top of the humidity ... and actually makes it worse than before.
So, the issue is not a failure to eject warm air (as it would with an AC unit). The failure is in not bringing in outside air. This misunderstanding is why most people do not get satisfactory results. If it is hot outside, it seems counterintuitive that you would want to bring that air inside. But, an evaporative cooler cannot work for long, if you don't.
And, if a unit does bring in and cool outside air, then the other failure is typically the fault of the user - in not creating a good place for the indoor air to exhaust. That is the other thing about evaporative coolers. You want to vent indoor air at some point as far from the fan as possible. This creates a flow. Warmer, lower-humidity air is drawn in, increasing pressure inside. This air is cooled and its humidity raised. We want to draw that air through the space and eject it. Any space that does not have this air flowing through it will not be cooled.
Which brings us to one more point that most people don't fully appreciate. Intuition dictates that the longer you run your cooler, the cooler the space should be - like it is when you run an AC. But, that's not how these work. The cooling only lasts as long as the unit is running - pretty much the same as a fan. You shut if off, stop the air flow, and the cooling stops immediately. Running it longer does not cool it down more. The only thing that brings the temperature down is if you increase the air flow or the RH drops.
Fortunately, nature has provided portable evaporative cooling that is actually more efficient. When you move air over your skin, as we all know, the evaporation of sweat cools us. All a swamp cooler does is outsources this cooling so that we get the same amount of cooling, but with decreased airflow directly over our skin. In other words, we could get the same amount of cooling by sitting in front of a fan. But, a swamp cooler allows us to put that cooling process somewhere else (in the cooling unit) and just get the cooled air.
Of course, the problem with these inexpensive portable units is that, as mentioned above, they increase the RH so, although they initially cool the air, they also decrease the effectiveness of sweating. So, we sweat more and the humidity continues to climb.
All this to say that an evaporative cooler CAN work, even on a boat, but these portable units require some modification. All you would need to do is duct air into the unit (rather than taking ambient cabin air). Then, if you position yourself between the unit and a port or hatch that is cracked open (to allow exhaust), the unit WILL make you cooler than if you didn't have it, unless RH is quite high.
First, the lower the relative humidity, the better they work. I lived in on-post housing for a while in Arizona, and that is how those houses were cooled. They did not chill the house, but they brought the temperature from completely unbearable to just bearable. So, when considering one of these for use on a boat, most of us live in areas where the RH stays fairly high, reducing the benefit (but not negating it). But ...
Unlike an AC system, a properly-functioning evaporative system brings air in from outside, cools it, and forces air out of the space at some other location (like a cracked window). This is because the cooled air is also more humid (due to the evaporation). It doesn't take long before the air is pretty saturated and then the unit cannot cool at all. Portable units (like the Lowes unit) fail in this regard because they just recirculate indoor air. In areas with very low humidity, this can actually be fine for a little bit - cooling the space down - but as humidity climbs, the unit stops cooling and the space eventually heats up ... on top of the humidity ... and actually makes it worse than before.
So, the issue is not a failure to eject warm air (as it would with an AC unit). The failure is in not bringing in outside air. This misunderstanding is why most people do not get satisfactory results. If it is hot outside, it seems counterintuitive that you would want to bring that air inside. But, an evaporative cooler cannot work for long, if you don't.
And, if a unit does bring in and cool outside air, then the other failure is typically the fault of the user - in not creating a good place for the indoor air to exhaust. That is the other thing about evaporative coolers. You want to vent indoor air at some point as far from the fan as possible. This creates a flow. Warmer, lower-humidity air is drawn in, increasing pressure inside. This air is cooled and its humidity raised. We want to draw that air through the space and eject it. Any space that does not have this air flowing through it will not be cooled.
Which brings us to one more point that most people don't fully appreciate. Intuition dictates that the longer you run your cooler, the cooler the space should be - like it is when you run an AC. But, that's not how these work. The cooling only lasts as long as the unit is running - pretty much the same as a fan. You shut if off, stop the air flow, and the cooling stops immediately. Running it longer does not cool it down more. The only thing that brings the temperature down is if you increase the air flow or the RH drops.
Fortunately, nature has provided portable evaporative cooling that is actually more efficient. When you move air over your skin, as we all know, the evaporation of sweat cools us. All a swamp cooler does is outsources this cooling so that we get the same amount of cooling, but with decreased airflow directly over our skin. In other words, we could get the same amount of cooling by sitting in front of a fan. But, a swamp cooler allows us to put that cooling process somewhere else (in the cooling unit) and just get the cooled air.
Of course, the problem with these inexpensive portable units is that, as mentioned above, they increase the RH so, although they initially cool the air, they also decrease the effectiveness of sweating. So, we sweat more and the humidity continues to climb.
All this to say that an evaporative cooler CAN work, even on a boat, but these portable units require some modification. All you would need to do is duct air into the unit (rather than taking ambient cabin air). Then, if you position yourself between the unit and a port or hatch that is cracked open (to allow exhaust), the unit WILL make you cooler than if you didn't have it, unless RH is quite high.
