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Swamp coolers for the house?


It has been hot here recently in Catalunya. Like 40°C and forest-fires-covering-our-patio-in-ash hot.

Luckily, the house is traditionally constructed with extremely thick, solid stone walls which means the worst of the heat doesn't make it inside – so long as we remember to shut the windows. Even so, a little extra help to keep the temperature down during the day would be very welcome.

Why not air conditioning?

Perfectly installed AC unit

Despite it being really effective, I don't love air conditioning for a few reasons:

  • the units are invariably ugly (internal and external)
  • installation is relatively complex (heat exchangers, possibly ducting, dripping water, ...)
  • not particularly energy efficient

Instead, we started looking at evaporative cooling, also known as swamp coolers.

What are swamp coolers?

Swamp coolers work on the principle of evaporation absorbing a good amount of heat from the surrounding air – it's why misting your skin on a hot day feels refreshing and cool. They harness this phenomenon by directing (ideally hot and dry) air over a wet surface, resulting in cooler and more humid air.

Solar powered swamp cooler in Black Rock City

The coolers work best in an arid climate, which we don't have here but does explain why they're popular at Burning Man. in the middle of our summer days, however, humidity is around 25% which should be fine according to this helpful page.

Buy or build?

The vibe we're going for in the house is rustic, trying to keep many of the original bits and pieces. This allows us to bodge all the DIY and claim it's characterful.

Dalek sandwich toaster

However, unfortunately, most – if not all – of the commercially available coolers look like props from Doctor Who.

Given ancient Persians were using these things to cool whole houses in the middle of the desert thousands of years ago, surely they're quite easy to make?

Most of the examples online definitely fall in the ugly but functional camp.

Then, I found Thibault Faverie's Cold Pot which looks amazing. It uses terracotta as a porous material for the water to evaporate from, and a small fan to move air through it. However, I must admit that to my inexperienced eye it looks like it wouldn't be very effective. No evaporation occurs within the air stream itself – it relies on the chill of the ceramic being passed through multiple components before it gets into the air. I'm pretty sure we can do better.

Where from here?

I suspect it will be a fairly long process to find something which works well, looks nice, and is easy to put together, so I wanted to get these initial thoughts down now rather than them becoming just another draft post.

My planned next steps are – in some order:

  • figure out what to use as a porous material
    • Plan A is a terracotta plant pot
  • figure out how to blow air through it
    • Plan A is an old computer fan from the rubbish dump
  • figure out how to maximise air-on-terracotta contact
    • Plan A is an Archimedes screw, spiralling up inside of the terracotta
  • figure out how to keep the terracotta saturated
    • Plan A is a reservoir, open at the botton and sealed onto the pot

We'll see how many of those Plan A's work out!