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I want cool a small room with something that uses less than 2kwh per night with more cooling effect than a simple fan. The room is on second ground with 2 windows and one door and is about 15m2. I have access to ice. The room is in the Caribbean. Thank you in advance for your help

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  • where are doors and windows situated? is this room above ground, on ground level, or below ground? do you have access to ice? – depperm Sep 9 '19 at 12:30
  • Prior to AC they used to have a fan blow across a block of ice. Swamp coolers are considered ac by some but use falling water and evaporating water for a cooling affect no Freon. Just pumps and fans. – Ed Beal Sep 9 '19 at 13:13
  • Are you asking how to cool it below the outdoor temperature? – isherwood Sep 9 '19 at 13:55
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    "with more cooling effect than a simple fan". It's a common fallacy that a fan will cool a room. Fans do two things: 1) they move the air causing people's sweat to evaporate faster and make them feel cooler, and 2) they add heat to the room. If your fan is labelled "100W", then it is equivalent to a 100W heater. I've known people that leave fans running in their rooms while they are out so that "it will be cooler when I get back". In fact, their room ends up a degree or two warmer than it would have been. – Ray Butterworth Sep 9 '19 at 14:13
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    Put a second wall surface with an air gap and create a "Trombe" wall... – Solar Mike Sep 9 '19 at 19:01
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This answer takes the question literally and offers a way to cool the room without assuming you are cooling a person or even that there is a person in the room.

Buy a small air conditioner. With 30 seconds of searching I found one that uses 400 watts. Maybe you can find one that is even smaller or even more efficient. Insulate your room as well as you reasonably can, at least close the doors and windows and seal any large cracks. For such a small room this will easily come under 2kWh. It will help if "night" is limited to hours of complete darkness. If the room is leaky then you limit "night" to, say, 6 hours or whatever it takes to remain under your arbitrary energy ceiling.

And since you are in the Caribbean you could measure with British kWh, as they are 11.5% larger than American ones. :).

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  1. Open a window on the ground floor.
  2. Open both windows in the bedroom on the 2nd floor.
  3. Have a fan blow hot air out one 2nd floor window. This will have the effect of getting rid of hot air (which rises to the 2nd floor), and bringing up cool air from the ground floor.

Alternate 1: Check out these Youtube videos about using ice and a fan to blow cool air around you. There are many designs here.

  1. Larger chunks of ice will last longer, like a 12" cube.
  2. But you will likely run out of 1" ice cubes in 2-4 hours so somehow you may want to refill those.

Alternate 2: Put a cool, damp washcloth on your head, chest, or inside of elbows (there are a lot of veins close to the surface there), have a fan blow on you. This helps cool you down via evaporation, but again, the water will need to be refreshed about every 2 hours. I've done this before when my AC broke.

Alternate 3: Have a rubber bag of ice, put on your head, inside of elbows, or on your chest. Have a cooler next to the bed for 1-2 spare rubber bags filled with ice.

Alternate 4: Have a mister bottle with plain water next to your bed. Spray your self slightly with water and have a fan blow on you to cool you through evaporation. Remist yourself as needed. Do not mist yourself so much that the water drips.

Source: I live in Michigan, it gets hot and humid in the summers. I've tried most of these.

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This answer assumes you want to cool a person in the room, not just the room itself.

My grandmother told me that when she was small they would hang a wet blanket from the ceiling and one of the servants would poke it with a stick to get it moving. Is that an option for you? If your servants are all too busy perhaps you and your partner could take turns poking the blanket. Of course, my grandmother did not have electricity when she was small so this may have been the best option.

Today I think the best way for a person to stay cool while sleeping, better than any A/C regardless of temperature, is a combination of two airflow solutions:

  1. open a downstairs window and put a quiet window fan in your bedroom blowing OUT. Do not open any other windows. This creates a flow of cooler downstairs air into the upstairs and warmer upstairs air to the outside. If there is more than one room involved you have to open multiple downstairs windows, and put an exhaust fan in each room to be cooled. There must be no upstairs windows open other than the ones with exhaust fans, because then you just move warm air around the upstairs. You have to keep the bedroom door open, at least a little, along with any other doors that would limit the desired air flow.
  2. A ceiling fan above the bed, blowing downwards at a low speed just enough to maintain air flow over you and not so fast that you feel you are being fanned.

These things use far less energy than any A/C, they are quieter, more pleasant, and the cooling effect on a sleeping person is just as good as a 20 degree drop in room temperature, which is all a small window A/C could achieve anyway.

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I didn't use a simple fan but I bought a Vornado 660, it's a room circulator that can push air 100 feet. I've dropped the temp by a few degrees but it's not cheap.

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  • The air temp may have dropped, but it certainly wasn't due to blowing the air around the room with a big fan – SiHa Nov 3 '20 at 20:57

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