Hacker News Reader

Comment by hourislate | Hacker News Reader

Simply putting your outside AC Condenser Unit on the shady side of a house or have a Tree or Bush shade it can significantly reduce your energy usage. They units themselves are at least 20 Degrees cooler than being in direct sunlight.

There are also misting units that use approx 1-2 gallons of water a day (equivalent to a toilet flush) that can also reduce energy consumption by up to 30%.

Simple solutions for big savings.

View on HN

Your first claim was so interesting I had to Google it. But this article suggests it doesn't hold up.

https://www.energyvanguard.com/blog/will-shading-your-air-co...

Moneyquote: "The temperature of the surrounding air has a much bigger effect on cooling efficiency than direct solar gain, and the volume of air pulled in by an air conditioner is huge."

This article you are referring to is for a heat pump and so are the % of savings.

An AC Condenser sitting in the Sunlight will naturally be a lot hotter in temperature than one sitting in the shade. For example park your car in the sunlight and then park your car in the shade? Where will the surface of your vehicle be hotter/cooler? It has nothing to do with air temperature at this point. It is the heat of the sunlight that is raising the temp of the coils in the condenser just like it would raise the temp of the surface of a vehicle parked in the sun instead of the shade.

I live in TX. I have some experience with this.

A typical small AC will have to dissipate about 5kW of heat through the radiator. If you put it into the sun, it will additionally need to dissipate the energy it gets from sunlight. Assuming that the area exposed to the sun of the radiator is about 0.25 square meters, it will receive at most 250W of energy from the sun (assuming that it is painted black and perfectly absorbs all light and miraculously doesn't emit anything).

This means that you can save at most 5% by putting the radiator in the shade.

(Metal sheets heat up quickly in the sun because they have low heat capacity. They also cool down quickly if you blow on them with a fan. Just because something feels "hot", it doesn't mean that a lot of energy is stored inside)

It's not just the unit itself, but everything the sun shining on nearby heating the air which is getting blown through the coils. The temperature increase effect is also superlinear; the efficiency goes down as the temperature increases so 250W extra heating might cause an extra 120W of loss (that number is made up, but the amount is greater than zero).

Swamp coolers are useless in high humidity climates. And similarly, shade isn't as cool relative to direct sunlight in high humidity either.

The water removes more heat from the coolant; the swamp cooler isn't for the inside of the house it's for the compressor itself.

I disagree. There isn't much difference in the _air temperature_ of air "in the shade" versus air not in the shade.

Air temperature isn't the only thing that heats a condenser. Solar radiation does that too.

It’s a difference of over 10 degrees in many places.

Reply on news.ycombinator.com