DIY Solar-Powered Air Conditioner for Beginners

While conventional air conditioners are usually fairly complex, comprising several units mounted inside and outside the building, a DIY solar-powered air conditioner can be simple and is made from equally simple parts. In this DIY build, we’ll show how to put together simple yet effective solar DIY air conditioners.

The Concept

These types of solar power air conditioners work by drawing warm air from the room through an ice-filled container. This cools the air, which is then blown back into the room, effectively dropping the ambient temperature inside the space. This may sound overly simple, but it is really very effective.

How It Works

Ice is kept cold in a conventional styrofoam or plastic ice box. An electric fan mounted through the ice box lid draws warm air over the ice, cooling it as it does. The same fan forces the now-cooled air back into the warm air column, causing a drop in temperature. The fan is powered by modest solar panels, meaning the cooling is affordable and environmentally friendly.

In its simplest form, the solar air conditioner uses only an icebox, a 12-volt fan, and suitable PV panels(solar panels). However, adding a couple of extra components can make the unit far more useful and effective.

The Basic Concept

A small fan is mounted through the lid of the container and circulates air through it. Air entering the container exits through a 90° PVC plumbing elbow fitting also fitted through the lid.

The container is filled with ice, which cools the introduced air, which then exits at a significantly reduced temperature. Although very simple in theory, a portable AC unit works surprisingly well.

The layout of basic solar air conditioners is illustrated below in Fig.1.

Although styrofoam iceboxes are affordable and work well enough, they are fairly flimsy and prone to getting damaged. So it would be a good choice to use a good quality plastic example for your solar air conditioner.

What You Will Need

• Plastic ice box (approximately 9 to 15 quarts). Try to find a box that has a flat lid without any ridges or textures.
• High capacity 12 volt computer fan ± 1,500 to 2,000 rpm (approximately 5″ x 5″ x 1″ or 120mm x 120mm x 25mm)
• 12-volt solar panel of between 2 and 5 watts output
• In-line on/off switch
• 3″ 90° PVC sewerage/water PVC pipe plumbing elbow
• Silicone sealant
• Electric jig saw with a suitable plastic cutting blade
• Sharpie marker
• Masking tape
• Electric drill and drill bit selection
• Stainless steel or brass nut and bolt selection
• An AC/DC multimeter

The Cooler Lid Construction Process

The first order of business is to mount the fan and the cold air outlet onto the lid of the icebox. Fig. 2 illustrates the approximate size of the fan cutout hole. It should be big enough not to impede the fans’ airflow, but not so big that air bypasses the hole.

Before cutting the fan airflow opening, place the fan in position and mark the 4 mounting hole positions. Now put the sharpie or marker between the fan blades and mark the fan airflow opening as accurately as possible.

The fan should be mounted towards the edge of the lid. Now repeat the process with the 3-inch outlet pipe. The approximate positions of the lid components are illustrated below in Fig. 3.

Now drill a hole on the inside of the marked holes, as indicated in Fig. 4. The hole must be big enough to allow the jigsaw blade to pass through it and rotate freely.

Now, starting at the pilot holes, use the jigsaw to cut out the fan and exit pipe openings. Try to cut the exit pipe hole slightly inside the marked reference to ensure a snug fit. Then, drill the 4 mounting holes to accept appropriate mounting bolts.

Mount the fan in position with the power leads facing outwards towards the edge of the lid. Now push the plumbing elbow through its hole, facing it away from the fan position. The elbow can be sealed in place with PVC cement or silicone sealer. The completed lid assembly is illustrated in Fig. 5 below.

This completes the cooler construction part of the solar AC unit. Now we can move on to the solar source components.

The Solar Powered Cool Air System

This solar air conditioner’s cooling component is relatively simple and has low power demand requirements. This makes a solar AC unit easy to run on a very simple and modest solar setup. That is, of course, if you only intend to use it during peak sun hours.

With the inclusion of a couple of additional solar system components, you can extend its use considerably, though. More on that later. The basic AC unit layout for daytime use only is illustrated below in Fig.6.

At its simplest, the solar part of this project will require only a couple of components. A 2-watt solar panel, two lengths (red and black) 1.5 mm panel wire, a soldering iron and solder wire, and a length of heat shrink tubing

You’ll have to decide how far you would like to be able to place the solar panel from the AC. This will dictate how long the system leads will be.

Fan Wiring

Note: the solar panel and the PC fan will be fitted with appropriate plugs that will be cut off during installation. In most cases, a PC fan will have a three-wire harness. These are typically colored red, black, and yellow. As per normal, the red wire is positive 12 volt DC, and the black wire is negative. The yellow wire is usually the fan speed sensor and controller you won’t use. You can tie this back and insulate any bare ends with shrink tubing.

Most computer CPU fans are not really that sensitive to reverse polarity wiring, i.e. positive to negative and vice versa. Some are, though, so the next step is fairly important.

Wiring the Solar Panels or Panel

This can be tricky as many solar panels don’t clearly indicate which leads are positive or negative. That is why they have very specifically shaped plugs that can only be connected in one orientation. In this case, however, that plug has been cut off. This is where the multimeter will come into play.

You’ll need to put the panel in the sun to be dead certain you have the leads correctly connected. Then you can read the output voltages on the panel leads to establish polarity. You can easily do this using a multimeter. Fig. 7 below illustrates this process.

Keeping in mind that the red multimeter lead is positive, part A of the illustration shows the correct orientation. Part B displays a -, or negative symbol, ahead of the voltage reading, indicating incorrect orientation.

If you have a part A readout, mark the lead the red multimeter lead is in contact with. This is easily done by wrapping a tab of masking tape around the positive lead. Mark the tape with a + symbol. This way, you won’t run the risk of potentially damaging the fan.

Extending the Panel Leads

If you want to install an on/off switch, it’s best to do it now before the panel is connected. Its potential position is indicated in illustration 6. NB: Always try to keep the switch on the positive lead in all installations.

If you need to extend the leads from the solar panel, use the red and black panel wire to do so. Keep the red wire with the switch on the panel’s positive lead. Soldering the extensions or joints between the panel and the fan is the best practice. Use heat shrink tubing to insulate all your joints.

Connecting the Fan

The solar panel leads can now be soldered onto the fan leads. Just keep track of that positive wire and make sure it goes onto the correct fan lead. Again, use heat shrink tubing to insulate all joints.

NB: This is one good reason for including an on/off switch in the circuit. Without it, as soon as the solar panel is energized, even by artificial light, the fan will run. This can cause some rather unpleasant or even dangerous results.

A Better Mousetrap

The example detail above is a very simple example of a solar AC. With a little tweaking, a far more user-friendly and feature-rich example can be built.

Adding Batteries

By adding batteries to your build, the AC can be used 24/7. So at night or in overcast, low-light conditions, you can still have cool air on tap. And, unlike traditional air conditioners, it’s 100% portable and AC power independent.

That said, adding battery convenience to the system will require additional equipment. And some of them may be a tad costly. However, the convenience of air conditioning anywhere, anytime, is hard to beat.

What You Will Need

The solar AC detailed above will remain largely unaltered, with the exception of two extra components. These are a charge controller and one or more batteries. Here is a brief explanation of what they are.

• The charge controller: This component will gather the energy your solar panel harvested to charge the battery.
• The battery: This one is pretty much self-explanatory. This component stores power harvested by the solar panel for use in hours of darkness or low light.

With home or RV solar systems where 110 or 220-volt AC power is required, an inverter would be included. But as we are running a single 12-volt fan, they are unnecessary. Unless, of course, you choose to run a grid voltage AC fan.

An example of an advanced solar-powered AC is pictured below in Fig 8.

In Closing

Having an air conditioner on those sweltering hot days needs no selling. No matter how small or simple it may be. And having air conditioning that includes solar panels that can be multi-functional is a sure winner. The example described here uses basic store-bought parts and can be assembled with a minimum of technical skills.

Not only that, if you consider how much energy they can save, building one is a truly worthwhile project.

ADDITIONAL NOTES:

The solar air conditioner we have detailed here is relatively modest. If you need more cooling power though, it’s really simple to beef up all the components to increase output.

We have showcased a cooler box of between 6 and 9-quart capacity. If you consider coolers ranging from 25 to 200-quart capacities available, the sky is really the limit. Well, that and your budget of course as all components will have to be upgraded.

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