Solar Water Heater – Metro Manila

The water coming into my home comes from a communal water tower, I don’t have any heater, so the temperature that the water comes in is the temperature that I experience when showering, washing the dishes, etc. When it’s very hot outside, the water comes in kind of warm, when it’s even slightly cool outside, the water comes in very cold.

Instead of going out and buying a water heater for my shower which would eat up electricity, I started researching for a way to use the sun to heat my water. We certainly have enough sun and heat in Manila to make such an idea work! After watching a number of videos on Youtube and reading a few different sites, I understood the basic idea of a solar water heater and how it makes use of thermal siphoning.

The basic idea is that you have a sealed insulated box which features a transparent face (glass/plexiglass) and  some water pipe (copper, pvc, hose) running inside it. Cold water goes in at the bottom and as the sun hits the pipe and warms it up, the water rises (thermal siphon) and then eventually exits at the top of the box. You can cycle this same water around until it reaches your desired temperature. Scroll through the images below to better understand how a solar water heater is made.

The following pictures are a custom design based on what I’ve read online and may not necessarily be the best way to make a solar heater. At some point I’d like to replace the hose with copper, since copper would conduct heat much better. I’d also like to replace the plastic covering with glass or plexiglass for better insulation. Both changes will require a bit more cash and complexity. Also note that I forgot to take pictures at some steps, I’ll make up for that in the image notes :)

 

Base Box

This is the basic box, measuring 4ft x 2ft. The sides are made up of 1inch by 4inch planks and the base is a piece of plywood. Insulation has been glued and stapled into the sides and base. A sample of the insulation is shown in the middle of the box.

 

Stand-offs

A section of 1inch x 4inch plank was cut into smaller sections to use as standoffs for a piece of metal that will be fitted later.

 

Glueing the standoffs

A total of 6 standoffs/supports are glued in and then weights are put on top until the glue dries.

24 gauge metal sheet

After having no luck at the junk shops, I bought a 8ft x 4ft sheet of metal (24 gauge). A section of this will be cut to fit inside the box and will act as a heat conductor and a mounting point for my water pipe.

 

Cutting sheet metal by hand

I didn't have anything that was able to cut through this thickness of metal. I used an old cheap knife (~p70) and a hammer. It's not ideal but it works.

 

Engine coating spray paint

The metal was spray painted black (to help attract the sun) with an engine coating spray which can hold up to high temperatures. The metal is held in place with screws going into the standoffs installed earlier.

Spray painted hose

Next I drilled a hole at the bottom side for the cold input hose and then another at the top side for the hot exit hose. Next I installed regular green garden hose. I drilled holes into the metal and used wire to hold the the pipe in place. I then spray painted the hose black. Connectors are joined onto the hose ends so that it can be easily connected and disconnected to different water sources. A sealant was used around the hose holes to ensure heat stays within the box. (Ideally this would be copper pipe rather than a garden hose)

Plastic cover for solar water heater

I cut a sheet of plastic (about the thickness of a playing card) and stapled it to the top of the box. The idea is to keep as much heat within the box as possible to help heat the water as it passes through the hose. (Ideally this would be glass or plexiglass)

Duct tape solar heater

Duct tape was used around the edges of the box to ensure a good seal on the plastic sheet. It was then spray painted black so that it looks tidier. I placed a thermometer inside the box so that I can get an idea of the internal temperature.

Solar water heater in Manila, Philippines

The finished solar water heater has been placed outside, at an east facing wall - meaning it will heat up primarily in the morning. No water pipes have been connected yet. The internal temperature of the box increased from 30 degrees celsius to 40 degrees celsius within an hour of indirect sunlight. I'll update the post once I've measured the internal temperature during direct sunlight.

 

galvanized pressure tank

I bought a galvanized pressure tank on sulit.com.ph for p1700. This will hold the water that circulates through the panel, getting hotter each time it passes through. In this picture, I had started to wrap the tank in the same insulation that was used inside the panel; this should hopefully keep the water hot in the tank right through to the night.

 

water tank connected to solar heater panel

This picture shows the water pressure tank fully wrapped in insulation and spray painted black. The tank is sitting on top of a 3-legged table. There's a ball valve inline with the cold water pipe so that the circulation of water can be stopped at any point. There's also a faucet for getting hot water out of the tank. While the water is coming out extremely hot (hot enough to burn you), I'm experiencing pressure issues, the thermosiphon effect doesn't seem to be working as well as I'd seen in earlier tests. I've bought some copper tubing which will replace the hose inside the panel and should make the panel much more efficient.

 

Copper tubing in solar water panel

After much searching, I managed to find someone who could bend the copper tubing (labor cost p800). It's not possible to bend the tubing by hand without the correct tools, since it would simply kink closed. I had asked for 170 degree bends so that the pipe would gradually rise inside the box at each bend. Unfortunately the result wasn't perfect - I'm not sure if it will have an effect on the performance.

Posted in Green Living, Sun

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