SOLAR HEATERS DIY

SOLAR HEATERS 

DIY -PROJECT

In this article we will take a look at almost free way to heat a small room or bunker, even in winter sun weather conditions. Parts or materials for this DIY project are very cheap.We will mention beer or soda can solar collectors and screen solar absorber heaters.For soda cans optimal 'd be larger box containing 100 to 120 beer/soda cans.The bigger ..the better! You can easily produce up to 48 to 60 C+ heat for room heating with these projects.Only part which actually uses electricity is small pc fan working on battery or even on small solar panel making small amount of current for ventilator.You can also make small circuit with thermistor and regulate when ventilator switches on.

Two of the more popular designs are the pop can collector and screen absorber collector. The pop can collector uses columns of ordinary aluminum soda pop cans with the ends cut out.The sun shines on the black painted pop cans heating them, and air flowing through the inside of the can columns picks up the heat and delivers it to the room. The screen collector uses 2 or 3 layers of ordinary black window insect screen as the absorber. The sun shines on the screen and heats it, and the air flowing through the screen picks up the heat and delivers it to the room. For best heating results you want to go larger. A 4ft by 8 ft collector is about the minimum to contribute some real heat or in metric,cca. 2 square meters of surface.

*screen solar absorber is on right side of picture

Basic principle is that sun shines through the glazing, and hits the collector absorber heating it. The air flows through the inlet and over or inside or through the absorber picking up heat as it goes. This heated air then flows out the collector outlet and into the room being heated. The main differences between air heating collector designs have to do with how the air flows over the absorber.

In full sun, the incoming solar energy is about 1000 watts per square meter of collector area. Of this 1000 watts/sm, about 10% is absorbed or reflected by the glazing and never gets to the absorber. Of the remaining solar energy, about 95% is absorbed by the absorber. So, for the 1000 watts/sm that arrive at the collector face, about 850 watts/sm end up actually heating up the absorber. 

Crucial factor with these simple project is isolation material and air flow.For bigger solar collecting surface you will need larger ventilator for airflow intake.

Building the Soda/Beer Can Collector

1. Collect the cans.
2. Clean the cans.The cans typically have some residue and need to be cleaned.

3. Cut the ends out of the cans. You can either punch bigger holes.sand-off entire bottom or make (most complicated and time consuming) ventilator wings pattern.With latter method hot air is naturally rising and spinning in solar collector. 

4. Cutting out the top of the cans

5. Gluing the can columns.For gluing you can use high temperature silicone caulk. Its a good high temperature material that remains a bit flexible and does not stink or out-gas after its initial cure.Keep in mind that the cans must not only be glued together but also sealed.

6. Preparing the cans columns for painting.You can just wipe cans down with acetone.

7. Build the manifolds.There are manifolds along the top and bottom of the collector that distribute the air evenly to each can column.Best is to use hard materials like wood,plywood or even metal.

8. Install the inlet and outlet vents.Cut holes in the back of the collector for the inlet and outlet vents.

9. Assemble and paint the absorber. Best way is to use high temperature resistant BLACK paint and to assemble heater in such way that hot air naturally flows to upper area of heater. Everything must be sealed and insulated.For cover you can use UV resistant Plexiglas, glass or whatever transparent material  is available and convenient.

Building the Screen Absorber Collector

1. Build the absorber frame.The absorber frame holds the three layers of screen in place.

2. Staple or screw screen to frame.You can use fiberglass screen.Black aluminum screen might be a better choice for long life.Just staple or screw the three layers of screen directly to the sides of the collector box.This would save making the frame to hold the screen. I would make a few guide marks at the top and bottom of the collector box, then staple the screen across the top, then pulling the screen tight, staple across the bottom, then putting a bit of tension on the screen staple each side. Remember that the screen needs to be close to the back of the collector on the inlet end and close to the glazing on the outlet end. About a half inch space is normally allowed between each layer of screen.

3. Install the inlet and outlet vents.

4. Mount the absorber frame in collector box.Place the frame in the collector box. It should be tilted so that at the inlet end, its near the bottom of the collector box, and on the outlet end it should be near the top of the collector box. Secure the frame to the box with a couple screws on each side that extend through the box and into the frame. Seal any gaps between the edges of the absorber frame and the collector box with something like foam or silicone caulk.Note that the absorber is tilted so that it is close to the bottom of the box on the inlet end, and close to the top

of the box on the outlet end.

5. Connect inlet to absorber .On the inlet end, press the three layers of screen down onto the inlet flange and glue them in place with polyurethane glue.Air has to flow through the screen to get to the outlet vent.1) cut the hole in the back of the collector for the inlet vent, 2) install the screen absorber, 3) cut an opening in the screen matching the inlet vent hole in the back of the collector, 3) apply Great Stuff to the inlet vent (which is a start collar) and push the inlet vent down through the screen and the hole in the back of the collector.

5. Install the inlet baffle.A baffle is used across the bottom of the collector to spread the inlet air more evenly across the width of the collector and to keep the inlet air from impinging directly on the glazing (which would increase heat loss). The ideal flow is for the inlet air to spread out evenly over the screen, and then flow through the screens toward the back of the collector picking up heat from the solar heated screen layers. This baffle is made from some aluminum soffit material

You can expect similar results from both types of solar heaters.Screen solar collector is simpler and faster to make but probably won't last long if you don't use metal sheets.In summer days small soda can collector will produce 65C of heat while screen solar collector will do 67C.In winter conditions up to 45C on outlet is expected. Off-course,materials,surface and weather conditions are all variables in this equation.You are free to experiment and internet is full of great ideas for these types of projects.