How to build a pop can solar heater

Did the rolling blackouts of #DarkNL 2014 get you down (and cold)? The key to staying warm may be in your recycling bin.

The power outages and rolling blackouts in Newfoundland this past winter left most people bitter about having to conserve energy. Residents of St. John’s were irritated at having to unplug unused lights, turn down thermostats and wash laundry during off-peak hours. Instead of thinking about energy conservation as an annoyance (or something we all do when the government implores us to conserve during emergencies but quickly falls out of style when the power is back online), we got a group of friends together inspired to think about how we can be more energy self-sufficient. We want to be able to stay warm and feed ourselves without necessarily relying on power from ‘the grid’.

The group—informally called ‘Energy Club’—formed out of a DIY Energy Fair we organized last January (the outcome of sitting in the dark, cold and freezing for three days!). The ultimate goal of the Energy Fair was to shed light on the perils of a centralized energy monopoly by showcasing do-it-yourself projects and spurring discussion of alternatives. There is no good reason to be pursuing fracking on the west coast or megaprojects like Muskrat Falls for energy when there are so many alternatives for smaller-scale and decentralized energy innovation, like wind, geothermal, and solar energy. We learned from folks at the Energy Fair that a good way to kick-start community investment in renewable energy generation would be by introducing “feed-in tariff” legislation to allow the public to sell excess power back to the electricity grid (which is currently outlawed in the province under Muskrat Falls enabling legislation).

The Energy Club builds Do-It-Yourself devices for harvesting energy that are low-cost and environmentally friendly. We want to demonstrate to others that we can start small and we can start now. Our first project was a pop can solar heater.

A pop can solar heater is an air heater that uses the sun to warm the air in a building. The basic principle is that air is warmed by passing through aluminum cans that are placed in the sun. There are several good resources online for building DIY pop can solar heaters, both small prototypes and large-scale units. For examples, click here, here, and here. The heaters can also be purchased from Newfoundland-based company CanSolAir.

The Energy Club Pop Can Solar Heater Prototype

These steps outline how Energy Club built a pop can solar heater prototype, but they can be adapted to suit other sizes and styles.

Step 1. Collect pop or beer cans (our prototype took 20 cans). Soak cans in hot water and soap, rinse thoroughly, and let dry.

Step 2. Use a regular kitchen can opener to cut the TOPS off the cans.

Step 3. Use a drill to make three holes in the BOTTOM of each can. The three holes create a small turbine effect, slowing down the air as it passes through the cans. There are alternatives to the three-hole style, such as using curved metal snips to cut a small turbine into each can, or simply drilling one large hole into the bottom of each can.

Step 4. Build a frame for the solar heater. Make sure the frame is the same size as the piece of glass or Plexiglas that will be used to cover it. Use a hole saw to drill a hole at the top and bottom of the unit. The bottom hole will pull cold air inside the unit and the top hole will allow the warm air out.

Step 5. Insulate the frame box with cardboard or another type of insulation.

Step 6. Line up cans into columns and attach them together using a high heat-resistant adhesive (e.g. silicone) or aluminum duct tape. Whatever material is used to keep the cans together must be able to withstand high heat. Regular duct tape is not sufficient as the glue will melt.

Photo by Jenne Nolan.
Photo by Jenne Nolan.

Step 7. Spray paint the entire unit black, preferably using high heat-resistant spray paint.

Photo by Jenne Nolan.
Photo by Jenne Nolan.

Step 8. Secure glass or Plexiglas onto the top of the unit using tape, silicone, or a fastener. The unit should be as air-tight as possible.

Step 9. Attach recycled computer fans (or another type of fan) to the holes in the top and bottom of the unit. The bottom fan will be the ‘intake,’ pulling cold air into the unit. The top fan will be ‘outtake,’ pulling warm air out of the unit. For large size units bigger fans or more wattage may be required.

Step 10. The unit is ready! Our prototype was not durable enough to install outside, but large units should be built to weather the elements. Large units (about 4 by 8 feet) are best installed on a south-facing wall outside of the house. Installing a unit outdoors involves drilling two holes in the wall. One hole will align with the bottom hole on the pop can heater and the other will align with the top. Flexible tubing, such as dryer vent tubing, can be used to connect the holes in the units to the holes in the wall. Cool air from inside the house will enter the unit through the bottom, heat up by travelling through the pop can heater (which is on the outside of the house), and flow back into the house through the top hole. Click here for an example of the outdoor installation process.

We tested the Energy Club pop can solar heater prototype on a sunny June day in St. John’s. Without any fans the unit still worked. Hot air could be felt flowing out of the top hole, despite the unit’s many flaws and imperfections. For example, the unit is far from air-tight. Gaps in the box (i.e. wood that does not line up perfectly) and cardboard allow warm air to escape before reaching the top hole. Prototypes similar to ours have reported output air temperatures of about 65 degrees Celsius!

Tips and Lessons Learned

  • Scavenge as many materials as you can. Pieces of wood and chipboard, cardboard, and pop and beer cans can be rescued from the garbage. Old windows can be reused as glass for the unit.
  • Be careful if you use silicone — the fumes are toxic so use it outdoors and give plenty of time to dry.
  • Spray paint works best when the can is upright. Prop your unit up on an angle as you spray paint.
  • There are hundreds of different designs for pop can heaters. Look around online and note the techniques, styles, and materials that would work best for you. A variation of the pop can solar heater is the screen solar heater.

If you would like to share one of your own DIY (do-it-yourself) projects with Indy readers, email Justin Brake at justin (at) theindependent (dot) ca.

Editor’s note: If you would like to respond to this or any article on, or if you would like to address an issue we haven’t yet covered, we welcome thoughtful and articulate Letters to the Editor. You can email yours to: justin(at)theindependent(dot)ca. Not all letters will be printed, but all will be read.

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