Pop Can Solar Collector

Here at the Welcome Homestead we have electric baseboard heating. Yup, that’s bad! The only advantage is being able to heat individual rooms on their own but it is still pretty pricey. Being hooked to the grid leaves us dependent on the prices and reliability of others. We have been exploring alternative ways to power and heat the house and it seems that we have to return to older technology in order to control costs and achieve independence. Sure, power generating stations give us reliable power on demand and generally aren’t subject to the whims of nature like solar and wind power generating systems are but at what cost? Nuclear plants have incredibly toxic waste to dispose of, coal and natural gas plants have carbon emissions issues and hydro plants flood vast swaths of land in order to provide enough water to power the turbines. These plants are also very expensive to build and maintain and the transmission network needed to deliver the electricity to the customers is expensive and soaks up power along the way so what you put in to the line at one end isn’t what you get out the other end.

As with everything else we consume, this leaves us with three choices: Status quo, change or do without. Since it is difficult to get along without electricity and maintain the lifestyle and technology that we are used to the last option is out. Sure, a lot of us would love to go live in a cabin in the middle of nowhere and enjoy the peace and quiet but we humans are social animals at heart and most of us would at least like to communicate with our friends and loved ones from time to time and that’s a bit difficult without some sort of power. We could go with the status quo, pay what the power companies charge us and have our convenient power any time we need it. If people are happy with that, more power to them (pun intended). It is nice to have the convenience to flip a switch and cook, do laundry or turn up the heat whenever we want. However, for some of us who would like to save a few bucks and perhaps be independent of big business there are a few alternatives we can explore on our quest for peace and self-sufficiency.

This project is the pop can solar collector. It’s by no means new technology, in fact it’s basic physics that we have known since man (or woman) first stood in the sunshine and felt it’s warmth on his (or her) face. Touch a rock or some pavement that has been in the sun for any period of time and, of course, it’s hot. The sun shines down on our heads for free and we fail to utilize this amazing resource. The solar collector is simply a way to gather that heat and distribute it in an orderly manner. There are companies out there who manufacture solar collectors like this, in fact one buys pop cans from a recycling facility and reuses them in their units. However, we are doing this on the cheap so we are trying use as much scavenged materials as possible.

This particular project will be fitted into a window. Others are self-contained units which we will explore at a later date. We start by measuring the window that will be the new home of our solar collector then build a box the size of the window and deep enough to accept the width of the pop cans. There is a piece of wood cut to contain the rows of cans on the top and the bottom and holes cut in these pieces to accept the tops of the cans. Each can is washed in dish detergent so the paint will stick to the can and a hole is punched I the bottom of the can so air can get through when the cans are placed end to end like tubes.

After the cans are placed in the box they are secured with wires and then the entire unit is painted black with high temperature frame and roll bar paint. Once the paint is dry the unit is placed in the window, secured and sealed and the fan installed on the bottom. As the sun heats the cans air is blown through the unit, picking up heat and distributing it to the room. Pop cans are used because of the superior heat transfer qualities of aluminum. This particular project has hardly been professional and still needs some tweaks such as improving the seal on the box but it is operating in principle as expected. It does keep the kitchen a few degrees warmer than it would be without it although we don’t have official temperature stats at this time. The temperature inside the unit gets off the scale of the thermometer which tops out at 120 degrees F. The fan is a bathroom fan which is rated at 70 cfm and draws 100w of power. If that fan can prevent the 1500w baseboard heaters from coming on it’s a big savings right there.

Some improvements would make this unit more efficient, for example, we plan on blocking off the two doorways out of the kitchen to prevent heat from going into other parts of the house which should make the kitchen warmer due to only having to heat a smaller space. Sealing the unit better would make it more efficient and putting a duct from the unit to the center of the room may distribute the heat better. We fully appreciate that it only works in direct sun but anything that can reduce our costs and environmental footprint is a step forward.

This idea can also be built to work without a fan, using only the convection of the air inside the unit to power it. As air is heated it rises and exits out the top of the unit and draws cooler air in from the bottom. Slits as wide as the unit would have to be cut where the holes top and bottom currently are to make this work. Some in the real estate profession have been using ideas similar to this in unoccupied houses to keep the house temperature above freezing so the pipes don’t burst.

The cost of this project came out to about $70. There were extra screws and brackets left over and can be used for other projects. It’s built of ½” plywood for light weight and the fact that it is mounted inside the house means it doesn’t need insulation. Self-contained units meant to be mounted outside would need to be built of thicker wood and likely insulated to keep the heat inside the unit.

This is just a basic project and is not meant to be the end all and be all of alternative options. We plan to build on this idea and hope it can inspire others to think a little outside the box so we can move toward a more environmentally friendly and sustainable world.

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