The solar air heating collector is a quick and simple way to get started on alternative energy. Although is a quite simple array, it can make you save a lot of money on energy bills. Just basic thermodynamics, not moving parts, cheap and effective.

Solar Air Heat Collector
Installed Solar Air Heat Collector

How does it work?

Thermosiphon Diagram – Hot/Cold Air Flow

The two principles at work are:

Dark surfaces absorb light. Any black colour object absorbs all wavelengths of light and reflects none, that’s why it appears black. As you know, light is energy and as being absorbed into something it can turn into heat. The main part of the box will have black-coloured material in it to capture heat from the sun.

That heat gets transferred into the air in the box. As the air warms up, it wants to rise out of the box. As the warm air rises, it pulls cooler air into the box. This is knowns as the thermosiphon effect. This is a method of passive heat exchange, based on natural convection, which circulates a fluid (air in this case) without the necessity of a mechanical pump.

Step by Step DIY!

The most effective and efficient design uses black metal window screen as the heat collector. This works great because it has a large surface area and is designed for maximum airflow already. If you can get black metal window screen, that is the best. If you can’t, it’s easy to spray paint the screen black.

How much would you save?

If one heater can keep the living room warm for all the daylight hours, that’s 6 to 10 hours of not having a heater on. Our average living room would normally need a 3200-watt electric heater. If it’s running for 10 hours, that’s 32-kilowatt hours (kWh). Let’s say electricity costs you 19 cents/kWh. That’s over $6 per day or $42 per week. From October to March, that’s about $1022.

What would you do this winter with your extra $ 1.000?

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4 COMMENTS

  1. First, what crap. The solar isolation on a sq. ft. of vertical collector is about 200 BTUs a hour between 9 am and 3 pm. A well made air heater will capture and bring 100 of those BTUs into the house. allowing for cloud cover, often 6 days in a row where I live. A sq. ft. of collector will bring less than 100,000 BTUs into a house per year.
    I pay 70 cents delivered for 100, 000 ( a therm ) of nat. gas. I have , and have had for 20 years, commercially made selective surface, low iron glass 4 by 8 collectors on my house. I bought them used when nat. gas was over $ 1 before fracking. At 70 cent nat. gas, these collectors are worth $22 a year to me. Each.
    You can write a clear sentence. You have some education. SO, are you a liar, or, a fool.

    • Hi Karl!

      Thank you for your comment.

      As the article says, “average living room would normally need a 3200-watt electric heater. If it’s running for 10 hours, that’s 32-kilowatt hours (kWh). Let’s say electricity costs you 19 cents/kWh. That’s over $6 per day or $42 per week. From October to March, that’s about $1022.”

      This means, that you can save that money if you have that heating electric system and pay that amount of money per kWh and use it that amount of time.

      As it seems, that’s not your case, especially if you live in a place where cloud cover is often 6 days in a row and use cheap natural gas.

      The aim of this article is to show one real experience and discuss just one alternative energy option for house heating systems.

      There is not the intention of fooling or lying, I encourage every reader to deeply inform before taking any action.

      I trust that the reader will analyse their energy options and choose the one that suits better for their area and pocket, as you did.

  2. Is it the most efficient design? The air will go up in seconds with a flat vertical surface, barely enough time to heat up sufficiently. In the other designs I have seen, the air usually goes through an aluminum pipe that zigs zags from the bottom hole to the top hole, so the air has a much longer way to go and to collect heat.

    Most DIY designs use recycled aluminum cans that are cut on both sides, assembled into the zig-zag pipe and painted in black. I tried building one, but collecting cans is a hassle when you never drink any can, and cutting and assembling them into a pipe is even worse when you only have a kitchen table to work on and not many tools, I gave up. It’s a project that should be done collectively, it’s not fun otherwise…

    You need a heating system mostly in winter, which is also the season when the sun sets down the earliest. So a more useful heating system if you want to heat the room after sunset might be a regular water heating solar panel, which you can purchase as a kit for cheap or build yourself (there’s a DIY link somewhere on this site). You’ll need to couple this solar panel(s) to a big water tank and to water pipes, usually integrated into the floor. Much more complex than a simple solar air heater though.

    The bungalow on the picture looks like these cardboard bungalows we see flying away in every tornado, and I’ll be damned if this solar heater faces south, there’s only one window on this side…

    • Hi chimel31, thank you for your comment.

      The efficiency on the design of a Passive Solar Air Heater (PSAH) will depend on several factors such as the interior depth of the frame, the Insulated Back (polyisocyanurate is recommended), Matte Black Interior, Solar Absorber, Air intake/outlet and Glazing (polycarbonate, acrylic or tempered glass).

      The solar absorber material and airflow is where, as you say, the design differs. This can have a big impact on the efficiency and effectiveness of the unit as a whole, finding the right combination of heat gain and air throughput may require experimentation.

      However, if you want to know more about this check out this comprehensive comparison test which includes methodology, graphs, thermal pictures and other details.

      In these findings, the best performance overall as well as the cheapest and easiest to build was the Screen Type (the one of this post). The Aluminum Tube Type or the “can” design, showed a -40 to -50% compared to the Screen Type. It was the most expensive to build and really hard to equalizing airflow across all the tubes.

      I agree that it can be hard to collect so many cans, especially when you are not a regular consumer and every project will be better if shared.

      I also agree that having a way of storing energy during the night will be really useful, and a water heating system will help with that.

      The idea of this post was just to share a simple and concrete experience.

      For more information about Solar air heaters I recommend this 2016 review :
      Solar air heaters: Design configurations, improvements methods and applications – A detailed review”

      Thank you!

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