DIY Solar Space Heating

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Photo: Build It Solar.

Mrs. Homegrown, who spent her formative years in the mountains of Colorado, made fun of me this morning as I noted the “cold” temperature . . . 60°F. It was the first ironic “brrrrrr” out of her mouth, letting me know that we’ve transitioned from the hot smoggy season to the the less hot smoggy season here in Los Angeles.

In the northern hemisphere it’s time to consider heating. The always useful Build-It Solar blog has a detailed link to a DIY solar space heating system in Virginia (pdf).

Collector panels mounted on the roof heat a reservoir which is circulated through a floor-based radiant heating system. It even has an Arduino based data acquisition component that tracks performance. There should be a DIY Nobel Prize for this project!

If you live in a place that’s both cold and sunny in the winter, solar heating has a lot of potential. In fact, I’m much more intrigued with solar space and water heating then I am with photo-voltaic panels.

The Sundiner–A Groovy 1960s Era Solar Cooker

Sundiner solar cooker

Backywards beekeeper Dennis of The Buzz in the Dale, was nice enough to gift me his vintage Sundiner solar cooker that he found at a garage sale a few years ago.

Sundiner solar cooker

Resembling a cross between a portable 1960s record player and a satellite, the Sundiner is compact, light and easy to carry.

Sundiner solar cooker built in thermometer

A built in thermometer lets you know when you have hit cooking temperatures. The unit is so efficient, that when I set it up at noon it hit 350° F within minutes (in February!).

Interior of Sundiner solar cooker

The Sundiner has one big disadvantage. There’s only enough space in the business end to fit a 9 inch square shallow baking tin. And that tin, depending on the time of day and year, may be at a steep angle. Thus the Sundiner is more of a solar grill–anything liquid will ooze downwards and make a mess of the difficult to clean, unidentifiable space age insulation material. Grilling is really not the best application of solar energy–you lose the smoky flavor and grill marks you get with fire–which is probably why the Sundiner never caught on. More recent solar box ovens that I’ve seen, both commercial and homebrew, have shelves with adjustable angles, making it easier to use them as crock pots.

Nevertheless, I admire the efficiency of the design–the legs also double as a handle and the panels unfold and snap together in seconds. It’s easy to aim. The instructions are even printed on the back of the panel that covers the reflectors.

Sundiner solar cooker instructions

More info via the April 1963 issue of Desert Magazine:

Here’s a new product that suits desert living as few others can—it collects and concentrates the heat of the sun and allows outdoor cooking without fuel or fire. They call it the Sundiner. The technical description is “Solar Energy Grill.” Sundiner is a compact unit, 17-inches square and 6inches tall. Fold-out mirrors are metalized Mylar plastic, supported by polypropylene holders. The mirrors focus the sun’s heat on the lower section of the cabinet, where heat slowly builds up to a maximum of about 450 degrees—plenty to cook with. Directly below the apex of the mirrors is an oven enclosure. Plastic foam insulation and a pair of glass plates prevent excessive heat loss. The solar energy grill works in this simple way: point the mirrors toward the sun for a few minutes until the right temperature is reached (built-in heat indicator dial) and pop a tray of food into the oven. There is no fire or fuel to handle. Sole source of cooking stems from the collected, concentrated rays of the sun. Here is a sample of how long various meats take to cook: Hamburgers, franks, and fish, 15 to 20 minutes. Steaks and fillets, 20 to 25 minutes. Quartered chicken, 25 to 30 minutes. Temperature variations are possible by turning the Sundiner toward or away from the sun. The advantage of the Sundiner is that it can be used as a safe substitute for a fuel-fired stove on beaches, parks, decks of boats, and other restricted areas. Carrying handles are standard. The price is $29.95. From Sundiner. Carmer Industries. Inc., 1319 West Pico Blvd.. Los Angeles 15. Calif.

How To Dry Food With the Sun

Drying Apricots in Southern California–early 20th century style.

Dehydration is one of my favorite food preservation techniques. Drying food concentrates flavor and is a traditional technique in our Mediterranean climate. Best of all, drying food is one of the best applications for low-tech solar power. In many places, you can simply set food out under cheesecloth to dry in the sun.

But there’s a catch to sun drying: humidity. Food dries best when temperatures are above 85º F and below 60% humidity. If you live in a desert, humidity isn’t a problem. But in most other places in North America it’s simply too moist to set food out under the sun. It will rot before it dries. In Los Angeles, due to the influence of the ocean, it’s slightly too humid most of the year for sun drying to work well.

But there’s an easy way to overcome humidity: convection, i.e. hot air rises. Most solar dehydrators take advantage of the passive movement of hot air to lower humidity enough to dry food. Here’s a couple of solar dehydrators that harness this simple principle to dry food without electricity:

Continue reading…

Sun Boxes: A Solar Powered Public Art Project

It’s not often that my unused music degree intersects with the topic of this blog, but I got an email from Craig Colorusso describing a neat, solar powered public art project that he’s touring the US with called Sun Boxes. From the description on his website:

Sun Boxes are an environment to enter and exit at will. It’s comprised of twenty speakers operating independently, each powered by the sun via solar panels. There is a different loop set to play a guitar note in each box continuously. These guitar notes collectively make a Bb chord. Because the loops are different in length, once the piece begins they continually overlap and the piece slowly evolves over time.

You can find out more about the project at www.sun-boxes.com. Make sure to listen to the recording of the boxes–I could listen for hours–the sound is at once hypnotic and deeply relaxing.

My Trip to Maker Faire


Getting ready for the earth oven workshop this weekend meant that I never got around to reporting on my trip to Maker Faire up in San Mateo on the 19th. I spoke in the low-tech “Homegrown” shed far away from the high powered tesla coil displays happening elsewhere. To add to the low tech/high tech irony, I was not able to use my PowerPoint and had to speak extemporaneously. This worked out for the better, as I was able to pull up a member of the audience to demonstrate her solar cooker–much more fun than showing pictures of solar cookers. And, after all, maybe it’s time we retire PowerPoint.

Some of the things I spotted at Maker Faire:

Long lines for the tiny house. I’ll review Lloyd Kahn’s awesome tiny house book later this week (he gave a talk just before me). Not sure what’s up with the white robe outfit in the foreground.

Also spotted: bamboo bikes!

Cornelia Hoskin, who curated the Homegrown Village part of Maker Faire, her husband and new bambino. Cornelia also runs homegrown.org.

Yes, there were paintings done by snails.

Solar popped popcorn.
A rep from Sweet Maria’s Coffee gave a great demo on all the ways you can roast your own coffee.

Expensive AK-47 toting garden gnomes.

And solar powered bikes. Not sure how this would work out on an LA street.

Someone in the Homegrown area was processing greywater in bulk containers planted with bamboo.

Overall I had a great time. It was a wee bit heavy on the robots and 3d printer gadgets but that’s to be expected. At least there were a few chickens present to balance out the proceedings. However, next year I’m coming with an overhead projector: