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:

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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:

Low Tech Solar Heating with a Thermosyphon Collector

Yet another great post from the folks at Build It Solar: a simple and low tech solar heating system called a thermosyphon collector mounted in the wall of a garage. It uses the same principle as the solar dehydrator we have on our garage roof–basically it’s just some clear plastic and a heat collector made out of black window screen. If your climate is cold and sunny (think Colorado) this would work nicely.

Read the post to see a review of its performance over the past nine years here.

Solar Garden Helper Thingy

From the always cool Build It Solar blog, a “garden helper machine” built by Randy, aka “PD-Riverman”.

I really Love gardening but I have a bad back and when it comes to staying bent over in the garden it gets rough. So I built this Helper Machine. I  call it My P-Machine. Planting/Picking/Pulling weeds/Putting around the garden machine. 

It’s powered by two 12 volt 80 watt solar panels that charge some golf cart batteries.

I feel like adding learning welding to my New Years resolution list!