Solar Power isn't Feasible!

Solar Power isn't Feasible!
This cartoon was on the cover of the book "SolarGas" by David Hoye. It echoes the Sharp Solar slogan "Last time I checked nobody owned the sun!"

Monday, November 26, 2007

Bicycle Parts and Vanity Mirrors

I just finished reading "Design for the Other 90%", a gift given to me and Sybille from Kenneth and Diane Miller to inspire us in our Solar CITIES work. It is appropriate to have read this book during the "Thanksgiving" holiday, since the celebration itself goes back to a time when the native Americans shared their tech-knowledges with the starving European refugees ("pioneers"). And it gives me a moment to thank Kenneth and Diane for thinking of us as "two caretakers" (as they wrote in their apt inscription) who could benefit from the sharing this book (and the exhibit at the Cooper-Hewitt National Design Museum) makes possible.

Perhaps the article that has the most immediate relevance to our work (trying against all odds to bring affordable solar technologies to the other 90% in Cairo) is the one on the "Solar Dish Kitchen" created by the BASIC Initiative Mexico Program of the University of Texas and the University of Washington back in 2004, and now used in both India and Mexico.

For one thing, the Solar Dish Kitchen was "designed for two informal poor urban settlements (squatter communities)" and that is the type of one of the two communities we have been working with in Cairo for the past few years. It's focus on cooking meals for children and helping mothers is closely related to our work on solar hot water systems -- theirs, like ours, are "retrofits" to existing buildings, and provide both solar cooking and solar hot water heating. While our systems do not generate temperatures sufficient for cooking, they do preheat water so that the fuel load getting it up to boiling is significantly reduced.

But we, of course, are building flat panel solar hot water systems, while their system makes use of solar thermal concentrating technology, and this is something we would desperately like to replicate.

We have tried, several times, to hand-build solar concentrators like the one depicted in the Solar Dish Kitchen. When I was on the board of directors of the Wadi Environmental Science Center back in 2004-2005, after visiting New Basaissa in the Sinai with my mentor professor Dr. Salah Arafa, and seeing what he had built there, I went hunting in Bab El Louk (near the AUC campus) for satellite dishes of various sizes. We covered them with vanity mirrors, set them up on their poles so they could be swivelled to face the sun at any time of day, and, by fastening a black metal plate with a serpentine copper tube welded to it, connected to a cold water hose and a faucet, demonstrated that we could get super hot water from the system (as well as do fun things like light wood on fire on a cold windy day -- the coolest demonstration was showing kids that a white piece of paper would hardly get hot, much less ignite, because it would reflect the sun's rays, but as soon as you drew an ink dot on the paper that part would absorb the heat and burst into flame).

I later built a similar system for demonstrations on the roof of the biology building of the American University in Cairo and, instead of covering it with vanity mirrors, reduced costs still further by simply gluing potato chips bags to the dish, with their shiny insides facing out.

We demonstrated that the chips bags work rather well -- water still gets up to 85 or 90 degrees (for some reason that last 10 degrees is a real pain to heat up -- something about water's amazing properties -- getting to the phase change point takes a whole lot more energy!), and you can still set wood on fire (it takes a little longer, but the way it gives off smoke within a few seconds is impressive). The huge cost savings, and the potential for creating an incentive to pick up and collect the ubiquitous but relatively value-less chips bags from the littered Cairo streets, made the energy loss worth it.

The real barrier to implementation was something far more insidious than the usually doubted ability of the dish to concentrate solar energy for useful domestic applications (Solar Dish technology is so proven, and has been for so long, even for industrial applications, that it is almost embarrassing to have to say it again! Here is a 1954 article on its "potential" for the "unbelievers"; click to enlarge):

We proved to the locals that it could have utility. The problem which plagues us is HOW TO TRACK THAT DAMN STAR! To the ancient Egyptian astronomers, the chief difference between stars and planets was that stars seem to stay fixed in the sky, while planets move around (in fact, "planet" comes from a word, also found in "plankton", meaning "wanderer"). The great Arab navigators used their astrolabes because they could "fix" their position using the relatively "fixed" stars. All you needed to know was the time of day or night, and from that you calculated where the star should be in its "fixed" path and you could use it to find where you were.

All fine and good for navigating ships. For solar applications though, the clocklike movement of the sun, steady as it is (and thus the foundation of solar clocks, a.k.a. sundials) frustrates all the attempts of do-it-yourselfers (including almost all of "the other 90%" in the world) from taking good advantage of the star power we call "sunshine".

Every five minutes the sun moves one degree. Every hour the solar dish thus needs to be moved 12 times to maintain the focal point on the surface you want to heat. During the 6 good hours of sun we get in Cairo (between 10 and 4) that means we have to move the dish 72 times to maintain its heat output. Regardless of how cheap time and labor may seem to outsiders, we have yet to find anybody who finds it worthwhile to keep moving the dish just to heat water for cooking or bathing. Even the women of the community, forced to slave away in front of open flames preparing the meal and bathwater for the whole family, are not enamored by the idea of sitting in the hot sun moving a dish every five minutes. The maintenance costs are too high.
This is one of the reasons the parabolic solar cookers have failed to take off (the other, as pointed out by Martin Fisher in the Design for the other 90% book is "In designing for the world's poor, there is too often a focus on developing things that "we" think "they" need. We design technologies that address a problem we have defined without understanding the true needs of the people we are trying to help. SOLAR COOKERS ARE A GOOD EXAMPLE. THERE ARE MANY CLEVER DESIGNS WHICH ALLOW USERS TO HARNESS THE POWER OF THE SUN TO PREPARE MEALS. THE IDEA IS THAT THESE COOKERS SAVE FORESTS FROM BEING BUT DOWN, SLOW GLOBAL WARMING, AND REDUCE THE TIME REQUIRED TO COLLECT FIREWOOD. THESE ARE LAUDABLE GOALS, BUT IN MOST PLACES, PPOOR FAMILIES PREPARE THEIR LARGEST MEALS IN THE EVENING, WHEN THE DAY'S WORK IS DONE. THEY PREFER TO COOK INSIDE SO THEIR NEIGHBORS CANNOT SEE WHAT THEY ARE COOKING, AND OFTEN RELY ON A COOKING FIRE FOR WARMTH, LIGHT, AND TO HELP REPEL MOSQUITOES." (p. 35)

(A parabolic solar cooker - we've tried to introduce them in Egypt, but the idea fails to take off, for reasons stated above...)

The answer, it would seem, would lie in having an inexpensive parabolic dish that easily and automatically tracks the sun, so little or no thought or labor must be invested in using it, and , most importantly, which stores the heat for use in the evening. It is for this reason that Solar CITIES considers solar heating systems a form of effective PRE-HEATING, and uses insulated plastic barrels to store 50 degree water from flat panel systems that require no turning. The fuel savings in heating the water to boiling in the evening are considerable. But we dream of an inexpensive automatic parabolic system that would heat the water in the tank to near boiling. Then the energy investment in the evening would be much much less, and it would begin to pay off for the people -- they could still cook and bathe in the evening, but the starting temperatures would be much much higher!

Searching for solutions, I visited the Deutsches Museum for Science and Technology in Munich for the third time yesterday, and revisited the reconstruction of Lavoisier's famous laboratory (Lavoisier was a major inspiration of mine when I began teaching science in the ghettoes of South Central L.A. in 1989 -- I read passages of his book "The Natural History of Candle" to my students, realizing, as is pointed out by Paul Polak in 'Design for the Other 90%' "Often the most effective way of optimizing affordability is by going back through the history which leads to the modern form of the technology."


This principle, the second of Paul Polak's guideline for designing effective products for the poor, lead me back to Lavoisier.

In the Munich science museum they had recreated Lavoisier's 1775 "Brennlinse" -- a solar "burning lens" system. Lavoisier had used it to heat lab flasks to 1500 degrees celsius (hot enough to melt copper) using solar energy. The system consisted of two huge glass lenses, one perhaps a meter in diameter, another a quarter or a meter or so away about half that size. The entire apparatus was mounted on a wooden wheeled cart with a turning table (like the "lazy susan" you find at some Chinese retaurants) and a small gear system to change the angle of the lenses. The toothed gears on both the rotational and angle changing parts of the machine made it clear that he had found a way to precisely move the lenses in accordance with the fixed and thus predictable movement of the sun.

(photo shows The Lavoisier Solar Furnace and laborator at the Deutsches Museum in Muenchen)

It was also clear from the design that some sketches I had made with AKTC architect for using the giant plastic fresnel lenses I had brought to Egypt would work (All praise to the internet as social transformer: I've just discovered that Mother Earth News has an article on how to build and use a solar furnace here!).

(Diagram from Mother Earth News)

What was also obvious, though, was that Lavoisier too had to move the system by hand. Standing in the detailed recreation of the inventors' 18th century lab, I was impressed by the system he had developed (it has even been made famous on mugs and T-shirts, bags and mousepads!), but despaired that alas, it still didn't afford me any idea how to eliminate the labor of the precise turning.

But Paul Polak's principle of "Moving Forward by Designing Backward" includes the additional guideline: "UPDATE THE OLD PACKAGE WITH CUTTING-EDGE MATERIAL":

"Revise outmoded designs with any new materials that may have become available, as long as affordability is not compromised."

Ted Stern, our good friend and colleague (the true to life "rocket scientist" featured in James Dean and Elisa Conklin's "Solar Circus" documentary) demonstrated at the solar conference in Egypt in 2004 that rather than using exotic and expensive photocell technology to track the sun (such as you find in the Pyrenees in the village of Odeillo in France) and drive the step motors, one could simply use a clock. He stated, "the sun moves in an orderly and predictable fashion, varying only in its angle throughout the year. The time of sunrise and sunset are likewise predictable. Therefore, all one needs to do is run the gears moving the solar tracking system with a simple clock."

The difficult thing, however, is that nobody has ever shown us HOW you would do that, and how you would build a simple inexpensive system for getting the damn dish to move. Like most of these great ideas, in principle it is deceptively easy and certainly intuitive. In practice however, it is the stumbling block, the achilles heal that defeats all our our attempts to implement home scale solar dish technology.

Yes, we have thought of using the satellite dish receiver movement arm (that little piston you can buy to track satellites for your TV channels) but it is too expensive to justify for the very poor, and requires (as far as we know, though we never tested it) buying the satellite receiver to run it (obviously there are ways to make the stupid thing move without buying the receiver, but nobody with that basic level of electronics experience has ever come forward to show us how!).

What Sergio Palleroni's "Informal Community Solar Kitchens" article in "Design for the Other 90%" does for us, however, is suggest a new alternative we hadn't thought of:
The flaw in the Cooper Hewitt book for people like us, who ARE designing for the othe 90%, is that it gives no detailed plans, so we have no idea HOW they implemented the solar dish using bicycle parts and vanity mirrors. But we are inspired, and can at least begin to look into the possibilities.

Perhaps there is somebody out there reading this who is an intimate friend to "bicycle parts", somebody who loves bicycles and dreams of ways to use his/her passion for bicycles to help third world development and never before considered that bicycle parts could furnish an answer to the dilemma of integrating solar thermal concentration technology into the lives of the urban poor.

If that person is out there, we would love to hear from you, and work with you on making the ancient site of "Heliopolis" a true "solar city".


Andy said...

"Perhaps there is somebody out there reading this who is an intimate friend to "bicycle parts. . ." Hmm. I happen to be both mildly enamored of both bicycle parts and integrating solar thermal concentration technology into the lives of the urban poor. You're looking for a cheap way to track the sun's movement throughout the day? I'm thinking something along the lines of using a bicycle chain, perhaps a small solar panel to charge a battery that'll run a gearbox. I'm meeting with a mechanical engineering professor on Friday morning at Brown' engineering lab--they have all sorts of goodies there. Let me bring up the question to him and see what he suggests.

Marcel said...

Let's talk!


T.H. Culhane said...

Hi Andy, Hi Marcel,
Thanks for your responses. I just got back from seeing Leonard DiCaprio's great film "The 11th hour: 5 minutes to Midnight" which features Stephen Hawking making his usual profound statements about our role in the biosphere and the cosmos and your brief comment "Let's Talk" reminded me of Hawking's marvelous "voice" looped into Pink Floyd's "The Division Bell" when he says, "For millions of years mankind lived just like the animals..
Then something happened which unleashed the power of our imagination...
We learned to talk...
"It doesn't have to be like this...
All we need to do is make sure we keep talking..."
(Since I live in Germany, here is the german for you:
"Über Millionen von Jahren lebte die Menschheit wie Tiere
Dann ist etwas geschehen, was die Macht unserer Phantasie freisetzte
Wir erlernten das Sprechen...
Es muß nicht so sein...
Alles was wir tun müssen, ist sicherzustellen, daß wir weiter miteinander reden"

So yes, let's talk!

Andy said...

hey T.H.,
Michele and I saw the DiCaprio film when it first came out in the U.S. I wrote a review of it that you can see on my site. I thought it was great too!

Marcel said...

Can we discuss via email? Please drop me a line...

I look forward to hearing from you.


Marcel said...

hi TH
i don't know how you are progressing 6 months down the track with the solar cooking issues, given your PhD and baby....:)

Wadi Environmental Sciences Centre tell me they are doing work with their students on solar cooking, and i was scrounging around for info on this myself and found the following link....what i couldn't find was a description of or solution to your problem of tracking the sun...however maybe the diagrams on this link will be inspiring.

a fellow philanthropist in cairo