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!"

Friday, November 30, 2007

The "Zeitgeist Conspiracy" and how it affects the use of solar energy

What's wrong with this picture?It astonishes us here at Solar CITIES how difficult it is to overcome inertia and lassitude when it comes to moving toward sustainability. We aren't pointing any fingers; We are astonished by ourselves. We also too often take what seems to be the "easy route" and cause long term problems for ourselves. So we need a new way to think about problem solving, or at least a way to make "making an extra effort" somehow seem fun and "worth it".

We'll come back to what's wrong with the picture above in a moment. First, a short diatribe on what we call "The Zeitgeist Conspiracy"

When we went to see Leonard DiCaprio's milestone film "The 11th Hour: 5 minutes to midnight" in Munich (Southern Germany) last week and discovered it was only playing at one theater and only at 10 in the morning, and then discovered, when we tried to take our family members to it this week in Essen (Northern Germany) that it wasn't playing at all, forcing us to drive all the way to Dusseldorf where, again, it is only in one theatre and only at odd hours, we almost gave up. You should have heard the arguments against "wasting our time going all the way there (45 minutes away), wasting gas driving there... oh the cost and inconvenience of it all..." -- yet we DID happily travel all the way there last year to see Tom Cruise in Stephen Spielberg's "War of the Worlds", making a fun "trip day" of it, and that movie has little redeeming to say for it except for Morgan Freeman's delightful narration, reminding us that even the humblest and most maligned of God's creation, large and small, have an important role in the health of the biosphere. But I'm sure that point was lost on most movie goers.

"The 11th hour", on the other hand, is of enormous import, much like Al Gore's brilliant "An Inconvenient Truth", and DiCaprio does a great job of pointing out not only the problems and the urgency of stopping climate change in this 11th hour, but of calling our attention to the marvelous ideas and technologies out there that can be immediately implemented, even at this late hour, to save the day. Much as the simple microorganisms save the day in The War of the Worlds, during this war to save the world, the movie tells us, everything from fungi to bacteria to the rest of us "little people" among the 6.5 billion humans in the world can work with Gaia's ecosystem to bring her back to health. It is a feel good movie when all is said and done.

So why the reluctance to make the effort to see it? And what does that have to do with what's wrong with the picture shown above?

It is something we call "The Zeitgeist Conspiracy". As far as conspiracy theories go, ours is pretty mild and sensible and shies away from pointing the finger at anyone (wouldn't want people who do bad things to think of themselves as "bad people" now would we? Wouldn't be very Christian-like, and we are struggling every day to "love our enemies" and "love our neighbors as ourselves" so that we can cut this Gordian knot of resistance to positive change.)

So what is the Zeitgeist Conspiracy? We define it as a group of people all breathing and co-tainting the same bad air together (in-spiring, re-spiring, CON-spiring) trapped in a fairly rigid if semipermeable bubble called "the spirit of our times" (in German "Zeitgeist"). When you con-spire that spirit, you become part of the con-spirit, see? And thus, you are part of the Zeitgeist "con-spir-acy". Is that too much of a stretch? Too much linguistic leger-de-main?

Let me try to put it differently, drawing on the work of science writer Phillip Ball in his masterful opus "Critical Mass": like typical herd animals, humans conspire to maintain the status quo until enough of them change direction, and a new wind blows. Then they jump aboard the bandwagon. And we haven't reached that critical mass yet, so most of us are stuck. We look around us and say, "if I make that much effort to see DiCaprio's movie (which is not in the interests of the special interests that conspire to keep it from effective mass distribution), will I appear like a hero to my family and friends, or like a granola eating, behrenstock sandal wearing, earthy crunchy fool? Is it sexy enough yet to be the guy who went to all that trouble to be part of a cause that our majority leaders still haven't sanctioned? Is this how I want to, as Irving Goffman put it, make my "presentation of self in every day life?" Is this , as Eric Bern would have put it in "Games People Play" and "What do you Say After you Say Hello", the "T-shirt you would like to wear that tells people who you are?"

For most of us the answer is sadly "no". We are risk averse characters and we mostly follow the pack unless we feel we can get real social recognition for our extra efforts. Until then, unless the few percent of people who have the power to make certain things relatively "effortless" make the transaction costs of doing something new or different painless, only the "early adopters" or "lighthouse customers" (as Everett M. Rogers would call them in his "diffusion of innovations theory") will "cross the chasm" (as Geoffrey Moore would call it in his model). The rest of us will hold back until... until 5... 4... 3... 2... 1 minute to midnight? Until "after midnight", when we "let it all hang down"?

To paraphrase the Eric Clapton song, baby, it ain't gonna be "all peaches and cream" after midnight. No sir. We're going to have to "stimulate some action" NOW, at 5 minutes to midnight and counting, during the 11th hour; Ain't gonna wait for "The Midnight Hour", cause that's when the whole world comes tumbling down. Uh-huh. That's whataymsayn! Word.

But how do we get out of being part of this horrible, time lagging, procrastinating Zeitgeist conspiracy? And what does it have to do with the picture above?

Let's answer the second answer first ("and the last shall be first and the first shall be last...")

The picture above is remarkable because it contains misinformation that radically affects the performance of thermosiphoning solar hot water systems, and it seems nobody thought to test it. The picture is printed in a booklet that the wonderful Hans Seidel Stiftung (a German foundation) publishes and makes available to help people in Egypt learn how to make solar hot water systems. The fact that they have gone to the trouble of not only printing and distributing these great informational booklets but of supporting workshops in the Suez area to train locals how to create home-made domestic solar hot water systems is more than laudable. The Hans Seidel Foundation is one of the best organizations out there, working on everything from solar technology implementation to biogas production from waste.

We applaud everything the Hans Seidel Stiftung does, and their booklets have helped us convince all sorts of stakeholders in the local community to work with us on our Solar CITIES project.

What is a shame (and we have witnessed it all over Egypt with other foundations projects as well, including our own) is that they are all subject to the curse of what UCLA Professor Susanna Hecht used to call "RECEIVED WISDOM" in her development classes.

Instead of relentlessly beta testing ideas locally, and involving local wisdom and experience (what Dr. Hecht called "metis", from the Greek), we almost always apply "techne" (codified "one size fits all" knowledge) and that techne all too often reflects certain historical contingencies and market compromises. It has become "commodified".

There is often, of course, a good reason for this: testing and modifying things locally takes time and energy and money and patience and cultural understanding. It is reasonable to expect that people will try to avoid "reinventing the wheel" if they can, but what is the great shame that reflects the "zeitgeist conspiracy" is how many times we have seen a failing to rethink things that have to do with local solutions for decentralized energy and food production.

Whereas people will obsess with endlessly checking and redesigning entertainment media, for example, incessantly improving every new iteration of a computer program and inviting a host of world-wide "beta testers" to enthusiastically check for bugs and report problems, this same passion for redesign is almost never occurring with renewable energy systems, electric cars, or other examples of "appropriate technology".

How many times have you agreed to "send a report to Microsoft" to help them with the computer errors that crashed the computer program you were working on? You have become part of an army of unpaid testers -- worse, you are paying for the privilege of spending your time and labor helping to improve THEIR products. But at the same time, you would probably consider it absurd to spend hours of your day or night trying to help us all improve the quality of information and product relating to things that, if we put our collective intelligence to work on them, could stop the scourge of global warming and biodiversity loss.

The diagram in the Hans Seidel Stiftung book is a case in point. Egyptians had been telling me for the past several years that "solar energy systems are great in the summer, but they don't work in the winter." My experience with solar hot water in Germany and the U.S. contradicted this complaint, so I didn't take it seriously. I chalked it up to "the ignorance of the locals". And, optimistically, I went ahead and built several solar hot water systems out of local materials with the locals, according to plans like the ones reproduced in the booklet. Of course the systems worked, and to prove a point, I gathered a crowd during the winter and turned on the faucet and showed that, yes, they produce hot water in the winter months.

Case closed?

Hardly. In our western arrogance we forget to consider the usefulness of our technology to fit into the daily consumption patterns of the local people. Sure, we demonstrated that solar hot water systems designed as in the diagram can deliver hot water in the winter. But we never took the time to measure exactly how much or to make it a priority to redesign the system to suit the real on the ground conditions. We relied on received wisdom.

It wasn't until my wife and I actually moved into the slums of Darb El Ahmar into a building recently renovated by the AKTC and built one of our "hand made solar hot water systems" on the roof of our apartment and decided to stay during the cold winter that we learned, by living as a local, what the problems with the design were.

In short, the systems depicted in the diagram, which can easily heat 200 liters of water using a two panel setup (each panel being 180 x 80 cm) during the summer, only heats about 25 liters during some winter days. That was fine for our demonstrations, because we simply turned on the faucet and let people stick their hands in the piping hot water that gathers at the top of the tank (see the diagram) and didn't use more than 25 liters. But when you are actually using it to bathe every day, you quickly run out of hot water.

The locals said, "you see, told you so, solar hot water doesn't work in the winter." And all we could do was hem and haw and talk about reduced consumption patterns in the winter and "yeah maybe solar is just a preheater in the winter... blah blah blah." Internet searches didn't help -- most diagrams show the cold water outlet at the bottom of the tank and hot water inlet at the top and suppose that the water will circulate (see the circular arrows?) until the whole tank is hot. But our field experience showed us that that isn't really going on. Hot water does a terrible job of heating by convection, and most of these diagrams must be based on the use of a circulation pump, because in the winter with the shorter hours of thermosiphoning, circulation doesn't see to be happening at all, particularly not in the vertical tanks we are forced to use for cost reasons in developing countries (note that commercial suppliers of thermosiphoning SHW systems use horizontal tanks and boast about the improved circulation/mixing capacity). So we felt stuck, demonstrating to the locals that in a vertical tank there is a dramatic thermocline in the winter -- water at 50 degrees C at the top of the tank, water at 25 degrees less than 15 cm underneath it, with a sharp difference in the layers that you can feel when you stick your hand in the tank (we use open tanks for demonstrations).
Use up the 25 liters or so of hot water and then you have to grin and bear the 175 or so liters of cold water in the winter. Or so we thought.

Then we remembered our trip to Palestine.

The beauty of traveling around the world to areas where refugees are trying to solve problems without much help and in the face of great adversity is that you begin to pick up bits and pieces of effective local knowledge -- what Dr. Susanna Hecht called "metis" - that can radically affect the globalized "techne" and thus improve its local application.

We had learned from the Palestinians that in households that have no constant water supply one should put a cold water feed-in tank to maintain pressure. We learned this by walking down one of the streets that separates West and East Jerusalem and noticing that you could tell which houses were Israeli and which were Palestinian by looking at the solar collectors on the roofs: Israeli houses tend to have one tank systems (with horizontal tanks) while Palestinian houses tend to have two tank systems (with vertical tanks). Palestinian families whose roofs I climbed onto told me that they need two tanks because they have unreliable water pressure, and often the water is cut. Thus they have a cold water tank feeding into the hot water storage tank connected to the solar hot water system.

We had learned to adopt this system in Darb El Ahmar and Manshiyat Nasser because water pressure is nil to nonexistent during much of the week and water is often cut outright. But it wasn't until we re-examined close up photographs we took of the roofs of Palestinian homes that we realized they had also solved our problem with the winter-time low performance of the vertical tank solar hot water system. We originally thought it was just poor design (weren't they following the diagrams we send them from the West? Was it ignorance?) but came to realize that it was the hard won experience of trial and error that led the Palestinians to place the hot water inlet NEAR THE BOTTOM OF THE TANK, JUST ABOVE THE COLD WATER OUTLET. Our prejudices (not believing the locals could know better than the published diagrams) blinded us from taking the risk that would have solved our problem a long time ago.
But once we started living like the locals, in the slums, and dealt with the problem of taking a hot shower every day in the winter, we suddenly realized we would have to experiment too. Fortunately, we had the Palestinian model to go by, and it was simply a matter of giving it a try.

We went from this:

To this:

It cost time and money, yes, because it meant we had to build another system for comparison with the standard system. But once it was built (on Solar CITIES field coordinator Hanna Fathy's house in the Zabaleen area) its performance exceeded our expectations: 200 liters of hot water on a variably cloudy day that only produced about 20 liters in the system with the hot water inlet placed at the top as in the diagram!

We also made modifications that no system we have ever seen in the world has: we listened to the advice of Plastics recycler Walid Sabry, whose mother and sisters sit in piles of medical waste all day, often pulling needles from used syringes and separating bloody bandages from medical bottles, risking hepatitis infections. Walid had asked, sensibly "why can't we use plastic barrels with loose fitting tops for both the hot and cold water barrels?". When "experts" from development agencies and universities told us the hot water would melt the barrels, we decide to honor Walid's skepticism and that of local Beduoin friends who regularly boil water in used PET plastic bottles over an open flame (because many plastics melting temp is over 140 degrees, and won't melt as long as the container is filled with water -- water can't rise above 100 degrees until all has turned to vapor). In fact, the plastic barrels are great for hot water storage in a solar system (only in gas and electric systems does the heating element get hot enough to melt the plastic). And a whole lot cheaper.

As for the loosly fitting top issue: I came up with my own innovations: I figured out how to use the Magdy Zahran barrel float valve in both tanks, setting them up like toilet bowls so that they automatically stop filling when they are full, and solved that problem. Now that Magdy Zahran, Egypt's premier plumbing inventor, and I are good friends I realize I should have been talking to local inventors all the time, instead of trying so hard to find "foreign experts" to help solve these problems.

A combination of local metis and globalized techne is one of the solutions to our global warming dilemma, and one must be respectful and humble and willing to attempt some real "bricolage" trying to fit the two together to fit the circumstances. That much is sure.

But now, how do we stop participating in the Zeitgeist Conspiracy? Not everybody is an "early adopter" much less an inventor or innovator. Not many people can afford to spend the time, money or energy painstakingly trying to improve things in the real world. It would take a lot of incentive, for example to get most of us to get up off our butts and start tinkering with our automobiles to make them run on alcohol or biogas or electricity (though it really isn't hard to do!) much less go to a third world country and live in the slums and try to design a better heating system.

So how can the majority of us defeat the Zeitgeist conspiracy?

My answer is to start taking the public's willingess to beta test software seriously. Now that computer game engines for video games are open source or cheaply available (such as the Steam Source SDK physics engines for Half Life 2 or the SDK for Elder Scrolls Oblivion) I suggest we follow the lead of the Digital Urban group and start modeling real time physics and engineering problems on our computers in a realistic and fun simulation environment of real ghettoes and rural areas. It doesn't have to be that tough -- already there are huge numbers of gaming fans who enthusiastically spend long hours "modding" their favorite games. Tutorials are readily available. And even Popular Science this month has an article called "The Hard Science of Video Games", explaining how computer game software development kits (SDK's) are among the most important tools for data visualization and experimentation on the market.

Since computer models can now make realistic predictions of the effects of temperature and density and mass and volume on fluids and gases and can use them to model the effects of things like climate change, why not create virtual Darb El Ahmars and Manshiyat Nassers, literally create Digital Urban Slums, replete with rats and open sewers and inadequate plumbing. Why not do it as an Alternate Reality game, and let players build solar hot water systems and other industrial ecology systems on the roofs (as we are trying to do at Solar CITIES) and try out various designs and "play" through them and see which work and which don't? Make it part of the ARG gaming experience, and then report back to those of us in the field who are responsible for building the real things?

What is wrong with reinventing the wheel, or baking a better cake or building a better mousetrap? And now that we have the internet connecting all our virtual and real life experiments and each other, can't we all breath a better air together -- a different sort of Con-Spiracy, in which we connect to form a new "Spirit of the Time"? Now that would be a positive sort of Zeitgeist Conspiracy...

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".

Friday, November 23, 2007

Polypropylene: A revolution for the urban poor and their home-made solar hot water systems

Time it was (and what a time it was) when I had to learn to cut steel pipe. Thread steel pipe. Carry steel pipe. That was back in 2005 when Sybille and I moved to "Beverly Hills, Egypt", the new desert development out by 6th of October City, and into an unfurnished apartment on the bottom floor of a four story building. That was back when we installed our first solar hot water system, built while we videotaped at the Wadi Foods factory out in Noubariya way up near Alexandria. The plumbers, of course, did everything backward, never having been trained in any kind of thermodynamics theory (and thus apparently unaware that hot water, like the hot air in Montgolfier's baloons, RISES).
When, come winter time, the expectations of our skeptical neighbors were met ("you see, solar hot water systems don't work in the winter time!") I decided to take matters into my own hands and replumb the damn system the right way -- hot water from the panels into the top of the tank, cold water to the panels from the bottom of the tank, snaking around to the OTHER SIDE of the two panels, opposite where the hot water came out, so as to get a good cross flow for thermosiphoning.
But the pipes were steel, and they were heavy, and putting in new one's meant hauling new pipe home and buying special pipe cutting and threading tools. It was a pain in the butt.
When we began building our own home-made solar hot water systems, I resolved that I would use plastic pipe. Cheaper, light weight, easy to cut and glue.
I built our first hand-made solar system on the roof of building 72 in Darb El Ahmar, and our second on the Zabaleen recycling school in Manshiyat Nasser, and learned to use a PVC cutter (piece of cake) and how to glue pipe with toxic, foul smelling, skin fouling PVC glue -- a sure recipe for future cancer risk. Still, it was easier than steel pipe.
Unfortunately, the poor quality PVC that I could afford in Cairo was prone to cracking, and that meant embarrassing leaks that undermine confidence in the solar hot water systems we were trying to convince people were an answer to, not a source of, their problems.
At the time, when I went shopping in the Sabteyya market place, a "new German technology" was making its way to the larger shops: green polypropylene pipe. In 2006 it was still fairly expensive, about 9 LE per meter (the same as steel pipe and 3 pounds more than PVC) , and I was told by the various plumbers I was training with it was very difficult to use because it needed to be "welded" using special equipment. You couldn't just buy the pipe and thread it or glue it together (I have since learned that you can simply thread it the way you thread steel pipe, and use it in the same way, but that is another story involving poor man's compromises!)

This year, something miraculous happened (though quite predictable given the laws of supply and demand and factor substitution and comparative advantage and all those other great lessons from Economics 101) . First Turkey and then Egypt itself began manufacturing Polypropylene pipes and plumbing supplies. I was told they imported the powder from Germany, but could now take advantage of the lower labor and operating costs in the developing world. When I was building our third hand-made solar hot water system, to put on the roof of one of the two Solar CITIES' new coordinators, Hanna Fathy, in the Zabaleen neighborhood, I checked on the price of Polypropylene and found it had dropped to a mere 3.25 LE per meter. Suddenly it was cheaper than either steel or PVC, and was now known for its durability and ease of use.

Taking the plunge, I decided to overcome my "I can't do this stuff" attitude and buy the welding machine. It turned out that contrary to what the plumbers had been telling me ("The only welding machines are from Germany and they are very expensive, between 1500 and 2000 LE") Turkish manufacturers had brought the price down to a mere 300 LE! And it turned out the welder was small, lightweight and extremely easy to use. (This year we bought a Chinese version even smaller and more light weight for a mere 150 LE!)

When we began building my latest invention, the "Dr. Flaschenstein's bottle-brick solar collector" from recycled bottles, on the roof of AUC's science building (funded by a generous 500 LE contribution from Dr. Moshira Hassan, a long time supporter of Solar CITIES, following the tradition of Dr. Jeff Miller, who had started it all with his 10,000 LE investment before retiring) I started conducting plumbers training workshops, and introducing our Zabaleen and Darb El Ahmar colleagues to just how easy it was to weld polypropylene pipe.

Samih, one of the plumbers, was so delighted he volunteered to run polypropylene pipe from the system we had built on the Zabaleen school all the way to the shanty home of Walid Sabry, just so he could practice his new skill (Walid's family recycles medical waste and are in danger of hepatitis (we had given them cold water the previous year, piped in from PVC, and, with donations from generous visitors such as Moshira's student Andrew, had actually helped them build a proper bathroom). Samih, who know has offered to volunteer his services every Sunday as his way of providing church service to his community, said, "the problem with many great technologies that can make our lives so much easier is simply that people don't know about them. And if they hear about them, they think they must be difficult or expensive or hard to implement, otherwise why wouldn't they already be in use?"

I reflected on my own hesitancy to jump into using polypropylene, and how long it took me to step up to the plate and buy some and buy the welding machine and start experimenting.

Now, what used to take a couple of days, putting together a solar hot water system and running pipe to the house, now merely takes a couple of hours. Repair and replacement jobs only take minutes. There are no toxic fumes, there is no mess, it is easy to cut, it doesn't leak or break, and it is so lightweight that I have carried entire plumbing kits for a whole building -- up to 40 meters of pipe, rolled up (!) on my shoulders from the marketplace in Fagala street to the Muqattam hills (an hours walk).

We no longer fear making mistakes and having to re-plumb -- we can experiment to our heart's content, knowing that if one configuration doesn't work, we can quickly try another.

Because of this we have recently been able to prove that the diagrams for solar hot water thermosiphon systems are all wrong -- they work in the summer, sure, because things get so hot the entire tank fills with hot water. But in the winter, performance is poor when you put the solar hot water inlet in the very top of the tank (particularly when using vertical tanks such as we do). The best placement is the one our Palestinian friends showed us when I clambered up onto roofs in East Jerusalem, Ramallah and the West Bank -- you place the hot water inlet only slightly above the cold water outlet. We would have never learned that if we had stuck with conventional wisdom and if we hadn't been encouraged to experiment and change things based on how easy and cheap polypropylene makes things.

Finally, Hanna and I proved that you can use recycled polypropylene found in the garbage over and over. A neighbor of his sells discarded poly for 4 LE per KILO, because once it has been welded there is little sense in using it again ( a virgin poly pipe is 3 LE per meter, and most recycled lengths are shorter than 2 meters, and the joiners and elbows needed to extend the recycled pipe cost between 1 and 4 LE each, so nobody wants recycled pipe that they have to weld together with expensive joiners.) But Hanna and I demonstrated that if we take the discarded joiners and T's and elbows to the iron worker around the corner, who has a standing drill press, we can drill out the poly joiners with a 19 mm drill bit, and they reweld like new! We also showed that we can weld 1/2" pipe to 3/4" pipe and skip using joiners altogether.

Polypropylene is going to create a revolution in sustainable development once local people learn how easy it makes the creation of do-it-yourself solar hot water systems!

Designing a Heat Exchanger for the other 90%

Our family friends, Kenneth, Diane and young Andrew Carnegie Miller (scions of the industrialist/philanthropist Andrew Carnegie) graciously sent Sybille and me the book "Design for the Other 90%", with the inscription "For two caretakers, as you are, this might inspire and inform your work."

It contains a foreward by Barbara J. Bloemink and articles such as "World Designs to End Poverty" (Cynthia E. Smith), "Design for the other Ninety Percent" (Dr. Paul R. Polak), "Fuel from the Fields" (Amy B. Smith), "Design to Kickstart Incomes" (Martin J. Fisher), "One Laptop per Child" (Interview with Nicholas Negroponte and Yves Behar), "Reliable Renewable Rural Energy" (H. Harish Hande, Ph.D.), "Rolling Water" (Pieter Hendrikse), "Informal Community Solar Kitchens" (Sergio Palleroni), "Life Line" (Cheryl Heller), "Leapfrog, Design Strategies for Global Innovation" (Sheila Kennedy), "Katrina Furniture Project" (Sergio Palleroni), "Lessons from the Marginalized: A Manifesto for a Truly Public Architecture" (John Peterson), "Hearing for All" (Modesta Nyirenda-Zabula), and "Pot-in-Pot Cooler" (Mohammed Bah-Abba).

The book is as inspirational as it is uplifting, making the reader cry out "brilliant -- wish I had thought of that" with every page turn.

Now the rub: Being such a reader, long influenced by other such great books (in particular "Eco-Pioneers: Practical Visionaries Solving Today's Environmental Problems", Buckminster Fuller's "Critical Path" and "Design Outlaws on the Ecological Frontier" among others) I have long since graduated from "wish I had thought of that" to "how do I implement the new designs I AM thinking of?"

They say that necessity is the mother of invention, and I have thus deliberately gotten used to placing myself in places and circumstances where deprivation would force me to think of ways to improve my (often self-imposed) "poverty condition" (and that of those around me), so the design ideas that are scrawled in my notebooks are not few in number. What are very few in number are my successes in translating those ideas into practical realities.

Jeffrey L. Pressman & Aaron Wildavsky wrote a widely recommended book in the planning literature called "Implementation: How Great Expectations in Washington are Dashed in Oakland; Or, Why It's Amazing that Federal Programs Work at All" and its lessons were not lost on urban planning students like me who chose first to spend a decade in the ghettoes of Los Angeles and chase that bitter drink with another decade out into the field in "developing countries" such as Indonesia, Guatemala and Egypt. Implementation is the bear, whether it is making real our designs in policy or technology.

Our latest project at Solar CITIES is an example of how challenging implementation can be on the ground when you come up with a "design for the other 90%". First of all, you must realize that very few in that 90% will be able to do much to help you outright, even when the innovation you are considering is ultimately "for their benefit". People are generally risk-averse, and the poor have learned the bitter lesson that it is safer to stick with "tradition", even when it costs more in the long run in terms of discomfort, and labor and money lost. So when you are trying out your new idea in the field, don't expect it to win converts and supporters for a long while.

The case in point here: a do-it-yourself stove top heat exchanger for the other 90% in our Cairo survey area who don't have access to insolated roof space (i.e. their roofs don't get adequate sunshine, or they aren't allowed to modify their roof in any way, or the roof can't support any weight).

In conducting our survey of the community's of Darb El Ahmar (Medieval Cairo slum area) and Muqattam/Manshiyat Nasser (informal community built by the Zabaleen garbage recyclers) we have learned that many homes not only have no solar access, so we cannot provide them with Solar CITIES hand-made solar hot water collectors, as a promised outcome of our US AID small infrastructure grant, but the dire condition of the houses (typical for "incremental housing" situations) prohibits the families from making use of standard gas and electric hot water appliances, even if and when they can afford such consumer goods.

When we actually got into the houses to see HOW people were heating their bath water, we found that most were heating 10 to 15 liter cans of water on the stove (when they had a stove) or on a small gas burner on the ground.

Water heating, the survey revealed, is done by one of the women in the household (a mother or elder daughter) and takes approximately 30 minutes per person. Thus water heating alone can take a woman with 6 children (an average family size here) up to 3 hours of her day.

Clearly something must be done to lighten this burden, particularly if gender equity and societal transformation through education are considered important and realistic goals!

Our answer to the problem: designing a stove-top heat exchanger for the other 90% who must rely on gas burners for their bathing water.

The principle is simple and is derived from the standard gas heating appliance found in some of the homes where hot and cold water plumbing infrastructure has been provided: in a standard on-demand gas heater (the kind sold in Cairo) a copper tube snakes around a metal heat absorbing plate that surrounds several flame pipes. You ignite the flame pipes and the roaring fire quickly heats up the absorber plate. When you turn on the water, it flows through the copper tube and heats up. The output is instant hot water that lasts as long as the flame is on.

There is no storage tank, and the system is very efficient. It suffers, however from a couple of serious problems, even for people who can afford its modest (~ 500 LE, or $90) price tag (roughly a months salary for most people). One is that the diaphragm that allows the gas to flow to start the heating relies on adequate water pressure to operate. In our area, the water is frequently cut, and when it comes on, even in homes that have their own water pump, the water pressure can be very inconsistent. When the water is cut, heavy salts and other minerals in the water, which is of bad quality, crystalize and perforate the rubber diaphragm, rendering the appliance inoperable. While it is a simple matter to repair the diaphragm (I did it myself three times over the course of the year we lived in Maadi using a gas heater) and it only costs a few pounds (about 50 cents) if you know where to buy a replacement, most people DON'T know how to take apart and repair the heater and hiring a plumber (which costs an average of 60 pounds for the day, and who may charge at least 20 pounds for this procedure) is often out of the question for people at this level of poverty. Thus we have seen many homes with unused gas heaters who have gone back to boiling water on the stove.

We have witnessed the same thing with regards to electric hot water heaters: families will go to great expense to install them (necessitating finishing a bathroom with hot and cold water pipes and tiles -- not a trivial expense) and will use them for a couple of years until a combination of calcification and overheating when the water cuts out causes the heating element to burn out. At this point people will abandon using the heater and go back to using the stove, not knowing that a new electric heating element can be purchased for as little as 35 LE (7 dollars). The trick in many heaters, of course, is knowing how to install the new element. Most people simply consider the appliance broken and either throw it out or leave it sitting unplugged.

We have also found families who have unplugged their electric heaters and gone back to heating on the stove not because the electric heater didn't work, but because the electric prices proved prohibitive. It is "cheaper" to let the women in the family prepare the water in the "traditional way", and, as one respondent put it "I prefer to have my sister boil the water for my bath -- that way it is ready for me when I come to bathe; with my electric heater I not only have the cost to deal with, but it takes a half an hour to heat up, since I can't afford to leave it plugged in all the time. That means I have to think to switch it on and then wait. I would rather my sister simply calls me when it is time to bathe -- that way she can think about the heating."

Regardless of the reasons, a significant number of the households we have surveyed are forced to use gas stove heating for their hot water, and we cannot help them with solar hot water technology. So what to do?

The design of a stove top heat exchanger seemed most logical. Rather than having the mother or sister sit for hours tending to a pot of boiling water on an open flame, carrying the heavy and dangerous hot water from kitchen to bath each time it is ready (and risking scalding themselves or their family; third degree burns from bathing account for around 30 deaths and 300 hospitalizations a year according to Ain Shams Universities study in "Burns" Magazine), we proposed a copper heating coil in a cooking pot attached to a small 30 liter elevated cold water tank (basically a bucket with an output at the bottom) by a hose on one end and to a hose with a faucet on the other, attached to a hot water bucket.

The idea is that rather than placing the cooking pot on the stove and waiting for all the water in it to heat up, then emptying it each time, one could simply put the heat exchanger pot on the stove, heat it up in five minutes, then continuously run cold water through it (as in the "on-demand" gas heating appliance), running the hot water that results into the bucket at a safe bathing temperature (around 40 degrees) for transfer to the bathroom (or one could extend the hot water hose all the way to the bathroom itself).

Sounds simple.

The devil, of course, is in the details.

And here are the details from the first experiment here in Essen, Germany, where we are spending the Thanksgiving break:

Materials: (purchased from Bauhaus at Langmarckstr. 2)
81 Euros.

7 meters of copper pipe (roll, 12 mm x 1mm), sold at discount 5 meter price (3.95 per meter): 19.75
2 brass winkel @ 2.48 ea:
Rohrnippel Verzinkt:
Teflonband 12x0.1mm:
2 Flexible Schlauch, 1/2" @12.26 ea:
Kugelauslaufhahn M.
Getraenkefass 30 L

Basically, the faucet and on-off valve, and the two plumbers hoses, were the most expensive parts of the system. Plumbing parts always are. Our experience is that the plumbing supplies drives the costs of experimenting with new designs to prohibitive levels and discourages people from being innovative. Imagine, a small valve costing 9.25 euro!


We started by going to the Zoomarkt pet store and buying fine sand (1 Euro for a 2kg packet in the bird section) which we pouredwith a funnel into the copper tube after unravelling it to its full 7 meter length. Once it was filled with sand, we tightly coiled the copper tube, fitting it inside a cooking pot with a 25 cm diameter so that as much as possible was on the bottom of the pot and the rest spiralled up the sides. Then we removed the coil from the pot and took it outside and dumped the sand out. We then replaced the coil in the pot.

I connected the outlet of the 30 L plastic tank with a 3/4" to 1/2" nipple to the plumbers hose and connected that to the valve. to this I connected the brass winkel which I placed on one end of the copper tube sticking out of the pot.

On the other end of the copper coil, also sticking out of the pot, I placed the other brass winkel (angle or corner) to which was connected the other plumbers hose. On the other end of that was the faucet. This was placed over a 10 liter plastic bucket.

We placed the 30 liter plastic tank (sold here for beer making) on top of another, inverted, bucket next to the stove so that its outlet was above the pot with the copper coil. After experimenting with simply heating the pot with the coil inside, filled with water, and achieving lukewarm results, we finally filled both the coil and the pot with water, and let the entire pot heat up to 40 degrees reasoning that the best way to transfer heat to the entire coil was through outside water as a medium. The water in the pot would theoretically stabilize the temperature inside the coil which otherwise would simply radiate any heat it gained from the metal of the pot out into the air.

A log of the experiment is as follows:

9:17 PM, November 21, 2007:
Begin heating pot with copper coil on small electric stove burner. Pot contains 2 cms of water to cover the bottom coils. Water in is at 13 degrees C.
After 25 minutes the water in the pot has reached 93 degrees.
I open the faucet and let water flow to the ground bucket. It starts coming out at 84 degrees, but the temperature drops quickly as cold water from the tank flows through the coil. Within 3 minutes of flow the water coming out of the exchanger is at 23 degrees. By 4 minutes it is 22 degrees.

After 8 minutes the 10 liter bucket is full and I switch off faucet. The mixed temperature of the 10 liters in the bucket is 30 degrees.

At 9:50 we decide to switch to the larger electric stove top burner, figuring that it has higher heat output.

We open the faucet and start filling another 10 liter bucket. Inlet temperature of water into the coil is still 13 C.

9:52 The temperature of the water leaving the coil is now 28 C.
9:54 Brigitte suggests I fill the whole pot with the lukewarm water in the first bucket, now at 29 C, to see if that helps transfer heat. I do so.

Outlet temperature drops to 26 C and stabilizes there.

9:56 I close the faucet to let the pot heat up.
10:00 The water is 37 C in the pot
10:02 Water is 40 C in the pot
10:03 Water is 45 C in the pot
10:05 Water has reached 50 C in the pot START EXPERIMENT ANEW

10:07 Water outlet to bucket starts flowing at 53 C and quickly drops to 40 C.
10:08 Outlet 36 C
10:09 Outlet 34 C
10:14 29 C
The 10 liter bucket is full, and after mixing, is at 35 C

10:15 New bucket, Water in pot is now at 35-36 C, water inlet at 13 C, outlet at 26 C
10:21 full bucket, 10 liters mixed at 28 C

10:22 New bucket. Outlet starts at 30 C, drops to 26 C in 30 seconds, bounces up to 27 C.
10: 23 outlet temperature goes up to 29 C!
10:25 outlet temp 32 C
10:26 outlet temp 31 C

10:35 New bucket. Pot temperature is 33-34 C; inlet temp is 13 C, outlet starts at 29 C.
10:36 outlet temp 27-28 C
10:37 outlet temp 29 C
10:38 outlet temp 31 C
10:41, I restrict the flow rate and outlet temp naturally rises, to 35 C.
10:48 outlet temp 31 C, but of course it is taking longer to fill bucket.

10:49 New bucket. Outlet temp 36 C; I return to orignal flow rate by opening the faucet.
10:50 31 C
10:51 I decide to pour the 10 liters of 30 C water I collected into the remaining 20 liters of cold water (13 C) in the tank -- previously I had been refilling from the faucet at 13 C, but this was wasting water, as I was pouring the outlet water buckets each time into the garden. One thing to be remembered in implementation of designs into reality is that you are dealing with real, not theoretical, masses, volumes and materials. Water is expensive.
10:51 continued: The mix gives me a new input temperature -- water in tank is now 18 C. Temp at outlet now 32 C.
10:55 outlet temp 33 C -- a difference of ~ 13 degrees from input temp of 18 C, consistent with what we observed when input temp was 13 C and we were getting output temp of ~ 26C. It may be that the thermal gain from this electric stove burner with this system is at best 13 degrees over input at this flow rate.
11:00 outlet temp has climbed to 38 C, perhaps because entire pot is hotter...

11:01 New bucket. I pour the previous bucket (which also averaged 30 C) into the tank (which was at 18 C) and make it 22 C. The temp in the pot is now 40 C. The outlet temp is 36 C (again reflecting the idea of a roughly 13 degree difference)

11:08 outlet 37 C
11:10 outlet 38 C

11:12 new bucket
I pour the bucket of water into the tank, raising its temperature to 26 C.
Outlet temp is 37 C
11: 13 outlet temp 38 C
11:15 pot temp is 42-43 C, tank temp is 26 C and outlet temp is 39 C, again confirming idea that heat gain at this flow rate is roughly 13 C.
11:17 outlet temp 40 C
11:21 pot temp is 44 C, outlet temp is 40 C, tank temp is 26.
We now see that to get a 40 degree bath from our system on an electric stove burner the input temp needs to be 26 degrees.

11:22 New bucket. After mixing, tank is at 29 C. Pot is 44 C. Outlet is only 37 C, but flow rate is faster for some reason...
11:26 outlet 38 C
11:29 outlet 39 C

11:30 New Bucket outlet hovers between 38 and 39 C, stabilizes at 39 C
11:35 outlet temp 39 C... Is the water in the pot now taking the heat we want to transfer to the copper coils?

11:36 new bucket, tank temp is 32 C, pot temp is 43 C, outlet is 39 C.
11: 38 outlet temp is still only 39 C, and not rising, even though tank temp is 32 C. If it followed the curve from previous results it should have heated to at least 45 C. How can that be? Are we at a point where heat is now being tranferred to the air from the water in the open pot? Helmut suggests that we should keep the pot sealed in the next phase of the experiment.

11:40 New bucket
Tank temp 32 C, pot temp is 44 C, outlet temp 39 C

11:46 new bucket, we cool off tank, making it 16 C. Outlet temp now 29 C.
11:50 we make tank 18 C, outlet temp now 28 C

11:52 New bucket; tank is 16 C, pot is at 33 C, outlet temp 26 C, jumping between 26 and 27 C.
Now we are looking at 10 degree heating difference. Has the flow rate really increased? Why and how?
11:55 Tank is 17 C, outlet temp 26-27 C. I restrict the flow rate with the faucet and temp rises to 29 C. I open it up again.

12:00 AM, new bucket. Added warm water to tank.
Tank: 22 C, pot 34 C, outlet 30 C

12:05 new bucket
Tank 25 C, outlet temp 30 C
12:10 outlet temp 32 C, clearly the water is not taking on as much heat, and we notice that the electric range burner is throbbing from bright orange to deep red. Is something wrong with the burner after leaving it on for over 2 and a half hours? We terminate the experiment. The 10 liter bucket is now full with 30 C water.


Much more experimentation needs to be done, which means more set up, more time, more mess, more trying the patience of Sybille's family and tying up the kitchen. Since our beneficiaries use gas burners, the results from the electric range oven may not be appropriate. We must test on a gas oven, and we must test at different flow rates. It was taking roughly 6 minutes to fill a 10 liter bucket, which is 1.6 liters per minute flow rate. Even if we could find a way to get the heat gain up, so that we were filling a 10 liter bucket every five or six minutes with 40 degree water, would that justify the effort and expense?

We need to calculate how long it takes to heat 10 liters to 40 degrees on the stove in a pot by itself. It may turn out to take roughly the same amount of time, in which case the only advantage of the heat exchanger would be if the output was piped directly to the bathroom, so that no carrying of hot water was necessary. This is assuming 1.6 liters per minute is an adequate flow rate for showering/bathing.

The cost of materials alone for this project was as much as purchasing a gas heater or electric heater in Cairo; we must see what the cost for materials is when purchased in Cairo (that will be the next step).

Perhaps a different design would work better -- is there a way to put the copper coil inside a hollow can (like a Nido Milk can) and place that directly on the gas burner? Are we losing heat by using a pot? By filling the pot with water? What is the best way to transfer the heat to the water in the copper pipes?

All of these are questions to be resolved through further experimentation. But that, of course, takes further investments in time and money and effort -- all things that the poor can ill afford, to say nothing of a graduate student long overdue on writing his thesis!