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!