Finally -- A Hand-Made Solar System Prototype that Really Works -- in Cairo Winters Too!

We did it: A do-it-yourself solar hot water prototype built from local and recycled materials that we can train others to replicate and mass produce!

This is the final version of our hand-made solar hot water systems for the Zabaleen community in Muqattam, Manshiyat Nasser (without the sytrofoam insulation on the hot water tank, showing how we wrapped a second 200 liter surfactant barrel (originally from Saudi Arabia, containing Sodium Lauryl Ether Sulfate, a.k.a. shampoo) with mylar (from the inside of potato chips bags and from sheets sold by street vendors at Attaba metro station), then bubble wrap (purchased at Moskee, near Attaba) then mylar. The final step was to build a 3 cm styrofoam box around the barrel, glued together with spray foam insulation.

This system heats up all 200 liters to at least 40 degrees on most winter days (except days of full cloud cover). The secret is in the placement of the float valve and the hot and cold water inlets and outlets. We place the Zahran floar valve 37 cm from the top of the tank and the hot water outlet (to the house) at 25 cm below the top (this allows the float valve to open and close as water is drained from the barrel, replacing it with the same amount of water from the blue cold water barrel top left).

Meanwhile, the hot water inlet to the panels is located 20 cm from the bottom of the tank, 10 cm above the cold water outlet to the panels (which is at 10 cm) . This is the Palestinian system we observed in Palestine, applied to our plastic barrel system.

The height of the brick column supporting the cold water barrel is 170 cm, and the height of the brick column supporting the hot water barrel is 115 cm, just above the top of the panels themselves.

The "secret" to our do-it-yourself solar hot water systems is our use of the Zahran Float Valve, created by Egyptian inventor Magdy Zahran, who has become a good friend.

Below you see the cold water tank, the hot water tank, then both tanks together:





T.H. Culhane had a hunch that toilet bowl flush float valves would enable the use of unsealed tanks in solar hot water systems and hunted around Cairo for one that could be used in a big tank. He stumbled upon a shop on Fagala street (Kamal Sediki Street) where all the plumbing suppliers are, and inquired of the shop keeper if he had any float valves suitable for a 200 liter tank. The man not only pulled the float valve (called a "Zahran Owama") off the shelf but asked T.H. if he would like to discuss his solar hot water project with the inventor himself, Magdy Zahran. He said, "he lives around the corner and I can call him."

Magdy Zahran took us to his factory and even brought us on Egyptian Satellite TV on a show called "The Missing Link" ("Al-Halaqa Mafquda") about local inventors to introduce our "Double Whammy" (Two Owama) Solar Hot water system using Zahran float valves and Zahran plastic input-output fittings, as shown here:

The use of these Zahran products is an innovation that enables us to radically cut costs and use relatively inexpensive and stable recycled plastic water barrels that are available all over the world, instead of using expensive steel tanks and expensive metal plumbing fixtures.

This is helping us bring costs down to a level the urban poor can afford.

Most families in our study area rely on water from a single standpipe at the entrance to their houses, and have few or no pipes running water to the rest of the house.


In our project we run three pipes -- a cold water supply pipe from the standpipe to the roof to fill the cold water barrel when there is water available, a cold water supply pipe to the bathrooms and kitchen in the house from a T where a pipe from the cold water barrel feeds into the bottom of the hot water barrel, and a hot water pipe from the top of the hot water barrel (that is to say, from the outlet 25 cm from the top of the barrel) to the house.

Needless to say, we put check valves on all our pipelines, to keep water from backflowing into the system. This adds to our costs but improves reliability (note that check valves can fail, so be sure and place them where they can be easily replaced).

This is what most families in our study area currently use to heat their bathing water (and they must store their water in numerous barrels and buckets as depicted). Our system gives them hassle free rooftop storage (200 liters cold, 200 liters hot) and provides adequate water pressure.





These are the kinds of bathrooms our beneficiaries currently have:

This is Talaat conducting our "hot water service and demand survey" for my UCLA Ph.D. Dissertation in Urban Planning, from which we determine who he beneficiaries of our US AID small infrastructure grant for solar roof construction:

Two of the children in the room, when initially asked what problems they had with hot water provision, said without prompting, "we learned in school that one day Egypt could be like Germany and use solar hot water systems, but we don't know when or how..."

Isn't that funny? "One day" a sunny land like Egypt will use solar energy like they do in cloudy, rainy Germany!? And here we are in the 11th hour at 5 minutes to midnight...

Fortunately this family will have a Solar CITIES hand made solar hot water system -- which they will help build -- by Christmas!


And here I am, blessed by having the chance to play Santa Claus to this Coptic Christian Zabaleen family:




And finally, here are some pictures of Solar CITIES field coordinator Hanna Fathy and his brothers Ayman and Romani and friend Hani building the system that will go on their roof: