Do-It-Yourself “Dude”: Collecting Passive Solar Energy
by Karin Kloosterman, Tel Aviv 
on 08.28.06
Every day of an Israeli summer is a beach day. With rarely a cloud in sight, it doesn’t rain for about half of the year. Faced with strong sunlight and desert climate, Israelis have found creative ways to make use of the Sun’s potential over the years. Most homes today are equipped with a “dude shemesh” (sun water heater)- a simple contraption where water from a tank is pumped into pipes coated with a black collecting surface. It is cheap, simple and reliable. Is the “dude shemesh” an Israeli invention? Israelis seem to think so. The dude in Israeli cities and towns is as ubiquitous as pigeons and hot dog stands in New York.
“American hot water heating is always on and is always wasting electricity or gas,” says David from Israel on Survival Blog. “Passive solar is cheap and simple plus it can be supplemented with electrical on cold days. Being in the West Bank I also see that the Arab homes and mansions will always have at least one dud shemesh.”
The simple black panels of the dude attract sunlight and become hot. The pipes transfer this heat over to the water, which runs back into the water tank. Unless your house has a “dude” you must be remember to turn the electric boiler on for hot water- or use a timer. Unlike in Canada, and the US the average Israeli house isn’t equipped to keep hot water brewing all day. Over here we rely on the sun, or a half-hour pulse of electricity needed to heat the tank for a shower or doing the dishes. In the beginning it was really irritating to have to remember to turn the tank off, but now I appreciate using only what I need. My electricity bills stay low.
David suggests the basics for a D-I-Y dude:
“If a commercial model is too expensive, construction is simple and cheap: the collector is about 1.5 m x. 75 m; and a 7 to 8 cm deep panel placed at the lowest south facing part of the roof.
Hoses carry the water up to the "dude" or tank, which is as high as possible. Israeli tanks are insulated when situated on the roof, but some cheaper and simpler models can be found in Arab villages where they make use of a simple black plastic tank placed on stilts.
Convection carries colder water from the bottom of the tank into the collector and hot water rises to the upper intake on the tank. On cold winter days we set the timer to run the immersion heater built into the tank as on days near-freezing the heater barely produces luke-warm water. A wood framed glass-paned collector with black painted PVC pipe would likely make a great collector and a plastic barrel would probably make a good tank with a little Bondo work. Insulating the tank would make for warm water in the early morning.
If a tank were suspended above the chimney it might be able to grab a few more precious BTUs from the hot gasses during the winter.
Israeli water heaters will run near boiling. It is possibly easier to heat and insulate a small amount of very hot water than large tanks of less hot water." :: Commercial company Makor Hateva :: Energy Crises Now ::Survival Blog
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Why is the water tank in the first picture painted White? Wouldn't it be far better to paint it black?
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Editor's comment:
All the storage tanks, it seems are painted white. I think that might be the industry standard, but perhaps something to think about doing. Tel Aviv- dubbed by UNESCO as the White City - might not be fond of black tanks - which you can see, versus the panels, which you usually cannot. But it is a good idea.
Painting the tank is a bad idea. The tank is insulated, the only way for a black tank to be usefull was if the heat was tranferred (conductive) to the water, in wich case the cold of night (when people take showers) would also be transferred. It would also degrage the insulation.
You could also go for a "dude shemesh" and instant hot water....
I think claiming that Isreal is the founder of this idea is a stretch. But regardless, they are only doing what so many others do in other parts of the world.
When I lived in the Dominican Repuclic, every house had one of these on the roof. As storage for water shortage and also to heat water for warmeth.
Here in Cape Town, many homes have solar water heaters on their roofs. It is normal to drive through the suburbs and see every other house with solar panels on the roof.
Point is, they are out there all over the place, not just Isreal.
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Editor's comment:
Good to know!
I have been living in Jeruslem for the past few years and the 'dood shemesh' ( I prefer to spell it that way ) is an integral part of the skyline , very jarring at times but let's leave the aesthetics for the time being . The dood works wonderfully well in the summer , we have hot water for the bath , for cleaning washing , infact we can even flush with hot water if we want . In winters, when you really need , the dood falls short . True we don't have harsh winters and even on a cold day you can have lukewarm water in the afternoon but very often the dood is located a couple of floors away from it is used , so you waste quite a bit of water and secondly invariable the electrical heating element is located on the tank on the roof which is exposed to the elements and inspite of being insulated is losing heat constantly . I don't have figures but I am told that the dood actually is less economical . If one factors in the cost of the collectors and the boiler and the fact that they need to be changed every few years , the dood is no longer that economical or green .
I've found these dotting the skylines of almost every city, town, and hamlet I've been to in the eastern Mediterranean region. I've heard the same things about their dubious efficiency..
This type of hot water heater has been around for about 150 years--I wonder why this site is always reinventing the wheel?
Here in Japan, this type of hot water heater is very common out in the countryside.
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Editor's comment:
I have lived in Israel for about 7 years and Israelis just assume that it is their invention. If you could trace the beginnings of the "dude" let us know!!