Dud Shemesh
(Solar Water Heater)
The Dud-shemesh is Israel’s national water heater and one of the defining symbols of the country’s urban landscape.
It's a system that provides hot water without the need for electricity or gas, and without the need to pay monthly bills. The system is located on the rooftops of residential buildings. 80% of all Israeli households use it and enjoy readily available hot water when the sun shines over the country – and it shines most of the year, providing heat for free.
How It Works
The system is made up of two separate units:
1. A water tank (or in short: Dud or Boiler) is a water-tight tank with insulating materials. 2. A solar collector (or in short: Kole’t) is a rectangular, flat metal box covered with dark glass and filled with pipes.
The collector is placed on the roof, exposed to the sun and angled correctly to absorb its rays. The sun's rays heat the water in the pipes, which then flow from there into the water tank (dud), and from there to the faucet inside the apartment.
In older residential buildings, the collector and the dud are placed on the roof, attached to each other, and scattered across the building's roof from where the water flows to the apartments.
In newer buildings, the collector for each apartment is located on the roof, while the dud is located inside the apartment or in a nearby space.
In new buildings with tiled roofs, the collector is outside and the dud is inside, hidden.
A solar water heater set: dud and collector
The Dud-shemesh system is one of the most prominent symbols of the Israeli urban landscape.
Anyone who looks down at residential buildings in any city or town can see rooftops covered with white duds or dark-colored collectors – sometimes together and sometimes apart.
Many people see this as an environmental eyesore that mars the landscape.
For the apartment owners and users of the system, this is not a concern – they enjoy the system, they rely on it to the point of addiction, and they don't care what’s up there on the roof or what it looks like from above.
They don't go up there anyway.
If there's a malfunction and the hot water doesn’t reach the faucet in their apartment, most of them call a professional to fix it, who will charge them a high price that adds to the overall cost of the system's maintenance.
For those who will go up to the roof and try to fix it with their own two hands, it won't be an easy task: they'll first have to figure out which of the many systems scattered on the roof belongs to their apartment. They'll wander among the tangled pipes that connect duds and collectors and try to solve the riddle: “What belongs to what?” They'll shake the pipes to look for a leak, twist handles on the dud, and might manage to diagnose the problem.
In most cases, even then, they won't be able to fix it themselves and will leave it to a professional.
The average cost of a Dud-shemesh system, including the dud and collector, ranges from $1,000-$1,500, depending on the tank's volume and the amount of water it provides – enough for a large or small family.
The average lifespan of the system is between 10-15 years, and if you want to enjoy a flow of hot water without problems, you should replace the old system with a new one on the date stamped on it.
Israel is considered a pioneer and a world leader in utilizing the sun for home heating. Its main competitor, China, is promoting the idea to Chinese households, but it is still relatively far from the widespread adoption seen in Israel.
On the state's 75th anniversary, it's hard to separate Israelis from the Dud-shemesh. It's a source of patriotic pride and is listed among the "most Israeli" products in public opinion polls. Although, this heating system is not originally ours, it was developed and produced here and turned into a basic fixture in every building, partly thanks to the fact that there is a law requiring contractors to install it in every residential apartment.
An Israeli rooftop: duds and solar collectors.
The Dud-shemesh system has existed in Israel since the 1950s.
In those years, right after the state was established, every home already had an electric water heater (boiler), but the price of electricity was too expensive. The economy hadn't yet recovered from the government-imposed austerity policy ("Ha'tzena"), and citizens had to "tighten their belts."
An Israeli engineer took an existing idea, modified it, and adapted it for Israelis.
The new development was called: Dud-shemesh, and in those days it was considered a global breakthrough. The system's unveiling captivated Israelis who were the first consumers to use it. The new system was not cheap, but the combination it offered – instantly available hot water, and money savings – encouraged many Israelis to install it in their homes.
In the 1970s, following the global energy crisis, the Israeli government decided that the Dud-shemesh would be a basic fixture in all residential construction, and the Knesset enacted a law requiring every contractor to install a Dud-shemesh in every apartment built in Israel. Exempted from the law were apartments in very tall buildings where the roof area was insufficient for effective water heating.
Since then, the system has been ingrained in the Israeli consciousness and so much so that people don’t really pay attention to a few small details related to its use:
A Dud-shemesh doesn't completely replace water heating with electricity or gas.
On winter days when the sun doesn't shine, there is no choice but to heat the water using a built-in electric heating element inside the dud. The size and volume of the dud also limit the water it can provide – a small dud will be enough for two showers, a larger one for four. And if there are more than four people in the house, they need to manage schedules and a "shower shifts" or turn on the electricity.
And if we get into the details and look at the numbers and cost-benefit calculations, it's worth remembering: Ultimately, these days, the average saving from a Dud-shemesh system amounts to 8% of home heating expenses.
With the rising standard of living in Israel, there are many for whom this number no longer makes an impression. They want hot water 24/7, with no favors from the sun. Whatever the cost. A few more dozen shekels a month? No big deal.
And perhaps that is the reason that in recent decades, the use of instant heating systems, using electricity or gas (like "Junkers" systems), has been increasing. An instant heating system is a reliable channel for providing a constant supply of water, especially in the winter when the sun is behind clouds.
Therefore, for many Israelis, both systems operate side by side. They complement each other, and you don't have to worry when you leave the house, because when you return, hot water will be available in any case without turning on the boiler.
Solar Water Heater - Here. All details and history
Tel Aviv rooftops, digitally processed photograph by Jacek Olejnik, 2013
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