Sunday, April 7, 2013

Taking Solar Thermal to a Next Level

Between 50 and 70% of Palestinian households are using solar water heaters. Typical roofs look like this:

Those passive "thermosiphon" solutions are great for a start, mostly manufactured locally in Hebron, and widely available at low cost, but there is a lot of room for improvement:

  • Poor insulation of collector, storage, and pipes, so that in the winter time you will hardly have warm water
  • Small storage capacity, so if you wash dishes with warm water in the evening, the next morning your shower will be cold for all household members
  • Lots of wasted water -- before your shower gets warm, you have to let it run for several minutes and waste maybe 10-15 liters.
  • Heat can be used for water only, not for floor heating.

Potentials of new Technologies

Vacuum tube collectors -- have better insulation and give much better yields especially in wintertime, and require less space on your roof.

Circulation pumps -- insulate your water pipes and let the hot water circulate using a small pump. This way you will have hot water immediately as you open the tab, and no need to waste 10 liters of cold water before every hot shower you take.

Heat storage -- modern storage and heat exchange systems are much bigger in capacity, often located in the basement, and serving an entire apartment block. So even on rainy days you don't need to worry about hot water for your shower.

Space heating -- are you still freezing in wintertime, because you want to save hundreds of dollars of diesel heating cost each month? Investing in a large heat storage and plenty of vacuum tube collectors on your roof could be the solution.

Early Adopters

Several companies are selling vacuum tube passive thermosiphon solutions like this one. I saw some shops in Al Bireh. If you want to go into that business, look on Ali Baba, and you will for sure find a Chinese manufacturer that wants to export them to you. 

So far, those appliances are not yet manufactured locally. Here is a video describing the manufacturing process:

You would probably need a technology partner in order to establish a local production, for instance Ritter Solar.

The city of Rawabi offers to its residents a solar thermal solution that has the heat storage tank on the balcony, instead of the rooftop. This solution employs a circulation pump, and reduces water losses. The same heat storage tank is used for the gas burner, and there is an electronic controller to use gas once the water temperature is dropping too low. So you have not only reduced water loss, but also more convenience.

The company of Royal in Hebron offers comprehensive solutions, including large heat storage tank, circulation pumps and electronic controller. This picture is from their brochure:

Future Outlook

The use of concentrated photovoltaic (CPV) together with solar thermal is a promising future technology. A parabolic mirror reflects sun onto a small high-efficiency photovoltaic module for electricity generation, and the assembly is cooled with a cooling liquid, whose heat can be stored, and used for solar cooling, solar heating, hot water, space heating, etc.

Have a look at their prototype, which is promising an energy collection rate of up to 70% (combined heat and electricity):

Stay tuned what comes up from


  1. You really delivered reliable information. Thank you regarding discussing energy

  2. I am happy to read like this, As increasing pollution and global warming we must choose the renewable resources as they never cause any harm to our environment. Solar energy are clean and renewable sources to help our environment.
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