A Great Integrated Tank Solar Collector System
 
  Where temperatures are not likely to drop into the freezing zone, many evacuated tube solar collectors are made with an integrated storage tank at the top of the collector. This design has many advantages over a system that uses a separate standalone heat-exchanger tank. With the tank separate, you are required to operate solar controllers, water pumps, expansion tanks, etc. All this extra equipment can greatly increase the cost of the system. The separate heat exchanger tank can also be the single most expensive component in your system.

With the tank included in the design, water flow is controlled via your standard household water pressure. The reduction in electronics not only reduces the cost but also reduces failure points and operational complexity.
       
   
  Globe Solar Energy has recently introduced a model to the Canadian market (yes that's in an area with freezing temperatures), which has governmental approval to be included in their ecoAction program. This unit comes with a built in heating wire for the outside piping and a controller to turn the heater on if needed. The cost of this simple system is half of the cost of a closed loop glycol system. This product could greatly increase the acceptance of solar water heaters in cooler regions of the globe.
   
 
 

Evacuated-tube collectors can get very hot, exceeding the boiling point of water and can cause significant issues in an existing domestic solar water system. You need to use your hot water every day to ensure the temperature doesn't overheat in the tanks. Mixers are easily installed just after the last hot water tank and mix your regular (cool) water supply with the hot water, to ensure the temperature never exceeds a set limit.

Notice on the picture above, the black hose leading away from the pressure relief valve on the top of the tank. After only a single day without use, this tank could exceed the temperature and pressure levels, blowing hot water onto the lawn and killing the grass. The black pipe was added to safely take the hot water away to the drainage system. On a ground mounted panel, you can also cover the unit before leaving the house for an extended period. Be careful of the tubes when covering them, as they are made of annealed glass, which is more delicate than tempered glass. You need to consider overhangs (slide ice and snow loads), falling branches, etc., when selecting a location for your panels.

Evacuated-tube collectors don't heat up like flat-plate collectors. Thus in the winter, they won't melt large quantities of snow that fall on them at one time. It can be very difficult to clear the snow from the glass tubes without breakage, be careful. Of course, heat-pipe evacuated tubes will not impact the system if they break - you just have one less tube to heat the water. If a direct-flow tube breaks, you have a problem!

   
 
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