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2 Responses to How does a passive type solar water heater work?

1. The biggest difference between passive and active solar is mostly a matter of “moving parts”.
   The simplest form of passive is a good south facing window, that you can cover with an insulator when it’s cloudy or at night. The solar comes in, warms up whatever it hits. That’s it…and that is every bit as efficient as any “installed” passive solar heating system. These systems are generally designed in, not retrofitted. Good windows are placed in the right places, and some type of insulation is usually used to cover the windows at night or when cloudy. The “storage” in this simple system is whatever the sunlight hits.

   “Passive” water heaters are tanks set in the sun, in an insulated box with glass on the south side. They work fine and are cheap, but they demand you pay attention. If freezing climates you have to protect the tank, and when it’s real sunny and you are not using hot water, step have to be taken to prevent overheating.
   So you can see that along the path, the “passive” systems become more and more “active”. Simple systems can be built cheap, but are not very “automated”…you have to watch the weather, open and close valves, drain things, etc.
   Many passive systems are built on site, while active systems use factory built collectors. Water, antifreeze or air is pumped through them and the heat gathered is stored for later use.
   From your statement about “panels”, I’m thinking you mean an active domestic water heating system.

   Your water heater is the biggest single appliance you have, besides your hvac, and you use it year round. Solar heating of that water is a good investment, while you don’t get too much in the dead of winter (and solar home heating systems don’t, either) you get 100% of your water heat for several summer months.
   At 40 to 45 Degrees north latitude (Madison, Wisconsin) a typical family of 4 can get 50% of the yearly cost of heating water from the sun, with a system that costs about $ 4000, installed. DIY’s, can do it for less than $ 1000 if they get used panels (there are a lot available) and other salvage.
   Typical systems have 60 to 80 square feet of collector, with an 80 to 120 gallon tank.

   If you live in a climate that seldom freezes, a simple and very cost effective “passive” water heater can be built very cheaply by any good DIY’er. Get a water heater…say 80 Gallon. Take the jacket off, plug the element holes, paint it flat black. Build an insulated box to put it in, glaze one side with a double layer of glass. Put the whole thing somewhere it can get good sunshine, tilted at about the same angle as your latitude. Cut the cold water feed to your existing water heater, and divert it to the bottom of that tank. Take the hot water off the top of the tank and run back to your cold water inlet on the existing heater.
   The solar will pre-heat the water to your existing heater. The heater will boost it to a final temp as needed. There is more detail to this, but that is basically how it can be done very cheaply when you don’t have freezing temps to deal with. Solar water heating in such areas, with this type of system is extremely cost effective.

   

   roadlessgraveled
   July 27, 2011 at 8:23 am
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2. A solar energy system is a low-intensity energy source that is commonly supplemented with other traditional energy souces,although it can be designed to handle 100 percent of a
   energy load requirement.A passive solar energy system does not employ circulators or fans but relies on natural(gravity)flow.
   One of the main considerations when solar energy systems are
   installed is the structural loading effect from collectors and
   supports.
   There is a established criteria for flammable and combustible
   heat transfer liquids in a solar collection system.That is the
   minimum temperture at which the liquid gives off suffucient vapor
   to form an ignitable mixture with air near the surface of the liquid
   (flashpoint).The heat transfer fluid is required to have a flashpoint
   temperature of at least 50%F above the max design temperature
   that it could reach while flowing through the system.
   This is designed on the location of where you live and location of the air to air collector that is installed in regards to sun light.
   To calculate the system you have to know how much(on average) of hot water you require per day.
   A typical active Space and Domestic solar water heating work like this, Liquid flows from the solar collector to the Thermal storage water tank thru the Furnace to a pre-heater to the water tank. All your required calculations will done for you before you buy the system by the installion company.This should show a
   economic statement for the area you live in.
   As always,get references from people in your area who have such a system before you invest in the system.
   Hope this helps.

   

   Lionman
   July 27, 2011 at 8:27 am
   Reply