Integral Passive Solar Water Heaters – A Primer

Integral Passive Solar Water Heaters – A Primer

Integral Passive Solar Water Heaters – Intro

Before we discuss integral passive solar water heaters (IPSWH), let us talk a bit about solar systems. Increasing energy costs have focused attention on energy efficiency and alternative sources. Renewable sources of energy appeal to the preparedness minded. It helps Preppers disconnect from an energy delivery system that is vulnerable to failure when necessary. It also allows Preppers to be in control of their own energy instead of relying on some distant corporation or government bureaucracy. Solar energy plays an important role on many homesteads, bug out locations and is especially important with many cultures overseas because it is readily available and free. It can also be used for cooling as well as heating. As long as the sun is shining the Prepper can collect, store and use its energy.

Solar water heating systems fall in to two categories; active and passive. Active systems are more expensive and technical. Simply explained, they rely on auxiliary power to run fans and pumps. Passive solar systems are typically more simple and cost less. The only moving part in the most simple systems is the sun. Talk about reliability. There are two class of passive solar water heaters. In one systems heat is collected and stored are separate. These are called thermosiphon flat-plate systems. The the other class collection and storage are combined. IPSWH fall in to this latter class, and hold some advantages over the former. They tend to be more simple, more economical to build and maintain, and more resistant to freezing.

Integral Passive Solar Water Heaters – Principles of Operations

Integral passive solar water heaters (IPSWH) centered around some sort of tank, or series of tanks. A common, and inexpensive source for these tanks are discarded water heaters. The tank is painted black, in order to maximize the amount of heat from the sun that is collected, which then heats up water stored within. In order to increase efficiency, a collection/storage tank is placed on a south-facing wall, or roof top, and is insulated to reduce heat loss. Cold water is brought in via an inlet on one end of the tank , it is heated up, and then moved to a back to a back heater. This is usually a gas, or electric-powered conventional water heater. Waterline pressure is used to move the water, so no external pumps are needed for the system.

In sunny locales, or during summer months, the conventional water heater can be turned off or bypassed entirely. The IPSWH can provide all your hot water needs. In colder climates, and during winter the auxiliary heater is used to augment the IPSWH. To protect against freezing, should the need arise, the system can be drained, and the conventional heater can provide household hot water.

Integral Passive Solar Water Heaters – The 6 Commandments

The design, installation, use and maintenance of integral passive solar water heaters are governed by certain principles. If you follow the 6 commandments when you design and install your IPSWH it will work efficiently and provide your household with inexpensive hot water.

1. Locate your heater for maximum sunlight.
Place your IPSWH on a sunny southern exposure. It is preferable that be close to your back-up heater, to reduce heat loss during water transfer.
2. Make the collector as efficient as possible.
Tanks come in a variety of sizes. Most of them are usable. Long thin tanks have the highest surface area to water ratios. Used water heater tanks tend to be the cheapest. Make sure your tank is in good condition, so it will last longer. Next, make sure your tank is in a good location for exposure, as well as maintenance. Finally, use reflectors to concentrate sunlight on your collector tank.
3. Make sure your tank(s) will retain heat.
Use a good quality glazing to enclose your tanks in the their frame. Caulk and seal your panes tightly. Inlet and outlet pipes should be insulated, as well as your back up heater, to reduce heat loss.
4. Make sure your heater is properly sized.
You should allow about 30 gallons of water person in the household.
Proper water per square foot of glazing ratios will maximize heating, with 2.5 gallons per foot being recommended as optimal. that works out to 12 foot of glazing per person. Smaller ratios will speed up heating. Even an undersized system will provide preheated water, reducing water heating costs.
5. Make an efficient connection to the back-up heater.
Minimize the amount of piping needed to connect to your back-up heater. Insulate all piping. Heat taping exposed pipes in cold climates is a must.
6. Build your system to last.
Even if you are budget, use the best materials you can afford, or scrounge. Good materials and construction will ensure your system will last a long time, and be safer in the process.

Integral Passive Solar Water Heaters – 5 Basic Types

  • Single Tank IPSWH – This type uses a single tank to provide solar heated water. Household units run from a simple setup of a used water heater tank enclosed in an insulated plywood box to more elaborate setups placed on roofs with internal shutters and tilted frames.
  • Photo Courtesy Integral Passive Solar Water Heater Book by David A. Bainbrid

    Photo Courtesy Integral Passive Solar Water Heater Book by David A. Bainbrid

    A Greenhouse IPSWH – best used in cold climates, this model provides protection against freezing. The IPSWH is enclosed in a protected sunlit space. Ideally, an attached heated green house is the best choice, hence the name.

  • An Inverted IPSWH – Another cold weather setup, an inverted IPSWH protects against cold weather and night-time heat loss by turning the IPSWH system upside down. The insulated part of the housing is facing the sky, and sunlight is sent to the collector via a series of reflectors.
  • A Low-cost IPSWH – This simple system is nothing more than a cheap solar collector hung in the sun to heat the water inside which is gravity fed through the shower head. This type of unit provides the best BTU/ dollar heating but is best used at campsites, RVs, and summer homes that are not used full-time.  One example of this type of system is the Solar Camp Shower.

Integral Passive Solar Water Heaters – Building Your Own, A Simple Rundown

Glazing & Tank relationship.  Photo Courtesy Integral Passive Solar Water Heater Book by David A. Bainbrid

Glazing & Tank relationship. Photo Courtesy Integral Passive Solar Water Heater Book by David A. Bainbrid

Here is a simple run-down of the steps used to build your own itegral passive solar water heater:

1. Select your location – Remember Commandment 1
2.Design – Design your own, find plans in books, on the internet or buy commercially avaiable plans.
3. Construction – Build the frame, Fit the tank(s), cover the outside, insulate, cover the inside, plumb, test and glaze.
4. Maintain – Proper maintenance of the tank(s) and plumbing will ensure efficiency, safety, durability and longevity.

Intergral Passive Solar Water Heaters – Conclusion

Using an itegral passive solar water heater is the most efficient and economical method for providing hot water for a homesteader or those on a budget. Economy and efficiency while preparing and living a more self sufficient life-style are corner-stones in the FSP philosophy. IPSWH’s touch on several areas of the FSP doctrine. If you are interested in learning more about integral passive solar water heaters, you can read “Integral Passive Solar Water Heater Book” by David A. Bainbrid for a more comprehensive and in depth look at the subject.

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