Inexpensive Solar supplemental heating system and how to build a solar collector at home

New whole-house solar heating systems initially cost $14,000 or more. In contrast, a conventional heating system might cost $6,000 to $13,000 for the same size house. The cost fluctuates depending on the size, type of house, location of house and amount of solar fraction available.

If you have an existing radiant/space heating system you can reduce the cost of your new system by adapting any solar radiant/space heating kit such as SunMaxx HH-1000/1500/2000/2500 from the Silicon Solar to your existing system. And by adding an Air-to-Water heat exchanger you can integrate your new kit even into your existing forced hot air system!
For a house of 1000 square feet an installed SunMaxx HH-1000 kit will cost you from $12,000. This kit designed to assist in offsetting approximately 192 gallons of heating oil annually, because it contains two very efficient SunMaxx-30 solar collectors.

But I think it's very logical to spend much less amount of money to see how solar heating really works in your specific area.

I used 2" x 4" pine boards and 5/8" plywood to build the solar collector frame/box. Then, I painted the whole unit. The frame size is 36" x 79.5"

For my thermosiphon heating system I used 2" x 6" pine boards

All frame seams were sealed.

I also used a one-inch insulation board with aluminum foil (back side). It works not only as an insulator, but also as a heat reflector.

You can use high density (rigid) polyisocyanurate foam - melting point is 177 degrees Celsius or
expanded polystyrene - melting point is 240 degrees Celsius.

For my collectors with 2" x 6" boards I used Super TUFF-R(TM) C 2.00 inch commercial insulation sheathing (modified polyisocyanurate rigid cellular polymer)

Manufacturer - DOW
Melting Point >150°C/302°F
R-Value - 13.0
Size - 4' X 8' X 2"
Price -$37

Insulation board installed.

The seams of the insulation board were also sealed.

In order to test the effect of black tar-paper as an absorber, the solar collector box was temporarily divided into two sections. The left section contained tar-paper. During a period of several hours, I tested the temperature inside each section.
The better result was reached in the section with tar-paper.

The main components of my collector are black painted hot water baseboard heating elements (copper pipes with aluminum ribs).

or you could simply use black painted 1" or 3/4" copper pipes as I did for my thermosiphon system (right collector on the picture below).

Solar collectors assembled and covered with double glass sliding door section to trap and hold in sunlight/sun's energy that is not immediately absorbed by the heating elements in a method similar to a greenhouse.
The solar collectors cost includes the cost of materials, which are about $250-$300, and approximately 20 hours of labor.

This 12V/15W solar panel ($79.99) feeds water pump/circulator.

12 Volt DC pump - $79.99

You can use 12 Volt DC brushless pump also.

To reduce final cost of your system, you can use a thermosiphon (alt. thermosyphon) principle - a passive heat exchange without the necessity of a mechanical pump and controller!

The baseboard(s) must be installed above the top of the collector, therefore I installed an additional baseboard in my living room
Thermosiphon systems rely on the natural convection of warm fluid (water/antifreeze) rising to circulate fluid through the collectors and to the baseboard, which is located above the collector. As fluid in the solar collector heats, it becomes lighter and rises naturally into the baseboard above. Meanwhile, the baseboard's cooler fluid below flows down pipes to the bottom of the collector, causing circulation throughout the system.
Thermosiphon systems are typically more reliable, because the systems are simpler than most solar water heating systems in that the need for both a circulation pump and a controller are replaced by the thermosiphon natural circulation.

I prefer Cryo-Tek -100 Anti-Freeze by Hercules Co.
5 Gallon, - $98

70% virgin propylene glycol with triple protection inhibitor Package, Pre-Mixed With Water, In A Ready To Use Formulation, Undiluted.

Provides:
- freeze protection down to -70ºF/ -57ºC,
- pumpable down to -80ºF/ -62ºC,
- burst protection down to -100ºF/ -73ºC.

5-6% Heat transfer efficiency bonus!
SPECIFIC USES: Use any cryotek AntiFreeze in hydronic closed loop heating and cooling systems, solar heating systems, and general plumbing systems that require freeze protection.

Cryotek Products are not recommended:
1. For use in systems containing galvanized components.
2. For open solar systems and systems where operating stagnation temperatures are regularly over 300ºF / 150ºC.
3. For systems with concentrating solar collectors or evacuated tube solar collectors.
4. In systems containing aluminum and operating temperatures over 160ºF / 71ºC. (Please check with equipment manufacturer of system to determine compatibility with this product).

February 21, 2009
Temperature inside of my solar collector

This photo shows that my solar collector is well-insulated.
Thanks to the insulation as well as properly chosen collector (heating) elements, the water in my solar collector reached boiling temperature.

November 11, 2010
Excellent performances of my thermosiphon system

The temperature inside of living room baseboard is 51 ºC
51 ºC = 123.8 ºF

Celsius to Fahrenheit calculator

February 22, 2011

The temperature inside of living room baseboard is 54.7 ºC
54.7 ºC = 130.46 ºF

Here you can see the live Broadcast!


The 16 feet long basement baseboard was installed below the solar collector. That means a thermosiphon principle will not work in such situation. Therefore I installed TACO hot water circulator (110 AC, $70), connected to the 175 Watt DC to AC power inverter ($30).
The solar collector is simply connected to the baseboard as a closed loop with glycol.

Thanks to the basic laws of physics, warm/hot air rises to the main floor of my house.
The house itself (walls, floors, ceilings, doors, furniture etc.) absorbs this warm air and keeps it for a long period of time, because my house is well insulated.


Temp.In - 100ºF (February 09, 2012 11:45 a.m.)

My solar systems are supplemental heating systems, and do not replace my existing heating system, which is based on oil fired hot water boiler.
Nevertheless, my solar systems helps to offset heating oil, because each solar collector can produce up to 15,000 BTU every sunny day.


  NOTES:
1. One gallon of #2 fuel oil = 138,500 BTU's (British thermal unit)
2. One gallon of propane = 91,547 BTU's
3. The BTU measures the heat of burning the fuel, and not the final heat delivered to the rooms of your home, because that depends on the efficiency of the heating system.
4. Insolation is the rate of solar energy arriving on a specific flat surface perpendicular to the line of the sun. At sea level, the least possible loss is 29 to 30 percent. The maximum possible insolation is therefore about 70 to 71 percent of the solar constant., or about 320 BTU per hour per square foot. No solar collector, regardless of shape or design can deliver more than this maximum possible value, without energy input from some other source.
5. New SunMaxx-M2 flat plate solar collector can produce up to 28,000 BTU daily or more than 1300 BTUs per square foot daily.
6. Each SunMaxx-30 evacuated tubes solar collector can produce up to 42,000 BTU daily or about 2000 BTUs per square foot daily under clear skies in a warm climate..
7. "The SunMaxx-M2 flat plate collector is typically recommend for use in warmer climates simply because they are designed with larger absorber areas that are not insulated from the colder weather. The SunMaxx evacuated tubes collector prove to be more efficient in colder climates and are recommended for use is these areas. However, because of the incredible advances in efficiency and durability made to the SunMaxx-M2 flat plate collector, this flat plate collector can also be used successfully in non-extreme mid and northern locations and climates." From Silicon Solar Inc.

Summary of SRCC certified solar collector and water heating system ratings

Evacuated tubes solar collectors

More about my experience with insulation

How to build heat pump Furnace or Water Boiler at home

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