Portable Solar Trackers

Passive Solar Works

If you are fortunate enough to have your home facing south with a fairly unobstructed view there are several things you can do. I am a huge fan of passive solar. It is much more efficient than active solar and it does not require much effort or money to see results.

You would be amazed at how much heat is produced on a good solar day using nothing more than a black surface a few inches behind a south facing window. You can take it a step further and place a cold air return to the basement beneath the window and place a portable black partition a few inches away. Do a search on “passive solar furnace”.

Trombe Wall

Also search for “Trombe Wall”, It’s a type of passive solar wall heating system that utilizes a “wall” made of material that’s effective at absorbing solar radiation, in combination with thermal mass, and is located just behind a window or wall of glass.

There are some companies that incorporate their systemsinto the design of commercial buildings to heat air and water supply.

I was allowed to do just about anything to my south facing Barn, that was my wife’s first mistake. My Barn was filled with outlandish experiments to heat, cool and provide power to.

My side door was made of steel with a glass storm door in front. The first few hours of every solar day produced a tremendous amount of heat between the storm door and the “WHITE” steel door. This inspired me to turn this door into a solar furnace. I had a 100 Watt solar panel with a bad cell, it still could power a DC computer fan but not much else, so I mounted the solar panel on the steel door. I drilled a 4″ hole at the top of the door and mounted a thermostatically controlled fan in the opening. 

The temperature in the void by 10 AM was between 140–180 degrees on a good solar day. There was a space at the bottom of the storm door where the sweep was that provided the cold return. It would have been better to drill a hole at the bottom of the steel door and install a thermostatically controlled damper so that I pulled air from heated space rather than pull cold air from the outside…but what I had worked great. In effect, I had created a Trombe wall like the picture below.

Solar Furnace

The challenge with passive solar is that it can be unsightly on the front of a home, this is not to say that the design above is unsightly but some solar furnaces actually extend out from the front of a window and I don’t think it is very attractive but neither is a high heating bill.

Evacuated Tube Solar Collector

The evacuated tube solar collector is another method of converting the Sun’s energy into useable power, in the form of heated water. These, also circulate water through copper tubing that is inserted into a vacuum tube and produce an incredible amount of heat which is then pumped to baseboard heaters.

Primary Components 

Evacuated Tube


Absorbs solar energy and converts it to usable heat. A vacuum between the two glass layers insulates against heat loss. The Heat Transfer Fin helps to transfer heat to the Heat Pipe.

Heat Pipe


Copper pipe with volatile fluid captured in bulb transfers the heat from within the evacuated tube up to the manifold.

Manifold


Insulated box containing the copper header pipe. The header is a pair of contoured copper pipes with dry connect sockets that the heat pipes.

Mounting Frame


Aluminum frame serves as the mounting base.

Basic Operation

Water is circulated through a closed loop system. Several heat pipes, filled with volatile fluid, extend into several evacuated tubes where they are heated. The evacuated tubes are in a vacuum and have a dark surface on the inside to absorb heat. Most systems have fins or thin metal threads to store heat longer. The volatile fluid is heated and moves upward transferring heat to the manifold. Water flows over and around the top of the heat pipe and this heated water is pumped to an insulated storage tank. A pump circulates this hot water to a baseboard heater.

Installation & Placement

Most of these systems are installed outside on the roof or lawn but they can also be installed behind a glass wall in a sunroom.

Passive Solar – DIY Anybody Can Do

What makes passive solar so incredibly efficient is the amount of energy that is created versus the cost to create it. Active solar equipment is expensive and not very efficient if you factor in the installation cost it much less efficient. Passive solar is an excellent project for the DIY person. Anybody can incorporate passive solar in one form or another. Heck, heavy black curtains mounted 5–6″ away from a south facing wind will produce heat. Extend the curtains to within 4–5″ off the floor and you are heating the space.

If you own a car with a dark interior you have certainly experienced the power of the Sun, the heat that is generated is sweltering. This is passive solar at work. You would be literally sitting in a solar furnace. I would not recommend running out and buying some insulated hoses and duct taping them from the car to the house, but it might be entertaining to watch. If your home, workshop or cabin has a southern exposure you might just try employing a few passive solar techniques to collect the Sun’s energy. I will caution you against some of the more obtrusive techniques like installing a flat black metal absorber just a few inches behind your south facing windows where everyone can see it. This is viewed as hideous, ugly and unappealing…even after I hung a picture of the “poker playing dogs”.

Pictured above is my passive solar barn. The front is double-walled polycarbonate with flat black steel corrugated roofing (the absorber). The garage door is controlled by a PLC controller that measures the outside air temperature and the temperature behind the polycarbonate. When the outside air is less than 45 degrees and the temperature behind the polycarbonate is greater than 90 degrees, the garage door will open exposing the black absorber. The temperature can and will rise quickly even on a cold but sunny day. I have measured temperatures greater than 180 degrees.

When the thermostat in the workshop calls for heat, the fan turns on and 2 cold air returns open allowing a good exchange of air. When the Sun goes down, or the temperature of the void is less than 90 degrees the garage door closed, the cold returns closed and the fan turned off.

What I would recommend is staging dark colored objects and opening the blinds and curtains. We do just that on all of the south facing windows and we cut-off the heat to those rooms. A well placed cold air returns beneath the windows would do a world of good but then the “voice of reason”, often referred to as my wife, slams the door on the idea.

Your particular situation may be different, your wife might trust you with a circular saw…truth is I don’t trust me with a circular saw.