David Butcher's Micro Solar Energy System

I have always been a solar energy nut. I finally have a small photovoltaic system up and running, generating 12 volt power (though in very small amounts) and providing me with a way to learn what I need to know before I expand to a large scale "off the grid" system.

Note: This article describes several different systems. They are used daily.

I began the small solar lighting system to light one dark hallway and my garage. Of course, things have progressed from there. Solar electric systems are easily expanded, and I started with a very small system. I had plans to expand it over time. Here is the chronology:

The project actually began in the 1970's when I begin building solar cell panels and teaching workshops on panel construction. Among the many small solar panels I built was a 12 volt, 1 amp panel built with single crystal 3 inch silicon cells. The panel had never really been put into service, but through all my travels I kept it with me, and I finally decided to celebrate the new millennium by permanently installing it and finding something useful to do with the power it generated.

The first installation consisted of a Trace C12 charge controller, two very small (4 AH at 6 volt) gell cell batteries and a white LED light of my own design.

The light has 6 white LED's, arranged in two circuits, with a fan switch which gives bank A, bank B and both banks with successive pulls of the cord. The light tube is free to rotate, giving the light the ability to be directed through a 180 degree arc. Power is 12v DC, and each bank of 3 LED's draws 20ma - yes, twenty milli-amps. The entire light, including switches, materials, LED's, screws to hook it to the roof and even the wire inside the light cost under $25 !!

The light is a prototype. I will construct a brighter version when the next set of LED's arrives. Here is a closeup of one end of the light to show the two-way pull switch.

It's not a twin tube 40 watt fluorescent shop light by any stretch, but it is impressive how much light can be produced by running only half a watt through these little solid state lamps.

I will create detailed plans if anyone is interested.

Mon Sep 04 17:31:21 PDT 2000

Well, the "micro" name may have to be dropped. I have added three more solar panels to the system. Here are the details:

  1. I bought a small (250ma, 12v) panel on sale at Real Goods for $39 (regularly $69) and wired it in. It is weatherproof, has it's own blocking diode, and it is now mounted fairly high up on the eaves.
  2. I took my oldest 12v panel, 30 200ma "satellite" cells assembled into a panel in 1982, and mounted it in a clear skylight. This panel only produces about 15v instead of the usual 18v (36 cells is typical), so it is more valuable when there is a load on the system or when the batteries are fairly low.
  3. About five years ago I bought 4 used solar panels for $75 each. In July I built a redwood frame (aluminum is sometimes referred to as "solid electricity" because of the amount of power (i.e. coal/oil/nuclear) required to produce it. Redwood is renewable.) to hold the panels. Everything went well, and I now have a 4 foot square panel. That is large enough to produce around 100 watts! The panel lives on the roof of the garage, and I use the power it generates to recharge everything inside the house on "Sunday" every week.

Now the system is starting to really produce some power! In fact, I found that the combination of small panels kept the batteries charged all week, running the LED lights I had in the hallway and in the kitchen, and I had enough power with the big panel to run a solar powered drip coffee maker on the weekend! Even after making coffee, there was power to spare.

I am now cleaning up the system and considering adding more lights in several places in the house. With 28AH of batteries and the panels I have, I can probably have two or three times as many LED lights as I have now. I will be building more lights soon, and I will also create a diagram of the system to show how all the pieces fit together.

Sat Sep 16 23:06:50 PDT 2000

Today I made some progress on system reliability. I followed instructions from Home Power magazine, and built a battery desulfator circuit. This circuit pulses the batteries with high current, high frequency current which results in elimination of sulfate buildup. The circuit is small, and it looked easy to build. I have it working on an old 25AH Gell Cell battery that I bought new, never used, and is now severely sulfated. Something is definitely happening, as the charge current on the battery is gradually increasing from almost nothing (3 ma). I'll post the results here, but it may take several weeks to determine whether the battery can be saved.

Sat Nov 25 09:43:12 PST 2000

Big changes are taking place. The solar system has become a tangled mess of wires, inverters, alligator clips and cords. Today I will work on organization. I will present photographs later today showing how the different components fit together. To make a presentation, I have been attaching the components to one foot square ceramic tiles. While this will take up more space on the wall, it will also enable the system to be cleanly organized and modular.

Sun Feb 17 19:42:39 PST 2002

Wow. The time flies. I have had white LED's in our walk-in closet for almost a year. They are powered by three Ray-O-Vac D Alkaline rechargeable batteries, charged weekly using a small (140 watt) 12v to 120v inverter, and an Ray-O-Vac battery charger. The system has worked like a dream. I have a small microswitch (Radio Shack) on the door, and the LED's turn on automatically when the door is opened. 90% of the time my wife and I use this light source instead of turning on the two 40 watt florescent lighting fixtures. Fabulous!

Elsewhere in the house, I have created more LED "strip lights." Under the kitchen cabinets, I have three sets of three white LED's where I used to have 110v strip lights. These LED lights are wired (though the kitchen wall) to the 12 volt power source in the garage. A simple pull-switch turns them off and on. With these lights available, the 150 watt track lights in the kitchen are seldom turned on. Another big win for solar energy!

I have also created a 6 LED light fixture for the short hallway between our house and the garage. This simple fixture has two features. It is turned on by a microswitch, just like the closet lights, and it has several large capacitors (about .1 farad) in the circuit with the LED's, so the light does not turn off immediately! This allows me to walk out into the garage and then back after the door closes. The door closes automatically to comply with fire codes.

These projects have enabled us to "kill" a number of 120v grid powered lights. While the 120v lights are still available, the 12v solar LED lights are automatic, and they are almost always enough. Simple, easy, cheap, and hundreds of times less power-hungry than their 120v counterparts.

Mon Oct 28 18:39:58 PST 2002

Big changes! Since the last entry, my wife and I bought a house. In the process of moving, every solar system had to be taken apart. Little by little, I have been putting them back together. One of the systems I cannot live without is the under-counter lights in the kitchen. This time, as I built the system, I took some pictures of the process. I believe anyone could do what I did, and create similar lights. These lights are powered by rechargeable batteries, and the batteries are charged with solar electricity, so they are "off-grid." Here are the details.

Thu Nov 7 15:45:57 PST 2002

A strange thing happened today. It is raining, so I figured it would be a good day to clean up some of the wires on the Microsine Inverters (OK4 for you NKF fans). When I did my ususal "finger test" to see if they were warm (active), one was stone cold. Now I admit it was raining, and I did not expect much power to be generated, but the other one was noticeable warmer. I went inside and got my laptop computer, hooked it to the OK485 computer interface, and checked up on the inverters. Sure enough, one was putting out 15 watts and the other was at zero. Interestingly, the one at zero said that it could not read the "plug" voltage: 120 volts AC. After much fiddling, and switching wires around, and "rebooting" the inverter by unhooking it from both the 120 volt AC line and the 24 volt DC solar panel, I was ready to give up. Then I rememberd one of the old tricks I had learned back when I repaired computers for a living. I took a screwdriver, held onto the metal end, and whacked the inverter with the handle. It immediately fired up and began producing power. Sometimes the low-tech solution is the best solution. I have mailed NKF tech support for suggestions. It could be a cold solder joint, or some other problem. Whaterver is was, it is "fixed" for now.

You may be curious about the potential power output of different size solar panels. I created this solar panel power output calculator to make it easier for me to experiment with different size solar photovoltaic arrays. It's not very precise but it's good enough to give approximate values. There are other similar calculators on the Web, just ask your favorite search engine.

Fri Apr 10 08:13:37 PDT 2009

The end of the story - the system is still working! I moved again. The same little batteries and the same controller and panels are in my garage, where their micro solar power is run through an inverter to provide power for small items in my home office.

The Microsine inverters were both destroyed by an electrician's mistake, so the 100 Watt panels (4 of them now, each named after a favorite pet) are wired in series to directly power a 300 Watt heat lamp that shines in my legs while I work. No inverter, no controller, just comfortable infrared heat. I have turned off my heat, and I am saving around $00/month by using this system. Pretty cool!

David "Photons, not Neutrons" Butcher

PS. If you alerady have a small power system like this, why not add Pedal Power to it?


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David Butcher
Tel (408) 978-5495
Los Gatos, California 95030

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