A Low Cost Single Axis Manually Operated PV Tracker Bob McCormick A PV array with tracking ability will yearly produce about 25% more power than one mounted in a fixed position. A tracker can reduce the number of PV modules required for adequate power production. It should be maintenance free as possible. A PV tracker should be affordable. Trackers must not operate by any means that may be harmful to humans, animals, or the environment. Why Tracking is Beneficial We purchased our first PV modules in November, 1985. They are 8 @ 45.7 Watt Kyocera modules, producing 2.74 amps at optimum insolation levels. They power a 12 volt DC hybrid system with a Trace 2 kW. inverter. Living in northern British Columbia Canada above the 56¡ North latitude, means we have a small number of sunlight hours in mid-winter, only about 5 hours per day in December. We live in a valley with hills on the East and West sides. These shorten our sunlight hours by 1 1/2 hours per day during the winter. We knew that in order to get every Watt our PV array could produce, it must have tracking ability. We also knew that winter tracking adds 10% to 15% (much more in the summer) to the overall power production of the array. This may not sound like much, but it adds about 10 ampere-hours more per sunny winter day. This represents enough power to light a 30 Watt fluorescent fixture for 5 hours. It would run our DC water pump for almost 2 hours. No Passive Tracker Our home is located at mile 132 on the Alaska Highway in the Pink Mountain area. Winter temperatures often reach - 40¡F. and lower. Passive tracking devises using solar heat will not operate in these temperatures, no matter how bright the sunlight. This would mean we must use a powered tracker of some kind. I must be motor driven or manually operated. We wrote to various manufacturers requesting literature and prices for motor driven trackers. We received two answers (a majority never answered at all) and the prices quoted were completely beyond our finances. we would have had to sell the ranch to pay for one. Necessity is the mother of invention. We put our thinking caps on, and went to work. We would build our own manually operated tracker. Scrap Pile Holds The Goods Almost every farm and ranch in North America has a scrap iron pile. Ours yielded 2 pieces of pipe that looked promising for our needs. We chose one piece of 2 7/8 inch outside diameter pipe which was 7 feet long, and we left it this length. The other piece was 3 1/2 inch OD from which we cut a 16 inch piece. It had an inside diameter of 3 1/8 inch and would slide freely over the 2 7/8 inch pipe. Both pieces had a 3/16 inch wall. We found a mild steel 3/8 inch plate that measured 40 x 30 inches. It was somewhat bent, but we managed to straighten it sufficiently to meet our needs. Having an acetylene torch and a portable welder are almost essential where we live. This is 100 miles from the nearest town and 50 miles from the nearest power lines. We cut one piece 14 x 40 inches from the steel plate, and another smaller piece 14 x14 inches square. We cut the corners off of the 14 x 14 piece at a 45¡ angle, for which purpose will be explained later. These two pieces would serve as base plates for the array to turn on. We then cut a hole in the center of the 14 x 14 plate that would allow it to slide over the 2 7/8 inch pipe. We placed the plate 15 inches from one end of the pipe and squared it to the face of the pipe. It was then welded to the pipe on the side of the plate toward the long end. Next, a hole was cut in the center of the 14 x 40 inch plate that would allow the 3 1/2 inch pipe to slide through. We welded the plate flush with one end of the pipe, squaring it as before, and making the weld on the long pipe side of the plate. The welds were made in this way, so they would be on counter-opposed sides. The two plates would meet exactly together with no gap between, when the 3 1/2 pipe was slid down over the 2 7/8 pipe. In the center of the 16 inch pipe (length wise) we made a hole slightly larger than the thread diameter of a 3/4 inch bolt nut. A 3/4 inch nut was centered over this hole and welded to the pipe. We then took a 3/4 x 14 inch bolt, heated it in the center (7 inches from either end) and bent it to an approximate 80¡ angle. We coated the threads with bearing grease and screwed it into the nut we had welded to the 3 1/2 inch pipe. This bolt would serve as a simple but secure locking pin. By only a slight tightening of the bolt against the inner pipe, it prevents the array from turning in even the strongest wind. Loosening the bolt just a partial turn, would allow the array to be turned with ease. Cutting the corners from the 14 x 14 inch plate was necessary to allow the bolt a full 360¡ turn capability. When the plates were in various positions in relation to each other when the array was being turned, the bolt would not make a full circle unless the corners were removed. The Only Materials Purchased At this point all we needed to complete the tracker were two pieces of 4 inch channel iron. Each would be 82 inches long and be bolted across the ends of the 14 x 40 plate. This length was necessary to allow the panel mounting structures for the two sections of the Kyocera array to sit on. Each section sitting tightly against the sides of the 3 1/2 inch pipe. The channel iron pieces were centered, one on each end of the plate and two holes were drilled in each pipe, and the plate. These were 3/8 inch and (2) 3/8 x 2 1/2 inch bolts were used to secure the channel iron to the plate. The two pieces of channel iron were the only materials we had to buy. For a different make of module, the length of these two pieces of channel iron are all that need be different. To mount a single panel width structure, simply straddle the pipe and make the channel iron pieces slightly longer than the width of the base of the panel mounts. Ready To Anchor Add some paint and the tracker is ready to anchor in Mother Earth. Choose a location that has a good solar window and is as close to your controller or batteries as possible. Make a hole in the ground approximately 3 x 3 feet and 3 feet deep. Place the long pipe with the 14 x 14 plate up, into the hole. Use the plate to set a level on and cement the pipe in place, making sure the plate is level. After the cement is properly set, coat the top of the plate and the outside of the pipe above it liberally with grease. Slide the swiveling section, which contains the long plate and channel iron cross pieces, down onto the base. You are now ready to mount the array. We secured the array mounting structures to the channel iron with four 3/8 x 1 inch coated bolts. Two in each base piece of the mounts and in the back pieces of channel iron. Routing The Power Cable After the array has been mounted on the tracker, the power cable from the array is run over the front edge of the 14 x 40 inch plate. Leaving 3 to 4 inches of slack in the cable, bring it under the two plates and over to the pipe beneath. Tape or secure the cable to the pipe and then down to the ground. Bury or otherwise protect it. The 3 or 4 inches of slack in the cable, allows the array a tracking arc in excess of 250¡. The cable we used for this section, from the array to the pipe or ground, is No.6 or 8 soft stranded copper, with a butyl rubber coating. This allows flexibility at the most extreme temperatures and hundreds of repeated flexings. After four years this cable has shown no signs of cracking or deterioration. No Maintenance and Costs To Build The first of these trackers we built in the winter of 1985 still has the same array on it. The original grease (none has been added) is still there and the array moves as freely and easily as the day it went into service. This tracker does not require Freon to operate, or anything else that may be harmful to the environment. All it requires is a small amount of elbow grease a few times a day. Turning the array to face the sun directly only 2 or 3 times per day, adds considerably to power production. We also adjust the array angle to solar normal periodically throughout the year with the adjustable panel mounts. Our adjustable panel mounting structures are similar to those outlined in HP#2. We have a number of these simple trackers for some of our customers over the last four years. We have made them to hold from 2 panels up to 12 and the simplicity of design and ease of use have made them quite acceptable. If you do not weld or have access to a welder and acetylene torch, you should be able to have this tracker made at your local blacksmith or machine shop. At present prices for materials and labor it should cost less than $200.00 in Canada and about 20% less than this in the United States. Access For a detailed plan of this construction, send an SASE to: Bob McCormick, C/O Northern Alternate Power Systems PO Box 14 Pink Mountain, BC Canada V0C 2B0