Monday, September 22, 2014
Solar Ruminations - If At First You Don’t Succeed...
Rube Goldberg Contraption
There is an expression to describe the labors of those who find that their attempts at creation do not work as well as they had hoped. It is “Back to the drawing board.” This expression accurately describes my efforts in recent days to re-design my solar auxiliary power system in my bus. My first implementation of solar power proved to be less than adequate, necessitating an overhaul.
For those unfamiliar with my old solar set-up, I have four solar panels rated at 140 watts each. This is their rating per hour of power generated. Altogether my four panels can produce up to 560 watts of electricity per hour. Here in Georgia I could get as much as ten hours of good sunlight in the summer, which would produce 5600 watts of electricity per day. In the winter I may get only half that amount. On overcast or rainy days the power generated would also be well off the peak.
These are my four solar panels. I had built adjustable angle mounts so they could be positioned to face directly into the sun. The image above is NOT where they were put when in use, as any shade will collapse a solar panel’s output tremendously. When I used them I placed them in direct sunlight where they were not shaded at all.
The following picture shows the rest of my original solar set-up inside the trailer I pull behind my bus. On the wall behind the yellow electrical reel there is the solar charge controller, a 20 amp model made by HQRP. It was adequate to handle two solar panels, which is all I had connected to it. I had a second identical charge controller that I intended to install inside my bus. It would be connected to the other two panels, but I never hooked it up.
You can see a remote display above the charge controller that reported the amount of power coming in from the panels and the state of charge on the large battery that you can see on the floor below the charge controller. On the wall to the right is the inverter that takes the 12 volt DC power from the battery and converts it to 110 volt AC power to run appliances and other electrical devices. The inverter was rated at 600 watts. It was actually underpowered for my needs. I have a grain mill on the counter above the battery that has a 900 watt motor. The 600 watt inverter would not run it.
(For those who are curious, the object mounted to the countertop with the crank handle on it is a roller/flaker. You feed whole grain oats into the top of it, and as you turn the handle it rolls the oats between two metal wheels, flattening them. The end product is rolled oats - just like Quaker Oats that come in the round box. I keep the whole oats in 5 gallon buckets in my trailer. When I run out of rolled oats in my bus, I go out to my trailer and roll some more. They are much better fresh, and store better when they are not rolled. I eat a lot of oatmeal, especially in the cooler months of the year. They are great when cooked with the frozen blueberries or strawberries that I picked and put into my freezer. You can cook oats without rolling them, but they take about 20 minutes to cook when not rolled. They will cook up in about 3 minutes in the microwave when they have been rolled.)
After two years of sporadic use, I found that my solar auxiliary system did not meet my needs very well. It was cumbersome to place the panels on the ground, and store them in my trailer whenever I moved. Also, the panels do best when facing directly into the sun. This required frequent trips outside to reposition the panels so that they tracked with the sun. A solar panel that tracks with the sun will generate approximately 40% more power in a day than one that is stationary. That is a significant difference.
When I began to consider the redesign of my solar power system, one of the first items I gave thought to was the arrangement of my solar panels. I wanted to get the maximum power from the panels I have on hand. This meant setting them up in such a way that they would track with the sun throughout the day. A 40% power increase is the equivalent of adding another 1.6 solar panels. By using automatic solar tracking I could significantly boost my power generating capacity while keeping the same solar panels and not take up any more space in deploying them.
The optimum placement of the panels would be on the roof of my bus. In my brief experience with solar panels, I found that the shadow cast by my bus is a significant problem. It is necessary to keep the electrical cables running from the solar panels to the charge controller as short as possible. Longer cables increase voltage drop in the lines significantly. Longer cables means less power is being delivered to the batteries, for the power is lost in overcoming the resistance in the wiring. However, with short cables, it is difficult to position the panels on the ground where they will not be shaded by the bus at some point during the day.
Many people (including some solar panel installers) do not know that shading even one small spot on a solar panel can result in the power output being cut entirely, or significantly reduced, from the panel. This is due to the way the individual solar cells that make up a complete solar panel are wired. Following are some illustrations of poor positioning of solar panels, and the resultant power loss incurred. They are taken from Handyman Bob’s website.
The small shadow caused by the roof vent falling on the panel pictured above reduced the power output by 2.9 amps, almost 30% of the panel’s rated output.
The shadow on the panel above reduced the output by 50%.
The little shadow on the corner of the panel above caused by the raised roof vent diminished the solar panel’s output by 2.5 amps, 30% of its rated output.
And the shading caused by the satellite dish on the corner of this panel cut the power off completely. It registered as a dead panel. (I am sure there is a spiritual lesson in all of this somewhere. A little darkness will reduce the power and effectiveness of our lives, and the darkness that enters people’s lives by watching satellite television can kill a person’s spiritual life.)
As you can imagine, placing your solar panels under trees, or where the shadow from other objects can fall upon their surface, will seriously degrade, or kill your solar panel output. Last winter I drove my bus to Jekyll Island and spent four months there. I have four small solar panels mounted on the front of my bus to keep my cranking battery charged. Because I rarely crank the bus, sometimes being parked in one location without driving anywhere for 6 months to a year, the battery would die if it was not being constantly charged.
The solar panels at the front of the bus do a good job of keeping the cranking battery charged up and in a ready state - that is, as long as they are in direct sunlight. The entire RV park on Jekyll Island is under ancient Live Oak trees, and large pines. I did not think much about this, for there is light under the trees, and I figured the panels would charge my battery a little bit. I was wrong. About two weeks before my time was up I decided to crank the bus to make sure everything was running okay. I was surprised when it would not crank. The battery was dead. Fortunately, it had not drained so low in the 3-1/2 months I was there to kill the battery. I was able to charge it back up. When it comes to solar panels, shade is bad - real bad.
The four small panels that keep my cranking battery charged
(Yes, they are in the shade - but only part of the day at that location.)
At my present location, my bus is parked in a nice open spot without any overhanging trees. I have been here for most of the past two years, other than my trip to Jekyll Island. I have good sunlight access, but if the panels are placed on the ground they must contend with the shade caused by the bus. Consequently, one of my first considerations was to come up with a design to place my solar panels on the roof of the bus, and set them up to track with the sun.
For those unfamiliar with solar tracking, there are a considerable number of devices being marketed that detect the sun’s location in the sky and send a signal to a control box to power a motor to turn the solar panels. These devices are not all that expensive (compared to other components of a solar power system). A single axis solar tracker can be purchased for about $90 with sensor, control box and wiring (motors are extra). Dual axis solar trackers can be obtained for about $150. Some also come with inputs to attach an anemometer (wind gauge) that will tell the panels to lay horizontal if the wind rises above a preset limit. This is a considerable concern as solar panels are like big sails. They catch a lot of wind.
Dual Axis Solar Tracking
A dual axis solar tracker allows movement along the horizontal and vertical axes. This is optimum to generate the most power from a panel. If you can keep the panel facing directly at the sun, the maximum power will be produced.
I read a lot of Internet websites on this subject, and watched a lot of videos of various solar tracking installations. I had to consider what I was capable of doing myself with the tools and material available to me. One thing I do not have, and am not trained for, is welding. Ideally, mounting something on the roof of my bus would be best done by welding it there. I can hire someone to do the welding, but I also wanted to consider if there was anything I could bolt up to the roof. My bus is now 42 years old (manufactured in 1972), and it has a steel roof. It is actually a double layer steel roof with a 2" space between layers, and the space is insulated. It is much more solid than most new motorhomes or travel trailers. I do not have any concern at all about damaging the roof by walking on it.
After considerable consideration, I decided to try mounting the panels using a small 2' tripod, the kind used to position satellite dishes on the ridge of a roof. My design also included using a satellite dish motor to turn the solar panel to keep it aligned with the sun. Below is a video of an implementation of a similar design.
Following is an image of one of the tripod mounts on the roof of my bus.
You can see on the back of the bus roof there is a platform covered by a tarp. The previous owners had used the bus to go to NASCAR races in Atlanta. They would park in the field in the center area of the track and climb up on the roof with their folding chairs and watch the cars go around. I use the area for storage, and cover it with a tarp. My plan was to set four tripod mounts on the roof between the cargo area and the panels at the front of the bus, and have the solar panels rotate on the mounts.
The image above shows a close-up of how the mounts would attach to the roof. I also purchased a pole mount to provide a fourth mounting point at the very center. This would add much more rigidity to the mounting system.
Before putting any holes in the roof of my bus, or welding anything to it, I decided it would be best to assemble one of the panels to the tripod and satellite dish motor and see how sturdy it would be. I was concerned that wind load on the panels might be a problem. If this set-up did not appear to be rock solid, I did not want to risk using it for my panels. One drawback to this design is that the panels could not easily be flatted (placed in a horizontal position) to minimize wind effect. Also, the panels would have to be dismounted and placed in my trailer whenever I drove the bus. Despite these drawbacks, because this design seemed “doable,” being within my capabilities and something I could accomplish with the tools I had on hand, I wanted to give it a try.
First, I removed the framing I had been using on one of the panels when I set it on the ground, and I fabricated a new frame incorporating a pole mount I purchased on Ebay. The pole mount is adjustable, made specifically for solar panels. It allows the panel to be positioned at an angle with the sun.
I then assembled the tripod base using a 1-3/8" fence pole. The pole was not as thick as I would have liked it to be. It tended to deform when I clamped it down tightly to the tripod and to the satellite motor mounts. To keep the pole from bending inward, I ran a piece of wood doweling of the same diameter down into the pole.
Tripod with Satellite Dish Motor and Solar Panel Mount Installed
I then screwed the base down to the 3/4" sheet of marine plywood you can see it resting upon. Champ apologizes for the dirt. This is inside his kennel and I have not yet been able to train him to sweep his floor when he gets it dirty. The final step was to mount the solar panel to the base.
I was very happy with the way it looked. As far as Rube Goldberg contraptions go, it was pretty exotic looking. The mount itself was very sturdy. Nevertheless, when I applied pressure to either side of the solar panel, there was significant movement from side to side. The weak point in the set-up was the satellite dish motor. The neck of the satellite dish motor is not held taut enough by the motor. This was the largest satellite dish motor I could find at a reasonable price, and it failed the strength test. It is designed to hold 3' diameter satellite dishes, but the solar panel is considerably larger.
For those wondering how this design would have been used to track with the sun, the satellite dish motor connects to a control box that is operated with a remote. By purchasing a universal remote with a timing feature, the control box could be activated at specified time intervals to move the panel to a preset position. Since it was all set to a timer, by inputting the correct times and positions, the panel would automatically track with the sun. No sun position sensor is needed with this design.
Any mounting design that utilizes only a single attachment point in the center of the panel is going to be inherently weaker than a design that uses two or more attachment points. The entire weight and wind load on the panel is borne by the single attachment point. This necessitates that all materials must be very strong and rigid. The materials I was using, particularly the satellite motor, proved to be inadequate.
Observing some of the shortcomings of this design before I had even assembled it, I thought it a good idea to reach out to a brother in Christ who has far more experience in fabrication and design of mechanical things than I do. This brother lives in Idaho, so unfortunately I could not drive my bus over to his house and ask for his assistance. We are separated by about 3,000 miles and the tallest mountain range in America, the Rocky Mountains. My bus does not have a strong enough motor to climb mountains, and it gets only 4-5 mpg which makes the cost of long cross country travel prohibitive. Yahweh evidently did not foresee any need for me to drive the bus out of state when He directed me to purchase it. It remains a Georgia vehicle, having traveled only within the state.
Jeff proved to be very eager to help me out. After some exchanges of information, he quickly came up with some ideas that are far better than my attempts. I had told Jeff that another option I had considered was to use the four tripods and pole mounts to form a large rectangle frame that would be positioned just forward of the cargo area and go above the air conditioner on the roof. Using the same fence poles I could construct a rectangular frame approximately 8'-10" x 4'-10" (the dimensions of the four solar panels laid side by side), and create some type of giant lazy susan affair that they could rotate on. Following is an image showing how the panels might be mounted in this arrangement.
Imagine this sitting on a rotating base, and you have an idea of what I had in mind. My main concern again was the strength of the frame and the sturdiness of the rotating assembly under a wind load. My plan was to use some wood in the construction, as I am better able to work with wood, and have the tools for it, but Jeff rightly stated that steel construction is much stronger.
Sometimes it takes a fresh pair of eyes to see possibilities that we overlook. Jeff asked me what the dimensions of the cargo area at the rear of the bus were. When I measured I found that it was slightly larger than the solar panels and would serve very well as a position to locate them.
When I first began living in the bus I had a small 8' x 5' trailer I was pulling behind it. It was a short trailer than you had to stoop to enter. I could not carry much in the trailer, so it was very handy having the cargo area atop the bus to put things I did not need frequent access to. Back on 2012 I purchased a much larger trailer, and the cargo area atop the bus was not needed as much. Half of the storage containers on the bus roof were empty. When I took everything down off the bus roof and discarded what was not essential, I found I could move what remained to the trailer. Since I had moved the solar panels out of the trailer, and would not be needing to put them back as they would be permanently mounted on the roof, I had plenty of space in the trailer.
The platform at the back of the bus roof is steel construction, and very solid. It is far better than anything I could have come up with for a mounting base. Jeff had his daughter Kristine draw an illustration of his solar mount design to show me what he had in mind. It uses a trailer axle stub as the central piece upon which a steel frame will be bolted to hold the panels. Following is a picture of my cargo platform on the bus roof.
It needs a good wash. The small cultivator laying there had not yet been removed. The platform is welded to the bus roof along all the edges. The corrugated steel decking is welded to the edges of the platform frame. Consequently, the decking does have a little springiness in the center. Some additional steel may need to be welded atop the corrugated deck to make it a little firmer. Following is an image of Jeff’s design. It reminds me a bit of one of those hand sketched Leonardo DaVinci designs.
Pictured is a 12" x 12" steel plate at the base. At the center of the plate is a pipe standing on end with a screw jack inside. You can see a handle for the screw jack extending out to the rear of the bus. This will be used to raise and lower the solar panels. In the lowered position the solar panels can be covered with the tarp that I have been using over the cargo area, protecting them when traveling, or in the event of inclement weather. Another pipe would fit over the first pipe, with the axle shaft welded to it. This allows for the axle to rotate. Pieces of angle iron would be bolted to the studs on the axle. Jeff suggested using a scissor jack to raise and lower the panels, inclining them to face the sun, but I may opt to use a linear actuator for this instead.
I know this isn’t the normal type of thing I write about, so some of my readers will be wondering what a linear actuator is. Following is a picture of one.
The linear actuator is the unit with the electric cord running into it. It is pictured attached to a base at the bottom. The actuator has a shaft that goes in and out. In the installation pictured above, as the shaft extends the pole it is attached to is pushed over at an angle. As the shaft is retracted the pole is pulled back into an upright position. Linear actuators are used in most professional solar panel trackers.
Eco-Worthy is one company that sells solar trackers. You can purchase the electronics separately from the linear actuators, or purchase them together in a package. A dual axis solar tracker with actuators is under $300. It will handle all the motion in a solar array. After the sun has set in the evening, the electronics of the solar tracking system directs the panels to lay flat in the horizontal position. This protects them from winds that may arise at night. In the morning when the sun rises, the light hitting the sensor initiates tracking once more and the panels will raise themselves into the correct position.
In the design Jeff came up with, one linear actuator would attach to the pipe near the base and would control the horizontal rotation of the panels. The other actuator would go where the scissor jack is pictured in the drawing.
Because I will inevitably park the bus facing different directions, multiple mounting points indexed around the base of the apparatus will need to be fitted so that the range of motion provided by the linear actuator will always be adequate to track from east to west. This is the plan at the moment. I will provide an update once it is fabricated and installed.
Coming up with a functional design that adequately meets the needs of my solar auxiliary power system has required some perseverance and patience. It has required that I research the subject, and educate myself in it. As Christians our lives are always a mixture of spiritual and natural experiences. Yet, even in those terrestrial tasks that appear to have little relationship to spirituality, there is a need to manifest the fruit of the Spirit in our lives in order to succeed.
It would be easy to murmur and complain at every obstacle, or to bemoan every failure or setback. Tragically, this was what the Israelites did when Yahweh led them through the wilderness on their journey from Egypt to the land of Canaan. Rather than bearing up patiently when difficulties arose, they gave into despair and yielded their tongues to speak words of complaint against Yahweh and His appointed leaders. As we follow the Lord through this life we will inevitably encounter difficulties, trials, and seemingly insurmountable problems. Yet, if we will crucify the unruly flesh with its impatience, unbelief, and impetuosity, we will find that God will help us. If we implore His help in a humble and respectful manner, He is pleased to help us.
Remember, this is the same God who expanded the mind of Solomon to have wisdom and understanding surpassing all other men. It is the same God who provided water from the rock and bread from the heavens when His people had a need. It seems a small thing to ask Yahweh to help us in carrying out the tasks that we encounter in this life. James sagely wrote, “You have not because you ask not.” One thing I have done in approaching this project is to routinely ask Yahweh to guide me and to give me understanding to know how to proceed.
Don’t fall into the error of separating your life into spiritual and natural compartments. All of life is spiritual, for we are spiritual beings created in the image and likeness of our heavenly Father. The fruits and gifts of the Spirit have application in all realms of life.
To be continued...
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