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When a gas warms up, the product of pressure and temperature increases. This can be used to build a system that keeps solar collectors or solar panels
directed at the sun.
A gas container is set up so that the heat from the sun warms up the gas, more if the container or a system surrounding it
has a certain orientation with regards to the sun. The pressure in this container is used with a pneumatic actuator that moves both our control container and the device that we want to control, into a direction that brings the container out of the sun and the device being controlled into the sun.
There is an antagonist, a opposite system, that is sensitive to sunlight coming from a direction across the centerline of our solar panel The balance between the pressures from the two gas containers is what causes the system to track the sun. If the sun is the east, the gas container on the east warms up and pulls the device to the east. As the sun moves to the west, the western container warms up more then the eastern and moves the (solar panel/solar collector) to the west.
A third and fourth actuator control up/down direction.
Implentation could be rubber bladders (oh no) or gas cylinders with pistons.
Gearing and power available could be adjusted by picking a gas with large expansion (possibly a refrigerant), size of container, length and diameter of piston, distance from pivoting point and possibly concentrating the sunlight.
Track Rack Passive Solar Tracker for Photovoltaic Modules
http://www.emarinei...mounts/tracker.html
[half, Jul 12 2006]
Mother Earth Tracking System
http://www.motherea...lar_Tracking_System
[jmvw, Jul 17 2006]
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The movement of the sun given global position is entirely predictable through algorithm. Why not just use a small solar-powered motor to move the solar collector in accordance with the algorithm. That way, it's 100% correct, all the time. |
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Why? Not sure. Durability, perhaps. I think my system could have a longer mtbf then a system that relies on electric motors, solar cells and a microcontroller. I think of it as an alternative to what you're describing. |
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Why dont you just hook up a bungee cord to the sun and it will pull the dish as it moves? |
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Too much inherent error in a bungee cord. A chain of zipties would be more stable. |
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//gas with large expansion// Surely only a gas that undergoes a chemical change such that the number of molecules increases with temperature will have a larger thermal expansion than an ideal gas. |
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There was an article in Earth Garden or similar that did a cost-benefit analysis of tracking for photovoltaic panels, and concluded that in most cases you would be better off just adding extra panels rather than a tracking system to get the equivalent power increase. However, there might be room for a low cost, low precision system such as this one; most of the potential gains from tracking would be achieved without high precision. |
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I've seen a slightly different form of passive tracking in use. No actuators needed. (link) |
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[half] Neat, ether duck trackers. Don't those blow about in the wind, though? |
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//If the sun is the east, the gas
container on the east // "if the wind's
to the east, aim to the west.... he leans
to the right, so shoot to the left" or
similar - dialogue from "The
Paleface" - Bob Hope et all. Sorry
couldn't resist. |
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Idea sounds suitably daft to attract my
best wishes and this +. Looking forward
to animated photographs of pulsating
bladders being pecked at by thirsty sea
gulls. |
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//relies on electric motors, solar cells and a microcontroller// Why do people imagine a tracker involves a processor of some sort? Two pairs of LDRs and a couple of amplifiers with H-bridges to drive the motors is all that's needed. Simple analogue electronics. |
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// Why do people imagine a tracker involves a processor of some sort? // Why its so we can install a Microsoft O/S on it, of course. |
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baked many (many) years ago in Mother Earth News. As others have pointed out, it isn't generally worth the hassel for PV or water heating. Perhaps for a solar oven? |
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[James Newton] I think I found the article in Mother Earth News that you mentioned. See link. The article seems to describe an electronic system similar to what [coprocephalous] described. |
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My system uses thermal expansion of gases. I think it could be valuable it if this were produced on any kind of scale. Of course, larger systems will benefit more. |
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It might be nice if we could see the cost-benefit analysis that [spidermother] mentioned. |
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No, I distinctly remember a pair of black rubber bags that inflated and deflated with the heat to track the sun. It may not have been Mother, but it was something like that. |
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It's a good idea, one way or the other, for things that really need to be focused. Not PV or heat, but solar cooking or steam. |
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I found myself thinking of this idea for some reason recently... |
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And it occured to me, why not have a hinge on the west side, and the expansive material on the east side. At night, the device will cool off, causing the material to contract. The solar pannel then tilts downward towards the east. As the sun rises, it heats the bags, and the material begins to expand. At noon, it's about level, in the afternoon, it keeps heating, and expands more, so it is raised up, and points west... |
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It'll be a little tricky to keep it pointing west during the cool of the evening, and making sure it expands slowly enough not to hide itself from the sun in the morning might be a challenge, but I don't think it's anything a big enough heat sink couldn't handle... |
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The storage chamber goes on the opposite side from the actuator. |
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When the panel is square on to the sun, both storage chambers are fully shaded by it. If the sun is to one side of the panel, the tank on that side is exposed. This causes the actuator on the opposite side to expand, pushing the panel up on that side. There will be both lag and oscillation in the system, but having a tank with a large heat dumping capacity (fins away from the sun) and a relatively small volume to surface area (long skinny cylinder) should minimize those. |
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Probably still better off with a motor, since it will provide more reliable results. |
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Jmvw, ideas like this are why I still enjoy tis site! |
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