Mechanically Steered Sterling Solar Array

Steven Lake
Steven Lake Solar Expert Posts: 402 ✭✭
in General Solar Power Topics #1
Well, I've got a new one for you guys that sounds plausible (it's another one of those "heard it from a friend" things that sounds real enough to be true) which I thought you'd find interesting. Anyhow, a local engineer (not sure if it's the same guy with the wind hydro power system or not) apparently built a working prototype mechanically controlled sterling solar array. But here's the kicker. It doesn't use a single lick of electronics. It's all mechanical, including the power regulation and steering systems.

Apparently someone came up to him and said, "All this solar and wind stuff is great, but what happens if a CME/EMP hits it? Won't you be screwed because all the electronics are fried?" So, apparently his solution to that was to build a sterling engine, then build a control system for it using all mechanical switches and other things that wouldn't be affected by large current spikes.

So how does this thing work? Well, if I understand what I was told correctly, sunlight is concentrated using a special lens (I think it was using a fresnel lens, but I'm not sure) onto the center of the sterling engine. As the sun moves, the beam drifts off center and onto a bunch of thermal buttons (it sounds like he was describing some kind of small peltier plates) which heat up and trip switches that move the array back to center by activating several attitude control motors. (at least that's how I remember it. Forgive me if this is confusing, as I'm going by memory here, and given my age, that's a challenge. lol)

Now I didn't find out how he gets it back on center in the morning, but there may be something in the design that resets it for the next day once the sun goes down, or he may have to reset it manually. Not sure. But if it's real, it sounds very interesting. A completely EMP/CME proof system that's mechanically controlled and driven. Now how cool is that? :D Anyhow, thought I'd share.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Mechanically Steered Sterling Solar Array

    Zomeworks trackers don't use electricity either: http://zomeworks.com/products/pv-trackers/introduction
    They automatically return for morning too.

    There's no reason why such pressure differentiation couldn't be use to continually realign the lens to focus the sun on the collector.
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #3
    Re: Mechanically Steered Sterling Solar Array

    Hi Steven,

    I believe Zomeworks trackers use the heat of the sun acting on a collector plates to create the motive force to track the sun. THink it uses a fluid/gas cycle. My description is not very clear, as I have not studied the process, but uses no electronics, but needs shock absorbers to limit the effects of high winds on the positioning of the array..

    http://zomeworks.com/products/pv-trackers

    Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    #4
    Re: Mechanically Steered Sterling Solar Array

    A completely EMP/CME proof system that's mechanically controlled and driven. Now how cool is that? Anyhow, thought I'd share.
    Sure the tracker might survive but how you avoid electronics in the chargecontroller and inverter???????????Semms like after a electrical"whipeout" the solar panels will be tracking nicely but everything thay are connected to will have failed.. kinda defeats the purpose somewhat??
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #5
    Re: Mechanically Steered Sterling Solar Array

    For CME's ("solar flares"), we have had threads here before:

    Making a PV system survivable in EMP/CME conditions?

    In general, my belief/understanding is that CME's only will affect power grids/electrical systems that are on the order of miles across (minimum size)... And will not affect a home's off-grid power system.

    Nuclear EMP--You will have other problems to deal with...

    More likely, working at hardening your system against lighting strikes is a more cost effective/near term problem solution:
    BB. wrote: »
    A couple threads about Lightning:

    Off Grid Grounding Technique?
    Another Question, this time about Lightning

    Note, the above are discussions, not a do A, B, and C--and you will be "safe". There probably is no such thing with lightning. Several different techniques are discussed--and a few of those posters even have experience with lightning. :cool:

    And our host's consolidated FAQ page:

    www.windsun.com
    Lightning Protection for PV Systems

    From other past posts here, Windsun (admin/owner of NAWS), he said that most of lighting induced failures he saw were in the Inverters' AC output section.

    Towards the end of this thread is a very nice discussion of proper generator grounding.
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Mechanically Steered Sterling Solar Array

    i agree with john p for if it is strong enough to affect something as small as the tracking of the pvs, then the rest of system, being electrical, would be toast. i'm not going to say that the sun couldn't ever produce something large enough to fry smaller things, but we have enough troubles trying to keep the more common lightning from frying our stuff rather than planning for a catastrophic event like nuclear. remember, the sun is nuclear.:roll::D
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  • Steven Lake
    Steven Lake Solar Expert Posts: 402 ✭✭
    #7
    Re: Mechanically Steered Sterling Solar Array

    JohnP, for a solar array vs emp/cme, yeah, I can easily see a mechanical turning system being pointless. Now a Sterling solar system, that'd be a whole other thing.

    Cariboocoot, Vic, those are kinda neat. I don't know if he modeled his system after that, but if I ever find out, I'll let you know. That's kinda neat. :D

    Neil, I'm pretty sure his system uses something similar to what this guy used for his wind turbine. (the control box is 3/4 of the way down the page) Now as for how you'd make a mechanical charge controller, that's actually not that hard, believe it or not. :D

    All you need are a couple relays designed to trigger at certain voltages, a dial switch, and a low rpm dc motor attached to the switch. The idea here is, if you want the voltage to remain at 2 amps, one relay is set to 2.1 amps, the other to 1.9. If the voltage to the battery drops below 1.9, the first relay fires and turns the motor right, dialing up the voltage until it's above 1.9 amps. Then it shuts off, stopping the motor. If the voltage goes above 2.1 amps, the second fires, turning the motor left (ie, reverse current) and it dials it back to below 2.1 amps.

    I've actually had a working model of this years ago (something I did for a science experiment) and it works pretty good. I have no idea where to get the relays from anymore, nor do I have my plans anymore, but the idea is pretty simple, and should be easy enough to build. So how does it handle things when the battery is near the top, or the bottom? Eh, not well. I never figured that part out. Then again, I only needed it for a short time, so I didn't experiment that far. lol. But the fact remains that you *can* build a mechanical voltage controller.

    Oddly though, I'd be interested in seeing someone make one again. I'd be fun to see others with a bit more electrical skill really go to town on this design. :D
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #8
    Re: Mechanically Steered Sterling Solar Array

    that's wonderful if you can pull all of that off, but because the loads being powered are electrical they would be toast and you'd have electric generation without anything working to be powered.:roll:
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  • Steven Lake
    Steven Lake Solar Expert Posts: 402 ✭✭
    #9
    Re: Mechanically Steered Sterling Solar Array

    lol. Yeah, in the event of EMP/CME I don't expect anything electrical to survive. But if you could get the generator to survive, you'd prove your point. Not that it'd matter, but still, as they say in the mechanical field, "it's the principle of the thing". ;)
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  • SolarLurker
    SolarLurker Solar Expert Posts: 122 ✭✭
    #10
    Re: Mechanically Steered Sterling Solar Array

    sounds cool you should try and see it and take some pictures. I would wonder what the effciency of such a system.

    There is a company in Colorado that is trying to make a low temp sterling generator that uses evacuated tubes as the heat source. It would seem like this arrangement would be much more simple. I kind of like the prospects of the system as you could set the system to store the heat in a storage tank and siphon it off at night.
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  • Steven Lake
    Steven Lake Solar Expert Posts: 402 ✭✭
    #11
    Re: Mechanically Steered Sterling Solar Array

    Ya know, that heat storage idea does have potential. In fact, I know it'd work, because there's some solar plants out there that literally use molten sodium (or some kind of high temperature salt solution) to both run the generators during the day, and store extra heat to power them during the night. If they could do it, then I know I could too. The only issue with be the scale of it. IE, what's the minimum size required to be practical.

    One idea might be to use a heat pump. I've actually heard of places that use the idea of a heat pump to cool their buildings in the summer, and heat them in the winter with the same section of ground simply by sequestering heat underground during the hot months, and then pulling it out during the cold. Don't know if it works or not, but so far I haven't heard any negatives. So that might be one way to store heat for use overnight. I'm just not sure how it'd work when connected to a Sterling. But either way it's one possible way to store heat.
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  • snuffy
    snuffy Solar Expert Posts: 72 ✭✭✭✭
    #12
    Re: Mechanically Steered Sterling Solar Array

    I have this picture in my head of a clock driven gear that drives a slave gear. The clock gear shaft would have a cam that disengages the drive gear from the slave gear for a couple of hours or so. During the time the slave gear is disengaged it is free to move and is returned by a counter weight to a positive stop where it waits for the drive gear to re-engage it again.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,894 ✭✭✭✭✭✭
    #13
    Re: Mechanically Steered Sterling Solar Array

    Another question you should ask yourself is "do i like repairing things that are mostly mechanical or do I like repairing things that are electrical?" I have been stumped a few times in working on the Zomes and the Wattsuns are just easier for me because of my electrical background. They both fit in different types of design stategies nicely!
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • SolarLurker
    SolarLurker Solar Expert Posts: 122 ✭✭
    #14
    Re: Mechanically Steered Sterling Solar Array

    It really sounds cool, I wish I had the skills to create some of the projects some backyards tinkerers do. Unfortunately, I know just enough to be dangerous, I'm trying to learn but it's a steep curve.

    If panel prices keep falling it might just be cheaper down the road to build a half dome clad with pv.
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  • Steven Lake
    Steven Lake Solar Expert Posts: 402 ✭✭
    #15
    Re: Mechanically Steered Sterling Solar Array

    SolarLurker, I'm kinda like you. I like to tinker and see what's possible. Even if it's not practical, I still like building them to answer my typical batter of "what if" questions. I've actually come up with some pretty neat designs over the years. Again, none of them were practical, but they were all working proof of concepts. :)

    On a side note, I did find someone (and apparently there's quite a few of these guys out there, you just have to dig a bit) who actually carries a [URL="http://www.cumminsgeneratortechnologies.com/www/en/common/pdfs/download/stamford/pdfs/avr/TD_MAN-VOLT GB_09.02_01.pdf]manual voltage regulator.[/URL] It's designed to act as a backup to an automatic regulator. I don't know how surge proof this will be, but if it holds up well, you're good to go. :)
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