solor on canadian rockies mountain tops

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I am investigating putting solar power with battery banks on mountain top sites to power point to point wireless  internet repeaters.  We are currently using Tri-Star controllers and have our batteries configured in 24v mode.  A couple of problems I have been having is one: monitoring the batteries as the Tri-Star only has a serial out put and converting it to Ethernet isn't a go as  the app used to monitor it doesn't connect to tcpip.  I would like to have a full view of the power system - i.e. power consumption, current capacity etc.  Does anyone know of a controller with a built in ehternet port?

our second problem has been keeping our panels clear of rime (heavy frost).  We have sprayed them with wax type stuff and we are looking at making a "rear window" like defroster that would come on intermitantly (but I am sceptical)....has any one else dealt with this?  If so how?

cheers
Wade G

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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: solor on canadian rockies mountain tops

    to my knowledge there isn't any such controller as of yet.
    most let the sun do its job on the pv surface for frost. usually people ask about snow and not frost. a defroster on a pv isn't very energy conserving and can drain a good bit of power off of the battery before any sun gives it a charge, and that's if the sun appears that day so it could very well deplete the battery and ruin it. higher angles with respect to the ground allow snowfall to slide off more readilly. i would refrain from putting coatings onto the pv as this could reduce its ability to generate electricity. now if this frost is turning into ice layers you may have a major problem because i develope ice in and around my downspouts and i can tell you it surprised me how much heat is actually needed to melt even a tiny bit of that ice. snow is much easer in melting and it usually slides off of the pv when the sun heats up the pv enough.
  • System2
    System2 Posts: 6,290 admin
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    Re: solor on canadian rockies mountain tops

    Click on some of these links. Might be what you want, you can see if you are putting out power or not and even the panel temp.. what ever you want I'm sure it is there for a price. Just tossing it out there. You can always send the data loger data from one pc to the other or just ftp it from a pc at the site if there is internet there.. Sounds like there is. Do a google or yahoo search and you will find a good list.


    http://www.sunviewer.net/

    http://view2.fatspaniel.net/FST/Portal/

    http://www.akeena.net/solar_electric_systems/monitoring.html
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
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    Re: solor on canadian rockies mountain tops

    From Morningstar's website FAQ's:

    - Can I connect to the TriStar from a remote location?
    Yes. We have tested certain serial to Ethernet converters as well as wireless/cellular modems. The method of communication must not conflict w/ Modbus timing requirements. Refer to the TriStar Applications Guide for different remote communications schemes.

    Here's a link to the TriStar application guide.

    HTH,
    Jim / crewzer
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: solor on canadian rockies mountain tops

    at least that's half of their problems answered. what do you think of an ice buildup problem jim. i know they just said frost which is a thin layer of ice, but if that's all there is it's not a problem. continual build of frost or ice is a problem and using power to melt it is a contradiction in power management as it may need all the power the pv produces(and it may need even more) to rid itself of this ice.
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
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    Re: solor on canadian rockies mountain tops

    Considering the northern latitude (~50 degrees?), I'd recommend that Wade install his south-facing PV modules at a tilt of between 65- and 70 degrees from horizontal. This attitude should provide for good general winter performance, and should help with de-icing as well. He could also try a steeper angle, but that might unacceptably reduce summer performance.

    Another possibility might be to install a smaller module, under the current unit(s), in a near vertical (75 degrees?) configuration. The upper module(s) would shelter the lower one from snow, ice and some frost, and the lower one may provide power if the upper unit(s) is (are) covered in snow / ice / frost.

    HTH,
    Jim / crewzer

  • System2
    System2 Posts: 6,290 admin
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    Re: solor on canadian rockies mountain tops

    Mountaintops in the Canadian Rockies? I'm thinking that temps of -40 or -50 F may be pretty hard on the batteries. Not only does it reduce battery capacity (drastically), but at those temps a lead-acid battery will freeze and break unless it is kept near full charge.

    Bill
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
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    Re: solor on canadian rockies mountain tops

    Reasonable concerns. Here's a link to SOC vs freezing point information, and this graph from NAWS' site indicates that a battery at -40 degrees (F or C) can supply but ~30% or nominal capacity.

    HTH,
    Jim / crewzer
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: solor on canadian rockies mountain tops

    you're right bill, it is a big challenge all the way around. i tried helping one guy here on the forum and via email about 1 and a half years ago in oregon. i'm not sure if he really got it the way he wanted it due to the challenges being so overwhelming and expensive. last check was no he didn't about last summer. to those with systems in weekend cottages or cabins it is nearly as difficult because of similar problems. loads are different for the cottages and cabins as they don't need a 24/7 load and that's saving on the system some and the costs. just coming up with a steady power to go 24/7 is really tough as was in a post recently who needed a constant 50w. you wouldn't think on the surface that the small power loads would be that difficult, but in a 24/7 configuration once laid out it shows itself.
  • System2
    System2 Posts: 6,290 admin
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    Re: solor on canadian rockies mountain tops

    I am trying to work out a solar power system to power up a similar wireless device like what Wade Graham is having here, but I am using a Morningstar ProStar charge controller and connecting the power input of my wireless device to the LOAD output of the controller. The system is configured at 24V nominal system voltage on the battery bank, PV panels and the controller, as the power input of my wireless device is specified as 24V(DC) by the manufacturer.

    I also intend to connect the LOAD output of the controller to a switching relay as well (for some other load switching on/off control purposes with the relay). So I searched for a 24VDC (on coil side) switching relay, which I thought should be available; the relay needs to be a DC coil AC switching relay, 24VDC on coil side for switching a separate AC power line.

    While finding the relay, all that i can find so far are having the coils taking 24VDC (nom.) at a range of from ~21.6V to a max. 26.4V only (as specified by the relay manufactures in my searches).

    And then I got to know the followings about the controller :

    1. The LOAD output from the ProStar (and even the TriStar too??? Mr Graham..) controllers is not regulated and is the same as battery voltage
    2. In a 24V system, the LOAD voltage may at times be 30V+ depending on the battery type
    3. The LOAD voltage is about the same as BATTERY voltage (minus a slight voltage drop), so as the BATTERY rises and falls on voltage, so does the LOAD voltage too

    That means I will not get a stabilized 24VDC at all times supplying from the LOAD output of the solar controller in my solar power system.

    So I hope any of you can offer some advice regarding this relay input voltage (range) problem, and also whether or what/whose made relay as required will be able to take in such varying supply voltages (from the solar system) throughout the day and night operation (battery charging/discharging) of the solar system (in which its output comes through from the LOAD end of the controller), without any problem...yeah, if possible, and if not possible, what are the problems and is there any economical solution (as I don't hope to add much cost into the solar system when the relay is to be connected to the LOAD output of the controller).

    Now, come back to my 24V(DC) wireless device, it seems a bigger problem on the solar system output with large varying voltages from 24V nominal.

    Studying from the ProStar manual, as I am trying to figure out what could be the exact voltages output then and see it as follows (please correct me):

    As I use AGM sealed LA battery for the solar system and since the LOAD output of the (24V nominal) ProStar controllers follows or is the same as battery voltage, then I suppose the LOAD output supplies varying voltages of 22.8V (LVD voltage) to 28.7V (25-day cycle equalization voltage), during the day and night operation (battery charging/discharging) of the solar system, to my rated nom. 24V(DC) wireless device or load.

    Is "the LOAD output supplies varying voltages of 22.8V (LVD voltage) to 28.7V (25-day cycle equalization voltage)" correct?  (Ignoring the slight voltage drop)

    Another word, are the varying voltages of the LOAD output the same as battery voltage changes as per the charging voltages at the bulk/PWM/float/equalization stages?

    Is this correct too?

    As ProStar has HVD protections too: on battery at 30.4V (HVD on solar) and 30.6V (HVD on load), does this mean that ProStar will never exceed 28.7V?
    (However, should this be incorrect and it will exceed 28.7V, then do the varying voltages of the LOAD output become 22.8V-LVD to 30.4V-HVD)?

    And also, hopefully any of you can give me an insight or advice too on such large varying voltages to power up my 24V(DC) wireless/modem/IT devices.

    Understand that if my load (like the wireless device) requires a specific voltage window to operate, I should consider a DC-DC converter which will provide a regulated DC voltage to my load, protecting from high voltages. However, I have searched around, including those converters from www.solarconverters.com, don't have one that really regulate the solar system output voltages (anyway, is it 22.8-28.7V, 22.8-30.4V, or what???, ignoring the slight voltage drop from the controller BATTERY end to the controller OUTPUT end, which is 0.12V max. according to the ProStar spec sheet) to a stabilized 24VDC within a controlled or regulated voltage range, typically +/-10% or +/-5% of the 24V nominal, for my 24V(DC) wireless/modem/IT devices or even for the 24V(DC) coil AC switching relay that I need.

    Since it seems difficult to find one such DC voltage regulator, does that mean that most DC loads, including that wireless device i have, can take in such large varying solar system output voltages? For this doubt, may I know what's Mr Wade Graham experience and solution if it is a problem to him as well; and anyone knows about this too?

    Hope you guys all do help me out, as I need to know some exact answers to the above...Thank you very much to any of you offering helps or views.

    Regards,
    SolarFish
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
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    Re: solor on canadian rockies mountain tops

    The ProStar and TriStar charge controllers are just that: charge controllers. Their primary purpose is to regulate charging voltage and current from a PV array to a battery, which in a nominal 12 V system could range anywhere from 10.5 V (for discharged battery under load) to 15.5 V or so for charging a cold battery. Nominal charging voltage for a 12 V battery at 77 degrees F is 14.4 V. Low voltage disconnects (LVD’s) and high voltage disconnects (HVD's) serve to protect the battery and/or the loads. In general, though, neither lead-acid batteries nor charge controllers are intended to function as regulated power supplies.

    I think you’re on to something with the DC-DC converter idea. Instead of a 24 VDC-to-24 VDC converter, a more readily available solution might be a 12 VDC-to-24 VDC converter. Such a device would allow you to configure your PV array, controller and battery in a 12 V configuration, and then use it as an unregulated source for the DC-DC converter to power your 24 V loads. The input range for this particular unit is ~10.5 V to ~15.5 V, depending on the model. You could perhaps add a primitive zener diode regulator to the input to protect it from high charging voltages (i.e., flooded-cell battery equalization or cold ambient temperatures) -- or perhaps just a big ol' diode in series with the input and just live with the ~0.7 V drop.

    This unit appears to be able to take any nominal 12 V or nominal 24 V source and convert it to regulated 24 V.

    Don’t forget to install an anti-kickback diode across the relay coil winding.

    HTH,
    Jim / crewzer
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: solor on canadian rockies mountain tops

    jim,
    my hat's off to you on finding a converter such as that. if his loads aren't greater than the capacity of the converter (100va, more specifically 5.2amps at 24v+/- 1%) then his problems are solved. jim is correct in his telling you that controllers are not meant to be regulated power supplies although they do regulate to some extent, but are meant to recharge lead acid type batteries. if your loads are greater than the capacity of that converter i would search out that company to see if they offer another that suits you or write them to see if they would engineer such a converter to meet your needs. your equipment is looking for and is speced for a regulated supply and this is what you must give it and if a dc to dc converter fits that bill that's great in simplifying a solution to an otherwise perplexing circumstance.
  • System2
    System2 Posts: 6,290 admin
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    Re: solor on canadian rockies mountain tops

    There are DC to DC type converter bricks that are widely used in the electronics industry... You can look for prepackaged ones from places like (have not used this company--maybe good or not...):

    http://www.majorpower.com/dctodc/

    Here is a company that makes very small, sealed, high reliability, high eff. power bricks. I have used these before in Telcom applications (years ago). Weren't cheap--but they did what they claimed. They do semi-custom work and can do smaller runs if you need a custom input/output configuration:

    http://www.vicr.com/

    Just as an FYI--From my experience a few years ago--a cheap medium sized power supply (AC to DC, DC to DC) will cost from $0.50 (wholesale/cheap) to around $1.00 per watt (retail or higher-rel). The DC to DC bricks can cost you a lot more.

    If you will need 1,000's of them, it may make sense to design/out-source a custom design. If you only need a few--then bite the bullet and just purchase an off-the-shelf type unit for your needs (at $$$ retail).

    -Bill
  • System2
    System2 Posts: 6,290 admin
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    Re: solor on canadian rockies mountain tops

    Really very sorry for so late getting back guys, Jim, Niel and Bill...thanks a lot for your information, advise and help.

    That time I saw the replies from you guys I went to research almost all of them..the converters..and then one thing led to another...later on I got so tied up by many technical issues.. Anyway finally now able to relax a bit back here.

    Well in between..Jim, I found the converter you recommended is great! So I am using the 24V-24V converter to
    regulate my solar power output to wireless devices...yeah, such devices do really take a very small range of voltage input only....(tested it and found this so), so then the 24V-24V converter regulator is able to do it at +/- 1%...and the mfr support to me is prompt, direct and good...so the problem solved..yeah..really appreciate that.

    As for 12V-24V, it is not favourable as 12V system is not efficient enough to me...so can't make it 12V for using the 12V-24V converter.

    The next thing from here puzzling me is about the Primitive Zener Diode Regulator, "big ol' diode" and anti-kickback
    diode...as I don't have much knowledge about diode, its applications, actual way of circuit wiring and where/how to get the diode which is right for my circuit in terms of its rating, spec and/or size, contact leads and others...of selecting a right one from somewhere a mfr list. So you can see...that's a problem..although generally I can understand the function you mentioned about putting a diode there or somewhere else will make my system better and work reliably. So what are they..the diodes for solar system use? How they look like? How many contact leads they have? And how to specify its rating, spec and size and then I would need to look for a source or supplier of the spec chosen..yeah...please enlighten somehow, I think it should be a simple electronic item to you guys..

    And Niel, thanks, that 24V-24V is good enough for my devices...because these devices mainly are small power
    items, so 100W of it work enough for them. I mean so far I have not come to need a bigger capacity than that yet.

    By the way, these converters do add some significant cost there, but then think I have got no other choice..

    BB, thanks too to your recommendations...I did contact them to inquire. But then their support was not good
    to me, or just no reply..and also there are some techincal issue like...their heat derating is a bit of problem..
    Oh yeah, the converter seems small..but the price they told me is not cheap...more expensive than that of Jim's.

    Hm...working hard still on some of these here, and hope to hear from you guys again on some of above..hoping..

    cheers!
    SolarFish
  • Roderick
    Roderick Solar Expert Posts: 253 ✭✭
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    Re: solor on canadian rockies mountain tops

    If the power requirements are not extreme, you might want to consider some of the Lithium chemistries for your batteries. Rose Electronics has been helpful to me in the past with this sort of thing.

    I hear that some of the novel Lithium electrolytes are good to -100 C (yes, Celsius), but if you need a lot of power, the cost would be prohibitve.

    Then again, you might heat a highly insulated battery compartment for less money. Maybe even the natural power dissipation of the electonics would be enough.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,502 admin
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    Re: solor on canadian rockies mountain tops

    The "Kick Back Diode" is also called a snubbing diode on a coil/inductor... Basically, the warning is the if you are controlling a relay with some sort of electronic switch (transistor, FET, etc.), when you try and quickly stop the current flow, the relay's coil's field will collapse and try to keep the current flowing (and generate 100's of volts--depending on the size of the coil and such)...

    Basically, one method to prevent this is to place a simple diode (propertly rated) across the coil terminals (in parallel with the coil), and opposite to the control voltage (blocking).... So, coil is energized, current flows through coil while diode blocks current. Coil is de-energized, the coil tries to keep current flowing as the field collapses--the diode is now forward biased and the energy is safely dissipated instead of impressing a high voltage across the Transistor/FET switch.
    (+) positive (Cathode connection to Diode)
    -------+---------|
         |      |0
       __|__    |0
         /\     |0 (Relay Coil)
        / \     |0
         |       |
    -------+----------|
    (-) negative
    
    

    The Zener or simple drop diode was a suggestion to put this in series with the "battery" (i.e., positive cable) to power converter connection. Diodes have between 0.2, 0.7, and higher voltage drops available and the suggestion is that you can fractionally drop the high battery voltage down to a save level for the power supply...

    This will work, but does this with the drawback of inserting a P=V*I voltage drop which is just burning power has heat (no useful work). Can work fine if power available is high, not recommended if you are trying to conserve power (example, 1 volt diode drop at 2 amps = 2 watts of loss power). Also, if you place a diode in series with the power supply, you should also include a couple of capacitors before the power supply--the diode is a non-linear resistive element and can cause nasty harmonic oscillations on the power supply input (usually a couple sizes of caps, a smaller radio frequency cap (0.01 uF) and a larger bulk cap for lower frequencies (couple ~10's of uF).

    The Series Drop Diode can work--and you could place a relay in parallel to only insert the drop when float charging the batteries (NC relay, closed when voltage is normal/low, energized open when volrage is high and needs to be dropped).

    In either case, it would be better, if you can, to find/design a supply that accepts the range of input voltages you need.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: solor on canadian rockies mountain tops

    bb,
    thought i'd clarify that a zener is not a series drop diode. zeners are regulation diodes and they could be used in low power fixed output circumstances somewhat easily, but this is paralleled to ground and uses a fixed resistor in series from the unregulated power to the + of the zener diode to stop overcurrent to the diode and load.
    a series drop diode would be a standard diode at the rated current value seriesed inline to drop roughly 1/2 volt per diode passed and can range in voltages dropped as you stated depending on the diode.
    i know you know the difference bb, but the way it's stated it could mislead people that they are the same. i also will say that if you don't have any knowledge of building regulator circuits that you should be cautious in trying this without the help of somebody that knows what they are doing.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,502 admin
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    Re: solor on canadian rockies mountain tops

    Hi Niel,

    Actually, I did really intend to say series drop heat-sinked Zener (this would assume that you are looking for several volts or more of series drop). Either 6 plain diodes or one 3 volt Zener (I would have to check to see if Zener diodes work at this low of voltage) would work about the same (assuming that the current and heat dissipation are met).

    Using a Zener as a shunt regulator (resistor feed to the Zener--connected to ground) would only really work as a voltage reference. Trying to pass any power this way would be highly inefficient.

    Using a three terminal regulator (with band gap reference) would probably be even better for most applications (the Three T Regulators can be made adjustable, handle more power, and waste less power than a typical Zener shunt regulator).

    In the end we are probably quibbling here--the real answer is switch mode power supplies design for the application. Anything else is probably a kludge of limited help in this application. Any Three T or other type of non-switching regulator usually wastes more power than it passes (50% or less efficiency). Energy that you don't want to waste in Solar.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: solor on canadian rockies mountain tops

    i too like the 3 terminal regulators, but it's no pwm for sure. as to the zeners passing power in series, well this is possible but not wise to do. the zeners can only handle small amounts of power and to make matters worse is that it passes anything over the voltage rating of that zener when in series. if say you have a 12v zener being fed with 36v in series, the voltage after the zener would be 36-12=24v at the output and would be limited depending on the wattage rating of the zener or risk blowing the zener like a fuse. now if the input voltage to that zener was 11v then the output voltage is 0v as it is below the avalanche point of the diode which is 12v. at 13v input the output is 1v so this is just subtracting the voltage rating of the diode, but leaves the output still unregulated and doesn't solve the problem as lower voltages that would normally be able to pass now won't because the diodes subtracted from that too. a regulator is needed and not a dropping diode. regular diodes used for dropping diodes seem better to me than zeners as they go by current rating and not wattage rating and thusly handle much more power than zeners and are cheaper than high power zeners. the trouble is you'd need to utilize too many of them in a circuit. do i hear 25 pack from radio shack for 3-4 dollars :? :?
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
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    Re: solor on canadian rockies mountain tops

    You guys saved me a lot of typing... Thanks! :-)
  • System2
    System2 Posts: 6,290 admin
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    Re: solor on canadian rockies mountain tops

    Hm...thanks guys, well some of these diode stuff need some time for me to absorb though...ha..studying them now. Anyway diodes, diodes..mmm...guess I should need to master them as well for making solar power works..

    SolarFish