Monitoring system

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Soulbringer
Soulbringer Registered Users Posts: 17 ✭
in Advanced Solar Electric Technical Forum #1
Hello guys,

I don`t know if somenone can help me but I will try to explain:

I want to install small PV system 700W but only for monitoring purposes (solar irradiation,wind speed, module temperature and produced energy). So the site where i want to install this system don`t have an electricity connecton. The first thing I want to ask:
Do I have to buy off grid inverter. Because I have one on grid inverter (SMA Sunnyboy 700) but I know that it works only if we have load.
So my idea is to connect my Web Box and SensorBox to Sunnyboy 700 and to use them as a load. Do you think it`s possible to measure the produced energy and solar irradiation in that case. Thanks to all
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #2
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    Re: Monitoring system

    A true grid tie inverter needs the utility mains to even turn on and generate power. Without the mains, the Grid Tied inverter will just sit there an do nothing--regardless of any connected load.

    You will need to get a regular inverter (or use a DC input power supply) to run your equipment.

    Also, you may wish to purchase a battery powered weather station and download the data to a very small PC/laptop DC powered system... A 700 watt system is pretty small and a continuously operating PC (example a small laptop) can still consume 20 watts x 24 hours = 480 Watt*Hours. Your system would may only generate an average of 4 hours of sun * 700 watts * 54% over system efficiency = 1,512 Watt*Hours... (54% equals panel derating, battery losses, charge controller losses, AC inverter losses).

    Only to see your monitoring system take about 1/3 of your overall available system power...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Soulbringer
    Soulbringer Registered Users Posts: 17 ✭
    #3
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    Re: Monitoring system

    Thank you Bill.

    May be it will be better to find a pyranometer which can be installed on a field where there is no electriciry and can be powered by solar cells integrated in it. What do you think?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #4
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    Re: Monitoring system

    Why/where do you want to measure solar energy? And how how accurate do you want the measurements to be...

    Realistically, a true pyranometer will have accuracies down to 1-2% (probably towards +/-5% if not cleaned often--and you will still need to get/build a data logger for it), where a typical weather station/data recorder will be in the +/- 10% range.

    If this is a "remote monitoring package" then your idea is fine (except you will have to either use a true inverter, rather than the SunnyBoy Grid Tie, or get a DC power supply for your computer), or look for a low power system / data logger and you can reduce power usage/solar system size.

    Something like this only consumes 2 watts from a battery bank... Or look for other embedded computer options...

    There are also companies that have created complete systems (used by state agencies and such)...

    Really all depends on your requirements... While solar power (or wind, etc.) can be a big help--there are times of bad weather where you may go a week or more without significant sun--so having a system that uses very low power in the first place makes it much easier to power with a reasonably sized battery during those times (and avoid needing a backup generator of some type). Having the ability to "sleep" during the night will also save about 1/2 your power requirements.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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