skystream grid tie issues

ws9876 Solar Expert Posts: 440 ✭✭✭
Regarding the Skystream... it was pointed out to me that the Skystream HAS to be connected to the grid to work,at least in standard set up. The only way around it would be to use seperate{dont know why you would need separate..) inverters and a battery bank and a complete separate power panel
in the house and any loads you want to run wired into this additional panel.
This question is for engineers or like that understand this only please.
First, why is this?Why cant I push power in to my breaker box even if it doesnt back up into the grid or get me credit.If I make the current ,then the meter wont be spinning forward as much anyway and this is a savings anyway.No? Secondly, there is an issue out there regarding the quality of power
on some rural grids and the grid tie contract saying that it will not credit power back if
there is too much of a diifference in the voltage levels between the grid and the Skystream. This might be an issue solely because of the lousy power in the grid but
the Coop might still not register the credits if this is the case.The coop might say that between 8 to 2 PM the computer said the disrepancy was out of bounds(coop at fault)
so there is no credit during that time..???
And by the way, SMA(sunny boy) makes the inverter in the Skystream....
whats up with this??? thanks


  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: skystream grid tie issues

    now this is interesting to me and seems to be a catch 22 for you. the reason you can't use it directly is because, like the solar gridtie inverter counterparts, the voltage is raised to create a differential and thusly sends power to the grid by this means. these voltages are far too high to run your ac stuff directly without being absorbed by the rest of the grid. they are saying if it is raised to do this over what they deem appropriate that they won't pay you for it. you better ask what that threshold is and how it's determined or you will (providing the skystream works at all) give them free power. this sounds like a scam/scheme for the utility not to embrace renewable energy sources and to reap without due payment the benefits of it by imposing "if, ands, or buts". contacting sma for an opinion couldn't hurt either as swwp won't know much.
    this affects all who are grid-tied regardless of the power source used and could set a precedent. all else fails then it could be the political route of contacting your state representatives.
    please followup on this and let us know what you find out.
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: skystream grid tie issues

    Before contacting anyone you need to get the data as to why your not selling energy.

    Your wind genny has to be above the voltage and minimum power requirements of the Sunnyboy and the grid has to be within UL1741 regulations ( as a guess probably 240 VDC and 20 or so watts before the Sunnyboy can sell to the grid, grid needs to be between 211-264 VAC 59.9/60.1 HZ )

    Your post has no data to determine what is happening at your site, the more details the better you can get responses that could help you understand you performance

    All grid tie inverters can only sync to the grid, they cannot by themselves be a grid. You were told correctly if you want to harvest energy from the windgenny, you have to be connected to SOME grid, be that your coop or your own inverters and battery banks

    Also you coop needs to know about your grid tie system ...

    And for Neil, its takes hundred of amps to budge a grid connection, so for home based gridtie, its a not a concern ... if your generation is above say 10kw, then most utilities require engineering to make sure the grid can handle the boost that the grid tie system can inject into the system. the theshold varies from locality/state
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: skystream grid tie issues

    hmm. i interpreted out of bounds to mean too high and didn't think of it as too low which would stop production of power to the grid. was there sufficient wind during this timeperiod? i am not that familiar with the skystream or the software being used to know for sure what this is indicating to us. is that skystreams software or the utility's for determining power delivered to the grid that is payable/credited to you? i'll sit back and let sg do the proper q and a to you.
    btw i don't think it will always take hundreds of amps to bump the voltage up a smidgeon as it is a matter of localized areas with resistance in the wires and variable loads within. when the power company here did a voltage test it was without any loads on that might drop said voltage.
  • ws9876
    ws9876 Solar Expert Posts: 440 ✭✭✭
    Re: skystream grid tie issues

    guys, there is no site yet.. let me try this again.....regarding the crediting issues( there is no actual buying at all)
    Say the grid has spikes and other quality problems. Say it goes on for 5 hours. During that time you are forcing 2kw into the grid, good winds.... Their computer says there was a discrepancy between the two power qualities at this location so we are not going to credit anything during this time. They can do this apparently and one consultant said this is happening.It was the grid quality but they cant tell who is the problem so its tough shit.
    Everything is monitored by computer and all data is sent wireless to the nearest substation
    and from there through the phone line to the office.
    I am going with a Bergey and doing a separate system completely.
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: skystream grid tie issues

    That's not how grid tie works ...

    If the inverter thinks that the grid is Outside of UL1741 conditions, it stays offline, there is no power going anywhere. As for 2kw for a Skysteam, thats not happening in this lifetime. Grid tie very common and it makes no difference if the RE source is solar or wind, its the inverter that handles the energy transfer and is constantly monitoring that the grid is within UL1741 parameters

    While its possible that your Coop has poor regulation, utility's are required to meet standards as well, but it depends on your State regulations if they are required to allow you to interconnect for selling or net metering your RE energy

    As to monitoring the grid to find WHY the grid maybe out of allowable parameters, most grid tie inverters have the ability to data log, with a Xantrex GT system for example, data logging can be done down to the 1 second interval and the data can help with hard data to whats happening, sunny boy I believe can log down to 4 second intervals.

    Grid tie is becoming very common, but is NOT in all 50 states and Utilities are NOT required to support it in all states. Selling only IS allowable in all 50 states, but only at the wholesale price level and your RE is really just treated like any other power plant, which makes NO sense for RE energy to get 2-4 cents kWhr ... if your coop doesn't support retail net meter, there is no point in being connected to sell RE to them