grid tie recommendations

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shawnbath
shawnbath Registered Users Posts: 5 ✭
in Solar Beginners Corner #1
hello, am new to solar and have been reading and reading. i am planning on purchasing a grid tie system in the 12000 - 15000 watt range. the calculators say to cover %100 of my electric i use now i need a 18000 but we a have city owned utillities (in s.e. kansas) and i dont want to feed power to them and not receive any compensation. my home is on 1.5 acres plenty of open space to not have to worry about shadding issues. anyways my question is- what are the better systems or parts to buy. solaredge has my attention but i would really like to know what some of you that have been involved in this for some time have to say. thanks for your time shawn
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #2
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    Re: grid tie recommendations

    Installed systems should run you about $4 a watt with central inverters, use micro-inverters expect another $0.50 a watt in cost. That is a large system you will need to find out about your panel capacity as you can only backfeed to 120% of the buss bar capacity in the panel. This can be achieved by derating the main breaker to get up to a 60 amp back-feed on a 200 amp panel without to much trouble if the other loads are not too large. 200amps X 120%= 240 amps. derate to 175 amp main breaker you get 25 amps for the derate and 40 amps for the buss bar rating.

    Or you can get into a situation like we had with a 12500 watt system. Permitting agency would not allow a derate of the main panel because of the existing loads. This required a $4300 upgrade to the main service entrance to 400 amps (changed all the way to the transformer) with two 200 amp breaker panels, one derated to 175 amps.

    The first thing you need to do is find out what the utility will allow for back-feeding the grid. These are called net metering plans. On our net metering plan we back-feed within out TOU time frame but those watts are not allowed to be used at night. Call the Utility first, many are doing strange things to discourage implementing grid tie systems.
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #3
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    Re: grid tie recommendations
    shawnbath wrote: »
    we a have city owned utillities (in s.e. kansas) and i dont want to feed power to them and not receive any compensation.
    If this the case a Grid Tie system is not what you want. You would need a Mini Grid or a Hybrid with a Gird Support. Grid Tie is all about selling or banking power.
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  • shawnbath
    shawnbath Registered Users Posts: 5 ✭
    #4
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    Re: grid tie recommendations

    I will be able to do the install myself and have 2 200amp services I will be able to tie into if need be. I don’t believe net metering will apply since it is a city owned utility and not an investor owned and I plan on checking into that today. I shouldn’t have said I don’t want to feed the utility. I just want to size the system where if I do feed them more than I use it will be minimal. If I have to pay a small bill to them that is fine. Any input on manufacturers?? What does everyone think about the solar edge brand?? Thanks Shawn
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #5
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    Re: grid tie recommendations

    After you check with the utility then check with the permitting department and see if they have any special requirements. Some require a AC disconnect well labeled which in turn requires a single attachment point in the electrical system. If you are roof mounting some have special requirements for the fire department roof access and for structural drawings and engineering sign off. Some go crazy with the grounding requirements.

    Sorry can't offer any advice on Solar Edge, I run central inverters.
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  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
    #6
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    Re: grid tie recommendations

    Kansas has net metering laws, which means if you connect to the grid you can zero out your bill but not "go negative" i.e. you will never receive any money from them. I would recommend going grid tied; it's a lot easier/cheaper than a battery based system. You are allowed to go as high as 25kW.

    If you have occasional blackouts I would recommend SMA inverters with a feature called "secure power" - it allows you to run off your inverter during the day when the power goes out. (No batteries so no power at night, but you can charge lanterns, laptops, run your fridge/furnace during the day etc.)
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  • shawnbath
    shawnbath Registered Users Posts: 5 ✭
    #7
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    Re: grid tie recommendations

    Thanks for your input. I live in a small town around 3000 people so the city utility people are pretty easy to get along with and are friends of mine. I already have a main disconnect under my meter at the pole so that is covered. I have some experience with robotics and logic controllers so I am planning on building my own mounting systems (ground type) that will track on a single axis. I don’t see the need to do a dual axis as I can make the mounts adjustable on the north side and just adjust them monthly. From what I have read there is energy to be gained by tracking, what do you think?? Thanks again Shawn
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  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
    #8
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    Re: grid tie recommendations
    shawnbath wrote: »
    From what I have read there is energy to be gained by tracking, what do you think?? Thanks again Shawn

    Nowadays PV's are so cheap that it makes more sense to just put more PV up rather than get a tracker. However if you just like the idea of a tracker, go for it. Zomeworks trackers work very well (aside from sometimes taking a while to reorient in the morning.)
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #9
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    Re: grid tie recommendations
    shawnbath wrote: »
    Thanks for your input. I live in a small town around 3000 people so the city utility people are pretty easy to get along with and are friends of mine. I already have a main disconnect under my meter at the pole so that is covered. I have some experience with robotics and logic controllers so I am planning on building my own mounting systems (ground type) that will track on a single axis. I don’t see the need to do a dual axis as I can make the mounts adjustable on the north side and just adjust them monthly. From what I have read there is energy to be gained by tracking, what do you think?? Thanks again Shawn
    I advise using PVWatts http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/ to run a few scenarios to see how much changing the tilt monthly on 15kW of PV will buy you; compare that to how much it will cost you to design and build a system with that capability. I assume you are talking about a ground mounted system; adjustable tilt on roof mounted systems is rarely feasible.

    When you say you have two 200A services, is that two meters or two services fed by the same meter? You'll need to do your homework with the utility to see what they allow/require with respect to interconnection before you plan your system, and study section 690 of the NEC in order to be code compliant. Your utility may require that you hire a master electrician to review your design and make the interconnection.
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  • shawnbath
    shawnbath Registered Users Posts: 5 ✭
    #10
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    Re: grid tie recommendations

    Ok thanks for the input. I talk to the city utilities this morning and they have never had anyone inquire about solar so I don’t think I will have any issues there. I have 2 good friends who are master electricians also so I got that covered if need be. I think after the input I have received I will just do a stationary setup. My wife is nervous about spending 20+ grand right off the bat so to comfort her I believe I will do this in 2 steps and then maybe a 3rd if we need it later. It is only 1 meter feeding both services. Thanks again for your input and advice Shawn
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  • DanS26
    DanS26 Solar Expert Posts: 266 ✭✭✭
    #11
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    Re: grid tie recommendations

    All good advice so far. If you are doing the work yourself, you must also be aware of voltage drop calculations, especially if you are going the micro-inverter route. Ground mounts a lot of times are located a ways from the service connections.
    23.16kW Kyocera panels; 2 Fronius 7.5kW inverters; Nyle hot water; Steffes ETS; Great Lakes RO; Generac 10kW w/ATS, TED Pro System monitoring
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #12
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    Re: grid tie recommendations

    I am still in the dark with some of your statements. If you have no intentions to feed any power into their system, what do you intend to do with your excess power ?? Do they have smart meters ?? Do they have the software to do bi-directional billing to be able to bank your output ?? It's easy to tell you to go Grid Tie, but you did not clarified your exact intentions that have changed since your first post. My utility went along with me also until they found how much it was gong to cost them to have my system hooked to their system and bank my excess.
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  • shawnbath
    shawnbath Registered Users Posts: 5 ✭
    #13
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    Re: grid tie recommendations

    I guess maybe I wasn't clear. I don't think the city will be interested in buying the excess but I haven't got that far in discussing it them. That is why I would like to get system setup that will be close to what I need. I will be able to be within 100ft of my grid connection. Thanks again shawn
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #14
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    Re: grid tie recommendations
    shawnbath wrote: »
    I guess maybe I wasn't clear. I don't think the city will be interested in buying the excess but I haven't got that far in discussing it them. That is why I would like to get system setup that will be close to what I need. I will be able to be within 100ft of my grid connection. Thanks again shawn

    Which city utility is it? How will they treat your bill if the net is less each month? Will they provide a meter that is assured to at least run backwards, some don't and you get billed for the watts pushed back onto the grid as well.
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #15
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    Re: grid tie recommendations

    I know about all the Grid Ties laws, you can bet it's like my state, all Rural co-op's and Municipal owned Utilities are exempt from them. There is something in the Rural Electrification Act that is in conflict. They can still do it, but it's all voluntary. Just letting you know some of the pitfalls and questions to ask.
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  • DanS26
    DanS26 Solar Expert Posts: 266 ✭✭✭
    #16
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    Re: grid tie recommendations
    shawnbath wrote: »
    Ok thanks for the input. I talk to the city utilities this morning and they have never had anyone inquire about solar so I don’t think I will have any issues there. I have 2 good friends who are master electricians also so I got that covered if need be. I think after the input I have received I will just do a stationary setup. My wife is nervous about spending 20+ grand right off the bat so to comfort her I believe I will do this in 2 steps and then maybe a 3rd if we need it later. It is only 1 meter feeding both services. Thanks again for your input and advice Shawn

    If you are doing the arrays in stages, then think about making sure the underground conduit is large enough to pull additional wires later, but that is such a pain. If you can afford it, lay all the additional wires now.
    23.16kW Kyocera panels; 2 Fronius 7.5kW inverters; Nyle hot water; Steffes ETS; Great Lakes RO; Generac 10kW w/ATS, TED Pro System monitoring
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