Converting old off-grid system to grid-tie suggestions

Hi Guys

I've taken on a the repair of an old off-grid system, which has not been functional for a number of years. The inverter no longer functions and I am unsure of the exact problem. Regardless, the house is on the grid and the owner has no desire to mess with batteries. I think the best approach would be to switch it over to simple grid-tied system (without batteries). I am looking for any thoughts on this.

Some specific questions to address:

1. PV Panels- Currently there are currently 16x 75watt (1.2kw) Siemens 12v panels wired in 2 strings at 150volts each. They are mounted on two 6" poles as seen in the picture. If possible, I would like to make the system a bit larger. Either by selling the existing panels or adding to them. Any thoughts on this? Any idea of the value of these panels (provided they are still within spec)?

2. Batteries- Provided they are still in good condition (which is unknown at this point until I check with a hydrometer); Any ideas as to the value of each battery and the best way to sell it, craigslist?

3. Inverter- If I reuse the old panels (all or a portion of them) and wanted to add additional panels, that would require me to purchase an inverter with two DC inputs (MPPT trackers)- correct? Currently there is only one string buried in conduit from the combiner box. I'd like to avoid running new conduit- but that may not be possible.

4. Existing Inverter/Charger/Load Controller- I believe the inverter is broken, although I am uncertain. Any idea of it's value? There may be parts of it I could reuse but I am inclined to keep it intact as possible try and sell it that way. Any suggestions?

I am sure I will have more questions as this project moves along but I'd appreciate any help steering me in the right direction. Any thoughts?


Thanks!
matt

Comments

  • BB.BB. Super Moderators, Administrators Posts: 28,992 admin
    Re: Converting old off-grid system to grid-tie suggestions

    First question--Does the utility allow Grid Tied solar.

    Second question--What are the GT solar rates for the utility. Some utilities these days are starting to make it "very expensive" to install GT solar (high per month charges, low per kWH billing).

    Assuming the answers to the first two questions are Yes/Makes economic sense. I would doubt there is much that can be salvaged from the existing system.

    If the solar panels are old, they many not have UL listing and not be rated for 600 Volts insulation--Older battery based systems used solar panels with ~75VDC maximum rating and these panels will not be "legal"/safe for use with standard AC inverters which have ~200-600 VDC input voltage ranges.

    You could look for Micro Inverters and connect (for example) 2-3 of these panels in parallel with an Enphase inverter--But it is possible that the Enphase installation will not meet its UL requirements, will be then non-compliant, and if you have a local building inspector, they should not approve the system.

    So--I would start from the beginning... Loads, rate plans, and expectations. Do a paper design (i.e., is a 1,200 WH solar array enough power for this home, or would a larger system make more sense).

    In general, today's turnkey install pricing has never been cheaper--You may find you can get a good sized system (3-10kW solar array) system installed at ~$2-$5 per Watt. The existing 1.2 kW array would, at best, save you ~$1,200 (at ~$1 per watt for new 250 watt solar panels)--But cost you more than that for all of the configuration/wiring/regulatory issues to fix.

    Questions/comments?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • runningduckrunningduck Registered Users Posts: 6
    Re: Converting old off-grid system to grid-tie suggestions

    Bill,

    -Yes they do allow grid tied solar here in New Hampshire. The state has a rebate of 0.75cents/dcWatt too- I have the paperwork and they actually do allow homeowners to self install. I've read the paperwork and I think I've got that part covered.

    -I am aware of the need for it to make financial sense. I have a year of her electrical bills and have done some calculations with PVwatts etc. I still need to do some more calculations once I have a direction to go- in mostly to maximize the the state rebates and ultimately ROI.

    -Now that you mention it- I don't see a UL listing on the panels (I will need to check that). They are rated for up to 600vDC though.

    - I am familiar with enphase microinverters (I am actually using them at my own house). I might try stringing a few panels together myself but for someone else's system I'd rather not.

    - I took this project on more for the opportunity to learn then anything else. I've dabbled in solar for the past few years and I've always wanted to do more. I am looking at this as an opportunity to do just that.

    - If I was to "start over" replacing the panels and inverter etc.. Any idea as the value of existing system and any idea of the best way to find a buyer?
  • westbranchwestbranch Solar Expert Posts: 5,136 ✭✭✭✭
    Re: Converting old off-grid system to grid-tie suggestions

    Your idea to switch it to GT is probably the best.
    A GT system will need to be designed by a professional and installed by a pro... they may not be the same person.

    The equipment there was good at the time and may still have some life left, but one never knows.

    Post it on the For Sale thread here and you might get some bites. Shipping can be pricey.

    http://forum.solar-electric.com/showthread.php?16275-For-Sale-Thread&highlight=sale
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • westbranchwestbranch Solar Expert Posts: 5,136 ✭✭✭✭
    Re: Converting old off-grid system to grid-tie suggestions

    our host has this system pricing for example. http://lib.store.yahoo.net/lib/wind-sun/enphase-estimate.pdf
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • peakbaggerpeakbagger Solar Expert Posts: 341 ✭✭✭
    Re: Converting old off-grid system to grid-tie suggestions

    Based on the photos, the panels are quite old, possibly 15 to 20 years?. They are monocyrstalline but look at them very carefully for any sign of delaminating as Siemens of that type and vintage did have this issue. Unless the photo is distorted, the racking appears to be inadequate given the obvious twist in the left side mount. These are most likely 12 volt modules so there is a demand in some areas for off grid low voltage panels for remote camps. If you are lucky you may get 25 to 35 cents a watt.

    Assume the batteries are worth scrap value, call a battery supplier and they will usually buy them for weight.

    With only one set of wires out to the pole, you are very limited on your options. If the wire is 600 volt rated, you may be able to find a small grid tie inverter that will accept the voltage range but small grid tie inverters are getting rare and the cost per watt is high.

    In general, I think the best option is to sell it as a package for an off grid system after possibly trying to get the batteries to hold enough charge to see if the inverter works.
  • runningduckrunningduck Registered Users Posts: 6
    Re: Converting old off-grid system to grid-tie suggestions
    peakbagger wrote: »
    Based on the photos, the panels are quite old, possibly 15 to 20 years?. They are monocyrstalline but look at them very carefully for any sign of delaminating as Siemens of that type and vintage did have this issue. Unless the photo is distorted, the racking appears to be inadequate given the obvious twist in the left side mount. These are most likely 12 volt modules so there is a demand in some areas for off grid low voltage panels for remote camps. If you are lucky you may get 25 to 35 cents a watt.

    Assume the batteries are worth scrap value, call a battery supplier and they will usually buy them for weight.

    With only one set of wires out to the pole, you are very limited on your options. If the wire is 600 volt rated, you may be able to find a small grid tie inverter that will accept the voltage range but small grid tie inverters are getting rare and the cost per watt is high.

    In general, I think the best option is to sell it as a package for an off grid system after possibly trying to get the batteries to hold enough charge to see if the inverter works.


    I am leaning towards just doing that; Replacing the panels and then using enphase microinverters. I have experience with the enphase system and it would make the whole project a lot simplier. In addition it would make it easier to expand the system later if the owner would like.

    The next step would be for me to figure out how many panels (standard 60 cell panels) the existing racking can hold. I presume if I can find the model number of the existing racking (top of pole mount); I should be able to find how much weight it is rated for? As you pointed out it may need to be replaced as it's distorted right now. Once I pull the panels off I should be able to tell if it's bent or damaged.

    Any ideas as to how best find a buyer for this? Anything better then craigslist?

    Your input is much apprecaited!
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Converting old off-grid system to grid-tie suggestions
    I am leaning towards just doing that; Replacing the panels and then using enphase microinverters. I have experience with the enphase system and it would make the whole project a lot simplier. In addition it would make it easier to expand the system later if the owner would like.

    The next step would be for me to figure out how many panels (standard 60 cell panels) the existing racking can hold. I presume if I can find the model number of the existing racking (top of pole mount); I should be able to find how much weight it is rated for? As you pointed out it may need to be replaced as it's distorted right now. Once I pull the panels off I should be able to tell if it's bent or damaged.

    Any ideas as to how best find a buyer for this? Anything better then craigslist?

    Your input is much apprecaited!

    New modules are so cheap these days that you won't get much for the old ones. Likewise for the inverter (is Trace even still in business?). If the batteries haven't been maintained then they probably are only worth their scrap value. The existing array is very small; it might not be worth it to jump through all the hoops to get a system that size interconnected.

    Microinverters might be an option, but you'll have to look at the existing wiring to see if it can be used.
  • peakbaggerpeakbagger Solar Expert Posts: 341 ✭✭✭
    Re: Converting old off-grid system to grid-tie suggestions

    I dont know what area of the country(or world ) you are in. In northern New England there is Uncle Henrys which is regional classified ad magazine. The hassle with selling used equipment is even if its as is where is, the purchasers rarely have a clue on what they are buying and lot of them get cold feet when it actually come to handing over cash.

    On the other hand, I had a batch of older Siemens panels and let a campowner on a lake know I had used low voltage panels and between he and his neighbors they cleared me out and paid me 50 cents a watt.
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