Modifications to Small System

Hello Everyone,

Thanks for the great information to my last few questions at http://www.wind-sun.com/smf/index.php?topic=2186.0

I have made some adjustments to my system I was hoping to run by you wizards and was also hoping I could have some additional questions answered.

I was thinking now of 2 Kyocera KC130 panels, an MX60 Outback charge controller, 2 Lifeline AGM GPL-4D in parallel for 420Ah at 12V and a Prosine 2.0 inverter.  I expect about 5 to 6 hours of unobstructed sun per day here in Hawaii.

I decided upon the MX60 controller for reliability based upon the charge controller being the most prone to fail according to a survey done in Hawaii on photovoltaic systems.  http://www.hawaii.gov/dbedt/info/energy/publications/pvsu95.pdf

This MX60 charge controller and the prosine 2.0 allows for expansion of the system and hopefully reliability.  Total cost of system should be around $4200.  Any suggestions on what combination of components would improve my system would be appreciated.


The panels will be 22 feet from the controller.  The controller, batteries and inverter will all be close to each other.  There will be a 25 foot extension cord out of the inverter to appliances.

Questions –

1)  Should I wire the 2 KC130 panels in series or parallel?

2)  What is the difference between a KC130TM and a KC130GT?

3)  When you wire the solar panels either in series or parallel, is it better to have the combiner box close to the panels or since this will be a pole mount or can I just combine the wires closer to the controller?

4)  Where do the fuses or breakers go, does it matter which is used?  Is one better than the other?

  That’s all the questions that I can think of for now. :-D   Thank you very much everyone for your time and knowledge. 

Aloha!
Ralos









Comments

  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: Modifications to Small System
    Ralos wrote:
    I decided upon the MX60 controller for reliability based upon the charge controller being the most prone to fail according to a survey done in Hawaii on photovoltaic systems.  http://www.hawaii.gov/dbedt/info/energy/publications/pvsu95.pdf

    Just Curious what the above document lead you to believe the MX60 would be better? , its not even in the list of the respondents. For such a small system, in a tropical climate, a low-cost pwm controller like the Xantrex C40/C60 would actually yield a higher net energy harvest. The MX60 has a pretty hefty operational draw and with hot panels, there is no advantage of a mppt controller in such a small system, actual it is a loss. The MX60 mppt controller has higher idle and active losses, it also has a minimum Vin/Vout drop, of about 1 volt. So if the hot panels vmp is at the battery voltage ( which is very likely ) the MX60 will HAVE to have the array battery voltage + 1 volt. This can be overcome by having the panels in series so its 24V -> 12V nominal with the MX60, but the tar losses exceed any gains the mppt would give you for your climate. Also, for the cost difference of a MX60 to a C60, you could add another 50 watts of PV.

    Mppt is a really great technology, but currently available mppt charge controllers are best suited for larger systems ... maybe one day there will be a TRUE mppt controller that is also efficient at low power level and costs similar to a pwm controller  :-D
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Modifications to Small System

    Ralos,

    I think your revised system is still too small to meet your proposed energy requirement. I recommend you revisit my May 9, 2007 post on this topic: http://www.wind-sun.com/smf/index.php?topic=2186.msg16269#msg16269

    Regards,
    Jim / crewzer
  • System2System2 Posts: 6,290 admin
    Re: Modifications to Small System

    Hi Solar Guppy,

    The reason why I thought the MX60 would be better was that sodamo from this board said he went through a ProStar 30 Charge Controller and a BZProducts MPPT500 and currently has an MX60 which he is very happy with. Also, the report mentions people having problems with the Trace C30 controller which is now Xantrex.

    Thank you for your thoughts.



    Hi crewzer,

    My power requirements are not set in stone. I am currently on grid and this system will only supplement my power needs. If the PV system cannot provide the power I need, I can always draw from the power company. I am limited by finances and definitely limited to 2 PV panels only being that I currently rent.

    I could increase the battery bank to 3 GPL-4D or upgrade to a slightly higher wattage PV panel but can’t really go much past the cost $1500 for 2 panels.

    So basically, I guess I’m asking what would be the best system for about $4200

    Thank you,
    Ralos
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Modifications to Small System

    Ralos,

    Thanks for the additional information. Limits on PV size and budget will definitely affect your candidate system’s ability to meet the original goal of 300 W x 30 hrs/week = 9 kWh/week (net), or 1,287 Wh/day.

    Note that PV modules rarely ever supply their nameplate rating, and they certainly never will in Hawaii, except, perhaps, briefly during “edge-of-cloud” events. The nameplate specs are important for determining “design” voltages and currents for NEC calculations, but they typically have little to do with real world performance.

    For example, the California Energy Commission, using PVUSA specs, rates the KC-130 module at 115.2 W, or 88.6% of their nameplate rating. And the KC-85 is CEC PVUSA rated at 76.8 W, or 90.4% of its nameplate rating.

    http://www.consumerenergycenter.org/cgi-bin/eligible_pvmodules.cgi

    Returning to the focus of this effort, another design path for you to consider would be to spec a balanced system within your environmental and budget limits and estimate what its capabilities might be.

    For example:

    1) A pair of KC-130 modules wired in parallel would be rated for 7.39 A Imp x 2 = 14.78 A.
    2) I’m still using “worst case” average insolation for Honolulu = 4.8 hrs/day
    3) The “260 W” PV array would supply 14.78 A x 4.8 hrs/day = 70.9 Ah/day
    4) Assuming VRLA battery coulombic efficiency (Ah out / Ah in) of 98%, a 12.4 V average battery voltage, and inverter efficiency of 87%, the average net available energy would be ~750 Wh/day -- ~58% of your original goal.

    Such a system would include the following items:

    - Two each KC-130 PV modules
    - One each Morningstar PS-30M PWM controller
    - One each Exeltech XP600-12 sine wave inverter
    - A battery bank rated at 12 V X ~280 Ah
    - One each Xantrex TC-20+ battery charger (120 VAC -> 12 VDC; optional)
    - Misc cables, breakers, fuses, etc.

    This collection of high-quality equipment would certainly cost well under $4,200. You can check the prices and specs via the NAWS store’s website. Assuming that the controller and batteries will be kept indoors, you probably won’t need a remote temp sensor for the batteries, as the PS-30M has one built in.

    The advantage of this system are that it would meet your size and budget limits. Disadvantages include limited growth potential and the inherent limits of a 12 VDC system.

    Does this help?

    Regards,
    Jim / crewzer
  • System2System2 Posts: 6,290 admin
    Re: Modifications to Small System

    Hi Jim / crewzer,

    It seems you answered my question as I sent it to you. Thank you so much!
    You've been a BIG help along with several others on this forum.

    I will try to digest the information.

    Thanks again,
    Ralos
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Modifications to Small System

    Ralos,

    Yest another strategy might be to consider a 24 VDC system built around an OutBack FX2524T inverter/charger and a Mate. Carryover components from my earlier post would include the pair of KC-130 PV modules (wired in series for “24 V”), the MorningStar PS-30M controller (operates in 24/24 or 12/12 modes), misc. cabling, breakers and hardware, as well as your preferred batteries.

    An initial disadvantage of this configuration would be that the inverter would not operate particularly efficiently at low power levels. In fact, its standby requirement is ~20 W. However, it’s pretty easy to turn the inverter off via the Mate or via a hardwired switch when there are no active AC loads.

    On the other hand, there are several advantages to this configuration. One is that the inverter’s power rating (2500 W at 120 VAC) is substantial and would allow for considerable expansion over time. I have one of these beasts, and it has no problems running our fridge, our washing machine and our home AV system all at the same time (although I don’t do this often).

    Another advantage of this inverter/charger is its HBX, or High Battery Transfer, feature. In short, the inverter, when connected to an AC source (i.e., the grid), can sense a low battery voltage, transfer the AC load from the inverter to the AC source, recharge the batteries, and then transfer the AC loads back to the batteries and inverter – all automatically!

    And, everything else being equal, 24 VDC systems operate at ½ the current of 12 VDC systems, so wiring can be smaller and/or wiring losses reduced, and 24 V inverters are typically a bit more efficient overall than comparable 12 V models. The Mate would be required to program and operate the inverter.

    The Morningstar PS-30M controller can handle PV arrays rated up to ~800 W (STC) when configured for “24 V”, so that should give you a fair amount of expansion room. If you decide to expand even further, you’ll need to buy a larger controller. Or, perhaps go ahead and spring now for a Morningstar TriStar-45 with optional meter. An advantage of the TriStar is that it’s UL listed.

    Another susbsystem to consider is the MidNite Solar E-panel. This well-equipped electrical panel system will safely connect and integrate the array, controller, batteries and inverter, although you may need to purchase an extra couple of breakers.

    Including the pair of your locally sourced batteries, I’d expect you could assemble this system for ~$4,500. Shipping may add a bit more cost.

    HTH,
    Jim / crewzer
  • System2System2 Posts: 6,290 admin
    Re: Modifications to Small System

    Hi Jim/crewzer,

    Thank you so much for your excellent ideas.  So many options to consider. :|  That FX2524T sounds great.  You've got me leaning towards a 24V system.  I’m looking at maybe larger panels.  I’ll have to price these locally since the shipping cost for these to Hawaii are outrageous.

    Looks like it might be closer to $5000 for this system. 

    Thanks,
    Ralos
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Modifications to Small System

    Ralos,

    This business might be worth consideration: http://www.outbackpower.com/dist_namer.htm#Hawaii

    I don't know anything about 'em, and this is not an endorsement.

    HTH,
    Jim / crewzer
Sign In or Register to comment.