Introduction

DC BuildersDC Builders Registered Users Posts: 13
Greetings

I am new to the forum. Am attending an eight week 48 hour class at Indian Valley College on Solar Installation and Integrations.

Learning Objectives: Safety safety safety working with PV systems; Site evaluation; Design a grid tied system; Install components; Perform a system checkout and inspection;

Successfully pass Entry Level Certification Examination from NABCEP.

Complete and present the following to Class:

kWh use--year and average daily; Site diagram; Site evaluation; Battery bank for 3 day outage; PV sizing and design--Number of panel and strings--select combiner, inverter, DC and AC disconnects; Finish site diagram locate Modules, Meter, Inverters, Disconnects, Conduit and Wire size; Complete a single line electrical schematic.

Professor Barrall advised us to check out your Forum.
Forty year ago I was 3 year Electrician Apprentice.
Been a General Contractor For 34 years.

My Project:

Location: Mill Valley, CA. 37.6N, 122.4 E

Usage based size is 14 kWh at 5.6 sun hours daily = 2.5 kW

Want to run 14 210W modules for 2.9 kW

One string 372 Vdc, 7.9A, Tilt 25 degrees. (Lat -13)

Azimuth S 39 E.

Comments regarding array performance and battery selection would be appreciated.

Thanks,
Dan

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,511 admin
    Re: Introduction

    If I did the PV Watts correctly (SFO is closest site):
    "Station Identification"
    "City:","San_Francisco"
    "State:","California"
    "Lat (deg N):", 37.62
    "Long (deg W):", 122.38
    "Elev (m): ", 5
    "PV System Specifications"
    "DC Rating:"," 2.0 kW"
    "DC to AC Derate Factor:"," 0.770"
    "AC Rating:"," 1.5 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 25.0"
    "Array Azimuth:","129.0"

    "Energy Specifications"
    "Cost of Electricity:","12.5 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 2.81, 125, 15.62
    2, 3.76, 153, 19.12
    3, 4.58, 209, 26.12
    4, 5.92, 260, 32.50
    5, 6.54, 296, 37.00
    6, 6.72, 292, 36.50
    7, 7.20, 321, 40.12
    8, 6.46, 287, 35.88
    9, 5.93, 253, 31.62
    10, 4.47, 199, 24.88
    11, 3.07, 132, 16.50
    12, 2.53, 112, 14.00
    "Year", 5.00, 2638, 329.75
    For "raw" power--seems to be a bit on the small side (based on information I have).

    15kW*30days=450 kWhrs per month

    I have a similar 3.5 kW site in San Mateo CA... PV Watts seems to agree pretty well with my performance figures.

    For PG&E utility customers--E-6 Time of Use is the "standard rate plane" (do they still allow E-1?).

    How do they teach you to estimate that various time of use and tiered pricing from a plan as complex as the E-6. If the home can avoid peak times during the summer--E-6 can be a benifit. However, if the home cannot time shift/shed loads during peak times and/or the array is only a fraction of total power usage--E-6 can (in some cases) cause a Solar Assisted Utility Bill to be higher than the original E-1.

    I am running the old E-7 which works out well for us. I could probably use 1/2 the size of array I have now and break even (right now, I have a $300+ credit every year--planned for more loads--conservation really took hold at our home).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • DC BuildersDC Builders Registered Users Posts: 13
    Thanks Bill for PV Watts

    Hi Bill,

    I remember Mark talking about PV WATTS. It did not sink in.
    As far as those rate and TOU questions, the answer is, I really don't know.

    Low on raw power?

    Read the help page regarding the N#S bearing conversion to North=zero.
    The way I posted was a bit confusing, think my roof plane is facing 151 degrees.

    It is 29 degrees East of Due South. Basis of bearing I think is Mt. Diablo Meridian. I have put a compass to it with magnetic declination correction.

    Thought only the longitude determined solar noon, come to find out that it is not as simple as that.

    Seems in February the sun is a little late. Four times a year it is on time (sound familiar?)

    122.4 longitude /15 degrees= GMT - (8.16h) then add about -(15 minutes). On the 12th of February solar noon here is approximately 12:25 PM, or no?

    Thanks again
    Dan
  • BB.BB. Super Moderators, Administrators Posts: 29,511 admin
    Re: Introduction

    "Raw Power" in the sense of kWhrs per day from the panels / GT inverter being generated vs load of the home. Sorry--should have been 14kWhrs per day:
    • 14kW*30days=420 kWhrs per month
    The "peak months" are only around 300 kWhrs a month (with my slightly off compass interpretation).

    The "adjusted power" (if you want to call it that)--For my E-7 plan (just to keep the numbers easy)--with baseline (lowest pricing tier)... Monday thru Friday during summer--I "get paid" $0.27 per kWhr or so... All other times, I pay $0.09 per kWhr (when I try to run my electric loads loads).

    So--my weekday Time Of Use pricing makes my solar panels "3x larger" because I can "buy" my power back at 1/3 the price off peak.

    If you have a customer that is using TOU pricing and they cannot avoid the peak power times (E-6 is much more complex and wider time slots)--they can end up buying their power during the expensive times instead of selling (too small of array, too much peak period power usage).

    So far--I have not seen a good way to estimate how a customer may end up being effected by a TOU plan (nobody measures their power in 1 hour blocks during the week)...

    Now--however, PG&E (Northern California) is converting over to the "Smart Meter" which does send the hourly (or 15 minute data for commercial) back to PG&E for billing--I wounder if they can give you a month or a year of information and a spread sheet (with the rate/tier plans)--where somebody can simulate solar production overlaid on PG&E billing...

    It would be very interesting (but probably highly messy).

    The local noon moves with seasons--And, for a TOU plan that charges more for late morning through evening power--a south west facing array will tend to favor a TOU plan...

    PG&E Tariff Plans


    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • DC BuildersDC Builders Registered Users Posts: 13
    Re: Introduction

    Bill,

    I see what you mean regarding the rate structure.

    I have an old HP Laser Jet 4V printer (good machine, kind of power hungry)
    Do the AHJs accept "B Sheets" 17 x 11 for permit submittals.
    I have AutoCAD 2007 LT on my computers, took a ten week class (300 hours) at Martinez Adult Education Summer of 2007.

    Do you like single line drawings for Electric Schematics? I guess there are liability issues when showing the neutrals and negatives.
    Not bad practice for students, but the building departments don't want to see them.

    EDIT: [The above paragraph is all wrong, he wants the neutrals, switches, negatives, grounds and everything else shown on the drawing]

    Professor B only wants to see single line drawings. Sounds right to me.

    EDIT: [Above paragraph is all wrong as well, not what he said nor what the slides indicate either]

    Ever done a battery back up?

    Glad I found this site.

    Dan
  • BB.BB. Super Moderators, Administrators Posts: 29,511 admin
    Re: Introduction

    I am not a solar designer--I am a electrical/systems design engineer (mostly computers/network gear from times past). Have done some battery based (Telcom equipment)--but not battery based solar. My system is a 3kW GT system for my home (professionally installed).

    Single Line drawings are great for getting the idea across of how something works--and building departments seem to be OK with those (in my limited experience).

    However the devil is in the details. Solar is kind of in the middle of complexity and code--GT which requires permits and inspections -- vs off-grid which frequently nobody looks at.

    Outback has some nice system drawings which can give you some good examples done by others.

    The schematics that we did--full every wire and component to layout circuit boards and ICs (which eventually became logic equations and state machines instead of schematics)...

    Getting experience in the region and on the products you will be working with is great training--and with your background--you will pick it up on no time (if you have not already).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • notsobrightnotsobright Solar Expert Posts: 247 ✭✭
    Re: Introduction

    hi DC, this forum has been extreamly helpful to me and I looked lurked arround several others before deciding to join here. lots of good people and info here.
    Do you like single line drawings for Electric Schematics? I guess there are liability issues when showing the neutrals and negitives.
    Not bad practice for students, but the building departments don't want to see them.

    Professor Barrall only wants to see single line drawings. Sounds right to me.

    hey, out of curiousity Im intrested to know why there might be "liability issues when showing nuetrals and negatives" and "the building departments don't want to see them."

    line drawings are the only schematics I can follow. the rest are very frustrating to personaly since the ones I use (auto industry) never seem to include suplimental infos needed to "decode" them.

    at least with the continous (sp?) line drawings theres really nothing else needed to follow them. everything you need is on that page.

    I wont be much help with your learning here as Im still learning the basics myself hence why I ask that.

    well anyway, best wishes on your training there and hope you enjoy the NAWS forum!
  • DC BuildersDC Builders Registered Users Posts: 13
    Wrong about drawings

    Hi,

    My earlier post in this thread was wrong about not drawing the negatives, neutrals, grounds etc. I have edited the prior post.

    Sorry, about the misinformation.

    Dan
Sign In or Register to comment.