Introduction

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

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

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