Bob's Solar Project

At about 1 pm today, the output from my solar shingles exceeded 2000 watts! The shingles are rated for a maximum output of 17 watts each, which with 84 shingles should give me 1428 watts. Unisolar says to expect higher output in the first months of use, but this is pretty impressive--about 24 watts per shingle!


(See below* for explanation)

Unfortunately, because of the low capacity of my soon-to-be-replaced cheapo batteries, and because I didn't receive a functioning Outback Mate Controller until last Friday (7/8), I haven't been able to take full advantage of this large amount of power. Here are the daily kilowatt-hour totals for July so far:

Fri. 7/1 6.2 kw-h
Sat. 7/2 8.3
Sun. 7/3 9.1
Mon. 7/4 7.3
Tue. 7/5 1.3
Wed. 7/6 1.0
Thu. 7/7 1.0
Fri. 7/8 1.0 (Mate installed late in day)
Sat. 7/9 8.0
Sun. 7/10 10.2
Mon. 7/11 3.5
Tue. 7/12 3.2
Wed. 7/13 4.0

Another reason I'm not able to use the full amount of energy available is that I don't have a "dump load" set up yet. I plan to use the dehumidifier as my summer dump load--whenever the batteries are fully charged and the sun is still shining, the dehumidifier will run. On weekends, I have been able to run large loads while the sun is shining--dehumidifier, box fan, dishwasher, washing machine, rice cooker, etc. That's why the weekend totals are higher (it has been pretty uniformly sunny or partly sunny all month long).

* Explanation of charge controller display:
IN 54 V, 37.3 A: The maximum power point tracking MX60 is showing 54 volts to the solar shingle array and receiving 37.8 amperes of current.
OUT 52.8 V, 38.1 A: This is the voltage and current being used to charge the batteries.
WATTS 2011: The current power output of the shingles, equal to the voltage times the current (either IN or OUT, ignoring small internal losses in the charge controller).
AUX OFF: The auxiliary output is off.
kWHrs 3.2: Total number of kilowatt hours passing through the charge controller so far today.
MPPT: Maximum power point tracking. Means that the charge controller is presenting the optimum voltage to the solar array which will produce the most power. The charge controller periodically sweeps through a range of voltages, multiplies the voltage times the current, and finds the largest product. This is the MPPT voltage. This can change depending on the amount or angle of sunlight, the temperature, and other factors. MPPT charge controllers like my Outback MX60 are supposed to yield as much as 30% more power from a solar array than the less-expensive charge controllers which serve mostly to prevent overcharging the batteries (the MX60 also prevents overcharging).