SYSTEM DETAILS

Total solar panel output (standard conditions)	2250W DC
Best case output	2175W AC
PV USA Test Rating output (PTC)	1765W AC
Solar Panels	12 Sanyo HIP-190BA3
Configuration	6 panels in series, 2 strings in parallel
Panel orientation	160 deg (SSE), roof angle 18 deg
Inverter	SMA Sunnyboy 2500 SBD

ENERGY SUMMARY Period: April 27, 2008  - Oct 19, 2008 Average daily electricity consumed: 12.23 kWhrs Average daily electricity generated: 12.94 kWhrs Avg daily electricity gen. (this week): 7.4 kWhrs Total electricity generated, this period: 2.498 MWhrs Total electricity consumed, this period: 2.317 MWhrs Net elec. cost (US$): -135.97 (negative = energy credit) Projected yearly electricity production: 3.45 MWhrs Total Installation cost (including rebates):US$ 7,900 Other Information: Lifetime Electrcity Generation: 12.648 MWhrs Uptime:1273 days Sulphur dioxide: 32.8 kg Nitrous oxides: 33.5 kg Carbon dioxide: 12.154 metric tonnes

This website describes a 2.2kW so called high voltage (315VDC normal operating voltage) grid-intertie PV system without battery backup. The output to the electrical grid is 240VAC/60Hz (split phase). The design was done with the help of a spreadsheet in late 2004. It involved studying our energy consumption patterns, regional temperatures, panel orientation, shading, roof angles, solar panel characteristics - their voltages, temperature related properties, inverter characteristics etc.  Pricing, rebate numbers, utility metering types etc. were also considered.  After an optimum "solution" was reached the various components were ordered and  procured in early 2005. The construction was carried out mostly in the month of March 2005. The installation consisted of three parts: roof prep work, AC hookup to grid and solar panel/inverter DC installation. A roofer was contracted to install the standoffs on the tile roof. The image below shows the view of the sky from our roof and the path the sun takes during the year. Shading effects can be seen quite clearly due to the surrounding trees.

The AC electrical wiring from AC disconnect to the utility panel was handled by an electrical contractor.  The rest of the installation that included the DC wiring and disconnect, solar panels and inverter installation was carried out by me with help from some enthusiastic friends. The work took approximately a month (mostly on weekends). The system was inspected by the city of Pleasanton, CA in early April and PG&E approved the grid intertie connections on April 13, 2005. A digital "time of use" (TOU) meter was installed by PG&E at this time. At the same time we opted for an E-7 metering schedule, where from 1200-1800hrs (Monday-Friday) energy use is considered as peak power use time. Rest of the time is considered non-peak power time. With TOU metering, it is possible to generate less power than consumed and still achieve a net-zero electricity usage in terms of cost. This is made possible by reducing consumption of peak power and generating net excess peak power during such times (peak power is more than 3 times as expensive as non-peak power from May 1st through Oct 30th).

The best case power output under clear skies has been 2150W close to the best case design numbers. Under partly cloudy conditions with direct sunlight on the panel, the output has reached 2500W (inverter maximum output) due to reflected incidence of solar radiation from the clouds.

Based on our usage patterns and time of use metering, it is expected that our net long-term electricity energy costs will be zero in the foreseeable future. There is still a grid interconnection fee and other small utility fees that will need to be paid but these will be minor. The only way to avoid these fees would be to be completely off-grid, but that doesn't make sense unless the grid itself is unreliable, which it is not, at this point. Also off-grid systems tend to be low voltage designs with heavier wiring, have to deal with battery maintenance/replacement, lowered overall conversion efficiencies and the capital investment of a charge controller.

Data for 2007-2008
Data for 2006-2007
Data for 2005-2006 and system validation

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