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Solar Power

I wrote a detailed solar power data display application to show the details about my solar power system back in California.  Unfortunately the Internet has deprecated the method I used to run the applet within this web page, and the system has been dismantled and sold, so I can only show you a screen capture.

Note that it's a Java application (not applet) that your web browser launches using Sun's Java Web Start technology.  The following steps take place when you click the screen shot above:

1) Your web browser loads the Java application launch description file (.jnlp) from this web server.
2) Your web browser reads the .jnlp file and prompts you to run the Java Web Start Launcher, or install the required Java support.
3) Java Web Start downloads the latest copy of the application's files or uses the ones already cached.
4) You will see a popup dialog asking for permission to read from sirocco.accuweather.com. I read satellite images from there and display them in the application as you can see above.  Please click OK.
5) It takes a little while to read the real-time and historic data files from their server.
6) The application launches in its own window on your desktop.

Some interesting things about the application:

* I don't read or write any data from your local system. I don't need to, and the Java security mechanisms wouldn't let me.
* The data logging computer connected to the power inverter uploads new sample data to this web site every 30 seconds
* The application queries the web site every 30 seconds for new data and updates the user interface
* The Cloud Cover image is updated every 15 minutes, but the time stamp lags due to Accuweather processing time for the satellite.
* The gauge and charts, from the JFreeChart open source project, are zoomable and configurable. Try dragging a rectangle.  Drag a line straight up to unzoom. Right-click to change chart settings.  I paid for the developer documentation for this excellent software.
* The application window is resizeable but the gauge and satellite image aren't.
* It doesn't handle running overnight well.  I have this on my to-do list for version 2.

If you have any comments or suggestions, please email me at mwbrown42 at gmail dot com..

Solar Power Background

Solar Installation Pictures

I moved to Paso Robles, California in June 2007. "Paso" is on the Central Coast, halfway between Los Angles and San Francisco, in the middle of a large winery region. The grapes like this area because of the warm days and cool nights.  Paso gets over 300 sunny days per year so about 6 months before I moved, I started planning the installation of a solar power system.

I try to do what I can for the environment, including using only Compact Fluorescent bulbs, recycling, using less, reducing greenhouse gas generation, running B-20 biodiesel and generally being smart about my impact.  I think it makes a lot of sense to generate electricity from the sun, if you have a suitable climate, good installation location and the significant money to spend up-front, for a long-term payoff.

With the system in place, I can follow my plan to migrate to an electricity-only property, changing from a propane tank and propane appliances to a tankless electric water heater, electric stove and electric heating system.  And maybe an electric car someday to get me 10 miles into town and back... This plan was further reinforced by the stories of rolling blackouts and Enron price-fixing in the electricity market here in California

This is what I'm trying to avoid; check your electricity cost and let me know how it compares. (kW = thousand watt-hours consumption).  Pacific Gas & Electric has a staggered monthly rate schedule (E-1 for normal households) that currently goes (approximately) like this. The lower tiers' prices have been stable for a while, but the higher tiers are expected to increase.

    0-400 kWh:               11 cents / kWh
    401-800 kWh:           17 cents / kWh
    801-1100 kWh:        24 cents / kWh
    1101 - 1400 kWh:     28 cents / kWh
    1400+ kWh:             37 cents / kWh

Looking at my last full Austin electric bill (May/June 2007 with the air conditioner running) of 1725 kWh , I paid $173, including fees and taxes. Here, that would have cost me $388.25, without fees and taxes. I have a lot of computers and woodworking tools and I don't look forward to bills like that every month.

So the decision was pretty easy. I did some research and everything pointed to hiring REC Solar, based in San Luis Obispo, to design and install the system.  Les Kangas is the REC sales rep for my part of Central California. After a lot of emails back and forth and several visits to my house, we agreed on a strategy and component suppliers as follows:

    25 Sanyo 200W panels                             Best in the heat of the north county, and most efficient power conversion
    1 Xantrex 5000W DC-AC inverters         Great efficiency and very programmer-friendly for pulling historic and real-time data

This delivers a 5000 watt system, a good size for my expected usage. We chose an inverter sized for the maximum panel output, but in the future I can bolt on more panels and buy another inverter. I had thought to buy two 3800W inverters now, sized for a 50% capacity upgrade, but in the early morning and late evening the panels may not be able to supply the minimum power required to drive the inverter efficiently. Also I would be putting money into extra inverter capacity when in fact I may be happy with the 5000W system.

I will not have a battery bank as I don't feel the need to be totally "off-grid", plus the batteries and the charger are expensive and the batteries lose their capacity over time. During the day as I generate more than I use, my excess power goes out onto PG&E's grid and my electric meter spins backwards. At night as I draw power, the meter spins forward. On the 12 month anniversary of the go-live date, I pay a single bill for my "net" usage, but I do have to pay $4.44 per month for the privilege of being connected to the grid.

Unfortunately if I generate more power than I consume, PG&E doesn't write me a check.  The goal is to size the system so I'm safely in the  lowest bracket. It makes little sense today to generate 100% of your expected usage if you want to be tied to the grid for power at night, as no solar system can generate power that's cheaper than that lowest bracket.

The total cost of the system wasl $47,133, offset by an $11,042 rebate from PG&E and a $2,000 U.S. Federal tax credit that I can take on my 2007 tax return. Later, if I buy more panels to bump up my capacity, the PG&E rebate will be lower, an incentive for people to install systems now.

The timeline of the project was:

Complete July 2007:                        REC Solar rep and I finalize generation size, panel and inverter components
Complete July 14, 2007                   I sign contract.
Complete July 2007:                        I do site preparation
Complete August 6, 2007:               REC Solar engineer visits site for physical location check and power-grid tie-in strategy
Complete September 10, 2007:       REC Solar engineer builds physical and electrical design on CAD system
Complete September 17-26 2007:   REC Solar crew performs the installation
Complete September 26 2007:        County inspector signs off
Completed September 2007:            REC Solar works with PG&E on rebate and account switch to Net Metering
Completed October 2 2007:            PG&E signs off, puts in a new electric meter, tells me to flip switch to go live