Sunday, January 22, 2012

Photonics West: SPIE's awesome conference smartphone app

..John Wallace
..Senior Editor
..Laser Focus World

So I'm here at SPIE's Photonics West 2012 in San Francisco (and will be here until next Thursday), and I'm as overwhelmed as everyone else by the number and variety of events and sessions at the show. However, I am armed with a secret weapon -- SPIE's free "SPIE Conferences" app, which I have on my Android phone (it's available for the iPhone too).

It has made all the difference. Yes, I still have the bulky print versions of the Technical Program and the Exhibition Guide. But they're staying put in my backpack while I use the SPIE app.

The app first opens to the "Conference Calendar," which lists current and upcoming SPIE conferences for the next few months, starting with Photonics West and ending (for now -- I'm sure it will be continually updated) with Defense, Security, and Sensing (DSS) in April. I select Photonics West and find the following simple menu under "Program":

--Technical Program

As you can see, the app replaces the print program and guide. But it has more: a list of the Photonics West attendees (all 13,023 of them), as well as additional info on the attendees if they're speakers.

But the most valuable feature of this app (to me) is at the bottom of the screen - the "What's Happening?" button. Hit that button and you get a list of every event, session, etc. going on at the show, all ordered based on the time they begin.

This means that at any time in the conference, without having to grope my way through a fat and unwieldy catalog, I can find just what I need. Nice indeed.

(The app can be found both in the Android Market and the iPhone App Store.)

Monday, January 16, 2012

Residential solar PV: a happy customer

Gail Overton
Senior Editor
Laser Focus World

There is nothing quite like opening your electric bill for the third month in a row and owing $0 (that’s a zero) dollars. This is the second winter season that our electric bill has been zero since we put in our 3.22 kilowatt solar photovoltaic (PV) system in the summer of 2010.

Now before I launch into a summary of panel output and cost (which are details often lacking in many articles that I read about residential solar energy systems), I'd like to describe a few unique issues that make our system especially cost effective. First of all, it is a ground-mount system--which made it less expensive to install compared to some rooftop systems. Secondly, we live in the desert southwest of California, with abundant sunshine and rarely a cloudy or rainy day, meaning that our solar output is maximized compared to many other locations in the world (and California gives generous rebates for residential systems). And third, we found a very efficient crew and an excellent installer in our area that helped us with rebate paperwork, interfaced with our utility company, and did the job over a 3 day period (including concrete footings and frame in a very rocky caliche soil). The name of that company by the way is "The Sun Works" ( out of Niland, CA.

Our system uses a total of 14 Sharp monocrystalline PV panels rated at 230 W each, bringing it to 3.22 kW and generating roughly 20 kWH (kilowatt hours; often written as KWH) each day. This means that we get roughly 7 hours of full generation out of our panels every day; pretty good considering they are fixed and do not track the sun (solar tracker equipment is fairly expensive).

With 20 KWH of generation per day, we output roughly 600 KWH per month, with the excess feeding into our grid-tied system. And because we typically consume about 300-600 KWH per month in the winter (depending on whether the heater is running or not), our bill is basically zero in the months between November and April. Our monthly consumption in the summer months--when it’s up to 110 degrees outside and the air conditioning is set at 80 degrees inside--is about 1200-1800 KWH, meaning that our highest bill of $230 per month is roughly cut in half. Utility rates at Imperial Irrigation District (IID) are some of the lowest in the country at $0.13/KWH, meaning a month with 600 KWH consumption runs about $80 a month.

So what was the price and what is the "payback" time for our system? The total price was $22,600. Sounds overwhelming and unaffordable for most people, but here is the bottom line: Immediately upon installation, one-third of that price is rebated against the total. The state of California pays the installer about $7500, bringing the amount we owed to $15,100. And then, another one-third of the total price becomes a full tax writeoff, taking the price down to $7600. But reality is harsh; because that tax benefit is not available until later, we financed the $15,100 through our Credit Union, which offers 6.75% fixed rate, 5-year solar loans. Essentially, we think of our solar-energy system as the equivalent of a five-year car payment. Fortunately, unlike a car that is sometimes worthless after five years (or worth just a couple thousand bucks), our solar energy system should continue cranking out the kilowatts for a 25-year lifetime, giving us 20 full years of zero dollar electric bills in the winter, and $100 maximum electric bills in the summer. Each year, we save about $1200 with the system, making it a 6.3 year breakeven point at a total price of $7600.

While making that payment now is not fun, I’ll be smiling broadly in just three more years when the loan is paid and the kilowatts continue to flow for years to come.

Thursday, January 12, 2012

Watching real wavefronts in slow motion

..John Wallace
..Senior Editor
..Laser Focus World

A team at the MIT Media Lab, led by Ramash Raskar, has developed the best way yet to visualize the passage of light as it hits and passes around or through objects. They use streak cameras, femtosecond-laser pulses, and a million or more repeated measurements of a stationary scene to capture the actual laser pulse as it passes through a transparent bottle, or is intercepted by an apple or other object.

Two points I’d like to make. First, is that Senior Editor Gail Overton’s news story on this will appear in the February issue of Laser Focus World; don’t miss it, as she has talked to the researchers and describes in detail how the whole thing works.

The second point is -- this is pretty amazing. They’ve created videos of wavefronts as they propagate through an everyday scene . . . and these are no simulations; they are the real thing. The colorized gray-scale photo here shows a couple of wavefronts in passage through a bottle.

(Photo: MIT Media Lab)

The bottle is perpendicular to the camera, and the pulses propagate from left to right (with no toward- or away-from-the-viewer component). I stared at this for a moment before I realized why the wavefronts look tilted -- it’s because the light from the farther-away points on the wavefront take longer to get to the camera, so these spots appear to have not progressed as far as those nearer to the camera.

This realization made me feel strangely relativistic, as if I were flying by the bottle in a spaceship at half lightspeed. (And I won’t even try to explain this.)