I retract all scoffing remarks regarding Nanosolar

Historically, I have spent a fair amount of time deriding Nanosolar for claiming that they would build a 430 MW/year solar cell factory by the end of 2007.

On the one hand, they have only 10 days to prove me wrong. I don't think they will have ramped production up to 430 MW/year. On the other hand, they are shipping a thin film module created through a printing process. That alone is an impressive feat. They win the prize, soaring above the Aonian Mount, while pursuing things unattempted yet in prose or rhyme (well, maybe attempted in rhyme).

Nanosolar is claiming module costs of 1 $/W; the US solar industry is now selling around 5 $/W.

It looks like they have beaten:

• Ascent Solar (thin film, CIGS, probaby through vacuum deposition)
• Konarka (thin film, printed, organic cells)
• Heliovolt (thin film, printed, CIGS cells)
• SoloPower (thin film, CIGS, but electroplated, not printed)
• Miasole (thin film, CIGS, but not printed)
• Solyndra (thin-film CIGS, unknown process, but they're hiring people with semiconductor process experience)

But have they hit grid parity? Maybe.

First off, $/W is a dumb metric. The W refers to the peak power, so if you buy a panel that peaks at 200 W for $800, you're paying $4/W. It's stupid, but it's easy to measure, and it's easy for journalists to quote.

A better metric is $/kWh, where kWh is a unit of energy. That's harder to talk about, because you have to talk about average production over the course of a year, which changes with location, weather, age of the panel, and so on.

The sun that hits the ground peaks around 1000 W/m^2; you might get 20% of that on average, once you factor in night, clouds, and the like.

There are about 10,000 hours in a year, so I'd expect 200 W * 10,000 hours * 10% efficiency = 200 kWh/year for a square meter. In Massachusetts, where I live, that's worth about $40 ($0.20 per kWh). (Did I get those calculations right?)

Conventional panels of around 10% efficiency are about $1500/m^2 (say, 2 Evergreen 200 W panels for $750 each?). Given panel life of about 20 years and the added expense of installation, an inverter, and maintenance, I think solar is still off from grid parity by a factor of 2-4 in Massachusetts (not counting Nanosolar).

If Nanosolar is telling the truth, they may have just hit grid parity.

DIY solar computer system, part 1

Like a lot of semi-urban computer enthusiasts who plan on living for a few decades after the onset of global warming, I have a few computers that are always on, and I wish that I could find an economically viable way of reducing the emissions generated as a side effect of the power they require. Also, when the hard times come and grid power gets flaky or drops out entirely, it would make the local warlord happy if I could use a computer to calculate optimal irrigation ditch depths, or the like. (Note to self: learn to use abacus while leisure time still exists.)

Typically, solar arrays in urban or suburban areas are tied by an inverter to the local power grid. Such inverters cost a few thousand dollars; they both allow excess power to be released to other consumers and enable the use of AC appliances without any modifications. I live in a rented property, so installing a large solar array on the roof with an inverter in the basement is not an option. But, maybe I could run a smaller array without an inverter for DC loads only.

DC vs. AC Computers, generally designed to connect to AC power, have as their first component a switching power supply that turns AC from the wall into DC. If I had a solar array, it would output DC, which would be converted to AC by the inverter, and then back to DC by each computer’s power supply, losing energy at each step. I call this "dumb"– why not just run the computers off of the DC directly?

The problem is that if you run the computers just off DC from the solar panel, the computers die when the sun is occluded by a cloud or a planet (at night, for example).

An alternative architecture The system I'm building has a 24 V DC power supply fed from the grid at its core. This will run in parallel with whatever solar panel I eventually set up. For starters, I have replaced the ATX power supply that came with my desktop with a DC/DC converter from Ituner.com. I then power that from a beautiful DIN-mount Sola SDN 10-24-100P supply that I got off Ebay for $33.00 ($45.82 with shipping).

For the DC/DC converter, I looked at the pico-PSU, but rejected it in favor of the slightly larger M2-ATX-HV.

The M2-ATX-HV had a few advantages:

The M2-ATX-HV is a bit bigger, but my PC case is pretty large, so that wasn't a concern. Including all the cables and shipping, I paid $96.40 for the M2-ATX-HV-- about $30 for the advantages listed above.

Stage 1 complete The DC system has been working reasonably well for a few weeks now. Next, I have to find a cheap way to test current sharing with a solar panel, as I don't want to commit the full $700 or whatever for a 180 W panel until I have more evidence that it will work. I'm off to the beach to start collecting sand for a little homebrewed Czochralski action.

Pope and Bacon a dangerous combo

After meeting Ubuntu zealots Alan Pope and Jono Bacon at Fosscamp this morning, I made the mistake of leaving my laptop screen unlocked within the range of these two dangerous characters while I went to the bathroom. What's worse, I left a terminal window with a root prompt open on the desktop. (I don't remember why-- I think I was installing some software earlier.) When I got back, this so-called "Pope" had blown up the font size on my terminal window and added "rm -rf /" at the root prompt.

It was good for a laugh. Unfortunately, I didn't have the poise to take a screenshot.

Later, it was revealed that the Bacon, not Pope, was the instigator, or so says Pope.

Note for the non-haX0rs in the audience (I guess that's you, mom): "rm -rf /" is a command that recursively deletes all files in your filesystem. Incidentally, I did once execute that command on an OS X server that I was maintaining a few years ago. I needed to reinstall OS X for some reason, so I tried executing the legendary command. It was pretty sweet-- various programs on the desktop crashed, services disappeared, and the machine was eventually rendered unbootable.

Anyway, I won't make the mistake of leaving my laptop unprotected when Bacon is on this side of the Atlantic.

One other interesting note from Fosscamp-- I talked to Ubuntu Linux founder Mark Shuttleworth for a few minutes after one of the morning sessions; he mentioned that the Dell Linux machines that I was so excited about a few months ago were actually Dell's idea. I had assumed that the whole Dell Ideastorm business was more of a marketing exercise, while Dell and Canonical had actually been planning Dell PCs with Linux for a while. I guess I was wrong.

Extracting files from a directory tree

Mr. Ben Polito has recently beating his drum to the tune that I am a repressed mechanical engineer who needs to release his inner software engineer.

Normally, I am too busy with preparations for the arrival of the Hard Times to spend time busting the myths spread by a sailor in the dark, but a recent problem I ran into at work gave me pause. The first version of our corporate wiki, a tweaked version of mediawiki, left a hierarchy of a few hundred directories sprinkled with around 1600 files. These files were attachments to the old wiki, and while most of them were transferred to the new wiki, some were not.

I thought to myself, "Ah! I bet I could write a little Python function that recursed through the directories, copying out the files and calling itself for each subsequent subdirectory!" This was Friday night around 10, after a day spent writing PLC code for work. It was at this moment that I thought, "Perhaps Mr. Polito has a point."

To that end, I present Pylito.