I Have The Power!

A Venerable Laptop is Laid to Rest

Welcome back to the blogosphere, Matt Traum!

My HP Pavilion ZV5000 laptop kicked the bucket last week. This poor piece of portable Pentium 4 obsolesce faithfully served me for over 5 years. Our modern computer age demands planned obsolesce no more than 2 years after the purchase date; meaning my laptop remained useful to an extreme geriatric age. The thing survived an MIT doctoral dissertation. So, I was convinced that it could survive a nuclear war and that I would never need a new computer.

Through it could seemingly deflect mushroom clouds, my poor laptop was eventually done in by Microsoft updates. Although I could find no conspiracy theory on the Internet, I am convinced that those updates Microsoft keeps installing on Windows computers are malicious. Microsoft is trying to push its new Vista operating system, after all. How difficult would it be to check the operating system and age of a machine while running an update? If the computer isn’t running Vista, the update loads a bunch of clutter onto the machine, which gets worse with each update. Eventually, the machine is bogged down to a snail’s pace. This performance degradation entices the user to shell out for a new computer AND Microsoft’s new operating system. Hallelujah! 

Of course, I have no proof of this conspiracy theory; except that over the past few months every Microsoft update that finds my laptop has caused it to run ever more slowly. By Monday last week, it took my computer 10 minutes to find its own hard drive. By Thursday, boot-up led inexorably to the Microsoft Blue Screen of Death^TM. Sure, I could probably wipe the hard drive, reinstall the original software, and revitalize my relic laptop for another 6 months of service, but who has the time? It seemed like the right time for a new computer anyway. 

So, for the past week, I have been exclusively using my work computer pending the purchase of a new home machine. However, since I have a specific agreement with my employer that I will not use any university resources to produce this blog, my readers were left pining away for a new post while I purchased and set up my new home desktop machine. 

Sorry for the hiatus, but now that I’m up and running at home again, my blog posts should return to their regular frequency.

Low Liquid Hydrogen Energy Density Presents Gas Tank Challenges

Lawrence Livermore National Laboratory has claimed a world record for hydrogen-fueled car endurance. Using a modified Toyota Pruis, researchers drove 1,050 kilometers (about 653 miles) on 150 liters (about 40 gallons) of liquid hydrogen. That’s 105 km/kilogram on a per-mass basis or 7 km/liter (16.3 miles/gallon) on a per-volume basis. This feat is reported in “H₂ Going the Distance” from ASME’s Mechanical Engineering Magazine and is detailed in “Setting a World Driving Record With Hydrogen” from Science and Technology Review (S&TR).

Not surprisingly, on a per-volume basis, the Livermore numbers come out low compared to gasoline-fired automobiles. According to fueleconomy.gov, the 2008 Prius gets over 45 miles/gallon of gasoline on the highway. The number disparity becomes clearer when comparing the energy density of gasoline (922 BTU/ft³) to liquid hydrogen (270 BTU/ft³). To put the Lawrence Livermore accomplishment in perspective, if their Prius were running on a fuel with the same energy volume density as gasoline, it would have gone over 3.4 times farther, topping 55.6 miles per gallon. So, compared against the 45 mpg rating of an assembly line Prius, the Livermore hybrid is an overachiever.

Despite hydrogen being among the most energetic fuels on a per-mass basis, liquid hydrogen contains only about 29% of the energy on a per-volume basis as gasoline. So, while hydrogen fuel weighs less than tank gasoline with the same total energy, it takes a much larger volume to store. Unfortunately volume is at a premium in today’s small, efficiency-focused automobiles.

Another major liquid hydrogen drawback is the energy required to liquefy it (~ 30 percent of the energy content of the hydrogen molecule, according to S&TR). Moreover, to maintain its liquid state, hydrogen must be vented to remove latent heat and keep the tank from an overpressure explosion. So, liquid hydrogen vehicles “burn” fuel even when sitting parked and off in a driveway. While insulation can be added surrounding the fuel tank to reduce fuel bleed off, insulation eats up precious volume.

Despite these challenges, the Livermore team has made some impressive advances in liquid hydrogen fuel tank technology. Their pressure vessel is 47 inches (120 cm) long and 23 inches (58 cm) in diameter. It is smaller than previous tanks and yet stores more hydrogen due to its design: a carbon-fiber-coated aluminum vessel holds pressure and is surrounded by a vacuum space filled with reflective plastic.

Hydrogen storage technology still requires a long evolution to become commercially viable for automobiles, but the Lawrence Livermore team has provided a glimpse at a possible hydrogen-fired transportation future.

CDT Solar Provides Excellent Value for Small Panels

I scoured the gambit of solar panel manufactures looking for an affordable solar array in the 10-watt range that was lightweight, robust, and inexpensive. These panels are for use by my freshman this semester for their MEEN 1110 design-and-build project. They must work in teams to create a solar-powered winch that drags a substantial bronze statue 25 meters along a concrete surface.

This project would be difficult for advanced students, even if they were allowed to use batteries instead of solar cells to provide power to their winches. For freshman, it is going to be a battle. The project is made more challenging by extreme budget limitations for materials. If any corporate sponsors out there would like to support UNT’s solar-powered winch freshman design-and-build project, I am happily accepting donations!

With only $1,200 to buy sixteen solar panels, each with enough juice to pull a bronze statue, my choices were limited. Options included 10-watt modules from AEE Solar, Uni-Solar, SunTech, and CDT. Analyzing these products using key parameters including price-per-watt and power-to-weight ratio, the CDT-10W panel blew away the competition at $7/watt and about 3 watts/pound.

The panel’s manufacturer, CD Technology, was a pioneer in the CD-ROM industry, and in 2006, they founded their CDT Solar division. UNT now owns 17 of these panels (16 for the students and one for me to play with), and so far they are an excellent product. They perform as advertised, both under sunlight and artificial light, and have stood up to abuse from students.

For tinkerers or hobbyists interested in getting hold of an inexpensive, small-scale solar panel for projects, the CDT-10W is an excellent choice. For different applications, CDT Solar offers a range of economical solar products in a spectrum of peak-power ratings: 1, 5, 10, 20, 40, 50, 60, 80, 90, 100, 110, 120, and 175 watts.