LAPTOPS FOR ALL

Powering and networking small systems in areas without electricity isn’t a brand-new problem [“The Laptop Crusade,” April]. When there were no telephone lines in outback Australia, people used HF radio. There was, of course, no electric power until quite recently.

In 1929, a guy named Alfred Traegar devised the “pedal radio,” which generated power by means of disused bicycle parts and later the planetary gears from a Model T’s steering. Traegar is hailed to this day as the man who brought communications to the vast and rural outback. The pedal radio system was also promoted by John Flynn, moderator of the Presbyterian Church, because it complemented his Flying Doctor aerial medical initiative. You can find more details about Traegar’s pedal radios in Ion L. Idriess’s biography of Flynn, Flynn of the Inland.

Schools in disadvantaged areas anywhere can rig something similar. Youngsters could take turns pedaling in relays and could charge one or perhaps a whole bank of laptops.

Ian Findlay

IEEE Member

Sydney

POWER IN THE HOME

I really enjoyed “A Power Plant for the Home” [News, April]. In it, reporter Prachi Patel Predd writes that “micro-CHP growth might be slower in North America than in Europe and Japan because many of the same homes that require a lot of heating in winter also run electricity-hungry air conditioners in the summer.” But this is a problem that could probably be solved through the use of absorption-type heat-pump air conditioners. For example, Honda recently introduced what it calls the world’s first ultrasmall ­absorption-type heat-pump air conditioner for home use. It uses neither electricity nor Freon. Honda says the unit uses air as the cooling medium and is suited to cold climates as well, because it can also work as a heat-pump heater.

I have seen natural gas–powered absorption air conditioners. They are quite efficient. With a bit more development, perhaps they could even be designed to use heat from the engine to reduce the natural gas burned directly in the air conditioner.

Jose Sousa

IEEE Member

Broomfield, Colo.

Some recent comments in IEEE Spectrum on solar and other alternative-energy systems have overlooked payback considerations. In 1973, I was part of a small team working at CBS Laboratories on ­gallium-arsenide solar arrays. We were led by Denis Gabor, who had received the Nobel Prize for physics in 1971 for his work that led to holography. Gabor was a boyhood friend of Peter Goldmark, who headed the labs, and Goldmark asked Gabor to suggest possible alternative-energy approaches.

Early on, Gabor asked: “How long did the system have to operate to recover the energy required to fabricate the system and supporting infrastructure?” Although the answer—18 years with the system operating somewhere near the equator—became the kiss of death for this particular program, Gabor had opened the door to evaluating the payback times of these projects using financial models. By the way, Gabor also envisaged direct conversion of the solar array’s output into hydrogen, which would be stored at very high pressures in flexible bladders on the seabed.

Terence Roach

IEEE Life Member

Fairfield, Conn.

HOT CARS

For the Honda FCX/Concept car, claimed fuel efficiency is “435 km from 171 liters of hydrogen, stored at 350 atmospheres” [“Top 10 Tech Cars,” April].

I would believe a claimed fuel efficiency of 435 km from hydrogen stored at 350 atm and occupying only 171 liters of space in high pressure ­(composite?) tanks. This would be 59 850 liters of hydrogen, since gas volume is measured at standard temperature and pressure (25 °C and 1 atm). Thus, they are going to use 2672 moles of hydrogen, (a little less than 5.4 kg) to go 435 km, or about 1.25 kg/100 km.

Pretty impressive. But not 2.54 kilometers per liter of hydrogen!

Doc Dougherty

IEEE Member

Playa del Rey, Calif.

The author replies: Nice catch! Thanks for reading so closely.

CORRECTIONS

In “Top 10 Tech Cars” [April], the description of the Tesla Roadster should have noted that it is adapted from a Lotus-designed and engineered “donor” platform, which Lotus uses in its Elise roadster. Tesla’s engineers worked closely with Lotus’s engineers to adapt the platform, and they did substantial reworking to accept a totally different power plant and a completely different body in carbon fiber rather than fiberglass. They also extended the wheelbase. The Tesla is built at the same Lotus plant that builds the Elise.

In “The Laptop Crusade” [April], the number of schoolchildren in Nigeria was incorrectly stated; Nigeria has 45 million school-age children; at any one time 4 million are at the same grade level.Ed.