3 posts tagged “renewable energy”

Link: Gravia: LED Lamp Lit by Gravity Lasts 200 Years, Never Plugs In

The Gravia lamp won second prize at the Greener Gadgets design competition.  The design is seductive: the user raises a set of weights, which then fall over a period of time to generate light using high-efficiency LEDs.  The analogy with grandfather clocks reminds us of a simpler age.  The Gravia also engages the user and directly connects the user with the act of producing light. 

In fairness, the competition was intended to encourage conceptual ideas.  The designer deserves credit for providing specifications.  The lamp was intended to produce 600-800 lumens (roughly equivalent to a 40W incandescent bulb) for four hours.  The weights fall a distance of 48" (1.2 meters).  Although not stated in the design description, other posts indicate the weights totaled 50 lbs (23 kg). 

Commercially available LEDs get about 100 lumens and therefore the lamp draws about 5 watts.  Various people have calculated that energy output of the falling weight is roughly 200 times less than the lamp power draw, even without taking into account friction and energy conversion losses.  The designer has conceded that his estimates were incorrect, although suggests that increased lighting and generator efficiency might still make the design viable.  Given that LEDs are about a 10x improvement over incandescent lights, it is hard to see what technology would deliver another 200x increase in light per watt.  Generator efficiency is not relevant, since the 'back of the envelop' calculations assumed 100% energy conversion efficiency. 

What is disconcerting is that this design sailed through the competition without anyone questioning whether the numbers made sense.  Ironically, the video of the judging suggests that one of the judges wondered about the viability of another light powered by a crank.  With increasing demand for 'green' solutions, it is incumbent on all of us to neither make problems appear worse than they are, nor solutions easier than is possible.  The first path leads to paralysis and apathy, the second can prevent us from making difficult decisions while we wait for more 'green gadgets'.

The Gravia lamp also points out the limitations of human energy.  The Human Power Plant suggests a "healthy man" can generate up to 300 watts power while cycling for 5 minutes and 200 watts for 60 minutes (output drops off rapidly at longer durations).  Again assuming no energy conversion losses, 4 minutes of 'flat-out' cycling is required to generate and store enough energy to power the Gravia lamp for 4 hours.  200 watts is roughly equivalent to 1/4 horsepower - my 90 horsepower diesel Jetta generates almost 400x more power.  It is amazing what a pair of legs can accomplish, if the distance to the store is reasonable.  Or, according to Pedal Powered Washing Machine Tests, you can almost pedal your way through a load of laundry!  Perhaps there is an opportunity for a laundro-gym franchise.

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WBCSD: German ship fights climate change with high-tech kite

"two fast-growing German companies have worked together developing a high-tech kite system to pull enormous ships across the oceans -- and save enormous amounts of money.

The 132 metre (433 ft) long MV "Beluga SkySails" will make its maiden voyage in January across the Atlantic to Venezuela, up to Boston and back to Europe. It will be pulled by a giant computer-guided 500,000-euro ($725,000) kite tethered to a 15-metre high mast. ... 

To latch onto the powerful winds prevailing well above the surface, the kite attached to the high-tech steerage unit flies up to 300 metres high to tug the 10,000-tonne ship forward, supporting its diesel engines and cutting fuel consumption.

Under favourable wind conditions, the 160-square metre kite shaped like a paraglider is expected to reduce fuel costs by up to 20 percent or more ($1,600 per day) and cut, by a similarly significant amount, its carbon dioxide emissions."

SkySails is planning a 320 square metre version for 2009, with a 600 square metre kite after that.  These larger kites could reduce fuel consumption from 30 to 50 percent.  The separation of the kite from the ship and the aerodynamics of the kite allow the ship to obtain benefit from the wind even if the ship is heading at 50 degrees into the wind.  The deployment, operation and retrieval is fully automated, and all equipment can be stowed in a remarkably small space when in port or passing through constrained waterways.  The technology is intended both for new ships as well as retrofits on existing ships.  The target is 1,500 ships by 2015. 

The SkySails site includes a number of still images and a video clip.  Although the focus is on cargo and commercial vessels as well as yachts, this technology might also be of interest to cruise ships, given the rising price of fuel and the 'greening' of the industry.  The parasail-type kite would definitely make a statement. 

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Technology Review has compiled a series of articles on global warming.

"Readily available energy technologies could be put in use today to forestall global warming. Technology Review examines some of these technologies and argues that they require not further refinement but a considered, long-term deployment strategy."

The articles describe both the causes and potential solutions for global warming.  Noticeably absent is a discussion of how we can reduce the rising demand for energy through conservation and efficiency.