On Thu, Jul 02, 2009 at 10:20:07AM -0400, [email protected] wrote: > > In the same Home Power magazine (Feb/Mar 09) I copied the Battery > Equalizing essay from, there was another article about installing a PV > system in a jungle village that stated in the text: > > "Key to the plan was LED bulbs, which use less than a third of the energy > of compact fluorescent bulbs..." > > While in a sidebar it was stated: > > "Compact fluorescent lamps produce at least 50 lumens per watt, while > current available high-brightness LEDs can produce about 30 to 35 lumens > per watt. > > These contradictory statements are confusing. Can anyone out there give us > the true facts?
I've actually done a lot of research on this in the recent past (within the last year) as a business proposition, and here's the take-home: top-quality, very expensive LEDs currently win out by a narrow margin over the top-end CFLs; medium-quality CFLs win out by a large margin over the medium-quality LEDs. To expand on this, there are also LEDs currently in the testing stage - not yet in production - that are significantly more efficient than CFLs depending on the usage pattern [1] (not three times more efficient, however; that would require about 60% efficiency from the LEDs, and little beyond fireflies comes even close to that. :) Theoretically, LEDs that are currently in production compare favorably with CFLs for lighting purposes; both are quite efficient, with the LEDs winning out in a number of ways (no high start-up current; no usage pattern requirements; much higher shock resistance; much lower production cost, etc.) The problem with using them for lighting, however, has to do with three factors: luminous flux (amount of output), beam angle, and luminous intensity (which varies inversely with the beam angle.) The greatest majority of LEDs today do not produce a high-enough combination of LF and BA to satisfy the average consumer. Solutions to this range from producing higher intensity LEDs (e.g., Nichia and others), through stacking a large number of LEDs for area coverage (LED panels - very expensive but work well), to optical solutions (e.g., taillights in new model cars) that spread and focus the beam. All of these are bearing fruit; none of them have yet achieved that magical combination of commonly-available AND cheap. I expect that point to be passed somewhere within the next year or two - but it isn't here yet. [1] CFLs die quickly if cycled rapidly; turning one on and off on a 5-minute cycle shortens its life by about 85%. A minimum 15-minute on-time is recommended. -- * Ben Okopnik * Editor-in-Chief, Linux Gazette * http://LinuxGazette.NET * _______________________________________________ Liveaboard mailing list [email protected] To adjust your membership settings over the web http://www.liveaboardnow.org/mailman/listinfo/liveaboard To subscribe send an email to [email protected] To unsubscribe send an email to [email protected] The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/[email protected] The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html
