> heat loss from incandescent to make them more efficient, maybe even on the order of today's LEDs seems more promising to me
This is already happening - you can apply a 'hot mirror' coating to reflect infra-red radiation back into the bulb, while allowing visible light out. This is a very old idea - here's a patent from the early 1960s which states that the basic principle was already in use:
Here's a report / puff piece from 2013 asserting that this technology is currently taking off and claiming that "by 2018 the efficiency of a hybrid halogen incandescent light bulb will exceed that of the current compact fluorescent lamps (CFL) and equal light-emitting diodes (LEDs) on the market by 2023":
This is already happening - you can apply a 'hot mirror' coating to reflect infra-red radiation back into the bulb, while allowing visible light out. This is a very old idea - here's a patent from the early 1960s which states that the basic principle was already in use:
http://www.google.com/patents/US3174067
And another which applied it specifically to coating a halogen incandescent light bulb:
http://www.google.com/patents/US3209188
Here's a report / puff piece from 2013 asserting that this technology is currently taking off and claiming that "by 2018 the efficiency of a hybrid halogen incandescent light bulb will exceed that of the current compact fluorescent lamps (CFL) and equal light-emitting diodes (LEDs) on the market by 2023":
http://www.smithmillermoore.com/Pdfs/technicalarticles/3-6-1...