Running a $12 chip at only 3w crazy? Not really if your goal is for maximum efficiency. Sure it will cost more to get there but we are all familiar with the cost, power, efficiency 'pick two of' routine. Plus there was some point in time that emitters producing 3w cost $12 each so it was done before.
for 77% efficiency? last year guys were running $50 crees at 16W (500 mA to get 66% efficiency, so its not unprecedented on the $/W scale, but still on the upper edge of obsession.
Then there is thermal management. You may not need anything. A 1212 bare running 3.1w 77% efficient should only generate 0.713w of heat which it could passively do. That is another part of the efficiency variable for the system as a whole - reduction in environmental costs.
further to this latest study i expanded my spreadsheet. we have cost per chip and efficiency of chip at various currents. we then also have heat load and monthly energy cost.
heres the result of my conclusions that will lead me to the "uber passive build" i hope to feature here
-chips cost money. thermal management infrastructure costs money - which would you rather invest in considering the inverse relationship of these two items?
-at some point, your thermal load is so reduced that your mounting infrastructure (Aluminum plate of sufficient mass and dimension) can handle the heat load by itself in lieu of more expensive heatsinks
-easy to calculate your ROI based on capital cost, efficency and electrical cost
im looking at:
"base" configuration @ 50% efficient
ongoing costs = monthly electricity bill plus i factor 10% electricity overhead for every watt of heat the chips throw out their backsides
per my spreadsheet for a 5x9 tent (chip costs only-drivers the same really as overall wattage is similar):
for me to get to 55% efficient it costs me an add'l $190 which pays itself off in under 12 mos
for me to get to 60% efficient it costs me an add'l $525 which pays itself off in under 19 mos
for me to get to 65% efficient it costs me an add'l $1300 which pays itself off in approx 32 mos
for me to get to 70% efficient it costs me an add'l $2500 which pays itself off in approx. 48 mos
perhaps as important as the economic analysis above, is the fact that if my calcs are correct, if can get to 65% efficient i can mount and cool the entire rig passively on bare 1/4" plate and im putting money into chips not heatsinks. thats saving me a few hundred dollars at least, which is knocking that 32 mo payback down to 24 mos which im down with.
Remember- chip prices are still falling dramatically. you think these chips will be worth what they are now in 2 years? not a chance. maybe 25% of what they cost now. So there is a different angle to running a few chips hard and investing in your "long-term" rig later- but that is a moving target, hard to catch that curve at the exact right time. Are you "losing" money with an "inefficient" (lower 60s vs upper 60s) rig vs sitting on the sidelines waiting for your unicorn?
