Here is a good piece I found on EDN...
In spite of their high lighting efficiency, the cost of high-brightness (HB) LEDs for commodity applications is not low enough yet to compete head-on with older forms of lighting such as incandescent and high-intensity discharge (HID). However, certain applications can justify paying a premium for high-efficiency, long life, ruggedness, and light-color temperature control, and these applications are the sweet spot for HB LEDs.
Here’s a good example (pictured in the brochure): Solar-powered outdoor lighting for off-grid applications. This Solar Vision Pole’s lamp post is especially novel, because rather than use a standard rigid solar panel that requires additional bracing for wind shear (and can attract the attention of scavenging thieves), the pole itself is wrapped with a flexible solar panel that charges 4 gel batteries located in the base of the pole. The size of the panel and the number of batteries limits the lighting to 50W which would be a pretty weak traditional light source, but makes for a strong cool-white LED light. 6 hours of charging is enough to run the light all night.
Each pole/light/battery combination sells for about $5,000, which seems steep, but imagine lighting, say, a parking lot where there’s no access to electrical power. This approach can be a practical, low-maintenance lighting solution.
For more ideas on what the future holds for LEDs, catch Cary Eskow’s keynote speech at EDN’s free “Designing with LEDs” Workshop in Chicago next week on October 6.
This is an example of something that looks good on paper, but when one takes into account the real world, does not look so great:
ReplyDelete1) 50 watts of LEDs ... realistically that is going to take 55 watts electrical.
2) The batteries are listed as 12V, 30.5Ah and there are 4. I would place the "realistic" total power (at room temp) at less than 1500 watt hours (I am being kind). That is 30 hours at 1500 watts (not 40). At 6 hours per night, that represents about 5 days storage.
So lets go with that 50 watts * 6 hours = 300 watt hours.
The panel is 68 watts peak. Under what conditions? Is that 68 watts in its mounting condition or under a optimum solar angle? Does the charge controller use MPPT technology? If it does use MPPT, at best 90% is stored. If not MPPT, <80% is stored.
68 watts, however, the panel is mounted as a horizontal flat plate essentially. Hard to say what the wraparound is going to do.... With the exception of the far southern U.S., the peak sunlight hours for a horizontal flat plate collector is less than 3 during December. That 68 watt panel is only going to produce 200watt-hours per day. If no MPPT, then only 160 watt-hours are going to be stored.
Add in some other factors..... what i the tolerance on the panel? Is it 68 watts minimum or nominal 68 +- x%?
Panel is guaranteed 20 years, but after 20 years, it is no longer a 68watt panel but likely only guaranteed to be a 55 watt panel (80%).
1500 watt-hours is at room temp or 20-25C. What about when the temp drops? The capacity of those batteries drops. Practical implementions NEVER run a lead-acid completely down, using at most 80% of the charge. Hence not really 1500 watt hours but 1200 watt hours. Of course, that is the storage the day you buy it, but you want it to last a bit and still have the light work, so let's call that 1500 watt hours really 1200 after the end of life. So that 1500 watt hours new is really with temp, margin, life more like a 750 - 800 watt hours battery. At 50 watts, that is more like 16 hours!