CR4 Generates New Ideas

One caveat might be related to your use of "a" stepdown transformer. I assume you don't mean just one transformer/rectifier in a central location, providing a bus for the lighting in the entire house?

Here's a cautionary tale:

A family member's house was built in the 1960's and was fitted with a briefly-popular GE system wherein all of the lighting fixtures (inside and out) are switched via low-voltage latching relays, located in a central panel in the basement. All of the wall switches throughout the house are momentary ones, and the power is provided by a lone transformer up in the attic.

Besides the (long ago discontinued) relay and switches that have failed over the years, one day that transformer in the attic is going to die and with it every single still-working light fixture.

So you might want to consider a few independant zones of lighting. Or some kind of backup power supply.

A few transformers on several circuits is not a problem as long as the individual components are off-the-shelf (inexpensive). I thought about a small device that your lamp would plug into and in turn plug into the wall receptacle, but a "light bulb" type LED device would need to be designed. The light bulb shape would raise the cost. Since LED's are so small and inexpensive, using many would provide adequate light without major expense.

Not trashing the idea - but how about an experiment? Go into a dark room with one of these flashlights, & turn it on. Then try to work out how many you'd need to light the room equivalently to a 60W incandescent or an 11W compact fluorescent. If it still looks viable, then maybe you should run with it.

I think my approach would be to provide task lights instead of area light. There really isn't any good reason to light an entire area. It's just wasteful. Where an area needs to be evenly lit, as in a commercial application, the Panasonic LED lamp would be employed.

Good point.

Could be worked out pretty easy, done a simple one below and the LED's seem to be the most energy efficient. Ie how many lumen's they produce per Watt of power.

There are a few thing's that could effect this , changing the AC to a suitable form LED ,could use more power than it saves . and what part of the light spectrum the lumen's are in.

60W-1170 Lumen's filament bulb (from first link)

20W -1200 Lumen's CFL ( energy efficient) (from first link)

12W-1200 Lumen's LED (from wiki)

so just divide the 12W by how much power each LED uses and you have a rought number you would need.

High efficiency - LEDs are now available that reliably offer over 100 lumens from a one-watt device, or much higher outputs at higher drive currents (from wiki)

http://oee.nrcan.gc.ca/publications/infosource/pub/home/Household_Lighting_Section5.cfm?attr=4

http://en.wikipedia.org/wiki/LED_lamp

I am not against such an idea. In fact I am quite fond of LED devices.

However, I am cautious. What is the purpose? To be more efficient and save energy I suspect. Or is it to reduce carbon foot print.

When analyzing the pros and cons one thing that needs to be taken into account that is often neglected is the actual cost (energy and carbon footprint) of all the new stuff that is necessary to make the change. This would include the transformer(s), rectifiers, lighting fixtures new bulbs, etc. Generally when those are taken into account, the savings isn't so beneficial and in some cases can result in more dire consequences (outlawing of the simple incandescent bulb comes to mind).

It may be possible to come up with an optimized design for certain situations, but rooms in houses serve numerous functions. My family room is used for watching TV (occasionally), general conversation with guests and/or family members, playing games, reading, working on kids projects, working on projects for my boss (wife). The same goes for the dining room (minus watching TV) and the living room and the Den, and the kids rooms (all minus TV). Good lighting is necessary, but the most flexible/robust solution is probably not the most energy efficient. I am not opposed to a little lifestyle change to be more energy efficient, but by pushing down my power bill I may actually increase the time it takes me to do things or how well they get accomplished.....in the end, is that really more energy efficient?

Another concern I have with such project would be if the government caught wind of it, then instead of individuals converting over to such a system as their existing lighting system fails, it would be mandated upon us in a move to reduce the carbon footprint (while perhaps actually increasing it initially) and save the economy. Sorry, I couldn't resist the political rant.

I've looked at this in some detail. The best 20 ma LEDS I can find (so far) are the CREE LC513FWH1-60Q-A0-00001 they are 60° (viewing angle) 4000 milli Candella.

You would need about 400 ($100 to $200) of these to produce the same amount of light as a 100 Watt incandescent.

I believe the actual lighting provided would be superior, so it probably wouldn't be too difficult to persuade someone with money that they needed the latest technology.

This will become more and more viable as LEDs get cheaper/better.

The idea looks promising.

If your area has significant air pollution, trouble may occur due to corrosion of the switch contacts. 110 or 240V will still function through a corroded contact, 12V may not.

I once had considerable problem with a complex materials handling system which used 24V relays for a lot of the switching. It was located on a cliff top straight above the sea and was also in a sewage treatment plant.

Every time we wanted to start the thing we had to clean all the contacts! This was a real problem during commissioning, although much less so when in service.

What about using one 75 watt fluorescent fixture with a series of fiber optic cables bringing the light to the other rooms of the house, or work area. The ends of the fibers could be shaped to direct the light to a focused area for task lighting, or shaped to provide more of a wide angle light pattern for general lighting.

Is it workable? Yes.

Is it practical? Not really.

The cost of some projects just make them impractical.

When the cost of incandescent bulbs has become so cheap, we tend to avoid changing to anything more efficient until we are prodded by something. Just my opinion.

use a 12V car battery 60 to 100 W of solar panels and an inverter per lighting ring, use CFLs @ one per room, have a change over at your distribution board in case of inverter or battery failure and you have free lighting with all items available off the shelf and no disruption to your house wiring?