24VDC LED lighting systems

[Flyback]

Hello,

I would like to investigate the different 24VDC LED lighting distribution systems that are currently available on the market as we have to plan a large office building lighting system.

I simply cannot find the offerings which i know must be out there in this field. I wish to compare prices

Do you know of any 24VDC lighting systems.

Eg, Mains to the building, then power converter, then 24VDC distribution wires to the separate lamps.

Clearly its more efficient to do PFC in a centralised unit placed eg in the basement of the building, and then distribute DC to lamps from this point. Theres also the advantage of easy interconnection with solar power.
Obviously one cannot use >24V as it creates too much contact sparking in connectors which wears them out unless they are very expensively made.

 

[ronv]

I would like to investigate the different 24VDC LED lighting distribution systems that are currently available on the market as we have to plan a large office building lighting system.

I simply cannot find the offerings which i know must be out there in this field. I wish to compare prices

Do you know of any 24VDC lighting systems.

Eg, Mains to the building, then power converter, then 24VDC distribution wires to the separate lamps.

I think the IR losses are to high for a large scale system at low voltage.

Clearly its more efficient to do PFC in a centralised unit placed eg in the basement of the building, and then distribute DC to lamps from this point.

That's probably true if you could get around the voltage drop in the lines. But, to enjoy the savings you would need to have special bulbs without PFC correction.

Theres also the advantage of easy interconnection with solar power.

With standard AC distribution solar takes place in the normal manner.

Obviously one cannot use >24V as it creates too much contact sparking in connectors which wears them out unless they are very expensively made.

I always try to turn stuff off before I unplug it.

 

[ChrisP58]

Hello,

I would like to investigate the different 24VDC LED lighting distribution systems that are currently available on the market as we have to plan a large office building lighting system.

I simply cannot find the offerings which i know must be out there in this field. I wish to compare prices

Do you know of any 24VDC lighting systems.

Eg, Mains to the building, then power converter, then 24VDC distribution wires to the separate lamps.

Clearly its more efficient to do PFC in a centralised unit placed eg in the basement of the building, and then distribute DC to lamps from this point. Theres also the advantage of easy interconnection with solar power.
Obviously one cannot use >24V as it creates too much contact sparking in connectors which wears them out unless they are very expensively made.

Can you show any real numbers as to why a centralized PFC is more efficient than a local PFC supply? I can't imagine any reason for that to be true. Even if it were to be a few percentage points higher, the I^2R losses of the power distribution system will quickly eat up that margin.

As for switching high voltage DC, I agree that there'rs not many devices out there. But switches can be made to fulfill the need and, when made in quantity, would not be very expensive.

Besides, more and more of the new construction and retrofits these days use electronic control systems. And mosfets switch HV DC just fine.

 

[Flyback]

I think the IR losses are to high for a large scale system at low voltage.

..yes, agreed , but let me expand, we will have enough PFC'd "power hubs" near each group of lamps so that we dont have long low voltage cable runs.

you would need to have special bulbs without PFC correction

Agreed, they would be bulbs with smps led drivers in them, which run off the 24V

With standard AC distribution solar takes place in the normal manner.

....Solar panels provide you with low voltage DC which you use to charge a low voltage battery......this could then be stepped up and fed to the 24VDC distribution bus, being diode or'd into it.

....if the low voltage DC in the batteries was to be converted to 230VAC mains, then thats far more inefficient and expensive.

And mosfets switch HV DC just fine

sure, we debated over having a 200VDC bus and putting FET based circuitry in the bulbs to quell any contact sparking, but in the end it works out simple and cheaper to go for 24VDC , and use the multitude of available switches at that voltage level.......and we just need to put a power hub near to each cluster of 24V bulbs, so that cable runs at low voltage are not long.

A "power hub" is an smps converting mains to 24vdc

 

[ronv]

yes, agreed , but let me expand, we will have enough PFC'd "power hubs" near each group of lamps so that we dont have long low voltage cable runs.

Clearly its more efficient to do PFC in a centralised unit placed eg in the basement of the building, and then distribute DC to lamps from this point.

Agreed, they would be bulbs with smps led drivers in them, which run off the 24V

So once you put an IC inside the bulb PFC is only 3 diodes and 2 capacitors away and you can get rich selling your bulbs to the whole market instead of a niche.

....Solar panels provide you with low voltage DC which you use to charge a low voltage battery......this could then be stepped up and fed to the 24VDC distribution bus, being diode or'd into it.

....if the low voltage DC in the batteries was to be converted to 230VAC mains, then thats far more inefficient and expensive.

But if you use the inverter when the lights are off and the batteries are fully charged you can sell the power back to the power company.

But wait... Now you have little step down supplies for power hubs closer to the lamps so you must have batteries close to them so the solar power must be distributed to each one?????

 

[Flyback]

Clearly its more efficient to do PFC in a centralised unit placed eg in the basement of the building, and then distribute DC to lamps from this point.

yes but then the cable runs would be too long and too much i^2r loss...unless you do HVDC distribution and put spark contact circuitry in each bulb.

So once you put an IC inside the bulb PFC is only 3 diodes and 2 capacitors away

Valley fill is only about 80% PFC, so its more losses in the power system.

Now you have little step down supplies for power hubs closer to the lamps so you must have batteries close to them so the solar power must be distributed to each one?????

..Do they have to be close?...why ?....ok there'll be i^2r losses if theyre not close but who cares?.....solar is free energy from the sun so we tolerate the i^2r loss.

 

[tcmtech]

Looks like another repeat of the last thread where this all got shot to pieces.

Round two?

Why bother with sending the power to each and every unit when it can easily be grid tied into the main power systems of the building and server the same purpose and more if the lights are not on?

Now relating to PFC you have yet to ever produce any rational or realistic numbers to back up your logic or reasoning whereas in your last thread I shot it to pieces with basic math.

As far as switching DC goes once again it's not a problem over 24 volts. It's done all the time so I don't know where you are getting your reasoning and logic from over it?

Now if you are looking for off the shelf 24 VDC LED lighting its used a lot on industrial equipment so start searching there for your lights. You may be surprised at how many options you have available.

 

[Flyback]

As far as switching DC goes once again it's not a problem over 24 volts. It's done all the time so I don't know where you are getting your reasoning and logic from over it?

..if you search for switchs above 24V you will see how there are so few above 24V, and so many below 24V....24V is the demarkation point, where contact sparking damage gets too bad with DC.
Dont forget i am talking DC.

 

[ronv]

I think you have pretty well shot it down all by yourself. Think about what you are saying. We moved it out of the basement where you started because of I2R power losses.

Valley fill 80%. Not so sure:
https://www.electro-tech-online.com/custompdfs/2013/07/AN75_r0.pdf

Losses in the solar are free? I think not. Especially if you sell it back to the power company.

So lets see. We step the mains voltage down, distribute it thru a high loss system then step it back up to run some LEDs. All to try and save a nits worth of power factor?

Then we battery back it up with a solar panel and batteries in the basement that just gives away free power when the lights are off?

 

[tcmtech]

.if you search for switchs above 24V you will see how there are so few above 24V, and so many below 24V....24V is the demarkation point, where contact sparking damage gets too bad with DC.
Dont forget i am talking DC.

Well I must live in a very special part of the world and do very special electrical work because I have loads of DC switches, relays, breakers, and contactors designed for 12, 24, 48, 100, 110 and 250 VDC nominal voltages and everyone of them is to me a common off the shelf item in my lines of service work.

A quick online search brings up all of my items in vast numbers and variations of such without issue. Even Digi Key carries a good deal of higher voltage DC rated switches relays breakers and contactors with lots more available as no stock as well.

To be honest I am just finding the 24 VDC limit argument very weak to say the least. That and the PFC reasoning is just about as weak too.

 

[Flyback]

These links show that low voltage DC distribution is a serious thing............

http://www.emergealliance.org/
**broken link removed**
**broken link removed**

Well I must live in a very special part of the world and do very special electrical work because I have loads of DC switches, relays, breakers, and contactors designed for 12, 24, 48, 100, 110 and 250 VDC nominal voltages and everyone of them is to me a common off the shelf item in my lines of service work

you can get high voltage dc contactors etc, but the point is that they are far more expensive than sub 24V switches

I just went to Farnell.com and typed "switch"..."rocker"....it gave the following quantities at voltages

12V (27)
14V (10)
20V (27)
24V (54)
28V (83)
30V (6)
35V (1)
72V (1)
125V (4)
250V (1)

anything above 30V is considerably more expensive.

The above links show that in-building DC power distribution is a real concept with real advantages.

 

[tcmtech]

I guess I am not a cheap as you are.

You still have not given one bit of numbers to back up any of this as having any level of cost saving or practicality to refit any level of structure with a system like you are proposing Vs just using a grid tie inverter system to pump the solar power into the existing power systems of the building.

As far as power factor control goes very few buildings are charged for marginal power factor on their lighting systems and no homes are ever charged. Relating to power factor control in large industrial systems they already take care of it themselves and already have such systems in place.

That said even if a circuit has a poor power factor on it by code the power carrying conductors of the circuit are still going to be large enough to keep the overall voltage drop to a minimum. The typical standard is for a less than 2% voltage drop at the circuits full rated load.

Say I have a large office building with a 2 megawatt fluorescent based lighting load which is powered by a standard 277/480 VAC three phase power source and the overall system power factor is only .5 now given that it was designed correctly the overall system has a 2% voltage drop from source to end lighting loads. How much power am I wasting on line heating at that 2% drop with a power factor of only .5 to top things off and I pay 10 cents a KWh?

Now can you give me a realistic time frame for the return on investment if I switched the whole building over to your 24 VDC system along with all the additional wiring and whatnot that goes with it all while assuming that your low voltage LED system is 2 times more efficient than my present system plus has a power factor of .99 as well?

Try the math yourself this should be a rather easy one being all the relative information and numbers is there. I am curious to see what you come up with in the end and why?

 

[Flyback]

The point is that the saving when increasing the power factor comes in the reduction of reactive current between the power station and the installation....and the reduction of subsequent i^2.r losses.
Its not possible to calculate this as it depends how far away you are from the power station, and how many miles of cable there are between installation and power station.

As for your two times efficiency improvement of led over flourescent, thats very generous of you, i am not sure its really that good for leds.

The advantage of 24vdc is that you can have the emerge alliance type web structure on the ceiling and just have lights moved to where they are needed and keep all the others off. (pse see the video on the emerge alliance website.)

 

[tcmtech]

As I stated in your other thread the utility companies adjust the power factor of their systems to best match their needs for the operation of the systems so that argument is pointless.

They have automatic PFC units and capacitor banks all over their primary systems that they can switch on and off to keep the the primary systems stable at all times.

It's necessary to have some inductive reactance in the system to make things work. At a PF above .95 the system actually get very unstable and creates more problems than it solves so they try to keep the overall system tuned in to around .9 - .95 but short term dips below that are still acceptable.

What we do on our side of the meter PF wise has little bearing on what they have on theirs. The only concerns they have are with very large power users with highly variable PF loads. That's the ones they charge extra to for poor PF and expect them to handle their own adjustments.
The rest of their systems automatically keep themselves balanced to around a PF of .9 but not higher than .95.

So as I said before your overall argument for low voltage DC systems do not make sense financially or energy savings wise on the grand scheme of things. The numbers and reasonings just don't add up

 

[Flyback]

**broken link removed**

if you watch the video on the middle left you will see why low voltage dc is massively more efficient....its because you dont have to have a whole room bathed in light...you can just (very easily) shift the light to that particular spot where its needed at that particular time.......and that means mega efficiency savings.

Low voltage DC is the way forward

 

[alec_t]

you dont have to have a whole room bathed in light...you can just (very easily) shift the light to that particular spot where its needed at that particular time

You can do that with mains voltage lighting too, so the 24DC system has no clear advantage for that feature

 

[Flyback]

You can do that with mains voltage lighting too, so the 24DC system has no clear advantage for that feature

if you watch the video as shown, you most definetly cannot do that with mains voltage...... its a low voltage dc exposed track......if that was mains people would be toasted.
Thats precisely why emerge alliance use 24vdc.

 

[tcmtech]

Drop a paper clip on your exposed 24 VDC system and or grab it with a sweaty hand and see what happens.

As far as exposed live wires go I am rather sure the electrical code books did away with that concept some 70 - 80 years ago when the old 32 VDC systems started getting phased out.

There is a reason that electrical systems went to standardized higher voltages and wiring systems. People don't like having to use different power sources for every item. Every wonder why cell phones and similar items have largely went to standardized charging voltages and connectors? Compatibility and convenience.

Now relating to having one portable light VS lighting up the whole room I like most every one else am much more in favor of lighting the whole room which is also why public buildings have minimal lighting standards.

This isn't 1813 and no one wants to work by candlelight.

 

[Flyback]

As far as exposed live wires go I am rather sure the electrical code books did away with that concept some 70 - 80 years ago when the old 32 VDC systems started getting phased out.

The JLS system has 24VDC distribution with "self sealing" contacts
The emerge alliance system isnt affected by sweaty hands, and paper clips dont defy gravity.

If you watch the emerge alliance video, you see that the 24vdc system does not succumb to your failings of it....nor does the JLS system by Juice technology

 

[tcmtech]

You still have not yet justifies the costs and expenses of refitting anything over to use a system like this.

It doesn't save they utility companies a dime and so far I have yet to see anything I would call a positive gain from using it.

Its system efficiency isn't high enough to have a reasonable return on investment time due to energy savings by PF control or more efficient conversion of electrical energy to light energy plus adding all that 24VDC power circuits opposed to being able to use the already in place AC lines outlets and the like takes time and a good deal of money.

Yet according to you the only upside is having one small light you move around in every room Vs having the whole room illuminated. None of this to me sounds like any gains I want to live with either.