Reduced lighting voltage =? energy savings?

[sceepe]

I have a comercial client that has been told he can reduce his lighting energy costs by 20% by installing "voltage regualtors". Looks like the idea is to drop voltage to 114 V (the ansi minimumm).

My first reaction is "yeah right". but I need a better answer than my gut feel.

So the question to the forum is, do you buy it and why not?

Also, almost all this clients lighting is 48" T8's on electronic ballasts.

a few thoughts, is light output proportional to voltage? Do electronic ballasts have their own voltage regulators that will bring the lower voltage back up? If 114 Volts is good lets go to 100V, that must be better. Why not?

Thanks in advance for your help.

 

[southernboys]

Re: Reduced lighting voltage =? energy savings?

I may be wrong here but in theory. VoltsXamps=watts. The voltage is directly proportional to amprage. The power company charges in watthours therefore I dont see how this would lower the customers bill. Am I correct in my understandings?

 

[physis]

Re: Reduced lighting voltage =? energy savings?

a few thoughts, is light output proportional to voltage? Do electronic ballasts have their own voltage regulators that will bring the lower voltage back up? If 114 Volts is good lets go to 100V, that must be better. Why not?

Kink of yes. But it doesn't happen the way you describe it.

The regulation doesn't bring the line voltage up. It creates a voltage source on the opposite side of the regulation so that there is voltage supply that's bigger than the output voltage.

For incandescant you will save money lowering the voltage. But you'll loose more light than the corresponding savings in current.

That's physisafe.com for all your unnecessary electrical needs.

 

[bphgravity]

Re: Reduced lighting voltage =? energy savings?

Ever hear of Ohm's Law?

W = V?/R The lower the V, the lower the W.

 

[sceepe]

Re: Reduced lighting voltage =? energy savings?

Ever hear of Ohm's Law?

W = V?/R The lower the V, the lower the W.

Ohm's Law is V=I*R

W=v^2/R applies to purely resistive DC circuits. I think it was pretty obvious from my question that I was not talking about a purely resistive DC circuit.

The lower the V, the lower the W

Only if the impedance is constant. Im pretty sure that the input impedance of an multivolt electronic ballast is not independent of voltage.

Bryan,
Thanks for the brilliant reply. Very helpful

 

[sceepe]

Re: Reduced lighting voltage =? energy savings?

I may be wrong here but in theory. VoltsXamps=watts. The voltage is directly proportional to amprage. The power company charges in watthours therefore I dont see how this would lower the customers bill

You would be correct if the current were to increase as the voltage was decreased. The question is then what will happen to the current when the voltage is decreased. The answer depends on the impedance of each load. Every type of load will respond differently. Also, some electronic load impedances may be a function of voltage. For a purely resistive load, (incandescent lamp) the impedance is a constant. Lowering the voltage will lower the current and reduce the power consumed. (However, it also will lower the light output).

My question is really trying to determine what is the impedance of an electronic ballast.

 

[bphgravity]

Re: Reduced lighting voltage =? energy savings?

Sorry, didn't mean to come off abrasive. Your absolutely correct, it will depend on what type of load you are serving. I would contact the manufacturer of the specific ballast or several manufacturers of ballasts to get this technical data. I'm sure they can indicate to you if reducing the connecting voltage will effect the operation in any way.

 

[steve66]

Re: Reduced lighting voltage =? energy savings?

For an incandescent lamp, the reduced voltage will also reduce the temperature of the lamp, which will lower its impedence.

Most ballasts are made to "regulate" the amount of light and power output. Thus, if you reduce the voltage, the current draw will increase a little bit.

In both the above cases, you will now be wasting more energy on the wiring. You may save a little bit on the power bill, but like Sam said, you have lost more light than money saved.

Energy saving lamps or higher efficency fixtures and newer technology lamps (T8 or T5) would be a much better way to go.

Steve

 

[ron]

Re: Reduced lighting voltage =? energy savings?

I don't know if this was an old engineers tale (somewhat similar to an old wives tale) here in NY before the national grid, but it is said, when most of the lighting was incandescent, Con Edison (POCO) would purposely reduce source voltages from the substations to help ride through a relatively high demand in the summer. As voltage reduced, so did power consumption.

[ July 25, 2005, 01:54 PM: Message edited by: ron ]

 

[charlie b]

Re: Reduced lighting voltage =? energy savings?

Originally posted by ron: I don't know if this was an old engineers tale . . . .

Speaking as an "old engineer," I have heard that story as well, and I believe it. If you are talking about resistive loads, such as incandescent light bulbs and heating elements, then you can save money by lowering the voltage. But as physis has pointed out, your output power goes way down, more than in proportion to the lowering of voltage. The light (or heat) you get for your money goes way down as well. So it may cost less money, but you will get less than you are paying for.

One key hazard is that any motor load will run at an increased current level, and will run the risk of overheating. I think it likely that no substation will power only lights and heat, and that they will all have some motor loads. So if the utilities intentionally lowered the voltage in times of crisis, it will not have been by much.

 

[rattus]

Re: Reduced lighting voltage =? energy savings?

Not only will an incandescent lamp draw less current, hence less power, at a lower voltage, its efficiency decreases as well. Not a good idea.

Why don't they just use smaller bulbs as they do in some of the cheap motels? Some travelers bring their own bulbs!

 

[physis]

Re: Reduced lighting voltage =? energy savings?

I'm not completely sure because I really don't know how they're designed but I think T-8's use a switching supply.

What I think is going to happen is nothing.

The reason why is because the electronic ballast makes a voltage supply of say 20% above the regulated output. If you drop the input voltage by a few percent your going to effect the unregulated supply voltage by close to not at all with regard to the regulated output voltage.

It's like a voltage dam. (Except that with a dam the weight of the water effects pressure and that doesn't happen with voltage regulation)

The input current does not increase because there is no effect on the output voltage and therefore no change in output current.

The other factor that's less important is ballast power dissipation. If it were a linear supply it might be worth considering but switching supplies waste far less heat (the primary reason T-8's are better).

This is all completely dependant on my assumption that a T-8 ballast is a regulated switching power supply. I don't know of another practical method for high efficiency.

Edit: Error B

[ July 25, 2005, 05:11 PM: Message edited by: physis ]

 

[rattus]

Re: Reduced lighting voltage =? energy savings?

Sam, I would guess that the electronic ballasts regulate current. The ionized gas will clamp the voltage wherever it wants it. If that is the case, dropping the supply voltage a few volts won't change anything.

I have heard that a tub of water under the meter will slow it down. Explain that to me! Bricks on the gas meter are supposed to work too!

 

[physis]

Re: Reduced lighting voltage =? energy savings?

I'm not disagreeing Rattus, I'll just ask what you need to ionize a gas?

 

[physis]

Re: Reduced lighting voltage =? energy savings?

After thinking about it for about 5 seconds, you might be right Rattus. It couldn't hurt to regulate the current too. In either case, given the assumed efficiency of T-8's my expectation is a constant lumin output and a very tight input power range under normal conditions.

Once again, I am guessing though.

 

[rattus]

Re: Reduced lighting voltage =? energy savings?

Sam, you need a voltage spike to start the tube, then you see a negative resistance until the voltage stabilizes. I would think the systems provide maximum efficiency at the rated voltage.

Obviously, if you drop the current too low, the light goes out! Not a good idea.

 

[physis]

Re: Reduced lighting voltage =? energy savings?

Rattus, imagine if you will, both a voltage resevoir and a current resevoir comprising the output. Edit: Before the regulation.

With semiconductors we have the ability to emulate resistors with switching techniques. In other words, you can have a voltage drop without the I?R losses. If that sounds really cool it's because it is.

[ July 25, 2005, 09:03 PM: Message edited by: physis ]

 

[growler]

Re: Reduced lighting voltage =? energy savings?

Some of the time, the best thing to do is forget the technical side. I doubt that this would work anyway. There are companies out there that do fake energy audits and charge a consulting fee, they are mainly interested in selling equipment and getting paid their fee. Any energy savings will be purely accidental. They provide charts and do some fuzzy math to show the customer that by spending $400 a month he can save $800 over the next five years this looks good. Before they know it they have signed a commercial lease agreement to pay $400 a month for the next five years. There may be a couple of thousand in equipment and 8 to 10 grand for them. They get real hard to find after the transaction has taken place. The first thing to do when you hear of one of these off the wall energy saving ideas is to check out the company that suggested it in the first place. Do they have any engineers working for them . Did they incorporate in the last few months. Do the have any real office space anywhere ( not rental boxes ), any real phone numbers ( not cell ). I ran into a company that had a beautiful web site, with pictures of the corporate office, phone numbers of offices all over the US, none of it real. They took a local company for a bit of money ( probably a lot more than one ).

 

[physis]

Re: Reduced lighting voltage =? energy savings?

I was just talking with a good friend of mine the other night and the subject of business and ethics came up. Maybe we're alone on the conclusion we reached, or the belief we already held.

I feel a little uncomfortable about the amount of money I have to ask my employers to pay sometimes for some things because a lot of the things I deal with aren't really that big a deal to me. Of course I had to learn tons of stuff and I have decades of experience and there's a lot of value in that, but it's still something I'm not that comfortable with.

On the other hand, lots of people with absolutely nothing of value to offer do quite well peddling whatever form of fabricated manure and feel very good about themselves and at the same time might even have the odacity to criticize those who wouldn't behave as they do for being less successful.

Real estate agent comes to mind. These people produce nothing and believe themselves to be superior to those who own, build, and buy the commodity that they merely parasite off of.

Alright, I'm done. It just makes me feel foolish for bothering to try to be ethical.

Edit: Error B

[ July 25, 2005, 11:59 PM: Message edited by: physis ]

 

[sceepe]

Re: Reduced lighting voltage =? energy savings?

Not to help get this thread even more off topic but...

I know a few guys who bought houses, never moved in, never fixed anything, just sold them 6 months later and made more profit than I make in a year of busting my hump. It seems to violate the way I was raised, which is you don't ever get something for nothing.