OT, any electricians or electrical engineers on here? i have something that

[Bill R.]

i'm wondering about... with a 120v transformer thats rated at 100 watts 12v and i have 5 20 watt 12v mr16 bulbs being run by it... If i substitute 1 watt led's with mr16 bases with the power consumption drop or does the transformer consume 100 watts regardless of the load on it ... thanks

[tim]

Dear Bill,

I'm not sure if this helps but, Volts x Amps=Watts. Therefore, since you are using a transformer and voltage is fixed, the only variable in the equation is the amp draw of the bulbs. Your old bulbs drew about .166 amps. Your new ones draw .0083. You could have 100 led's.

The Transformer is is just 2 coils, that transmit elec. magnetically as opposed to mechanically. There is no conductive connection between the circuits, which may be at arbitrary constant potentials. Only changes in one circuit affect the other. When a transformer is on, but no power is drawn, the draw is equal to the resistance of the coil. This is dissipated in the form of heat. There is some loss to the system due to the resistance of the coil material and the ferromagnetic material.

Long story short, your transformer will draw current at rest, but not 100 watts. Otherwise it will pull whatever amperage it needs up to its rated capacity (where there's usually a fuse).

BTW I'm not an electrical engineer so ne1 feel free to correct.

-tim

[Tiger]

The consumption drops 95 percent. The transformer only provides power according to the load of the system. Although there are some energy loss at the transformer due to the heat but it is a minor loss.

Just make sure the LED can handle 12V power or otherwise it is toast.

[Kalevera]

Good stuff! Wow, this makes me want to replace all of the interior lights in my car with blue high intesity LEDs.

[Bill R.]

the owner of a local lighting company was telling me that it would consume 100watts regardless of the load on it up to the maximum 100watts that the transformer was rated at...I have some low voltage halogen mr16 lights in my hallway that i wired up with a 100w transformer ,running the maximum allowed 5 lights at 20watts mr16 bulbs each, so in theory i'm lighting my hallway with 100watts total... lately i've been looking at some of these 1,2 and 3 watt led mr16 replacements that supposed to put out quite a bit of light with a very long bulb life.
So i thought i would try a couple out in the hallway and if they work well wire up a number of lights in my house with them and see if i can't drop my total power consumption a good bit..








The consumption drops 95 percent. The transformer only provides power according to the load of the system. Although there are some energy loss at the transformer due to the heat but it is a minor loss.

Just make sure the LED can handle 12V power or otherwise it is toast.

[danzee]

The owner of a local lighting company is patently wrong. What the other guys here are telling you is substantially correct. The transformer will draw some small current plus what is needs to support the load you put on the 12V output.
Just be careful how much you UNDERutilize it. The unloaded "12V" output voltage will be higher than the "12V" output when it is fully loaded. Since the automotive lighting is designed to withstand at least 14V , I don't think you will have a problem at all.
I assume you are going to put some kind of rectifier after the transformer. The LEDs will either burn up or give lsomewhat lower light output on AC. The rectifier will drop the voltage slightly as well so you'll be back near 12V.
If what you meant when you said "transformer" is really something that puts out 12V DC (power supply, then the rectifier is built in and you are good to go.

[Javier]

in the board are telling you the truth, transformer will pass only the required power, based on the load, and will draw from the system this power plus looses that won't ever be significant. Even more, with low load in the system, the copper loses in the windings will be very low, so transformer will also run very cool, yes voltage will rise almost to no load value, but doubt the transformer regulation (Vloaded-Vunloaded)/Vunloaded will be over 5%.

I'm curious. What are this LED bulbs you are talking about? Are them suitable for AC voltage (alternating current), as were the former bulbs? A LED is a DC component, current will flow only in one direction, and when it does, it will generate light and have a voltage drop of about 1.4 volts, on the other hand, they can not withstand too much reverse voltage. If you take an ordinary led, and put 12 Vac on it, it will fry immediately. Guess your LED bulbs are some kind of LED array, with both ways led's series so to use current flow in both directions (as AC means).

Your only requisite then, would be to be sure your new bulbs are OK for 12 Vac operation, and you can put as many bulbs as you want up to 100 Watts. Will expend only the installed wattage.

Javier

[Bill R.]

get to the luxeon 1 watt wide angle, that and the 3 watt are the ones i'm considering to replace some existing 20 watt halogens, I'm even thinking about buying some of these for a pv panel and storage battery system..
led mr16 lights
(http://www.superbrightleds.com/cgi-bin/store/commerce.cgi?product=MR16)






in the board are telling you the truth, transformer will pass only the required power, based on the load, and will draw from the system this power plus looses that won't ever be significant. Even more, with low load in the system, the copper loses in the windings will be very low, so transformer will also run very cool, yes voltage will rise almost to no load value, but doubt the transformer regulation (Vloaded-Vunloaded)/Vunloaded will be over 5%.

I'm curious. What are this LED bulbs you are talking about? Are them suitable for AC voltage (alternating current), as were the former bulbs? A LED is a DC component, current will flow only in one direction, and when it does, it will generate light and have a voltage drop of about 1.4 volts, on the other hand, they can not withstand too much reverse voltage. If you take an ordinary led, and put 12 Vac on it, it will fry immediately. Guess your LED bulbs are some kind of LED array, with both ways led's series so to use current flow in both directions (as AC means).

Your only requisite then, would be to be sure your new bulbs are OK for 12 Vac operation, and you can put as many bulbs as you want up to 100 Watts. Will expend only the installed wattage.

Javier

[Javier]

You will have a better huge advantage, LED lamps will produce quite less heat than former halogens, so ambient temperature will be cooler with this LED lights.

This is a handicap of the halogen lights in hot seasons.

What didn't see were references to lumen (light) intensity, how they compare to halogens? If comparable, fell soon halogens will RIP.

Javier

[Bill R.]

star V and its 5 watts and 120 lumens output. But from people i've talked to that have seen them they say that the 120 lumens number is misleading. that it actually looks like it puts out a lot more light than that to them
Luxeon site (http://www.lumileds.com/products/line.cfm?lineId=3)








You will have a better huge advantage, LED lamps will produce quite less heat than former halogens, so ambient temperature will be cooler with this LED lights.

This is a handicap of the halogen lights in hot seasons.

What didn't see were references to lumen (light) intensity, how they compare to halogens? If comparable, fell soon halogens will RIP.

Javier

[Tiger]

Wow... I can see electric bill drop tremendously with these bulbs... Speaking of which... easiest energy saver for alot of us folks is simply swapping out most commonly used table lamps, ceiling lights with flourescent bulbs... they really do knock down electric bill big time while putting out more light than they are rated with equivalent regular incandescent bulbs.

In some area, such as bedside table lamps... you might want to keep them regular bulb as they are instant light and warm light easier on our eyes to read. But these specific lamps are short term use... meaning we turn them on and off unlike the rest of the house which may be on all the time.

[Hector]

for that. You can get a flat plate panel of polycrystalline Si solar cells and pay about $6/Watt installed but soon this is going to change by using GaAs-based compounds which produce more Watt/cm^2 than any other solar cell technology. I believe AZ (as well as CA) have special incentive programs to get rebates for so much green power that is generated at the residential/comercial scale. I also think there is a mandate in AZ that so much electricity be produced by renewable energy but I think PV is the hot ticket. I'll be in Scottsdale, AZ in May for a PV conference on solar energy. Arizona Public Sevice has some of our product tied into their power grid. These are exciting times...!!!!

[Bill R.]

4.50 a watt, my next door neighbor just put up 40 160watt bp panels on a special program that the local utility offers, it was 28k for the cost of the entire system but they had a bunch of extra stuff that wasn't part of the normal package. So far the average output is only about 5200 watts during most of the day.









for that. You can get a flat plate panel of polycrystalline Si solar cells and pay about $6/Watt installed but soon this is going to change by using GaAs-based compounds which produce more Watt/cm^2 than any other solar cell technology. I believe AZ (as well as CA) have special incentive programs to get rebates for so much green power that is generated at the residential/comercial scale. I also think there is a mandate in AZ that so much electricity be produced by renewable energy but I think PV is the hot ticket. I'll be in Scottsdale, AZ in May for a PV conference on solar energy. Arizona Public Sevice has some of our product tied into their power grid. These are exciting times...!!!!

[Tiger]

Wow... I didn't realize how much power it could put out... what was their electrical bill like? Even though they spent $28,000

[Bill R.]

going is around 350 to 400 and during the winter they probably don't have a 50.00 electric bill. They told me they knew the payback would never happen they just wanted a solar system, since they had always been interested in it.There's a tax credit on it and they have a buyback agreement with the utility so that any power they don't use during the day makes the meter run backwards and actually credits them. The only thing is their bill can't be less than the standard service charge which is something like 7.50 a month. So even if they generate more than they use the utility gets that extra power for nothing.







QUOTE=Tiger]Wow... I didn't realize how much power it could put out... what was their electrical bill like? Even though they spent $28,000[/QUOTE]

[Tiger]

Mmm... they must have set their A/C super cold... did you have to wear a jacket in their house at summertime? ;)

Their bills sound normal as in regular leaky old house bill... Unless they have a super sized home also.

[Hector]

that's not too bad. Here in CA, usually it costs about $8-$9/W before rebates but there are some that will install a system to as low as $7 but you'd have to worry about the quality... The CA Energy Commission used to give a 50% rebate based on PTC (PV USA Test Condition) power but now it has gone down to 40% because many are jumping on the PV bandwagon and they are running limited on their rebate funds. They also have a 7.5% state income tax credit if one qualifies. I've always had a problem with how the rebates are done because when you buy a system, you pay for this based on STC (Standard Test Conditions; which are lab test conditions of panels based on 1000 W/m2 of insolation and 25 C) but the rebates are based on PTC, actual operating conditions. So if you buy, say, a 3 kW system, you actually produce 2.5 kW due to losses from heating, insolation less than 1000 W/m2 and such and you rebates are based on the 2.5 kW. Pretty much the same thing with your neighbor. He paid for 6.4 kW but is getting 5.2 kW. It's better than nothing!! Anyway, enough of the venting.

There is a local guy who will sell you a 3 kW flat plate system for $14,759 but after the rebates you'd pay $8815. It's a tempting offer. 3 kW is enough to power a small home.

I'm personally holding out for a concentrator dish. By concentrating the sun's flux by 250 to 500 times, you have less real estate of PV material and you can also generate hot water so that the gas heater doesn't have to work as hard. Downside is that the system is a little more complex. You'd have to have a tracker, cooling system if you don't want to generate hot water, and safety could be an issue. We will see.



4.50 a watt, my next door neighbor just put up 40 160watt bp panels on a special program that the local utility offers, it was 28k for the cost of the entire system but they had a bunch of extra stuff that wasn't part of the normal package. So far the average output is only about 5200 watts during most of the day.

[Tiger]

This is very interesting Hector... I thought a 5kW system can make a serious dent on average home electric usage... but as Bill pointed out what he thought the neighbor's common bill... it is not any different from all the bills I saw on regular house.

I renovated a duplex... everything new and energy effiecient except gas boiler that is made in 1970... supposedly 80% efficiency back then but everyone think it is about 65%... The end result was a bill of combined electric and gas never exceed $130 a month. Everyone else on block average anywhere between $200 to $300 a month combined. 1200 sq. ft living space.

Now, I am thinking... if these units have solar power... boy... how much lower can it go along with LED lightbulbs? There would always be gas bill... Now if I were to live there... it would be an investment... but rental property? No way... I'd have to charge for solar power usage... hehehe.

[Bill R.]

actual total of the panels is 6.4 So far without the system really getting going they are already exceeding the 4k guaranteed output.
its a 3500sq.ft house with a basement, built in 1931 so its not terribly efficient, this year i'm sure it will do a lot better, they got at least one a/c unit this year thats a much higher seer than their old ones. I think that part of the reason that its as cheap as it is here is as you've stated they have to generate x amount of power with solar each year and until they are they'll be offering deals










that's not too bad. Here in CA, usually it costs about $8-$9/W before rebates but there are some that will install a system to as low as $7 but you'd have to worry about the quality... The CA Energy Commission used to give a 50% rebate based on PTC (PV USA Test Condition) power but now it has gone down to 40% because many are jumping on the PV bandwagon and they are running limited on their rebate funds. They also have a 7.5% state income tax credit if one qualifies. I've always had a problem with how the rebates are done because when you buy a system, you pay for this based on STC (Standard Test Conditions; which are lab test conditions of panels based on 1000 W/m2 of insolation and 25 C) but the rebates are based on PTC, actual operating conditions. So if you buy, say, a 3 kW system, you actually produce 2.5 kW due to losses from heating, insolation less than 1000 W/m2 and such and you rebates are based on the 2.5 kW. Pretty much the same thing with your neighbor. He paid for 6.4 kW but is getting 5.2 kW. It's better than nothing!! Anyway, enough of the venting.

There is a local guy who will sell you a 3 kW flat plate system for $14,759 but after the rebates you'd pay $8815. It's a tempting offer. 3 kW is enough to power a small home.

I'm personally holding out for a concentrator dish. By concentrating the sun's flux by 250 to 500 times, you have less real estate of PV material and you can also generate hot water so that the gas heater doesn't have to work as hard. Downside is that the system is a little more complex. You'd have to have a tracker, cooling system if you don't want to generate hot water, and safety could be an issue. We will see.

[Bill R.]

boiler at the focal point and used superheated steam to run a 8kw turbogenerator or they could use it to store compressed air in cylinders to power the turbogenerator during periods of no sun..









that's not too bad. Here in CA, usually it costs about $8-$9/W before rebates but there are some that will install a system to as low as $7 but you'd have to worry about the quality... The CA Energy Commission used to give a 50% rebate based on PTC (PV USA Test Condition) power but now it has gone down to 40% because many are jumping on the PV bandwagon and they are running limited on their rebate funds. They also have a 7.5% state income tax credit if one qualifies. I've always had a problem with how the rebates are done because when you buy a system, you pay for this based on STC (Standard Test Conditions; which are lab test conditions of panels based on 1000 W/m2 of insolation and 25 C) but the rebates are based on PTC, actual operating conditions. So if you buy, say, a 3 kW system, you actually produce 2.5 kW due to losses from heating, insolation less than 1000 W/m2 and such and you rebates are based on the 2.5 kW. Pretty much the same thing with your neighbor. He paid for 6.4 kW but is getting 5.2 kW. It's better than nothing!! Anyway, enough of the venting.

There is a local guy who will sell you a 3 kW flat plate system for $14,759 but after the rebates you'd pay $8815. It's a tempting offer. 3 kW is enough to power a small home.

I'm personally holding out for a concentrator dish. By concentrating the sun's flux by 250 to 500 times, you have less real estate of PV material and you can also generate hot water so that the gas heater doesn't have to work as hard. Downside is that the system is a little more complex. You'd have to have a tracker, cooling system if you don't want to generate hot water, and safety could be an issue. We will see.

[Hector]

of the system you select and the number of loads you have running during the day, it is actually possible to watch the power company's meter run backwards as Bill stated. Conversion efficiency is the key. I think many resort for the latest in state of the art patented high efficiency polycrys. Si solar cells from Kyocera. I believe their conversion efficiency is 15%+ considering that, in general, the quality of this polycrys. Si is poor.


This is very interesting Hector... I thought a 5kW system can make a serious dent on average home electric usage... but as Bill pointed out what he thought the neighbor's common bill... it is not any different from all the bills I saw on regular house. Living on a gas bill would be a dream for many.

I renovated a duplex... everything new and energy effiecient except gas boiler that is made in 1970... supposedly 80% efficiency back then but everyone think it is about 65%... The end result was a bill of combined electric and gas never exceed $130 a month. Everyone else on block average anywhere between $200 to $300 a month combined. 1200 sq. ft living space.

Now, I am thinking... if these units have solar power... boy... how much lower can it go along with LED lightbulbs? There would always be gas bill... Now if I were to live there... it would be an investment... but rental property? No way... I'd have to charge for solar power usage... hehehe.



Yep, there are all kinds of scenarios that people get into to power up various devices with solar electricity/solar thermal. Sandia, for example, is working on a 150 kW/day Sterling engine that can provide power to more than 40 homes.

http://www.sandia.gov/news-center/news-releases/2004/renew-energy-batt/Stirling.html

I have a colleague who is DIYer and he is into generating clean energy as a hobby. He has a stack of ten 12 V car batteries in his garrage. I think he told me that his main bus cranks out 208 A of juice!!! He has a flat plate array that powers the batteries when they are low and relays the extra power to the home when the batteris are charged. The batteries are there in case of the emergency which he hasn't had one yet.

The thing with a concentrating dish is that they are mainly used at the commercial/utility level. The very few who have dishes in their backyard require special permits that are tough to get at times. Others go through illegal channels, such as the so-called "guerilla solar people" who generate energy for personal profit without acquiring proper permits and without going through the energy commission. But I'm casually campaigning to get dishes out for residential use. This is a possibility considering that the USA has the world-record efficiency for converting sunlight into electricity at 37.3% using GaAs-based cells in a dish!!! Compare to 15% flat plate and 22% from a concentrating dish both with Si.

The sad part of all this is that although we have the most bright minds who excel at technical excellence, we still lag Japan and Europe as far as selling/installing PV. There is a drive between National labs and Corporations here in the US to get the cost down to $2 to $2.5/W installed so that we can be at the top of our game, and be competitive. Then, I think PV will explode... and every home will reap the fruits... yeah sounds corny but is a great vision.




boiler at the focal point and used superheated steam to run a 8kw turbogenerator or they could use it to store compressed air in cylinders to power the turbogenerator during periods of no sun..