I don't get this. Here what we are talking about is pure science and engineering and still this guy is as adamant as if he is talking about religion! One would think he would stop digging himself further once people point out the hole he is in!
Watts vs volt amps, what does power meter count?
- Thread starter Digital2k2
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Originally Posted By: greenjp
1 FMF I see you're putting a lot of effort into these posts, but I must joint turtlevette and EdwardC in setting the record straight - a generator's fuel consumption is related almost entirely to true power.
almost ?
i put the effort in to try to explain something, i gave quite a few examples none of which was repudiated.
Quote:
Remember, the "extra" apparent power is taken from and returned to the circuit every cycle resulting in no net work being performed. No work = no power = no more fuel required to produce it.
don't agree,
first where does that extra power come from in the first place?
what is correct in that statement is power taken from and returned to the circuit and no net work is performed AT THE LOAD.
when the load has low power factor it has to draw more current [power] to do the same amount of real work. it draws the extra power but does not use it and the power goes back and forth on the transmission line. it is there that it is wasted as heat.
for a single home residence it may be insignificant within the home measured behind the utility meter because those transmission lines are very short and the power draw is small,
but just like CAFE with fuel savings in automobiles you look at a single car it's nothing, multiply by everything out there and look at the totals and it is significant.... over the miles of transmission lines and total apparent power drawn.
Quote:
I have a presentation here by a PE at Progress Energy (utility company now part of Duke Energy) discussing this subject
haha ok Mr. Internet Expert.
and you have a presentation... I don't have it. I suppose you know a guy too right?
Quote:
, it closes with this:
"BOTTOM LINE ON Understanding Power Factor and How it Affects Your Electric Bill
- Very small charge with penalty most customer have no Power Factor Penalty
- None or very small savings or possible increase cost when using Power Factor Correction Devices"
this is not saying the utility meter does or does not measure true or apparent power.
again, LOOK AT THE WORDING... "most customer" or "very small savings".
Quote:
If fuel consumed was related to power factor as you suggest, these two points would not be true.
fuel consumed most certainly is related to power factor. if it was not then why bother with power factor at all ??????
Quote:
More FWIW - generator set specific fuel consumption curves are given vs. real power output, irrespective of power factor. Why do you think that is?
because power factor is based on load type and it varies. you can't spec the fuel consumption on apparent power ( which is real power x power factor ) when they have no idea what the power factor and the loads will ever be.
it's up to the user to move that power efficiently to the load and turn it into real work. if they use loads with low power factors that's the user's problem not the generators.
Quote:
Here is some good reading on this exact subject:
http://www.eng-tips.com/viewthread.cfm?qid=35570
http://www.eng-tips.com/viewthread.cfm?qid=310797
http://www.eng-tips.com/viewthread.cfm?qid=76677
http://control.com/thread/1307586278
wow, not really. those are all blogs. as a good a source of info as reading you guys above.
Quote:
ps. you really lost us with the ethanol and Bin Laden non sequiters
because you are not smart and don't think for yourself. the power company or whoever tells you something and doo dee doo you believe it without question and then when i try to explain something holy Jesus i can't imagine what Columbus went through leaving Spain in 1492.
i asked a few questions in the previous posts none of which were answered logically. give me some logical answers to what i asked, until then why should i believe anything you guys say?
Quote:
Did you tell your mommy people weren't being nice to you? Why do I suspect she's never told you you're wrong once in your life?
your awesome
1 FMF I see you're putting a lot of effort into these posts, but I must joint turtlevette and EdwardC in setting the record straight - a generator's fuel consumption is related almost entirely to true power.
almost ?
i put the effort in to try to explain something, i gave quite a few examples none of which was repudiated.
Quote:
Remember, the "extra" apparent power is taken from and returned to the circuit every cycle resulting in no net work being performed. No work = no power = no more fuel required to produce it.
don't agree,
first where does that extra power come from in the first place?
what is correct in that statement is power taken from and returned to the circuit and no net work is performed AT THE LOAD.
when the load has low power factor it has to draw more current [power] to do the same amount of real work. it draws the extra power but does not use it and the power goes back and forth on the transmission line. it is there that it is wasted as heat.
for a single home residence it may be insignificant within the home measured behind the utility meter because those transmission lines are very short and the power draw is small,
but just like CAFE with fuel savings in automobiles you look at a single car it's nothing, multiply by everything out there and look at the totals and it is significant.... over the miles of transmission lines and total apparent power drawn.
Quote:
I have a presentation here by a PE at Progress Energy (utility company now part of Duke Energy) discussing this subject
haha ok Mr. Internet Expert.
and you have a presentation... I don't have it. I suppose you know a guy too right?
Quote:
, it closes with this:
"BOTTOM LINE ON Understanding Power Factor and How it Affects Your Electric Bill
- Very small charge with penalty most customer have no Power Factor Penalty
- None or very small savings or possible increase cost when using Power Factor Correction Devices"
this is not saying the utility meter does or does not measure true or apparent power.
again, LOOK AT THE WORDING... "most customer" or "very small savings".
Quote:
If fuel consumed was related to power factor as you suggest, these two points would not be true.
fuel consumed most certainly is related to power factor. if it was not then why bother with power factor at all ??????
Quote:
More FWIW - generator set specific fuel consumption curves are given vs. real power output, irrespective of power factor. Why do you think that is?
because power factor is based on load type and it varies. you can't spec the fuel consumption on apparent power ( which is real power x power factor ) when they have no idea what the power factor and the loads will ever be.
it's up to the user to move that power efficiently to the load and turn it into real work. if they use loads with low power factors that's the user's problem not the generators.
Quote:
Here is some good reading on this exact subject:
http://www.eng-tips.com/viewthread.cfm?qid=35570
http://www.eng-tips.com/viewthread.cfm?qid=310797
http://www.eng-tips.com/viewthread.cfm?qid=76677
http://control.com/thread/1307586278
wow, not really. those are all blogs. as a good a source of info as reading you guys above.
Quote:
ps. you really lost us with the ethanol and Bin Laden non sequiters
because you are not smart and don't think for yourself. the power company or whoever tells you something and doo dee doo you believe it without question and then when i try to explain something holy Jesus i can't imagine what Columbus went through leaving Spain in 1492.
i asked a few questions in the previous posts none of which were answered logically. give me some logical answers to what i asked, until then why should i believe anything you guys say?
Quote:
Did you tell your mommy people weren't being nice to you? Why do I suspect she's never told you you're wrong once in your life?
your awesome
dude, did you even read your own links?
http://www.eng-tips.com/viewthread.cfm?qid=310797
post 7
Quote:
The words used in this thread are "significant", "not much", "little less", "not much less", etc. In fact it is something - and you never get something for nothing. You don't generate all that heat in the windings and core and transmission lines for free. It takes fuel to do it, fuel that is not producing real power but heat in all the components from the I2R losses waross mentions.
If it weren't a real problem, there would be no need for sync condensers and capicator banks located out on the distribution system. The power companies would just generate all the VARs needed at the central plants and send them across the lines to the users. The reason that they don't and that they locate devices to take care of it near the loads is that it is expensive to ship VARs. They can't afford the fuel costs.
exactly what i am saying with the perspective being power company transmitting power over hundreds of miles... turned to heat and is a loss.
http://www.eng-tips.com/viewthread.cfm?qid=310797
post 7
Quote:
The words used in this thread are "significant", "not much", "little less", "not much less", etc. In fact it is something - and you never get something for nothing. You don't generate all that heat in the windings and core and transmission lines for free. It takes fuel to do it, fuel that is not producing real power but heat in all the components from the I2R losses waross mentions.
If it weren't a real problem, there would be no need for sync condensers and capicator banks located out on the distribution system. The power companies would just generate all the VARs needed at the central plants and send them across the lines to the users. The reason that they don't and that they locate devices to take care of it near the loads is that it is expensive to ship VARs. They can't afford the fuel costs.
exactly what i am saying with the perspective being power company transmitting power over hundreds of miles... turned to heat and is a loss.
Originally Posted By: 1 FMF
dude, did you even read your own links?
http://www.eng-tips.com/viewthread.cfm?qid=310797
post 7
Quote:
The words used in this thread are "significant", "not much", "little less", "not much less", etc. In fact it is something - and you never get something for nothing. You don't generate all that heat in the windings and core and transmission lines for free. It takes fuel to do it, fuel that is not producing real power but heat in all the components from the I2R losses waross mentions.
If it weren't a real problem, there would be no need for sync condensers and capicator banks located out on the distribution system. The power companies would just generate all the VARs needed at the central plants and send them across the lines to the users. The reason that they don't and that they locate devices to take care of it near the loads is that it is expensive to ship VARs. They can't afford the fuel costs.
exactly what i am saying with the perspective being power company transmitting power over hundreds of miles... turned to heat and is a loss.
Yes I did read them. The difference between the two of us is that I actually understood them.
What's being discussed in that quoted part is the generator efficiency vs. power factor. As I said in my first post (Cummins paper linked in the "Diesel gen fuel consumption vs KW and KVA" explains this very clearly) is that the increase in temperature within the generator results in a small increase in resistance, decreasing the efficiency of the generator. This is on the order of 0.8-0.9% for a decrease in PF from 0.9 to 0.8. That's a different thing altogether than claiming that a generator's fuel consumption is dependent on apparent power vs. real power. If it was dependent on apparent power, the fuel consumed would be more like 11% greater, not 1%.
That is, the additional amps in the system do not generate an actual load (via resistance creating heat as you claim) that must be delivered by the generator. It just doesn't work that way, your continued insistence to the contrary simply proves that you don't understand.
FWIW I measure electrical power usage and generator fuel consumption in my job, but what do I know
Google "progress energy power factor electric bill", the presentation I reference will be the first hit. I suspect you will misunderstand the content of that presentation as well. If, as you assert, electric bills were based on apparent power, then there would be no power factor penalties because users' power factors would already be accounted for. In reality, they charge based on actual power (apparent power x PF) and only apply a penalty fee/surcharge to users with unusually low PF. They do of course want to maintain a higher PF than lower but it's because low PF results in oversized generators wrt kVA and distribution systems to meet the actual power load, not proportionally higher fuel consumption.
Generators are rated for a certain actual power output and associated KVA at a particular power factor. They are capable at operating at different power factors, higher or lower. If the PF is low, then they hit their amperage limit before they hit their kW limit, resulting in a voltage drop. But again, crucially, the actual fuel requirement for the generators is dependent on the actual power (with the exception of the generator efficiencies which are a smaller influence than say fuel energy content, ambient air temperature, or generator loading %).
From those same discussion threads:
"Improving the power factor will result in a very minor (essentially zero) improvment in fuel usage. The generator losses will be a little less and there will be fractionally less excitation power."
"There will be not significant fuel saving adding capacitors since the fuel consumption is directly related with the KW running load. Capacitor could reduce the KVAR but not the KW."
"Perhaps the following typical scenario could help to quantify the losses in cable do to the PF and roughly compare with the total fuel consumption witch is direct proportional to the running load KW...This scenario shows power loss in conductors exists even for ideal power factor of 100%. For lower than unit power factor, copper losses in cable increase slightly but still is a fraction of the total power consumption.
This case shows that power factor correction from 70% to 90% will only reduce the heat losses in cable (fuel consumption) in only near 2%."
"I concur with Waros and Itsmoked that the power factor has very (little) impact on the fuel consumption.
Although current increase for load power factor with the same kW at the load, The generated kvar do not require real power at the driver shaft. Therefore, not significant fuel is required other than the ancillary services and possible extra heat generated in the genset."
"Agreed Waross, I've been through this many times, an improved PF adjustment has marginal effects on the fuel consumption."
"Addition of pf correction capacitors will have minimal impact on fuel consumption.
For an isolated system such as an oil platform, the main benefits would be:
Release of additional generator capacity for production of kW instead of kVARS. This is only a benefit if you actually need the kW.
Improvement of voltage regulation.
If the generator has adequate capacity to produce the kVARS and the kW required by the system, the addition of capacitors would be hard to justify on purely economic basis."
"As dpc indicated power factor correction do not signinficantly affect fuel consumption.
Prime movers (turbies or engines) only supply real (kW) power. Since prime mover do not supply reactive or 'imaginary'(kvAR) power, reduction in kVAR do not affect fuel consuption."
etc etc.
This part here is nonsensical:
"because power factor is based on load type and it varies. you can't spec the fuel consumption on apparent power ( which is real power x power factor ) when they have no idea what the power factor and the loads will ever be.
it's up to the user to move that power efficiently to the load and turn it into real work. if they use loads with low power factors that's the user's problem not the generators."
So first you've got the equation wrong - actual power = apparent power x power factor, or apparent power = actual power/PF. Second, it's obvious you've never read a genset tech manual, fuel curves, etc. The fuel curve is independent of power factor (aside from that ~0.9%) so they don't bother accounting for it. They just establish standard conditions (fuel energy, temp, air temp, etc) and quote fuel consumed vs. actual power.
jeff
dude, did you even read your own links?
http://www.eng-tips.com/viewthread.cfm?qid=310797
post 7
Quote:
The words used in this thread are "significant", "not much", "little less", "not much less", etc. In fact it is something - and you never get something for nothing. You don't generate all that heat in the windings and core and transmission lines for free. It takes fuel to do it, fuel that is not producing real power but heat in all the components from the I2R losses waross mentions.
If it weren't a real problem, there would be no need for sync condensers and capicator banks located out on the distribution system. The power companies would just generate all the VARs needed at the central plants and send them across the lines to the users. The reason that they don't and that they locate devices to take care of it near the loads is that it is expensive to ship VARs. They can't afford the fuel costs.
exactly what i am saying with the perspective being power company transmitting power over hundreds of miles... turned to heat and is a loss.
Yes I did read them. The difference between the two of us is that I actually understood them.
What's being discussed in that quoted part is the generator efficiency vs. power factor. As I said in my first post (Cummins paper linked in the "Diesel gen fuel consumption vs KW and KVA" explains this very clearly) is that the increase in temperature within the generator results in a small increase in resistance, decreasing the efficiency of the generator. This is on the order of 0.8-0.9% for a decrease in PF from 0.9 to 0.8. That's a different thing altogether than claiming that a generator's fuel consumption is dependent on apparent power vs. real power. If it was dependent on apparent power, the fuel consumed would be more like 11% greater, not 1%.
That is, the additional amps in the system do not generate an actual load (via resistance creating heat as you claim) that must be delivered by the generator. It just doesn't work that way, your continued insistence to the contrary simply proves that you don't understand.
FWIW I measure electrical power usage and generator fuel consumption in my job, but what do I know
Google "progress energy power factor electric bill", the presentation I reference will be the first hit. I suspect you will misunderstand the content of that presentation as well. If, as you assert, electric bills were based on apparent power, then there would be no power factor penalties because users' power factors would already be accounted for. In reality, they charge based on actual power (apparent power x PF) and only apply a penalty fee/surcharge to users with unusually low PF. They do of course want to maintain a higher PF than lower but it's because low PF results in oversized generators wrt kVA and distribution systems to meet the actual power load, not proportionally higher fuel consumption.
Generators are rated for a certain actual power output and associated KVA at a particular power factor. They are capable at operating at different power factors, higher or lower. If the PF is low, then they hit their amperage limit before they hit their kW limit, resulting in a voltage drop. But again, crucially, the actual fuel requirement for the generators is dependent on the actual power (with the exception of the generator efficiencies which are a smaller influence than say fuel energy content, ambient air temperature, or generator loading %).
From those same discussion threads:
"Improving the power factor will result in a very minor (essentially zero) improvment in fuel usage. The generator losses will be a little less and there will be fractionally less excitation power."
"There will be not significant fuel saving adding capacitors since the fuel consumption is directly related with the KW running load. Capacitor could reduce the KVAR but not the KW."
"Perhaps the following typical scenario could help to quantify the losses in cable do to the PF and roughly compare with the total fuel consumption witch is direct proportional to the running load KW...This scenario shows power loss in conductors exists even for ideal power factor of 100%. For lower than unit power factor, copper losses in cable increase slightly but still is a fraction of the total power consumption.
This case shows that power factor correction from 70% to 90% will only reduce the heat losses in cable (fuel consumption) in only near 2%."
"I concur with Waros and Itsmoked that the power factor has very (little) impact on the fuel consumption.
Although current increase for load power factor with the same kW at the load, The generated kvar do not require real power at the driver shaft. Therefore, not significant fuel is required other than the ancillary services and possible extra heat generated in the genset."
"Agreed Waross, I've been through this many times, an improved PF adjustment has marginal effects on the fuel consumption."
"Addition of pf correction capacitors will have minimal impact on fuel consumption.
For an isolated system such as an oil platform, the main benefits would be:
Release of additional generator capacity for production of kW instead of kVARS. This is only a benefit if you actually need the kW.
Improvement of voltage regulation.
If the generator has adequate capacity to produce the kVARS and the kW required by the system, the addition of capacitors would be hard to justify on purely economic basis."
"As dpc indicated power factor correction do not signinficantly affect fuel consumption.
Prime movers (turbies or engines) only supply real (kW) power. Since prime mover do not supply reactive or 'imaginary'(kvAR) power, reduction in kVAR do not affect fuel consuption."
etc etc.
This part here is nonsensical:
"because power factor is based on load type and it varies. you can't spec the fuel consumption on apparent power ( which is real power x power factor ) when they have no idea what the power factor and the loads will ever be.
it's up to the user to move that power efficiently to the load and turn it into real work. if they use loads with low power factors that's the user's problem not the generators."
So first you've got the equation wrong - actual power = apparent power x power factor, or apparent power = actual power/PF. Second, it's obvious you've never read a genset tech manual, fuel curves, etc. The fuel curve is independent of power factor (aside from that ~0.9%) so they don't bother accounting for it. They just establish standard conditions (fuel energy, temp, air temp, etc) and quote fuel consumed vs. actual power.
jeff
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