THE PHYSICS OF... POWER

[FionaZuppa]

does the poco bill me for work or power ?? they typically bill by kWh, which is what, work, or in physics terms, joules?

 

[FionaZuppa]

so if poco wants to maximize their bill they sample around the negative power areas ??

 

[K8MHZ]

does the poco bill me for work or power ?? they typically bill by kWh, which is what, work, or in physics terms, joules?

Actuallly, KWh is energy, not power or work.

 

[ggunn]

Power is the rate of energy transfer. Energy is never consumed, just transformed from one variety to another: electrical energy to mechanical energy or heat, etc.

Cheers, Wayne

One man's consumption of energy is another man's conversion of electrical energy to heat.

 

[GoldDigger]

so if poco wants to maximize their bill they sample around the negative power areas ??

Theoretically, POCO integrates, they do not sample.
The old mechanical meters literally integrated the instantaneous values, since the force driving the disk was proportional directly to the instantaneous product of the current and the voltage, and the motion was the integral of that force.

For peak VA purposes, I believe that POCO takes the integral over a 15 minute period and calculated the average VA, then looks for the worst 15 minute interval.
All well beyond the ebb and flow on a 1/4 cycle basis.

 

[FionaZuppa]

Actuallly, KWh is energy, not power or work.

:huh: whaaaat, this is all over the place.

work = joules = energy = kWh = power*time
kW is power (a rate of energy)

Theoretically, POCO integrates, they do not sample.
The old mechanical meters literally integrated the instantaneous values, since the force driving the disk was proportional directly to the instantaneous product of the current and the voltage, and the motion was the integral of that force.

so they dont account for the vector components of power?

 

[ggunn]

if a generator is at poco, and in my house i have a big big capacitor with no charge, poco turns on the juice to charge my pure cap, did i get energy transfer and need to pay for that? but did i use any power or transform any energy?

So, with a network of capacitors and very fast switches, could you power your home without using any real power from the POCO?

 

[GoldDigger]

So, with a network of capacitors and very fast switches, could you power your home without using any real power from the POCO?

Nope, because once he actually uses it it retroactively becomes power.

Bottom line is that the POCO is really the ENCO and bills you primarily for energy.

 

[FionaZuppa]

So, with a network of capacitors and very fast switches, could you power your home without using any real power from the POCO?

nope. so is the poco charging me for power, or work ? i dont consume power, i consume work?

my motor has a power rating of 22kWatt, how much work does it do?hmy:

 

[GoldDigger]

nope. so is the poco charging me for power, or work ? i dont consume power, i consume work?

NO. You consume energy. You may use the energy to do work. Any form of delivery of that energy over time (i.e. other than occasionally in a can) constitutes power.

Now that I think about it the gas company is also delivering energy, in the form of chemical potential energy, and could be considered to be providing power too. But their meters do not indicate instantaneous delivery rate in any way.

my motor has a power rating of 22kWatt, how much work does it do?hmy:

Your motor with a 22kW power rating does not necessarily consume any energy at all, depending on whether or not it is turned on and what the load is at any given moment. Beyond that, the work it does depends on what the motor is driving and its efficiency at that load.
If it has burned bearings and is just sitting there smoking it is still consuming energy but not doing any work at all. But POCO still bills you for it.

 

[K8MHZ]

Bottom line is that the POCO is really the ENCO and bills you primarily for energy.

Exactly.

So much so, that in fact, our POCO changed its name from Consumers Power to Consumers Energy.

 

[K8MHZ]

:huh: whaaaat, this is all over the place.

work = joules = energy

Work does not = energy, or potential energy would = potential work.

The work-energy theorem states that the work done by all forces acting on a particle equals the change in the particle's kinetic energy.

Source: Boundless. “Kinetic Energy and Work-Energy Theorem.” Boundless Physics. Boundless, 26 May. 2016. Retrieved 02 Sep. 2016 from https://www.boundless.com/physics/t...etic-energy-and-work-energy-theorem-278-6249/

So work = the change in energy, not the energy itself.

 

[FionaZuppa]

Your motor with a 22kW power rating does not necessarily consume any energy at all, depending on whether or not it is turned on and what the load is at any given moment. Beyond that, the work it does depends on what the motor is driving and its efficiency at that load.
If it has burned bearings and is just sitting there smoking it is still consuming energy but not doing any work at all. But POCO still bills you for it.

w/o the time variable the power rating means nothing. the instantaneous rate of power tells us nothing in terms of work being done, you need a delta t

Work does not = energy, or potential energy would = potential work.
So work = the change in energy, not the energy itself.

"THE PHYSICS OF POWER" is the title of this thread. the unit measure of work is joule (or eV if we go further) = energy. you name it whatever you like, i will call work as it is, energy.

if i start with 27kJ of potential energy, i then do mechanical work to an object transferring 10kJ to the object via burning of gasoline over delta t = 200sec, my potential energy remains the same, my delta J is zero at delta t = 200sec. i did work, the object did not do work, etc.

 

[FionaZuppa]

i didnt get to finish post #113. yes, from system A to system B, work results in transfer of energy from one system to another, but this does not mean the system itself has delta energy. as example, if a push a heavy block across a friction surface 27ft, when the block comes to rest it itself has delta J of zero. since i did the work by a chemical to mechanical transformation of energy, my delta J = the heat J generated by the friction of block sliding. the only true 1:1 delta J is when the work is converted into pure potential energy, eg, a lossless lift of a mass, or vice versa like a satellite in frictionless orbit.

 

[K8MHZ]

"THE PHYSICS OF POWER" is the title of this thread. the unit measure of work is joule (or eV if we go further) = energy. you name it whatever you like, i will call work as it is, energy.

I had no hand in 'naming it'. That was done by physicists. Have the Work-Energy Theorem changed and then get back to me.

Impedance and resistance are both measured in ohms, does that make them the same?

 

[K8MHZ]

Think of it this way (hopefully a decent analogy)

Energy is what is in a tank of gasoline. It can remain there indefinitely without doing any work.

It's only when the energy of the gasoline is released that work is done. The work can stop before the energy is depleted. So at any given time, it is possible to have more energy than work (like half a tank of fuel with the engine turned off), but not the other way around.

 

[FionaZuppa]

Have the Work-Energy Theorem changed and then get back to me.

.... is a mathematical relationship defined by physics, has nothing to do with the unit of work. W(joules) = Work-Energy Theorem

 

[GoldDigger]

It might help to keep in mind that energy is. Work happens.

Similarly you can transfer heat from one body to another, but a system never contains a fixed amount of heat.

 

[Carultch]

nope. so is the poco charging me for power, or work ? i dont consume power, i consume work?

my motor has a power rating of 22kWatt, how much work does it do?hmy:

The POCO bills you for the accumulation of power, which is energy.

In high power cases, they can also bill you for your highest 15-minute interval average power, which is known as demand. So if your ordinary load is 100 kW on average, and you spike your load for 200 kW for just one interval, you will be billed for 2400 kW-hrs each day, and for a 200 kW demand charge. This is especially true, if you consume during peak hours.

Work is what happens when mechanical energy is transferred through force and distance. If you have a 22 kW motor as its mechanical output rating, and you operate it 1 full hour, it does 22 kW-hrs worth of work, which is also 80 Megajoules. Note that the mechanical output rating of a motor in the US, is usually in units of horsepower (a unit that engineers of my age do not instinctively comprehend).

In thermodynamics, electrical power transmission is also understood to be called work. In that subject, the contrast is between work and heat. Work, be it mechanical or electrical, is easy to use for any purpose. Heat is difficult to re-purpose, as it can never be 100% converted to work.

 

[Carultch]

It might help to keep in mind that energy is. Work happens.

Similarly you can transfer heat from one body to another, but a system never contains a fixed amount of heat.

In general terms, this is the distinction between dynamic energy types and static energy types.

Work and heat are dynamic energy. They are the terms used for the transmission of energy from one system to another. Whereas thermal energy and kinetic energy, are static energy types. Other examples are chemical energy, electric potential energy, and strain energy. They are energy that is stored within a system.