Tesla Car Charger???

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Besoeker said:
I made no comparison the the Tesla power. That would be a bit silly IMHO. But who would drive a car that can go from 0-60 in under four seconds at a constant 55 mph?

Anyway, this a photograph of the speedometer/oddometer.



The 696 is the calculated remaining miles with the fuel left in the tank. The "B" 372 was how far I'd travelled since my last fill. And it isn't a huge fuel tank - 14 and a bit Imperial gallons.
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1000mi/14gal = 71.4 mi/gal. Do you really get that mileage?
 
wwhitney said:
watt is a unit of energy/time = power

watt-hour is a unit of (energy/time * time) = energy

Wayne
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surely yes, but we dont talk about kWh as if it was not produced or consumed, do we? maybe we do when we ask "how much does 1kWh cost me", we say "12cents for that bundle of 3.6 megajoules".

context is key, thats why kWh is typically used to mean power, because in almost every discussion its about energy produced or consumed, and typically over a period of time, because in physics you cannot produce or consume energy w/o the time variable, etc.
 
FionaZuppa said:
surely yes, but we dont talk about kWh as if it was not produced or consumed, do we? maybe we do when we ask "how much does 1kWh cost me", we say "12cents for that bundle of 3.6 megajoules".

context is key, thats why kWh is typically used to mean power, because in almost every discussion its about energy produced or consumed, and typically over a period of time, because in physics you cannot produce or consume energy w/o the time variable, etc.
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It seems to me that the larger problem is that people tend to use the term power interchangeably with the term energy too often in popular descriptions and conversations.
There is no ambiguity whatsoever in the units (kW versus kWh) nor in the use of the words power and energy by physicists.
 
FionaZuppa said:
reply to post just before this one. we must understand the fundamentals for discussions like this, otherwise its all overt the place.




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joule or eV are units of energy. Watt (energy/time) is a rate typically in the context of producing or consuming. i can in fact have Watts and not fall into producing or consuming realm, such as the flux of light energy passing through an aperture (area), so for any given time t the aperture (area) would have seen X amount of energy passing through, yet no energy is produced or consumed there (hence no power).

so, unless you want to be on the not-so-common side of the lingo, power is a rate of energy produced or consumed, and once you throw in Watts you are in "power" land.
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As you note, it can be the rate of energy exchange. The units for var also match the units for watt but in the var case, the energy is returned in the second half of the cycle so the average power over the cycle is zero. Doesn't mean nothing happened.

And kWh/h = kW. kWh is energy.
 
FionaZuppa said:
context is key, thats why kWh is typically used to mean power
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Maybe very loosely as in a "power" company or something. But when speaking of power consumption we mean the rate that is uses energy. For example how long will the battery last for some given power consumption, etc.

FionaZuppa said:
because in almost every discussion its about energy produced or consumed, and typically over a period of time, because in physics you cannot produce or consume energy w/o the time variable, etc.
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Power consumption and power delivery usually are about how big the delivery system is or now big of an energy user something is...in other words: the rate.

I do get the occasional "how many kilowatts did I use" question and that may be ok for laymen but not how industry professionals people should be talking. JMSO.
 
FionaZuppa said:
context is key, thats why kWh is typically used to mean power, because in almost every discussion its about energy produced or consumed, and typically over a period of time, because in physics you cannot produce or consume energy w/o the time variable, etc.
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I don't know about the circles you run in, but I don't know anyone who knows how electricity works who uses kWh as a unit of power. It's certainly not "typical".
 
mivey said:
I do get the occasional "how many kilowatts did I use" question and that may be ok for laymen but not how industry professionals people should be talking. JMSO.
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hmmm, you cant answer that Q w/o a tidbit more data.
 
FionaZuppa said:
thats why kWh is typically used to mean power because in almost every discussion its about energy produced or consumed
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Just because energy was "produced" or "consumed" does not mean it should be called power. Power is energy over time, the time derivative of energy. Using the term power to refer to energy leads to confusion and should be avoided. kWh is a unit of energy, not power.

Cheers, Wayne
 
wwhitney said:
Just because energy was "produced" or "consumed" does not mean it should be called power. Power is energy over time, the time derivative of energy. Using the term power to refer to energy leads to confusion and should be avoided. kWh is a unit of energy, not power.

Cheers, Wayne
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Our local POCO changed their name from Consumers Power to Consumers Energy in 1997 because they were actually selling energy, not power.
 
ggunn said:
1000mi/14gal = 71.4 mi/gal. Do you really get that mileage?
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I do.

This was the previous car. Same make and model. Same engine, same six speed manual box.

Maybatch13005_zpsa29bb8bf.jpg


And not a one off.

MPG_zpsd83c6f27.jpg


It helps that the gearing is such that it has tall gearing - 70mph, the legal limit here, comes at just under 2,000 rpm.
With the abundance of automatic speed camers here it just isn't worth the risk of exceeding the speed limit.
 
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Besoeker said:
There is no more data - kW is a measure of power, kWh is energy. EOS.
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poco charges you for kWh use, right. so how much do they charge me for my 1kW bulb ?? now you see you cant answer, and hopefully know why.

kWh is a "unity" representation of energy over a period of time. "kW" for "1 hr". does it mean time always has to be 1 hr, no, and i fact i could use 1kWh of energy in just 10min. why not just make it 2kW-30min ? its still 3.6 MJ ?

the definition of POWER is energy "produced" or "consumed". and to do that you cannot have a # that is missing time variable.
Watt is a rate (power). Watt-hr is POWER-CONSUMED (power over a period of time). the result of POWER-CONSUMED is total energy for that time period, etc.

would be much easier if things were just kept in std SI units. instead of 12c per 1kWh it could be 3.3c per 1MJ <-- makes it sound cheaper too.


and those in-dash car MPG stats, are lying to you folks. better go look at how the car ECU calculates MPG's, because unless the car ECU monitors fuel flow rate with a high sampling rate (several ways to do this, no car i know of does), the MPG thingy in your dash is a feel good meter.

i have seen others monitoring tank fills (how many gallons for each fill) and recording how many miles driven after each fill. after about 5-7 fills you'll get a rather decent reading of your MPG's.
 
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FionaZuppa said:
the definition of POWER is energy "produced" or "consumed" at a rate. and to do that you cannot have a # that is missing time variable.
Watt is a rate (power). Watt-hr is POWER-CONSUMED -- over a period of time. the result of POWER-CONSUMED over a period of time is total energy for that time period, etc.
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Fixed that for you.

For a shorter, clearer, more correct explanation, see post #79.
 
FionaZuppa said:
poco charges you for kWh use, right. so how much do they charge me for my 1kW bulb ??
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Probably about $0.10 kw-hr. On residential anyway. yes, they charge for kW-hr use (say, 720). Then they multiply that by the cost per unit (10c/kw-hr).

720kw-hr x $0.10/kw-hr = $72. Because they bill by kw-hr (multiplier of 1), 720 kw-hrs (energy) used in a month equals 720kw (power) used.

However, they are only equal because the way residential billing works. an industrial consumer would pay a higher power bill if they used 720kw for one hour of the month rather than 1kw/hr 24 hours/day for 30 days.
 
FionaZuppa said:
the definition of POWER is energy "produced" or "consumed".
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No. Power = energy / time. Full stop. Nothing needs to be produced or consumed. Example:

How much power is flowing through this wire right now? A reasonable question, and the answer might be, say, 10 kW. Nothing is being produced or consumed.

Cheers, Wayne
 
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