What Does it Take to Produce a Watt?

You need to find out how many joules of energy are released by the combustion of a given amount of fuel and multiply it by the conversion efficiency.

hello!

thaks for helping me but i know that 33% of the consumpt fule is change to electircal watt and the remaining of engergy is lost but i am not to much sure about this so i like to know exactly the process please help me

baktash.nasiri wrote:

"33% of the consumpt fule is change to electircal watt and the remaining of engergy is lost"

ENERGY IS NEVER LOST!!! The "unused" energy is returned to Mother Earth resulting in GLOBAL WARMING!

IN FACT EVEN THE "USEFUL" ENERGY GOES BACK TO MOTHER EARTH TO CONTRIBUTE TO GLOBAL WARMING!

I am glad for the other responses which further clarified the physics involved, especially europium's distinction that power is the rate of energy output. Multiply it by time to get the quantity of energy.

I think the important thing you are considering is how big the fire has to be to produce a certain power level. The 33% efficiency figure is about what I had in mind, too. The fuel is burned to turn water into steam under pressure. That steam turns a turbine fan which then turns an electrical generator. The generator must have voltage regulation of the AC electricity and speed regulation for frequency stability.

I can help with propane. 1 Kg of propane produces 50 Mj. Divide this by 3.6 for kilo watts.

would u please tell me why we divid it by 3.6 i dont know exactly

thanks

hello!

thanks for hellping me

ok please tell me why we have to divid 50mj by 3.6 what is exactly 3.6

ok thanks again

Sorry for causing confusion. I think it's been very well explained below. I thought you'd be up on watts and joules so I didn't explain.

I was converting Mega joules to kilo watt hours. Joules to watt hours is divide by 3600 so Mega to kilo cancels out the 1000 and leaves you dividing by 3.6.

As explained below, one joule = 1 watt second so 3600 joules = 1 watt hour (3600 seconds in 1 hour) therefore 3600 kilo joules or 3.6 mega joules = 1 kilo watt hour

The heat rate is the amount of energy (Btu) in the fuel needed to produce one kilowatt-hour (kWh) of electricity. The lower the heat rate the more energy efficient a plant is. Plants that use a steam cycle such as coal, nuclear energy, and some natural gas plants tend to have heat rates of around 10,000 Btu/kWh. Some natural gas plants using the combined cycle technology have heat rates of around 7,500 Btu/kWh.

baktash, one point needs to be clarified. A watt is not a unit of energy, but a measure of the rate at which energy is transferred (consequently, it is meaningless to speak of how many watts a kilo of coal can produce. It can produce 0.000001 watts or 1000000 watts; take your pick).

A rate of one watt for one second is an amount of energy equal to one watt-second, or joule. Watts are analagous to speed. Joules (or watt-seconds, if you prefer) are analagous to distance.

A pound (0.454 kilogram) of good coal when burned should yield 14,000 to 15,000 Btu; a pound of gasoline or other fuel oil, approximately 19,000 Btu.

I'll let you do the math (with apologies for thoroughly mixing metric and imperial units). It's late and I'm going to bed.

-e

...assuming 15,000 Btu/pound: (15,000 Btu/pound) /(10,000 Btu/kWh) = 1.5 kWh/pound, or...

...about 2.2 pounds/kilogram * 1.5 kWh/pound = 3.3 kWh/kilogram, or...

...about 3.3 Wh/g, or...

(and don't forget: 1 Wh = 3600 j. There'll be a test on Friday)

Manana,
-e

Baktash, electrone's comment that the efficiency of (most) coal-fired power plants is accurate. Here's one derivation of his figure, give or take a few percent:

I. Assumptions:
1) Typical coal-fired P.P. heat rate of 10,000 Btu/kWh
2) Energy content of coal: 15,000 Btu/pound

II. Conversions:
1) 1 kWh = 1000 W × 3600 s/hr × 1 hr × 1 J/Ws = 3.6e6 J
2) 1 Btu = 1055.05585 J

III. Raw energy content of coal, in kWh per pound of coal burned:
(15,000 Btu/pound × 1055.05585 J/Btu) ÷ 3.6e6 J/kWh = 4.4 kWh/pound

IV. Power-plant output, in kWh per pound of coal burned:
15,000 Btu/pound ÷ 10,000 Btu/kWh = 1.5 kWh/pound

V. Power-plant efficiency, in percent:
(1.5 kWh/pound ÷ 4.4 kWh/pound) × 100% = 34.1%

VI. Percent fuel energy which does not result in generated electricity.
100% - 34.1% = 65.9%

-e

One more bit of info to help you on your quest for total confusion (jeeze! Am I ever gonna get to sleep?)...

My work here is done.

-e

1 Horsepower x 0.0013404825737265415549597855227882 = 1 Watt

Whew! You almost had me there: that third '2' really threw me for a loop!

A 2?? Are you sure?? Oh my gosh - the Addedums that have to be issued now....

It depends if you wont to produce 1 Watt for a second or for 10^10 years: things change slightly. If we take as same power and energy, heaven forbid !

Depending on the type of the coal you need 2 to 5 g of coal.

Hi Guys,

Have you heard of TOU (Time Of Use) tariffs?

i.e. the cost of electricity depends on WHEN it is used. i.e. if you demand to use electricity during a power system peak, then you need to pay more. Why is this?

Another curved ball comes in the form: WHERE do you want to consume the electricity? If you want to consume it on a remote farm, then SOMEONE will have to pay for the power line just to transport it there, before you have even started to burn the coal to make the electricity.

There are two main costs of electricity:

• Energy cost: cost of coal / oil etc
• Capital cost: cost of generating station, power lines, transformers, copper cables buried in the ground etc

This all boils down to the cost of 1Watt of electricity varying across the globe, and from hour to hour.

The TOU is the power company's way of inducing high demand customers to utilize power during off-peak periods and penalizing them when they don't. An example is municipal water utilities using their high HP pumps in the late evening and early morning hours to fill their elevated storage tanks. The power plants like nice consistent, and predicatable, demand because the efficiency is highest, analogous to highway driving, and making changes even with is like steering a large ship, things don't happen instantly or even quickly. What happens otherwise is the power generation facility has to keep the steam generation boilers at a higher capacity just ready for a large "hit". If they aren't ready then a brown-out occurs. The typcial cycle is 15 minutes and can be a moving or fixed window. If the average demand exceeds a contracted limit within any fifteen minute window then the company pays a higher ¢/KWH rate for the entire billing period which can obviously result in thousands or tens of thousands of dollars/pounds/euros/etc. for that month.

Depends on how long you want your watt to last.

A watt is a pretty small unit. US DOE information shows that on average 10,297 btu's of coal is needed to produce 1 kilowatt-hour of electricity. This number allows for line losses between the power plant and the end user (so it would be less if the power was used at the plant). Hard coal (anthracite) delivers about 12,950 btu's per pound. Hence it takes .795 pounds (.36 kg) of coal to deliver a kilowatt-hour of electricity. For a watt-hour it would be 5.6 grains or .36 grams of coal

With natural gas, the fuel does not require the processing that coal does, so I would assume the amount of energy required to deliver that watt-hr would be less.

Current coal-fired power plant technology can't seem to get much more than 34.2% efficient, according to published figures for heat rates and coal energy content. That's..um..terrible, actually. On top of that we have transmission and end-user losses. Yikes!

That little 7-watt night light in the corner represents some coal miner's job security.

-e

Watt are joule talking about?

In addition to defining a watt in terms of joules it can also be defined as:

1 Watt = 1 Volt x 1 Amps

And

1 watt = 1 Newton x 1 metre / second

Watt it is Hendrik! Hey, one of my physics profs - a very old, very distinguished, very dry British gentleman (is there any other kind?) - called them jowls. Perhaps he did so unconsciously (in his own image, perhaps?) as he sure had plenty of them.

But are you certain about that 1 Watt equals 1 Volt × 1 Amp thing? I've always been told 1 Watt equals 1 Volt × 1 Coulomb/second.

And I'm certain that, at one meter per second, Newton prolly doesn't much appreciate getting kicked around like that (although I must admit that as a student, I didn't feel too sorry for him). After all, one must learn to expect that sort of treatment from first-year physics and engineering majors who are forced under the best of circumstances to suffer the rigors of The Calculus. All in all I'd say it was a fair turn of events.

-e

1 Amp should be = 1 Coulomb / second. (it better be)

The newton metre will be applicable for converting potential energy (water in a dam) to power.

So how much power does a berzerk hamster in a squirrelcage generate? My neighbor wants me to calculate his car's theoretical top end.

-e

hello!

thanks from all of u and specialy for Europium!

i find out my answer so thank u all