Expert: W.A. (Bill) Stevens - 3/7/2009

Question
QUESTION: Dear Sir Stevens,

Please help me.This is the data I am supplying to you from one of your earlier answers to a question.
"A 1 MW generator operating at full capacity for 1 hour will generate 1 megawatt-hour of electrical energy.
If the 1 MW power plant has a heat rate of 10,000 Btu per kilowatt-hour, which is equal to 10,000,000 Btu per megawatt-hour, it would use 10 million Btus of fuel per hour at full capacity."

What Megawatt is 1 megawatt hour? 1 megawatt hour is what BTUs?

Can 1 Megawatt of Electricity be generated in a hours' time. Although I don't have much idea but till now I am in belief that a 1 MW capacity plant operating at full load will generate 1 MW of Electricity in 1 year so the breakeven point(machineries cost etc) would come in about 4.5 years.
But if 1 MW hour of Electricity, 1 MW of power is generated in only 1 hour, I belive the breakeven could come in only 1 day.

How much cumic meteres of Gas is required to generate 1 MW Elctricity. Is it around 1.5 million cubic meteres for 1 MW?
I am confused please help me.

Please send me any addtional info on Gas Power Plants if you have at:  

Please help me Sir, God will surely help you in a much greater way.

Sincerly yours
Anup


ANSWER: Anup, my friend, you need help from an engineer who can spend several hours with you, or maybe several days. It will be well worth your while, especially if you're actually trying to determine the economics of a power plant project into which you might invest real money. You need someone you trust who understands the physics and can do the energy math for you.
I'll give you a little bit more here, mostly to convince you, as a friend, that you need the help of a professional energy engineer:

First: Electric Power is not Electrical Energy. Power is the rate at which energy is generated or transformed. The unit of measure for Electrical Energy is watt-hours, or kilowatt-hours (one thousand watt-hours), or megawatt-hours (one million watt-hours), or gigawatt-hours (one billion watt-hours).

Second: A high efficiency, natural gas-fired combined-cycle power plant might consume about 7000 Btus of gas to produce one kilowatt-hour of electricity. That would be about 7 cubic feet of natural gas. It would therefoe take about 7000 cubic feet of gas to produce one megawatt-hour. In the U.S. today, one thousand cubic feet of gas sells at wholesale for about US$7.00 (seven dollars. So it would cost about $49 (wholesale price) just for the fuel to make 1 MW-hr of electricity this way.

Third: If the combined-cycle plant is a big one, with a power output of say 100 megawatts, it will generate electrical energy at the rate of 100 megawatt-hours per hour.

Hope this helps.
Good luck!
- Bill


---------- FOLLOW-UP ----------

QUESTION: Hope you are in good health and peace Sir Bill.
Thanks a lot Sir for your reply to my earlier question.

I have now got a clear idea that it takes $50 to generate 1 MW hour electricity from Natural Gas.

1. Could you please give me an Idea about what is the SALE Price by Energy Companies for a 1 MW hour electricity to Businesses/Power Grids/Households in USA.

I believe that a 1 MW capacity plant would generate about 8760 Megawatt Hours Electricity in 1 year. Is is true?

Please reply early.

Have a great week ahead.

Anup

Answer
Anup -
$50/MWh is only the fuel cost if the electricity is from a large highly efficient gas-fired combined cycle unit.
To that must be added the capital recovery costs, the staffing costs, maintenance costs, and some other costs that vary with how many hours per year the unit operates (water, chemicals, etc). After adding in all these the wholesale cost of production, including profit is perhaps $65-80/MWh.
Then one has to add in the costs of transmission and distribution and the profits associated with those. In the U.S. these could add another 50-100%. So the retail cost to the ultimate customer for electricity from gas alone might be in the range of $90-120/MWh.

But of course the actual retail cost of electricity in the U.S does not depend entirely on the cost of electricity from new natural gas plants. Only a fraction of the total electricity comes from new gas plants, the rest comes from existing older coal plants, nuclear plants, hydoelectric plants, etc, most of which produce electricity at a lower cost than gas. So the average retail price to a customer is based on a mix of costs, and varies depending on where one lives and what the generating mix is in that area.
But to answer your question, the average retail price of electricity for the whole U.S. in 2008 was just under $100/MWh.

Finally, yes, a 1 MW plant would generate 8760 MWhs per year ... IF it ran at full output for every hour of the year. But a new gas combined cycle plant will have to be shut down for some hours for planned maintenance and for unplanned mishaps (forced outages), so I would use at most about 87% of the hours in a year when estimating its actual energy output.
Good luck!
- Bill