Posts Tagged ‘energy’


Comparison of Arizona Nuclear and Solar Energy

December 9, 2015

Let’s compare and contrast solar energy and nuclear energy in Arizona. There is only one nuclear power plant in the state, the Palo Verde Nuclear Generating Station in Tonopah. There are several solar energy sites, so we will pick the Aqua Caliente Solar Project because it won the Renewable Energy World Solar Project of the Year category in their 2012 Excellence in Renewable Energy Awards.

Palo Verde Nuclear Generating Station

This nuclear plant consists of three reactors with with a total nameplate capacity of 3,937 MW. If these reactors ran for 24 hours day for 365 days a year they would yield 34,500 GWh (gigawatt hours) per year. The actual output is about 31,300 GWh per year (2010). This means they have a capacity factor of about 90%. Averaged over time Palo Verde yields 3,543 MW.

Palo Verde became operational in 1988 and is currently approved to operate until 2047, giving a lifetime of nearly 60 years.

Palo Verde’s construction cost was $5.9 billion in 1988 ($11.86 billion in 2015 dollars). Its operating costs for fuel and maintenance were about 1.33 cents per kWh in 2004 (1.67 cents in 2015 dollars.)

Based on an average power yield of 3,543 W and a cost of $11.86 billion (in 2015 dollars), the construction cost per watt for Palo Verde was $3.34 per Watt (in 2015 dollars).

Agua Caliente Solar Project

This 9.7 square kilometer solar energy farm has a nameplate capacity of 290 MW peak.  Its first year of full operation was 2014. If it were able to produce its nameplate capacity of 290 MW continuously for one year the energy output would be 2540 GWh. The energy output was 741 GWh in 2014, which means a capacity factor of 29%, an excellent result for solar energy. Averaged over time, this solar farm yields 84.6 MW.

Construction cost for Aqua Caliente was $1.8 billion.

Based on an average yield of 84 MW and a construction cost of $1.8 billion, the construction cost per watt for Aqua Caliente was $21.43 per Watt.


The cost per kilowatt hour of energy for either of these sources is combination of the construction cost and the operation, fuel and maintenance cost.  The longer the facilities are in operation the lower the fraction of construction cost per kilowatt hour.

The operation, fuel and maintenance cost for the Palo Verde Nuclear plant were about 1.33 cents per kWh in 2004 (1.67 cents in 2015 dollars.)  The great advantage of the Agua Caliente solar farm is that its fuel cost is zero, and we will assume for the sake of argument that its other operation and maintenance costs are also zero.

The following chart shows various costs per kilowatt hour for each of the facilities for various lifetimes.


1.  $0.0133 per kilowatt hour in 2004.  Converted to 2015 dollars.
2. 2013 energy output.
3. $5.9 million construction cost in 1988 dollars.  Converted to 2015 dollars.
4. 2014 energy output
5. $1.8 billion construction cost in 2014.
6. (GWh/year) x (number of years) x (1,000,000)
7. (Construction cost) / (kilowatt hours produced over lifetime)
8. (Construction cost per kWh) + (operating cost per kWh)

Two blocks of data are highlighted in yellow.  These are the most likely lifetime scenarios for each of the power generating plants.  The Palo Verde nuclear plant has had its license extended to 60 years.  Aqua Caliente solar farm is made from First Solar CdTe modules that have a 10 year material and workmanship warranty and a  warranty of 80% of the nominal output power rating during twenty-five (25) years.  It is reasonable to hope that it will last 40 years

There is one more thing to be considered.  We have assumed so far that the yearly output of each of these power generating stations it the same year after year.  That is not entirely correct.  Historically, the Palo Verde nuclear plant has increased its capacity factor through time as operations have become more efficient.  Whether that trend will continue is unknown.

Solar modules tend to slowly degrade with time.  The First Solar CdTe modules that are used at Aqua Caliente will likely decay at about 0.5% per year. The chart above gives a best case estimate for Agua Caliente and does not compensate for this degradation.

Based on the highlighted sections of the above chart, Aqua Caliente Solar Farm will likely cost about 2.5 times more per kilowatt hour than the Palo Verde Nuclear Plant over the course of their lifetimes.

One more point.  Aqua Caliente requires 9.7 square kilometers to generate an average of 84.6 MW.  Palo Verde Nuclear Plant generates and average of 3,543 MW.  So it would take 41 Agua Calientes to equal the power of Palo Verde.  That would require about 400 square kilometers.

Energy is the lifeblood of civilization.  The pursuit of energy abundance is the pursuit of healthier and more fulfilling lifestyle for greater numbers of people.  I present this data to help inform the choices that need to be made in that pursuit.


Units of energy: homes?

March 8, 2014

corrected 4/12/14

How many BTUs are in a kilowatt-hour?  How many barrels of oil equivalent (BOE) are in a kiloton of TNT?  There are a lot of different units of energy and power.  Which one is chosen at a particular time depends on the field and the customs of its experts.  It can get a little confusing when comparing numbers from practitioners in different fields.

It can be very eye opening to make the conversions.  For example, six sixteen watt CFL bulbs lit up for six hours will use as much energy as released by the detonation of one pound of TNT.  My preference is to convert powers to watts and  energies to watt-hours.

New unit for power

But there seems to be a new unit of power that I can’t find in any of my physics books.  Its called a “home.”  Here are some examples of its usage…

“The Tatanka Wind Farm, on the North Dakota-South Dakota border, will power 60,000 homes.”

“Limon I Wind Energy Center in Colorado is capable of generating enough electricity to power approximately 100,000 homes.”

“[E]nough clean electricity to power over 60,000 homes.”

“A 230 MW photovoltaic solar station in the Antelope Valley of California that will supply enough energy for 70,000 homes.”

“The new Copper Mountain 3 solar plant, which will be finished in 2015, will be able to generate enough power to supply around 80,000 homes.”

“Chicken Manure to power 90,000 Homes in the Netherlands!”


Ivanpah mirrors

Mirrors at Ivanpah

Brightsource’s Ivanpah Solar Electric Generating System in California is a case in point.  This is a solar thermal site that uses thousands of mirrors to concentrate sunlight to generate heat to run generators. says  the “$2.2 billion Ivanpah Solar Electric Generating System—the largest of its type in the world—will power 140,000 California homes.”  It looks like they are using a “home” as a unit of power.

What does “will power 140,000 California homes” really mean?

According to the EIA, the average home in California consumes about 7000 kilowatt-hours of electric energy each year  (most recent data, 2009).  That means 140,000 homes would use 9.8 x 108 kilowatt-hours (9.8 x 105 megawatt-hours) of electric energy per year.  I think we’re on the right track here, because the National Renewable Energy Laboratory says Ivanpah will produce 10.8 x 105 megawatt-hours per year.

But this unit of power called a “home”  is still a little misleading.  Although the average California home consumes about 7000 kilowatt-hours of electric energy per year, energy from other sources is also consumed.  The other big source is natural gas, which may be used for space heating, cooking or water heating.  If you think this is trivial compared to the amount of electricity used, think again.  The EIA document on residential energy consumption in California shows these graphs…

EIA California energy consumption

I think it is bad practice to use two mix different units for energy (kilowatt-hours and Btu) as the EIA has done with these graphs.  How many people can compare kilowatt-hours and Btu by looking a graphs?

The graph on the top left is where I got the estimate of 7000 kilowatt-hours of electrical energy per year for the average California home.  Notice that it is labled “ELECTRICITY ONLY.”  The graph on the lower left is for “ALL ENERGY average per household,” and indicates about 62 million Btu per California home per year.

How does 62 million Btu compare to 7000 kilowatt-hours?   62 million Btu translates to 18,170 kilowatt-hours!  In other words, 11,170 kilowatt-hours of energy consumed in the average California home comes from sources other than electricity.  If you find this hard to believe, look at the number of kilowatt-hours you used on a recent winter electric bill and look at the amount of energy, usually in “therms,” on a recent winter gas bill.  Convert the “therms” to kilowatt-hours and you will see what I mean.  It takes a lot more energy to heat water and air in your house than it does to light your bulbs or power your TV.  So Ivanpah really only provides enough energy to power 54,000 (≈140,000 x (7000/18,170)) California “homes.”

You might think that providing enough energy for 54,000 homes is still pretty impressive and makes a big dent in California’s energy needs.  Think again.  There are 12.5 million households in California.   So it would take about 240 (≈12,500,000/54,000) Ivanpahs to power them all.  Ivanpah covers about 16 square kilometers.  So it would take about 3600 (= 16 x 240) square kilometers to power all these households.

Building 3600 square kilometers of mirror arrays is a big undertaking, but wouldn’t it be worth it to power the entire state of California?  The problem is that it wouldn’t power the entire state of California.  Residential power consumption is only about 20% (1/5th) of California’s total energy consumption.  Far more energy goes into commercial, industrial  and transportation needs.

If we assume vast efficiencies then we might say that it only takes 2.5 times (instead of 5 times) the residential energy consumption to run the entire state of California.  With these assumed efficiencies Ivanpah would provide the total (not just residential) energy needs for the occupants of only about 22000 (≈ 54000/2.5) homes. It would take nearly 600 (≈2.5 x 240) Ivanpahs, a whopping 9000 (≈ 3600 x 2.5) square kilometers of mirror arrays, and $1.3 trillion (≈ 2.5 x 240 x $2.2 billion) to provide the average energy needs of the entire state.

Why talk in terms of “homes?”

The use of “home” as a unit of power has a warm and fuzzy feeling to it.  I guess good and caring people are concerned about “homes,” while cold and uncaring people talk about “kilowatt-hours.”  Using “homes” as a unit of power gives the impression (intentionally?) that all the energy needs of the people living in those homes are met.  It is much more impressive to say an energy project will “power 140,000 homes” than to say it will compensate for the total energy needs for the people living in 22,000 homes.

I believe this loose use of the English language and lazy, imprecise use of physical values  is used precisely because it yields more impressive numbers.


Which car would you rather drive?

September 19, 2010

Which of these two cars would you rather drive… 

Smart Car

Edison 2

The top car is the mis-named “Smart Car” from Daimler AG.  For somewhere between $12,000 and $20,000 you get a vehicle that carries two people gets 33 mpg city and 41 mpg highway for a combined 36 mpg.  That’s almost 85% of the fuel economy of a Honda Civic – fifteen years ago.    

The bottom picture is of the  Automotive XPrize winner,  the Edison2.  The Edison2 seats four, gets over 100 mpg, has a top speed of of 110 mph and a range of over 600 miles on a single tank of gas.  It will travel 50 mph on a mere 3.5 horsepower. and will go from 0 to 60 in less than 10 seconds.  And it would cost half as much as a Chevy Volt.   Edison2 is headed up by Oliver Kuttner, and according to consumer reports Kuttner says the Edison2

has plans for a car that is closer to being production ready, with bodywork that sounds more substantial. Should it progress to production, the car could be offered in the $20,000 range.

The call is yours, which would you rather drive?