What does "30 megawatt (PV) facility" mean?

[phantom power]

I've seen this kind of measure referred to in a couple other places, but here's today's example:

"The construction of our EverQ facility also remains on schedule. Current plans call for the initial 30-megawatt facility to be completed by the end of 2005 and installation of furnaces and equipment to commence in the first quarter of 2006. We look forward to being fully operational in Thalheim by about this time next year."

http://www.corporate-ir.net/ireye/ir_site.zhtml?ticker=ESLR&script=410&layout=-6&item_id=738198

Does this mean the factory will build enough PV cells per year to generate 30 megawatts? If not per year, per month? Or is it some completely different thing?

[Massacure]

1. It's peak capacity of all the PV cells made during the course of a year.

If you were to hook all the PV cells that the factory manufactured between the course of January 1, 2005 and December 31, 2005 together and connected it to the electricity grid, it would provide 30 megawatts of power at high noon on a cloudless day.

[Viking12]

2. It is a measure of peak output power

1 w = 1 joule per second
30 MW= 30,000,000 joules/sec
A megawatt day (MWd or MW·d) is equal to 86.4 GJ.

[skids]

3. Power versus energy.

Just to clear up for those who forget all their physics:

Power is measured in Watts.
Energy is measured in Watt-hours.

If a generator produces one watt of power for one hour, it has produced one watt-hour of energy. This is what you pay for -- your electricity is normally priced per-killowatt-hour.

The same applies to a lightbulb.

A fifty watt lightbulb, run for one hour, will use 50 Watt-hours of electricity. Same thing in reverse.

[NNadir]

4. They are being completely unclear. "Megawatt" in solar speak usually...

...means the capacity that a solar installation can produce at high noon on a cloudless day. This is a marketing ploy that is designed to make PV seem cheaper than it really is.

I would suspect that these people are discussing a plant that will have the capacity to manufacture 30 Mega"watts" of solar cells in a year, but they are being obscure about what they mean.

One almost always has to dig, and sometimes calculate (as I often do) what solar power claims actually mean in terms of energy. The way to discover this is to locate an energy term for an existing solar power plant usually expressed in kilowatt-hours or (more rarely) megawatt-hours. One can then convert these energy units to megajoules or kilojoules by multiplying by 3600 seconds per hour. (Note that a watt is a joule per second, so all the units cancel out leaving only joules.)

When one does this exercise, one almost always finds that the capacity loading of a typical PV solar plant runs on an annualized 24/7 basis at between 10 and 20%, most often in the middle of that range.

As an advocate of nuclear energy, I am often confronted with stupid statements comparing the output (and costs) of a nuclear plant with a solar plant in terms of watts, kilowatts, or megawatts. I used to let it slide, but I will not be doing this in the future.

Let us say that PV solar power gets down (some day as has been promised for the last 30 or 40 years) to $2.00/"watt" (current prices are 2.5 times as large) where the quotation marks refer to watts of power peak of a theoretical clear day at noon. Then a 1,000 Mega"watt" plant (billion watt, since a billion is a 1000 million), equivalent to a normal will cost $2 billion dollars. However the plant operates at only 15% average capacity loading. Therefore the real cost of the plant is 2 billion dollars/0.15 = 13 billion dollars.

I personally think that people who are wealthy enough to afford PV systems, people who want middle class and upper middle class comforts like air conditioning, may have a moral obligation to use PV systems for peak loads if they are in appropriate circumstances to do so. However I am under no illusion that PV power represents a general solution for humanity as a whole.