Another factor that puts a sever crimp in the use of wind and solar power as mainline electrical supply sources is amperage, or rather the lack of it.

Solar cells, assuming 40-50% conversion efficiency (which is what it was the last time I checked, two years ago) generate low-amperage current. Wind-turbine amperage varies with output voltage, which varies with (surprise!) wind velocity.

What both have in common is that amperage never gets high enough to overcome resistance (line-loss) over the long lines the “Wind And Sun Only (WASO)” mavens dream of.

Ohm’s Law will not be denied. And Congress can’t repeal it, either. The only way to make it work would be to have transmission lines composed of Room Temperature Super-Conductor (RTSC) material. The only problem with this is, so far, no one has managed to come up with a material which is a superconductor above cryogenic temperatures.

The reason I checked back in ‘06 was that on a PBS show, one “expert” from The Sierra Club said that it would work. All we needed to do (says he) is use superconductors for transmission lines. When someone else pointed out that there were no superconductors available that worked at normal temperatures, his response was, “no problem- we’ll just run them in pipes full of liquid nitrogen.”

Under every street in the country.

I have worked with LN under laboratory conditions. I know that, while an inert gas per se, it is difficult and dangerous to handle under the best of circumstances.

And this…person… wants to use it in a way that is about as far from “the best of circumstances” as Long Island is from Lompoc, CA.

I think this tells you all you need to know about the scientific and technical “expertise” of the “Wind And Sun Only” crowd.

We need to stop letting scientific ignoramuses set our policies regarding energy. Or, indeed, our policies regarding anything to do with engineering, period.

I include lawyers in the “ignoramus category”. Recently, in our local court, a traffic case came up in which a woman ran a red light in front of an oncoming semi, and got corner-rammed and spun into a light pole for her trouble. Her “defense” was that (quote) “the truck driver should have understood that I was going through, and backed up”- while the truck was moving at 35 MPH.

The judge told her, “That would have required the truck driver to violate the laws of physics.”

Her lawyer’s response?

“Well, he should have violated them instead of hitting my client!”

I rest my case.

cheers

eon

eon on July 8, 2008 at 6:43 PM

njcommuter on July 9, 2008 at 11:31 AM

Taking it in order;

1. You’re confusing voltage and amperage. Voltage is the amount of power being transmitted, amperage is the ability to overcome resistance, R, expressed in ohms. (Ohm’s Law.) To visualize the difference, do this gedanken experiment;

Put a gallon of water in a bucket, then throw the water (but not the bucket, please!) at somebody so that it takes 1 second for the full gallon to hit them. They’ll be drenched, and probably not too happy about it unless it’s a hot day.

Now, put the same gallon of water in a high-pressure centrifugal pump (like the ones on a fire pumper) and force it through a carburetor jet off of a 1965 Chevrolet V-8 in one second. If that narrow jet of water hits someone, it can draw blood, as the pressure behind it is high enough that it will scour off skin. (Add in sand, and you have an industrial sandblaster, actually.)

The amount of water (1 gallon) is the voltage. How hard it hits (by thrown bucketful or by HP pump) is the amperage. Never confuse the two.

2. The “heat loss” you mention over long lines is the result of the resistance (R, in ohms) of the conductors in the lines (usually copper) to the amperage (not voltage) of the current. Resistance is a factor of exactly what the conductors are made of; copper has about the least of the reasonably inexpensive metals. For really low R, the Apollo spacecraft’s DC electrical system used wiring made of gold and in some areas platinum; but that’s a bit expensive for long lines and can’t take as much tension on a “sag” as copper. (To say nothing of how fast it would be stolen by metal thieves.) The resistance of even copper renders long line transmission of solar or wind-turbine generated AC or DC power dicey at best.

3. My figure for 40-50% efficiency is that quoted by NASA for the solar arrays on their spacecraft. I don’t expect that they would work as well under 20+ miles of atmosphere, even on a sunny day, as they do in hard vacuum, but I like to give the other guy the benefit of the doubt. (If his hypothesis won’t work even under ideal conditions, it certainly won’t work in real-life conditions. Caveat Emptor.)

4. Other posters have dealt with the difference between AC short-range transmission and DC long-range, which is rarely used in the U.S. (I won’t say never, as I am not an electrical engineer). DC transmission is used in other countries because they use DC current domestically, not having realized (unlike George Westinghouse over here) that Nikola Tesla had his facts a bit straighter than Thomas Edison did.

5. I was aware of the cryogenic systems feeding WTC; you find similar systems in similar applications in everything from power plants to large buildings worldwide. I was referring to the impracticality (let’s call it what it is- plain dangerousness) of trying to run long lines underground for large areas of domestic grid, through all sorts of soils with the attendant problems of ground water, shear lines, strata differentials, and traffic-induced vibration (to say nothing of the occasional burst water main), with all the lines run in insulated pipes full of a liquid which can instantaneously freeze anything it hits. The guy on the show was conspicuously silent on the subject of how you insulate such a conduit, how you deal with inevitable vaporization pressure issues (especially on a hot day- or just in Southern California on any given day), or what you make the conduits out of that will resist embrittlement by being subjected to temperatures near absolute zero for years at a time. Not to mention what happens if somebody on a city work crew accidentally hits one with a backhoe while working on a sewer line. Best guess; work crew ends up in the nearest ER- if they’re very lucky. With frostbite the likes of which is rarely seen outside of the Arctic regions, or when something goes very badly wrong at Burdette Oxygen or Morton-Thiokol. Which, fortunately, is rare due to those organizations having safety regulations and procedures virtually identical to those those used at Cape Canaveral- for exactly the same reasons, NASA being one of their biggest customers.

However you slice it, Wind and Sun just won’t cut it except in very small-area, localized applications. You can change the laws of the land, but not the laws of physics.

(Don’t look at me- I didn’t write ‘em.)

cheers

eon

eon on July 9, 2008 at 6:13 PM