In , David Nebenzahl
wrote:
On 7/31/2010 1:45 PM Han spake thus:

"HeyBub" wrote in
m:

There aren't any places left to build dams - in fact some are being
torn down so the Wart-faced Faux Salmon can defecate. Further,
hydroelectric dams are the most dangerous of all methods of power
generation (dams don't fail often, but when they do...).

I am thinking smaller dams, not everything needs to be Hoover sized

Nor--even better example--Three Gorges-sized.

The term for such smaller dams is "low head hydro". Smaller dams reduce
the negative impact of damming watercourses: loss of wildlife habitat,
farmland, canyons, etc.

That leave nuclear, but far too many people are too phobic about the
prospect for nuclear energy to be politically viable.

Let's collaborat on promoting nuclear. I happen to believe that nuclear
is an excellent way out. Look at France ...

Let's not. Nukes are still a Very Bad Idea.

First of all, they're really not necessary. Even if we eliminate coal as
a source for electrical power generation--by far the worst environmental
offender, by consensus--we can still generate the power we need with a
mix of other technologies (including cogeneration, which captures energy
otherwise wasted), plus conservation. This includes solar, wind, hydro,
biomass, etc.

Nuclear power is still far too dangerous for this planet at this time.
Unlike other technologies, it has significant risks at each step along
the nuclear fuel cycle: mining, milling, fuel-rod fabrication,
transportation, power generation, decommissioning and spent-fuel storage
and disposal. There have been significant accidents at each step of the way.

And worst of all, there is still no viable scheme for long-term waste
disposal.

That situation in USA is at the request of those who want lack of
existence of such.

The barriers are political and not technical.

It is easy to dump nuclear waste into such suitable places as depleted
petroleum "reserves" under salt domes, that successfully contained liquids
over 1 Km underground for roughly 200 million years.

It is easy to dump radioactive waste into depleted uranium mines where
radioactive uranium ore sat for at least 10's of millions, probably
100-plus million years as innocently as the Garden of Eden.

I happen to know something about the subject as I researched
it in college and wrote a paper about it. Even now, 20 years after the
feds ran the nuclear waste railroad into Nevada (Yucca Mountain), things
are no better and we're no closer to a safe storage facility.

Primarily at request by political forces desiring a political declaration
that "safe storage" is impossible.

The stuff is just too ****ing dangerous for us stupid humans to deal with
it, apparently, despite slews of pointy-headed scientists that have
grappled with the problem.

Perhaps in the future, but not now.

Besides, why not use the greatest *fusion* reactor in the solar system?
It's a nice safe 93 million miles away from us, and provides all the
energy we'll ever need.

Can you cite how that can meet ourcurrent needs without requirement of
many humans to big-time "let go of" modern comforts and modern
necessities for productivity needed to sustain "modern comforts"?

We just need to learn how to capture and use it.
(And I'm not just talking electricity he somehow, we've seemed to
have forgotten all about simpler, more direct uses of the sun's
energy--remember "passive solar"? Still works, still is extremely
underutilized.)

Please keep in mind how much of that is "low grade heat".

Heat energy collected at a temperature mere degrees or 10's of degrees
warmer than "prevailing ambient" is good for not much other than home
or workplace heating (often only intermittently) and sometimes hot-water
heating.

As for conversion to electrical energy - please consider lack of any
business operation making any gigabuck-class improvement over the
11%-or-so collection efficiency of monocrystalline silicon solar cells.
While over 10 years ago it was diasclosed that GaAs did better, and a
"sandwich" of a "GaAs derivative" ("my words") over monocrystalline
silicon achieved around 30%. IIRC, that was disclosed published
somewhere around 15 years ago. No bigtime commercial product yet for
~30% as opposed to ~11% collecting-efficiency photovoltaic cells or
combos thereof?

As for converting "low grade heat" to mechanical energy:

A "heat engine" has ideally in most-oversimplified-ideal as-far-as
I-know, 3 ports. "Port 1" is input of heat energy. "Port 2" is exhaust
of heat energy, at a temperature lower than that of Port 1. "Port 3" is
output of energy in a form other than heat, preferably mechanical or
electrical.

As far as I understand "The Laws of Thermodynamics", the output of heat
energy from Port 2 is the input of heat energy into Port 1, minus the
energy delivered out through Port 3.

Meanwhile, the heat output from Port 2 is at minimum the heat input to
Port 1, times ratio of absolute temperature of Port 2 divided by that of
Port 1.

At most, non-heat energy delivered from Port 3 is the difference between
the throughputs of Ports 1 and 2. If the temperature difference between
Ports 1 and 2 is small compared to "ambient temperature", then
even-theoretically-best efficiency of converting heat energy entering
"Port 1" to mechanical or electrical energy (output via "Port 3") is low.

--
- Don Klipstein )