Re: Mook's quote about nuclear being a "low grade heat". Is it true?

From: william mook (william.mook_at_mokindustries.com)
Date: 06/13/04 

Date: 13 Jun 2004 07:41:37 -0700

bri1600bv@hotmail.com (brianb) wrote in message news:<68a6629.0406121259.3e1fbe37@posting.google.com>...
> Back in the day, costs were not assigned to things that we would find
> necessary today. But EVEN WITH THOSE COSTS NOT ACCOUNTED FOR -
> NUCLEAR POWER WAS 2 TO 3 TIMES AS EXPENSIVE AS FOSSIL FUELS. That's
> what killed the nuclear age more than anything else. No one could
> figure out to make things cheap enough. Nuclear energy produced by a
> nuclear pile with 3% or enrichment, is a low grade heat! Especially
> when compared to heat engines that worked with combustion of fossil
> fuels. This reduces temperature differences and overall *capital*
> efficiencies. If you assumed improvements that increased capital
> efficiencies of nuclear power plants, you could apply them to fossil
> fuel heat engines, and they'd INCREASE THE DISPARITY - NOT DECREASE
> IT. This sensitivity analysis killed Johnson's dream. That's because
> a fundamental driver or ROI and cost of living in an industrial
> economy is the cost of energy. Subsidies that promote the use of
> inefficient energy sources like nuclear (and at present solar) -
> exacerbate the problem and don't solve it.
>
> ------------------
> Is the above quote true that nuclear energy is a "low grade heat"? I
> vaguely remember from thermo that efficiency is related to temperature
> differentials. Is that what he is talking about?

That's precisely one of the things I'm talking about certainly. While
it is possible to create very hot, and therefore very efficient
nuclear powered heat engines, its not possible to do so safely. So,
practical nuclear energy is constrained to low efficiencies. Check it
out;

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/carnot.html

   (Th - Tc) / Th = Carnot Efficency.

With all temps in absolute temperature - degrees from absolute zero -
if we deal with celsius the absolute temperature is measured in
degrees Kelvin, or K. The freezing point of water is 0C = 273K. Room
temp is 72F = 22C, so that's 298K, so a slightly warm room is 300K...

So, if Tc = room temp (which is about 300K) we can compute ideal
efficiencies - which can never be exceeded - knowing Th (hot
temperature);

   Th Tc Efficiency
   373 300 19.5% - Boiling water
   400 300 25.0%
   500 300 40.0%
   750 300 60.0%
 1,000 300 70.0%
 2,000 300 85.0%

This is one measure. Another is power density per unit area of
reactor, per unit mass of reactor, and so forth...

Any introductory course in nuclear power plant design will go into all
of these factors. Its a bit much though to recount all of it
completely in an online posting.

>
> How exactly does his PV solar concentrator work anyway. It sounds
> interesting.

The cost of solar energy relates to the power available in sunlight,
the cost of converting that power to useful form and the efficiency
with which the conversion is done.

The amount of power arriving per square meter at the surface of the
earth on a clear day is around 1,000 watts. That's about 1 and a
quarter horsepower per square yard.

The cost of silicon runs around $1,550 per square meter $1,300 per
square yard.

The efficiency of silicon solar cells is no more than 20% so, the
useful power out when the sun shines is 200 watts electrical per
square meter. This means that the cost of solar collectors will be
around $7.75 per watt. Fill factor losses and other costs make this
more like $8 per watt!

Since silicon is a mature technology that stands behind the consumer
electronics revolution, don't look for vast improvements there.
Gradual improvement is occurring and will continue. But rapid
breakthroughs are not forthcoming. Although over time, prices are
expected to drop gradually to below $1 per watt, just by improving the
cost efficiency of silicon production.

Special tricks, like buying surplus silicon at a discount can reduce
these costs to $4 per watt, but their impact is limited for any
large-scale producer of solar panels. That's because only limited
amounts of materials can be acquired in this way.
  
What is needed is a way to get silicon or to operate at vastly higher
power densities. Then costs can drop. This is easily achieved
through concentrating sunlight with a parabolic mirror.

Clearly if we focus light to a point with a dish (or a line using a
trough) we can increase power density 10x, 100x, 1,000x, (although
line concentrators are limited by optics to 208x solar intensity, and
dish concentrators are similarly limited to about 40,000x solar
intensity) and even more to obtain costs (for silicon) that is 1/10th,
1/100th, 1/1,000th, and less. So, by concentrating sunlight we can
reduce costs to $0.78 per watt, or $0.08 per watt,or 8/10th cent per
watt, or less.

Now, anyone who has taken a solid state physics course in college may
recall that in experiment three in the course they illuminated a
photocell with a variable light source and plotted the current
produced. Anyone who did well in the course will be quick to say that
at around 2x solar intensity the power peaked at about 1.5x full solar
current, AND THEN DROPPED! They will recall that this illustrated
that solar cells suffer from parasitic losses when illuminated at high
intensity. You actually get less power out at high intensities of
illumination than you do at one solar because of these parasitic
losses. So, they conclude, along with everyone else, that you can't
do what I've just proposed to dramatically reduce solar power costs.
In fact,if you add the cost of the concentrator and tracker to make
this system work, costs could actually increase. And they're right!
With conventional photocells you can't concentrate the light to reduce
costs.

Well, lets look at parasitic losses then. What are they exactly? And
can you get around them?

To answer these questions we need a little undertanding of what
happens in a solar cell.

A solar cell is a version of a photo diode. A diode is a device that
lets current run in one direction and not the other. A solar cell is
set up to produce a forward current when its illuminated and the diode
maintains the electrical potential of this forward current so that it
is available to an external load, powering it.

But, there is also a dark current. If you illuminate a solar cell and
put it in the dark, without a load, the electrical potential will
gradually fade away. That's becaus a 'dark current' exists. This
dark current is the leakage of current opposite the forward current
and it is proportional to the temperature of the junction. Increase
the temperature and the dark current increases by the same proportion,
robbing current from the forward current, reducing efficiency. This
relationship is so accurate folks use silicon diodes to make
thermostats and electronic thermometers by injecting a known current
and measuring how much is lost across the diode.

So what's this have to do with parasitic losses? Well, heat increases
the dark current. This robs the forward current of power. Now,
here's the kicker. The forward current all by itself heats the
junction! That's because the junction has a resistance. This means
the junction disappates power heating it when current flows. This is
proportional to current squared times resistance.

So, now we know enough to calculate the result of experiment two in
your solid state physics course! The voltage of a solar cell is given
by its structure and composition. The current is proportional to
light intensity. The temperature of the junction is proportional to
the current squared times resistance - and the dark current is
proportional to the temperature times a factor. So the complete
equation looks like this;

       Pout = FORWARD CURRENT - DARK CURRENT

       Pout = Factor1 * Intensity - Factor2 * Resistance * Itensity ^2

The factors are just constants related to the materials involved and
their method of assembly. The important thing to see is that as light
intensity grows the forward current increases as expected, but the
dark current grows faster, and eventually overtakes the forward
current no matter what.

In typical solar cells this occurs around 2x solar intensity. Which
makes it dandy for a simple experiment.

But, by changing the internal resistance of the solar cell (as in
Swanson's SUNPOWER cells) you can change the speed with which the dark
current grows with intensity and change the location of the peak. Or,
by changing the VOLTAGE of the cell by making a certain type of
multi-junction stack(as in Sater's PHOTOVOLT cells and others) you can
change the rate of growth and the location of the peak as well.
Combining both ideas,along with others related to the factors,you can
do extremely well!

How far can you go in this direction? We've tested cells in our
equipment that are capable of producing output some 3,000x that
observed at 1 solar intensity! We are currently working on cells that
operate at 5,000x solar intensity and higher! We have as a goal to
achieve solar cells that operate at 15,000x solar intensity.

This dramatically reduces the cost of silicon in a solar cell - so
that the costs of the mirrors, trackers, heat sinks, and other stuff -
dominate.

As each factor comes to the top of the cost list, we have addressed
it, very successfully. Today we have 48 patents underway related to
all aspects of making the original concept of high-intensity photocell
operation work cost efficiently. We even found that large forward
currents and low dark currents can be manipulated at high intensities
so that efficiencies are actually increased from handbook values.

At present we have developed solar collectors that can be mass
produced for far less than current solar cells per peak watt and have
an areal efficiency of 40%. This means a square meter produces 400
watts electrical and we can produce energy for less than the cost of
fuels alone in conventional power plants. When you add in the cost of
batteries, inverters and everything needed to make a workable power
plant - we can produce baseload power for less cost than coal fired
plants. When the DC output of the panels are used to drive water
electrolysis hydrogen is produced at less cost per unit energy than
gasoline! This means that for the first time in history, we have the
ability to make massive use of solar energy on an industrial scale -
and actually save money doing so!

Since the panels cost less than the enegy they produce over their
lifecycle, we do not sell equipment. We sell energy!

This is a paradigm shift in the solar energy business. We're the
first solar energy company that actually sells energy! And we do so
cost-competitively without government subsidy or non-market support.

We are in the process of negotiating a number of contracts with
companies that use large quantities of DC electricity - becuase our
system offers the lowest cost method of producing energy. We are also
in the process of negotiating a number of land use agreements with a
companies that own land - this gives us access to over 100,000 square
miles throughout the world.

100,000 square miles of land (about 1/3rd the size of Cecil Rhodes'
holdings obtained from Queen Victoria) is enough land area to produce
four times today's industrial energy needs entirely from sunlight.
With 4% annual growth in energy use around the world - a growth rate
consistent with peaceful economic development throughout the world -
we will make use of all this land within the next 35 years.

This is an important factor in evaluating the resources of a solar
ENERGY company. While oil, gas and coal companies have reserves
evaluated in barrels, tons or cubic feet - solar energy companies like
ours are to be evaluated by their land holdings - since that is the
interface with the inexhaustable solar resource we're making use of.
By this measure Mok is the largest energy company in the world, with
an inexhaustible supply which we can tap cost competitively and with a
capacity to meet a continuously growing world economy demand for the
next 35 years. Against this measure all other energy companies pale
by comparison!

What to do with this resource? Make synthetic fuel obviously.

Hydrogen is a very interesting fuel to make. Not only can it be used
in a variety of ways directly, it can be used indirectly to produce
lots of interesting products.

Most interesting is the Sabatier reaction to produce methane -
synthetic natural gas from carbon dioxide and hydrogen. Here, we can
take CO2 from the air, or from a coking plant, or from a coal fired
plant, combine the CO2 with hydrogen and make synthetic natural gas
from it.

We can sell the natural gas, or we can run the natural gas through
zeolite to produce synthetic liquid fuels and sell those. Australia
takes large quantities of extracted natural gas and makes liquid fuels
this way.

Since our methane and liquid fuels are derived from air and sunlight,
we actually are converting all fossil fuel users who burn our fuels to
solar energy users - giving everyone virtual solar plants - without
the need to massively change infrastructure. In the process we
produce clean synthetic fuels that have zero sulfers metals and other
dirty secondary pollutants.

By making use of atmospheric carbon dioxide as an industrial carbon
feedst*** in a solar powered fuel generation system we have closed the
open ended industrial carbon cycle that has fouled our air and have
the means to cost efficiently run carbon dioxide levels up or down -
independent of rate of use of carbon based fuels. Ultimately, all the
oil that ever was or ever will be extracted and burnt may be
re-created with this solar powered system - all free of charge -
except of course the capital cost and land cost associated with the
operation.
 
With low-cost synthetic fuels chemically identical to extracted
fuels,produced at lower cost than extracted fuels,we have the means to
enter the market and augment our failing fuel supplies. For the US
this means we have a way to create energy independence using domestic
resources for the first time since US fuels faltered and gave rise to
OPEC.

General global economic growth means continued exponential growth in
energy use. Since extracted fuels are limited and solar fuels are
unlimited we can expect solar fuels to dominate supplies within 15
years or so, even while extracted fuels are produced in as large a
quantity as they can be produced from known resources.

All the carbon released is available to the solar synfuel producer as
a feedstock - free of charge! With solar energy as the resource for
the solar fuel cycle, and atmospheric carbon - all the oil formerly
and now in the wells of the major oil companies, will one day be in
the holding tanks of the solar synfuel maker, and be available to
refill the spent wells as carbon dioxide levels are steadily brought
down to natural levels.

Meanwhile, continued research will bring online more efficient ways to
bring solar energy to market. Hydrogen fuel, beamed energy, super
capacitors, super batteries, will all be developed over time to make
solar more efficient, and eventually end the age of oil and its major
effects on the environment.

This is all possible because we have solved the problem of making very
very low cost solar collectors. These collectors can be used in a
variety of ways - the most important for today's economy is the
generation of synthetic fossil fuels from carbon dioxide in the air
and sunlight.