Power generation system. Part 2

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After some investigation, I've decided to CONSIDER a completely different
approach to a petrol, or diesel generator. I can buy a 3kVA inverter for
about $3k and some Solar cells (10 X 115Watt panels) for another $8k. The
gummint gives me back $4k (yay!). I have plenty of easily accessible (<2
Metres from ground level), flat, unshaded roof space for the panels. I can
buy a second hand, refurbished, 24V 1kA/Hr battery for another $2k.Not only
should I be able to generate all the power I require, but, for a few extra
Bucks, I can feed the surplus back into the mains and make a little profit
(double YAY!). No neighbour problems and get to have a warm, fuzzy, green
feeling. A win all 'round.

Any thoughts and suggestions will be appreciated.


--
Trevor Wilson
www.rageaudio.com.au



Re: Power generation system. Part 2



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Only if your inverter is the appropriate type. Not sure if the price you
mention for 3kVA is for a stand-alone or mains-connectable.
The batteries sound cheap. Mine are 700AH, 24V and cost $4000 new. The
rebate also has conditions - e.g. the system must use NEW components (I
think) and be installed by an accredited installer etc.
Alan


Re: Power generation system. Part 2



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**$4.5k for the mains-connectable type.

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**Batteries are second hand.

 The
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**I figure on leaving the batteries out of the system, then installing them
later, just unsing mains interactive inverter. The acredited installer part
should not be a problem (I hope).


--
Trevor Wilson
www.rageaudio.com.au





Re: Power generation system. Part 2



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There is no replacement for a generator. Every decent set-up still needs
one...

 >I can buy a 3kVA inverter for  about $3k and
Pure sine wave inverter/charger approved  for grid interactive connection
for $3K? Sounds too good....

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Fair price...but for the system to operate without recharge from mains or
diesel generator, you would need a lots of modules. Do not forget, 115 watts
is peak power. You can count on 1/2 average per day. 5 modules  (24V) would
average 600W. You would need much much more than that.

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It is if you meet conditions. There are plenty....

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The most important part of the system is, guess what, the battery bank!
While everything else can be second hand and still work, there is no such a
thing as "refurbished second hand" stationary battery that still have enough
capacity for the system.
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few extra
The proper term would be double Whammy. Kilowatt produced by the system
would cost at least 3 times more than from the mains. If approved, power
authority will pay you fraction for what they charge.......

No neighbour problems and get to have a warm, fuzzy, green
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The hybrid power generation is hijacked by the global oil corporations.
Basically, there are no real investments or R&D.
They are waiting for oil to run out or when pollution is prohibitive to use
oil.
Therefore, cost of the components is just too high. We can only dream to see
solar panels on every roof in Australia.
There are thousands of panels along German highways, but not many here....

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Do the maths better....

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Re: Power generation system. Part 2



"hadda hadda" <draw.hotmail.com> wrote in message
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**Bugger.

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**Yeah, sorry 'bout that. $4.5k for mains interactive.

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**I plan on using 10 modules. Maybe adding a wind generator (200W), if I can
slide it past the council and neighbour objections.


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**So I've found.

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**My battery guy has a fair bit of experience in this area.


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**Typical.

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**I'm pretty certain I already have.


--
Trevor Wilson
www.rageaudio.com.au



Re: Power generation system. Part 2


Silicon manufacture for solar cells requires more
energy than the cells can make in thirty years, that
doesn't count the energy to process the silicon into
solar cells or the losses to store the energy made
by them.

If you look closely at the manufacturer's specs
you'll see the power drops off to about 80% after
ten years, due to micro fractures in the silicon
material causing performance degradation and a life
of about 20 years.

You'll most likely be doing the environment a favour
by buying an alternator instead and just using it
when neccessary. With proper maintenance and storage
it probably will last longer than the cells anyway
and definitely longer than the batteries you'll need.

The added advantage would be that it's compact,
cheaper, higher in output and needs less space than
a solar installation would.

Regards
Mark Harriss


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**Sprouting an old myth does not make it true. I suggest you do some actual
research before you make a comment. FYI: The actual figures for payback
(energy required for manufacture) is more like 4-5 years.

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**Depends on the cells.

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**And it will create noise and pollution in the process. Solar cells are
silent and do not produce pollution.

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**And far less convenient, noisy, polluting, requiring maintenance, fuel,
etc. All in all, a complete PITA. It would also defeat the secondary purpose
of the whole system. It would, however, satisfy the primary purpose.


--
Trevor Wilson
www.rageaudio.com.au



Re: Power generation system. Part 2



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Here are the figures I'd researched a month or so ago for another
discussion. Solar cell makers buy surplus semiconductor grade
silicon for manufacture of their cells, so they should count the
energy cost to refine silicon to this stage. There are processes
to make "Solar grade" silicon out there but none are past the lab
stage of testing: these take 1/3 of the energy to make the silicon.
At any rate here is the figures I've come up with.


The calcs assume:

1. You are living on the sunniest place on the planet with 3000Hrs
of sun per year, somewhere on the equator on a cloud free plateau,
Sydney/Melb figures will be greatly reduced as you are closer to
the south pole at sea level in air pollution.

2. The solar flux is a constant unvarying 1.4Kw per square metre
from the sunup to sundown.

3. There is no age related loss of power at all(more like average 10%
and peaking at 20%).

4. You have invented some new way to slice silicon that has no losses.
The figure is closer to 50% at the thickness I have quoted.

5. The only energy costs are that to make the silicon, nothing else.
Please not that this does not count the lack of efficiency of energy
storage in batteries, the cost of making the batteries, the cost of
making the inverter, the cost of converting the silicon into a cell
the cost of refining the metals and glass used in the solar system or
the cost of shipping and installation.

6.It also does not count the multiple sets of batteries over the life
of the system.

7. It does not count the CO2 made during the chemical combustion part
of refining the silicon with carbon from quartz.



Here's what I'd researched earlier, Trevor on the 19/05/05:

"I've read it's a six step refining process that requires 2130 KW/h per
kilo of silicon. The density is 2330 kg/cubic metre, so assume you can
slice the silicon to 0.5mm thickness and have no sawing / polishing
waste and no energy expended to saw / dope / connect the cells,you'd get
2000 square metres of silicon for just under 5 GW/hours of energy. Solar
radiation is ideally 1.395 KW/metre square by 2000 square metres cell
area @ 3000 hours per year of sun under ideal conditions at the best
spot on the planet.

This gives 8.370 GW/hrs of energy per year by 15% cell efficiency to
give 1.255 GW/hrs per year of electricity.

so 5 GW/hrs divided by 1.255 GW/hrs per year gives 3.953 years to
cover the energy costs of making the silicon?."


payback = Four years???


So in a nutshell you get 3.953 years energy payback time assuming no
losses in the best part of the planet, assuming no energy losses, that
your silicon is at least 15% efficient?? and assuming no energy went
into making the solar cell from the raw silicon.

I would put it to you Trevor, that making the raw silicon into a panel
will double that figure, shifting the panel from the world's sunniest
site on a cloud free high altitude plateau on the equator to a region
far from the equator at sea level, like Sydney, would double that figure
again as you'd no longer have the CONSTANT 1.4KW per sq metre solar flux
I used in my calcs.

    Finally a Telstra tech once told me that as a rule of thumb you
get half the energy out of a battery as you put into it, so your figure
would double again, so 4 years x 2 x 2 x 2 = 32 years assuming your
batteries never die, your inverter is 100% efficient and you solar cells
never age. If you could use/sell your solar power at the 24 Volts it
makes without needing to store or convert it you would still have a
payback of about 16 years.


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The only commonly available cell on the market with any real
usable performance WILL have this problem....regardless of
what marketing tells you Trevor. There are experimental cells
of different design but they are not available retail yet.
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It sounds like you've been listening to your solar cell
retailer Trevor, over it's lifetime, an alternator is
environmentally less polluting to manufacture than a solar
installation but would pollute more if run constantly all
day instead of when needed, which I thought your use would
be?.


Regards
Mark Harriss

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**All very interesting and unreasonably confusing. I did a quick search and
came up with more than 20 references to ENERGY payback for Silicon Solar
Cells. The WORST figure I came up with was 5 years, whilst the best was 1.25
years. Naturally, the financial payback time is in the order of 20-30 years,
at present energy prices.

To use some of your own data, it would take 11 years to refine one kg of
silicon, using a single 115 Watt panel.


--
Trevor Wilson
www.rageaudio.com.au



Re: Power generation system. Part 2


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1. It's simple math Trevor: find out how much solar energy is typical
for your location in watts per metre square, multiply that by the
efficiency for your solar cells and you get a figure for power
production for the area of solar cells you have in Watts. Assume for
simplicity that you get that wattage as long as the sun is above the
horizon so you multiply the wattage by the time to get Watt-Hours of
energy you make for a DAY.

2. Work out how many Kgs of silicon you need per square metre of silicon
and multiply that by 2130 KiloWatt/Hours per kilo of silicon.

3. So you have how much energy your cells make and how many watt hours
of power it took to make the silicon used in them. Divide the second by
the first to get how many DAYS it's going to take for the energy made by
your cells to equal the energy taken to make the silicon in them.


 > To use some of your own data, it would take 11 years to refine one kg
 > of silicon, using a single 115 Watt panel.
 >

One Kilo of silicon can make a lot more than a single 115 Watt panel.
Depends on how thin you slice it.


Regards
Mark  Harriss

Re: Power generation system. Part 2


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at least get the units right - kW*hrs not kW/hrs. the difference is
proportional to hours^2.....

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2130kW-hrs.

1 kWhr = 1kW * 3.6ks = 3.6MJ

2130kW-hrs = 7.668GJ per kg of silicon?

the specific heat capacity of silicon is 700J/(kg*K). For 1 kg, m*cp =
700J/K.

7.668GJ/[700J/K] = 10,954,286 K

thats enough to heat 1kg of Si to 11 million degrees C!!!

the melting point of Si is about 1700K so that could melt 1kg of Si
about 6,444 times.

Clearly this number is wrong.

Its out by about three orders of magnitude - if it were 2130W-hrs, that
would be enough to melt 1kg of Si six-and-a-half times, a thoroughly
believable proposition.

dividing your numbers by 1000 changes the answer somewhat, although the
methodology is sound.

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which does not alter the fact that at 115W takes 66,678,260 seconds to
use 7.668GJ, IOW 18,522 hrs = 2.1 years. Add in the various efficiency
factors, and Trevors calc is about right.

he said nothing about how many solar panels that 1kg of Si will make.

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Cheers
Terry

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Hi Terry, I pulled that figure off the net as the total energy cost to
make and refine silicon to semiconductor grade, which is where cell
makers buy their single crystal silicon:  I would imagine with constant
remelting of silicon from zone refining that it would approach that
energy figure.

  I always have trouble with my kilowatt hours terminology, thanks for
the advice.



Mark Harriss

Re: Power generation system. Part 2


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I dont buy it. They melt the Si a few times, not a few thousand times.

The physics dont lie.

Thats one problem with the web, bullshit abounds. When in doubt find
(2N+1) different sources, and make a majority decision. Seriously, it
looks like either they have screwed up the units (W-hr cf kW-hr) or have
included the energy involved in building the entire infrastructure - not
an uncommon trick with greenies, but desperately unfair - where do you
stop, pretty soon one ends up calculating the energy required to build
our entire civilisation from scratch.....

According to Goodge, Semiconductor Device Technology, ch.3 chemical
reduction is first used to purify SiO2. It then undergoes zone refining
several times (pulled thru a heater, making a molten segment that
travels along the Si rod, essentially pushing the contaminants to the
end). The end(s) are lopped off, and the resultant pure Si is re-melted,
and a single crystal is pulled (Czochralski process)

So the Si would certainly be melted several times, which is what your
number indicate assuming its W-hr not kW-hr


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I'm a pedant.... but the "/" symbol really confuses things.

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Cheers
Terry

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Yep I think so too: so I'm madly trying to find that 2130 KW-Hr figure
again, or any figure for that matter.

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Regards
Mark

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Hi Terry, here's a different site:

http://www.environmentalfutures.org/Images/williams.PDF

with a powerpoint presentation that has the same figure
for silicon production (page 12) of 2130 KWH per kilo.
This one, though does specify that this is the TOTAL cost
to get from sand to a finished silicon WAFER per kilo, not
just a kilo as I stated.

Also the author does cite references of studies for these
figures so I'm inclined to believe him. As solar cells
are made from wafers, I think it may still be a valid
comparison.

At any rate see what you think.

Regards
Mark Harriss

Re: Power generation system. Part 2


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Hi Mark, thanks for that.

Complete life-cycle energy costings....

the numbers in the table on p. 16 dont stack up:

multiply the % columns: 0.9*0.9*0.42*0.50*0.56 = 0.095

divide energy by % and add:
123/.9 + 50/.9 + 250/.42 + 250/.50 + 240/.56 = 1594kWh

Hmm, thats not quite right, probably a typo on their part, the order of
magnitude didnt change.

But clearly the erroneous figure 2130kWh is for 1kg of *processed*
wafer, and should be 1594kWh = 5.7GJ. Typical sneaky bastards, present
data in the way that serves their purpose best....because the yield is
9.5%, that 5.7GJ is "spent" on 10.5kg of raw Si, enough to melt it
(1700K) 458 times, a hell of an improvement on 6,444 times.

So if we multiply the 1600kWh by the weight of a solar cell in kg (much
less than 1kg) that will give us a fair estimate for the total energy
cost of the solar cell.

If we assume the wafer is 200mm diameter and 0.5mm thick (a guess), its
volume is 15.7e-6 m^3, so weighs about (15.7e-6 m^3)*(2330kg/m^3) =
0.0366kg, so per wafer its about 58kWh = 210MJ.

If you have some figures on Si area, thickness and power output, we can
work out the total payback time.

which pays back *ALL* of the energy used in the entire manufacturing
process.

Fun with physics.

Oh yeah, then do the same for the diesel generator. That steel didnt
smelt itself....

Cheers
Terry

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Not to mention CO2 produced from electricity used and carbon burnt for
the first step of the process.

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  I'm happy with the 0.5 mm thickness of a single cell, it may well be
thinner now, I still haven't found any processing costs for making the
wafer into a cell either which would be handy. I did find a commercial
cell efficiency of 11.5% and I would think using a solar flux figure
multiplied by the efficiency would be ok for power output.


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It'd be interesting to compare the CO2 made for both paths also.

Not only that but the genny is not used all the time, what are the
figures for continuous use. Hmmm... then there's battery costs as
well.
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Regards

Mark

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this total-cost-of-ownership thing gets pretty tricky pretty fast eh?

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look at the mic preamp gain post on a.b.s.e. I've got a link there to a
company that sells die. A typical die is 11mil thick, about 0.28mm hence
my guess of 0.5mm

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thats probably beyond me, my chemistry is not so great. But I'd be happy
to learn how...

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Re: Power generation system. Part 2



1. It's simple math Trevor: ............

Perhaps the simpler maths would be to just look at the cost of buying
panels. 50W panels used to cost about $500. How much of that is for the
energy required to manufacture them? $50? How much is a KWH? Say $0.15 -
then a 50W panel takes about 50/.15 or about 333KWH. So the 50W panel
has to make 333KWH to break even. At 5Hrs/day, this takes 333K/(5*50) or
1333 days or 3.65 years.
Alan


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