Power generation system. Part 2

[Dave Goldfinch]

On Wed, 27 Jul 2005 06:24:41 GMT, "Trevor Wilson"
<trevor@SPAMBLOCKrageaudio.com.au> wrote:

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.

Whenever I have contemplated something like this, I have always
wondered why no one has produced a small gen set that runs off town
gas ? Interruptions to the gas supply are very rare.

Would it be feasable to convert a small petrol motor to run off the
bayonet point a barbecue or heater connects to ?

Dave Goldfinch

 

[Trevor Wilson]

"Mark Harriss" <billy@blartco.co.uk> wrote in message
news:42e82742$0$837$61c65585@uq-127creek-reader-03.brisbane.pipenetworks.com.au...

Trevor Wilson wrote:


**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.



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.

**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

 

[Alan Peake]

Just wondering mate, what brand of inverter are you thining of going for?


**I have yet to determine that. If anyone has a suggestion, I would be all
ears. Here is my source:

If you want a quiet RF environment, some "pure" sinewave inverters put
out a bit of RF. Mine (SEA Voyager) puts an S5 signal on some of the
amateur bands. Can be suppressed of course - but that's more work.
It is very efficient though - even at low levels (<50W).
Alan

 

[Mark Harriss]

Trevor Wilson wrote:

**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.

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

 

[Terry Given]

Mark Harriss wrote:

Trevor Wilson wrote:



**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.


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.

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

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

 

[Terry Given]

Mark Harriss wrote:

Trevor Wilson wrote:



**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.


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.

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.

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.

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.

Regards
Mark Harriss

Cheers
Terry

 

[Mark Harriss]

Terry Given wrote:

Mark Harriss wrote:

Trevor Wilson wrote:



**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.


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.


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.


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.


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.


Regards
Mark Harriss


Cheers
Terry

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

 

[Terry Given]

Alan Peake wrote:

Just wondering mate, what brand of inverter are you thining of going
for?



**I have yet to determine that. If anyone has a suggestion, I would be
all ears. Here is my source:


If you want a quiet RF environment, some "pure" sinewave inverters put
out a bit of RF. Mine (SEA Voyager) puts an S5 signal on some of the
amateur bands. Can be suppressed of course - but that's more work.
It is very efficient though - even at low levels (<50W).
Alan

What features would you look for in a "pure" sinewave inverter? what
features would you like?

Here's what I think:

- true sinewave (even at no load)
- line interactive
- fully regenerative (eats motor loads etc)
- low (ideally no) EMI. Run an AM radio sitting on top of it...
- doesnt care which wires go to the grid, which to the load
(alas, it does care about which go to the battery)
- IP66/IP68 (run the sucker underwater...)
- drop it from 1m and give it a good boot while its running (wont die)
- programmable input PF -1...+1 (IOW can do VAR compensation)
- input can act as harmonic filter
- failsafe (fully fused, thermal modelling/monitoring etc)
- no inrush current
- sub-cycle brownout/dropout detection - bumpless power transfer
- optically isolated comms link
- user serviceable cooling fan
- liquid cooling option
- 3:1 peak to average power ratio
- > 20kHz switching frequency (inaudible)
- single- & three-phase models
- wide range of battery voltages (12-24-48V)
- built-in battery condition monitoring
- simple yet useful user interface (small LCD, a few buttons)
- optional bypass contactor

Cheers
Terry

 

[Terry Given]

Mark Harriss wrote:

Terry Given wrote:

Mark Harriss wrote:

Trevor Wilson wrote:



**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.


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.



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.


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.


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.


Regards
Mark Harriss



Cheers
Terry



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 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

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

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

Mark Harriss

Cheers
Terry

 

[Mark Harriss]

Terry Given wrote:

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

The physics dont lie.

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

Cheers
Terry

Regards
Mark

 

[Mark Harriss]

Terry Given wrote:

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.....
Cheers
Terry

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

 

[budgie]

On Thu, 28 Jul 2005 20:40:00 +1200, Terry Given <my_name@ieee.org> wrote:

Alan Peake wrote:

Just wondering mate, what brand of inverter are you thining of going
for?



**I have yet to determine that. If anyone has a suggestion, I would be
all ears. Here is my source:


If you want a quiet RF environment, some "pure" sinewave inverters put
out a bit of RF. Mine (SEA Voyager) puts an S5 signal on some of the
amateur bands. Can be suppressed of course - but that's more work.
It is very efficient though - even at low levels (<50W).
Alan


What features would you look for in a "pure" sinewave inverter? what
features would you like?

Here's what I think:

- true sinewave (even at no load)
- line interactive
- fully regenerative (eats motor loads etc)
- low (ideally no) EMI. Run an AM radio sitting on top of it...
- doesnt care which wires go to the grid, which to the load
(alas, it does care about which go to the battery)
- IP66/IP68 (run the sucker underwater...)
- drop it from 1m and give it a good boot while its running (wont die)
- programmable input PF -1...+1 (IOW can do VAR compensation)
- input can act as harmonic filter
- failsafe (fully fused, thermal modelling/monitoring etc)
- no inrush current
- sub-cycle brownout/dropout detection - bumpless power transfer
- optically isolated comms link
- user serviceable cooling fan
- liquid cooling option
- 3:1 peak to average power ratio
- > 20kHz switching frequency (inaudible)
- single- & three-phase models
- wide range of battery voltages (12-24-48V)
- built-in battery condition monitoring
- simple yet useful user interface (small LCD, a few buttons)
- optional bypass contactor

Most of those are features I am used to seeing in a commercial (i.e. not
domestic) UPS.

However review for a moment your 3:1 peak:average capability. Peak is
determined largely by current handling in the semis. Average is more determined
by thermal factors.

I can turn a 2:1 into a 3:1 very cheaply - by removing part of the heatsink.
One needs to be rather careful specifying such a ratio unless the average power
output capability is also defined adequately.

 

[Terry Given]

budgie wrote:

On Thu, 28 Jul 2005 20:40:00 +1200, Terry Given <my_name@ieee.org> wrote:


Alan Peake wrote:

Just wondering mate, what brand of inverter are you thining of going
for?



**I have yet to determine that. If anyone has a suggestion, I would be
all ears. Here is my source:


If you want a quiet RF environment, some "pure" sinewave inverters put
out a bit of RF. Mine (SEA Voyager) puts an S5 signal on some of the
amateur bands. Can be suppressed of course - but that's more work.
It is very efficient though - even at low levels (<50W).
Alan


What features would you look for in a "pure" sinewave inverter? what
features would you like?

Here's what I think:

- true sinewave (even at no load)
- line interactive
- fully regenerative (eats motor loads etc)
- low (ideally no) EMI. Run an AM radio sitting on top of it...
- doesnt care which wires go to the grid, which to the load
(alas, it does care about which go to the battery)
- IP66/IP68 (run the sucker underwater...)
- drop it from 1m and give it a good boot while its running (wont die)
- programmable input PF -1...+1 (IOW can do VAR compensation)
- input can act as harmonic filter
- failsafe (fully fused, thermal modelling/monitoring etc)
- no inrush current
- sub-cycle brownout/dropout detection - bumpless power transfer
- optically isolated comms link
- user serviceable cooling fan
- liquid cooling option
- 3:1 peak to average power ratio
- > 20kHz switching frequency (inaudible)
- single- & three-phase models
- wide range of battery voltages (12-24-48V)
- built-in battery condition monitoring
- simple yet useful user interface (small LCD, a few buttons)
- optional bypass contactor


Most of those are features I am used to seeing in a commercial (i.e. not
domestic) UPS.

some of them you wont find in commercial UPS either Yet...

However review for a moment your 3:1 peak:average capability. Peak is
determined largely by current handling in the semis. Average is more determined
by thermal factors.

yep.

I can turn a 2:1 into a 3:1 very cheaply - by removing part of the heatsink.
One needs to be rather careful specifying such a ratio unless the average power
output capability is also defined adequately.

ROTFLMAO! nicely put. Say Pcont = 3kW.

Cheers
Terry

 

[Terry Given]

Mark Harriss wrote:

Terry Given wrote:

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.....
Cheers
Terry



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

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

 

[David Sauer]

On Wed, 27 Jul 2005 23:41:04 +1000, "Phil Allison"
<philallison@tpg.com.au> wrote:

A small electric water heater takes 3.6 kW.

A basic electric stove takes 5 kW when the oven and 4 tops are all on.

A small room heater takes 2kW and an electric jug the same.

On a cold evening, while cooking dinner - the whole lot may be on.

That is over 10 kW not counting lights, TV or fridge.

Can't believe you didn't quote toaster specs. Should know them all.
1 room heater = 20 toasters, just you have to keep pushing to toast
button down all the time.

If loss of power is a concern then use an inverter for essential
lighting and power and use gas for the other essential items like the
oven and hotwater. Forget about using stuff like microwaves and
electric jugs for a few days while power is out.

Gas fridges are available, old man has a large domestic size fridge
running off BBQ gas bottles on his boat and then there's always the
Engel type smaller ones which are normally used for camping.
Maybe power the fridge a number of times a day off a genset used for
that purpose only.

Even in areas where town gas is not available there might be bottled
gas service available where they'll come and top up your tank or
supply two large tanks with a change over switch and swap them over
when you call and tell them you have an empty.

Trying to power electric hot-water and oven off an inverter is
ridiculous and a waste of money. Use the BBQ and install a back-up
instantaneous hot-water system off a 9kg BBQ gas bottle if needed for
a back-up. The later can be picked up cheap second-hand.

 

[Mark Harriss]

Terry Given wrote:

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.

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

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.

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.

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....

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.

Cheers
Terry

Regards

Mark

 

[Terry Given]

Mark Harriss wrote:

Terry Given wrote:

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.


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

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

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.



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.

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

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....


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

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

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.


Cheers
Terry



Regards

Mark

 

[Alan Peake]

What features would you look for in a "pure" sinewave inverter? what
features would you like?

Yes, I'd like all of those Terry
The Voyager is pretty good on most except the RFI. It's rated at 1700W
continuous, 2400W for 30 minutes and 3900W for 5 seconds. Starts all my
240v motors OK (biggest is half horse)and the 19" CRT monitor doesn't
dim the lights either at switch-on. (The 10HP/3.5 KVA petrol genny
coughs a bit under this load).
The THD is quoted at <4% but the switching freq is around 18KHz and I
get harmonics of this up to >14MHz.
Alan

 

[Phil Allison]

"Alan Peake"

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.

** A simpler calc is how long to pay for themselves, compared to mains
power.

A more realistic hours figure at 50 watts output is 1000 per year - takes
into account winters and cloudy days.

So 50 kWH = $ 7.5 worth of power per year.

Break even happens at 500/7.5 = 67 years.

Shame the panels will have died after 15 to 20 years.




............ Phil

 

[Alan Peake]

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