Subject: Re:Solar Powered Forges, and on

From: Russell McCrackin <[email-masked]>
Date: Mon, 9 Sep 1996 17:30:59 -0700 (PDT)

At 11:42 AM 9/9/96 -0400, you wrote:
>Only 1 square meter?! That's a pretty good output!! There are electric 
>kilns that are only 2.5kW (actually I think even less). While heating 
>directly may not be practicle because of the losses I think 1kw/m**2 is 
>actually pretty good. Say you had a 20ftx30ft roof (or collecting area) 
>utilized in this manner - thats 66kw! Equivalent to running a 90hp 
>engine continuously while the sun is shining. Unfortunately we don't all 
>live in Arizona at noon though! 8^(
>
>Hoping nobody tells me to put my portable forge where the sun don't 
>shine 8^)
>Daryl
>
>In message "Solar Powered Forges, and on", [email-masked] 
>writes:
>
>>> We have off and on been tinkering with a set up that uses fresnel 
>lenses, 
>>> at one time also available from Edmund. They used to sell one that 
>>> reaches 3000 F at the focal point, we have had only middling success 
>so 
>>> far, 
>>
 >Big Snip  
>>
>>The problem is to get enough power. One square meter will get you about
>>one kilowatt at best (that will just about run a big hairdryer).
>>Heating tiny things might work though.
>>
>>Ralph
>>[email-masked]
>>                                 
>
>Ralph has it right.  The problem is getting enough power.  And the 
definition of power is energy per unit of time.  So use the solar energy
forges you already have.  (I'll explain that statement later.)

Yes, the full sun when overhead on a clear (I do mean clear) day 
will give you energy at about the one KW or 1.5 HP rate.  But when 
the sun's rays slant the path through the atmosphere is longer, 
water vapor, dust, smog, smoke, various "air polutants,"  all reduce 
the amount arriving.

The amount arriving isn't what you are going to get to use.  A perfect 
"black body" would collect it all, but most materials will reflect more 
than 80% of what hits them.  That's the reflected light that you see
them by.

If you can use mirrors to reflect additional energy to the collector, the 
collector will get hot. (Solar One, the solar experiment by an oil company 
and the Southern California Edison Co. is an example.  But their absorber
gets visibly hot, which means that a lot  of the energy to it is radiated 
away, and does not go to the electrical generating system.)

You can cook a chicken with a solar stove, but I don't think you will
be using a direct solar energy forge with mankind's present knowledge.  

So let's all just use our present solar energy forges.  Yes, you
read me right.  Any fossil fuel you burn, natural gas, coal, alcohol, 
charcoal, old corn shucks, old emails from Rusty, it's all just stored 
up sun energy, stored up a little at a time, over a  very long time, and 
used in a very short time.  A lot of energy used in a short time is a lot
of power.

Rusty

Get it hot and hit it hard.

Never use force, get a bigger hammer.
 [email-masked]

---

From: "Duane C. Johnson" <[email-masked]>
Date: Tue, 10 Sep 1996 09:21:26 -0700

Hi all;
This is my first post to this list as I am not a smith yet.
I have been accumulating stuff to get started as I have been 
fasinated by smithing since the fiftys when my father would
get things fixed at a blacksmith shop in Mora, MN.

I have been lurking for a while. BUT I have to respond now.
I can take a joke as well as anybody. I give a lot of them 
also. I am an incurable punster. The solar thing has been
fun. BUT!

I am a designer of high powered solar heliostats. My prototype
is not designed for high temperature but it can produse high 
temperatures and high poweres when needed.

My design is using 180 square foot of mirrors that reflect the
suns power onto a receiver at the rate of about 10KWatts 
including all the losses, if no losses it would be 18KW.

This is not an insignificant amount of power. It is serious
power.

> >live in Arizona at noon though! 8^(

Well no! I realize you said "equivelant hp" but this is misleading as
the power is thermal. Just leave it at thermal power as this thread
is mostley interested in thermal power. Comverting to shaft power is
complicated and unessassary for the smith.

> >>> reaches 3000 F at the focal point, we have had only middling success

This is probably becouse you havn't had enough power to overcome 
the losses in a system like this. It is one thing to measure high 
temperatures and quite another thing to do useful work.

> >>Heating tiny things might work though.

Correct. Melting aluminium and forging steel takes real power.
The sun has plentu of power. You just need to gather enough of it.

> forges you already have.  (I'll explain that statement later.)

You have your units backwords. Energy is power per unit of time.
We must be careful in the usage of scientific units when calculations
are made. I fully understand that many like to use oldtime homey
terms when describing there historic craft. Even the oldtime smith,
though he may not have had the language correct, knew instinctivly
the difference between "power" and "energy". Power is how fast
you can heat somthing up, Energy is how much coal was needed to do it.

> water vapor, dust, smog, smoke, various "air polutants,"  all reduce

This is a misnomer. The power of the sun dosn't differ very much
due to it's position in the sky. Ok, of course, it is less near the
horison but not a lot less. (I am being vague here). Any solar forge
would of nessesity have to track the sun and not lie flat on the 
ground. 

> than 80% of what hits them.  That's the reflected light that you see

I think you are wrong abot this. The sun is a black body radiator 
at 10000 degrees kelvin. Your metal is not this hot. For the object
to reradiate 80% it would have to be at about 8000 degrees kelvin.
( Ok not exactly but not far off). Your object will accept the
majority of the power shining on it.

> away, and does not go to the electrical generating system.)

I agree with this. The fact that radiation occures dosn't stop the 
system from working though. This is one of the engineering factors to 
take into account when generating power. 
 
> be using a direct solar energy forge with mankind's present knowledge.

Of course you wouldn't cook a chicken in a forge either. We are talking
about apples an oranges here. 
 
> used in a very short time.  A lot of energy used in a short time is a lot

Come on guys think positivly about this. Solar forges can have some
positive aspects. How would you like to have a forge that:

1. Had no reactive gasses?
2. Could heat things not just to melting temp but to vapor temp?
3. Produced no scale?
4. Produced steal that was fully shiny, not black, when done?
5. Could heat things like titanium or magnesium without combustion?

> Never use force, get a bigger hammer.

I apologize if I have offended you but I think we need to 
try to work with new ideas as well as with the old. The smith
of old was working on the leading edge of technology in his time.
We need to work at the leading edge of technology of our time.

This solar thread has inspired me to look into a solar powered
forge. Anyone want to use it if it workes next summer?

Did you hear the one about the solar guy from Barstow.....?

---
 
CUL8ER

Stupid is Forever
Ignorance can be Fixed

Duane C. Johnson
Ziggy
WA0VBE
Red Rock Energy
1825 Florence St.
White Bear Lake, MN, USA 55110-3364
(612)635-5065 w
(612)426-4766 h
[email-masked]
[email-masked]
http://www.geocities.com/SiliconValley/3027/