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Concentrated solar energy

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Posted by Mark Fortune on July 17, 2006, 10:33 pm
 
I've been wondering for a while now about this...
basically I have this idea to build a form of solar collector
i've put a picture the idea on my site:
http://www.fortrex.co.uk/images/solarcollector.jpg

Much of this idea has stemmed from two noted observations:

1) that PV cells have a high cost per area
2) That PV cells are relatively efficient only in a narrow band of
wavelengths.

The device works by taking in sunlight at one end, bouncing it off a few
mirrors and through a few lenses to focus it into a beam of highly
concentrated solar energy, in much the same way a reflecing telescope does.

This beam is then split by a prism into a rainbow of wavelengths.

Seperate solar panels are then used to collect certain bands.. ie one
that is tuned for red light to absorb the red light, one that is tuned
for green light to absorb the green light etc etc.
I would like to know if it's even possible to obtain pv cells which have
a specific band gap.

The advantages of this system could be:
o A decreased area of PV cell material used, cutting costs

o Increased energy yield by absorbing a wide band of wavelengths

Of course, not being an expert in optics or PV cells (perhaps you
noticed by my novice use of terminology) I dont know if such a device
would work.. perhaps someone with more experience in these matters will
spot the seemingly obvious pitfalls of such a system.

I suspect there may be a few inherent problems:

o highly concentrated light source may overheat the panels
    I'm thinking at a passive evaporation based cooling system
    might help overcome this problem

o numerous other things which I probably havent thought about.

Of course, it's possible that someone else has already built a working
version of this and has it in production / or threw it in the skip

Please feel free to rip it apart :)

Posted by =?iso-8859-1?Q?Roland_M=F6sl?= on July 18, 2006, 4:55 am
 

Each mirror create looses
each lens create looses
the prism create looses

The system works only at full sun light

The diffuse light of a cloud sky can not be concentrated.

I think the future is more in photovoltaic with a good performance
under a cloudy sky.

Thin film photovoltaic has very good performance under clouds

http://live.pege.org/energy/thin-layer-photovoltaic.htm

Makes easy roof integration possible

http://live.pege.org/energy/photovoltaic-roof-integration.htm


--
Roland Mösl
http://car.pege.org  cars and traffic
http://live.pege.org  building and live
http://www.pege.org  


Posted by Anthony Matonak on July 18, 2006, 8:19 am
 Roland Mösl wrote:

...<snip description of concentrator system>...

Actually, the losses from reflectors and lenses are not the
problem with designs like this. You can always compensate
for a little loss by making the things bigger. Mirrors and
lenses are relatively inexpensive compared to PV cells.


This also is not as much of a problem as it might seem.
Cloudy days, by definition, have less light to start with
so you're not really losing all that much by not being
able to use this light.

You'll note that no PV system operates in the dark.

Besides, all concentrating systems like this need trackers
and this alone will increase the amount of energy they can
collect compared to fixed mounts.

The main issue with these things boil down to heat and
complexity. Ordinary solar PV panels are fairly simple,
operate under very modest temperature ranges and have
no moving parts.

Concentration systems require special PV cells, trackers
and some method of cooling. These all add to the expense
and have, so far, proved not to be cost competitive with
other PV panels. As PV cells get cheaper the idea of
concentration becomes less attractive.

Anthony

Posted by Jim Baber on August 9, 2006, 4:46 am
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
  <meta content="text/html;charset=ISO-8859-15"
 http-equiv="Content-Type">
  <title></title>
</head>
<body bgcolor="#ffffff" text="#000000">
<br>
<br>
Anthony Matonak wrote:
<blockquote cite="mid_YadnTgyfb8WBCHZnZ2dnUVZ_tadnZ2d@comcast.com"
 type="cite">Roland Msl wrote:
  <br>
  <blockquote type="cite">
    <blockquote type="cite">I've been wondering for a while now about
this...
      <br>
basically I have this idea to build a form of solar collector
      <br>
    </blockquote>
  </blockquote>
....&lt;snip description of concentrator system&gt;...
  <br>
  <blockquote type="cite">Each mirror create looses
    <br>
each lens create looses
    <br>
the prism create looses
    <br>
  </blockquote>
  <br>
Actually, the losses from reflectors and lenses are not the
  <br>
problem with designs like this. You can always compensate
  <br>
for a little loss by making the things bigger. Mirrors and
  <br>
lenses are relatively inexpensive compared to PV cells.
  <br>
  <br>
  <blockquote type="cite">The system works only at full sun light
    <br>
The diffuse light of a cloud sky can not be concentrated.
    <br>
  </blockquote>
  <br>
This also is not as much of a problem as it might seem.
  <br>
Cloudy days, by definition, have less light to start with
  <br>
so you're not really losing all that much by not being
  <br>
able to use this light.
  <br>
  <br>
You'll note that no PV system operates in the dark.
  <br>
  <br>
Besides, all concentrating systems like this need trackers
  <br>
and this alone will increase the amount of energy they can
  <br>
collect compared to fixed mounts.
  <br>
  <br>
The main issue with these things boil down to heat and
  <br>
complexity. Ordinary solar PV panels are fairly simple,
  <br>
operate under very modest temperature ranges and have
  <br>
no moving parts.</blockquote>
<ul>
  <li>But there are commercial devices like Heliodynamic's <a
 href="http://www.hdsolar.com/index.htm">Harmony</a>  out there and they=

do have certain advantages:<br>
    <ol>
      <li>The specialized solar cells produce more power per square cm
(less silicon) than typical modules.<br>
      </li>
      <li>The 3 bay Harmony actually produces more heat energy (10 kW
of hot water) than electrical energy (1.5 kW).<br>
Remember that heat can be used as the energy source to drive absorption
chillers in HVAC systems instead of <br>
electric motor driven compressors, so this heat energy can be used to
replace the high wattage compressors <br>
common in HVAC cooling systems as well as providing direct heat.</li>
      <li>It has a built in tracking mechanism to gain 25-30%
additional solar energy on a given day.<br>
      </li>
    </ol>
  </li>
</ul>
<blockquote cite="mid_YadnTgyfb8WBCHZnZ2dnUVZ_tadnZ2d@comcast.com"
 type="cite">Concentration systems require special PV cells, trackers
  <br>
and some method of cooling. These all add to the expense
  <br>
and have, so far, proved not to be cost competitive with
  <br>
other PV panels. As PV cells get cheaper the idea of
  <br>
concentration becomes less attractive.
  <br>
  <br>
Anthony
  <br>
</blockquote>
Jim Baber<br>
<pre class="moz-signature" cols="80">Email <a class="moz-txt-link-a=
1350 W Mesa Ave.
Fresno CA, 93711
(559) 435-9068
(559) 905-2204 (Verizon IN cellphone (to other Verizon IN accounts))
See 10kW grid tied solar system at <a class="moz-txt-link-rfc2396E" hre=
f="http://www.baber.org/solarpanels.jpg">"http://www.baber.org/solarpan=
els.jpg"</a>
See solar system production data at <a class="moz-txt-link-rfc2396E" hr=
ef="http://www.baber.org/solar_status.htm">"http://www.baber.org/solar_=
status.htm"</a></pre>
</body>
</html>

Posted by SJC on August 19, 2006, 10:33 pm
 Thanks for the Harmony link, that is a nice system.



Anthony Matonak wrote:
  Roland Mösl wrote:

      I've been wondering for a while now about this...
      basically I have this idea to build a form of solar collector

  ....<snip description of concentrator system>...

    Each mirror create looses
    each lens create looses
    the prism create looses


  Actually, the losses from reflectors and lenses are not the
  problem with designs like this. You can always compensate
  for a little loss by making the things bigger. Mirrors and
  lenses are relatively inexpensive compared to PV cells.


    The system works only at full sun light
    The diffuse light of a cloud sky can not be concentrated.


  This also is not as much of a problem as it might seem.
  Cloudy days, by definition, have less light to start with
  so you're not really losing all that much by not being
  able to use this light.

  You'll note that no PV system operates in the dark.

  Besides, all concentrating systems like this need trackers
  and this alone will increase the amount of energy they can
  collect compared to fixed mounts.

  The main issue with these things boil down to heat and
  complexity. Ordinary solar PV panels are fairly simple,
  operate under very modest temperature ranges and have
  no moving parts.
  a.. But there are commercial devices like Heliodynamic's Harmony out there and
they do have certain advantages:

    1.. The specialized solar cells produce more power per square cm (less
silicon) than typical modules.

    2.. The 3 bay Harmony actually produces more heat energy (10 kW of hot
water) than electrical energy (1.5 kW).
    Remember that heat can be used as the energy source to drive absorption
chillers in HVAC systems instead of
    electric motor driven compressors, so this heat energy can be used to
replace the high wattage compressors
    common in HVAC cooling systems as well as providing direct heat.
    3.. It has a built in tracking mechanism to gain 25-30% additional solar
energy on a given day.

  Concentration systems require special PV cells, trackers
  and some method of cooling. These all add to the expense
  and have, so far, proved not to be cost competitive with
  other PV panels. As PV cells get cheaper the idea of
  concentration becomes less attractive.

  Anthony

Jim Baber

Email jim@NOJUNKbaber.org
1350 W Mesa Ave.
Fresno CA, 93711
(559) 435-9068
(559) 905-2204 (Verizon IN cellphone (to other Verizon IN accounts))
See 10kW grid tied solar system at "http://www.baber.org/solarpanels.jpg"
See solar system production data at "http://www.baber.org/solar_status.htm"  



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