Solar Collector Design

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All,

For component level modeling challenges like constructing custom solar
thermal collectors, what sort of simulation tools would others recommend to
evaluate, i.e. heat transfer through different types of enclosure materials
into the receiving fluid, or different reflector shapes?

My first instinct would be to use something like IES and push the
temperatures out of range, then examine results at the surface level in
Vista.

Ideas?

--

Arpan Bakshi

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This may be what I was looking for -- SEL's CoDePro
http://sel.me.wisc.edu/codepro/new_codepro.html

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Hi!

Hm, I am curious about replies here. Wouldn't it make sense to break up
the problem? Reflector design mostly would be about radiative transfer,
so optical simulation tools would lead to an assessment of the
irradiance on your absorbing surfaces. The second step would be to find
the heat flow inside the piping as well as between pipes and surrounding.

Cheers, Lars.

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As Lars pointed out, if you are indeed investigating a concentrating
collector (with a reflector), then the problem is probably more complex than
modelling a flat plate collector due to the importance of radiative
transfer. It looks like CoDePro only models flat plate collectors, but I've
never used it. There might be other tools out there, but if the design is
truly custom, you might need to develop your own computer model in something
like EES (which is exactly what CoDePro is) or Matlab, etc.

Regardless, the most complete reference for solar collector modelling is the
book "Solar Engineering of Thermal Processes" by Duffie and Beckman.

Cheers,

Marcus Jones, LEED AP

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I agree with Marcus here. The best that you could do in IES -
practically - would be to utilise a polynomial representing the
performance of the collector. Definitely no detailed analysis of the
collector itself. The same would be true of E+.

Sounds like you could end up messing around in Trnsys or Matlab - not
something I'd like to do!

You may want to take a look at Micheal Wetter's work with Modelica at
LBNL. I don't think he's developed any solar collector models but
Modelica is definitely the way to go for general purpose physics based
component modelling.

Again, it's worth keeping an eye on the development of IDA ICE from Equa
which has the best of both worlds: a friendly user interface for
generating building models and an open interface to the underlying
component models (many of which are written in Modelica). There's a
schematic modelling interface enabling the user to build stand alone
component models as well.

Thanks for the bibliography reference Marcus.

Regards

Chris Yates

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FYI.

Much of the research in this area was done in the 1980s and was documented in numerous SERI, Sandia and Los Alamos reports. Some of it continues today. Several handbooks document this, for example Kreider's book.

Duffie & Beckman does a good job with most concentrating and tracking collector types. Kreider also had a textbook on medium and high temperature processes that covered a wider range of collectors.

For ease of use, the FCHART software, available from Klein & Beckman easily analyzes many types of concentrating collectors using the utilizability method if you know the input parameters. I believe NREL also has an on-line analysis, as does our lab at ecalc.tamu.edu.

There are also certain types of collectors that were extremely clever and good performers, although not in production today. For example the CPC collector with an evacuated tube, such as Sunmaster made. These were amazing collectors, but suffered from shattering under flash conditions. Today, evacuated tube collectors such as Thermomax do a great job and have reduced the flash problem using heat pipes. We used a collector of this type for our Solar Decathlon 2007 entry, papers and a report on this can be found on our website (we won the hot water prize). Such collectors are hands-down winners for very cold climates.

Hopefully, more clever solutions will come along like these.

Jeff S. Haberl, Ph.D., P.E., FASHRAE

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