solar energy calculations

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solar energy calculations

Postby zetreque on November 27th, 2015, 1:42 am 

What is the most basic way to use physics calculations to demonstrate how much heat energy I can obtain from the sun heating a hydro solar thermal collector? What formulas should I be looking at?

This looks like it can get very complicated when I start to take into account water flow, conductivity of different materials, convection. I just want to make it as simple as possible so I will be making a lot of assumptions such as:
The collector is a perfect black body object.
All the heat energy striking the box will be transferred into the pipes containing the water.
Assumptions about flow rates of the water.
A certain solar radiation level based on location and how long that radiation level will maintain during the day.
Lack of lost heat through airflow.
Perpendicular to the sun.

I have been looking at the Stephan-Boltzmann equation but it looks like that solves only half of what I need.
The stephan-boltzmann equation would be used to calculate how much energy is lost (radiated) by the collector right? If so I need to calculate how much is input to the collector then find the difference.
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Re: solar energy calculations

Postby wolfhnd on November 27th, 2015, 2:51 am 

I would go with a scalable design so that "units" can be added to get the desired effect. Once you build one you can then scale to need after making actual measurements. There are so many factors to consider that experimentation is a better route than calculation other than the roughest estimates.
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Re: solar energy calculations

Postby zetreque on November 27th, 2015, 2:55 am 

I have to do a final physics presentation for a physics class that taught me nothing other than how to search google for answers to keep up with the rest of the class which does the same, copies from one another finding the answers online, and paying for the answers online. Since I am building a hydro solar thermal collector anyway to experiment with and I didn't learn anything in this class, I figure I should do my physics presentation on that collector so I have to at least teach myself the physics of this collector.

My workflow I am coming up with so far is.

Watts per meter^2 (from the sun) ----> times seconds -----> joules which can be converted into watt hours or BTU's which can then be converted into delta water temperature. I can then try to come up with some thermal conductivity rates of the materials and surface area between materials to find heat flux. I can also use Stephan-Boltzmann equation to talk about how the colder it is outside the greater the deltaTemp will be and the more my collector will radiate which makes it harder to heat the water aka work for my purpose.
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Re: solar energy calculations

Postby zetreque on December 25th, 2015, 1:45 am 

Here is the result of my effort.

http://www.instructables.com/id/Solar-Hydrothermal-Collector/

If you have an account on that website, please consider voting for it in the 2x4 contest ("vote" label in the upper right corner of the screen)

I learned quite a bit through this project. I look forward to improving my calculations and playing with it!
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Re: solar energy calculations

Postby Mjr Houlihan on December 25th, 2015, 2:21 am 

zetreque » December 25th, 2015, 1:45 am wrote:Here is the result of my effort.

http://www.instructables.com/id/Solar-Hydrothermal-Collector/

If you have an account on that website, please consider voting for it in the 2x4 contest ("vote" label in the upper right corner of the screen)

I learned quite a bit through this project. I look forward to improving my calculations and playing with it!


"I want to eventually build a house that is powered almost entirely by the sun."

Something like this?

http://www.groundhouse.com/


Well, if you can't afford that yet, there are alternatives - have you heard of the garbage warrior?

http://www.garbagewarrior.com/

The documentary about him is a revelation re: the politics around this

Garbage Warrior Full Length Documentary
https://www.youtube.com/watch?v=Jnkv_qj1xUc



Your creative energy is awesome and very moving - I wish with all my being that you fulfil your dream as soon as possible and meanwhile - Hope you have a peaceful and happy day today - happy Christmas Zetreque whatever that may mean to you.
Mjr
Last edited by Mjr Houlihan on December 25th, 2015, 2:38 am, edited 1 time in total.
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Re: solar energy calculations

Postby zetreque on December 25th, 2015, 2:34 am 

Thanks Mjr Houlihan,

I'm not looking at Earthships personally though I have researched them a lot and they are a really great idea for a lot of regions. I am working around a location that isn't very suitable for them.

I'm trying to design using the concepts of:
-Passive solar (adjustable diurnally[day] and seasonally[year])
-Color changing... emissivity
-Thermal mass
-High insulation low surface area.
--Wind break and breeze.

All of which are based on the same convection, conduction, radiation calculations in this thread/project.
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Re: solar energy calculations

Postby Mjr Houlihan on December 25th, 2015, 2:42 am 

maybe something like the links I have just edited into the previous post - similar to Garbage Warrior? he is an awesome man too and done fantastic charity work in disaster zones, helping people build wells and so on. hope the documentary stays up long enough for you to see it. Once again, kindest regards
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