Also check out PCM's (Phase Change Materials) Angie
significantly higher heat storage capacity by volume because of the transition phase.http://en.wikipedia.org/wiki/Phase_change_material
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| Solar Ponds http://byap.backyardmagazines.com/forum/viewtopic.php?f=31&t=4564 |
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| Author: | Angie [ Dec 5th, '08, 05:32 ] |
| Post subject: | Solar Ponds |
I tried to see if this topic had been discussed before but I didn't find anything so I am creating this new topic. Since, heating and cooling expenses seem to be the most difficult part of maintaining a year-round AP system and something that I still need to address in my 2nd prototype, I was wondering if anyone has tried solar ponds? Solar ponds, coupled with hydronic heating or as a heat source for generating electricity, could resolve a great many issues with AP- it sounds too good to be true. http://www.green-trust.org/solarpond.htm |
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| Author: | TCLynx [ Dec 5th, '08, 05:49 ] |
| Post subject: | Re: Solar Ponds |
I don't think I've seen this particular concept discussed on these boards. The average person on this forum doesn't have access to large tracts of land for heating their system but for those who are looking at large scale operations with lots of excess land in a sunny climate, it could be a good thing to learn more about. |
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| Author: | Angie [ Dec 5th, '08, 06:18 ] |
| Post subject: | Re: Solar Ponds |
The solar trough farms- Solar Energy Generating Systems (SEGS) in the Mojave Desert, CA.- uses molten salt to store solar energy and uses it once the sun has gone down. They resort to natural gas once this reserve has been used up so that they can continue operations without interruption. It sounds like this would resolve one of the biggest problems that plagues most solar and wind techologies- base load issues (the minimum amount of electricity delivered or required over a given period, at a constant rate). Additional info- http://www.motherearthnews.com/Modern-H ... -Pond.aspx |
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| Author: | JohnnyH [ Dec 5th, '08, 07:51 ] |
| Post subject: | Re: Solar Ponds |
could a SHW collector either aftermarket or home brew with some sort of regulator like a water heater t-stat and a dump type valve keep a small to medium FT warm? plumb it just like the pros do for domestic home hot water. that hardware is not inexpensive but does last a long time and there are plans for the collectors on the net that could be built and even ganged together. my old friend made one and it would make steam so they sure do the job if you could regulate and size the beast to your application sure would save a lot of electricity money to heat the tank with solar if some talented wise person could figure it all out and size properly. just my 2 cents worth, highest regards, johnny |
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| Author: | TCLynx [ Dec 5th, '08, 10:10 ] |
| Post subject: | Re: Solar Ponds |
Well it is totally different from the solar pond idea but my aquarium system is being warmed up quite well by what I'm calling a passive drain heater. The passive drain heater is bassically a coil of black drinking water pipe thrown out on the ground in the sun. When I open the valve to it, water flowing from the growbeds into the sump, goes through that coil of black tube in the sun before going into the sump tank. I have to make sure to close the valve before the sun sets on cool nights or I will be chilling my fish tank instead of warming it up. This method got my aquarium up to 78 F today and I don't think the high today got over 70 F here. I have some solar pool heater panels up on my roof that I am working on getting set up to heat water in an insulated container. Into that I have placed a coil of drinking water pipe through which I can run system water. I do not want to run system water through the solar pool heating panels due to uncertainty about the chemicals and plastics involved in those used panels. An even more important reason to not run system water through these particular panels is that the tubes that make up these panels are really small and would likely get all clogged up with solids and bio-slime way too quickly. I don't know how much I'll really be able to warm up my system but hopefully a little bit. Solar water heating is about the most efficient use of solar power out there. Points to keep in mind when thinking about solar water heating for aquaponics. 1-copper is generally bad for fish in a recirculating system. 2-research plastics to make sure they are still appropriate for drinking water even at high temperature. 3-make sure you don't cook your fish. 4-watch out for making the fluctuations greater. A solar pool heater may be able to heat water while the sun shines on it but it will act as a chiller if the water is kept flowing at night. During cold weather one probably wants to keep such a system off at night and during hot weather one should probably keep such a system off during the day. |
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| Author: | RupertofOZ [ Dec 5th, '08, 10:19 ] |
| Post subject: | Re: Solar Ponds |
Johnny.... solar heaters utilise various technologies and components.... they're not all alike... and most have distinct problems regarding the use of copper heat exchangers... They're great for hotwater generation.... ie copper can heat them typically to 60-80 centigrade.... but that's too hot for a fish tank scenario.... And the copper will kill your fish.... also the acidic nature of an AP system would mean an extremely short life span of the unit.... Having said that... there are systems available that utilise stainless steel components... and double tube evacuated tubes.... no copper components.... See discussion in this thread about some experiments I've run with such systems... viewtopic.php?f=8&t=3976 And TCL and others are using passive heat gain through poly pipe and other means.... The solar trough/solar pond stuff is entirely different.... and indeed the solar ponds use specific "salts" that are relatively expensive.... |
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| Author: | Angie [ Dec 6th, '08, 02:28 ] |
| Post subject: | Re: Solar Ponds |
RupertofOZ wrote: The solar trough/solar pond stuff is entirely different.... and indeed the solar ponds use specific "salts" that are relatively expensive.... From the preliminary research, I partially disagree with you- while you can attain higher temperatures with "expensive salts", you can still attain low temperature process heat up to 70- 80 degree celsius and in at one case, the pond reached a temperature of 93 C, which was a record high for sodium chloride ponds. (Sodium chloride is regular table salt.) http://adsabs.harvard.edu/abs/1978aes.....6.2935Z Also from: http://en.wikipedia.org/wiki/Solar_pond Efficiency The energy obtained is in the form of low grade heat of 70 to 80 °C compared to a 20 °C ambient temperature, which has an upper Carnot-cycle extractable efficiency of 1-(273.15+20)/(273.15+80)=17%. By comparison a solar concentrator system with molten salt delivering high grade heat at 800 °C would be able to convert 73% of absorbed solar heat into useful work, and be forced to divest only 27% as waste heat to the cold temperature reservoir (ambient air). The low efficiency of solar ponds is usually justified with the argument that the 'collector', being a plastic-lined pond, might potentially result in a large-scale system that is of lower overall levelised energy cost. Another thing that these ponds can be used for is raising Brine Shrimp, which may also be useful to some people as additional feed or as an additional by-product revenue stream. Also I have a request, could the title be changed to Salt Gradient Solar Ponds- it is a more accurate discription of what we are discussing here. |
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| Author: | Sleepe [ Dec 6th, '08, 06:18 ] |
| Post subject: | Re: Solar Ponds |
Also check out PCM's (Phase Change Materials) Angie significantly higher heat storage capacity by volume because of the transition phase.http://en.wikipedia.org/wiki/Phase_change_material |
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| Author: | DanDMan [ Dec 9th, '08, 06:17 ] |
| Post subject: | Re: Solar Ponds |
The solar roof ponds work very well in some climates. There are a few house that use this idea to achieve free heat and cooling, but its very climate dependent. The black body radiation into clear skies during the summer offer cooling and solar radiation during the winter offers heat. A 20 degree difference can be achieved in climates with clear night skies and low humidity and water can store a lot of energy. Just aim you infrared thermometer into the night sky and look at the temp it reads. |
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| Author: | DanDMan [ Dec 9th, '08, 06:20 ] |
| Post subject: | Re: Solar Ponds |
 As seen here: http://www.solarmirror.com/cgi-bin/faq.cgi?_recurse=1&file=1 |
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