Solar cooling with 2 clay pots ! Very cheap genius idea !

[Pirate88179]

@ Koen1:

Who needs clean drinking water when you have cold beer? (ha ha)


Bill

[Koen1]

Who needs clean drinking water when you have cold beer? (ha ha)

Hehehehe Good point Bill!

[ResinRat2]

I  always knew I would return to this project someday. I was looking at a posting by member jeanna at :

http://www.overunity.com/index.php?action=dlattach;topic=4627.0;attach=23007

that showed Donkey's solar refrigerator. This led me to consider using a stirling engine on top of the flowerpot system to see if it could give a continuous running motor that kept the temperature differential intact even with a stirling motor running on the top of the system.

The first picture shows the two clay flowerpot design that has aluminum oxide filling the center pot and sand and water filling the outer ring between the first and second flowerpots. The hope here is that the aluminum oxide center will cool or heat up at a different rate than the outer ring of sand and water as that area cools. This should draw heat away from the center and always keep the temperature difference as the water freely evaporates.

The second picture shows the same system except that now a stirling engine is resting on top of the aluminum oxide center and the area around the engine base is insulated with a wool ring to isolate it from the environment. That way all the cooling will be from the water and sand ring around it, and all heating will be from the stirling engine. I researched the specific heat values of aluminum oxide, clay, and quartz sand. These gave values of 0.21, 0.33, and 0.19 (cal/g/^oC) respectively. I am hoping this will allow the outside pot to always cool faster than the inner core.

My hope is that no matter what the outside temperature is, there will always be a temperature differential that will keep the stirling engine operational. As long as the whole system is above freezing temperatures of water that is. Although it might even work below freezing, I don't know for sure until it is tested.

I should receive my aluminum oxide in three days. At that point I will put the system together without a stirling engine and run it for several days with a temperature probe in the center. I will record the temperature differential between the system center and ambient temperature and see what kind of difference will result. This will let me know if it is worth it to purchase the engine. I saw one for about $100 US dollars that doesn't seem too unreasonable.

Thanks for your interest.

RR2

[Koen1]

Interesting idea, that.

It reminds me of an idea, not sure who came up with it first, but
it is beginning to see a bit of revival recently in the sustainable energy
industry, anyways, an idea where the heating or cooling is done by
using the earth as reservoir.
Basically, in summer when air and surface temperatures are relatively
high, temperature a few meters under ground is relatively low (as
that remains fairly constant around 18 degrees or so). A water reservoir
placed a couple of meters under ground could be used as a heat sink
and a stirling engine or thermocouple could be used to produce energy
from the thermal energy flow.
Similarly, in winter the air and surface temperature in most places is
a fair bit lower than the temperature under ground, and now the under-
ground water reservoir will be warmer than the outside air, so now
the outer environment can be used as a heat sink and thermal energy
from underground can flow out, producing energy again via the same
stirling engine or thermocouple.
This is what they're doing in many new housing projects, using the ground
as heat or cold supply.

Regards,
Koen

[ResinRat2]

Hi Koen,

Yes, similar principle. Spelunkers and well-water users know how cold water underground can be.

If this unit works like I think it will, there should be a good temperature differential (perhaps 40°F or so.) That should give a good boost to the Stirling and maybe give enough torque to perhaps run a very small motor as a generator. Those Stirlings are notoriously weak, but if the motor it powers is very small it could prove the viability of the concept. I would like to scale it up a bit in the future if good results could be obtained.

What I like is that this type of system would work even when the sun goes down. Unlike the solar-powered Stirling units they have developed that stop when the clouds block out the sun.