Solar thermal Applications.

[Julius Tangka]

The last time I sent a posting on my  appropriate technology solar refrigeration systems and my need for assitance in presenting the work at the London South Bank University organised conference in Cyprus (October 2004, I recieved very harsh comments).

I have have tried to place the pictures of the system here for those who are interested. Hope it works.

src="http://www.otherpower.com/images/scimages/585/solar_refrigerator_side_view.jpg" width=80%>

If this does not work then you could also try

http://www.freewebs.com/julius_tangka/

The techincal details including the performance evaluation are available at,HPC 2004 Congress Secretariat-  Faculty Engineering, Science and the Built Environment London South Bank University.

The genrator is located inside the solar collector at the back of the system.

During the generation cycle, the ammonia in the anmmonia /water contained absorber  is vaporised and driven off. At the top of the system, the air cooled condenser transforms it to a saturated  liquid which flows by gravity through a check valve into a liquid reciever. The liquid ammonia flows through a restrictor into the evaporator located inside the unit. Block off the solar radiation onto the gernator and allow the system to cool. The resultant pressure drop will cause the ammonia to boil absorbing heat. The vaporised ammonia is reabsorbed into the genrator.

COP= 0.95.  At Miday in Dschang, Cameroon, temperatures in the genration box can get up to 95° C. Research continues. For best performance, the generator should be located outside the building and the refrigeration compartment located inside to prevent pre-cabinet heating by incident solar radiation.

[kurt]

The last time I sent a posting on my  appropriate technology solar refrigeration systems and my need for assitance in presenting the work at the London South Bank University organised conference in Cyprus (October 2004, I recieved very harsh comments).

i think that people viewed your last post with scepticism because you did not include with your post any verifiable information to show that you were who you said you were we live in the age of a con man on every corner so therefor if you want to be taken seriously when making a post like that it is up to you to prove you are who you say you are or you will not be taken seriously. if it was me making that post i would have provided reference links like the web site of the university you are affiliated with preferably with a page showing that you are on the staff there and would have given the link to hugh's site showing that you had attended one of his workshops and perhaps even contacted hugh and asked him to make a reference comment attesting to the fact that you are on the up and up. without any information to support that you were who you said you were it is not surprising that your post was viewed with great scepticism.

i think you shot yourself in your own foot in that post. a reasonable person would not expect any response other than the great scepticism that you got presenting your request in the way that you did.

[erne]

I would be interested in knowing more about what you mean by solar.. are you using the sun to heat the unit then shading or what? I have a friend who could use a machine that run on sunshine alone.. you could e-mail me with info if you don't want to post it...erne

[Julius Tangka]

Like every solar system, there must be a collector of solar radiation. My unit has collector/generator located behind the sytem. This contains a mixture of ammonia and water in a sealed container. The box is covered by two layers of glass separated by a space of 5cm. All incident solar radiation is absorbed by the black body generator located inside the box and very little is lost. Consequently the temperature rises steadily until ammonia is liberated from the generator to the piping net work. The flow of ammonia in the system with various changes in state, results in the cooling of the compartment. Only the collector assembly needs to be outside although the heavy insulation of the refrigeration chamber prevents heat gain to the system. Like mmost intermmittent systems the heat source has to be taken away to allow the generator to cool. I do this by covering the collector from solar radiation.

[Julius Tangka]

Well I still think differently. For those of us in academics, you do not always have to come out and say who you are before someone reveals your identity. I expected only interested persons to go further and that is why I wouldn't bore you with the necessary links. After all, I was only asking, for suggestions and not looking for cheap publicity.

[Frank Lussier]

I also am interested in your design.  Can you give us more info, how built it etc.. i'm interested.

thanks

Frank

[Ungrounded Lightning Rod]

My unit has collector/generator located behind the sytem. This contains a mixture of ammonia and water in a sealed container. The box is covered by two layers of glass separated by a space of 5cm. All incident solar radiation is absorbed by the black body generator located inside the box and very little is lost. Consequently the temperature rises steadily until ammonia is liberated from the generator to the piping net work. The flow of ammonia in the system with various changes in state, results in the cooling of the compartment. Only the collector assembly needs to be outside although the heavy insulation of the refrigeration chamber prevents heat gain to the system. Like mmost intermmittent systems the heat source has to be taken away to allow the generator to cool. I do this by covering the collector from solar radiation.

Have you tried the continuous ammonia/water/hydrogen/sodium chromate version of this cycle, as used in propane refrigerators?

(I've often thought that this cycle would be marvelous for solar-powered refrigeration, though probably inadequate for air conditioning.)

[brock]

Would you by chance have a link to the research you did about the differnt solar panels?  I am very curious how the differnt manufactures compare.  If you have a link could you please post it?

Thanks in advance

[elvin1949]

the only problem i see is shading the outside

 unit.

look's to be manual.

i would try to modify a solar roof vent from

a greenhouse to supply shade when needed.

just a thought

have fun

luck

later

elvin

[number42]

It is unfortunate that this project was met with such criticism. Moreover, I'm somewhat surprised that folks seem to be unaware of how solar technology is actually employed in practical, day-to-day applications around the world. Solar refrigerators using absorption technology, such as this one, have already been developed for use by medical personnel to keep vaccines refrigerated in developing nations. It has been seen as a viable alternative to using the same technology heated by kerosene (propane, butane, etc are typically not available on a reliable basis). There has also been a great deal of recent work in attempting to adapt dual Danfoss DC compressors to run directly off a PV array and store enough energy to work through the dark period for the same application. The results were not favourable.

I have had a quick look at my links but I long since deleted them. MIT, Berkley, and a number of universities have ongoing research projects so if you plug away on web searches you will eventually find their reports and designs. They're not trying to keep them secret, they just get covered up by a lot of commercial mumbo jumbo. There is also a particularly good report on the use of amporphous solar panels in Kenya including efficiency ratings, degradation over time, and durability. Surprising results that run counter to many prevailing attitudes.

One thing to consider about this absorption solar fridge. Electrolux makes an off-the-shelf fridge which runs off of 12 vdc as well as 240v and butane/propane. It does not have a thermostat for the 12v mode, but one can be made for about £5. The unit draws 5.75 amps at 12 volts so figure roughly 72 watts or, on a 70% on cycle, slightly less. The difficulty of routing thermal energy to the absorption unit may end up being less efficient and practical than a couple of decent 80 watt panels to simply drive the built-in heater. Food for thought? I run mine this way.

From the edge of the universe...

Cheers!

[number42]

Ahhh...here's one link that board users might find interesting.

http://home.att.net/~africantech/solar/amorphous/amorphous1.htm

Nothing like a different perspective to put one's own perspective into plain relief.

[number42]

Ahhh yes...one more.

A commercial site but based largely on the work of Sandia and the US Dept. of Energy (one of my former bosses).

Everything you ever wanted to know about vaccine fridges.

http://www.polarpowerinc.com/products/refrigerator/reliable-vaccine-ref.htm