help needed with bio-gas generator
Christopher Moss
My school is part of a project to use solar power to benefit the third world.
The group has decided to explore the possability of a refrigerating unit.
We will have a solar panel and 500uk pound at our disposal. Can
anyone out there help us.
Will a single solar panel be enough or will we need a secondary
source of electricity (eg a bio-gas generator producing and then burning CH4).
Thanks in advance
Jonathan Moss
Gene Alan Townsend
Jonathan:
A single PV panel is too small for all but the very smallest
refrigerator. You will also need a couple of deep cycle golf cart
batteries, and probably an inverter, so it will be difficult to meet
your cost goals, although I'm not sure the exchange rate.
The least expensive, and most appropriate means for solar powered
refrigeration in the 3rd world countries would be a solar thermal
approach using a cheap parabolic reflector, along with an "icy ball"
type absorbtion refrigerator, which could be easily made in any high
school machine shop. These have no moving parts, containing only two
small tanks and some plumbing. One ball is heated by the sun at the
point focus of the collector, charging the unit for a few hours in the
day time. The unit is then taken inside, placed in an insulated box
with the other ball inside, where it will remain cool for 24 hours if
designed properly. This device uses an ammonia cycle at 100 to 150 psi,
and should be built of iron or stainless steel.
Regards,
Gene A. Townsend
Seamus
Christopher Moss <chris...@zetnet.co.uk> said that:
>My school is part of a project to use solar power to benefit the third world.
>
>The group has decided to explore the possability of a refrigerating unit.
>We will have a solar panel and 500uk pound at our disposal. Can
>anyone out there help us.
>
>Will a single solar panel be enough or will we need a secondary
>source of electricity (eg a bio-gas generator producing and then burning CH4).
>
Hi,
First off I think that we should get this straight. The
primary beneficiaries will be yourselves who will get the benefit of
the learning development process.
The *third world* has had a considerable degree of experience at
living where they do and stupid they are not. A lot has been done in
terms of alt tech and more is yet to come in those places.
The biggest thing to understand is that the refined *sliktek* western
solution which is locally unsupportable will attract no interest in
your target areas .
The lesson which has to be learned from the wisdom of the Indian
approach is to seek exclusively *appropriate sustainable technology*.
- ie. something that can be made at factory level in country and then
repaired and maintained at village level. This would possibly include
the manufactury of spare parts by the village craft workshops.
Starting with photovoltaic electricity is probably the wrong thing to
do, perhaps a web search would reveal work that already has been done
on evapourative cooling in closed cycle refrigeration applications,
and absorption cooling. Bio -gas is quite common but much too valuable
as a cooking fuel to waste on the luxury of refrigeration.
As a hint or tip I would further suggest using a solar concentrator to
give an alternative heat source for a natural gas or paraffin burning
refrigerator. They exist already and have been around as long as I
have.
The smart step to take would be to research the combination of a solar
concentrator and a remote heat driven fridge by passing the heat
product via a hiss of optical fibre........
......now that would be good and meet a need. Piped heat hmm.
I know that these people have done work you may wish to learn from
regarding solar concentration.
John_S...@RedwoodFN.org
David jones, pom...@cris.com
jmar...@cris.com (Steve Marshall) wrote an interesting article on
solar absorbtion chilling on 21/08/96 which I would be happy to snip
to you. He brings a new perspective onto existing chiller technology.
These URLs may find the spot also.
A cheap solar tracker-
http://www.netins.net/showcase/bigdog/elcheapo.html
Absorbtion refrigeration.
http://www.elsevier.nl/catalogue/SA4/430/09710/09711/28699/28699.html
Keep an open mind try-
http://www.chatlink.com/~soltherm/
The solar thermal electric generators there can be used for
refrigeration. The solar collectors can "make ice"
with no moving parts. VERY efficient. - that is the claim made by the
site.
There is also a solar concentrator web page at
http://www.users.globalnet.co.uk/~blootl/trackers/index.htm
Try offaxis at-
http://www.igc.apc.org/raenergy/offaxis.html
Good luck and do not be in a hurry to spend your money.
Jim