Salud de Sol is an ETHOS group sponsored by the University of Dayton and winner of $10,000 in a 2008 business plan competition.  This organization is requesting advice and ideas concerning a few technical problems associated with building a viable solar autoclave.  Their humanitarian project is currently being continued from last year.  The team of engineering students started a non-profit organization with a clear intent to help third world communities improve local healthcare.  Salud de Sol hopes to achieve this by providing a cost effective method for sterilizing medical instruments. Their focus is on Nicaraguan health clinics and communities that are located in areas off-grid or in places where electricity is unreliable or nonexistent.

The group’s original design does work. An operational prototype could be built if they were not restricted as to where they could obtain the parts.  The goal is to create a working model that can be mass produced using cost effective materials that are available locally in Sabana Grande, Nicaragua. There are a couple simple criteria for incorporating components into the autoclave.  If a part can be reused, then it should cost less than 10 dollars. If it cannot be reused, then it should cost no more than 1 cent.  Such strict pricing limitations will ensure that the device they end up manufacturing is affordable to the target communities.

Group Seeks To Resolve Design Issues

The current challenge facing the group is that some seals and valves created from spare parts leak or are not durable enough.  Salus de Sol needs ideas and welcomes suggestions. So far the items members have sourced locally in the Sabana Grande area to use as pressure relief valves have proven to be too insensitive.  They ended up using a commercially available version from a pressure cooker instead of trying to fashion one from scratch.  Fortunately, these were available locally without buying an entire cooker.

Another challenge has been making an accurate sterilization indicator.  The previous design had to be abandoned because of pressure being built up as the device heated.  It used a cylinder filled with polywax2000 with a washer on top.  As the wax melted, the washer would slowly sink to the bottom at a known rate.  Their next design still needs to be tested.  It uses two cylinders with one empty and the other filled with the wax.  As the wax melts, it runs into the empty compartment at a known rate.

The pressure vessel itself has a problem with the seals.  Aluminum end caps with a silicone pie pan were used in a second version.  These parts were fastened together with hex bolts and wing nuts.  This design initially worked during the pressure test.  Team members got the system up to 32 psig when they only needed a solid 15.  However, the seals failed when they added heat in the oven test.

New Team Members

While most of the original staff are still active (Anna Young, Daniel Hensel, and Lori Hanna), this year they expanded their team to include a member from the business school, Nathan David.  When they finally get the mechanism working properly and to specs, they need the business expertise for distribution purposes.  They also figure that they could get new perspective on the project outside of the engineering department during the continued research and development phase.  Another fairly new member is Erin.  She has mechanical engineering experience that will be very helpful.

These advances on the frontiers of cost effective sterilization are very exciting. Hopefully, this non-profit group will be able to reach their goals soon. In the meantime, if you need to make a smart buying decision about an autoclave for your facility, read our free report to find out what your options are.