An Introduction

Hello to all reading and welcome to my first blog post!  I'm making this blog so that friends and family back home can all keep up on my adventures in Switzerland.

An introduction to STEP

I'm working as a research assistant this summer on the Solar Thermal Electrolysis Project, or STEP, at Valparaiso University.  I've been working on the project with Dr. Palumbo since September 2008.  This past school year I also worked on it as my senior design project.

So what exactly is STEP?  In a nutshell, we are studying the production of zinc from zinc oxide using solar energy.  Why do we want to do that?  Currently zinc is produced industrially by burning a lot of fossil fuels, which creates pollution and is also nonrenewable.  We want to show that substituting solar energy for the fossil fuels is a feasible way of creating zinc.  In addition to being used as a commodity (to galvanize steel, etc.), zinc can also be used as a fuel, either as is in a zinc-air fuel cell or by reacting it with water to produce hydrogen.  The best thing about either of those methods is that you get zinc oxide back as a byproduct, which you can put back in the solar reactor to get zinc again.

With STEP we are working at very high temperatures, ranging from 1700 to 2800 degrees F.  The reason we work with high temperatures is this:  in order for the zinc oxide to split into zinc and oxygen, a little electricity is needed.  As the temperature of the reaction increases, the amount of electricity that needs to be supplied decreases.  In fact, at just over 3600 degrees F the reaction can occur with no electricity whatsoever.  However, we stay down below 2800 degrees because of material restrictions.  As the temperature gets higher, it becomes more difficult to find materials that can withstand it.

To study the process, we built a solar reactor.  The reactor itself has gone through several iterations as we discovered various problems while running experiments.  The solar reactor operates as follows:  sunlight passes through a window at the front of the reactor and enters a small hole called the aperture.  It heats up a large graphite block that we call the core and melts the electrolyte/zinc oxide mixture in our crucible.  A small amount of electricity is supplied by the electrodes, and the zinc and oxygen flow up chimneys and through a cooling system.  The zinc collects on copper water cooling coils and in filters attached to the cooling system.

Our goal for the project is to study how changing different design and operating variables affect how the reactor performs.  Variables we can change include electrolyte composition, electrode material, crucible material, operating temperature, current density, and how much ZnO we mix in with the electrolyte.  The two performance parameters we look at are the back work ratio and the substituted solar fraction.  The back work ratio is a measure of how much electricity we put in to get zinc versus how much we would get out if we reacted the zinc with air in a fuel cell at room temperature.  The substituted solar fraction tells us basically how well we are using the sun's energy.

So what does this have to do with Switzerland?

In order for the reactor to reach high temperatures, the sunlight must be concentrated by a parabolic mirror called a concentrator.  Paired with the concentrator is an array of flat mirrors called the heliostat that tracks the sun as it moves across the sky and directs sunlight into the concentrator.  Our reactor sits at the focus of the concentrator.  The heliostat-concentrator pairing is called a solar furnace.

We are traveling to Switzerland because Valparaiso University doesn't yet have a solar furnace.  We are going to be working at the Paul Scherrer Institut in Villigen, Switzerland.  Here's a picture of their solar furnace facility:

(Image Source:  http://solar.web.psi.ch/data/facilities/?tasc)

VU will eventually have a solar furnace facility; one is being planned to coincide with construction of the new addition to Gellersen.  Another team of students is working with Dr. Duncan and Dr. Nudehi this summer to finish designing the heliostat and concentrator and begin building them.

When are you leaving!?

Everyone's favorite question!  I am leaving tomorrow for Zurich, flying direct from O'Hare.  Our flight leaves at 7:20 pm central time, and we will arrive in Zurich on Monday at 11 am local time.   I'll return to the US on August 6.

I hope you have enjoyed learning a little about what I'm working on.  If you have any questions please ask!

--Leanne

*Edit:  I made it so you can post comments without having an account.  Just make sure you let me know who you are!*