Late 20th century, development of clean energy has been regarded as a new research subject due to prediction on fossil fuels exhaustion and environmental crisis by emission of greenhouse gas such as the carbon dioxide (CO2).
Therefore, required clean energy has special features as follows; low emission, low CO2 discharge, and massive amount of their deposits. As one of the candidates satisfied with these constrains, hydrogen (H2) has drawn much attention from researchers because of its high chemical energy and vast reservoir. A proton exchange membrane fuel cell (PEM fuel cell) has been regarded as an alternative generator to produce electricity by chemical energy of H2. Different from the conventional engines and generators, the PEM fuel cell creates electricity by direct conversion of the chemical energy between H2 and oxygen (O2) without any combustion process.
Therefore, there is no additional energy loss by mechanical friction of each moving part like an internal combustion engine. As a result, the PEM fuel cell operates with higher efficiency than the conventional engine does, and the PEM fuel cell does not emit CO2 and other pollutants. The entire process of generating electricity in the PEM fuel cell is illustrated in the following schemes.
Our main research issue on the PEM fuel cell is water management for performance and efficiency improvements.
Similar to the following diagrams in the bottom of this section, excess water supply to the cell and shortage of residual water in the cell cause serious performance drop.
Moreover, because the electrochemical reaction within the cell produces H2O, it is very hard to maintain appropriate water balance between water supply and discharge in the cell. This is why the water management has been regarded as one of key factors to enhance the cell performance.
Due to low operation temperature (<90oC) of the PEM fuel cell, water liquefaction in the cell is an unavoidable event.
In order to solve these problems, our lab is conducting two sorts of researches. For calculation of precise water amount to convey hydrogen proton (H+) according to increase in electric current, we are measuring the water movement between anode and cathode sides of the cell through the membrane. The other subject is not only defining a flooding phenomenon in the cell with quantitative standards but also finding a way to restrain the flooding to achieve cell performance increase.
In order to conduct our researches, various experimental setups is been utilizing in our lab.
A fuel cell test station with RBL 488 50V-1000A-4000W from TDI can deal with 30 cm2 cell to 300 cm2 because two kinds of fuel supply systems in the station can supply proper fuels into the cell according to the cell size and output current. Water with constant temperature is fed into the cell by an isothermal bath in order to maintain constant temperature condition of the cell.
A digital multimeter and other devices measure inner and outer operation condition of the cell as well as cell performance. Furthermore, a hi-speed camera, CCD microscopes, a CCD digital camcorder and infrared cameras are applying to our experimental apparatus in order to visualize inner condition of the cell and liquid water movement within the cell.
These days, the increasing concentration of key greenhouse gases is the most
important issue facing the world. Anthropogenic green house gases accumulate in our atmosphere and induce warming by strengthening the “greenhouse effect.” Carbon dioxide (CO2) has been increasing over the past century compare to the pre-industrial era (about 280 ppmv). Therefore, there is a significant need for the reduction of global greenhouse gas emissions, especially CO2. The CCS systems have been directly applied in industry, especially in power plants, but the problems of cost and energy efficiency remain.
There is thus a need to develop innovative technologies to reduce costs and increase energy efficiency. One of the advanced concepts for capturing CO2 in a cost-effective and energy-efficiency way is a “heat exchangeable fluidized bed reactor system using dry regenerable sorbents.” To verify this concept, thermal design is required considering fluid flow and heat transfer.
Recently, as the environmental problem is issued, the interest of alternative renewable energy sources such as??sunlight,?wind, rain,?tides, and?geothermal heat?are focused on. The photovoltaic industry is main part of renewable energy, and its market demands are increased.
In order to satisfy photovoltaic industry market demands, the polysilicon for solar cells wafer supply should catch up the demands. The polysilicon production process is very important because it effects a solar cell cost and output. There are mainly two method for polysilicon production process ? Siemens, FBR (Fluidized bed reactor).
In FBR method, hydrogen gas is injected at the bottom of reactor for fluidization and polysilicon deposition occurs on individual silicon surface.
Related with Siemens method, FBR method is much more proper for mass production because a number of silicon particles have huge chemical reaction surface. Furthermore, energy consumption of FBR method is less than Siemens method. Therefore, it is necessary to research FBR method for cost reduction and mass production.