An Undergraduate Analysis Of Two Different Photovoltaic Module Types: A Comparison Completed For An Industrial Affiliate

Rowan University is committed to giving its undergraduate students an early experience in real world situations. Through the participation of Industrial affiliates Rowan University is able to get their undergraduate students involved in the innovation of cutting edge renewable energy research. During the 2007-2008 academic year Kaneka Corporation of Osaka Japan, sponsored the installation of a Photovoltaic (PV) system located at the newly created South Jersey Technical Park. This 1kW system utilizes Kaneka’s new amorphous-silicon photovoltaic modules, which are purported to being more efficient in higher temperatures. A comparison of these amorphous modules and an existing system of differing module types has been completed. This reference system being a 13.3kW array of single-crystalline modules located on the same roof, tilted at a comparable angle. Working in an engineering clinic environment modeled on the medical school model, students were to determine (if existent) the efficiency gains of the new amorphous type modules in contrast to the mono-crystalline modules on the same roof. Background The New Jersey state school Rowan University’s College of Engineering (CoE) has made a name for itself in large part due to working hand in hand with industrial affiliates from around the world. When the CoE was created thanks to a healthy endowment by an industry magnate, one of the most important aspects that the university wanted to integrate into its curriculum was a large amount of practical experience for its students. Not only would this keep things interesting but would also prepare them well for their future. The most important way this was done was by introducing what is now called the Engineering Clinic. This bases its idea on the medical school model by providing the necessary experience in a safe environment that will enable the participants to be fully capable of acting on their own in the real world, all the while providing a service to its affiliates. The details of the clinic are described in numerous papers so the sequence is not discussed here. In recent years many other papers have been written to demonstrate the usefulness of the clinic and to share many opportunities that students at this university have had to apply the clinic to innovative renewable energy and sustainability activities. In late 2007 Kaneka Corporation of Japan approached the CoE to fund an experimental Photovoltaic system that incorporates their new amorphous silicon modules which promise lower losses of performance in higher temperatures when compared to conventional solar modules. Seeing it as a great opportunity for an additional clinic project, Dr. Rowan along with his graduate student and four undergraduates added the project to their list of objectives. The first semester included the design and installation of the system including data collection for future analysis. In the fall 2008 semester, part of a clinic project entailed the analysis of the collected data to give an insight into the operational efficiency of the new module type versus two existing systems that utilize conventional multiand single-crystalline technology. Analysis A large part of engineering entails the analysis and comparison of previously collected data, in order to give a greater understanding of improvements or changes that need to be made in the future. Without the scientific process of trying to understand the operation of any given system, significant advances in technology would not be made. Hence, it is an intricate part of the curriculum at the CoE and must be included in the clinic program for students to become proficient in all aspects of engineering. That is exactly what students have done in this part of the project, and on which this paper will focus. Amorphous PV The manufacturer claims that amorphous silicon cells will convert between four and six percent of incoming solar energy into usable power. Compared to monoand poly-crystalline cells which most commonly range in the 12-17% efficiencies, amorphous types will at first glance seem inferior. However, due to several reasons this is not always the case. Their ease of manufacturing makes them less expensive per watt, but the nature of the thin-film method increases the overall area of the module per watt. A combination of these factors provides possibly the cheapest type of PV module that requires the most amount of space. The real advantage with these amorphous cells lies in their tolerance of heat. Normally efficiency drops immensely when module temperatures reach 30C°+, but amorphous cells do not suffer as greatly from increases in temperature as shown in the following section. If pertinent data can be collected on-site to help determine when if ever these module have an advantage, it can significantly help picking the right type for a new system. Module temperature and loss factors Since module temperatures will not always be available before the installation of such a system, it is important to note any correlation between them, ambient temperature and insolation. There are many other meteorological and environmental factors that can influence any direct connection between variables, ranging from precipitation and humidity to wind or overcasts. Naturally one of the strongest of these will be the wind speed at a given site. It’s ability to cool the modules is a major factor, but only basic data for the surrounding area was found – which does however give at least a small insight into its effect. Comparisons of various data were done for the months of May through September 2008, starting with the most intuitively straightforward correlation of ambient and module temperatures. A simple best fit confirms the assumption with R values ranging from .8 to .85. Figures 1&2 give example graphs of the ambient and module temperatures measured at the site for the Months of May, July and September.