Sustainable+Energy+-+Solar

Intro to Technology Development - TEM194

ALTERNATIVE ENERGY:The Solar Solution Michael Deegan **Introduction to Solar** As an alternative energy, solar exists on the precipice of large scale implementation. Once an expensive niche technology, widespread acceptance regarding the advantages of solar energy has resulted in the development of new technologies which are uniquely positioning solar energy as the alternative power of the future. Despite this recent emergence as one of the leading alternative energies, solar energy possesses a long and storied history. This history coicides with our own development as shows the progression of the technology to its current state. The manner is which this technology has developed, and the way in which it operates, are key to understanding the current state of solar technology. Recent advances are quickly removing the limitations that have held back solar energy from mainstream implementation. So, in order to understand the path solar is currently taking, we need to understand the path it has already traveled.

**The History of Solar Energy**
As the development of solar energy has been an ongoing process since around 7 B.C., a detailed breakdown of its total development would be impractical. Despite this, the best way to see where any technology is going is to see where it its been. As such, ask any child with a magnifying glass and an anthill about the development of solar energy, and the answer given may not be too far from the truth. Trends in solar energy began around the 7th Century B.C., where glass with magnifying properties was used to set this on fire. This continued into the 3rd and 2nd Centuries B.C., with many more things being set on fire by intensifying the sun. However, technological advances now allowed for the fires to be set with polished metals and mirrors.

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This trend continued unabated until about 1839, when French scientist Edmund Becquerel discovered the properties of photovoltaic electricity generation. Then, in 1873, Willoughby Smith discovered the photoconductive properties of selenium. This lead to the 1883 development of the first selenium wafers by Charles Fritts, an American. All of this burning and studying finally resulted in the first photovoltaic (PV) cell being created in 1954 by Daryl Chapin, Calvin Fuller, and Gerald Pearson. Their initial invention operated with a quite respectful 4% efficiency. With the technology established, a company named Hoffman Electronics made impressive progress in increasing the efficiency of photo cells, reaching 14% by 1960. From here, the development of solar technology began to snowball in the advent of new materials with which to develop the PV cells. Silicon and thin film PV cells broke new threshholds in efficiency and reduced production costs. The 1990s saw the first major use of solar in the distribution systems with Pacific Gas & Electrics's 500 Kilowatt system in Kerman, Ca. Though only acting as an aide for a distribution feeder, this was proof that solar technology had developed enough to become a presence on the world's power generation front. 1======

Without the ability to harness the energy of the sun, solar energy would not be the alternative energy leader we know today. The primary means by which solar energy is converted to electrical energy is through the use of photovoltaic cells (PV). To simplify an exacting, complicated science, PV cells are constructed of semiconductor materials, usually silicon. When the energy from the sun strikes the surface of the cell it causes the release of electrons. These electrons are channeled by the cells to external contacts where the electricity can be utilized. However, the electricity generated by PV cells is a DC, or direct current. The current used in your average home or business, though, is known as AC, or alternating current. The final step in harnessing the sun's energy is the application of an inverter, which turns the direct current generated by the cells into a usable alternating current for homes, businesses, or industrial applications.
 * How Does Solar Energy Work?**



The key to effective utilization of solar energy lies in the efficiency of the photovoltaic cells. The first PV cells, developed in 1954, operated with 4% efficiency. As technology has progressed, though, current PV cells can see energy conversion rates climb as high as 22%. 1 However, increasing the efficiency of PV cells increases their manufacturing costs. This has created the largest limiting factor in solar technology: Cost. The operating efficiency enjoyed by today's solar cells comes at the expense of high production costs. Improving efficiency while decreasing production costs are the motivating factors behind the current state of solar technology.



**Emerging Trends and New Technology**
Solar energy harnessed through PV cells is an effective means of reducing the carbon footprint of a home or business. However, for solar energy to continue to gain momentum as a viable alternative to traditional electricity generation methods, it must establish its ability to be used on a distribution-level scale. As the most efficient PV cells are very expensive, installing a huge network of them is usually not financially practical. Recent advances in solar technologies, though, have turned some older ideas into the forerunners of the future. One such technology is known as solar thermal energy. Instead of generating electricity using PV cells, solar thermal energy develops energy in a similar fashion to the manner in which a magnifying glass combusts an unlucky ant: Solar thermal energy is developed by concentrating the heat energy from the sun. This heat energy is focused by thousands of small mirrors which are used to intensify the sun's heat onto a solar tower. The solar tower is essentially a boiler which, when heated, develops steam that is used to spin an electricity developing turbine. One company, eSolar, has been pivotal in developing this technology. The key to this tech are the mirrors which used to heat the solar tower. Cheap mirrors are less effective but expensive mirrors drive up costs. As a means to combat this, eSolar has developed a proprietary software which it uses to focus its mirrors into a perfect parabola on the solar tower. The effectiveness of the software allows for the use of inexpensive mirrors, 176,000 inexpensive mirrors. 2

With solar's primary limiting factor being cost, does this mean that the photovoltaic cell is being phased out of future technological advancements? Well, as it turns out, the PV cell is doing just fine. Recent developments in PV cell technology and use are allowing for decreases in their manufacturing costs. A large component of the manufacturing costs is the expensive, pure silicon required to bring up the efficiency of PV cells. A new type of cell, called the Nanopillar Cell, eliminates the need for the use of the crystalline silicone. Instead of silicone, the new cells utilize pillars of cadmium sulfide and cadmium telluride 500 nanometers. Using these materials, they are able to increase the efficiency of the cells and potentially lower the cost by almost 10 times that of a comparable silicon-based PV cell. 3 Another manner of lessening the cost of solar energy installations is the use of solar troughs. Solar troughs represent an amalgamation of design between solar thermal technology and PV cells. With solar troughs, also known as solar concentrators, the light shone onto expensive PV cells is concentrated through the use of cheaper mirrors. The concentrating effect of the mirrors allows for the use of less PV cells to achieve comparable power outputs. An upstart company, Skyline Solar, has shown that solar concentration can increase the amount of light hitting a PV cell by a factor of 10. This increase is also reflected directly in the power output at the cells. 4

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For students looking to pursue a degree with connections to alternative energies, ASU offers two distinct programs. While both programs are in the engineering fields, they are through different schools. The first degree program is a traditional electrical engineering degree offered through the Ira A Fulton School of Engineering. This degree requires 120 credit hours and offers technical electives, such as EEE 498 Solar Energy, which are specifically geared toward alternative energies.======

[|Electrical Engineering Degree Map] The second degree program is electronics engineering technology with an emphasis in alternative energy offered through the College of Technology and Innovation. This degree requires 126 credit hours. Term 7 of this program offers several classes classes related to solar energy, such as ALT 410 Solar Cells and Modules and ALT 425 Applied Photovoltaics.

[|Electronics Engineering Technology Degree Program]

FOOTNOTES:

1. United States Department of Energy. "The History Of Solar." //Energy Efficiency and Renewable Energy//, http://www1.eere.energy.gov/solar/pdfs/solar_timeline.pdf. 2. Woody, Todd. "A High-Tech Entrepreneur on the Front Lines of Solar." //Yale Environment 360//, Last modified March 3, 2010. Accessed February 5, 2012. []. 3. Patel, Prachi. "Nanopillar Solar Cells." //Technology Review: Published by MIT//, Last modified July 6, 2009. Accessed February 16, 2012. []. 4. Bullis, Kevin. "Cheaper Solar Concentrators." //Technology Review, published by MIT//, Last modified May 4, 2009. Accessed February 17, 2012. http://www.technologyreview.com/business/22582/?mod=related.