The global middle class is growing at an accelerating rate and people want their comforts. The need for more electrical power is undeniable. The question is, how much can alternative energy sources such as solar power contribute and at what cost?
Through the next few weeks we will examine the subject of solar power generation and try to present a balanced view of its merits and its drawbacks.
Solar/Photovoltaic Cells – An Introduction
Silicon-based solar cells dominate today’s market with about a 90 % share, of which about 95 % are either monocrystalline or polycrystalline.
The solar efficiency of a silicon photovoltaic cell is governed by how well aligned its silicon atoms are. In a monocrystalline cell, the silicon atoms are all lined up, very orderly, resulting in high efficiency and long service life. Polycrystalline cells are less orderly, which reduces their efficiency; amorphous silicon cells, even less efficient. What multicrystalline and amorphous silicon cells lose in efficiency, they win back in flexibility of application and cost.
Monocrystalline Silicon Solar Cells
Monocrystalline solar cells, also called “single crystal” cells, are made from a very pure type of silicon. In the silicon world, the more orderly the alignment of the atoms, the more efficient the material is at converting sunlight into electricity. In fact, monocrystalline solar cells are the most efficient of all; efficiencies have been documented at upwards of 20%.
Monocrystalline solar cells are made out of single crystal silicon ingots, a cylindrically shaped design that helps optimize performance. Beyond being most efficient in their output of electrical power, monocrystalline solar cells are also the most space-efficient relative to their generating intensity.
Another advantage of monocrystalline cells is that they last the longest. Many manufacturers offer warranties of up to 25 years on monocrystalline PV systems.
The monocrystalline cell manufacturing process wastes a great deal of silicon, sometimes more than half. Combined with their high efficiency, monocrystallines are the most expensive of all the solar cell types. Hence, polycrystalline and thin film cells are often the preferred choice for consumers.
Polycrystalline or Multicrystalline Solar Cells
Polycrystalline solar cells, were the first solar cells introduced to industry, in 1981.
Polycrystalline cells do not go through the cutting process used for monocrystalline cells. Instead, the silicon is melted and poured into a square mold, which yields the square shape of polycrystalline. They are much more affordable as hardly any silicon is wasted during the manufacturing process.
Polycrystalline cells are, however, less efficient than monocrystalline. Typically, polycrystalline solar PV systems operate at 13 to16% efficiency. Being less efficient, they need more space to generate the same amount of electricity. Also, polycrystalline cells do not perform as efficiently as monocrystallines at high temperatures.
Thin Film Solar Cells
Another technology particularly promising for commercial applications is the thin film solar cell, which now represents approximately 5% of all cells on the market.
There are a number of thin film products using various photovoltaic substances, including amorphous silicon, cadmium telluride, copper indium and gallium selenide. Each type of material is suited to different types of solar applications.
These cells presently operate at efficiencies of 7-13% that may climb to 16% with future developments.
Thin film technologies are attractive due to their low relative cost, with mass production much easier than crystalline cells.
The market potential for thin film solar cells is promising as they are more flexible and easier to handle during manufacturing. High heat and shade have less impact on performance. However, as they are less efficient, they require more surface area to achieve the same output, making them less attractive for home-owners, better-suited to commercial applications.
Thin film solar cells have a shorter shelf life than their crystalline counterparts, hence the shorter warranties offered by manufacturers.
Next Week – Operating efficiencies and discuss the costs of installation.
Further reading:
“Types of Solar Panels” – http://pureenergies.com/us/how-solar-works/types-of-solar-panels/
“Solar Cell Comparison Chart – Mono-, Polycrystalline and Thin Film” – http://energyinformative.org/solar-cell-comparison-chart-mono-polycrystalline-thin-film/
“Types of Solar Panel – Which Type of Solar Panel is Best for You?” – http://www.c-changes.com/types-of-solar-panel
“Alternative Energy – Common Types of Solar Cells” – http://www.altenergy.org/renewables/solar/common-types-of-solar-cells.html
“Crystalline silicon” – Wikipedia – https://en.wikipedia.org/wiki/Crystalline_silicon
“Meet the battery-powered home” – The Economist – http://www.economist.com/news/science-and-technology/21651106-tesla-joins-race-help-homeowners-unplug-grid-dawn-battery-powered-home
“What are mono silicon, poly silicon and thin film solar panels?” – http://www.cleanenergyreviews.info)
Originally printed in the Duncan Journal in 2015.