LESSONS OF EASTER ISLAND
March 17th, 2016
Active area: The surface area of the photovoltaic module responsible for the conversion of light into electricity Adhesive: A material used to bond two surfaces together Amorphous silicon cell (a-Si): A classification of thin-film photovoltaic cells composed of noncrystalline silicon that lacks long-range order and uniform lattice structure; typical Eg = 1.7 eV Antireflective coating: Typically an inorganic coating formulated to decrease the reflection and increase the transmission of specific wavelengths of light
Backsheet: A material typically composed of a polymer used as a primary barrier to the backside of a photovoltaic module Balance of Systems (BOS): Components of the installation used to mount the array to the roof and electrically connect it to the home or business
Band gap (Eg):...
Read MoreTABLE A.1
Metric System Prefixes, Symbol, and Conversion Factors
Prefix |
Symbol |
Conversion Factor |
Giga |
G |
1,000,000,000 |
Mega |
M |
1,000,000 |
Kilo |
k |
1,000 |
Hecto |
h |
100 |
Deca |
da |
10 |
1 |
||
Deci |
d |
0.1 |
Centi |
c |
0.01 |
Milli |
m |
0.001 |
Micro |
P |
0.000001 |
TABLE A.2
Example of Applying These Prefixes to Length Measured in Meters
Prefix |
Symbol |
Conversion Factor |
Gigameter |
Gm |
1 Gm = 1,000,000,000 meters |
Megameter |
Mm |
1 Mm = 1,000,000 meters |
Kilometer |
km |
1 km = 1,000 meters |
Hectometer |
hm |
1 hm = 100 meters |
Decameter |
dam |
1 dam = 10 meters |
Meter |
m |
1 meter |
Decimeter |
dm |
1 dm = 0.1 meters |
Centimeter |
cm |
1 cm = 0.01 meters |
Millimeter |
mm |
1 mm = 0.001 meters |
Entire books have been devoted to the niche discipline of polymeric photovoltaic solar cells, also known as organic solar cells. It is not the intent of this section to cover the expansive research in this area but to provide the reader with an overview of the application’s current feasibility and limitations as it relates to polymeric packaging.
Like CPV, polymeric photovoltaics are a cost-reduction technology. Specifically, the manufacturing costs can be reduced by eliminating inorganic chemistry, sourced from precious Earth metals, and using polymers, mainly sourced from petroleum by-products.
Polymeric substrates are flexible and can be formed into a number of different geometries, increasing the commercial applications for PV...
Read MoreThe goal of luminescent solar concentrators (LSC) is to simultaneously decrease costs and increase efficiency. Traditionally, LSCs are designed to absorb unusable light and re-emit it at wavelengths with the highest efficiency for the underlying PV cell. By increasing the concentration of highest – efficiency light, material costs decrease because fewer PV cells are required for the same power generation. Unlike the aforementioned concentrator techniques, there is no required tracker creating odd-shaped array footprints in residential areas.
LSCs are constructed of a polymeric lens that directs the light into the adjacent PV cells. The flat plate geometry is the most widely discussed, but cylindrical concepts have been proposed and patented since the late 1970s [21-24]...
Read MoreParabolic concentrators and reflectors use metallic surfaces to concentrate light. Parabolic concentrators are composed of two parabolic mirrors, referred to as the first and the secondary. The first mirror reflects light from the Sun to the secondary mirror elevated above the first. The secondary mirror focuses light back onto the underlying PV cell. Parabolic concentrators
often exhibit high concentration factors, and they require a dual-axes tracker to follow the course of the Sun and optimize performance. In contrast, reflectors have guidance mirrors on each side of the PV cell. Light rays from the Sun hit the mirror and bounce down to the cell...
There are a number of design considerations to ensure a lens efficiently focuses light rays onto a focal point. The two relevant for this discussion are geometry and material selection. Design considerations include the geometric shape, the wavelength with the highest quantum efficiency for the PV cell, and the refractive index of the materials used for the lens.
Fresnel lenses are the most common geometry designed for CPV concentrators [16]. A Fresnel lens is composed of a number of Fresnel zones visualized as a series of prisms with different steps in thickness cut around the lens circumference. The expected concentration factors in the assembly are typically modeled using ray tracing, specifically the edge-ray principle [17]...
Read MoreBetween 2004 and 2008, silicon supply constraints caused more than a doubling of raw material cost [14]. In an effort to further reduce production costs, PV manufacturers have tried to reduce the amount of costly semiconductor material used in the module. These initiatives have generated interest in concentrated photovoltaics (CPVs).
CPVs use polymeric lenses and packaging components to focus incident light on encapsulated cells, thereby increasing collection efficiency over a smaller cell area. Concentrated photovoltaic modules constituted 125 peak kilowatts, 0.06% of U. S. PV exports, in 2005, and 27,527 peak kilowatts, 2.8% of U. S. PV exports, in 2008 [15]. This explosive growth is the outcome of increased competitiveness due to improvements in cell efficiency...
Read MoreLooking at the cross section of a module, there is a large disparity between the refractive index of PV cells (e. g., silicon) and packaging materials (e. g., glass and encapsulant) (Table 6.5). For instance, soda lime glass is about two units away from silicon. Most PV manufacturers make packaging choices to minimize the refractive index change across the glass-encapsulant interface.
TABLE 6.5 Packaging Function with Corresponding Inorganic or Organic Materials and Refractive Index
|
They then use an AR coating on the cell to maximize light transmission...
Read More