Page 66 - Alternative Energy Systems in Building Design

CONCENTRATORS 43

PDOT (ETHEYLENEDIOXYTHIOPHENE)

ITO (INDIUM TIN OXIDE)
ALUMINUM

PET (POLYETHYLENE TEREPHTALATE) FOIL
Figure 3.10 Polymer solar cell layers.

process is achieved by means of special enzymes that strip electrons from glucose, free-
ing them to generate electric current, much as in fuel cells.
It is estimated that the average person’s body theoretically could generate 100 W of
electricity using a bionanogenerator. The electricity generated by bionanoprocesses
perhaps someday could power body-embedded devices such as pacemakers and blood
circulation pumps. It is also suggested that the future development of bionanogenerator
robots, fueled by glucose, could be embedded to perform various bodily functions. At
present, research conducted on bionanogenerators is still experimental, but progress in
the field holds significant prospects for advancing the technology. Figure 3.10 shows
polymer solar cell layers.

Concentrators

Concentrators are lenses or reflectors that focus sunlight onto solar cell modules. Fresnel
lenses, which have concentration ratios of 10–500×, are mostly made of inexpensive
plastic materials and engineered with refracting features that direct sunlight onto the
small, narrow PN-junction area of cells. Module efficiencies of most PV cells, discussed
earlier, normally range from 10 to 18 percent, whereas concentrator-type solar cell tech-
nology efficiencies can exceed 30 percent.
In this technology, reflectors are used to increase power output by either increasing
the intensity of light on the module or extending the length of time that sunlight falls
on the module. The main disadvantage of concentrators is their inability to focus scat-
tered light, which limits their use to areas such as deserts.
Depending on the size of the mounting surface, solar panels are secured on tilted struc-
tures called stanchions. Solar panels installed in the northern hemisphere are mounted
facing south, with stanchions tilted to a specific angle. In the southern hemisphere, solar
panels are installed facing north.