Page 255 - A Comprehensive Guide to Solar Energy Systems

258 A COmPreHenSIVe GuIde TO SOlAr enerGy SySTemS

It is anticipated that OPVs will make their largest contribution as a source of renew-
able electricity in the context of building integrated PV (e.g., in architectural glass, win-
dows, and roof tiles) where their light weight and the possibility of engineering the color
gives OPVs a major advantage over other classes of PV (Fig. 12.2). early stage large-scale
deployment will most likely be in the form of semitransparent shaded glass, which uses
the energy absorbed providing shade to generate electricity. Advantageously, in this con-
text the PV is incorporated in the inert gas filled gap between the glass planes and so
the module is well insulated from the environment. OPVs are particularly well matched
to this large area application because, in contrast most other types of PV, the efficiency
with which light is converted to electricity improves as the temperature increases up
to an optimal operating temperature of 40°C [22], which is easily achieved in the cavity
between the planes of double glazing, even in northern climates. In addition, the or-
ganic semiconductors used in OPVs can be optimized to harvest photons outside of the
visible spectrum, enabling the realization of highly transparent OPVs. To this authors’
knowledge, Heliatek GmbH are currently leading in this application space, offering OPVs
achieving 6% efficiency with up to 50% transparency that are also suitable for integration
into vehicles.
Another early stage application for OPVs is in consumer electronics (Fig. 12.2—top left)
and micro-generators for indoor wireless smart devices in the home and in a retail envi-
ronment to keep track of stock. unlike most other types of PV the power conversion ef-
ficiency of OPVs improves at light levels below 1 sun intensity [22,23] making them ideal
for indoor applications where the light intensity is typically less than 5% of 1 sun intensity.
Additionally, the light harvesting organic semiconductor in OPVs can be engineered to
make optimal use of the light emitted by incandescent, fluorescent, and led lights used in
commercial and residential environments.

FIGURE 12.2 Commercially available OPVs: InfinityPV HeLi-on compact solar charger (top left); Heliatek’s Heliafilm
incorporated into a car roof (in collaboration with Webasto) (top right and bottom) and on top of an inflatable
building. Bottom left photograph credited to André Wirsig.