Environmental Engineering Reference
In-Depth Information
shut-off. Photovoltaic systems must only be connected to strong grids. Modern invert-
ers usually include the corresponding safeguarding equipment, so that the above-
defined requirements are usually met.
Fires in buildings, causing solar modules and the building envelope to burn,
may cause evaporation of certain components contained in the solar cells. For
instance, with regard to cadmium telluride and CIS thin-film solar cells critical
amounts of cadmium (Cd), tellurium (Te) and selenium (Se) may be released; for
instance combustion trials of one hour of duration have shown the release of 4 g/h
selenium (Se), 8 g/h cadmium (Cd) and tellurium (Te) /6-37/, /6-43/. Yet, the
release of these substances is below the harmful cut-off values defined for these
substances. Due to the low concentrations it is expected that even in case of com-
plete cadmium (Cd) release harmful cadmium concentrations to the surrounding
air masses can only be reached from plant capacities of 100 kW onwards /6-41/.
Roof-mounted modules of such capacities are only applied in exceptional cases
(e.g. for factory buildings). In case of fires at electrical plant components (e.g.
cables, inverters) additional amounts of harmful substances may be released to the
environment; yet, they are not specific for photovoltaic plants.
Furthermore, experience has shown that in case of extreme, hardly realistic,
elutriation (e.g. due to rain or modules being submerged into brooks or rivers) the
limits of the potable water prescription act are not exceeded.
Injury hazards due to falling solar modules, improperly mounted onto roof
panels or facades, or in consequence of electrical voltages between electrical con-
nections, may be largely excluded by adhering to the applicable standards in terms
of construction and operation of electro-technical plants.
All in all, photovoltaic power generation has a very low propensity towards
malfunctions, and malfunctions are always limited to a certain location. Provided
that the modules are appropriately installed and operated, hardly any significant
environmental impacts have to be expected.
End of operation. According to current knowledge extensive recycling of solar
modules is possible. For instance, extensive recycling of glass components is pos-
sible with only little effort. For the recycling of the other module components, by
contrast, highly sophisticated chemical separation processes are required. Amor-
phous frameless modules are best suited for recycling, as they may be transferred
to hollow glass recycling without any pre-treatment. Possible recycling methods
suitable for "classic" photovoltaic modules include acid separation of solar wafers
from the bond, transfer of frameless modules into ferrosilicon suitable for steel
production, as well as complete separation of the modules into glass, metals and
silicon wafers /6-37/. Yet, cadmium tellurium (CdTe) and CIS technologies need
to be further assessed in order to determine whether their heavy metal content pre-
cludes or requires further processing /6-42/. The ensuing environmental effects
largely correspond to the common impacts of this industrial branch on the natural
environment. However, since the recycling of photovoltaic systems is still at its
infancy the related environmental effects will be possibly reduced in the future.
Search WWH ::




Custom Search