Environmental and social aspects of solar rooftop system

In general, the application of solar PV systems is considered to be positive, as it is a sustainable technology. Converting solar irradiation into electricity using solar PV technology does not result in air, water or ground pollution and does not endanger animal or human health.
The environmental impacts are associated more with solar PV module production processes and their disposal at the end of their service lives.
During wafer-based crystalline silicon (c-Si) solar cell production, hazardous substances such as silicon tetrachloride for silicon production, hydrofluoric acid for wet-chemical etching of the wafers and lead for soldering are used, although not all solar PV module manufacturers use lead. Wastewater resulting from solar cell cleaning and texturing processes has to be treated in state-of-the art wastewater treatment plants to avoid environmental impacts. For dry etching of silicon wafers and thin-film silicon deposition sulphur hexafluoride gases are used for cleaning the deposition chambers. Sulphur hexafluoride is among the most potent and long-lasting greenhouse gases.
For cadmium telluride (CdTe)-based modules, hazardous cadmium is involved. This might also be the case in smaller amounts for certain CIGS (copper indium gallium di-selenide/sulphide) modules, which are equipped with cadmium sulphide buffer layers. The amount of cadmium would be lower than for CdTe module production, as the cadmium sulphide layer thickness is in the nanometre range. Most CIGS modules available on the market today do not contain any cadmium.
The hazardous chemicals used for solar cell production and their amounts depend on both cell technology and the manufacturing process. Proper disposal and safety procedures during manufacturing processes are necessary to keep environmental risks low and to not give rise to serious environmental or public health threats. CdTe-based modules in themselves are not hazardous, as the binary compound is stable and modules do not produce any pollutants during operation. Even in the event of a fire, almost all of the cadmium content (99.5%) would be encapsulated in the molten glass matrix (Fthenakis et al., 2005). In certain countries, such as Japan, the installation of modules containing cadmium is not allowed.
Additionally, inverters may contain hazardous materials such as lead, brominated flame retardants and hexavalent chromium.
During SHS and PPS operation, the surfaces of solar PV modules can be soiled by particles such as dust, combustion coke, bird droppings, pollen and leaves. Depending on the degree of soiling, the solar modules’ output power could be significantly reduced. Modules in desert regions with wind-blown sand and no rainy seasons suffer most. Automated or manual cleaning using water is a typical approach to minimise losses in output power. However, water consumption for module cleaning depends on location and climatic conditions.
To measure the reduction of carbon dioxide emissions, the CO2 factor for electricity production is defined as CO2 emissions per kilowatt-hour (kWh). This factor depends on a country’s fuel mix. As an example, the CO2 factor for Germany was 535 grams per kWh. The European Union (EU) targets a 20% cut in greenhouse gas emissions compared with 1990 levels. Because solar PV systems do not emit CO2 during their operation, the amount avoided can be calculated as:

CO2 avoidance = generated electricity (kWh) x CO2 factor

Nearly 1.1 billion people worldwide do not have reliable access to electricity. Stand-alone solar PV systems would improve their quality of life by providing electricity for standard home