Solar Cells ………..are they really green energy cells??

Solar photo voltaic is classified as renewable energy source because it captures the SUN’s energy and “converts” it to electricity. So SUN’s energy is renewable and not the energy converters like solar cells! Let us understand how solar cells are manufactured.

A life cycle of a solar cell starts from the mining and processing of materials. This material is basically silica in the form of minerals and rocks like quartz and quartzite.   Then comes the solar cells that are made from the refined silicon from these mineral and rock. The cells are then fixed in modules, generally a metal  made from naturally occurring material. From the solar panels the flow goes into storage system like lithium based batteries. The lithium is mined from open cast or underground mines or extracted from minerals like spodumene or lithium bearing mica. Everything has to come from earth!! Once the solar panels and batteries complete their function, they are decommissioned and the materials some times are recycled or disposed of. The cost associated with the manufacturing of the cells to batteries are embedded in the cost of electricity that the cells generated from the Sun. But there are other costs known as the external costs. They included environmental, health and societal. These costs are well quantified by European Union’s series of “ExternE” (External cost of Energy) projects. This includes emissions generated from the manufacturing of cells, atmospheric dispersions and respiratory issues associated with such dispersions. They are not imbedded in the cost of electricity. This ExternE helps in policy decisions by the energy and transport sectors. In the latest ExternE report published by the European Commission states that photovoltaic installations in Germany has 30% higher health impacts than natural gas and Green House Gas emissions of 180 g CO2 equivalent/kWh generated is 10 times higher than the electricity generated from nuclear fuels. According to the ExternE report, the results are based on greater than 15 years old solr pv installations and module production technology. Similar study by Australia showed that solar pv emits about 100 g of CO2 equivalent/kWh of electricity generated.

A paper published by Fthenakis and Alsema in 2006 (Prog. Photovolt: Res. Appl. 2006; 14:275–280) states that the 94% of the PV system modules in 2004 that were installed to generate about 1250 MW were made of silicon. These authors with the cooperation of several European and US photovoltaic companies carried out extensive study on the life cycle inventory data that represent the present status of production technology of crystalline silicon modules (mono and multicrystalline) for rooftop pv systems. The results of the study by Germany and Australia are similar (Fig 1) very similar. The ExternE cost for health and environment estimated for solar insolation of 1700 kWh/m2/yr is about euro 0.18/kWh and for solar insolation of 1300kWh/m2/yr would be euro 0.23/kWh. This study reports that the CO2 emissions under the above conditions vary between 21 to 59 g CO2 eqi/kWh. Although this emission is less than that emitted by coal based thermal power plants, it is significant when GW are considered. At 15 % efficiency a 1 KW solar pv will emit 75 kg of CO2 during its life cycle.

Basics of solar pv cells

Manufacturing of solar pv cells is an energy intensive process, starting from mining of material, transportation, smelting, processing and manufacturing. In the entire cycle of production the main energy source is either coal based thermal power plants or electricity generated from hydroelectric power stations. Thus preparation of solar cell is closely associated with CO2 and other gases emissions as quantified above. Manufacturing of a single solar cell is associated with a large number of ancillary industries. Mining, metallurgical, electronics and other metal manufacturing industries are closely associated with the manufacturing of solar cells. By not promoting solar pv all these ancillary industries will collapse and the country’s GDP will dip….especially some of the European countries that are vehemently promote solar pv!! To prepare 1 m2 of sc-Si module the electricity required is 4620 kWh. To generate 4620 kWh 2.17 tons of coal is required (40% efficiency) and the CO2 emission is 5810 kg. To generate 1 MW of electricity nearly 14000 sc-Si modules are needed that will occupy about 4 acres of land. Thus to generate about 1.368 million kWh of electricity, the solar cells, during its life cycle, will generate huge amount of CO2. This does not include the batteries ( lithium) needed for storing the electricity generated.