COMPARATIVE ANALYSES OF ECO TOXICITY OF PV TECHNOLOGIES, AND ITS MITIGATION

Abstract

The global solar photovoltaic (PV) installed capacity has been increasing exponentially since the beginning of the current millennium and has now surpassed 1,866 GW. It is further projected to exceed 4,500–5,000 GW by 2050 if it continues to grow at the same pace. Though capacity addition at this exponential rate will help meet the ever-growing energy demand, it may bring along several environmental concerns that have not received adequate attention from researchers and policymakers so far. The output of solar PV systems is sensitive to environmental conditions, and past research shows that it fluctuates widely with wind speed, wind direction, the chemical composition of available dust, dust particle size, relative humidity, and irradiance intensity. To maintain the output of PV installations at the intended or design levels, they require frequent cleaning with fresh water, a scarce resource in many parts of the world. Apart from power output, environmental factors also affect PV reliability, and partial shading conditions (PSC) are among the most significant. PSC may be created by non-uniform dust deposition on the module, inconsistent cleaning of the module glass, bird droppings, leaves, and shading from nearby trees, electric towers, and modules in adjacent rows at low sun altitude. Under PSC, the shaded cells become non-productive or under-productive, depending on the intensity of the shade. In such situations, the affected cells become a load on the productive or generating PV cells. This implies that the cell under PSC starts consuming or dissipating energy rather than generating it, and the temperature of the affected cells begins to rise. The literature indicates that cell temperatures can reach up to 400 °C under PSC. Apart from reducing the PV system's efficiency and power output at elevated temperatures, this also affects its reliability. The high temperature gradient within the module can cause the top glass to crack in extreme cases. Under such scenarios, atmospheric oxygen enters the module through cracks. It causes the Ethylene/Vinyl Acetate (EVA), which is used as a sealant in the modules, to catch fire. The phenomenon discussed in the paragraph above is one of the dominant early failure modes of PV modules and, together with the end-of-life (EoL) waste volume, contributes to the cumulative volume of PV waste. EoL PV waste management has not received sufficient attention from researchers yet, as EoL PV waste generation has a vii temporal offset of 25-30 years (i.e., the expected life of PV modules). Although the history of PV application for power generation dates back about seven decades, the installed capacity began to grow exponentially only at the beginning of the 21st century. And hence, presently, EoL PV waste generation and its management remain a crisis in the making; however, the world has reached a stage where it is imperative to recognize the issue it is heading to face in the near future. The PV waste volume was 1000 times less than the global electronic waste generated in 2014; however, the total PV waste may reach 8 million tons by 2030 and 78 million tons by 2050 under an early-failure scenario. The infrastructure required to handle even the existing E-waste volume is insufficient in developing countries, and 90% of this volume is disposed of in unscientific ways, as PV recycling technology is yet to reach commercial viability. The additional volume of PV waste will overburden the infrastructure, which is even inadequate to handle the existing e-waste volume, if the rate of PV waste generation is not restricted. Hence, it is imperative to investigate the effects of various environmental factors on PV reliability and to devise methods to mitigate early failures. The silver lining is that, according to an estimate from the International Renewable Energy Agency, these figures could drop by 78% in 2030 and by 30% in 2050 if early failures are averted or mitigated. To address the above problem, the present research work critically analyzes the renewable energy growth trend over the last two decades and identifies various technical and environmental challenges arising from policy biases in related policies. Further, the ecological footprints of the two most widely used technologies, i.e., crystalline silicon (c-Si) and cadmium telluride (CdTe), are analyzed holistically over the entire life cycle, and the environmental impact of c-Si is found to be greater than that of CdTe, contrary to common perception. Hence, a policy change is recommended to incentivize the production and use of CdTe PV modules. Lastly, the c-Si PV modules are further evaluated for the effectiveness of the hotspot prevention mechanism under partial-shading conditions, and the lacunae in the existing commercial PV module design are identified. Based on the findings of the above research, suitable policy changes are solicited to make PV energy environmentally sustainable and thereby keep the shade of this energy technology truly green.