Clean energy: How clean is it?

Clean energy is energy that can be generated with minimal or no pollution. It includes solar, wind, hydropower, geothermal, and biomass energy. Clean energy is also known as renewable energy because it comes from natural resources that are replenished on a human timescale at a faster rate than they are consumed.

Thermal energy, which is generated by burning fossil fuels — coal, oil, and gas — meets the major energy demand worldwide. However, the burning of fossil fuels produces harmful greenhouse gases (ie, carbon dioxide) and other toxic gases.

These greenhouse gases trap sunlight, leading to global warming. There is a growing need worldwide for renewable energy to slow down and eventually stop climate change.

Growth of renewable energy

The production of clean energy grew from 20% to 28% of the global electricity supply between 2011 and 2021. In 2024, over 30% of global electricity demand is met by renewable sources, and these sources are expected to contribute over 45% by 2030.

Among various clean energy options, solar and wind energy are emerging as potential replacements for conventional fossil-fuel-based energy. The main reasons for the rapid growth of solar and wind energy are increased efficiency and cost reductions over the past decade.

Environmental challenges of clean energy

Although everybody is pushing for clean energy, let us now look at how clean or green it really is. The manufacturing and disposal of solar panels and wind turbines have many adverse impacts on the environment.

The density of energy generated from windmills and solar panels is low compared to conventional energy sources due to the diffuse and intermittent nature of wind and sunlight.

Therefore, a large number of solar panels or windmills are required to replace a single unit of a thermal or nuclear power plant. For example, 20 wind turbines are equivalent to a 100-megawatt fossil-fuel turbine, which supplies electricity to about 75,000 homes.

Such a large number of wind turbines requires about 10 square miles of land, which is much higher than the space occupied by a single fossil-fuel turbine.

To generate 100 megawatts of power by solar cells may require about 200–500 acres of land. Large land requirements for solar and wind energy can affect food security by taking agricultural land.

Covering large areas with solar cells may also disrupt ecosystems and biodiversity by fragmenting habitats.

Material and manufacturing impacts

Another issue is the requirement of large amounts of materials for manufacturing and installing windmills and solar cells. The main materials used in solar cells are silicon, tempered glass, polymer encapsulant and backsheet, and an aluminium frame.

On the other hand, wind turbines require large amounts of steel and concrete for the construction of towers and foundations, cast iron and steel for the gearbox, fiberglass and carbon fiber with epoxy resin for the blades, and copper and aluminium for the electrical systems and generators.

The manufacture of solar panels and wind turbines relies on fossil-fuel-generated electricity for producing raw materials. With the increased demand for clean energy sources, the production of wind turbines and solar panels also increases, which raises electricity consumption and, consequently, greenhouse gas emissions.

In addition, hazardous pollutants such as xylene and ethylbenzene, as well as volatile organic compounds, are released into the air during the manufacturing process of wind turbines.

Disposal and waste management issues

Another major problem with green energy is the disposal of machinery after the end of its life. Both wind turbines and solar panels have an average lifespan of 25 years.

A large amount of unrecyclable plastics is expected to come from old panels and turbine blades. According to a recent estimate, decommissioning 20 wind turbines (capable of producing 100 MW) can generate four times more non-recyclable plastic waste than all the world’s recyclable plastic waste.

Both wind turbines and solar panels are coated with PFAS (synthetic chemicals used in high-performance, durable sealing materials).

PFAS-based sealants can cause many health hazards to human beings. It has been found that landfills with PFAS-coated plastics leach into groundwater.

On the other hand, many materials (e.g., lead, cadmium) used in the manufacture of solar panels are toxic, and hence improper disposal of old panels can pollute the environment.

Benefits and future considerations

Finally, clean energy sources are not perfectly “clean”, but they pollute much less than fossil fuels. In fact, wind and solar energy sources reduce greenhouse gas emissions and cause much less air and noise pollution than fossil fuels, improving public health.

According to an estimate by the International Energy Agency, to achieve net zero emissions by 2050, we must produce 90% of global electricity from renewable sources. Still, their manufacturing, land use, and waste management issues must be addressed to truly realize their potential.

Path to a sustainable future

Since no form of energy is completely clean, the most effective way to move toward a sustainable future is not only to develop renewable energy technologies but also to reduce unnecessary energy use. Energy conservation, coupled with cleaner production, will be key to building a sustainable and long-lived society.

[Suman Kalyan Pal is a Professor, School of Physical Sciences, Indian Institute of Technology Mandi. Views expressed are their own]