Today, mankind still relies on fossil fuels to cover its global energy demand, but given the fact that the pollution produced by these nonrenewable energy resources is severely affecting the environment and are causing global warming and climate change, mankind is bound to increase the generation capacity for renewable energy.
The most developed renewable energy source on the planet today is hydroelectric power, but to replace the fossil fuels with a cleaner source of power, which would make the air cleaner for us, we need to develop all the renewable resources available on the planet.

Solar and wind power represent intermittent sources of energy because solar power can be produced only during the day when the Sun is shining, and wind power can be generated only when the wind blows with enough speed to spin the turbines.
However, to be used in the grid, the clean energy produced by a solar power plant or a wind park is usually paired with energy produced from fossil fuels such as coal or natural gas.
Renewable and Nonrenewable Energy Resources

Fossil fuels can produce energy 24/7, which means that when the demand for energy in the grid increases, both sources of energy (renewable and nonrenewable) will be used to cover the energy demand in the grid.
In order to make renewable energy the main source of power in the energy mix of the planet, scientists are working on a clean technology which is more efficient and more affordable.
Many governments in Europe and Asia are massively investing today in solar and wind power because they are aware of the fact that we need to reduce the level of pollution on the planet and stop the climate change effects.
While the U.S. government is more concerned to increase the production of fossil fuels in the country and is less interested in supporting the renewable energy sector, many private investors have decided to invest in renewable energy because they realized that clean power could produce money out of thin air and sunshine.

Alternative Energies recently posted an article about the largest solar power plants on the planet today, and the fact that India and China are competing against each other on who is developing the solar farm with the highest output of clean power in the world.
While solar power is mostly developed today in Asia and the Middle East, the capacity to generate wind energy increases in Europe.
Besides developing new materials to make solar cells more efficient and more affordable, scientists are working hard today to make nuclear fusion a reality for humankind.
The nuclear fusion reaction is considered renewable because the fuel used to power the reaction is hydrogen, which is very abundant on our planet and in the universe. The nuclear fusion reaction has been already used in the lab of different universities around the planet to produce clean power, but to make nuclear fusion commercially available, it seems that we need to wait a few more decades because the entire process is way more complex than we thought.
With or without the nuclear fusion reaction, humanity moves forward by developing all the renewable resources available today on the planet because, besides solar and wind, we can use water, geothermal energy, biomass, and tidal power to increase the presence of the renewable energy in the energy mix of the planet.
Conclusion

Only by replacing the share of the dirty fossil fuels (coal and oil) in the energy mix of the countries with low-carbon energy sources (natural gas) and renewable energy, we can reduce the air, soil and water pollution on the planet, which will help the environment to recover and ourselves to live in healthier conditions.