This is obviously the sun, which should continue to deliver its solar radiation resulting from nuclear fusion of hydrogen for several billion years. Since the earth has a limited volume, the energy agents located on it (such as uranium, tritium, oil, gas, coal, etc.) are fundamentally limited.

Solar radiation can be used directly to heat things or grow plants, or indirectly as photovoltaic, wind or hydraulic energy.

Dr Claude alain Roulet thank you for your contribution to the discussion

Wind energy, as always, was the highest contributor to the total renewable power production. The percentage of solar energy produced in the overall renewable power production comes next to wind and is typically reduced during the monsoon months. At present, wind power is the most efficient method of sustainable energy production. In fact, it's more than twice as efficient as its closest competitor (geothermal). Solar energy, much like wind, is one of the most sustainable energy sources currently available. In fact, given its modular and scalable nature where it can be utilized as part of massive solar fields or mounted on individual homes it may be the most practical form of sustainable energy in use today.Increasing energy efficiency for countries leads to reduced environmental pollution and increased competition. Today, the local, regional and global negative effects of the traditional energy production and consumption technologies on the people, environment and natural resources have come to a serious state. Wind energy is one of the most sustainable forms of energy currently available. It harnesses the power of naturally moving air to spin wind turbines, which in turn generate electricity. Not only is this great because it provides a regenerative form of energy, but it also does so without greenhouse gas emissions. Solar and wind energy have continued to occupy the top spots in terms of the cheapest renewable energy sources. Both energy sources cost significantly less than fossil fuel alternatives and continue to become more affordable every year. All renewable energy sources are strong contenders for the title of 'greenest energy source' since they harness carbon-neutral sources of energy such as the Sun or wind and don't cause air pollution, putting them leagues ahead of coal or gas power. Renewable energy technologies play a crucial role in sustainable development by reducing greenhouse gas emissions, improving energy security and providing access to energy to communities that previously lacked it. Renewable energy technologies, such as solar, wind, and hydropower, can play a critical role in promoting sustainable development in India by reducing greenhouse gas emissions, increasing energy security, and promoting rural electrification. Renewable energy sources such as wind, hydroelectric power, solar, and geothermal energy are generally far more sustainable than fossil fuel sources.

@Rk Naresh As permanently reminded by the IEA : "Energy Efficiency is our first Resource"