[Answer] Is So-Called Clean Energy Really Clean? We often talk about promoting solar and wind power, but are these energy sources truly pollution-free?

[Answer] Is So-Called Clean Energy Really Clean? We often talk about promoting solar and wind power, but are these energy sources truly pollution-free?

The cleanliness of energy needs to be understood from two perspectives: the inherent characteristics of the energy itself, and the processes and technologies by which we use it under current technical conditions.

Essentially, all forms of energy used by humanity, except nuclear energy, come from different forms of stored solar energy. Fossil fuels (coal, oil, natural gas) and bioenergy (combustion, fermentation, etc.) originate from photosynthesis driven by solar energy; tides, hydropower, and wind energy come from the thermal effects of the sun; and solar energy itself (photovoltaic power generation and solar thermal heating) comes from the photoelectric and thermal effects of sunlight. On the timescale of human activity, fossil fuels and nuclear energy are considered non-renewable resources (energy cycles spanning hundreds of millions of years far exceed the scale of human energy use), while wind, hydropower (including tidal energy), solar energy (photovoltaic and solar thermal), and bioenergy are renewable. From the perspective of sustainable human development, assuming no major breakthroughs in basic science in the near term, renewable energy is the ultimate option that can allow humanity to continue, while non-renewable energy can only serve as a transitional solution. However, humanity’s current dependence on fossil fuels and nuclear energy, the contradiction posed by energy scarcity, and the insufficient development of renewable energy technologies all deserve serious attention and caution.

Now, on the issue of pollution. Under current technological conditions, humanity still relies primarily on combustion to use fossil fuels. Excessive combustion raises the proportion of carbon dioxide in the atmosphere, creating the greenhouse effect and driving continued global temperature rise, with potentially catastrophic consequences for all humanity. On this level, any use of fossil fuels constitutes environmental pollution. That said, compared with the severe pollution caused by nitrogen and sulfur compounds released from burning coal and oil, natural gas—which mainly produces carbon dioxide—can be considered relatively low-pollution. In the short term, cleaner coal technologies and energy-use methods centered on natural gas and other fuels that mainly emit carbon dioxide represent the minimum baseline for human energy use.

Wind, hydropower, and solar energy do not create additional pollution in their energy form and therefore belong to the category of clean energy (geothermal energy also falls into this category). However, because wind is unstable by nature, its reliability is constrained, and at present it still cannot serve as a primary energy source. The total exploitable amount of wind and hydropower is also limited by technological capability and natural conditions, and cannot fully meet present and future energy demand. Solar photovoltaics cause significant environmental pollution during manufacturing, especially in the purification of silicon materials, and their efficiency still needs further improvement. The long-term environmental impacts of building large hydropower stations also require further observation and research. Nevertheless, although wind, water, and solar energy still have many shortcomings today, they are humanity’s best choice for the future—and perhaps the only one. Overall, their use is low-pollution and sustainable.

Finally, nuclear energy is a Pandora’s box among energy sources. In formal terms, because of its raw material constraints, nuclear fission, like fossil fuels, can only be a transitional option rather than the ultimate solution to humanity’s energy problem. Controlled nuclear fusion, meanwhile, remains an untamed beast; whether it can be mastered, and when, is still unknown. Humanity’s future and hopes, of course, cannot depend entirely on it.

So before energy technology makes major advances sufficient to support sustainable human development, are we left with no choice but to continue down the current path and wait helplessly for decline? Of course not. Since the Industrial Revolution, humanity has used energy under the assumption that it is inexhaustible, in a crude and disorderly way. This has made energy waste—and the additional pollution it creates—especially severe. Improving this situation can, to a considerable extent, alleviate the energy crisis until technological innovation or scientific breakthroughs arrive. In terms of improving comprehensive energy utilization, applying advanced computer technologies—such as big data, the Internet of Things, and machine learning—to integrate existing clean energy sources, while also using energy in the forms of electricity, cooling, and heating, can improve efficiency and reduce waste. This so-called “smart energy” solution is an effective path forward, and it is also our present responsibility and commitment.