The solar energy harnessed and used measures human civilization.
8.1 Principle 5
The efficiency of renewable energy such as biomass, solar, and wind should be maximized for all the EEIS. In gauging a civilization, mankind is at its infancy because only 0.75% of solar energy is currently harnessed for human activities. If the efficiency of solar cell were to double, the amount of renewable energy harvested could increase significantly. For example, if 2% of solar energy that reached the Earth could be efficiently utilized, human civilization could reach to the next level. If 2% of energy in the Milky Way galaxy reached the Earth and were harnessed by humans, mankind could colonize most nearby planets. However, it is estimated that about 100 years is needed to harvest 2% of the solar power.
To reduce operation cost of WWTP, the best way is to generate renewable energy such as electricity and heat while increasing energy efficiency of the WWTP. Therefore, energy efficiency ...