Energy is an important material basis for economic and social development. The use of energy by mankind， from firewood to fossil energy such as coal， oil， and natural gas， to power generation from renewable energy such as hydro， wind and solar energy， every change is accompanied by a huge leap in productivity and major progress in human civilization. Energy， as the driving force for the development of modern society， is related to the national economy and people's livelihood， as well as to human welfare. The massive development and use of traditional fossil energy have led to increasingly prominent problems such as resource shortages， environmental pollution， and climate change， which seriously threaten human survival and sustainable development. In essence， the core of sustainable development is clean development. The key is to promote clean replacement on the energy production side， and replace fossil energy with renewable energy such as solar， wind， and hydropower.
　　Research on scientific and accurate quantitative assessment of resources is an important basis foundation for large-scale development and utilization of renewable energy. At present， the global installed capacity of hydro， wind and solar power has exceeded 30% of the total installed capacity of power sources. Although some achievements have been made in the development of renewable energy， there is still huge potential to be developed urgently. Therefore， it is of great importance to conduct a fine assessment on the resource reserves. On the basis of establishing and improving the global renewable energy resources database， the Global Energy Interconnection Development and Cooperation Organization （GEIDCO） has established an assessment system and digital fine assessment models of renewable energy resources， carried out systematic calculation and quantitative assessment of theoretical potential， technical potential installed capacity and economic potential installed capacity of hydro， wind and solar energies from a global perspective. An achievement of the Global Renewable-energy Exploitation Analysis platform （GREAN） has been made， thereby the accuracy and timeliness of global renewable energy resources assessment will be effectively improved， which provides important support for large-scale development and utilization of renewable energy in relevant countries and regions.