China is the world's biggest emitter of greenhouse gases, but it's also leading the world in clean energy investment and deployment. The growth in China's solar power sector, in particular, has been swift. According to Bloomberg New Energy Finance, China added 53 gigawatts of solar photovoltaic (PV) capacity in 2017 alone, up from 30 gigawatts the year before. Part of the reason for this large increase? The Chinese government paid subsidies to developers of solar projects so as not to build more of the coal-fired power plants fouling the air in the country.