"There was a general market shift from developed countries to emerging economies. China alone accounted for 36% of global renewable energy source investments," the report stated.
In developed countries, the 2015 renewable energy investments reached $48.8 billion in Europe (21% less compared to 2014), $44.1 billion in the U.S. and $36.2 billion in Japan.
For the first time, the researchers said they were able to document the consequences of nations reducing renewable energy subsidies and other incentives. Over the past four years, as the European Union decreased renewable energy subsidies, its share of global solar PV installed capacity plummeted from 75% to 41%, and the share of wind power dropped from 41% to 33%.
In 2014, for example, German lawmakers made major revisions to the country's Renewable Energy Act to curb subsidies by limiting how much wind, solar and biomass could qualify.
"This decrease was not fully matched by increasing investment in developing countries," the report stated.
Conversely, the combination of improved renewable energy technologies and cost reductions has driven down capital expenditures and operational costs, particularly for solar photovoltaics (PVs).
Challenges to renewable energy deployment, however, remain. For example, ensuring wind and solar power are deployed in the most effective locations (where consistent wind and sunlight dominate), and efficiently integrating that power into existing grid systems continues to be a challenge.
Burlington, Vermont, is one of a handful of U.S. cities that have already proclaimed 100% renewable energy use. Above is a 500kW solar array on the roof of the Burlington International Airport parking garage that began commercial operations in February 2015.
Effective and affordable technology, such as more sophisticated weather forecasting and better energy storage systems (i.e. battery and other technologies) will help decrease or eliminate the challenges.
"Appropriate policies, including regulation and market design play a fundamental role in both development of variable renewables and their efficient integration in electricity systems," the study stated.
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