<human>:  What are the most recent breakthroughs in renewable energy technologies?
<bot>: Some of the most promising recent breakthroughs in renewable energy technologies include the development of efficient, low-cost solar cells; advances in the design of wind turbines; the continuing development of geothermal energy; and the increased use of biomass fuels to generate electricity. Additionally, novel technologies such as tidal energy and hydrogen fuel cells are also gaining traction.