Al Gore, the former US vice president, could become the world's first carbon billionaire after investing heavily in green energy companies.
Last year Mr Gore's venture capital firm loaned a small California firm $75m to develop energy-saving technology.
The company, Silver Spring Networks, produces hardware and software to make the electricity grid more efficient.
The deal appeared to pay off in a big way last week, when the Energy Department announced $3.4 billion in smart grid grants, the New York Times reports. Of the total, more than $560 million went to utilities with which Silver Spring has contracts. More...