Mr. Baruch, a veteran venture investor who once lost money on Solyndra through his firm CMEA Capital, travels frequently between the coasts, visiting his new early-stage startups, as well as giving talks on global warming.

Mr. Baruch says he has been horrified to watch CO2 concentrations in the atmosphere rise and he believes that technology can help the world keep climate change in check.

Solar panel manufacturer Solyndra, which burned through more than a billion dollars of venture and government money, became the poster child of the unrealistic promises, huge capital expenditures, as well as the government’s perilous involvement in clean tech.

Mr. Baruch’s startups are calibrating their business plans as markets change and costs of scaling the technology become obvious.

Mr. Baruch aims to build a portfolio worth $1 billion in 10 years, a goal venture investors could support.

Meanwhile Republican presidential nominee Donald Trump has said he doesn’t “Believe in climate change.” Venture investors, spooked in no small part by the way the previous wave of clean-tech adventures turned out, have provided less than $100 million for startups in the past two quarters, some of the lowest levels of investing in the sector in years, according to Dow Jones VentureSource.

Mr. Baruch forges ahead. Being in his 70s hasn’t slowed him down.