Australian clean energy activists might have recognised some strangely familiar faces joining their ranks of late – those of their greatest adversaries in the coal industry.

Coal sector executives have been quietly switching sides to chase the lucrative profits up for grabs in green energy and – welcome or not – the experience they bring could prove vital to the increasingly desperate race to avert cataclysmic climate change. From a fifth-generation coalminer applying his hereditary knowledge to harvesting the building blocks of a clean energy economy to a fierce opponent of a price on carbon launching an energy-efficiency start-up, here are a few examples:

Altura Mining managing director James Brown – ‘It’s sad in a way ... we’ve always been proud to be coalminers’

Having dug their way from industrial revolution Wales and Scotland right through to the other side of the world in post-federation Australia, the Browns have made a living out of coalmining for at least five generations.

This family tradition is about to come to an end though with Altura Mining’s managing director, James Brown, who says he is seeking to divest all the company’s coal assets by the end of the year in order to apply his ancestral mining know-how to the extraction of lithium, a vital ingredient in battery storage for renewable energy and electric cars.

Brown says he is doing so out of a sense of responsibility – not to the environment but to his shareholders.

“It’s sad in a way,” he says. “We’ve always been proud to be coalminers – my sons, my father, grandfather, his father. I said to my wife the other day that it feels strange to be an ex-coalminer. My dad though – who’s 80 now – he loves the change. As long as we’re mining something, he’s happy.”

Brown sighs that the climate has been changing “for thousands of years”, although business trips to China have left him concerned about how coal affects air quality. He describes his transition as strictly a business decision tied to the growing number of banks and lenders refusing to issue finance to coal projects.

Brown plans to use his expertise in open-pit mine development and familiarity with the complex logistics involved in hauling resources across long distances to make the $140m Pilgangoora lithium project in Western Australia a success.

He notes there is another advantage to making the switch: “Coal has the potential to spontaneously combust and lithium doesn’t. So that’s nice to not have to worry about.”

Edge Electrons executive chairman Richard McIndoe – ‘My kids love me a lot more now’

Edge Electrons executive chairman Richard McIndoe Photograph: Edge Electrons

The former chief executive of Energy Australia left in 2014 to cofound energy efficiency start-up Edge Electrons, a move McIndoe says has improved life both at home and at the workplace.

“My kids love me a lot more now – it’s a generational thing,” he says, believing they have been influenced by a focus on climate change at school.

“I’m also now working with young people concerned about their environmental footprint. They are enthused about what they are doing, the difference they are making. Running an old coal power station isn’t as exciting as being involved in new technology.”

McIndoe says his time leading one of Australia’s most carbon-intensive energy retailers convinced him that customers today care about the environment but remain resistant to making sacrifices.

His solution is energy efficiency technology that can regulate voltage from the grid down to the minimum required to run appliances around the house, consuming less power and saving money.

McIndoe believes a focus on energy efficiency is important to move away from the “religious divide” between people who do and don’t believe in human-induced climate change.

“It’s interesting, people go ‘ugh you’re now looking to save electricity rather than increase consumption’,” he says. “Well the overall trend everyone recognises is we need to be more efficient in what we do – businesses are being killed by the cost of electricity.”

Like Brown, McIndoe became concerned about the impact of coal on air quality after working in Asia but he takes more of a Pascal’s wager approach in regard to climate change: “My view is that [maintaining high levels of carbon emissions is] not a risk that we should take.”

Although he says he is “not across the detail” of whether human activity is to blame for climate change, he argues: “Why take the risk, why deny the impact when the cost of reducing energy consumption is low and the benefits are significant?”

He was much more confident about the detail of climate change in his Energy Australia days, a period in which he led lobbying efforts against a price on carbon alongside Tony Concannon, who left IPR-GDF Suez – owners of the recently closed Hazelwood coal-fired power plant – to oversee development of a solar project in South Australia.

“People in the fossil fuel industry have credibility about this,” he says. “People like [Concannon] and myself know what the overall cost is of fossil fuels, we know the long-term prospects and we can see the rational and smart economic move is to low emissions.”

Energy Locals founder Adrian Merrick: ‘There’s a risk this might all go to ratshit’

Energy Locals founder Adrian Merrick Photograph: Energy Locals

Much like his former colleague McIndoe, as the former head of Energy Australia’s retailing arm, Merrick found himself bombarded by questions from his children that he didn’t have an answer for.

“My two kids – one eight, the other 10 – had started to ask questions about what I do,” he says. “One in particular had been essentially asking, ‘Why do you grown-ups keep screwing up the planet?’”

Unable to answer and frustrated with the lack of customer focus at his job, Merrick quit the energy giant in 2015 to create a start-up that helped the customers avoid the energy bill traps he himself had once help set up. Energy Locals also partners with community organisations to match them to the best energy solution for their needs, offering generous solar feed in tariffs and directing half the profit to good causes including renewables.

Speaking to the Guardian from an Arena renewables workshop filled with people that used to hate big suits like him, Merrick says it was unusual to be working on the same side as environmentalists who, when he worked at clean coal spruiker E.ON, would throw coal at his office and chained themselves to coworkers’ desks.

“There are plenty of activists in renewables and great, good on ’em, but I understand the commercial structures of industry and can actually make it happen,” he says.

He describes major energy companies, who recently ignored an opportunity to put all hardship customers on the lowest possible tariff, as a “pack of arseholes” and says it isn’t hard to work out why politicians spruik clean coal today by “looking at the donations”.

He notes talking down his former industry is probably not a great career move, given start-ups aren’t the most secure way to pay the bills.

“There’s a risk this might all go to ratshit, and maybe it won’t work, but I’m extremely determined to give it a bloody good go,” he says. “If I have to crawl back and ask organisations for a job I will but that is plan E or plan F at the moment.”