But the very phrase 'clean tech' irks Tesla's Yu. 'Typically, when you talk about clean tech, it's usually a trade-off between performance and cost. But clean tech cannot be charity tech - it's got to be technology that delivers value people want to buy,' he says.

'Personally, I don't see clean tech as an industry on its own,' says Japan-based Yu, visiting Hong Kong for the HKTDC's 6th annual Eco-Expo. 'I see it as an extension of the energy industry, an extension of the automotive industry, it's just the next generation of energy whether its wood, coal, oil or solar.'

Wu's sentiment is echoed by Yee Tak-chow, Hongkong Electric's general manager for corporate development. 'Clean energy has long been adopted by our ancestors, but somehow gradually disappeared or was ignored in modern life,' he says. 'Many of these were actually built on traditional engineering principles.'

According to Hong Kong-based Jari Vepsalainen, director of The Switch, a wind turbine component firm with manufacturing facilities in China and Finland, there is a huge need for all types of engineers to develop and implement clean tech in Asia. Talent is sought in mechanical engineering, electrical and electronic engineering and, crucially, in after-sales support, supply chain management and quality control, he says.

'Those kinds of people are really in high demand, but they cannot just come from the polytechnic [universities], they need experience,' he says.

For CLP's Ngan, finding experienced engineers to work with clean energy systems is challenging. With some clean tech systems barely a decade old, experience in operating them right down to the 'nitty gritty', as Ngan puts it, is in limited supply.

He says young engineers could take advantage of the situation and fast-track their careers by joining high-tech development firms. But he warns against specialising too early. 'From my personal experience, as an energy professional, we still need to understand energy as a whole. That means the young engineer who opts for fast-track now may [at a later time] come across difficulties to have a broader scope or view about energy.'

Hongkong Electric's Yee agrees. 'For young students, some good understanding of traditional power engineering is essential as the subject still requires students to have a very sound mathematical knowledge in mastering the fundamental engineering principles that were developed centuries ago.'

According to Ngan, there is no substitute for solid career grounding at a public or private utility, or with the regulator or government.

Meanwhile, Vepsalainen recommends a period of hard labour in the field. 'If I were a young engineer, I would take a job in China, learn for two or three years and then come back to Hong Kong as a team leader or for a management position,' he says.

But fresh graduates expecting a comfortable start to their careers may find clean tech is anything but clean. Renewable energy projects in China, for example, are not known for their hospitable locations. 'It's not eating ice cream at the Sheraton,' says Vepsalainen. 'It's long hours, it's cold, it's hot, the team goes there for weeks and weeks, they stay together in camps or barracks.'

But he sees excellent prospects - and high pay - for those who stay the distance. China itself is already exporting wind engineering and operations experience to Africa. 'That's when it becomes very interesting,' he says. 'It's a good career, a nice industry, it is definitely for the long term.'

For engineers worried about the sustainability of sustainability itself, Vepsalainen says it is a career for life. 'If you are in wind power you can easily go into electric cars,' he says. 'The whole industry is like a family.'