The worker, standing inside a section of what will eventually be a wind turbine, looks up as a piece of equipment on a rope is gently lowered inside through a hole.
Wearing an orange helmet, a grey T-shirt and once-white gloves that have long since turned grey, he manoeuvres the machinery as a colleague outside reaches in to help.
He works frantically inside the huge circular frameto which vast blades will be attached.
Outside this warehouse-style factory building in Baoding, a city a couple of hours south-west of Beijing that is home to 170 green-technology companies, are the 40-metre-long wind turbine blades. They appear elegantly sculpted as they lie side by side in countless rows.
Nearby, protected from the elements by cloth coverings, are scores of nacelles, the frameworks that contain all the power-generating parts of the turbine.
It is perhaps no wonder that this facility, belonging to the state-owned Guodian United Power Technology, is churning out wind turbines by the dozen.The market for them in China is booming.
Last year, the country installed almost 19 gigawatts of new wind energy capacity, taking its total to 45 gigawatts, the largest in the world.
Companies such as Guodian, which supplies all the components except the huge towers on which the turbines sit, have boosted production to capitalise on the vast investment in the sector.
Guodian produced 100 turbines in 2008, 600 in 2009 and 850 last year, all for domestic use. This year, thanks to the opening of new facilities, the company's annual production capacity will increase to 2,000 turbines, says Wang Hongbin, the company's deputy general manager.
Overall, the global market in wind turbines ispredicted to be worth US$94.7 billion (Dh347.84bn) this year, according to analysts at BTM Consult, which researches renewable energy. Last year, just over half of new installations worldwide were in China - 19.4 gigawatts out of 39.4 gigawatts.
Mr Wang points out that Guodian will "definitely" increase production even further.
"But it's hard to say what the number is. It depends on the incentives from the government," he says. "The government wants to control the growth speed of the industry. Lots of new facilities have opened in the last few years and the government needs to control the growth."
The world's second-largest economy, biggest greenhouse-gas emitter and largest electricity consumer wants at least 15 per cent of its electricity to come from renewable sources by 2020, and officials say the target could rise to 20 per cent.
While there have been concerns from foreign companies about incentives offered to domestic companies in China, even Chinese-owned producers could feel the effects of a slight slowdown in installations forecast for the next two years. The China Wind Energy Association predicts a total of about 30 gigawatts of new wind power generation capacity will be installed this year and next as China works towards a 2020 target of at least 150 gigawatts.
Part of the reason behind an expected slight braking of development in wind power is that the country's grid system is not set up to deal with vast quantities of electricity being produced by wind turbines.
Late last year, on releasing a wind energy report, the environmental group Greenpeace said China's national grid required a "massive overhaul".
Many turbines are in sparsely populated areas, and the challenge of transmitting their electricity to major urban areas has yet to be fully overcome.
In this context it is perhaps hardly surprising, Mr Wang acknowledges, that there is a risk of oversupply, with companies forced to reduce costs, improve quality and offer better after-sales service to secure business. While China's wind power manufacturers face turbulence as the market slows a little, producers of solar power are looking at even tougher times ahead, although here the concerns stem from the overseas market.
Yingli Solar, one of China's largest producers of solar power panels and one of Baoding's first green-technology companies, proudly shows off some if its latest solar-powered innovations to visitors at its headquarters in the city. There are forest fire alarms that combine solar panels with smoke detectors and emergency rescue kits powered by the sun.
But it is solar panels for generating electricity that drive the company's balance sheet, and there is unquestionably excess production capacity, even though China itself wants to increase installed solar electricity capacity more than a hundredfold by 2020 to 50 gigawatts. The issue is a steep drop in demand from overseas, where 90 per cent of Yingli's output goes.
Global investment in the solar power industry was valued at $81.5bn last year, and Chinese manufacturers held a 62 per cent market share, although in terms of the number of panels installed, Germany was the market leader. China's annual manufacturing capacity for solar power modules is 17.6 gigawatts, and Bloomberg New Energy Finance predicts 9.5 gigawatts of production capacity will be added this year. The organisation has said that this year, the global capacity to produce photovoltaic cells will be twice the demand for the technology. The continued investment in production facilities comes as governments in two of the world's biggest markets, Germany and Italy, have cut back on subsidies for solar power. France and Spain have also reduced subsidies.
With the prices of solar cells and panels falling, the market value of the companies making them has also tumbled this year. Yet Yingli insists there is cause for optimism.
"There's an oversupply globally. The demand is stimulated by the incentives from the government, so the demand in China is increasing, but the demand in Europe is declining," says Hank Wang, Yingli's director of international sales.
"It's a crisis, but to some companies such as us, it's an opportunity because it will force a lot of companies out of the PV [photovoltaic] industry and [those that] remain will be better," he says.
Yingli has said lower prices could stimulate further use of solar energy, a sector the Chinese government has particularly earmarked for growth after the crisis at Japan's Fukushima Daiichi nuclear plant.The Japanese emergency has led China to say it will curtail its ambitions for nuclear power.