One of the world’s largest PV power plant operators, China’s HHDC, is pushing the R&D dial so that hybrid clean energy solutions can be understood and actioned, writes Jeremy Chunn.

With abundant water resources from three rivers – including the Yellow River – and 100,000 square kilometres of unutilised land, SPIC Huanghe Hydropower Development Co (HHDC) chairman Xie Xiaoping says Qinghai Province has the potential to provide all of China’s power.

It’s a huge claim, and one Xie won’t have to deliver. Clean energy developers all over the country are pulling together in their bid to meet President Xi Jinping’s Paris Agreement commitment for China to use renewables resources to meet 30% of its energy needs by 2030.

HHDC, a subsidiary of China’s State Power Investment Corporation, started its journey into solar in 2010 with completion of a 10MW PV power plant in Tibet. “We started to build benchmark plants each year since then,” Xie says, including a 200MW PV plant in Golmud in 2011 and the 850MW Longyangxia hydro-solar power plant in 2014.

“Our company’s total installed capacity will hit 17,950MW at the end of 2019, clean energy making up 93%,” he says. “We are one of the largest PV power plant operators in the world now.”

Hybrid solutions

A priority for HHDC is understanding the possibilities of hybrid energy solutions, which explains its investment in a 100MW demonstration plant, where 148 different technologies are being tested, all monitored by 4,000 measuring devices across 32 data categories.

It’s a work in progress, Xie says, but early indications show small differences in generation in summer and large differences in winter. Regarding module technology performance, panels with N-type cells are delivering 11.68% higher output than a reference module.

Storage is also under the microscope at the demonstration base, with 20MW PV connected to 16MWh of battery technology, including LFP cells, ternary lithium cells, zinc bromine flow batteries and vanadium redox batteries – all up, 16 distributed energy storage systems and six concentrated energy storage systems.

Mounting structures are another important determinant of a project’s viability, with single-axis delivering 17.5% higher output and dual-axis a boost of 21.9%. Considering the investment required with tracking, the company’s assessment is that single-axis offers the best outcome.

A vertical orientation for bifacial modules, second from left, is among the possibilities being tested at HHDC’s demonstration plant.

One application at the site that caught EcoGeneration’s eye is the use of bifacial panels in a fixed vertical orientation, so that one side gets the sun in the morning and the other side in the afternoon. The generation profile for such a simple solution shows two bumps instead of one, and a module that stands straight up and down would be far less likely to accumulate grime or dust.

From his experience overseeing a huge portfolio of clean energy assets, Xie favours a ratio for solar and wind of about two-to-one as being “relatively optimal”.

The Qinghai Province in China’s northwest is dry, cool and high, a great combination for solar (Xining, the capital, is 2,275m above sea level). During EcoGeneration’s visit the temperature dropped to around -10˚C, but it felt far milder. Aware that a clean energy plant should leave a small footprint on the environment, HHDC has spent six years testing conditions at its Hainan PV industry park for the effects on ground wind, vegetation, land temperature and humidity. Satellite images of one site in 2012 and 2018 show a 15% increase in vegetation and a rise in humidity – good news for the local wildlife.

The evaporation in sunny weather has also been halved, with the result that desertification of land has been restrained. “On one hand, large scale solar plants facilitate the environment recovery; on the other hand, the recovered ecosystem enhances the stability and security of PV power facilities,” Xie says.

Both sides of solar

Following two years of research HHDC has launched a 72-cell bifacial module, the TOPCon. The 385W unit has a conversion rate of 19.6% and features DuPont’s new clear Tedlar film-based backsheet, to bring the weight down when compared with glass-on-glass alternatives.

Risk assessment for any good solar project combines laboratory data with field data, and DuPont PV Solutions vice-president of ecological system and business development Anthony Chen is concerned by evidence of bowing, cracking and delamination for glass-on-glass modules, where his research shows 8% of panels in some projects cracking within eight months of installation and 10-20% of modules succumbing to bowing.

The HHDC plant in Xining is being expanded as the company steps up production of its N-type IBC cell.

DuPont’s Tedlar backsheet technology, a polymer-based solution, is proving a tough contender for developers’ attention, he says.

“A double-face module, as the name implies, generates power on both sides. It requires the packaging material to be highly transparent and reliable,” he says, estimating that a 60-cell module with a clear Tedlar film-based backsheet will be 27-38% lighter than a glass-on-glass equivalent, and a 72-cell module 18-34% lighter.

“We are not just working on efficiency but also paying attention to ROI and reliability over the entire commercial life,” Chen says.

It will be another busy year for solar. Industry analyst BloombergNEF expects 121-154GW of new PV projects to be built globally in 2020, up from 109-134GW in 2019. In China, a rebound in investment is expected in 2020 as projects carry over from 2019 and a new subsidy-allocating auction happens in March. The analyst expects China to install 37-45GW in 2020, up from 26-31GW in 2019.

“Although China has made a lot of noise on subsidy-free solar plants … 2020 will be the first year to see them hitting the ground in volume,” the report said.

Powering ahead

China should also see a bumper year in the residential segment, with more than 6GW expected in 2020, up from some 4GW in 2019.

Last year it started construction on a 3GW solar plant using P-type PERC modules with single-axis tracking, which Xie says will become standard for utility-scale applications. The company turns out 625MW of panels a year and 1.1GW of solar cells, processing 2,500 tonnes of polysilicon.

“There are so many different types of cell and module technology in the PV industry,” Xie says. “We produce cells and modules not only for the products themselves, but also for a better job in our PV plants.”

Apart from manufacturing PV componentry and developing solar plants HHDC is also engaged in overseas plant investment and engineering and technological services. “Our international development capability is on a stable rise,” Xie says. “We have obtained the development rights of several clean power projects.”

Late last year the company reached an efficiency milestone when its N-type IBC cell tipped an average 23% conversion rate. HHDC has already been contracted to supply 50MW of the module to Italy’s FuturaSun, the country’s second-largest PV supplier. In Xining, work is progressing on a 200MW facility dedicated to manufacturing the IBC cell.

It’s been a rapid rise since HHDC was established in 1999. As to the next 10 years, Xie is confident the company will deliver steady growth. “Our installed capacity will hit 22GW at the end of 2020, 25GW at the end of 2025 and 30GW at the end of 2030,” he says.