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While BYD’s Solar Power International exhibit-hall booth might have been modest in size and the company’s reputation may not be as well-established as its Chinese PV industry counterparts, there are few enterprises that can match the scope of its vertically integrated and potentially synergistic business platform in the renewable and cleantech space. Building around what it calls “three green dreams”—solar power, energy storage, and electric vehicles (with some solid state lighting thrown in for good measure)—the Shenzhen-based, Berkshire Hathaway-backed, $7 billion company just opened its new North American HQ near downtown Los Angeles and signed a deal to provide EV shuttle buses and cars to rental giant Hertz.
At SPI though, the emphasis was on BYD’s solar division, a group that has quietly built up more than a gigawatt in crystalline-silicon wafer and cell production capacity and 800MW of module manufacturing capability since 2008.
Like many other c-Si cellmakers, BYD is working diligently on a selective emitter solution, in an effort to drive efficiencies higher without adding cost. The acronym for its own SE technology flavor is NES, which stands for “narrow finger and busbar electroplated selective emitter,” according to the company’s solar unit general manager, Tom Zhao.
The former Motorola man said during BYD’s press conference that median efficiencies on 156mm polycrystalline production cells had reached 17.4%, close to the midway point on a tight distribution curve between 16.9% and 18%. By next year, the roadmap calls for the average numbers to reach 17.6% and 18% in Q2 and Q4, respectively.
A check of the product specs on the firm’s Series-3BB modules, which incorporate the NES cells, shows top panel efficiencies of 15.6% on the P6-30 255Wp models and 15.46% on the higher-rated, P6-36 300Wp devices.
Zhao noted that the aforementioned “narrow finger and busbar” reduce shading area on surface of the cell, allowing more active area and absorption of incident light and thus increased current. Stating that the finger width on a standard cell would be in the 70-110µm range, the NES process shrinks that down to 40-80µm while also reducing the distance between the fingers. The normally 1.8-2.0mm-wide busbar gets trimmed down to 1.0-1.5mm via the enhanced processing procedures.
He described how the locally deep phosphorus doping level under the fingers and busbar facilitates lower Rs, and shallow phosphorus doping levels in the active emitter area produces lower surface recombination and higher IQE. There’s also better short wavelength response in the cells (in the 300-400nm blue range of the spectrum).
The key process in the NES process, electroplating, reduces series resistance and improves finger conductivity. Unlike the Suntech EP approach, which uses copper, BYD’s employs silver as the plating metal. When I asked Zhao after the press conference if there was any thought to transitioning to a less expensive, more abundant element than silver, he said there were no plans to do so, noting the potential risk of peel-off with copper and general robustness of the material of choice.
He also pointed out another difference between the Suntech and BYD process schemes: his company uses a high-precision silk-screening step rather than the laser etch employed by the Wuxi firm, followed by a coating step to add the seed layer to the cell, which is then fired, resulting in a “conjunction” that is very strong. This produces “good narrowness” and shows fewer issues with shunting, the GM said.
Zhao said the production operations were highly automated, putting the percentage level at 90% for the module manufacturing lines. Among the process and quality control measures in place, he cited pervasive optical and inline inspection steps and microcrack control resulting in <2-3% damage in production and “zero cracks seen by customers.” Electroluminescence tests are done in three locations on the module lines: postsolder, postlamination, and preflash test.
Although the wafer and cell capacity—including some newly added lines—exceeds a gigawatt and the moduling nameplate is close behind at 800MW, global module oversupply and the resulting demand hit have reached BYD’s factory floors as well. Current run rates (mostly poly c-Si-based) are in the 40-50% range, he said, with efforts “to secure more demand” ongoing in China and elsewhere. A countervailing cost reduction point in BYD’s favor: no long-term polysilicon contracts, allowing the company to benefit from record low spot-market prices.
One customer adding to the order books was announced at the SPI press event. Samba Energy, a US project development company, will soon deploy 1.2MW of BYD modules and inverters on school and commercial rooftops in the Northeast and Pacific regions, with another 10MW of product in the pipeline for Q1 2012 and more on the way in the future.
Zhao also briefly described an intriguing plan that BYD is working on with a Chinese utility, a hybrid power plant that would incorporate solar and possibly wind power generation coupled with large-scale energy storage, something he said would help make the output from the system “more predictable.”
Given BYD’s broad green product portfolio, such a project seems tailor-made for the company with the initials standing for “build your dreams.”
