Solar goes Boom Boom Boom

Solar goes Boom Boom Boom
Good for business, Good for the Planet

By Lubab Sheet and Eddy Blokken, SEMI

The dream of the world’s second largest solar cell maker is to make solar power a cost competitive energy source. “If we don’t, we’ve failed”, said Anton Milner, CEO and co-founder of Q-Cells. Both on-grid and off-grid applications are to be considered, as there are 1.6 billion people in the world without access to the grid, and this number will grow to 2.4 billion in the next several years. Success in photovoltaic (PV) will help alleviate some of the world’s greatest social problems and depends on innovations in managing growth, capital productivity, and new technologies. So, helping solve the PV challenge is not only good for humanity and the planet, but good for business, and that is what has everyone from government officials and venture capitals to company executives excited about solar.

Photovoltaic-based solar cells convert sunlight directly into electricity. They are made of semiconductor materials, including silicon, similar to those used in computer chips. When sunlight is absorbed by these materials, the solar energy knocks electrons loose from their atoms, allowing the electrons to flow through the material to produce electricity. The process of converting light to electricity is called the photovoltaic effect.

Despite supply side constraints associated with silicon for the past few years, the PV market has been doubling every two years, albeit from a small base. “This industry has the potential to go from boom to boom to boom if we do things right,” said Milner. Demand forecasts for PV vary from 7 to12 gigawatt (GW) by 2010 up from 2.3–2.5 GW produced in 2006.

More radical innovation needed to reduce costs

Current PV technology is based primarily on “borrowed technology,” and has seen “incremental innovation.” Many of the same issues facing the PV industry are the same as 20 years ago in the semiconductor industry. Future improvements and cost reductions will require more radical innovations, particularly in manufacturing and equipment. Areas of priorities include:

    1. Scaling of production
    2. Design for manufacturing
    3. Operational efficiency
    4. Reduced lead-times
    5. Automation in modules
    6. Standardization on interfaces
    7. Safety and environment
    8. Intellectual property management

Several solar cell makers suggested a 40–50 percent cost reduction over the next three years is a key requirement. Investments are expected to simultaneously increase as today there are approximately nine fundamental process steps—this is expected to double in the future. A number of targets were outlined and quantified.

Solar Cell Manufacturing Trends

2006/2007

2010

Lead times for manufacturing equipment

9–12 months

6 months

Ramp-up time for new production line

3–6 months

1 month

Uptime

80–85%

95–97%

Yield

90–95%

>98%

Cell efficiency
- Mono-crystalline
- Multi-crystalline


16.5–17.5%
15–16%


>19%
>17%

Wafer thickness

180–240 μm
(was 350 μm)

100–170 μm

Investment

0.4–0.6Meuro per MWp/a

<0.2Meuro per MWp/a

Labor for automated lines

1–2 employees per MWp/a

0.5 employees per MWp/a

Source: Various presentations, SEMI 1st PV Fab Managers Forum, March 2007

Numerous opportunities for equipment manufacturers to add-value

Dr. Rudiger Schultz, technical director of ErSol Solar Energy, provided an equipment supplier assessment, with appropriate disclaimers. In addition to improved lead-times and ramp-up times for equipment, cell manufacturers characterize the current equipment relationship as “selling rather than consulting,” with a desire for more focus on customer needs and improved service support. A number of opportunities for improvement were highlighted for equipment suppliers serving the PV industry:

  • Software capabilities (computer integrated manufacturing, remote access, GEM/SECS, XML)
  • Service (hotline, quick response, local service point, spare parts availability)
  • Development capabilities (continuous improvement process, consulting, not just selling)
  • Low operation costs (throughput increase and footprint reduction)
  • ISO-certification
  • Documentation (handbook in native language, graphical user interface in native language, appropriate hook up information, spare part lists)
  • Proactive training (for engineers, technicians and operators, training centers)

Future Solar Cell Fab—In-line

The future PV fab will require true in-line processing. In-line refers to true automation with “no human handling” or interruptions of the flow (i.e. batch-loading and unloading). Today most lines involve mechanical tool connections not real in-line processing. One of the key disadvantages to true in-line manufacturing is lack of flexibility to upgrade a tool/process. Also, if one tool on the line goes down, the entire line goes down and so generally several lines run in a single factory, making the footprint of factories very large. In order to establish true in-line PV manufacturing, smart automation, computer integrated manufacturing or CIM (including process instructions to operator, recipe selection, recipe download), manufacturing execution systems (MES), maintenance schedules, logistics and sophisticated work in process (WIP) flow are required.

Don’t forget the impact on module assembly

The supply constraints and associated price increases with silicon have caused a significant effort to reduce cell wafer thickness, although currently there are technical limitations at the module level at 160 μm. Thinner solar cells may save costs at the cell level, but increase costs of module fabrication. Another issue is that any change in raw materials or product technology requires an update of the product certificate or warranty which can take 6 to 12 months. “Sometimes certification takes longer than the lifecycle of the product,” said Lars Podlowski, CTO of SOLON. As a result, once silicon supply constraints are alleviated and pricing levels normalize, the emphasis on reducing wafer thickness might slow.

Despite the challenges associated with re-certification, innovation is needed in module manufacturing, particularly in “stringing” or putting the cells together and interconnection. The migration from manual stringing to automated stringing has begun, but is highly customized. Soft soldering by laser or induction has just recently been developed in back contacts or solar cell interconnection and is gentler than current infrared or hot air techniques, but requires higher investments and more skilled operators. Electrically conductive adhesives also offer less breakage for increasingly thinner wafers, but are expensive, have long curing times and questionable reliability.

Improved communication needed

A semiconductor equipment manufacturer may see the requirements and challenges outlined above and feel that these are easy problems that have already been solved for the semiconductor industry. While there is no doubt that the expertise and technology developed for semiconductor manufacturing can be leveraged in PV, there are also several unique needs for PV makers, and equipment companies would be well advised to spend some time listening and talking to PV makers to make sure these are understood. For example, some cell makers are thinking about implementing RFID tagging of cells and modules in the coming years—a much different approach than laser marking of wafers. Likewise, there needs to be a change of philosophy for cell makers too; if perfect manufacturing is needed, cell makers need to be willing to pay more for tools, and look at the total cost-of-ownership rather than just the tool costs. In addition, equipment companies need samples of some of the advanced wafers or cells “to play with” and improve equipment. Driving down costs in PV is going to boil down to open lines of communication between equipment suppliers, materials suppliers and cell/module makers, building strong supplier-customer relations and making sure everyone in the supply chain wins. Attitudes have to change a little on both sides, but based on the discussions that are already taking place, the future looks bright.

Readers may also be interested in the following article:

PV Standardization: an Opportunity for Real Win-Win Collaboration.

All of the information contained in this article was derived from presentations made at the 1st Annual SEMI PV Fab Managers Forum, hosted by Q-Cells, March 2007 in Leipzig, Germany. SEMI is poised to help advance the growth of the PV industry. For more information on SEMI PV activities, please contact at Eblokken@semi.org in Europe, Lsheet@semi.org in North America, Tono@semi.org in Japan or Dliu@semi.org in China.