Issue



Keeping PV fabs safe: the right thing to do — and economical


07/01/2009







Andreas Widl, Oerlikon Leybold Vacuum, Cologne, Germany

The photovoltaic (PV) industry is grappling with several factors that will be familiar to veterans of the semiconductor sector: the need to reduce costs (driven by the holy grail of grid parity), and growing time-to-market pressure (driven by the large number of panel suppliers seeking to establish themselves as leaders and begin earning ROI).

Much of this battle will be won or lost on the manufacturing line, and there will be intense pressure to maximize output at minimum cost. That almost always involves cutting expenses, but it should not include lowering quality or prudent operational and safety standards, such as management of dangerous substances. This is clearly the right thing to do, but also is the approach that gives solar panel producers the best opportunity to meet their goals.

To understand why, we need to first note that, when compared to the semiconductor industry, solar panel makers use large quantities of hydrogen, silane, and other explosive and/or toxic gases. Substrates for solar cells are generally orders of magnitude larger than silicon wafers, and process chambers accordingly contain much larger volumes of process gases.

Traditionally, chipmakers have added large quantities of nitrogen (as much as a 100 to 1 ratio) to gases leaving the process chamber; this dilutes the hazardous gas to the point where it is no longer dangerous. However, the far larger quantities of gas used in solar production renders this approach uneconomical.

A more cost-effective alternative is to reconsider the system design, and limit the amount of oxygen that enters the system. This makes it possible to avoid creating explosive atmospheres in the first place, which simplifies the problem encountered on the exhaust side. Controlling the oxygen in this way requires careful attention to the overall design of the vacuum system but the payback is the ability to provide the required level of safety at a significantly lower cost.

The exclusion of oxygen becomes extremely important in this proposed approach. Therefore, the design of the vacuum system must address a number of critical areas. For example, the integrity of vacuum connections must be carefully monitored, and personnel must be trained to ensure that vacuum chambers are free of leaks. Of particular importance is the need to review operating and maintenance procedures in order to remove these as accidental sources of oxygen ingress.

These approaches do require an amount of up-front planning, as well as close attention to day-to-day protocols for gas-handling and vacuum systems. But the benefits are huge — a combination of first-class safety and cost-effective operations.

An especially compelling argument is that the development of robust safety practices is a predictable investment of effort. You are able to calculate ahead of time what your commitment is, and you can have confidence in the day-to-day safety and environmental compliance of your manufacturing line.

The alternative is risk — primarily in terms of the health and safety of your team, and also in equipment downtime. When a piece of equipment is out of service, the cost can easily work out to 5,000 to 10,000 ???/hour (roughly 7,000 to 14,000 US dollars). Additionally, factory floor accidents typically require extended shutdowns for investigation and remediation — a disaster for any manufacturing line manager seeking to meet commitments.

The solar industry can point with pride to its mission of helping our planet move into a new era of renewable energy. By taking the right steps with regard to safety, we can keep our costs in line and also take pride in running our facilities efficiently. ??

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Andreas Widl, PhD, CEO, Oerlikon Leybold Vacuum GmbH, Bonner Strasse 498, 50968 Cologne, Germany; media.vacuum@oerlikon.com.