by Xavier Alcaraz, principal consultant, and Andy McIntyre, executive VP/managing principal/cofounder, EORM
July 31, 2009 -- Photovoltaic (PV) technologies have experienced significant improvements in efficiency and greater consumer demand, resulting in many more product alternatives and applications than ever before. Newer alternatives to standard crystalline silicon modules have emerged including casting wafers instead of sawing, thin film (CdTe, CIGS, amorphous Si, and microcrystalline Si), concentrator modules, Sliver cells and continuous printing processes. These advances in PV technologies have introduced a range of new manufacturing and R&D chemical and physical hazards that require appropriate engineering, administrative and personal protective equipment controls to minimize the potential for employee illness and/or injuries.
Summary of chemical hazards
PV manufacturing and R&D process present a diverse range of chemical-related health and safety considerations during both production and maintenance operations:
- Pyrophoric, flammable and/or toxic gases such as silane, phosphine, hydrazine, hydrogen, ammonia, and arsine, which are utilized in reactors to facilitate deposition processes, doping, and for other production-related processes. Worker exposures and chemical safety hazards associated with storage, handling, and transport of these gasses are ever present. Due to the hazardous nature of these chemicals and the potential catastrophic consequences associated with their release or exposure, a detailed process hazard analysis (PHA) should be incorporated into the process design phase. In the US, the type(s) and volume(s) of these chemicals stored at a facility may trigger required compliance with the Occupational Safety and Health Administration's (OSHA) Process Safety Management standard and/or the Environmental Protection Agency (USEPA) Federal Accidental Release Prevention (FedARP) Program.
- Mixtures of airborne metal dust, generated from cutting and scribing of solar cells with deposited metals (e.g., arsenic, cadmium, copper, indium, gallium, and selenium), may result in worker inhalation exposure. If cutting and scribing operations are not properly controlled through process enclosure and/or ventilation, airborne emissions of metal dusts have the potential to settle onto equipment, work surfaces and floors creating a potential cross-contamination issue as well as an ingestion hazard to workers. Appropriate assessment of the process and installation of enclosures and/or ventilation controls (if necessary) may be required to adequately control emissions from cutting and scribing, thereby ensuring worker exposures are below the applicable regulatory exposure limits.
- Nanoparticles used in PV manufacturing such as quantum dots suspended in ink, nanowires, and silver cells are made of various chemicals such as cadmium, silicon, cadmium telluride, and cadmium selenide. Handling nanoparticles in their raw (unbound) form can result in an inhalation and/or dermal hazard. The properties of these nano-sized particles may differ significantly from the larger particles of the same material, including mobility throughout the body, bioaccumulation in select organs, and toxicological response.
- Various corrosive chemicals used to etch and clean PV components during manufacturing include hydrochloric acid, hydrofluoric acid, phosphoric acid, and sodium hydroxide. Proper ventilation controls, employee training, and use of personal protective equipment (gloves, goggles, faceshields, etc.) are necessary to avoid the potential for inhalation of vapors and/or skin contact.
- Abrasive cleaning methods are often used to manually clean reactors and other production equipment in CIS and CIGS (copper, indium, gallium, selenium) solar cell production operations, resulting in the potential for exposure to reactor chamber deposits and reactant residues. As such, exposure controls such as "snorkel" exhaust ventilation, use of HEPA-rated vacuums, and cartridge respirators are necessary to minimize worker inhalation exposures.
A broad range of chemical compounds are employed in the photovoltaic manufacturing and R&D processes, some of which have limited toxicological data available and/or no established airborne occupational exposure limits. In the absence of sufficient toxicology data and recommended occupational exposure limits, PV manufacturers should employ a robust combination of engineering controls, administrative practices and personal protective equipment to minimize the potential exposure to workers during production and related maintenance activities.
Summary of physical hazards
In addition to the chemical-related health and safety considerations, PV manufacturing and R&D also present various physical safety considerations during production and maintenance operations:
- Servicing, cleaning, adjustment, and/or repair of equipment present potential exposure to a range of hazardous energies -- electrical, hydraulic, mechanical, etc. Implementation and training on well-written hazardous energy control procedures is critical to avoid the potential for electrocution, amputation, or crushing injuries.
- Exposed belts, wheels, and other rotating equipment on conveyors or other production equipment require appropriate guarding to prevent inadvertent contact by production and maintenance employees.
- Use of hand and power tools for machining of parts, preventative maintenance, etc., must be used correctly to avoid injury.
- Manual material handling of product, equipment, etc. can result in costly sprains, strains, and other musculoskeletal injuries. Use of conveyor systems, crane and hoist devices, pallet jacks, carts/dollies, etc. serve to minimize such injuries.
- Traffic associated with forklifts, pallet jacks, and other material handling equipment can lead to impact injuries. Operator training and compliance with the Powered Industrial Trucks standards and best practices is required.
- Cluttered or spilled materials in walkways and general work areas often lead to slip and trip injuries that are otherwise easily preventable.
PV technologies have introduced new manufacturing and R&D processes that present a range of chemical and physical hazards that require careful, upfront planning using a Design for Environmental Safety & Health (DFESH) approach, institution of a robust equipment installation safety signoff process, and proactive management focus on developing and supporting a strong EHS culture to ensure appropriate control of chemical and physical hazards associated with production processes and maintenance interface. Integrating EHS into the business from design to product take-back will contribute to improved employee morale and retention, reduced accident and injury experience, and bottom-line financial contribution.
This article was originally published by Photovoltaics World.