How much Cd is used in CdTe modules per kW of power produced
Source: NREL, USA
Cd per kW: 70 g/kW
Cd per MW: 70 kg/MW
Cd per GW: 70 metric tons (MT)/GW
A CdTe module of 10% sunlight-to-electricity conversion efficiency produces about 100 W of output under standard sunlight conditions; therefore, the average is 7 g/100 W = 70 g per kW of electric power produced.
How much Cd is used in a CdTe module per kWh of electricity produced (in an average U.S. solar location)
Source: NREL, USA
Cd in a module per kWh: 0.001 g/kWh
Cd per MWh: 1 g/MWh
Cd per GWh: 1 kg/GWh
In an average solar location in the United States, such as Kansas, a one-square-meter, 10%-efficient CdTe module containing 7 g of Cd produces about 5,400 kWh over its expected service life of 30 years. That amounts to about 770 kWh per gram of Cd, or 0.001 g/kWh. (Note: this amount is contained in the module and is NOT an emission. The Cd can be completely recycled.)
How much Cd is contained in nickel cadmium (NiCd) batteries, and how does this compare with the amount of Cd contained in PV modules
Source: NREL, USA
CdTe modules occupying 1 m2 (10.7 ft2) contain less Cd than one size-C NiCd flashlight battery.
Size AA: 3.3 g in the form of metal Cd and Cd (OH)2
Size C: 10.5 g
Size D: 21 g
References
Horn, G. (April 1988). "Recycling of NiCd batteries: some practical aspects." Nickel-Cadmium Battery Update Seminar, pp. 56-58, Paris, published by the Cadmium Association, London, UK.
Steatite Group, The. "A comprehensive range of industry-proven NiCd batteries." Accessed January 6, 2003.
How much cadmium is needed for large-scale CdTe PV
Source: NREL, USA
Less than 3% of the current U.S. Cd consumption is needed for large-scale (i.e., GW/year) production of CdTe PV; using less than one-third of the current Cd consumption for PV would change our electricity infrastructure in only a few years. Currently, Cd is used primarily in NiCd rechargeable batteries (~65%), paint pigments (~17%), plastic stabilizers (~10%), metal plating (~5%), and metal solders (~2%) (Fig. 1). In 1997, the total Cd use in the United States was 2,600 tons; globally the total use is 19,000 to 20,000 tons.
But to change the world's energy infrastructure with CdTe PV, much less Cd than is already used for other purposes would be needed, and it might not impact the overall smelting of Cd at all! In fact, it would provide a beneficial use of Cd that could otherwise be cemented or end up in a waste dump.
Why? Using only 3% of the U.S. consumption of cadmium in the manufacture of CdTe solar cells (i.e., 78 tons) would generate more than 1 GW of new PV per year. Note that the total current PV capacity in the United States is only 0.3 GW and is projected to grow (under optimistic assumptions) to about 3.2 GW/yr by the year 2020. Even if we envision an order of magnitude higher PV production, this would require only about one-third of the current U.S. Cd consumption. The result would be new solar energy of 10 GW/year, which would quickly accumulate and significantly change the mix of electricity sources in the United States and abroad, preventing carbon dioxide and other emissions.
References
Anderson, B. A. (2000). Materials availability for large-scale thin film photovoltaics. Progress in Photovoltaics, 8, pp. 61-76.
Cadmium Market Update Analysis and Outlook. (1995). Roskill Information Services Ltd., London, UK.
How much cadmium (Cd) is encapsulated in cadmium telluride (CdTe) modules
Source: NREL, USA
CdTe modules encapsulate about 7 g/m2 (the range is from 3 to 10 g/m2) of Cd, mainly in the form of CdTe. The amount of Cd compounds in PV modules is proportional to the area of the module and the thickness of the CdTe and CdS layers. A one-square-meter area of CdTe one micron thick contains about 2.9 g of Cd. The same area of CdS contains about 3.7 g of Cd. Most CdTe layers are about 1-3 microns thick, and most CdS layers are about 0.2 microns thick. This means that the CdTe layer contains from 3 to 9 g/m2 Cd, and CdS contains less than 1 g/m2. It is expected that layer thickness will be reduced as research and development efforts continue, further reducing the amount of Cd compounds in the cells.
References
Anderson, B. A. (2000). "Materials availability for large-scale thin film photovoltaics." Progress in Photovoltaics, 8, pp. 61-76.
Zweibel, K. (1997). "Reducing ES&H impacts from thin film PV." Environmental Aspects of PV Power Systems, Utrecht University, The Netherlands.
Zweibel, K. (1999). "Issues in thin film PV manufacturing cost reduction." Solar Energy Materials and Solar Cells, 59, pp. 1-18.
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