Renewable energy applications present opportunities and set design challenges for capacitors
BY BILL BUCHANAN
Kemet, Greenville, SC
http://www.kemet.com
The renewable-energy sector of the electronics market is only just beginning to realize its great potential in the industry. This presents a great market opportunity for designers and manufacturers of passive components — capacitors in particular — to test their technical capabilities.
When compared to other major ares of application for capacitors, such as the automotive and consumer markets, renewable energy is not quite as exposed to the ebb and flow of the global economy. Manufacturers are only too aware of the impact that the current worldwide economic situation is having on the consumer’s confidence and ability to make major purchases, such as new cars and other “big ticket” consumer electronics items. Renewable energy, however, has the benefit of “green” momentum pushing it forward. The growing number of government regulations and guidelines regarding energy efficiency, as well as government funding, further reinforce this.
Requirements for efficiency
Capacitor designers and manufacturers work closely with customers in the renewable-energy sector to address specific and sometimes unique requirements. Large-scale commercial wind turbines are perhaps the highest profile renewable-energy application, but capacitor manufacturers are also supplying devices for applications such as solar inverters, wave turbines and Kinetic Energy Recovery Systems (KERS) in the automotive sector.
The types of capacitors with applications in renewable-energy systems include large electrolytic and power film devices. These devices are used for filtering, decoupling dc-link for inverters, and snubbers for IGBT protection. High-voltage ceramic parts and film capacitors are also appropriate for use at the “front end” of renewable-energy systems. It is also necessary for the control circuitry in all equipment to have the latest technology in both ceramic and tantalum.
The reliability and life expectancy of components used in renewable-enery systems must be extremely good — above and beyond the specifications for off-the-shelf devices. Most of the renewable-energy systems have stringent requirements for the electrical and electronic specifications for capacitors and other components used in their circuitry. Equipment such as wind and wave turbines are often situated in remote locations that are not easily accessible and a need to operate continually. The components must also be able to withstand extreme operating conditions.
Regulating energy loss
Renewable-energy systems require that losses between the raw energy produced and the energy delivered to the user are kept to a minimum. Therefore, capacitors that have high efficiency, low equivalent series resistance (ESR), and low equivalent series inductance (ESL) are essential. Individual devices also need to offer stable capacitance and dissipation when subjected to widely varying frequencies, ambient operating temperatures and humidities that are typical in these applications.
The unique challenges presented by renewable-energy applications for components incorporated in their design, including capacitors, means that these solutions must be tailored to those specific needs. In the case of electrolytic capacitors, this includes life calculations based on exacting customer specifications. This allows maximum life to be achieved, which is crucial when accessibility is difficult and maintenance costs are prohibitively high. Similarly customized power film capacitors can be offered that give long life for higher voltage dc-link as well as meeting tougher voltage and operating temperature range requirements. ■
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