For high-current environments, German
manufacturer Wima provides a comprehensive
range of double-layer, cylindrical
components with operating-current
ratings up to 400 A and pulse-current
withstanding capabilities to 1400 A. The
SuperCap C and R lines consist of 2.7-V
dc capacitors in values from 110 to 600 F
with operating and pulse current ratings up
to 100 and 800 A, respectively.
The largest and most muscular, Wima’s
SuperCap MC specifies an operating
voltage and current of 14 V dc and 400
A, respectively. Weighing 1.7 kg and measuring
325 by 60 mm, 90 mm in height,
and 265 mm between poles (±), the component
can withstand pulse currents up
to 1.4 kA.
Other specifications include a
capacitance of 110 F with a ±20%
tolerance, internal resistance of
7 m, maximum stored energy
of 10 kJ, an operating temperature
from –30°C to 65°C, and
an operating lifespan of 90,000
hours.
SUPERCAP FUTURE
As noted earlier, the big push for ultracapacitors
is to replace rechargeable
batteries in a range of applications. This
is a logical progression, particularly with the current interest in green technologies
and the quest for cost-effective alternative
power sources.
One of several initiatives under way
entails the recent partnering of supercap
maker CAP-XX and Perpetuum, noted
for its energy-harvesting solutions, to create
battery-free, wireless-sensor condition
monitoring systems. A case study presented
at the nanoPower forum back in
June describes how Perpetuum’s PMG17
vibration energy-harvesting microgenerator
paired with a CAP-XX supercapacitor
will enable the design of battery-free condition
monitoring systems. These systems
collect and display data on machinery for
improving asset management.
According to the companies, traditional
condition monitoring systems require
manual data collection or the use of battery-
powered wireless sensors. Allegedly,
batteries may survive only two to five years
in the harsh environments associated with
these systems. It stands to reason that in a
plant with possibly thousands of batterypowered
wireless sensor nodes, the cost of
replacing and disposing of batteries can
add up fast.
In operation, the PMG17 converts unused
mechanical vibration into electrical energy,
providing a steady power source between
0.5 and 50 mW. The CAP-XX supercapacitor
stores this harvested energy and then
delivers the peak power needed to transmit
sensor condition data over wireless networks
such as IEEE 802.15.4 and 802.11.
The PMG17 can provide the necessary
power for intermittent radio sensor systems
such as Wireless HART, SP-100, and
Wi-Fi. However, its output impedance is
too high to supply the 10 to 100 s of mW
required by the sensor nodes. Resolving
this, the high capacitance and low ESR of
the supercapacitor provide approximately
1 s of peak power to transmit data.
“The micro-generator and supercapacitor
combo eliminates battery reliability
issues and time-consuming maintenance
while enabling significant savings in operational
costs and energy use,” says Stephen
Roberts, Perpetuum’s technical manager.
“Wireless system manufacturers can now
easily design battery-free systems using
this fit-and-forget self-generating power
source,” adds Pierre Mars, vice president of
applications engineering at CAP-XX.
For details on the PMG17, see “Energy
Harvester Perpetually Powers Wireless
Sensors,” by Pierre Mars of CAP-XX at www.electronicdesign.com, Drill Deeper 20033. Additionally, visit www.perpetuum.co.uk/resource/PMG17%20-%20Technical%20Specification%20Rev%202%200.pdf. For more information on CAP-XX supercapacitors,
visit www.cap-xx.com/products/products.htm.