An alternative with power

Capacitors vs. rechargeable batteries: the right area of application is crucial

Electrochemical supercaps, also known as ultracapacitors,
are a further development of the double-layer capacitors commonly used in electronics. Their field of application ranges from the smallest current units for storing data in static memories (SRAM) of electronic devices to power electronics. For example, supercaps are used to store energy in the KERS system of Formula 1 racing cars or support the regenerative braking of buses and trains.

It is crucial to select the right area of application:

Using supercaps for bridging times of several minutes, for example, is uninteresting, as a lead-acid battery is 5 to 10 times cheaper for this purpose. However, with around one million charging cycles, they can be recharged practically an unlimited number of times. They also deliver high currents in a very short time due to their exceptionally low internal resistance. This makes them the better choice than any battery technology for cyclically used applications that require extreme performance in the range of a few seconds.

Compared to accumulators of the same weight, supercapacitors have only about 10 % of the energy density, but their power density is 10 to 100 times greater. They can therefore:

• can be loaded and unloaded much faster
• withstand significantly more charging and discharging cycles
• Supplement or even replace batteries if a large number of cycles are required.

Peak shaving use case: cutting-edge technology for efficient energy management

The energy management of industrial companies aims to never exceed the agreed maximum electricity consumption - not even for a very short time - as this dramatically increases the supply fee. At the same time, electricity consumption can only be adjusted to a limited extent, especially not quickly. One solution is to use supercaps in conjunction with an uninterruptible power supply (UPS). In this case, the UPS takes over the supply of the load if the energy requirement rises above the permitted maximum. Such systems are already in use today, but generally use batteries with limited charging cycles, meaning that the system cannot work effectively or the user has to reckon with high battery wear. With supercaps, this limitation no longer plays a role. Furthermore, their service life is significantly longer: even at an ambient temperature of 40 degrees Celsius, it is still in the region of 8 to 10 years, whereas a standard lead-acid battery could only have a quarter of its regular service life at this temperature.

A lot of electricity in very little time: safe production with supercaps

The specific advantages of supercaps are ideal for an uninterruptible power supply in an industrial environment, as this places special demands on a UPS. As CNC machining centers require too much power to continue operating during a prolonged outage, the main aim is to achieve an orderly shutdown of the production plant. Three steps are crucial for this:

1. To be able to remove the tool directly from the workpiece to prevent expensive damage to it.
2. Save all position data and then initiate a controlled shutdown.
3. Seamlessly resume production after the power returns.

Supercaps Big 5: the advantages at a glance:

1. Due to their low internal resistance, supercaps deliver extremely high power. A corresponding UPS designed for peak shaving from Wöhrle Stromversorgungssysteme, for example, can deliver up to 2.4 MW (approx. 4 kA) for one second.
2. Significantly longer bridging times can be realized with lower output power.
3. Supercaps in block design allow for quick and easy integration into standard products. This results in cost-effective products such as the Supercaps UPS from Wöhrle Stromversorgungssysteme, which can also be used in demanding environments.
4. Because supercaps, unlike lead batteries, do not outgas, the housing does not require air exchange. They can be installed in a completely encapsulated rack with which protection classes of IP67 can be achieved.
5. Supercaps are insensitive to deep discharge, which usually causes irreparable damage to lead batteries. They can be completely discharged, shipped and installed. This makes transportation and handling much safer and less complicated.

Redundant supply thanks to modular approach: higher availability, lower costs

UPSs in the industrial sector must be installed close to the consumer and are therefore exposed to the harsh environmental conditions of the production hall. Robust energy storage devices such as supercaps help to keep the costs of the housing low and ensure the availability of the UPS. Here too, the power output is extremely high for a few seconds up to two minutes, which supercaps can cope with much better than battery technologies.

The Supercap UPS from Wöhrle Stromversorgungssysteme uses four power modules, each with a capacity of 25 kW, which can supply a redundant 75 kW payload in an n+1 configuration. The UPS is installed in a dust and splash-proof Rittal enclosure and uses eight Supercap blocks from Skeleton Technologies connected in series. These blocks each have a capacity of 177 farads (216 kW) and deliver a peak current of 2.6 kA for one second at a nominal voltage of 51 volts. As a result, the UPS can supply standard industrial loads with 400 V. If longer bridging times or higher currents are required, additional storage units can be accommodated in an external cabinet. It is important to take cell management into account and implement it in the operating concept. For this purpose, each supercap block has a CAN bus communication connection that allows access for charge management.

Supercaps: An alternative that sets new standards

Supercaps have reached a level of maturity that allows for very demanding application scenarios. With their specific advantages in terms of cycle stability and current output, they are far superior to battery technologies and - based on correct planning of the application - achieve significantly better performance than lead-acid or Li-ion batteries. It is crucial that the products are optimally matched to the individual capabilities of the supercaps and that the power section of the overall system can withstand extreme currents. Regardless of the energy storage system used, redundancy and availability must be guaranteed through appropriate measures such as modularity. If this is ensured, supercaps are a real alternative to conventional energy storage systems, especially in an industrial environment.