Hybrid storage systems

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Under hybrid storage systems is defined as a combination of different energy storage methods with the aim of their strengths to connect. Since many storage systems are optimized for either energy or performance , it is desirable to combine both properties. For example, an electric vehicle requires a lot of energy (= greater range) and high performance (= better acceleration).

Properties of electrochemical and electrostatic storage

With electrochemical storage devices ( accumulators ) only a small number of cycles (approx. 500–1500), but a high energy density and low self-discharge is possible. In contrast, electrostatic storage devices ( capacitors ) enable high numbers of cycles (<10,000) and high outputs. However, the energy density is lower and the self-discharge is high. The aim is to combine the advantages of both technologies. This is possible either through an integrated combination or through external coupling via terminals or contacts.

Lead DSK hybrids

This is a combination of a lead-acid battery and a double-layer capacitor (DSK). The advantages are a four times higher number of cycles than with the lead battery, a lower price than z. B. Nickel-metal hydride accumulators , a charge four times faster than with a conventional lead accumulator, no safety problems, a high temperature range (starting at −50 ° C) and easy recycling .

The CSIRO company uses a negative electrode consisting of 50% lead and 50% activated carbon . The energy density is a little worse here than with the lead accumulator and the power density is a little worse than with the DSK. This procedure is currently being tested in the Honda Insight Hybrid over 160,000 km of mileage. A production is currently being set up.

However, problems can arise, especially in Europe, as lead can no longer be used. The only exception: the starter battery of a motor vehicle .

Lithium DSK hybrids

This technology is currently being researched. Product maturity is expected in a few years at the earliest. The idea is to produce highly porous DSK electrode materials with the largest possible surface area, which are then coated with a thin (approx. 100 nm thick) electrochemically active layer. The preferred collector material is nanostructured metal (e.g. nickel ) and the active oxide, e.g. B. Manganese dioxide (MnO 2 ) or lithium manganate (LiMn 2 O 4 ).

External coupling

Coupling is best possible using a power electronic actuator. If only one actuator is used, the first storage system is placed on the left of the actuator and the second storage system on the right of the actuator. For example, if you take a conventional battery on the left and a double-layer capacitor on the right and switch on the consumer on the right, the DC / DC converter only has to be designed for a small capacity of the battery, but the machine converter has to be dimensioned very large because the voltage break in at the DSK and thus the amperage can rise sharply. If the consumer is switched to the battery side, the DC / DC converter and the machine converter must be dimensioned exactly opposite. One solution is to use a second actuator, which is unfavorable in many areas because of the additional weight. However, the actuator on the battery can be designed for low power and high energies and the actuator on the DSK can be designed exactly the other way around.

use

Hybrid storage systems are already being used in cell phones and electric vehicles. Modern cell phones often need high performance for GPRS , music playback or the flash for a photo , which the battery cannot provide immediately. This is smoothed out by a DSK.

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