No blackouts with mobile storage solution

Paul Boughton

A new idea for how to compensate quickly and flexibly for fluctuations in the low-voltage network has emerged from Germany and Switzerland.

Two years ago, German magazine bild der wissenschaft named the energy thriller Blackout – Morgen ist es zu spät (Blackout – Tomorrow Is Too Late) the most exciting science book of the year.

The sombre dystopia conjured up by Austrian author Marc Elsberg describes the catastrophic situation in Europe after a complete power failure. In Elsberg’s best seller, the collapse of the power network is the result of a terrorist attack.

“These horror scenarios sell well because they appeal to our darkest fears. But broadly speaking, our supply networks are not yet susceptible to blackouts of this kind,” Markus Müller, market developer at international plug connector manufacturer Multi-Contact, is convinced.

The increasing number of decentralised energy generators is bringing flux to our power network. This is why Müller is thinking of a solution that would allow network fluctuations and even partial network breakdowns to be balanced out: mobile batteries connected specifically to selected network hubs to compensate for voltage peaks and troughs.

“A global blackout is something for thriller writers, while guaranteeing stability of isolated networks is very much a reality,” explains Müller. Natural disasters such as floods or earthquakes make this all the clearer.

If part of the power network is isolated from the main grid as a result of flooding, ice, or earthquake, thousands of households sometimes have to go without electricity for days on end. This is a disaster for the population and, in the worst-case scenario, can even have fatal consequences for hospital patients.

In isolated networks, the power is normally provided via a large standby power unit or a local power station as the main energy source. What they lack is the compensation capacity of a large integrated network. This means that strong fluctuations in energy feed-in from, for example, PV systems can bring an isolated network to breaking point.

However, large storage batteries would be able to divert output surges away from these networks, while also supporting the generator when a couple of clouds move in front of the sun.

Storage solution

Müller came up with the idea of a mobile storage solution when looking for a flexible solution to support the existing supply network.

He explains: “There are feed-in points up and down the country designed to allow the connection of standby power units in an emergency. At the same points, there is the option of connecting storage batteries to extract energy and feed it back into the grid.”

His proposed solution: connecting mobile storage batteries designed as HGV trailers or containers to the network hubs using flexible cables and connectors and thus quickly and flexibly stabilising the supply network. The German CleanTech Institute (DCTI) also found the idea simple and brilliant and awarded the mobile storage solution the title of Clean Energy Innovation in 2013.

According to the DCTI, the solution represents a flexible contribution to the configuration of the smart grid. With the mobile batteries, existing networks can easily be adapted to future requirements such as decentralized feed-in or changing demand due to the growth of built-up areas and desertion of rural areas. The increased demand caused by the sudden rise in electric vehicles being charged at transport hubs during holiday periods can also be covered by storage batteries.

Specific load shedding

The number of feed-in stations has increased much more rapidly than the network infrastructure allows. Depending on the energy form, the network is subject to huge fluctuations.

In summer PV systems create an excess, while in winter it is the wind power stations that bring the network toward the limits of its capacity. If renewable energies continue to be expanded, bottlenecks in the power supply will be unavoidable.

However, there are many indicators that these will occur temporarily or on a seasonal basis. The maximum feed-in performance and the minimum consumption, which is set off against it, are the decisive factors in the design of the future grid size. However, the question needs to be posed as to what extent the temporary inclusion of large batteries provides a better solution than general expansion. They are already providing energy on demand on a specific, temporary basis and taking the strain off the network. The storage batteries can work well to capacity and are quick to pay off because they are so mobile. Using the connections already installed at many network hubs, the concept is simple, quick, and safe to implement.

Standby power units are connected to the feed-in points using flexible cables with suitably large cross sections that are fitted with plug connectors. The preferred plug connectors used at the feed-in points are from the BV range from Multi-Contact. The connecting cables for the planned storage batteries will be fitted with BV plug connectors to make them very easy to fit.

The technicians love the excellent contacts and the easy handling of the BV connectors. The largest model in the range, the 21BV, is designed for cables with a cross section of up to 400 mm² and can conduct loads of up to 1MW (1000 A, 1000 V). The bayonet fitting on even these giants can be operated with one hand.

Power is only transported once the built-in microswitch signals to the controller that a conductive connection is closed. This ensures the safety of the operating personnel and prevents dangerous faults on live parts.

Multi-Contact AG is based in Allschwil, Switzerland.

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