Battery storage can be used to absorb peak loads in the case of irregularly produced solar power or to optimise self-consumption. Used batteries from electric vehicles are also used in this process.

The electrical wholesaler Otto Fischer AG is currently testing such a so-called “Second Life” storage system. This compact power cube now stands on a small part of the visitor parking area in front of the headquarters.

Project status 80%

Visitors notice it immediately: the container directly at the entrance of the Otto Fischer company. This is an energy storage system designed to help make even better use of the electricity produced by the solar system on the roof of the building. And in a particularly environmentally friendly way. Finally, with the adoption of the Energy Strategy 2050, the Swiss population has decided to focus on sustainable resources. Initially, this means that energy efficiency is to be increased and the expansion of renewable energies promoted as part of the first package of measures.

Building owners are therefore also called upon to make their contribution to the energy strategy. In concrete terms, this means that so-called “prosumers” are now being promoted in places where previously only consumers could be found: Consumers and producers at the same time. The aim here is for energy supply to become increasingly decentralized – which poses a challenge for the power grid. This is because the feed-in of solar and wind energy is characterised by strong fluctuations. That’s why smart grids and technologies like batteries are needed to store electricity temporarily.

That’s why Otto Fischer is currently testing a battery storage solution to make even better use of the solar power they produce themselves – with the help of this container, which is located in front of the main building.

In the future “Second Life” applications

Batteries are increasingly being used in buildings. For example, to minimize peak loads, to optimize self-consumption or even as a backup in the event of a grid failure. However, the production of batteries requires key raw materials such as lithium, cobalt and nickel. It would therefore make sense for batteries to remain in use for as long as possible. Batteries that have been used in electric vehicles, for example, are still usable after their use in the car. The reuse (“second life”) of aged batteries from e-mobility in secondary storage applications can thus significantly extend the life of used lithium-ion batteries. This significantly increases the eco-balance of electric vehicles and can generate additional revenue.

The inner workings of the “power cube” with the reused electric car batteries.

Test operation in Zurich

Two years ago, the Otto Fischer company installed a photovoltaic system with over 900 modules and an output of 257.6 kWp on its roof; the electrical wholesaler consumes around 60% of the electricity generated in this way at its headquarters itself. In the sense of self-use of electricity, this is in need of improvement – for the environment and for lower electricity costs. In order to find out whether the use of a storage medium is worthwhile in this respect, it has been decided to test the use of a “Second Life” battery storage system in cooperation with the company Evtec AG from Kriens – a pilot test which should provide information on the dimensioning of the storage capacity.

The “power cube” is installed to store the electricity from the solar system.

Different modes of operation

Battery storage systems can be used and operated in many different ways. The two most common modes of operation are self-consumption optimisation and peak load optimisation, the latter being used more by commercial enterprises, as it can reduce power charges to the distribution grid operators. Furthermore, the storage systems can be used as backup or for control power.

For the pilot project on the parking lot of the Otto Fischer company, a combination of operating modes is used: on the one hand, self-consumption optimization and, on the other hand, peak load minimization. Peak load minimization is mainly useful on weekdays, with the aim of shifting and smoothing the peak load.

The increase in self-consumption, on the other hand, is often sought at weekends. Finally, the self-consumption is then only low, and thus the solar power can be temporarily stored in the battery at noon and used at a later time in the evening. Which means that the existing PV system with its output of 257.64 kWp is even better utilized: By operating the battery storage system, the company is now aiming for an increase in self-consumption of around 10-15 %, as well as a minimization of the power peak by 20 kW.

With load peak minimization, the load peak is shifted in time and smoothed.

With the help of a battery storage system, the increase of self-consumption as well as the minimization of the power peak are made possible.

SIA Data Sheet

The rapid development of battery storage systems and their increasingly widespread use prompted the SIA (Swiss Society of Engineers and Architects) to draw up the Code of Practice (SIA 2061) “Battery storage systems in buildings”. This contains dimensioning information and provides specifications for the integration and operation of the storage infrastructure, which is used in residential buildings as well as in commercial buildings or in mixed-use developments. The information sheet “SIA 2061” is expected to be published in spring 2021.

Briefly presented

The most important key data on the “Second Life” electricity storage system can be found here in a compact overview.


  • “Second Life” battery from the Nissan Leaf model (24 kWh)
  • Laminated lithium-ion battery
  • Battery cells: 192 (24 kWh)
  • Battery voltage: 350 V (24 kWh)
  • Mains connection: 3 × 400 V AC


  • 4 × 24 kWh, Total 96 kWh (nominal)
  • 4 × 10 kW DC power module
  • Total 40 kW DC charging and discharging power


Alessandro Buriola
Head of Product Range Development, Otto Fischer AG