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Economic and technical feasibility of a storage-as-a-service model using second-life batteries for a commercial end-user

As part of the EU Horizon 2020 CIRCUSOL project, Belgian PV installer and investor Futech investigated the technical and economic feasibility of integrating a second-life battery storage system at an existing 2MW solar plant in Belgium. The system originates from the automotive industry and was successfully commissioned in August 2021.

CIRCUSOL stands for “Circular Business Models for the Solar Power Industry”.  It is an Innovation Action project funded by the Horizon 2020 program under the European Commission.  It brings together 15 partners from seven European countries to develop and demonstrate business solutions for a circular economy in the solar power sector. The CIRCUSOL project started in June 2018 and will end in November 2022.

CIRCUSOL aims to deliver circular PSS (Product-service systems) business models with real environmental benefits and economic feasibility, validated in five real-life commercial demonstrators.

One of the demonstrators is the Cloverleaf PV plant in Heusden-Zolder (Belgium). Next to the 2MW PV plant, the site includes a shopping mall with a restaurant, a fuel station, a covered parking for acclimatized Trucks that can connect when parked, and a charging spot for electrical vehicles.

Storage-as-a-service
At the start of the CIRCUSOL project, Futech was already (since 2011) into an ‘energy-as-a-service’ agreement with the facility owner for the energy produced in the PV plant. Under this agreement, as being the investor, Futech remains the owner of the PV plant and is also responsible for its maintenance. The facility owner, for their part, contributes a monthly fee for the electricity consumed that is significantly lower than the grid electricity prices.

One of the objectives at the start of the CIRCUSOL project was to increase the self-consumption level at the Cloverleaf site from 22.8% to at least 50%. The increased self-consumption level was expected to be attractive for the facility owner since the tariff is lower than grid tariffs. The facility owner agreed to integrate the storage component and a new Power Purchase Agreement (PPA) was negotiated.

Self-consumption increase
To determine the optimal battery size, Futech analyzed the evolution of the consumption level at the Cloverleaf site. Since the installation (in June 2017) of a charging spot for electric vehicles, consisting of 12 superchargers, the consumption level significantly increased as is shown in the graph below. Mind that the decrease in consumption in 2020 was caused by the closure of the restaurant during the Covid-19 pandemic.

Cloverleaf site increased from 22.8% to 45.4%. Because of its favorable location nearby the E313 and E314 motorways, plans are currently being made for installing additional DC fast-charging stations at the Cloverleaf site which will for sure influence the self-consumption level positively.

This is why Futech decided to implement, at first instance, a relatively small second-life battery system totaling 84kWh. Such a system meets the minimum threshold of 300 battery cycles per year in contrast to, for example, a 200kWh system. Depending on the evolution of future consumption at the Cloverleaf site, the battery capacity can still be extended in the coming years.

Technical feasibility
After an intensive consultation round with Futech on its requirements, the 84kWh second-life battery system, originating from the automotive industry, was supplied by the French company SNAM. First, a battery rack of 21kWh (360V) was intensively tested in the Futech lab. Minor issues on the Battery Management System and the State of Charge were resolved relatively smoothly.

Unfortunately, after consultation with the local grid operator, permission was not granted for DC integration because some new components were at that given moment not yet technically certified. A few months after commissioning, the certification issue was resolved. In case of any future expansion of the second-life battery storage system, Futech would opt for the implementation of DC technology because of its higher round trip efficiency.

During the month of August 2021, Futech successfully integrated and commissioned the second-life battery at the Cloverleaf demonstrator. Parameters like the number of cycles of the battery along with its health status are permanently monitored in order to get an indication of the expected lifespan of the second-life system. The first findings appear to be very promising.

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