Presentation at Ökobilanzwerkstatt 2017 in Braunschweig Poster at NTNU Sustainability Science Conference 2017 in Trondheim
The energy transition - including the transformation of the mobility sector - requires new technologies, many of which come with an increasing demand for critical resources. Approaches from the circular economy, such as sharing and reuse, can lead to increasing resource productivity as well as new opportunities for value creation.
If life cycle assessment (LCA) is used to assess the environmental saving potential of circular approaches, several methodological challenges exist. The present analysis illustrates these challenges using the example of lithium-ion traction batteries in electric vehicles.
Sharing and reuse (Second-Life – SL) are identified as two technically feasible circular approaches for traction batteries. During its first life in the vehicle the traction battery can for example be used for load management by offering vehicle-to-grid (V2G) and thereby sharing storage capacity and power among the vehicle owner and a company (compare figure). Furthermore, after its end-of-life in the vehicle the used traction battery can be reused in a stationary application, for example as a photovoltaic home storage system.
Figure: Schematic representation of a vehicle-to-grid sharing concept for electric vehicle batteries (black=original life cycle, turquoise=life cycle with sharing)
Based on a literature review the following main challenges for LCA of reuse and sharing of electric vehicle batteries are identified:
- The delivered function and the lifetime of the storage system are dependent on the battery ageing process and thus the load profile and the state of charge.
- Due to a temporal delay, the future development of the disposal process needs to be included.
- The emissions need to be allocated between different functions (mobility and energy system service).
- In the case of system expansion, knowledge of the energy system is needed in order to determine the substituted technologies.
The case study on V2G for industrial peak load management shows that in the analysed case the impact of V2G on CO2 emissions is relatively low. However, the emissions accounting method (marginal vs. mix approach) has a strong influence on the results.
Finally, it is concluded that in case of a consequential LCA of energy technologies, system effects can be accounted for by energy system modelling. Furthermore, a prospective LCA approach is required for the assessment of circular approaches because temporal delays play an important role, especially in case of second-life applications.