Increasing The Environmental Potential Of Electric Vehicles And Renewable Energies With Grid Attached Energy Storage

The environmental performance of electrical vehicles is directly tied to the electricity mix that is used during the charging process. Nowadays, with a steady increase of renewable electricity being introduced, its usage is not always optimal. Alongside, its intermittent nature makes wind and solar not suitable for applications such as EV charging. Using a life cycle assessment methodology we analyze the impacts of the construction, usage and disposal/end of life of each of the studied systems. Pumped hydro and compressed air storage are studied as mechanical storage and advanced lead acid, sodium sulfur, lithium-ion and nickel-sodium-chloride batteries are addressed as electrochemical storage systems. Hydrogen production from electrolysis and subsequent usage in a proton exchange membrane fuel cell is also analyzed. The functional unit is one kWh of energy delivered back to the grid/vehicle, from the storage system. The environmental impacts assessed are climate change, human toxicity, particulate matter formation, and fossil resource depletion. Different energy mixes are used in order to mimic scenarios where the environmental applicability of the technologies is put to the test. Results indicate that the performance of the storage systems is tied to the electricity source used during use stage. Renewable energy sources have lower impacts throughout the use stage of the storage technologies. Regarding infrastructure and end of life, battery systems have higher impacts than mechanical ones because of lower number of cycles and life time energy (9.000 fold). The environmental performance of the use stage of an EV fluctuates as the overall impacts of the supply mixes change with different storage technologies up to 32 fold.