Abstract
To decarbonize transport the New Zealand government is targeting the large-scale adoption of electric vehicles (EVs) and at the same time transitioning to 100 % renewable electricity supply by the early 2030s. Charging large numbers of EVs at times of peak electricity could have a significant impact on a 100 % renewable electricity grid. Reliably meeting peak demand becomes more difficult with high levels of renewable energy generation, due to the seasonal and daily variability of renewable generation. This is especially true in winter, and when hydro inflows are low (termed a ‘dry-year’).
The aim of this study is to use a model of New Zealand’s electricity system to examine the potential impact of increasing levels of EV uptake and the impact of charging EVs at different times of the day, including off-peak charging. A further objective of this study was to consider the dry years impact of EV uptake. To achieve these aims, three levels of EV uptake were modelled, including one projection that represented both light and heavy vehicle EV uptake. Additionally, four EV charging profiles were examined, with one profile representing an extreme scenario of off-peak, night only charging (termed the Night charging profile). Each of the three uptake levels were modelled with each of the four charging profiles, resulting in a total of 12 scenarios.
Analysis of the results comparing the three levels of EV uptake indicated that although increased EV charging demand meant an increase in generation capacity, there was no significant impact on system efficiency. However, supporting increased amounts of EV charging demand required increased grid scale storage utilisation and resulted in exacerbated system shortages.
Comparing the Night charging profile to the other three charging profiles showed that in the initial transition to 100 % renewable electricity, Night charging offered several benefits. These included increased system efficiency, increased system reliability, reduced average and peak electricity prices, and reduced use of grid scale energy storage. However, this extreme scenario of night only charging meant that when EV charging demand reached very high levels (from 2040 onwards) the scenarios with Night charging had a much stronger reliance on hydro generation. This resulted in increased average electricity prices, increased shortages, and increased dry year risk.
When considering the dry year impact of EV charging, it was concluded that early overbuild of generation capacity would reduce short term dry year risk even with high levels of EV uptake. However, in the long-term increased levels of EV uptake in dry years would result in reduced reliability and more volatile electricity prices. Night charging of EVs was shown to reduce the impact of a dry year on the electricity system initially. However, in the last decade of the modelling night charging resulted in reduced system reliability and increased electricity prices in low inflow years. Again, this was the result of increased reliance of hydro generation in the Night charging scenario. Overall, this study provides in depth analysis of considering the wider implications of EV uptake on the electricity system.