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Electric vehicles - impacts on the power system
The Commission considers it reasonable to assess the impact electric vehicles (EVs) and plug-in electric vehicles (PHEVs) may have on electricity demand, and on generation and transmission development. Support for EV development has recently been signalled through the NZES, and internationally, there is clearly a great deal of research and development directed toward commercial availability of these vehicles.
Due to the typically short daily commute distance in New Zealand, the electricity demand of either PHEVs or EVs would be very similar (i.e. even for a PHEVs, most trips would be fully electric). Consequently the term ‘EV’ is used loosely to refer to full EVs, PHEVs or fuel cell vehicles.
The EV demand has been modelled as additional component of demand, added to the base forecast in some of the generation scenarios. The EV demand forecast is based substantially on an EV penetration scenario developed by the Ministry of Transport (MoT), using their Vehicle Fleet Emissions Model (VFEM). The VFEM produces a projection of total number of vehicles of different types (Figure 1), and total ‘Vehicle Kilometres Travelled’ (VKT).
Additionally, MoT provided the Commission with trip distance data from the Household Travel Survey (HTS). Assuming a pro-rata allocation of VKT to the total EV fleet, an assumed EV daily range, and energy consumption per VKT, a simple calculation yields the EV energy demand, in GWh per annum. Data from the HTS also enables an allocation of EV demand on a regional basis. The resulting EV energy demand forecast is illustrated in Figure 2.
There are a number of options for recharging these vehicles; for instance they can be charged overnight (‘off-peak’), or the load can be spread over the entire 24 hours of the day (‘anytime’). The Commission considers that ultimately EVs are likely to be charged off-peak, with some ability to shift the charging time in response to price or other supply side constraints. It is possible that EVs will participate in balancing intermittent generation (through smart metering and Vehicle to Grid (V2G) or Vehicle to House technology), and may enable a greater penetration of wind generation into the electricity system. These issues are still under investigation by the Commission, and will be represented in the GEM model at a later date.
For now, the Commission has assumed a charging profile for the demand that is mostly off-peak, with some small contribution during peak demand periods. In the ‘demand side participation’ scenario, the EVs were also modeled as a price responsive curtailment, to mimic the V2G technology. In this scenario the presence of the EVs caused a reduction in peaking plant requirement from 1400 MW to 850 MW in 2040, illustrated by the peaking plant build schedule in Figure 3.
Future investigation of these issues will require representation of demand side response, wind variability, pumped hydro, and wind balancing, and other reserve types in GEM.
Additional information:
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