The Impact of Sustainable Communities on the Low Voltage Distribution Network

Electric Vehicle Loads

 

 

This project was a scenario based project and therefore it was essential to create various load profiles for the Electric Vehicles (EVs) in order to assess the impact on the Low Voltage (LV) distribution networks.

 

From the all-encompassing studies which were made, it was determined that there was both an infrastructure constraint and the demand/response issues on the network. Therefore, the profiles had to capture these dimensions. (Associates, 2012)

 

In relation to the infrastructure constraint, two different types of charging scenarios were created:

 

 

The fast and slow charging was related with the current capacity in the wires and how much they could take.

 

Based on the Literature Review it was found that there was a third option of vehicle charge that corresponded to rapid charge on a power demand of 50kW. However, this alternative could not be considered in domestic level charging as this power demand is too large for the LV network within the domestic housing network.

 

In relation to the on-peak and off-peak charging scenarios, there were evidently different times of the day that would affect the loading on the grid. For that reason, the timescales were split up into off-peak and peak categories, as shown in the figure 1 below.

 

Figure 1: Electric Vehicle Charging Categories

 

 

As shown in the table above, there were various scenarios that the user could choose from when selecting establishing their estate definition in the WRISC Tool.

 

 

Assumptions

 

Towards establishing the load profiles for the electric vehicles some assumptions needed to be made:

 

 

 

Calculations

 

The calculations were part of the analytical technique for finding the EV load profiles.

 

An analysis was steered in order to determine the power conditions of charging at domestic level, so that it would define what the minimum and maximum peak power conditions would be as illustrated in table 1.

 

House Conditions: 240V, 15A circuit breaker

Slow Charge

Energy consumed = 3,600W over 1 hour = 3.6 kWh

Battery requires 25 to 28 kWh therefore 8 hours to recharge

House Conditions: 240V, 32A circuit breaker

Fast Charge

Energy consumed = 6,600W over 1 hour = 6.6 kWh

Battery requires 25 to 28 kWh therefore 4 to 5 hours to recharge

Table 1: Electric Vehicle Charging

 

A normal household of 240-volt outlet typically has a 15-amp circuit breaker, meaning that the maximum amount of energy that the car could consume was approximately 3.6 kilowatt-hours. Since the battery pack in the car normally needs 25 to 28 kilowatt-hours for a full recharge, it could take 8 hours to fully charge on a slow rate, and 4 hours to fully recharge at the fast charge rate at 6.6 kWh. (Yang, 2012)

 

Electric Vehicle Profiles

 

 

Figure 2: EV Charging Profiles

 

 

The above figure 2 illustrated the EV profiles showing on-peak slow and fast charging.

 

The green graph symbolised the slow charge on-peak, and the blue symbolised the fast charge on-peak. Moreover, it was shown that the fast charge was of a higher power demand but at shorter period of time than the slow charge.

 

The EV profiles were daily rather than weekly, in contrast with the housing profiles. This was due to the fact that according to the initial considerations, the electric vehicle could be charged based on the different occupancy profiles in the event of the vehicle being present at the house, this allowed users to specify different charging times. The selection of whether to charge on a slow or fast rate was indicative of the duration of the charging process.

 

All the aforementioned elements were integrated in the WRISC tool alongside the housing profiles so that the investigation process could be carried out.