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EV Charging Challenges for High Density Residential Facilities

Introduction

The collision of two major market transitions (shift to EV’s and shift to densification of housing) has created concern that the electricity grid will be able to provide the energy required. This study demonstrates that combining onsite generation and batteries with intelligent energy management has the ability to address this issue.


The Problem

As the residential market in Canada is moving towards densification to satisfy the growing population in urban centres, there is growing interest in providing EV chargers for high density residential facilities. This is evidenced with the growth of Unico Power in this market with over 100 installations in Western Canada.


High density residential developers and condo owners recognize the growing demand for EV chargers at their facilities – and that there is strong motivation to maintain the value of their properties by providing an EV charging capability.


One of the biggest challenges for EV charging in high density residential buildings is the peak power demand. In a residential complex, the cars tend to plug-in to chargers when the electricity demand is at its highest – around 5-8pm. Without intelligent power management, a large number of EV chargers will dramatically increase the peak demand for the grid. This has a significant impact on the cost of electricity at the facility.


Intelligent Power Management

Cerebro™ from Unico Power provides intelligent power management for EV charging in high density residential buildings by watching the peak demand of the building and not allowing EV chargers to exceed this limit. The result is that the EV’s have no impact on the peak demand for the grid. However, there is a limit to the number of EV’s that will be fully charged by the morning before the buildings peak demand will need to increase.


A study at a high density residential facility has shown that the EV’s return to the chargers with 80 to 90% of charge remaining and only require an average of 4kW for three hours to return to a full charge. The energy required for each EV was monitored over a one year period. This shows that the majority of charge sessions required less than 6kWh over 1.3 hours.





The electricity consumption for a pilot facility is shown below – and demonstrates a peak demand of 125kW. The facility has 121 suites and is located in Calgary Alberta.



We then simulated the impact of EV chargers with the Intelligent Power Management system that limited power to 125kW. The simulation assumed:

· EV’s arrived between 5pm and 9pm

· EV’s left between 5am and 9am

· EV’s required 4kW for 3 hours to receive a full charge

· All EV’s must have a full charge by 5am


Without Intelligent Power Management and allowing the EV’s to consume as much power as they needed starting as they arrived, the peak demand for the facility would almost double and reach 235kW with 38 EV chargers. In the chart below, the grey line is the original facility power and the red line is the power required for both the building and the EV chargers.



Zooming into one week, we see the power for the EV’s starting to increase at 5pm and reach its peak at 9 to 10pm before reaching full charge for the EV’s at about midnight.



With Intelligent Power Management, the grey line shows the original building power and the red line shows the energy required from the grid as a result of adding 38 level 2 chargers – demonstrating that this building can support 38 EV’s without any power demand increase from the grid.



Zooming into one week, we can see the increase in power (red line) to support the EV chargers over the night hours. Each EV is fully charged by 5am.




Onsite Generation

The next challenge is to determine how much additional power would be required in order to support 100 chargers. Even with intelligent power management, the building would need to increase its peak demand to 175kW, which would increase electricity costs by 53%.



Zooming into one week, we see the peak demand increase to 175kW.



Introducing onsite generation will increase the number of EV chargers that can be supported while maintaining the existing peak demand for the facility.


With the introduction of a 50kW onsite generator, the facility is able to support 100 EV chargers and still maintain the original 125kW peak demand for the facility. The grey line shows the original building power, the blue line shows the onsite generation and the red line shows the grid power demand.



Before introducing onsite generation, the peak demand increased to 175kW with Intelligent Power Management.



After introducing a 50kW onsite generator (blue line), we can see that the peak demand from the grid (red line) is now limited to 125kW.



Conclusion

Managing the peak demand at a high density residential facility is critical for two reasons

  1. Managing the costs for transmission and distribution are primarily based on the peak demand.

  2. Availability of power from the local distribution company. If the facility can limit the increase in power required, many more EV chargers can be made available and still meet the needs of the tenants.

The combination of Intelligent Power Management and small onsite power generation can address these challenges.





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