EV CHARGING IN MULTIPLE FAMILY DWELLINGS

Demand for Electric Vehicles is accelerating. The large number of people residing in Multiple Family Dwellings (MFDs) share an interest with single family homeowners in wanting to have the ability to charge their EV where they live. However, HOAs, Co-ops and apartment building owners often hesitate as the costs to bring EV charging to parking spaces can be considerable, similar to building and parking lot maintenance, HVAC refits, water supply repairs and other real but necessary operational expenses. Conversely, adding EV Charging can add value to the property and its attractiveness to current and future residents.

CHARGER TYPES

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Level 2 Sharable Charging

There are two up front decisions to consider when looking into EV Charging Stations also called Electric Vehicle Supply Equipment (EVSE):
1. Communal (shared) EVSEs provide the ability for one charger to charge many users.

  • For apartment buildings, use of sharable EV Charging Stations is a common solution. This is also a good solution in condos when there are parking spaces that the building/HOA owns and can be shared or for renters to share in common parking areas.
  • In either case, the metering and billing of the electricity is typically managed automatically.

2. Dedicated EVSEs typically provide the ability for one user to charge with one EVSE. This is a common approach for deeded parking areas

  1. Non-networked with manual metering and billing
  2. Networked and automated metering and billing
  3. Non-networked with semi-automatic metering and billing

POWER LEVELS

The other key considerations are the power level of the EVSEs and the facility power capacity.Image number 3 - Multiple Family Dwellings - Green Ways 2Go

Power levels are calculated by multiplying the voltage times the amperage. There are two groups of EVSEs, Level 2 (Alternating Current) and Direct Current (DC) Fast Charging (DCFC).

Level 2 AC charging starts with either 208 VAC or 240 VAC and the amperage can range from 16 Amps to 80 Amps. This results in a power output range of 6.6 to 19.2 kilowatts (kW). Importantly, if an EVSE can output a certain amperage, the EV may not be able to accept the power. Each EV has a device that converts the AC voltage to DC voltage on board the EV and this will act as a control point for how much power gets converted. For example, older Chevy Volts only take 16 Amps (3.3. kW) and some newer EVs can take 19 kW. Almost all EVs can accept 32 Amps, which has been the standard to date.

DCFC normally use 480 Volt (or higher) power at higher amperage and can provide between 25 and 200 kW of power. So far, these are uncommon in MFDs due to their significantly higher cost. To support such investments typically means charging residents higher fees and high utilization rates are needed.

EV ENERGY MANAGEMENT SYSTEMS (POWER SHARING)

EV Energy Management Systems (EVEMS) involve charging power allocation and/or charging time allocation.  Use of EVEMS is a fairly new but growing approach in MFDs and is something that decision makers should consider, as it can “stretch” the electrical infrastructure so that more residents can have access to EV charging by sharing limited facility resources before the need arises to upgrade the utility service.   This is especially true when retrofitting MFDs.  Power (current) can be split between simultaneous charging events, by up to a 4:1 ratio. 

EVEMS may be integral to the EVSE or may be integrated into an electrical panel or even a building energy management system. More at……..

METERING AND BILLING SOLUTIONS

As residents charge their EVs, they consume electricity from a host facility.   In most cases, the facility power is a common resource and a shared expense, so a means of measuring the amount of electricity (typically in kilowatt hours (kWh)) for each charging event used by an EV owner is required, so that a bill can be generated, and the facility reimbursed, as the property owners typically pay the utility.   The measurement occurs using sub-metering, which involves measuring the current in the circuit conducting wires, using a Current Transformer (CT), which transforms the current flow charging the EV into a signal that is then converted to cumulative kilowatt hours of energy over time, which is the power used during a given period (e.g. kWh per month). 

Non-networked EVSEs with Manual Metering and Billing

The simplest solutions include CTs mounted on conduit that provides power from a panel to an EVSE.  The CTs calculate the amount of energy and present the data on meters, providing a cumulative totaling of all the kWh passing through the wires inside the conduit.  To bill, this requires someone to periodically read the total energy on the totalizing meter, subtract this value from the previous reading to get the energy consumption for that period and then multiply by the billing rates (i.e. $/kWh).

Networked EVSEs and Automated

Many EVSEs today have integral sub-meters and automatically calculate the energy and power used.  This approach is the most convenient for all parties, and there are regular subscription fees that support the services.   These data are wirelessly communicated to a third-party network service provider that manages the billing.  The EV user, with an account, gets billed for the electricity and the facility gets reimbursed.   Wireless communication may use a cellular network and the Internet and/or WiFi local infrastructure networks.    Note, to apply this approach requires a standard EVSE brand for all participants.    

Non-networked EVSEs with Semi-automatic Metering and Billing

An alternative is to integrate the CTs within an electrical panel system, which calculates the energy, captures the data in a data logging device and then provides results to the facility on a regular basis, using either cellular or WiFi.    This approach does not require all the EVSEs to be of the same brand.  NEMA outlets can also be used in combination with networked or non-networked EVSEs.  Further, the EVSEs can have different power ratings.

SIGNAL AMPLIFICATION