Worldwide we are in the midst of a big transition away from internal combustion cars and their network of gas stations to electric vehicles (EVs) and new arrangements for powering them.
This article addresses the challenges of adding chargers at scale to multifamily residential facilities where parking is not adjacent to each living unit.
Beginning and scaling up charging initially seems incredibly daunting. Most parking garages, carport structures and parking lots have very limited electric capacity. And it can be challenging to see how to make the economics of wiring, charger purchase and electricity costs work out.
Ecovillage at Ithaca (http://ecovillageithaca.org) has been working on scaling charging infrastructure to their 100 households since 2017, and has devised some strategies that have made EV buildout practical and reasonably cost effective.
- Focus on installing 240-volt, charging-ready outlets, not chargers.
- Use daisy-chained wiring for charging circuits.
- Choose chargers with circuit-sharing capabilities.
- Standardize equipment by committing to one brand (manufacturer) of networked chargers.
Plan ahead for scale
These strategies are linked – each depends on the others to make them workable.
Let’s look at them one by one:
Installing 240-volt, charging-ready outlets
A useful goal is to have at least one parking space for each household pre-wired and ready to receive a charger. That means focusing first on how to provide the most 240-volt, 40-amp outlets using the financial resources and service capacity currently available.
Why is this helpful? Because it allows for much cheaper wiring strategies and avoids tying up capital in buying chargers today which may not get used for years if particular residents are not yet ready to purchase an EV.
Ideally these outlets should be in the parking spaces already assigned to residents, rather than set up for shared charging, as the resident experience is much more convenient and billing is simpler with dedicated chargers.
The problem with typical charger wiring is that large, dedicated circuits are used for each charger, which needlessly ties up valuable electric service resources. For example, if a given garage building is served by a 100-amp circuit, then only two to three chargers could be installed in that entire building unless measures are taken to address that.
One of those measures is daisy-chained wiring. This means that, instead of each 240-volt outlet having its own circuit connected back to the electric panel, you connect five to ten outlets in parallel on the same circuit. Thus, to wire a set of adjacent parking spaces, you need only one home-run circuit to the electric panel and then short hops of wire from one parking space to the next. This reduces the cost per outlet significantly, and allows a small electric service to support many parking spaces.
Choose chargers with circuit-sharing capabilities
To make daisy-chained wiring work without overloading circuits, we need to use chargers that can communicate to dynamically limit charging rates. Such chargers allow for the creation of charger groups for which a total current limit can be configured, and generally require a network connection to make it work. When implemented properly, this feature continually adjusts the rate for all chargers in response to the coming, going and the completion of charge cycles of the vehicles.
It is important to remember that each EV does not need to refill its entire battery capacity each night; most cars daily typically drive 30 miles or less, so they only need a few hours on charge to top off. This can allow, for example, a 100-amp service to effectively serve at least 20 EVs.
Standardize on one brand of networked chargers
Selecting a particular brand of chargers which have the ability to communicate over a Wi-Fi network allows for a number of important benefits:
- Today, only chargers from the same vendor can perform the dynamic circuit sharing described above.
- Using the same vendor means that charging statistics from all chargers can be collected and downloaded in one place. This greatly facilitates billing.
- Maintenance people become familiar with their installation and operation.
- All chargers have the same capabilities, so policies and management are straightforward compared to a random mix of chargers.
The EnelX Juicebox product line is one example of chargers that support this strategy.
Plan for scale
This simply means, operate from the assumption that eventually most of your residents will need access to charging. Thus, you avoid taking shortcuts that work OK at first when there are only a few EVs but which become a major headache later on as EVs proliferate.
Some examples of scale-related thinking:
- Seek to automate data collection. If you are doing billing for user-charging activity, choose equipment that can automatically accumulate such data in one location that allows for bulk downloading.
- If you are administering resident billing yourself, rather than using an outside network, craft clear policies that work at scale. Questions to answer include:
- Do you charge for power? If so, do you sell at cost or add a markup?
- How do you calculate energy costs and what aspects are included?
- Do you charge any session fees in addition to per-kWh charges?
- Do you charge any fees to fund ongoing maintenance of your charging infrastructure?
- Who buys the chargers, you or the residents themselves?
- Plan for growing electric service needs. This can mean thinking about how you do wiring today in ways that won’t require (much) rework later as you need more capacity. Sometimes it means installing some conduits and wires you don’t yet need if it is cheaper to do so now. It also means working with your utility company to take advantage of programs such as the New York’s EV Make Ready program that helps fund such upgrades.
Some specific examples from Ecovillage Ithaca
Ecovillage at Ithaca has been making use of these strategies since 2017, and is well along the way to their goal of one charger per household. They currently have around 25 EVs for their 100 households, with more added monthly.
Here are some implementation details that may be of interest.
One question is where to mount outlets and chargers within a carport? They typically mount the chargers up high above the vehicles, because that simplifies wiring and protects equipment from damage. Then they attach the charging cable to the ceiling and drop it down conveniently wherever the charge port happens to be located on that specific vehicle.
Generally, chargers are purchased directly by residents and the maintenance crew mounts and configures them. That saves capital and leaves the residents responsible for any service or replacement costs.
For charging outside of roofed structures, they use a simple fence-like structure to mount charging outlets. This makes it easy to wire multiple outlets by running along the cross beams, and it is easy to expand. They have benefited greatly from incentive programs to help fund this build out. Be sure to check for any local or federal incentives to support your efforts.
EV’s are coming fast, so access to charging will become a key factor in attracting residents. Now is the time to start getting ready so you can do your part to move this transition forward.
Jeff Gilmore is an engineer consulting on computer technology and renewable energy projects under the name Localforce.io. He and his family live at Ecovillage at Ithaca in Ithaca, NY.
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