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Set your own limits - energy storage for EV charging hubs

We look at how battery energy storage supports EV charging when grid infrastructure is problematic…


As demand grows for more workplace, fleet and public EV charging, our grid infrastructure is struggling to keep up. So, what happens when the demand for energy is higher than the available capacity?

Plug-in vehicles represent over 20% of new car sales, and this trend is only going to accelerate. In addition, all-electric vans are becoming more widely adopted, typically with bigger battery packs than cars, which brings its own unique demands on charging infrastructure for a fleet scenario. The first fully electric trucks are also now available from traditional OEMs like Volvo Trucks and Scania, as well as challenger brands like Tevva, raising the bar once again in terms of charging needs.

It is easy to see that the transition to EV will bring incrementally increasing demands for EV charging infrastructure, both in terms of more charging points and also the need for a quick turn-around of vehicles that only rapid charging can provide. In the first phase of EV adoption, almost all organisations required only a handful of EV chargers, meaning most sites could handle the extra energy requirements.

However, we are now at a pinch point in our EV transition, where sites require many more chargers, including chargers with higher capabilities. Currently, supply constraints are restricting the ability to meet demand.

Fundamentally, EV charging at scale creates spikes in power demand, on sites with limited capacity. There are currently three options to address this:

1. Load balancing

Smart chargers can be networked to ensure that all vehicles plugged into that network will still receive some charge, albeit much more slowly than expected. For example, if four EVs are connected to 7kW charging points, but there is only 10kW of power available, the EVs will charge at 2.5kW each. In this way they still all receive a fair share of the available energy but are charging at a much-reduced rate.

Whilst load balancing provides a low-cost, interim solution, it does have a major drawback. Vehicles do not charge at the expected rate, which can create problems for drivers who expect a certain percentage of battery power to be replenished within a given time frame.

2. DNO upgrade

The most obvious option is to buy an infrastructure upgrade from your District Network Operator (DNO). However, this can be extremely expensive – hundreds of thousands of pounds in many cases. In some areas, it is simply physically impossible to bring in additional power.

And the cost/benefit analysis does not favour this option for EV charging hubs. This is principally because the way EV charging hubs operate means that they only require additional energy capacity when demand is high, such as when the bays are full or nearly full. The rest of the time, this additional energy is not required. This translates to a more extended time frame for your return on investment from a DNO upgrade.

3. On-site energy storage

Until recently this option did not exist – but now it is set to revolutionise EV charging infrastructure provision.

Put simply, batteries previously used in EVs are repurposed as on-site storage. They draw energy either from your renewables such as PV solar arrays, or from the grid at times when it is either not needed on site or when electricity is cheaper. This energy is then available to meet those spikes in demand during busy periods, ensuring that drivers get the amount of power they expect when they plug in, but in a way that is much more cost effective than a DNO upgrade.

A Connected Energy battery energy storage system can be used in two different scenarios:

Boosting capacity: a site with some constraints during peak times

When a site has some constraints and requires additional power at certain times of the day, our battery energy storage system can act as that buffer.

One example of this is our E-STOR system which has been installed in Dundee to support the city council’s innovative EV charging hub. This was the first hub in the UK to include 22kW and 50kW rapid chargers.

We programmed the E-STOR to monitor the grid load, to ensure demand is always met. If demand from vehicles plugged into the hub gets close to exceeding the power available from the grid, E-STOR kicks in to bridge the gap. This ensures that the Council does not face any penalties for exceeding their limit.

The Connected Energy system also tracks charger usage and generation from PV array, maximising the contribution that solar power makes to charging. This not only helps to maximise the green energy used to charge the vehicles but it also means that solar power can be used during the evening – when the sun no longer shines – and therefore helps to reduce costs, find out more about Dundee’s project.

Active charger management

The second scenario is when a site simply does not have the power that the chargers required.

Connected Energy has worked with Allego to install battery energy storage systems in Belgium and Germany to help overcome this scenario. These sites provide 50kW DC rapid charging, but only have 40kW connections to the grid.

Whenever a driver plugs into the network, the Connected Energy system communicates with the charger to provide the additional power needed. This communication is achieved via the Open Charge Point Protocol platform (OCPP), find out more about our Allego projects.

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Get in touch with our team to discuss whether battery energy storage can work for your business.