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Battery Buffered Electric Vehicle Charging

The challenges of charging

As the need to lower carbon emissions in the UK heightens, the transition from solely internal combustion engine (ICE) vehicles to hybrid or fully electric vehicles (EVs) accelerates.

Despite many people prioritising the reduction of their carbon footprint both in their personal and professional lives, concerns over the practicality of EVs including range anxiety and charging time has suppressed the uptake of EVs compared to its expected boom.

It is clear that EV charging infrastructure is improving, according to data published in November 2019, there are currently 7033 rapid chargers in the UK network [1], a 43% growth year-on-year [2]. When compared with the availability of ICE fuel, however, around 8,394 fuelling stations exist in the UK [3], and when the difference in time to charge the vehicles is taken into account it shows how far behind the infrastructure is. Consider a fossil fuel car forecourt transaction which can be completed in under 10 minutes, supporting a steady flow of traffic. In comparison, charging an EV can take from 30 minutes to 12 hours to get to 100% state of charge, depending on the available capacity, meaning that far more charging stations would be required at a rate of 3 or 4 to every 1 petrol pump.

Despite there being a need for rapid chargers, they are not a comprehensive solution as they bring about their own limitations. Rapid chargers can charge a standard EV vehicle from 20% to 80% state of charge in approximately 30 minutes at a 50kW output power. However, they are restricted to areas where the supply can sustain a sudden 50kW load. This means that in highly constrained areas such as city centres where many companies and therefore fleets will operate, a costly grid reinforcement is required in order to install rapid chargers and guarantee enough power is available to undertake the process in the allotted time.

For example, if a commercial company has an electric fleet of 20 vehicles, and these vehicles are kept to a tight 24-hour schedule, it is essential that these vehicles are charged quickly. However, if 10 cars are charging simultaneously at a 50kW rapid charge this generates a large demand of around 500kW which many businesses cannot sustain. To complicate matters further, the cost to upgrade a sites capacity to support this demand has been identified to cost anywhere from tens of thousands up to millions of pounds, eroding the economic benefit of upgrading to an EV fleet.

Buffering the cost

One solution is to support rapid EV charging with battery-based energy storage. This not only enables a business to charge its fleet from the stored energy when required, negating sudden increases in demand, but it will always supply the highest possible charging rate by utilising stored energy to handle the unexpected ramp up in power. This, therefore, eliminates the need to reinforce the grid in order to deliver a rapid charge, saving on the financial costs and operational disruption that would otherwise occur.

As more people and businesses switch from ICE vehicles to EVs there is a necessity for suitable infrastructure to be in place to accommodate this. As habits will change, and simply filling up at a petrol station will no longer be the norm, many will look to charge their vehicles at places where they stay for long durations, such as offices. Battery buffered EV charging is a cost-effective way of meeting this need as it does not require the disruptive and expensive grid reinforcement that installing multiple rapid chargers does, and also has wider benefits to a business through its energy storage component.

Making hay while the sun shines

One of the contentious topics around EVs is where the energy for charging batteries is generated from. With countries working towards their emissions targets such as those set out by the Paris agreement, it is desired that a larger amount of this energy is provided by renewable sources, such as solar (PV) and wind power, as fossil fuel shrinks as a proportion.Battery buffered EV charging

Solar (PV) in particular can be utilised behind-the-meter within local micro-grids to generate cheaper, greener energy to support EV charging and maximise energy flexibility. Either roof mounted or as a canopy, can be integrated to achieve this and the benefits that can maximised with the use of an Energy Optimisation System (EOS).

Through an EOS, the activities of an integrated solar and energy storage system can be prioritised, depending on the state of charge, EV charging requirements, and the needs of the site. The EOS can allocate power to battery charging or to support the site during power failures, if required, and can optimise the processes involved on an automated basis utilise algorithms and forecasting, reducing reliance on the grid.

As an asset combined with battery energy storage system, it can provide a range of additional benefits including peak shaving to generate energy savings and, grid balancing services to generate revenues, providing added value when EV charging is not required.

Marrying up storage, buffered charging, and solar

It is evident that EVs have a major role to play in the transport networks of the future, and that this presents challenges in balancing the required demand. As a standalone technology, EV chargers are restricted by the grid in many scenarios. However, deploying EV charging with energy storage offer opportunities to expedite the expansion of both technologies, and the mainstreaming of EVs themselves due to the benefits that battery buffered charging can deliver, not only reducing the surge of demand but also reducing the cost of charging whilst allowing greater flexibility, including fast/rapid charging speeds for fleet managers than would otherwise not be achievable. When solar generation is factored in too, the cost of running EVs, and organisations’ carbon footprints can be reduced further through combining the discussed assets into a site wide solution. To read more on battery buffered EV charging click here.

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Energy Flexibility


18 December 2019


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