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| 6 | vehicles (LDVs). If electric trucks become a reality, the figures could be very conservative. The timescales associated with the build-out of charging stations needed and the upgrade of utility infrastructure extends way beyond government administration terms and immediate politics, but utility providers are anyway buying into the long-term inevitability of EVs and planning to have sufficient base energy supply. With infrastructure expansion for a growing general market anyway, the extra 15% for EV charging is not seen as problematic at the generation level. In distribution, however, as you get closer to the charging cable at the car, the situation is different. Figure 3: High-voltage distribution will have capacity for EV charging. (Source: Mouser Electronics) Distribution Hardware for Future EV Charging Needs Historically, electricity demand is low during the night, with load spiking at maybe 7am as toasters, electric showers, and other domestic appliances kick in. It happens again in the early evening as cookers and heating/cooling work hardest. Add home EV charging to the mix, and the pattern changes dramatically, with load now peaking during the night so the car is ready to go for the morning commute. Standard home chargers might be 3kW or 7kW, taking 6 to 12 hours to charge a full EV or 2 to 4 hours for a plug-in hybrid electric vehicle (PHEV). This is "only" like running a high-powered heater or two all night, but "fast" chargers can be rated up to around 22kW. This now approaches the limit of the incoming domestic supply and is usually a higher peak level than without an EV, and certainly a much higher average level throughout 24 hours. This is an immediate extra stress on the local distribution network as more homes get EVs, with the transformers on poles that drop the medium voltages down to domestic levels humming loudly in protest. The high-voltage distribution network and the power stations don't flinch much as they are rated to supply industry as well, which is peaking at a different time. Local supply infrastructure might be the first bottleneck, with significant local variations – city apartments, for example, may have parking spaces, but the EV electricity supply won't come directly from the end consumer's supply. Rather, it would be metered but aggregated at a higher utility level where the load is "leveled" across domestic and industry and within the hardware ratings. The same is true of roadside and public fast charging points where the load is more directly on the high-voltage network. EV chargers are intelligent enough to control rate of charging so that the battery is ready at a programmed time with the required charge, but they don't know about other demands on the supply. There is opportunity for "smart" chargers to interact with the utilities to stage the charging of EVs in a neighborhood to keep the total load within bounds. This not only helps prevent overloading, but is also a positive benefit to the utilities who appreciate a leveled load, avoiding the expensive spinning up and shutting down of power plants from peaks and troughs of demand. In some areas the utilities encourage this with rebates and special rates for smart charging during off-peak hours. In addition to implementing a host of smart features and connected infrastructure, there are the usual challenges associated with designing high-power charging and battery monitoring systems both in the vehicle and for the charging infrastructure. Many of these are already well known to power systems design engineers, with energy efficiency, heat dissipation, and power line conditioning being among the top three considerations. In an electrical environment where high-power load switching happens regularly, the supply can experience dramatic high-speed dv/dt transients. Such high-voltage spikes can cause catastrophic and permanent damage to connected equipment if it is not adequately protected. The use of specialist high-power protection devices such as the Bourns ® Hybrid GMOV™ Components is highly recommended for all types of EV infrastructure equipment. Comprising a space-saving gas discharge tube and a metal oxide varistor in a single compact, low-leakage and long-life package, it provides a very reliable method of protecting any electrical circuitry from overvoltage transient surges. Win-Win With Renewables A long-standing objection to EVs is that they aren't so "green" as they make out if the electrical energy for charging ultimately comes from dirty coal or gas-fired generators. The situation is changing with increased use of renewables, but with the downside of unreliable supply without sun for solar at night and unpredictable wind for turbines. The ideal would be some means of energy storage to level supply capability, but there are no perfect solutions – hydroelectric storage in lakes only suits some locations, for example. While there are promising

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