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We've been asked a lot recently, not only on these forums but directly via our website at www.solarcarprots.co.uk about the practicalities of using a solar carport, or a pre-existing solar PV installation to optimise the charging of EVs or PHEVs. Here are some thoughts to consider...

Most roof mounted home PV systems are of a capacity of 4kWp, and have a 3.6kW inverter attached to them, through grid connection restrictions. These were almost all installed on the basis of receiving a reasonable return on investment for 25 years initially, and more recently over 20 years from FITs and Deemed Export tariffs.

It would be fair to say that most of the installations were carried out with little to no thought as to the system's overall effectiveness of reducing electricity bills or using the power being produced by the PV array. As a result, many of these 800k plus installations in the UK have reduced bills by as little as 15%, and typically by no more than 30 to 40%. Effectively, all the people who chose to have these installed, myself included, were being asked to pay for a product, then only receiving as little as 15% use of it. That's like asking someone to purchase a new car, then having to allow everyone else to use it 85% of the time, leaving only 15% of its use to the person who paid for it. (or similar numbers if you look at the slightly better usage figures above).In either case, this is crazy!!

This is one of the few investments that people have made which they don't get the full use of, in most cases. If the FITs had been tied to the overall system's efficiency, then more thought would have gone into setting up the house's power consumption to best use the power being produced by the PV system, to avoid, where possible, grid spillage of unused power.

For example, using an ASHP to convert each kWh of PV power into heat, is better than using it to drive an electric heater directly. Add thermal mass to the heating system and use the daylight hours to use up as much of the PV electricity as possible to heat the home or its water supply. Those savings would then pass on to the gas bill, should the home be co-heated by gas. Use diversion load controllers to divert grid spillage to immersion heaters, this is a simple but effective way to use some of the PV power. Operate Air-to Air heat pumps to heat,cool or dehumidify properties, again with a COP of 3+ typically. Fridges, feezers will use a few hundred watts most of the time, especially during the warmer months.

If the home is setup to cleverly use all the power being produced by the PV system, it then doesn't matter when you wish to charge your EV, day or night, you're still getting the full benefit of the "free" PV electricity for that purpose, without a storage battery in sight (apart form the one in the car of course).

Every day I get messages saying, "yes, but my car isn't parked at home when I need it charged form my PV". It doesn't have to be, providing you have had your system properly designed in the first place as part of a complete energy package for your home. Today, it is still possible to alter most existing PV systems to more cleverly use the power they produce. This can involve some of the technologies mentioned, or can, in some cases involve battery storage, which has its place in some systems.

If your car isn't at home during the day, then it's at work I presume. Therefore, a discussion with your place of work to have PV charging bays installed there would get round that argument, yet this isn't what's happening in general. PV installed at a business is much less likely to spill power onto the grid, due to the much higher daytime demand of power on-site. Thus a PV car park, with charging bays, genuinely allows all PV power to be used to charge the cars of the employees who have switched to EV, or to power feet cars operated by the business (minus small system losses for the more astute among you).

There are a lot of conversations to be made between PV owners and their installers, EV owners and their work bosses, with the aim to have as many people genuinely operating their EVs from PV power.

Let's face it, the most efficient way to operate an EV is to charge it with power generated at the point of use from renewable sources. PV does this very well indeed, so please, have these discussions and get employers on-board now and persuade them to be leaders in this field, otherwise they will become followers at a later date...

It's up to you....
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