Charging an electric car with the power from your own photovoltaic system (PV system) is a rewarding experience. After all, a PV system with an output of 5 kWp can supply up to 5000 kWh (kilowatt hours) of electricity per year. If your electric car has an energy consumption of 17 kWh/100 km, then you are driving almost 2,500 km per month emission-free. So charging your electric car with PV power not only takes the strain off your ecological conscience, but your wallet too.
Due to decreasing rates of remuneration for feeding power into the grid and increasing electricity costs, the private consumption of PV electricity is gaining in importance. Instead of selling on privately generated electricity at low prices (remuneration for new systems under the German Renewable Energy Sources Act stood at 12.3 cents/kWh in Sept. 2015), you should consume or temporarily store as much of this power as possible yourself. You can increase your own consumption for example by using PV power to charge your electric car and by implementing intelligent consumption regulators such as the smartfox Energy Manager. Today, the saving for every kilowatt hour you consume yourself is already up to 18 cents. This is because you do not need to draw any expensive power from the electricity grid (26-30 cents/kWh), or temporarily store the PV power you have generated in the electricity grid for higher costs.
When using PV power, the maximum charging power for your electric car depends on factors such as the size of your PV system and the consumption profile of other appliances in your household. The larger your PV system and the smaller the electricity consumption of your household appliances, the greater the maximum charging power available with PV electricity. With a system capacity of 5 kWp and domestic consumption of 1 kW, 3.7 kW will still be available for single-phase electric car charging at a charging station. There will also be 0.3 kW left over to be fed into the electricity grid.
There are two basic ways to connect your electric car to a PV system:
At present, the current flows by means of a uni-directional connection one way only: from the PV system to the charging station, and from there into your electric car. Using a charging management system such as the smartfox Energy Manager enables you to have your electric car prioritise power from your PV system, therefore increasing your own consumption. If the sun isn’t shining when you need to charge your electric car, then you can simply draw additional power from the grid at the touch of a button. So you remain independent and flexible at all times.
In the future, the current will not only flow into the electric car, but – by means of a bi-directional connection – it will also flow back from your electric car into your home or be fed into the electricity grid. The electric car will in this way take over the task of a battery storage unit. When more PV power is available than is required by the household, then your electric car is charged. If less PV power than you need is available (e.g. in the evening or during the night), the household is supplied with electricity from the car battery. In addition, the battery is capable of stabilising the electricity grid, by the car being connected to the balancing energy market as part of a swarm storage unit (Vehicle-to-Grid – clearly and simply explained in our video). However, bi-directional charging stations are still under development. To help drive the future forwards, The Mobility House is participating in extensive tests of bi-directional charging in its office’s underground car park – and is now brewing green coffee with the Nissan Leaf: “The Mobility House brews coffee using green electricity from an electric car“.
The demand for decentralised production of green electricity goes hand in hand with the rising popularity and expansion of electric mobility. The ideal case would be to charge your electric car with solar power from the roof of your house as this not only guarantees you to hit the road fully emissions-free but also might have a positive effect on your energy bill. Whilst household energy prices from the grid operators have increased by almost half within only the last 10 years (from an average of 19.46 c/kWh in 2006 to an average of 28.73 c/kWh in 2016), the feed-in remuneration for solar energy decreased to approx. 12 cents per kilowatt hour, according to the German Association of Energy and Water Industries (Bundesverband der Energie- und Wasserwirtschaft – BDEW). To accelerate the refinancing of your solar panels it might be an interesting option for you to increase self-consumption instead of supplying under-priced solar energy to the grid and redeeming it. To do so, you can run high energy-consuming household devices, e.g. washing machines or heat pumps and boilers, using your own solar energy. In the same way you can power the charging station for your electric car with energy from your PV installation.
