March 5, 2021

Here comes the sun

An EV is only as sustainable as the electricity used to charge it. Therefore, net zero mobility not only requires the electrification of cars but also the widespread availability of green energy. Sourcing this green energy locally from PV systems also reduces the strain on the public grid and lowers costs. More sustainable, more grid-friendly, less costly: Sounds like a win-win-win situation. So how can this work?


Connecting PV system and charging points

Generally, some sort of connection between the PV system and the charging infrastructure is required to enable PV-charging. This connection can be established by two means:

  • Integrated – Either the inverter of the PV system or the charging station feature an energy management system to handle surplus PV production.
  • External – A separate controller monitors and manages energy flows in the system.

Dealing with uncertainty

PV production is characterized by high levels of uncertainty. A single cloud, for example, may reduce PV production to almost zero for a brief period of time before it jumps back up. Most EVs, however, require a minimum power of 6 Ampere per phase to charge. Therefore, it is not possible to simply charge any surplus production into connected EVs. To solve this conflict most systems work with a threshold. Once the PV surplus surpasses this threshold, charging starts. If the surplus drops below this threshold again charging is continued for a given period of time to accommodate brief drops in production.

Striking a balance between mobility and sustainability

Simply speaking there is a conflict between mobility and sustainability. If I optimize for sustainability, charging is only possible when there is a sufficient PV surplus. Thus, charging could be delayed for days if there is no surplus. If I optimize for mobility, on the other hand, I charge as quickly as possible – even if no solar power is available. The best balance depends on the user’s individual preferences. Therefore, our solutions put the user in charge and offer three different charging options:

  • Pure PV charging – Charging only takes place in case the PV surplus is sufficient.
  • Programme charging – The user enters a desired range and time of departure. The energy management attempts to charge as much as possible from solar power. If this does not suffice to meet the range in time, additional power sources are utilized.
  • Minimum charging – The user sets a minimum range. This range is charged as fast as possible. Once the range is reached, charging is only continued if surplus solar power is available.

Not just good for the environment

There is also a financial aspect. As smartEn pointed out in a recent report, financial incentives are still the key driver of prosumers. Luckily, the business case for PV charging is also quite convincing. As the subsidies for the feed-in of renewable energy is phased out in Germany and electricity prices soar, the incentive to increase self sufficiency is becoming bigger and bigger. Moreover, legislators are increasingly removing regulatory barriers to promote renewable energies. The new renewable energy act introduced at the beginning of 2021 in Germany, for example, now exempts PV systems up to 30 kWp from the renewable energy surcharge – up from 10 kWp. This makes solar power more appealing to prosumers with higher energy consumption.

Enormous potential

Solar can make a tremendous contribution to sustainable mobility. The German E-Mobility Association estimates that around 90% of charging procedures take place at work or at home. Thus, the availability of carbon-neutral electricity at work and at home can make a tremendous contribution to more climate-friendly mobility. Additionally, the looser time constraints and lower volumes charging at home or at work provide the flexibility needed to accommodate the uncertain nature of renewable energies without compromising on mobility.

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