Fronius Wattpilot Low-Cost Electric Car Charging Feature Guide

LOW-COST ELECTRIC CAR CHARGING WITH FRONIUS 

Feature Guide

1 GENERAL INFORMATION 

The integration and electrification of all energy sectors is a significant part of Fronius' vision of 24 hours of sun. Mobility is one of the most energy-intensive sectors. If we want to drive the energy revolution forward and pave the way for a sustainable future, it is essential that we move to electric vehicles, both for private transport and in the commercial sector. Fronius inverters allow the e-mobility sector to be easily integrated into photovoltaics. This paper will cover the various charging versions with Fronius inverters and explain the advantages. It will also provide an overview of the most common e-mobility charging solutions. 

1.1 The advantages of combining photovoltaics and e-mobility 

Photovoltaics and e-mobility are a perfect match. This section will explain the financial effects of combining PV and e-mobility as well as the impact on the electric vehicle's battery. 

1.1.1 Monetary benefits 

When photovoltaics was still in its infancy, it was common for 100% of the generated solar energy to be fed into the public grid because feed-in tariffs were high – up to 40 euro cents/kWh. In recent years, however, most countries have seen a trend towards self-consumption. 

It is now more cost-effective to use the self-generated energy from the PV system in your own home, as the feed-in tariffs are less than the cost of electricity. Therefore, the aim should always be to maximise self-consumption. Electric vehicles also require (a lot of) electrical energy. So you can benefit in a number of ways from using energy from your own PV system to charge your electric vehicle: 

/ Significant increase in the PV self-consumption rate 

/ Faster ROI of the photovoltaic system 

/ Cheapest form of energy for powering your electric vehicle 

/ Emission-free energy for your electric car 

/ Reduced dependence on the public grid 

An electric car typically consumes between 15 and 18 kWh per 100 km. On a conventional electricity tariff of around €0.3 per kWh (Germany), a 100 km trip in an electric car would therefore cost around five euros. However, if you were to 'fill up' your car with solar power alone, it would cost just one euro per 100 km. How did we arrive at one euro? A typical PV system involves an investment of around €1200 per kWp of installed power. We also assume a yield of 1000 kWh/kWp (Germany) and a useful life of at least 20 years. If you now calculate the price per kWh of self-generated PV energy, it comes to 6 cents per kWh. Therefore, if an electric car consumes 16kWh/100 km, it results in a cost of around one euro*. Meaning it is five times cheaper to charge your car with your own PV energy! 

Section two will take a detailed look at the different charging variants in monetary terms. 

*These calculations have been simplified. They do not include cost of capital, repairs, maintenance or module degradation. However, the system can also be operated for longer than 20 years.

1.1.2 Preserving the electric vehicle's battery 

The service life of the battery is an important factor when deciding to buy an electric car. This depends heavily on aspects such as the type of charging. Too much or too little strain on the battery can have a negative effect on its service life. For example, charging a battery with a capacity of 30 kWh with a power of 60 kW or more will charge it more quickly. But it will put an excessive amount of strain on the battery's cells and this can have a negative impact on the service life. You might then incorrectly assume that batteries should therefore be charged as slowly as possible. But this is not the right approach either. During the charging process, a higher voltage is applied to the cells than under normal condition. This degrades the battery cells during the charging process. The longer the charging process lasts, the stronger the aging effects are. Therefore, it is advisable to find a good middle ground with regard to charging power. 

This is another advantage of charging with surplus PV. Combined with a PV system, a vehicle is normally charged with a power between 4 and 8 kW. This charging power represents an optimum compromise, that is neither too fast nor too slow. Charging combined with a PV system therefore has a positive effect on the electric vehicle's battery life. 

1.2 Different charging options 

There are two ways of charging the battery in an electric vehicle. A distinction is made between alternating current (AC) and direct current (DC) technology. These have different charging plugs and charging infrastructure. There are charging standards from which three main plug types have developed in Europe: Type 2, CHAdeMO and CCS. 

1.2.1 Charging with alternating current (AC) 

Charging with alternating current is the most common way to charge an electric car. All electric cars are suitable for charging with alternating current. The vehicle's on-board battery charger converts the alternating current into direct current so that the battery can be charged. The AC charging power may vary depending on the type of charger installed. A VW e-up!, for example, charges with just 3.7 kW, whereas the latest Renault ZOE charges with up to 22 kW and therefore takes a lot less time to fully recharge. A charging box is needed for fuse protection and for communicating with the vehicle. This is a safe and convenient charging method, mainly used at home or in semi-public locations – such as company premises or car parks. Classic 230 V domestic sockets should not be used due to the long charging times and the issue of continuously high loads. Therefore, type 2 plugs, as shown below, are mainly used for charging with alternating current in the European Union:

1.2.2 Charging with direct current (DC) 

Some electric cars offer a faster alternative to AC charging: direct current or DC charging stations. Here the current is charged directly into the battery. These rapid charging stations enable high charging powers. The Nissan LEAF, for example permits up to 50 kW of charging power, while the Hyundai Ioniq allows up to 70 kW and the Tesla currently permits up to 250 kW. However, DC charging stations are considerably more expensive than AC charging stations and are therefore mainly used in public areas. In addition, rapid charging can have a negative effect on the battery's service life as described in section 1.1.2. 

1.3 Range and consumption 

The usable battery capacity of a vehicle varies significantly depending on the type and manufacturer. Small city cars offer capacities of 20 kWh, while touring saloons can store up to 120 kWh. Depending on the battery size and the vehicle consumption, the range can vary from 150 to 700 km. The majority of electric vehicles typically consume around 16 kWh per 100 km. This means, for example, that a vehicle with a 64 kWh battery can achieve a range of 400 km with a consumption of 16 kWh/100 km.

1.4 Limiting factors when charging electric vehicles 

The maximum achievable charging power for an electric vehicle basically depends on 4 factors: 

/ The supply cable (connection cable) used/the fuse protection for the building's power connection 

/ The mobile charging cable/charging box used 

/ The type 2 charging cable used (amperage coding) 

/ The on-board battery charger in the vehicle (1, 2, or 3-phase version, and maximum charging current) 

The weakest link in this chain always decides the actual charging power that can be achieved. When designing and installing a charging solution, all four factors must be taken into account.