**1. Introduction**

Electric vehicles (EVs) have several advantages over conventional fossil fuel-powered vehicles such as zero tailpipe emissions, higher tank-to-wheel efficiency, low noise, and full torque at zero speed. With the increased use of electric vehicles in the form of e-bikes, electric cars, and electric buses, there is increased emphasis to make sure that the electricity used to charge the EVs are sustainable as well [1,2]. As shown in Figure 1, the average emission from electricity production for various European countries shows a wide variation of 13–819 g of CO2 equivalent per kWh based on the electricity generation mix in 2016 [3]. The European Union wide average is 296 g/kWh, which is primarily driven by the 43% share of fossil fuels in the gross electricity generation. Assuming a modest energy efficiency of an electric car to be 5 km/kWh, the CO2 emission of 13–819 g/kWh translates to a 2.6–163 g/km. Therefore, to make EVs truly sustainable, it is essential to charge EVs from sustainable sources of electricity, such as wind and solar energy [4–7].

Using solar energy for charging EVs is attractive due to the possibility of distributed photovoltaic (PV) generation in locations close to where EVs are parked. Specifically, charging electric vehicles from PV panels at workplaces has significant potential for the future due to several reasons.


**Figure 1.** CO2 emission from electricity production for selected European countries for 2016, in g CO2 equivalent/kWh.

Concurrently, the disadvantage of charging EVs at the workplace using solar energy is the low solar generation in winter months. Secondly, there is a lack of charging demand on the weekends for workplaces that have a weekday working week.

#### *1.1. Electric Bikes and Electric Scooters*

Electric bikes and electric scooters provide a convenient means of intra-city commute with a multitude of benefits such as door-to-door connectivity, low (indirect) emissions, reduced traffic, and parking congestion and a fraction of the energy usage of an electric car [11]. In 2016, around 30% of the 928,000 bikes sold in the Netherlands were e-bikes [12]. An e-bike can travel up to 25 km/h using a motor of up to 250 W (up to 1000 W for high-speed e-bikes) and uses a 12 V–48 V battery with an energy capacity of 0.2–1 kWh. Electric mopeds (including speed pedelec), on the other hand, can go up to 45 km/h using a motor of 1–4 kW and typically uses a 48 V battery of 1–5 kWh. Furthermore, e-bikes have an extremely low energy consumption in the range of 5–15 Wh/km depending on the drivetrain efficiency, riding behaviour, tire characteristics, and the combined weight of the bike and rider. This is much lower than the 150–200 Wh/km energy consumption of an electric car.

By providing a charging facility at the workplaces and powering it with solar energy, e-bikes can be made into a fully sustainable means of daily commute [13,14]. The focus of this paper is on the development of a charging station to sustainably charge e-bikes at the workplace using solar energy. The charge station is shown in Figure 2 and provides three modes of charging: AC, DC, and wireless charging, respectively.
