What if the halfway is dead? Install a solar car roof for your electric car!

1) Prius Prime's solar roof

Toyota used the solar roof earlier on the Prius. It used a half-width roof to leave room for the skylight; the entire power is 60W. The actual construction of the two types of solar cells before and after, as shown in Figure 1.

Figure 1 60W solar roof of the previous generation Prius

The recently released Prius Prime (European and Japanese versions) has revolutionized solar panels. Its battery system is only 8.8Kwh (120kg, 351.5V). This solar panel consists of three parts in the whole system:

1) Solar roof module: As shown, the official maximum output is 180W

2) 12V NiMH battery: as the primary power source for solar power generation

3) DCDC variator: As shown in Figure 3, DCDC has high voltage output, divided into two connectors in two modes.

a. can be via the car charger to the battery system

b. It is also possible to directly enter the output bus and output part of the energy when the vehicle is driven.

Figure 2 Prius Prime system (electrification part)

As shown in Figure 2 below, the roof module has two pieces. According to the output of each piece in the literature 3, the maximum design is 94W.

Figure 3 Solar three-piece

In the early design considerations, mainly based on the selection of sample points, choose different time to monitor the actual solar power output efficiency; and the actual owner can monitor the top of the head through the display data of the entire large screen background, At the current moment of power, and throughout the life of the service, how much electricity is sent, corresponding to how much cruising range.

Figure 4 Practical efficiency and display interface of solar energy

In terms of current performance, the solar panels provide different power to the entire system under different seasons, different working days, and different power battery ratios. According to Reference 1, 20% of the 1kW in the literature can be used. Conversion, the rough estimate of the performance is about 10%, 0.5Kwh per day.

· Areas parked in different time periods will cause quite different

· There are about 5% differences in different seasonal factors, see Reference 4

Figure 5 Influencing factors of different Solar Panels

2) Is solar car feasible?

In fact, this problem can be combined with a domestic enterprise that makes solar cars. Similarly, we can see the engineers, give a modified car. Through the actual analysis of this case, we can get more questions and perspectives on this type. In this actual retrofit configuration, the average power generation situation is 2.09 kWh/day, which is equivalent to a cruising range of 14.6 km; the maximum power generation is 4.23 kWh/day, and the corresponding cruising range is approximately 29.6 km.

Figure 6 extends the solar cell to the body

The problem of electrical energy efficiency of the whole vehicle: The power generation efficiency of solar vehicles arranged at different locations is different. This problem exists objectively, so there will be a big difference between the ideal estimation and the actual test results at different time periods; As shown in Figure 6, different solar power modules need to be aggregated and bridged by cables and then collected into the DCDC converter. The semiconductor components need to be separated, and there will be wire impedance drop, semiconductor voltage drop and the entire converter. The conversion efficiency and other factors affect the overall power generation efficiency.

Figure 7 Differences in the position of the roof, front and back, and sides

Summary: Overall, the current roof with solar panels, in the PHEV with small battery pack (5 ~ 10kWh) this configuration can play some role.