Toyota, together with NEDO and Sharp, is conducting an interesting research project on a plug-in electric car, equipped with a solar charging system.

The idea is to assess how much power and energy can be supplied using high-efficiency photovoltaic cells, and how it corresponds to economic viability.

The Japanese manufacturer decided to use Sharp's triple-junction (indium gallium phosphide (InGaP), gallium arsenide (GaAs), and indium gallium arsenide (InGaAs)) solar battery cells in the form of a thin film (about 0.03 mm in thickness) with a conversion efficiency of up to 34%.

Covering the roof, hood, rear hatch door and rear hatch door garnish of the Toyota Prius Prime, allows for a potential power output (on sunny day) of 860 W. It's a lot and in theory could be enough to recharge the 8.8 kWh battery, which offers 25 miles (40 km) of EPA range.

Currently, the Prius Prime (aka Prius Plug-In or PHV) can be equipped with a 160 W solar panel (efficiency of 22.5%), but just for auxiliary purposes. The new 860 W system is designed to charge the traction battery while parking or driving.

Public road trials to begin in late July 2019.

Toyota plans to conduct the trials under various driving conditions in Toyota City, Aichi Prefecture, Tokyo, and other areas. Various data, including the power generation output of the solar battery panel and the amount the drive battery is charged, will be obtained and verified, and then used in the development of an onboard solar recharging system. Toyota plans to share a selection of trial data results with NEDO and Sharp. The PV-powered Vehicle Strategy Committee*5 (PV: photovoltaic), sponsored by NEDO and other entities will evaluate the benefits based on improvements in CO2 emissions reductions and convenience, such as the number of times a vehicle requires recharging. The goal is to contribute to the creation of a new solar battery panel market, including the transport sector, and find solutions for energy and environmental issues. Table 1: Performance comparison of the commercial and demo model Prius PHV Performance items Vehicle Prius PHV

(Solar charging system) Demo car Solar battery cell conversion efficiency 22.5% 34%-plus Rated power generation output 180 W Approx. 860 W Maximum charge to the driving battery while the vehicle is parked (per day)* BEV-mode cruising range equivalent to 6.1 km BEV-mode cruising range equivalent to 44.5 km Maximum charge and power supply to the drivng and auxiliary battery while the vehicle is being driven (per day)* Supplies power only to auxiliary battery, which powers the car navigation system, etc. BEV-mode cruising range equivalent to 56.3 km * Maximum amount of charge generated by the solar charging system while the vehicle is parked or being driven, converted into travelling distance according to the JC08 Japan test cycle. Calculated based on the Japan Photovoltaic Energy Association Labeling Guidelines (FY2016), taking into account the various losses incurred in onboard systems. Solar radiation amount calculated based on the daily data of the average year between 1990 and 2009 in the Nagoya district (source: NEDO).

Toyota Prius PHV demo solar car:

Gallery: Toyota Prius PHV solar demo car