Japanese group to trial electric cars fitted with ‘solar batteries’

17 Jul 2019

Nedo, Sharp and Toyota collaborate on photovoltaic car based on solar cell and battery combination; road testing, later this month.

A Japan-based collaboration of carmaker Toyota, electronics giant Sharp and research and development management organization Nedo is later this month, to commence public road trials of prototype electric vehicles equipped with high-efficiency solar batteries.

The initially-announced twin objectives of the research are to assess improvements in the cruising range and fuel efficiency of such a solar-powered vehicle.

To enable the trial, Sharp has modularised its high-efficiency solar battery cells, which offer a conversion efficiency of 34 per cent-plus. Development of these cells was carried out by a Nedo-led project and applications were envisaged for the power generation business to achieve a cost of ¥7 ($0.07) / kWh.

Toyota has installed such a solar panel on the roof, bonnet, tailgate and other parts of its Prius Plug-in Hybrid to produce a demonstration car for the planned trials. The solar battery cell is a film of about 0.03mm in thickness. This makes it possible to install it efficiently over the curved parts of the car, including the roof, bonnet and rear hatch.

Enhanced efficiency

By enhancing the efficiency of the solar battery panel and expanding its onboard area, Toyota has been able to achieve a rated generation output of around 860W, a figure around 4.8 times higher than that of the regular, production Prius Plug-in model (equipped with a solar charging system).

In addition to substantially boosting its power generation output, the demo car employs a system that charges the driving battery while the vehicle is parked, as well as when it’s being driven. This development is expected to lead to considerable improvements in electric-powered cruising range and fuel efficiency.

Toyota plans to conduct the trials in various driving conditions in Toyota City, Aichi Prefecture, Tokyo and other areas in Japan. Data, including the solar battery panel’s power generation and the amount the drive battery is charged, will be gathered and verified, and used in the development of an on-board solar recharging system. Toyota says it plans to share a selection of trial data results with NEDO and Sharp.

The PV-powered Vehicle Strategy Committee, sponsored by Nedo and others, will evaluate the benefits based on improvements in CO₂ emissions, reductions and convenience, such as the number of times a vehicle needs recharging. The goal is to contribute to the creation of what the partners are calling “a new solar battery panel market”, including for the transport sector, and to find new solutions for energy and environmental issues.

Background

In April 2016, Nedo established the PV-powered Vehicle Strategy Committee, which comprises members from industry and academia. With the goal of finding solutions to energy and environmental issues in the transport sector, the committee’s research focuses on solar power systems. Sharp and Toyota are active committee members.

The committee’s achievements thus far include estimates of the potential to achieve an output of 1kW in vehicles, in spite of the limited space available to install power systems, by using a solar battery module with a conversion efficiency of 30 per cent-plus, zero annual recharging (depending on usage patterns) and estimates of the benefits from a reduction in CO₂ emissions.