December 09, 2004
Photocapacitor Combines Photovoltaic Cell And Battery

Some Japanese scientists have developed a combined photovoltaic solar cell and battery for mobile applications.

Scientists in Japan have made the first device that can convert solar energy into electricity and then store the resulting electric charge. The "photocapacitor" designed by Tsutomu Miyasaka and Takurou Murakami at Toin University in Yokohama could be used to power mobile phones and other hand-held devices (Appl. Phys. Lett. 85 3932).

The cells can be arranged in series to produce 12 volts. (same article here)

The cells can also be connected to form larger, more powerful cells. Conventional capacitors that are charged using electricity can produce a voltage that is no greater than the input, or charging voltage, of one of the cells in a connected series. In contrast, the photocapacitor, like conventional batteries, can produce voltage equivalent to the collective input of photocapacitors connected in series. The researchers' prototype produces 0.7 volts. Connecting 18 cells would yield 12 volts, which is the output of a car battery, said Miyasaka.

The thickness of the photocapacitor depends on the thickness of the electrodes, and could be made narrower than one millimeter, said Miyasaka.

The scientists expect to make these cells practical to use within just 2 years. They are working on making the cells into a flexible plastic material.

If this stuff turns out to be cheap to make then imagine applying it as a coating to a hybrid car to allow car batteries to recharge while parked.

Update: Miyasaka's claims above about moving the "photocapacitor" technology to market should be taken seriously because he leads a Japanese company that develops photovoltaic cell technology.

Peccell Technologies, Inc. (Peccell), a developer of a film-type dye-sensitized solar cells (DSC), has achieved a high voltage of over 4V - equivalent to that of a lithium ion battery - under illumination. The electrode of the DSC is made of titanium oxide paste, which is based on fine particles of titanium oxide supplied by Shoa Denko KK (SDK). The paste is applicable to both film-type DSCs for portable applications and conventional glass-substrate DSCs.

Peccell, based in Yokohama City and led by Prof. Tsutomu Miyasaka, Department of Biomedical Engineering, Faculty of Engineering, Toin University of Yokohama, was established in March 2004 for the development of DSC-related technologies.

Share |      Randall Parker, 2004 December 09 12:24 PM  Energy Solar

Dave said at December 14, 2004 6:13 PM:

Very interesting, but leaves me with a few questions: What is the storage capacity of these? Efficiency? Cost may be low since they're trying to use plastic, but who knows?

Why would you use them on a car? It's already got a battery.

dan said at June 20, 2005 11:22 AM:

The bottle neck for electric vehicles has long been the ability to store
power. This could be quite a breakthru if it pans out. Vehicles are usually
driven for short periods then parked for long periods. Plenty of time for recharge
between trips. Rose electronics is starting production on solar cells that convert up
to 55% of sunlight to electicity. Have a little vision.

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