Sphelar Cells Save on Silicon,
Capture Light From All Paths

Arealization is emerging that theearth’s sources of fossil fuels, foodand energy are exhaustible and insufficient to support the growing
global population. At the same time, many scientists warn about the threat of global warming,
the apparent consequence of widespread andlong-term burning of fossil fuels. Every day,newspaper articles describe environmentalproblems.
Meanwhile, society is not make full use ofnatural energy, especially the inexhaustible lightenergy from the sun. The need is urgent for living spaces that fully use natural energy. Like
modern people suffering from lifestyle-relateddiseases, the earth is also ailing. The cure is tochange the living space itself.

Sphelar Spherical Solar Cell
Recently, spherical solar cells have drawn
attention mainly because spherical solar cells,
which are produced directly from molten silicon, significantly reduce the waste of raw materials by eliminating “Kerf loss” caused byslicing silicon ingots into wafers in the conventional method. Silicon shortages in recentyears are stimulating this trend toward spherical solar cells, which use less silicon and therefor should eventually cost less than conventional cells.
However, lower cost is not the only benefit ofspherical solar cells over conventional cells. In
the natural world, light comes directly from thesun but also from reflected light and diffusedlight. Indoors, light comes from all directions.
Kyosemi Corp. has found that by making thelight-receiving surface spherical to take in lightfrom all directions, power generation capacities

Fig. 1: Technology roadmap for Kyosemi

26, JEI February 2007

can be increased.
People usually think oflight coming from one direction only. Therefore, people
assume that a spherical shape
has poor light-intercepting
efficiency compared with aplanar surface. Hence, somepeople conclude that a spherical shape is unsuitable for asolar cell. Kyosemi thinks
otherwise. Since 1994,
Kyosemi has devised spherical cell structures, has developed an original process on
the basis of this concept, andhas brought out several modules. In 2004, Kyosemi registered Sphelar as a trademark
for the company’s sphericalsolar cells. Sphelar cells are Fig. 2: Example of low-power-application module
small, measuring about 1mm
was displayed at the 2005 World Exposition,
to 2mm across, enabling the creation of modAichi, Japan.
ules in many different shapes, as well as transIn promoting Sphelar cells, Kyosemi focusesparent and flexible modules. In addition,
attention first on high-value-added small lowSphelar cells can be connected in series or in
power-consumption products that make theparallel. Applications to high-voltage modules
most of Sphelar’s characteristics for accommocan also be anticipated. Furthermore, Sphelar
dating transparent and flexible modules in a vacells are durable, and their material is recyriety of shapes and for accommodating designclable. With these characteristics, Sphelar cells
ers who want flexibility in selecting voltage
are promising tools for the construction of livand current (Fig. 2). With these characteristics,
ing space in the 21st century.
Sphelar is perfect for light and compact mobile
products and has a potential to become an alterKyosemi’s Strategy
native to disposable batteries. About 50 years
Currently, research and development ofago, transistors were introduced in the electronSphelar cells is at the final stage and the comics industry, taking the place of vacuum tubes
pany is gearing up for the standardization,and leading to the appearance of compact ramass production and automatic production ofdios. Sphelar cells may play a similar role asproducts (Fig. 1). However,transistors in transforming the market. Another
there are difficulties uniqueapplication for Sphelar cells is in small sensors.
to spherical cells in the proBy installing various sensors and by having
duction and assembly prothem communicate with one another, sensor
cesses. Sphelar cells curnetworks can be formed, making possible
rently cannot meet applicawidespread wireless monitoring of the environtions for supplying large
ment, including measurements of temperature,
power in terms of produchumidity, wind direction and environmentaltion capacity. Also, it is too
pollutants. Other applications for such sensors
early to take advantage of
could include factory automation and logistics.
the cost benefits of spheriMeanwhile, the Sphelar applications in biosencal solar cells.
sors offer the potential of enabling better health
However, Kyosemi has
care at home. Yet another application fordeveloped a commercial
Sphelar cells is as a tag that transmits informaapplication for Sphelartion in devices, for example, for securing thecells involving a wirelesssafety of school children on their way between
information terminal withschool and home, and for devices in the area ofout a conventional power
food safety. Each application will create a new
supply. This information
market. Furthermore, as Sphelar modules canterminal uses a Sphelar cell
capture light from all directions, it is possible
to receive both power andto drop sensors from the sky without regard toinformation through inthe direction of the sun. Such sensors might befrared light. The terminal
used for monitoring the climate. These areCopyright  2007 Dempa Publications, Inc.

Fig. 3: Sphelar panel window for BIPVFig. 4: Schematic drawing of Sphelar panel window

Kyosemi’s scenarios for the deployment ofSphelar in the area of low-power-consuming
applications.
Meanwhile, the potential role of Sphelar
cells in building construction is exciting. Manypeople are trying to design sustainable buildings that use renewable energy as much as possible by making the most of the light and heatof the sun including direct, reflected and dif-

fused light to obtain coolness,warmth and brightness. Thisis where transparent modules
using Sphelar cells display
their real ability. As Sphelar
cells are about 1mm in diameter and allow all kinds of arrangements, they can be completely integrated with building materials used for exteriors, including window materials, facades, eaves andopenings. Used as a transparent window material, Sphelar
cells, due to their sphericalshape, enables power generation no matter the position of
the sun, which changes by theminute depending on the timeand season. With these modules, conventional
discussion of efficiency, that is, the method to
divide output by the power of sunlight illuminated on the entire module, no longer makes
sense. Rather, the performance should be measured in terms of electricity generated per day
or annually. A prototype transparent panel ismade by connecting 10cm.sq. units (Fig.3).
Laminated glass with double-pane construction
is used (Fig. 4). By including an air layer inthe panel window, conduction of heat is reduced. Down the road, Kyosemi plans to accumulate basic data on the effect of the transmitted light on the brightness of a room, the effectof the panel window on blocking the heat of
the sunlight and suppressing increases in room
temperature in the summer, and the window’seffect on retaining room heat in the winter(Fig. 5). Naturally, when the Sphelar panel isused in windows, output power declines withincreasing transparency (decreasing cell density). To accommodate a variety of buildings inpractical applications, designs with enhancedaesthetic features for respective levels of transparency are necessary, although it depends onrequired generation capacities (Fig. 6). In de-Fig. 6: Variety of patterns of Sphelars in windowpanel

signing Sphelar patterns, consideration must begiven to the interior and exterior designs ofbuildings, as well as to views seen throughwindows. As the solar cell modules are integrated into building materials, their prices andquality assurance need to be handled as part ofthe building materials, not independently as
solar cell modules.
Lastly, at the point when the mass production system is fully in place, the ultimate application area will be as a supplier of large
amounts of power. There, the cost benefits ofSphelar spherical solar cells will be fully delivered. Efficiencies can be further gained by collecting light through inexpensive lenses.
Sphelar itself is structurally durable and recyclable. This feature of Sphelar will also be exploited. Through its Sphelar business, Kyosemi
hopes to contribute to the construction of a newliving space in the twenty-first century.
❑About This Article
The author, Kenichi Taira, is Chief Engineer, Microgravity
Utilization Laboratory, Kyosemi Corp.

Fig. 5: Output power of Sphelar panel window vs. transparency

Copyright  2007 Dempa Publications, Inc.

JEI February 2007, 27