The system, which combines solar cells and storage batteries to generate electricity had some innovative features.
The consumer electronics maker aims to sell the system for less than one-tenth the 2-3 million yen ($18,100-27,200) charged for comparable home-use systems currently available in Japan, by designing it to supply power only for lighting equipment, radios and electric fans – items it regards as the most basic necessities for off-grid users.
The backbone of the solar system is lead-free lithium-ion batteries capable of efficiently storing power generated by solar cells during the day, making up for the fact they cannot produce electricity at night or when sunlight is obscured due to bad weather.
In April, Sharp invested in Eliiy Power Co., which developed the lithium-ion battery, and created the photovoltaic power system jointly with the start-up, which originated at Keio University, Japan.
Recalling the days when he first started contacting Eliiy Power last spring, Ota Kenji, Sharp’s senior executive managing officer, said, “It took a full decade for us to ultimately find the technology.”
While many lithium-ion battery makers focus on developing large-capacity devices suited for powering automobiles, Ota said, “we finally hit upon the ideal technology for our company, which is capable of achieving large capacities and low prices.”
Sharp is confident that it can halve production costs for solar cells by the end of 2010 by using thin-film solar cells made of layers of silicon membranes formed on glass substrates, significantly reducing the consumption of silicon, prices of which have been soaring.
If Eliiy Power succeeds in mass-producing the batteries and pushing down their prices, this would make it possible to promote the use of solar power systems in America as well.
At a symposium in mid-July in Osaka, Sharp Chairman Katsuhiko Machida called the new system “a technological breakthrough….to bring the concept of an innovative eco-house into reality to meet the global initiative of halving greenhouse-gas emissions by 2050.”
What he meant by “breakthrough” is the DC Eco-House, which the company envisions as an energy-efficient house in which appliances are powered by direct current, which flows in one direction only.
This type of current is the centerpiece of the concept of a solar power system based on lithium-ion batteries.
The eco-house will be designed to use direct current produced by solar cells to power home appliances as a way of reducing power loss.
The electricity distribution infrastructure currently available, such as power transmission lines, are mostly compatible with alternating current, which repeatedly changes its direction or strength at regular intervals.
Typically, a web of transmission lines sends electricity from large power plants to households. During the process, however, the electricity is reduced by several percent due to resistance in the electric cables.
Electricity loss also occurs when AC is converted into DC when flowing in home appliance circuits.
Avoiding this power loss is the main gist of Sharp’s DC Eco-House concept. Given that AC is the dominant current, this idea may come a surprise to some.
But the idea could be a possible solution to the inevitable issue of how to promote applications of solar cells.
What really worries domestic power utilities is the growing tendency toward so-called reverse power flow, in which operators of solar power systems sell extra electricity generated in the daytime to electric power firms.
They are concerned that if the reverse power flow increases from the present almost 1% of their combined power output, this may threaten the stability of the power distribution system because of its vulnerability to weather conditions.
While the solar cell market is growing at a rate of 40% a year, mainly in Europe, cell producers are likely to see their growth eventually reach its limit if they continue to rely on demand related to the reverse power flow.
If solar power systems that combine solar cells and batteries for steady power supply – such as the kind developed by Sharp – come to be used more widely, it could help accelerate the spread of solar systems among households while securing stability in the electricity distribution infrastructure.
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