A Japanese research group conducted a verification test to charge a Li-ion secondary battery module with DC power generated by solar cells and supply it to home appliances without AC conversion.
The experiment was administered by Tohoku University's Graduate School of Environmental Studies, NEC Tokin Corp, Sekisui House Ltd and Sumitomo Corp. The university announced the news Dec 17, 2008.
This verification test was part of the Development Project of Energy-saving Technologies for Weak Energy Storage Type Eco House, a program conducted by Japan's Ministry of the Environment to develop technologies for preventing global warming.
Existing home-use solar power systems convert generated DC power into AC using a power conditioner and supply it to homes. However, because many home appliances convert AC into DC via an AC adapter, power generated by solar cells is converted twice, from DC to AC first and from AC to DC next. As a result, even with a conversion efficiency as high as 90%, about 20% of the generated power is wasted due to the double conversion process.
On the other hand, the new system can boost use efficiency because it directly supplies generated power without converting it, Tohoku University said. According to its estimates, using 1kW-equivalent solar cell panels and making home appliances support DC supply, the amount of CO2 emissions generated by a typical household over a period of four hours can be slashed by about 40%.
The graduate school is planning to complete a wooden laboratory building that employs the DC power supply system in March 2010. It will also address the collection and reuse of weak energy as a new project from now.
Specifically, the graduate school aims to cut CO2 emissions by charging Li-ion secondary batteries with hydroelectricity generated by a waterwheel set in the drain in the bathroom, by a light breeze that blows through a room and by a man riding on a fitness bike.
An open experiment of the system announced this time will take place at Tohoku University's Graduate School of Environmental Studies at 11 am Dec 26, 2008.
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