Japanese Model of Energy Efficient Buildings

Solar Photovoltaic Energy in Buildings


Japanese housing manufacturers characterise their industrialised houses enhancing their sales with green features integrated into their products in response to the society's increasing demand for the environment-friendliness. Since 1994, the Japanese government had implemented a series of residential PV incentive program until the end of 2005. Today, the housing manufacturers tend to install a PV system as a standard feature rather than merely an option and particularly, the roof of the industrialised housing is well furnished with the PV panels instead of traditional roof shingles or clay tiles, which are called Kawara. Sekisui Chemical uses 5 ft. x 3 ft. (152.4 cm x 91.4 cm) 205-watt crystalline custom-framed modules manufactured by Sharp. The typical size of their building integrated PV systems is 4.2 kW and generates 4,200 kWh per year in Nagoya. Misawa Homes uses multicrystalline modules from a number of manufacturers, e.g. MSK, Kobe Steel and BP-Solar. Sanyo uses their 190-watt high efficiency HIT modules (half c-Si and half a- Si) that are produced in-house; thus, the use of its own PV modules may make the production of PV solar housing more efficient. PanaHome uses crystalline Kyocera PV modules, which typical size of system is 3 kW, which is also being applied to their PV solar community developments. Panahome offers a 10 year-warranty on the PV system (modules and inverter) like other PV housing competitors in Japan and a 25 year-warranty on modules alone.

Net metering and time zone contract

Japanese housing manufacturers mostly locate the solar photovoltaic (PV) power generating system on the rooftop, either tilted or flat. The manufacturers often recommend an active use of all electric homes equipped with PV systems that benefit from the net metering and the time zone contract which are already being put in effect in Japan. Users can sell the surplus electricity generated by PV systems to an electric power company of the region. Based on the time zone contract, Japanese power companies buy the surplus electricity in unit of kWh from users at a higher price estimated at approx. 26 JPY/kWh ($0.25 CAD/kWh) in the day time and sell electricity to users at approx. 6 JPY/kWh ($0.06 CAD/kWh) at night.

Costs

Sekisui Chemical Co. is successfully producing "Net Zero Utility Cost Housing"; in which the users can enjoy the economical benefit from the installation of an induction heating (IH) cooking heater, CO2 heat pump (Eco-Cute) and a PV system. The cost of the 1 kW PV system is estimated at ¥ 490 000 (CAD$ 4 760). The payback period is considered to be 16 years where actual design life is about 30 years or more. In Japan, the average size of a PV system is 3.8 kW.

Sekisui Chemical claims that the cost of their rooftop PV system is 20 to 30% lower than those of other competitors in Japan, because this housing manufacturer is able to negotiate lower PV components costs through large PV purchases with Sharp (PV manufacturer). The installation cost of a PV roof system that is installed after construction of a house, is usually 40 to 50% of the total rooftop PV system cost. However, Sekisui Chemical can reduce the cost to only 20% because of their in-factory completion. The company explains that PV modules are installed inside the factory before the shipment. Sekisui Chemical Company produces about 4 500 new houses equipped with a PV system annually: about 1/3 of their customers select a house equipped with a PV system, a relatively higher ratio compared with 1 to 2% of the national average in Japan. This may indicate that the Japanese housing manufacturers’ cost-performance marketing strategy1 is effective in increasing the sales of PV solar homes.

Sanyo is manufacturing HIT PV panels, a hybrid technology using a blend of amorphous and crystalline silicon: their PV performances are claimed to be 20 to 30% above their competitors. Sanyo Homes benefit from this Sanyo subsidiary.



1 Japanese housing manufacturers attempt to educate their clients to appreciate the distinguishing features of their high-cost and high-performance (i.e. high "cost-performance") housing, in which a wide variety of amenities are installed as standard equipment rather than options.

Building integration approaches

Most manufacturers offer a variety of PV panel dimensions which are usually integrated on South facing sloping roofs. Sekisui Chemical installs Sharp 205-watt modules that are fixed to tailored black frames and sealed to the roofing by making use of a "quick connect" device. Misawa also designs roofs that are entirely composed of PV panels and occasionally, openable windows are seamlessly integrated into the PV rooftop.