Daiwa House Industry Co Ltd announced that it will start selling houses equipped with lithium-ion (Li-ion) rechargeable batteries and photovoltaic (PV) cell modules in about the spring of 2011 in Japan.
By using PV cells to store electric power in rechargeable batteries during daylight hours, it is possible to drastically reduce the amount of CO2 emissions and light and fuel expenses. Also, the company plans to utilize the HEMS (home energy management system), which controls the power consumptions of home electric appliances and LED lighting equipment.
Daiwa House Industry is engaged in a project aimed to develop a residence that can eliminate CO2 emissions and light and fuel expenses by 2020. The new houses are the first products for the project and called "Sma x Eco House."
This time, Daiwa House Industry set up a house equipped with 6kWh of Li-ion rechargeable batteries and 5.1kWh of PV cells for field tests. Its total floor area is 254.86m2. According to a simulation by the company, the house can reduce CO2 emissions and light and fuel expenses by 65% and 102%, respectively, compared with normal residences that comply with the Japanese government's new standards for CO2 emissions and light and fuel expenses.
If the house used for the field tests is sold, it will be priced at about ¥54 million (approx US$606,061), Daiwa House Industry said. The price is about ¥20 million higher than that of the company's normal residences, which do not have the HEMS, etc.
As for the capacities of PV cells and Li-ion rechargeable batteries, Daiwa House Industry plans to optimize them through the field tests. The Li-ion rechargeable battery is manufactured by Eliiy Power Co Ltd, in which Daiwa House Industry has a stake. The battery consists of 48 large-size cells.
The PV cell module is provided by Sharp Corp. Daiwa House Industry determined the capacity of the Li-ion rechargeable batteries based on estimated electric power consumed by a family of four from morning to evening, it said.
In the Sma x Eco House, the HEMS plays an important role. For example, it controls the output of PV cells, the charging state of rechargeable batteries, the amount of power consumed in each room, air conditioners, LED lighting equipment, etc on a home server. For this purpose, Daiwa House Industry introduced "Residence API."
For the field tests, Residence API is installed in the iPhone so that it can be used to change the temperature setting of air conditioners and switch on and off LED lighting equipment. For the home server, Daiwa House Industry employed "OSGi," a framework standard for middleware and applications software that run on Java virtual machines. Those systems were constructed by Sorun Corp.
In the house built for the field tests, the home server and air conditioners are connected via a wired LAN. And Toshiba Corp's air conditioners are equipped with IP converters compatible with the "Echonet" standard.
All of the lighting equipment in the house uses LEDs provided by Kyocera Corp. And the LED lighting equipment is switched on and off by opening and closing the relay via the home server.
The LED lighting equipment is arranged so that it indirectly lights the rooms with soft light, Daiwa House Industry said. Shozo Toyohisa, a Japanese designer, arranged the lighting equipment. By alternately arraying warm white LEDs and white LEDs and controlling the voltages of the two types of LEDs respectively, the LED lighting equipment emits sunlight color light during daytime hours and silica lamp color light during nighttime hours.
Furthermore, Daiwa House Industry added a function to advise residents when to open the windows, etc by using the HEMS. The function encourages users to let fresh air in based on the difference between outdoor temperature and indoor temperature. By suggesting turning on air conditioners after that, the function can reduce the power consumptions of the air conditioners.