Miyakojima island goes 'smart' with solar, wind power

January 22, 2012

Staying in an "eco-house," a home built by the city to let the wind pass through and block the sunlight so that its inhabitants can go without air conditioning, offers an introduction to the energy conservation commitment in Miyakojima, an island 300 kilometers southwest of Okinawa's main island.

Even though it had rained, the temperature was still 25 degrees and humidity 91 percent after it stopped. And although it was winter, the home still felt strangely refreshing and comfortable inside.

It's all part of an expansive experiment under way on Miyakojima where the entire population of the coral reef-surrounded isle, numbering 55,000 people, is creating a "smart community."

Renewable energy generated by solar and wind power already accounts for up to 30 percent of the island's electricity. The community is now tasking itself with cutting carbon dioxide (CO2) emissions by 70 percent.

A blanket of solar panels cuts through the vast fields of sugar cane reaching skyward along the island's southern coast. The 22,000 panels, which make up the Mega Solar Experiment Study Facility, completed in October 2010 by Okinawa Electric Power Co., bathe in the tropical sunshine to generate up to 4 megawatts of power.

Two giant wind turbines tower over the grounds and three more stand on the northern part of the island.

Combined they produce a maximum of 4.2 MW of wind-generated power on the island. During peak demand in summer, Miyakojima and nearby islands consume about 50 MW of electricity. Winter demand is roughly half that, meaning that they are already relying on renewable energy for 30 percent of their power needs at the maximum.

Some critics say that since the weather has a major effect on solar and wind power, which come with big risks such as large-scale blackouts due to their relative instability compared to electricity generated with fossil fuels and nuclear power. Indeed, the electrical panels displaying power generation output in the Mega Solar Facility's administrative office drop to approximately 40 percent of the maximum level on cloudy days, and to less than 10 percent when it rains.

To compensate, the facility has a massive 4 MW storage battery system.

When solar and wind-powered generation drop off, the storage batteries pick up the slack by releasing their stores of electricity to maintain steady distribution throughout the island's power grid.

"I think our year-long trial project will sufficiently clear the conditions for making this technologically practical," Masayoshi Toguchi, the technical development group leader at Okinawa Electric Power, confidently declared.

Environmental awareness is high on Miyakojima, which is completely water and energy self-sufficient. In 2008, the city of Miyakojima adopted the "Declaration of Eco Island Miyakojima," which sets the major goal of cutting CO2 emissions in 2030 by 40 percent compared to 2003 levels, and by 70 percent in 2050.

To achieve this, cooperation from energy consumers in addition to efforts on the supply side will be essential. In October, the city hired Toshiba Corp. to formulate a way to manage how energy is used across the entire island. A four-year research project is now under way. On Kurimajima, an island of 88 households southwest of Miyakojima, a trial test is being run to provide all the electricity needed for daily living solely through solar power and storage batteries.

A number of initiatives are already getting started. MaxValu Miyako Minami, a supermarket in the central part of the island, has installed its own solar panels and wind power generation equipment, which provide 12 percent of the store's electricity. The supermarket also provides free electric vehicle (EV) charging with the high-speed charging station set up in the parking lot.

Power grid technology nearing practical level

A smart community employs an approach to urban development in order to use energy smartly and efficiently. Vital to its creation is an infrastructure that manages an optimal balance of the power needed. This is called a smart grid, which utilizes information technology.

Adding communication functions to a power grid and frequently measuring household electricity consumption with smart meters allows utilities to see the amount of power generated from natural energy sources such as solar and wind power, which constantly fluctuate.

A smart grid will also make it technologically possible for power companies to do more than just ask customers to conserve power according to changes in supply: they will be able to send signals to power control equipment in homes and office buildings to switch devices' operating modes as well as instruct storage batteries and EV batteries to charge or discharge. The technology will also open the way for utilities to introduce adjustable rate systems that, for example, would raise the rate charged to customers during hours of intense power consumption, thus making it easier to encourage people to help conserve energy.

Remaining issues to resolve include the creation of universal standards, but the technology is nearing practicality and companies are becoming actively involved. Toshiba, which has a department for overseeing smart community projects, will create a new organization in January to enhance its approach toward project growth.

The company is enthusiastic, having already taken orders for 20 projects worldwide and establishing a sales target of 900 billion yen ($11.7 billion) for four years from now, one-third of which will be generated with smart grids.

Some of the smart grid-related trials planned for the economy ministry's Demonstration of Next-Generation Energy and Social Systems project, of which smart house pilot programs form the central component, are already getting started. The project will organize a trial run of dynamic pricing, in which about 50 organizations and companies such as the city of Kitakyushu will participate. The project will allow power supply and demand to be seen in real time, which will be reflected in billing rates for power consumption.

(This article was written by Shu Nomura and Susumu Yoshida.)

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A blanket of Okinawa Electric Power Co. solar panels at the Mega Solar Experiment Study Facility. (Toshiyuki Takeya)

A blanket of Okinawa Electric Power Co. solar panels at the Mega Solar Experiment Study Facility. (Toshiyuki Takeya)

  • A blanket of Okinawa Electric Power Co. solar panels at the Mega Solar Experiment Study Facility. (Toshiyuki Takeya)
  • Some of the solar and wind power generated is sent to the storage battery system. (Toshiyuki Takeya)
  • An "eco-house" with a ventilated design. Opening up the entrance creates a drafty, yet roomy space.  Both houses are located in Miyakojima, Okinawa. (Toshiyuki Takeya)

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