By energy biz 

The race to deliver residential solar energy storage has yet another entrant.

A Japanese maker of grid-friendly, residential solar-plus-storage systems and a municipally owned Canadian electric utility have embarked on a trial that will allow customers to use the power the systems generate at any time.

Osaka, Japan-based Tabuchi Electric Co. Ltd. has installed its systems at the homes of two Oshawa Power and Utilities Corp. customers, kicking off a test program that will see them installed at about 30 residences in the utility's Ontario service territory. The test marks the first North American deployment of Tabuchi's systems.

An increasing number of solar-generation projects are incorporating storage components, but home-based solar-plus-storage is still extremely cutting-edge. Nonetheless, Tabuchi has competitors, including San Mateo, Calif.-based SolarCity Corp., whose home solar-plus-storage systems include Palo Alto, Calif.-based Tesla Motors Inc.'s Powerwall home batteries. (Elon Musk, Tesla's CEO, is the chairman of SolarCity, which he co-founded with his cousins.) And while the market for home solar-plus-storage systems isn't expected to grow as rapidly as the market for their commercial counterparts, it's still expected to expand considerably in the next few years.  

Like similar systems, Tabuchi's contain batteries, inverters and other components. They allow customers to use electricity from their rooftop solar units to charge the batteries and to control how the batteries discharge power. 

While the idea is to let customers store solar energy onsite and use it at any time, optimal use of Tabuchi's systems enable customers to take part in time-of-use or demand-response programs. Customers can also use the systems to power their homes when their electric service is out, but they'll have to watch their electrical usage during longer outages.

"If the grid goes down for a week, you can definitely function, but if you're running blow dryers and other things that use a lot of electricity, then you're going to have a hard time doing that," said Daniel Hill, a director of sales and marketing with Tabuchi.

The systems also can be monitored and managed remotely through their owners' mobile devices. And they can be aggregated and managed by utilities to act as a large virtual battery.

Beyond the test in Canada, Hill said Tabuchi is working on a couple of installations in California, and is getting calls from all over the country.

Tabuchi is a founding member of the Distributed Energy Resources Council of Hawaii, the first association formed in the U.S. to represent behind-the-meter technology and distributed resources. As such, Hawaii would seem to be a natural market for its systems. It might also help that the state's Public Utilities Commission stopped allowing residents to sign up for net energy metering in October, replacing it with several programs, including one that allows customers to power their homes with their rooftop solar systems and export small amounts of power to the grid.

Like Tabuchi, Oshawa Power is thinking beyond Ontario. Although it's owned by a municipality, the company is structured like an investor-owned utility with a holding company and three subsidiaries, including Oshawa PUC Networks Inc., which distributes electricity to nearly 60,000 customers in Oshawa.

Atul Mahajan, Oshawa Power's CEO, said the company plans to test Tabuchi's systems over a year and half, not just to confirm their technical viability, but also to investigate possible business models for them and see where deploying them would make most sense.

Solar-plus-storage systems presently aren't economically viable in Ontario, Mahajan said, although a combination of incentives and features they could add to the grid could make them so.

"I'm encouraging technology providers to get in contact with us because what I want to do is not just solar and storage," Mahajan said. "I also want to look at if I can remotely manage this storage that I will deploy at customer premises and start selling services back to the grid."

 Remotely managed and aggregated, solar-plus-storage systems could act like larger storage systems and provide power when needed not only to meet demand, but for voltage or frequency regulation.

In small groups, Mahajan said, they could be used to provide electricity to remote locations that get lots of sun, such as parts of Africa.

 "This would be a great game-changing technology with some modifications," he said.