Six units of Steffes Corporation’s electric thermal storage will go into operation this week on Vinalhaven Island, Maine to test over the coming months what could be the future of renewable energy storage for windy states: distributed energy storage.

The technology will make it possible to utilize generated wind power at night by distributing and storing electricity in the form of stored heat.

Steffes Corporation and its distributor Thermal Energy Storage of Maine L.L.C. have provided the electric thermal storage units for this week's test of a decades-old electric heating technology married to smart grid technology. The goal is to utilize renewable energy instead of oil for heating. Wind power generated at night is stored as slow-release heat in very dense ceramic bricks, then released on demand to economically heat buildings.

Vinalhaven is one of the Fox Islands off Maine. Last summer, the Fox Islands Electricity Cooperative Inc. voted to build wind turbines for electricity and they now make their own renewable energy from three 1.5 MW wind turbines. However, like 80 percent of Maine, the island’s residents have until now been dependent on oil for home heating.

"It's a horrible situation for us to be in because, as we saw in 2008 when heating oil peaked at $4.71 a gallon, there isn't enough money available from either public or private sources, to make staying warm – for tens of thousands of Maine citizens – possible at prices like that,” said Sam Zaitlin, president of Thermal Energy Storage of Maine, which is working with Steffes, the cooperative and the Island Institute in Rockland to test the technology to bring energy-independence in heating, as well as electricity, to Vinalhaven Island.

The addition of smart grid technology to Steffes’ electric thermal heating units makes it possible to store renewable energy in home units that can monitor and regulate and store electricity as heat, and then slowly release that heat as needed over a 24-hour period.

Distributed electricity storage as heat brings a solution to storing and then utilizing cheaper night-time wind power as home heating, and will be good for the island's residents individually, saving them money on home heating, while also regulating wind on the grid.

It is also much better economically for the islanders because, as members of the Fox Islands Electricity Cooperative, they have been selling their wind energy to the mainland at comparatively low rates.

With little demand for electricity between midnight and dawn, they were paid as little as 4 cents per kilowatt hour for the wind power they exported. And considering the distance to the mainland, the cooperative was even incurring a 3 percent line loss. Developing a storage capability on the island itself was embraced as a better economic alternative to exporting power at low rates.

Thermal energy storage

Funds are becoming available nationwide under the Recovery Act for states to sponsor approved energy audits, weatherization and fuel switching to cleaner, more renewable forms of energy. Thermal energy storage is one of the technologies sponsored by Efficiency Maine, a statewide effort to promote more efficient use of electricity.

This new and exciting smart grid technology enables remote control of storage heaters based on wind generator output, grid demand and the spot price of power, which fluctuates with the demand on the grid.

Thermal Energy Storage of Maine is working with Steffes, which is making the units to replace oil heaters in six of the island's residents' homes with wind-powered electric heaters that can store and safely hold heat in extremely dense ceramic bricks, then and slowly release this heat on demand for up to 24 hours.

Steffes’ technology has been around for decades. There are thousands of units like this in operation in Europe, and many in other states. But only now, as more excess renewable electricity is created at off-peak hours, has the need arisen to store that electricity somewhere, creating a new business opportunity for a new green technology.

Steffes’ electric thermal storage units work this way: electricity heats coils that radiate heat to extremely dense ceramic bricks, which are surrounded by a space-age insulation that keeps the exterior from heating above 160ºF.

As heat is removed throughout the 24-hour period, the bricks shed heat and the exterior eventually cools as well. They work no differently than other home heating systems: you set the temperature at whatever level you desire and a fan circulates air over the bricks at a variable speed so that a steady temperature is maintained.

Being charged with electricity from a smart grid controller does nothing to change the amount of heat being discharged into a space because the homeowner chooses that temperature.

Until recently, nobody has thought to use them specifically as a distributed energy storage option for wind power by adding sensors to absorb excess grid power. When there is more wind electricity on the grid than can be used, it would be dispatched to these units, which provide distributed storage for electricity for use as heat later.

Once they reach their maximum core temperature, they will not charge anymore. At that point, the heaters controls will not accept more power from the grid. Inside, the electric thermal storage units can transform and store enough electricity to heat each unit up to 1,200ºF, storing 24 hours worth of heat.

Commercial-sized units can heat up to 1,600ºF. Of course, the homeowner does not want a house that is suddenly hot at 2 a.m. while the wind is howling outside, and that does not happen. The exterior of each unit never gets above 160ºF, just like an old-fashioned radiator.

Smarter grid

Demand for electricity is constantly monitored the on the grid compared with generation output. Power plants have to generate more, or less power, at any time to keep things in balance. Sometimes wind farms have to be actually turned off at night because there is nobody using that electricity.

The test for the six units over the coming months will determine whether the technology is reliably able to divert excess wind power to the storage units. Using that extra wind power on the island to heat homes is the first step.

On a large scale, this would enable wind power to be utilized not only during off-peak hours, but also to become a flexible option for sudden needs for storage of excess power that can develop temporarily at any time during the day as well.

A pilot program sponsored by ISO-New England Inc., the nonprofit regional transmission organization serving Maine, Massachusetts, New Hampshire, Rhode Island and Vermont, will determine the feasibility of using remote-controlled thermal storage heaters to provide this regulation service that is currently only provided by generators. This could also provide the "sink" needed to absorb power on Maine's grid. The state aims to add 3,000 MW of wind by 2020 to meet the requirements of its renewable energy standards.

"This smart grid technology will allow ‘load-in’ in the form of remote controlled electric thermal storage units to follow generation," said Mr. Zaitlin of Thermal Energy Storage of Maine.

"To use an automotive analogy: going down the highway at a stead y 60 miles per hour is more fuel efficient than ramping up to 70 mph, down to 62, mph up to 68 mph, etc. The same holds true for power plants. Now imagine you've got installed, say, 25 MW of storage capacity in x number of [electric thermal storage] units," he explained.

"It's a winter night in Maine when the wind is blowing hard and it's very cold outside, but the grid doesn't need the extra 17 MW of power that the turbines could produce," Mr. Zaitlin remarked.

He continued: "What we're talking about here is the ability to sense the capacity available in those heaters and automatically dispatch the power to them without curtailing the wind generation. So, we'd be matching the load to the generation that's out there".

With distributed storage, any community could simply add more storage units as needed. As local renewable energy resources grow, the number of these thermal energy storage units in homes and businesses could also multiply in tandem, ensuring a good match between dispatchable power and the needs of consumers.

In addition to being scalable, distributed individual units demonstrate an inexpensive solution for energy storage when compared with centralized storage for renewable energy, such as pumped hydro or compressed air. If it works, it would have a wide national application.

The Obama administration is funding the development of many storage technologies for renewable energy in the Recovery Act. California legislators recently proposed a bill that will require utilities to have stored energy on standby as a percentage of peak demand at daytime.

Among the 29 states that have a renewable energy standard, including Maine, a storage requirement could well become the rule, as more renewable energy is added to the grid.