Hawaii confronts 'green' energy's bugaboo: batteries

Hawaii and California utilities are moving to add storage on their grids to accommodate 'green' energy and better match energy production and consumption. But storage is still expensive. 

Hawaii Electric Co. – no stranger to solar power – has a problem with the sun.

When it shines, so much energy from utility and home-based solar panels comes surging in that it can overload some circuits in the grid and, potentially, cause a power surge that damages home and office equipment. When the sun goes into hiding, the utility has to generate power from somewhere else. That’s why the utility is casting a net to find vendors that could supply it with the technology to store electricity.

The California Public Utility Commission has anticipated the problem and already requires the state's three incumbent utilities – PG&E Corp, San Diego Gas & Electric, and Southern California Edison – to collectively buy 1,325 megawatts (MW) of energy storage by 2020.

Storage is the behind-the-scenes bugaboo for “green” energy. Ideally, it would allow wind and solar developers to grow their markets, make grids more efficient, and eliminate the need to expand power production to cover peak loads. But it’s expensive. Until the price of batteries comes down dramatically, progress will be slow.

Some green energy advocates say the only problem is scale. Once advanced batteries are produced in sufficient quantities, they argue, the cost of manufacturing them will fall. Tesla chief executive Elon Musk, for example, said this past week that his $5 billion “gigafactory” could bring down the costs of advanced batteries by more than 30 percent. However, the plant at capacity would produce enough batteries for 500,000 electric cars a year, more than 10 times what Tesla sold in 2013. So, until Tesla sales skyrocket, one of the plans would be to use the excess batteries for green-energy storage.

At least 40 different storage technologies exist – but utilities’ demands are stringent. They’re trying to match the energy they produce with the energy their customers consume. That’s hard to do, given that industrial sites routinely implement new processes. Utilities often have to overbuild so they have capacity when demand peaks. If more storage could be developed, the grid could prevent blackouts with less excess capacity, keep wholesale prices of electricity from fluctuating wildly, and entice more green energy projects.

In the case of Hawaii Electric, which issued its requests for proposals last week, the storage needs are short term. It’s looking for 60 to 200 MW of storage capacity that would store electricity for 30 minutes, releasing the power during peak periods to ease congestion on the grid – or when the sky gets cloudy.

Many of today’s storage devices can inject about 15-45 minutes of power into the grid. Ultimate batteries may go for three to five hours, and run at 90 percent efficiency whereby little energy is lost during the production process. Other batteries can go for 6-10 hours, such as NGK Sodium Sulfur Battery. That duration is able to cover 98 percent of all outages, making it ideal for backup power.

Battery companies are already making a go of it in the utility business. With 130 employees, Pittsburgh-based Aquion Energy this year started commercial production of batteries that allow utilities to better manage their grids. It says it is selling its technology to California and Florida utilities that it cannot name because of confidentiality agreements.

“We are storing energy from solar panels and integrating renewables onto the grid,” says Ted Wiley, Aquion’s vice president of products and corporate strategy, in an interview. 

AES Energy Storage has 174 MW of battery-based controllable resources. Its products monitor the grid and then release stored energy either in response to wind variations or to help support unplanned outages. It is doing business in the United States and Chile.

Better batteries are coming, gradually. An acceleration in improvements in price and performance would be a boon.