Batteries put to test in PV plan

Hawaiian Electric Co. and the Hawaii Natural Energy Institute are launching a project in a West Oahu neighborhood to see whether battery technology can be effectively used to open the utility’s grid to greater amounts of solar power produced by rooftop photovoltaic panels.

The project, in a neighborhood with one of the island’s highest concentrations of PV panels, is among three ventures being undertaken by HECO and HNEI statewide, investigating how battery technology can be used to overcome limits on the amount of intermittent renewable energy the state’s electric utilities can accept.

One of the biggest challenges facing the HECO companies and the Kauai Island Utility Cooperative is the ability to absorb increasing amounts of solar energy being generated by an unprecedented number of rooftop PV systems.

The solar boom is raising grid stability issues for the utilities because each PV system is essentially a miniature power plant that puts out varying amounts of electricity over which the utilities have little control. The problem is exacerbated as the percentage of solar power generation in any given neighborhood exceeds thresholds, producing big swings in voltage and current frequency that have the potential to damage electrical appliances and injure utility workers.

Homeowners in some areas highly saturated with PV panels have had to put their projects on hold while HECO and its subsidiary utilities figure out what technical steps they need to take to accommodate more solar energy. Others have been told that they will have to pay thousands of dollars to cover the cost of equipment upgrades before they can proceed with their PV installations.

The project in West Oahu features a 1-megawatt lithium-ion battery that will be installed between HECO’s Campbell Industrial Park substation and the distribution circuit that serves a variety of utility customers in the surrounding area. The circuit is highly saturated, with more than 3 megawatts of installed PV capacity, or enough power to serve the needs of 750 homes.

HECO’s experience with battery storage to date primarily has been with systems installed by developers at utility-scale wind and solar energy projects to smooth out fluctuations in power frequency at the transmission level.

The West Oahu project, by contrast, is specifically designed to gather information on how battery technology can be used to keep voltages constant at the circuit level in neighborhoods with high levels of PV penetration.

"It’s going in on a line with a substantial amount of PV and industrial load. We’ll be doing some combination of smoothing out the power on that line and also providing voltage support," said Richard Rocheleau, HNEI director.

The battery will act as a buffer on the circuit, using control algorithms to release power when output from PV panels drops, and absorbing power when the solar power spikes.

The battery systems used in all three projects are manufactured by Nevada-based Altair Nanotechnologies Inc., a publicly traded company that specializes in commercial-scale energy storage systems.

HNEI is a research unit at the University of Hawaii which receives most of its funding from the Office of Naval Research, the U.S. Department of Energy and the state. It will pay for the batteries being used in the projects. HECO and its neighbor island affiliates are paying for the interconnection costs.

HECO plans to have the West Oahu battery system in service by the second quarter of this year, said Peter Rosegg, a company spokes­man.

The goal of the project is to "evaluate the capabilities of utility-operated battery energy storage sited at a substation to lessen the impacts of high PV penetration at both the circuit level and system level to allow as much PV on the system as safety and reliably possible," Rosegg said in an email.

"Hawaiian Electric needs to evaluate the efficiency and costs of circuit-level energy storage as a solution to allow more distributed generation photovoltaic systems — that is rooftop solar — on circuits with high PV penetration," he said.

On Molokai, HNEI is working with HECO subsidiary Maui Electric Co. on a 2-megawatt battery project that will address a combination of high PV penetration and relatively limited amount of conventional generating capacity that leaves the island’s grid vulnerable.

Energy generated from PV panels can account for as much as one-third of the island’s electricity consumption during certain times of the day. That generation is outside the utility’s control. That means MECO has to maintain frequency stability across the grid when it has control over only two-thirds of the power being generated.

If a tree were to fall on a power line or one of the diesel generators were to shut down, there could be a situation in which all the island’s PV systems would automatically disconnect from the grid. The utility may then have to quickly start up other generators to make up for the loss of PV power.

"We’re seeing these issues sooner on Molokai than on other islands because of the small grid," said Mathew McNeff, director of renewable energy resources for MECO.

The Molokai battery project is expected to be operational "later in 2014," Rocheleau said.

On Hawaii island, HNEI and Hawaii Electric Light Co. put a battery system into place at the start of this year at a wind energy project in Hawi. The project is being used to study and evaluate the effectiveness of battery systems to smooth voltage fluctuations and manage system frequency, Rocheleau said.

Another objective of HNEI in the Hawi project is to gather data on how to maximize the battery’s life, he said.

"Depending on how you operate it, you can control the lifetime of the battery. It’s a function of how hard you cycle it on and off," Rocheleau said.

"We’ve been pleased with what we’ve seen so far. It’s going very well."