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$3.1M Battery Proposed for Power Plant

If you’ve noticed a lot of temporary electricity outages and lights dimming lately on Molokai, you’re not alone — and energy researchers have proposed a multi-million dollar project they hope will help stabilize the island’s electricity supply.

About one fifth of Molokai’s electricity comes from photovoltaic (PV) energy from business and residential solar panels, according to Mathew McNeff, Maui Electric manager of Renewable Energy Services Department. However, that high percentage is causing instabilities in the flow of electricity. Because energy generated from PV depends on conditions like the weather and daylight, it doesn’t provide a steady source of electricity to Molokai’s electric grid.

“For two years in a row, Maui Electric has been highest in the nation for number of PV [installations] so we’re having to come up with these solutions ourselves,” said McNeff.

The grid is divided into five circuits that provide energy to various areas of the island — about 2,000 customers in total. The peak load for Molokai — when the most electricity is used — is 5.4 MW, almost 200 times less than Oahu’s energy demands. But the smaller the grid, the greater the impact sudden changes in frequency can have, like the shut-down of a generator at the power plant or a tree falling on a power line, said McNeff.

The Problem
The majority of Molokai’s power is generated by three, 2 megawatt (MW) diesel generators and six smaller 1 MW generators at the Pala`au Power Plant. When a generator at plant shuts down, the system is built to automatically disconnect electricity from certain areas of Molokai to stabilize the grid and restore the system.

In the case of a significant drop in electric frequency, rooftop PV systems are also designed to quickly disconnect, and the further loss of power causes a domino effect which can lead to island-wide black-outs, according to McNeff.

“The increase in PV generation has increased the need for new solutions to reduce the impact of loss of generation,” he said.

Last year, Maui Electric conducted a study on the Kaunakakai circuit to determine how much additional PV could be installed without sacrificing the reliability of the system. That study revealed some serious issues, said McNeff.

Currently, several Molokai circuits have reached PV “saturation,” or the percentage of renewable energy a circuit can support while maintaining stability. Residents wishing to install rooftop PV in those areas must first pay for Maui Electric to perform an interconnection study to examine the effect of the proposed PV installation. But interconnection studies don’t assess the cumulative risks on the electric grid as a whole, said McNeff. Last year’s Kaunakakai circuit study found that the high percentages of PV on Molokai presented a risk to the entire grid, not just the circuit.

There are two separate sets of problems, according to Richard Rocheleau, director of the University of Hawaii’s Hawaii Natural Energy Institute (HNEI.) One challenge is overall instability in the grid, in which one event can trigger a chain reaction causing widespread power outages until the electric frequency can be stabilized. The other problem is how to add more PV penetration to each circuit and increase renewable energy integration without sacrificing reliability.

One proposed solution is a giant battery that would be installed at the Pala`au Power Plant and supplement the generators to stabilize the flow of electricity.

“This battery is going to fix the first problem and reduce brown-outs [partial power loss] – hopefully very significantly,” Rocheleau said at a meeting last week to present the proposed project to the community.

Some Molokai residents have noticed that the repeated drops and surges in electricity seem to have taken a toll on their appliances, costing them hundreds of dollars.

“I know of five friends who have lost refrigerators lately… and that’s really weird,” said resident Cheryl Corbiell. She stressed the importance of surge protectors to save personal digital technology. “We all have to take a hard look at how to protect our sensitive equipment…. And I’m hoping this battery will help.”

Battery Specs
The 2 MW battery, called a Battery Energy Storage System (BESS), would allow energy to be stored and switched on or off the grid at a moment’s notice. If one of the 2 MW generators tripped offline, for example, the battery would turn on long enough for the utility to resolve the issue, resulting in fewer power interruptions.

“One of the key things the battery can do is sit there for low cost and if there are generation losses, it can replace that power nearly instantaneously,” said Rocheleau.

Made of lithium ion titanate, the battery is safe, uses lower voltage and has a longer life than most lithium batteries, according to Rocheleau. Its 2600 cells allow the battery to be replaced and repaired by units without shutting down the entire system.

Rocheleau said a similar battery system was installed earlier this year on Hawaii Island and is being used successfully.

The battery is housed in a large shipping container that is dropped onto a pre-installed pad, interconnected to grid and is ready to go on-line in a short amount of time. It also uses highly-tested fire suppression technology, minimizing any risks of overheating, said Rocheleau.

The total project cost is estimated at $3.1 million for battery and installation on Molokai. HNEI would fund $1.8 million of the project through a grant from the Office of Naval Research, while Maui Electric would be responsible for the remaining $1.3 million. Maui Electric ratepayers would see an average monthly increase of 25 cents, spread across Maui County, according to Maui Electric officials.

“There is no hidden cost or charge – a minimal impact for benefits it could bring,” said Rocheleau.

Matt Yamashita, a Molokai resident and representative for Rising Sun Solar, said he sees no negatives to the proposed project.

“I think it’s a good project and I don’t see why anyone would oppose it,” said Yamashita. “There’s really no negative impact on our wallet… and it’s going to take us to where we need in terms of reliable system.”

Why Molokai?
The Navy is interested in reducing their fossil fuel dependence and developing energy efficient technology, and the Office of Naval Research manages that research, said Rocheleau. HNEI is partnering with them to obtain information about energy solutions that will be made public and used to help guide future projects.

“We are looking at better ways to operate small grid systems with high PV penetration,” said Rocheleau. “We’re trying to provide unbiased information that people can use to make decisions.

“We had funds and looked at where in Hawaii it made sense to put it. It turns out Molokai was ideal place to meet the objective of the program and meet a critical need here,” Rocheleau explained.

The battery would be owned by its manufacturer, Altair Nanotechnologies, until it is installed on Molokai and tested to function as expected. At that time, ownership would transfer to HNEI, then transfer again to Maui Electric under a memorandum of agreement that allows HNEI to collect data on the performance of the battery and its impact on the grid for several years. The battery would remain the sole property Maui Electric for the duration of its use, which Rocheleau estimates to be a lifespan of at least 10 years.

Hawaiian Electric’s Director of Systems Integration Marc Matsuura said they are working with the battery’s manufactures for the battery’s valuable parts to be recycled after it is no longer usable.

Rocheleau said if all moves forward as proposed, HNEI anticipates the battery will be operational by this summer.

Along with being able to quickly replace power from one of Maui Electric’s generators if it shuts down, the battery could also serve other functions. In its capacity as a research tool, the battery could continually monitor frequency on the grid, as well as serve as an operating reserve, reducing the need for additional fossil fuel and improving electrical stability, according to Rocheleau.

Stepping Stone for Solutions

After the Kaunakakai circuit study revealed major weaknesses in the system, Maui Electric considered several options to improve service, said McNeff. One option was to add another diesel generator to the power plant, which would remain running at all times in case a drop in frequency required extra generation to stabilize the system. However, this solution would increase usage of fossil fuels as well as additional costs to customers.

The utility also considered widespread use of smart grid technology, an emerging frequency-responsive grid system that’s still under experimentation. While Maui Electric officials say this type of technology will soon be used for the Maui County Kaunakakai Fire Station, it’s still under development for larger scale applications.

The third option was the battery storage system. Despite the benefits researchers hope the battery will bring to Molokai, Rocheleau noted that it will not solve all of Molokai’s electrical challenges, calling it an important first step that will allow additional research to take place.

Currently, he explained, once energy leaves the power plant, little is known about the system and there is “no active control of the grid at that point.”

“There’s not enough data right now to come up with a [complete] solution,” said Rocheleau. “The next step is to try to put better instrumentation on each line [circuit] and then we can start looking for solutions [to allow increased PV penetration]…The battery will stabilize the whole system and that will enable us to look at getting more renewables on circuits. It’s a necessary step.”

McNeff said one of the challenges to incorporation of PV into the circuit is a situation known as “back-feed,” in which excess energy generated by rooftop solar panels feeds back into the power line.

Electrical circuits are not designed to handle back-feed, he said. The excess energy has no place to go if that circuit generates more electricity than the current load, or usage demand. Inverters, which are designed to trip off-line in the case of a voltage spike, can’t stop back-feed but can only react to it, causing the domino effect Rocheleau explained.

McNeff said one solution to the back-feed problem is installing a “load bank” on each circuit.

“Engaging a load bank… would ‘suck up’ the voltage spike for a fraction of a second,” he said — enough time for the circuit to stabilize without the inverters shutting it off.

McNeff called load banks “the most promising option” but added the utility is sensitive to the high electric rates charged to customers so they are “still looking for more cost effective options.”

In the meantime, researchers and residents hope the battery will bring an end to frequent power outages.

“This technology is solving one problem and hopefully contributing to the solution to another problem,” said Rocheleau.


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