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HECO faces big challenges after solar PV explosion

With 12% of customers using PV, new rules were needed

Rockville, MD (February 3, 2015) -- As Hawaii's electric utilities address reliability issues stemming from an explosion in home PV systems, there are solar-integration lessons to be learned for grids in the rest of the US, EPRI senior project engineer Ben York told Smart Grid Today – the leading independent, daily, professional news journal of the smart grid industry – recently. Smart Grid Today publisher Modern Markets Intelligence, Inc. is sharing the story here, free of charge.

He spoke to Smart Grid Today from Honolulu where he is involved in research on PVs and other renewables.

QUOTABLE: The biggest takeaway is, we're starting to see the need for standards and equipment that goes beyond what we've traditionally thought about for PV generation. Hawaii is very dynamic and rapidly changing in this particular field. – EPRI senior project engineer Ben York

Hawaii had 850 home solar systems connected to the grid in 2008, Darren Pai, a spokesperson for Hawaiian Electric Co (HECO), told Smart Grid Today recently. By the end of last year the number had surged to 51,000, he added.

That's 12% or about one in eight of HECO's 450,000 customers – far more than any other utility in the nation, Pai said. Compare that with an average of one system per-240 homes on the mainland, York said.

"It's been an incredibly rapid pace," Pai said.

The huge growth in PV generation, with power flowing back onto the grid and potential fluctuations when clouds block the sun, can strain a system designed for a one-way, constant flow from the point of generation to the end-use customer, York noted. The danger is that power flow will veer from required parameters for voltage, posing risks to utility infrastructure, customer equipment and utility employees working in the field, he added.

"Now you have power generators, 'prosumers,' on a system that's designed to be one-way," York told Smart Grid Today last week. "That changes how the system works. If you get a lot of generation concentrated in one area, it's so far from how the system is designed, it may pose a reliability problem."

HECO was not prepared for the explosive home-solar growth, leaders of Hawaii's solar firms told Smart Grid Today.

"This whole solar PV thing started to blow up in 2008," Gary Ralston, founder of Hawaii Island Solar – on the island of Oahu – and a board member of the Hawaii Solar Energy Assn (HSEA), told Smart Grid Today this month. "By 2011, it was just going gangbusters.

QUOTABLE: I don't think Hawaiian Electric had any idea that all these people would be buying PV systems. So they, I'm sure, were caught by surprise. They had to put some kind of brakes on it before things got out of hand. – Gary Ralston, founder of Hawaii Island Solar and a board member of the Hawaii Solar Energy Assn

HECO in September 2013 began enforcing a provision in its PUC-approved tariff requiring that customers seeking to install solar systems on circuits with high amounts of solar follow a technical interconnection review process, Pai said. That process was meant to ensure new solar systems would not impact safety and reliability for those customers and their neighbors, he added.

QUOTABLE: Collectively, thousands of PV systems installed on our island grids can impact the overall system reliability. On Oahu, for example, PV systems cumulatively exceed 280 MWs, exceeding the size of the largest central station generator on the island. Especially on small, stand-alone island grids like ours with high concentrations of PV, voltage spikes can damage utility equipment, damage customers' appliances or even cause outages. – Darren Pai, a spokesperson for Hawaiian Electric

Solar firms were not prepared for the change that effectively brought new solar installations to a halt in September 2013 in areas that already had a lot of home PV. "They had said for a while that change was going to come but they didn't say when or what," Christian Adams, president and partner at Bonterra Solar in Honolulu and VP of HSEA, told Smart Grid Today recently.

When the utility sent a letter stating the new rules, "it was a shock to the whole industry."

The slowdown that followed left about 2,500 solar customers waiting for months for the go-ahead to connect rooftop PV to the grid. Some of those customers had already purchased a PV system.

HECO completed a series of the interconnection studies, Pai said. Most of those pending customers should be hooked up by April with another 200 connected by the end of 2015, he said.

Solar firms, meanwhile, took it on the chin.

Hawaiian Island Solar went from 20-25 salespeople and the same number of service technicians to four in sales and five service techs, Ralston told Smart Grid Today.

QUOTABLE: A lot of us had to lay off a lot of people. We still have a stack of people that were sold PV system that are waiting. Some of these people have waited so long that they have changed their minds or something might have happened in their family – somebody lost their job or got divorced – so not all of those jobs will be going through. It's been pretty devastating. – Ralston

Hawaiian Island Solar was not hit as hard as others because the firm is diversified – offering hot water systems, split PV-assisted AC that is not connected to the grid and solar PV pumps not connected to the grid. That gear does not need utility approval, Ralston said.

Bonterra's 2014 business was down 50% compared with 2012, Adams told Smart Grid Today.

Renegade systems seen

Some customers connected their home solar without permits. Late last year, HECO began notifying what it called "prematurely connected customers" – those who connected without a permit – to deactivate their PV systems while the utility reviewed their application, Pai said.

"To ensure safe, reliable service for all customers and protect our crews working in the field, it's important that we know where and how many PV systems are interconnected to neighborhood circuits," he added.

While the robust feeder lines near substations can more easily handle PV generation, smaller feeder lines serving more remote customers may not be strong enough for demands placed on them, York said.

The required upgrades so feeders can handle the demand vary from circuit to circuit, Pai said. If the upgrade has system-wide benefits, the cost may be passed on to all customers, he added.

Customers contribute

In other cases, under a regulatory "cost causation" principle, customers are responsible for upgrades that specifically benefit them, he added.

Typical equipment needed for the upgrade includes upgraded service transformers, grounding transformers, load tap changer controllers at substations and power lines, Pai said.

HECO recently approved about 1,000 applications for customers who agreed to share in the cost of upgrading certain control systems in neighborhood substations, he said, noting that the cost was less than $100/customer in most cases. For these customers, HECO upgraded load tap changer controllers that help regulate the flow of power the utility's substations.

More PV on the way

HECO has continued to approve PV interconnections each month, Pai said, noting about 11,000 applications were approved last year.

Once the issue is resolved, HECO expects faster growth. The firm has submitted plans to its PUC committing to increase renewable energy to at least 65% of all generation by 2030 – far above the current clean-energy mandate of 40%, Pai said. That includes tripling distributed, largely rooftop solar, he added.

With those plans in mind, HECO is conducting additional studies to determine whether other safety or reliability issues will arise as the utility pushes to even higher levels of PV on circuits, Pai said. "We really believe there is an opportunity to use more technology to improve the integration of not just PV but all renewable resources," he added.

More standards needed?

In the future, more standards and equipment may be needed. New standards could cover interconnection and equipment such as IEEE 1547 for connecting DR, and interconnection rules that are maintained by individual states or utilities, York said. Additional equipment might include smart inverters and other smart grid communications technologies, he added.

The story has been slightly edited for this format and is included in its entirety here and at To read more articles like this one, sign up for a Free Trial to Smart Grid Today.


Smart Grid Today's mission is to deliver daily, unbiased, comprehensive and original reporting on emerging trends, applications and policies driving the modern utility industry -- in a signature format our founders have developed over decades in the trade news business, featuring highly concise and easy-to-understand news copy based on trusted reporting, exclusive interviews, informed analysis and strategic insights that our subscribers rely on to succeed every business day.  Smart Grid Today is published by Modern Markets Intelligence, Inc.


Brett Brune
VP of Editorial
Modern Markets Intelligence, Inc.

Season Crawford
VP of Marketing
Modern Markets Intelligence, Inc.


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