WSJ -- Hawaii Wrestles With Vagaries of Solar Power ....................................
June 28, 2015
Hawaii Wrestles With Vagaries of Solar Power
State pushes into renewable energy but sudden swings in output pose special challenges
By Rebecca Smith and Lynn Cook
For a glimpse of the promise and problems of turning the electric grid green, there’s no better place to look than Hawaii.
With 21% of its power now coming from renewable sources like wind turbines and solar panels, Hawaii has become a laboratory for those intent on reinventing the grid. A new law mandates that renewables supply all of the state’s electricity by 2045.
But Hawaii’s grid is already running into problems with its heavy helping of rooftop solar and other carbon-free renewables. Among them: sudden swings in the output of solar and wind, which force the state’s main utility to scramble to try to keep the overall supply of power steady.
State officials concede that there are problems. “But we’re highly optimistic we’re going to work through these issues and become energy self-reliant,” says Mark Glick, head of the Hawaii State Energy Office. “We don’t lack confidence at all.”
Though Hawaii’s effort is attracting attention around the globe, its electric system is unusual. For starters, each island has its own electric grid, and they aren’t connected. On the mainland, three big power grids serve 48 states; typically, the bigger the grid, the more stable it is.
Hawaii remains the only state that still burns oil to generate most of its electricity -- about 70% for the islands versus 1% for the U.S. as a whole, according to federal data. That has pushed Hawaii’s average electricity price to 34 cents a kilowatt-hour, the highest in the U.S. and nearly triple the national average, the data shows.
Partly as a result, an unusual number of islanders have put solar panels on their roofs. On Oahu, where most of Hawaii’s population lives, 13% of residential utility customers have solar systems, more than any other state, according to data from Hawaiian Electric Industries, the state’s biggest utility, and the U.S. Energy Information Administration.
More than 50,000 houses in the state act as tiny power plants, putting any electricity that they don’t use onto the grid. But grids were designed to zip electrons across high-voltage wires from a few big power plants to homes and businesses; they were not made to work the other way around. Traditional power plants weren't designed to ramp up and down quickly, either -- making it tough to absorb bursts of solar power added to the grid on sunny days or make up for a sudden drop on cloudy ones.
“It’s a grand experiment that’s playing out right now in Hawaii,” says Marco Mangelsdorf, president of ProVision Solar Inc., a company that installs photovoltaic panels on the Big Island of Hawaii.
Oahu has 470 megawatts of renewables and peak demand of about 1,100 megawatts, according to Hawaiian Electric, so at times as much as a third of its electricity comes from green sources. But a lot of it shuts down at night when the sun sets, so the utility has to balance things out with its own power plants.
On windy Maui, peak electricity demand is about 200 megawatts; the island has 150 megawatts of renewable capacity, half of it consisting of wind turbines. That means sometimes as much as 75% of power generated comes from variable sources like the wind and sun.
When power production from renewable sources changes suddenly, utilities have to be able to keep overall supply steady. The mechanics of power grids demand that supply exactly match demand, because insufficient electricity, or an oversupply, could damage equipment or cause a blackout.
Utilities typically have no way to measure the amount of electricity being put on power lines by solar panels, in real time. Nor can they control it.
That didn’t matter when there wasn’t much solar production. But some Honolulu neighborhoods have so many solar-equipped homes cranking out electricity in the middle of the day, when people are at work, that the power can swamp electrical lines and back up into power substations, where it could harm equipment there and in other parts of the grid.
So Hawaiian Electric has been beefing up its networks and also telling some customers they have to hold off on adding rooftop systems. The company, which provides almost all the electricity in the state, recently agreed to a buyout offer from NextEra Energy Resources LLC.
The company is also scattering solar sensors across its system to give engineers better data so they can estimate the output of privately owned solar panels. That will allow it to generate the right amount of power to fill the gap between what’s being produced by rooftop solar panels and how much Hawaiians actually need.
“We aren’t flying blind anymore,” says Colton Ching, vice president of electricity delivery for Hawaiian Electric.
To get more control over the power produced by homeowners and businesses, the company also is requiring new solar installations to include equipment called smart inverters. Inverters take electricity from solar panels and convert it to a form that can be used in homes or put on electric lines. The smart varieties of inverters can send and receive information from grid operators and are less likely to trip off if there are minor problems. Advanced models may one day allow utilities as well as homeowners to regulate the amount of power flowing on to the grid. Ultimately, they may tie a lot of separate solar power systems together so that they function more like conventional power plants whose electric output can be turned up or down.
Hawaii’s future may include energy storage, too. The utility is seeking bids to create 300 megawatts of energy storage on Oahu, which it hopes will smooth out supplies so that it doesn’t have to turn its traditional generators up and down so much.
Write to Rebecca Smith at rebecca.smith@wsj.com and Lynn Cook at lynn.cook@wsj.com
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