MECO seeks to have customers pay for curtailed solar power

Total from 2 projects is $155,000 for 2018

South Maui Renewables Resources, shown here in a photo taken last November, and Ku‘ia Solar were paid a total of about $150,000 by Maui Electric Co. per their power purchase agreements for “compensable curtailed energy” for 2018. MECO is asking the state Public Utilities Commission to allow the utility to pass the cost for 1.4 gigawatt hours of solar power that was produced but not used on to ratepayers. The Maui News / MATTHEW THAYER photo

Maui Electric Co. is seeking the approval of the state Public Utilities Commission to pass on $155,000 in charges for 1.4 gigawatt hours of unused power last year from the two utility-scale solar arrays that went online last year.

In a Jan. 31 filing, MECO said it paid South Maui Renewable Resources, a 2.87-megawatt project located near the Maui Research and Technology Park, $110,359.33 for 997.8 megawatt hours of “compensable curtailed energy” per its power purchase agreement.

Curtailed energy means power supplied but unused by the utility.

The payment was from May, when the county’s first utility-scale solar project went online, until Dec. 31. The PUC filing said that SMRR has an annual energy contract for 6.75 gigawatt hours.

Ku’ia Solar, the 2.87-MW solar project near Lahainaluna High School, billed MECO for $44,803.80 for 405.1 MWh of compensable curtailed energy. The amount is less than SMRR because Ku’ia came online in October. Its total annual contract for energy is 6.6 GWh, the PUC filing said.

Ku’ia and SMRR are both operated by Kenyon Energy and are paid 11.06 cents per kilowatt hour for energy fed into MECO’s grid, which is lower than the cost of fossil-fuel produced power.

MECO was required to file a report quantifying payments it seeks to recover from ratepayers for compensable curtailed energy and its rationale by Jan. 31, the PUC filing said.

When asked for data on total curtailed power, total accepted power and percentage of curtailed power from SMRR and Ku’ia, MECO spokeswoman Sayble Bissen said the utility reports “do not separate energy usage by facility nor do they contain curtailment figures.”

Updated figures will be submitted in MECO’s “2018 Renewable Portfolio Standard Status Report” that would include energy used from the SMRR and Ku’ia grid-scale solar projects but their data would not be broken out, she indicated.

In its PUC filing, MECO said that the amount of noncontrollable rooftop solar, which is more than 100 MW, contributes to curtailment of grid-scale variable generation, such as wind and solar, during daytime hours.

To maintain grid stability, the utility has to keep supply and demand equal at every moment, and with rooftop solar feeding the system with variable amounts without control, MECO regulates sources it has the ability to, such as wind and solar, as well as keeping fossil fuel generators running.

MECO explained that SMRR and Ku’ia currently hold “the highest curtailment priority and are the first to be curtailed.”

The introduction of controllable rooftop solar programs, such as Customer Grid Supply and Community-Based Renewable Energy, will increase the possibility of curtailment of the utility-scale solar power sources, MECO told the PUC. These new programs hold a lower curtailment priority than SMRR and Ku’ia. In addition, increasing popularity of those programs will decrease available space on the grid to accept SMRR-Ku’ia power.

MECO said it has been working in recent years to increase the amount of variable renewable generation it can accept and to reduce curtailment. The utility has tried to improve its forecasting of renewable energy sources, which allows MECO to better plan its own power generation.

The Maui County utility also has implemented set-point automatic generation control on several of its generating units, MECO said. This system more precisely regulates units to maintain system stability while integrating as-available renewable sources.

Set-point control has been implemented on the largest units at both the Maalaea and the Kahului power plants, said Bissen. The system enables the units to be more responsive to fluctuations of power generation from the various wind and photovoltaic generating facilities on Maui.

Low-load modifications to heat-recovery steam generators on two of its Maalaea plant units also were cited by MECO in its filing as a method to integrate more wind and solar power. Modifications were made to the largest units at the Maalaea plant to allow them to run at loads lower than originally intended, Bissen said.

“Having the units operate at lower levels allows for us to accept more generation from renewable resources while maintaining the ability for the units to ramp up in response to any fluctuations in generation being produced by renewable resources,” she said.

* Lee Imada can be reached at leeimada@mauinews.com.

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