In the first five months of this year, more than a quarter of collected wind energy reported from three wind farms that deliver electricity to Maui Electric Co. has been dumped from the grid, according to the utility’s website.
As of the latest reported data through May, about 28.8 gigawatt hours of wind energy have been curtailed or dumped, which has cost MECO customers an estimated $352,000, according to state Public Utilities Commission calculations.
About 70.1 gwh has been accepted in the grid in the period.
Because “as-available” resources, like wind and solar energy, vary greatly based on weather and other conditions, the dumping of power becomes an issue, explained MECO spokeswoman Kau’i Awai-Dickson.
“For example, it may be windy in the early-morning hours but less power is being used by households,” Awai-Dickson said in an email.
“To maintain reliable electrical service, MECO must balance energy supply with what our customers are using moment to moment in real time.”
When it is windy outside, the utility relies more on wind energy and turns down its oil-fired generators at Kahului and Maalaea power plants, though the utility still keeps some generators running at all times to ensure that, if the wind suddenly stops blowing, customers will not lose electricity.
Wind energy costs about 12 cents per kilowatt hour, while fossil fuel generation costs 21 cents per kwh.
When the amount of wind energy exceeds customers’ demand for electricity at a given time, that energy is curtailed or dumped.
MECO officials note that the possibility of curtailment was expected with the wind farms and is common with renewable energy which, while cheaper, is not as reliable as fossil-fuel generators. Additionally, the reported cost of curtailment to customers does not take into account the additional costs of modifying the grid to integrate more wind energy, Awai-Dickson said. In other words, upgrading the transmission and distribution system could cost customers even more than the estimated costs from wind energy curtailment.
MECO expects to curtail 54.4 gwh of wind generated energy annually, with 43.6 gwh of that energy coming from Kaheawa II wind farm above Maalaea, according to state filings. This is due to a “last in, first out process,” according to energy officials. Because Kaheawa II was the latest wind farm to come on line – after Kaheawa I in Maalaea and Auwahi Wind in Ulupalakua – wind energy is taken from the other two wind farms first, and when customer demand is met, the excess energy is dumped.
Some energy officials have suggested that more efforts should be made to find a way to store the excess energy to use when it is not windy, though such projects could be quite costly.
MECO’s current battery storage systems only have the capacity to store energy for a few minutes, according to utility officials.
“MECO lacks ways to store energy,” Maui Energy Commissioner Doug McLeod said in an email. “The peak load is approximately 200 megawatts on Maui. We have added 100 (megawatts) of solar and wind generation since 2006 and no MECO units were decommissioned. There is simply more power than we need on windy days.”
The PUC said that the amount of curtailment is a waste of money, fossil fuels and ultimately, customer dollars.
“This amount of wind curtailment represents almost 6 percent of the 2012 Test Year annual fossil generation for the Maui division and an indication of fossil fuel transshipped and imported into Maui that could be avoided,” said the commission’s scathing decision and order for MECO issued in May.
The commission ordered the utility to post via its website every month the quantity of wind energy accepted per month, the quantity of wind curtailed per month and the estimated cost of curtailed energy for customers. The commission also ordered MECO to submit by Sept. 3 a plan to lower fuel costs and to reduce curtailment of lower cost wind energy.
A Maui Energy Storage Study conducted by Sandia National Laboratories last year suggested that the utility could reduce or eliminate the operation of the Kahului Power Plant by installing a battery energy storage system, which could save the utility nearly $6 million each year, according to PUC documents.
Many county officials and residents have long complained that the Kahului facility was outdated, costly and even toxic.
“We share the commission’s concerns about MECO’s reluctance to retire the Kahului Power Plant and the need to eliminate the dumping of unused wind energy that could replace about 6 percent of MECO’s fossil fuel generation load,” Mayor Alan Arakawa and County Council Chairwoman Gladys Baisa said in written testimony last month. The administration advocated for energy storage systems and smart grid/demand response systems to eliminate the curtailment of low-cost wind energy.
Parent company Hawaiian Electric Co. announced Monday its plans to deactivate two of the four units at the Kahului Power Plant next year, along with Oahu’s Honolulu Power Plant. Maui Electric officials have said they plan to retire the entire Kahului facility by 2019.
“Maui Electric is committed to our wind energy partners to use as much of the electricity they can supply while keeping to our commitment to customers to provide safe, reliable power at the lowest price possible,” Awai-Dickson said. “We realize much remains to be done as Maui Electric continues to do what’s right for our community to add even more clean energy in a safe and reliable way.”
She added that nearly 21 percent of electricity delivered to MECO customers came from renewable resources like wind, biomass, hydroelectric and photovoltaic, or solar.
The utility plans on submitting its System Improvement and Curtailment Reduction Plan, as mandated by the state commission, by the September deadline.