For the second time in a stretch of eight days, Hawaiian Electric Co. asked its customers to cut evening electricity use Tuesday and warned that power failures could occur if demand remains high and another generator loses power.
HECO attributes much of the problem to hot weather and high consumption of electricity for air conditioning, but a downed power provider in Kalaeloa and little wind at two North Shore wind farms also prompted a drop in power generation.
"It’s not one single factor," said HECO spokesman Darren Pai. "It’s a combination of all these things."
HECO said Tuesday night that no outages occurred during the peak electricity usage hours.
One common factor linking Tuesday’s situation and the HECO advisory issued Sept. 8 is the downed power plant in Kalaeloa owned by Kalaeloa Partners, an independent power producer.
The plant, which has the capacity to fill a fifth of Oahu’s average daily demand, has a continuing boiler problem, and customers are asked to keep usage down while repairs are being made.
HECO said in a news release Tuesday the Kalaeloa plant was out of service due to the unexpected repairs. That plant went down Sept. 7, produced some power for a period of time, then the entire plant had to be brought down for repairs, Pai said.
The plant, which has a conventional oil-burning generator, can produce up to 208 megawatts of power, which "makes up a significant amount of normal generation" to fill the average daily demand of 1,000 to 1,100 megawatts.
HECO asked customers to reduce their usage Sept. 8, when Kalaeloa and a second major generator, its 90-megawatt Waiau plant, went offline for repairs.
Another common denominator shared by the two warnings was the fact that little energy was produced by the two wind farms in Kahuku and the Kawailoa Wind Farm near Haleiwa, due to light wind. The farms normally have a combined output of close to 100 megawatts of power.
"The main issue today is that we’ve been monitoring the use of electricity, and due to the hot and muggy conditions, it has been really quite high," said Pai. "We are predicting it’s going to be quite high during peak demand."
That period, from 5 to 9 p.m., is when people are home and usage normally goes up due to cooking, bathing and other activities.
HECO suggested turning off or lessening use of air conditioners, delaying hot showers and dishwashing and minimizing cooking until later in the evening to reduce overall electricity use.
"As we saw last week, cooperation from our customers helps because every little bit of energy we conserve makes a difference," Pai said in a news release.
At 4 p.m. Tuesday, when HECO sent out the request, the company anticipated it would be able to meet the evening’s peak demand but that backup generation reserves would be very low.
HECO also has its Kahe plant, HPOWER, and biofuel and coal plants in Campbell Industrial Park, as well as solar projects that include tens of thousands of rooftop systems and larger projects.
But during the evening, the photovoltaic systems "don’t contribute to meeting our customers’ energy needs," since the energy can’t be stored for use, Pai said.
HECO is working on developing an energy storage system for the solar projects, with a request for proposals out to bid.
