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At press time, Hawaiian Electric (HECO) had just issued the all clear:

“A combination of factors led Hawaiian Electric to ask customers to conserve power tonight. Demand for power was high due to hot, muggy weather. Also, the Kalaeloa Partners power plant is out of service due to unexpected repairs. In addition, continued light winds mean there is little power being provided by the island’s wind farms.”

HECO is a night-peaking utility. This is why the utility can hold up interconnection permits for photovoltaic power systems with one hand and issue outage alerts with the other. Despite the popularity of and demand for residential PV systems, most people are working in offices during the day, where presumably it is more efficient to provide climate control collectively. As a result, HECO requires inverter features or kill switches to shut off residential PV systems when the backfeed overwhelms the grid.

Hawaii, with its multiple islands with largely discreet grids, is an instructive case study for the interplay between intermittent sources, load and grid stability. PV doesn’t always peak when it is most convenient. As shown above, wind farms do not always hold up their end of the bargain at night. Conventional baseline sources can go down. It is not always possible - in this case, it is impossible - to dial up power from elsewhere.

The more conference sessions I attend, the more I hear about getting people to change their behavior. As a society, the argument goes, people should reorganize their lives around the peaking availability of intermittent sources. This is a nice thought. In the mean time, while awaiting instructions, people need to go to work during office hours so they can pay their bills and their taxes.

Yet society is changing. Regardless of the legal challenges waiting to pounce on the U.S. Environmental Protection Agency’s proposed carbon emission rules, certain classes of mostly coal-fired power plants are going away. One analyst says small coal plants of 200 MW or less will be unable to cost-effectively implement the pollution-control technologies that will be required in any case. All these - and many larger ones - will go away.

The question is how power providers will devise a mix of renewable energy sources with a low-carbon baseline. The future of renewable energy will be one of hybrid sources, with each playing to its strength. S

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