Balancing Hawaii's energy supply and demand
Solar and wind power are clean and renewable, but their variability needs to be matched with techniques, storage and "firm" sources to meet consumer demand
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The sun and wind create clean, local energy for Hawaii, but they’re intermittent. They come and go on a schedule that doesn’t follow the Islands’ demand for power. Here are nine ways to ensure Hawaii’s energy supply and demand match.
In the field of power delivery, load balancing – matching supply to demand – is a constant high-wire act. Too little supply relative to demand, and you create blackouts. Provide too much power, and you suffer frequency fluctuations that can knock out your customers’ Keurigs.
Conventional utilities balance this delicate equation by making sure their fuel is, in industry parlance, firm and dispatchable – that the power capacity can be guaranteed ahead of time and put into service as needed. In Hawaii, that has usually meant burning oil and coal.
But fossil fuels burn dirty, and oil is subject to global price fluctuations that have helped drive Hawaii’s electricity costs to the highest in the nation by far. In partnership with the U.S. Department of Energy, Hawaii has charted the most ambitious energy overhaul course in the nation: at least 40 percent renewable, clean, locally generated energy across the state by 2030.
Admirable. But while sun and wind, renewable energy’s workhorses, are clean, local and effectively infinite, they come and go according to their schedule, not ours. Wind often blows hardest late at night, when demand is low. And the sun goes down just when energy needs peak, as people get home, cook dinner, take a shower and turn on the TV.
In a world where energy may one day be 40 percent, or even 90 percent, renewable, the new load-balancing act will be a lot more complicated than the old one. What will it look like? No one knows, says Makena Coffman, an energy policy specialist in UH-Manoa’s Department of Urban and Regional Planning, but one thing is clear: “There’s no silver bullet. Many things will have a role to play.”
Here is a look at some possibilities for those “many things,” broken down into three major categories: technology, management systems and constant renewables. None are a lock because each has pluses and minuses, and each will take years – if not decades – to implement fully. But some of them are likely to be a significant part of our energy future.
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Sources: Hawaiian Electric Co. and Blue Planet Foundation
When Supply Exceeds Demand, Sock It Away
Here are the three technologies that could play a major role in storing renewable energy so we can use it whenever we need electricity.
Storage Technology #1: Batteries
“Storage is the big question” for intermittent renewables, says Coffman. Batteries have been around a long time and are our go-to energy-storage devices for their versatility and reliability. Utility-scale batteries like those used today at Kahuku Wind farm on Oahu’s North Shore can smooth out bumps and valleys in power supply. Jeff Mikulina, executive director of the nonprofit Blue Planet Foundation, says that the smaller, residential-scale batteries used as household backup in Japan and Europe could one day become part of the load-balancing potential of an American smart grid.
Pro: Reliable, portable.
Con: Slow to charge and discharge, uses a lot of space relative to energy stored, often made of toxic materials.
Storage Technology #2: Pumped Storage
This low-tech approach to energy storage takes power the grid doesn’t need and uses it to pump water uphill. When energy is wanted, the released water runs downhill to turn a turbine that generates electricity. Large pumped-hydro stations are often used to balance out the supply of energy at nuclear power plants (which are hard to cycle down), but the smaller facilities being studied for use on the Neighbor Islands would do the same for solar or wind power.
Pro: Clean, proven, low-maintenance.
Con: Hard to site; can affect landscape.
Storage Technology #3: Compressed Air
Surplus renewable energy can also be used to pressurize air, which turns a turbine when released. Compressed-air-storage facilities currently operating on the mainland and in Germany pump air into large underground caverns. Hawaii doesn’t have those, but we do have the ocean. At MIT, massive concrete spheres with walls three meters thick have been proposed for undersea air storage. Researchers at the University of Nottingham in the United Kingdom are developing a less weighty solution: the Energy Bag, a giant sack made of aerospace-grade fabric that would rely on the intense pressure of a deep-sea environment to keep the air in check until it’s needed.
Pro: Clean; uses assets we have, like near-shore deep water.
Con: Promising, but technology’s not there yet.
When Demand Exceeds Supply, Manage Demand
Utilities across the state are experimenting with smart grids, which allow minute-by-minute two-way communication between utility and customer. “Smart gridding does a lot of things,” says Coffman, “but the basic idea is a shift (for the utility) from being a passive provider of energy to being a very active manager of it.” Here are three management tools that can help match renewable supply with existing and future demand.
Management Tool #1: Time-of-Use Rates
European and Asian countries, where power can be more expensive than in Hawaii, have adopted rate schedules in which electricity costs more at peak hours. Consumers eager to save money respond to these price differences, and that creates smaller peaks in demand. Mikulina says that, in some places, customers even occasionally get paid to use power. Hawaii utilities are introducing voluntary time-of-use rates.
Replaces: One price for one kilowatt hour, regardless of how much it costs the utility to produce.
Management Tool #2: Demand Response
With the Hyatt Regency Maui Resort & Spa as its first partner, the Maui Electric Co. has introduced a fast demand-response pilot program for commercial and industrial customers that pays businesses for turning off noncritical electrical functions for short periods of time to balance load. Currently, MECO sends a request to the Hyatt, which voluntarily scales back noncritical functions, like back-of-house air conditioning, for up to an hour. Other demand-response pilot programs in California and the United Kingdom are automated, but with an optional override. Eventually, Mikulina envisions an ultra-responsive smart grid that could manage load seamlessly and unnoticeably by turning off your exhaust fan or pool pump for a few minutes at a time.
Replaces: “Spinning reserve,” in which utilities burn fuel to keep a turbine spinning but unconnected, in case it is needed to absorb unexpected demand or shortfall of other energy sources – say when a big cloud blocks the sun and solar power output drops quickly.
Management Tool #3: Customer Control
Smart grids also put power in the hands of individuals. In New York City, Con Edison customers who want to walk into a cool house at the end of a broiling summer day can sign up for the CoolNYC program. Instead of leaving the A/C on all day, users get an app that can turn on their air conditioners when they are already homebound. Whole-home energy monitors like The Energy Detective, which provide instantaneous usage feedback, can also help energy end-users stay in the driver’s seat.
Replaces: One-way-information analog meters.
Partner Solar and Wind with Constant Renewables
Increasing storage capacity and managing demand can go a long way toward making wind and solar work with the grid, but, in the near term, Hawaii’s power supply needs a firm, dispatchable source of energy. It just doesn’t have to be fossil fuel. What renewables do we have plenty of?
Constant Renewable #1: Trash
On Oahu, the HPOWER waste-to-energy facility has been turning trash into power since 1990. Oahu’s Hawaiian Electric Co. has also contracted Honua Power to “gasify” some of the island’s waste. Gasification turns biomass waste (such as plant clippings) and other organic renewables into clean energy by producing a gaseous biofuel that can be burned to drive turbines. Honua claims this approach, which has been around for more than a century, will reduce environmental impact by 90 percent in comparison with typical plants burning fossil fuel.
Pro: Kills two birds with one stone, removing methane-producing waste from the island system and producing energy.
Con: Burning trash directly (HPOWER) still adds significantly to pollution, and supplies of waste biomass are limited. HECO says Honua’s facility is not yet completed.
Constant Renewable #2: Trees and Other Biofuels
There are many biofuel projects going on in Hawaii, but the Kauai Island Utility Cooperative is betting big on wood, mankind’s original source of renewable energy. KIUC has contracted with Green Energy Team LLC to buy power produced from a plant that will convert biomass (trees) into electricity. A German corporation, Standardkessel, is slated to build the plant near Koloa using technologies that Eric Knutzen of the Green Energy Team says will reduce nitrogen oxides by 80 percent and sulfur oxides by 66 percent versus the current diesel fuel power plant, which will be dialed down as the new plant comes online. According to Knutzen, invasive albizia trees will be cleared from 2,000 acres on Kauai and replaced with fast-growing, noninvasive tropical hardwoods approved by the state Department of Land and Natural Resources. Both cleared albizia and the planted hardwoods will be used in the closed-loop biomass-to-energy plant, which, when operational, will be the first such facility in the U.S.
Knutzen says the CO2 absorbed by the trees as they grow will offset the carbon emitted during burning, for a carbon-neutral process.
Pro: Cleaner, cheaper firm power. Knutzen says the state’s consumer advocate found that the plant would save KIUC’s customers between $5.5 million and $20 million dollars per year.
Con: Growing trees for fuel is land greedy and climate specific. Workable for Kauai; harder for Oahu.
Constant Renewable #3: Geothermal
Hawaii Island’s Hawaii Electric Light Co. supplies its customers with more than 30 percent renewable energy, the highest percentage in the state by far, in large part thanks to the energy produced by Puna Geothermal Venture. Right now, geothermal-generated electricity is confined to Hawaii Island, but, in March 2012, a bill passed by the state Legislature laid the regulatory framework for undersea cables that would allow islands to share power.
Pro: The “holy grail” of 21st-century energy is a “cheap, firm, dispatchable, renewable resource,” says Blue Planet’s program director, Richard Wallsgrove, and geothermal energy can be all of those things.
Con: Great for Hawaii Island; for the rest of us, geothermal will take longer and cost more.
“We have a huge opportunity to truly make Hawaii a global leader in something that is the generational challenge,” says Mikulina, of Blue Planet Foundation. Colton Ching, VP of energy delivery at HECO, agrees: “The solutions here (in Hawaii) are more easily identifiable. And (unlike on the mainland) we’re all on the same side of the table, saying ‘Yeah, we should do this. Let’s find a way to make it happen.’”
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