Lessons from Hawaii: Clean, resilient cogeneration
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When you live on an island 2,000 miles from the mainland, you can’t take your energy source for granted.
That’s how Erick Tarvin became a leading authority on propane cogeneration systems in Hawaii. Cogeneration systems, also known as combined heat and power (CHP), use combustion engines or turbines to deliver a stable power source that’s highly efficient because the generator’s waste heat is used to provide heating and cooling. On an island with an unstable power grid, extreme weather, and no access to natural gas, large commercial buildings such as resorts and hospitals utilize the systems for affordable, sustainable resilience.
Tarvin gained expertise with gas turbine, micro turbine, and combustion engine technology in the military. So when he stayed in Hawaii to take a job with mechanical contractor Critchfield Pacific, the company sent him for training with turbine manufacturer Capstone Green Energy so he could install and service cogeneration systems.
Now with a new venture called Gordon Mechanical, Tarvin and his colleagues are hoping to spread cogeneration throughout Hawaii with a novel financing strategy that uses investor funds to pay for the equipment’s upfront cost. And the lessons learned from Hawaii’s cogeneration success could be applied to continental regions such as California, where unstable power grids create a need for reliable, efficient, on-site power sources.
Reliability at the resort
Tarvin’s first project with Critchfield was updating a 1 MW cogeneration system at the Westin Princeville Ocean Resort Villas in Kauai. The 346-room luxury resort is on a family-owned power grid that experiences frequent rolling blackouts and brownouts. So the resort takes some power from the grid but runs primarily on five micro combined cooling, heat, and power (micro-CCHP) units.
Exhaust gases from the units are collected in a heat-recovery module that makes hot water, which runs an absorption chiller that makes chilled water for air conditioning and refrigeration, as well as provides heating for four pools and domestic hot water for guest rooms and spa services.
With the Westin Princeville running smoothly, Tarvin went on to install larger systems. A project at the Westin Kā’anapali Ocean Resort Villas in Maui included 15 propane microturbines, and the Sheraton Waikiki used two large Jenbacher engines running on synthetic natural gas, a blend that includes propane.
Energy savings with no upfront cost
Now with Gordon Mechanical, Tarvin and his colleagues are offering to install cogeneration systems at resorts and other commercial buildings at no cost to the customer. Instead, investors pay for everything up front, and Gordon Mechanical acts like the power utility. The fuel and maintenance costs are covered in the cost of each kilowatt, and the hot water and chilled water are included at no additional cost.
Tarvin recently installed a test project at a major chain restaurant that demonstrates how the technology works. The system is based around a four-cylinder Tedom engine with an internal heat-recovery module in an enclosed box for quiet operation. The engine creates hot water at 190 degrees Fahrenheit, which runs to a Yazaki absorption chiller to create chilled water. The chilled water feeds a rooftop air-handling unit to provide air conditioning.
To allow the system to remain operational when maintenance is required on the engine, Tarvin included a propane tankless water heater system that keeps the absorption chiller running when the engine is offline. In a typical project, the hot water from the engine would also provide the restaurant’s domestic hot water through a heat exchanger.
For Hawaii businesses, the major selling point of the CHP systems is reliable energy, Tarvin says. “Timeshares or resorts will put it on their brochure that even if there’s an outage, a typhoon, or storms, and the grid goes down, they can stay fully operational with no downtime,” Tarvin says. At the same time, the system can provide virtually unlimited hot water with a fast recovery rate, as well as chilled water through the absorption chiller.
Businesses in the state are also held to strict emissions standards, and the propane engines can achieve zero or ultra-low emissions by burning almost 100 percent of the fuel and, thus, don’t need the extensive exhaust analysis required for diesel engines.
Where will cogeneration go next?
Tarvin sees cogeneration systems as a potential replacement for boilers in commercial applications due to their simple operation and maintenance needs. Whereas boilers require regular inspections, water treatment, and sometimes expensive maintenance, the CHP engines need only minimal maintenance and regular filter changes.
Renewable energy sources such as solar are part of the resilience solution, but they can provide only so much grid stability in one of the wettest climates on Earth. “When it’s cloudy, your solar farm isn’t doing much at all,” Tarvin says.
Although the per-kilowatt cost of a cogeneration system is typically slightly higher than the electric utility, the free hot water and chilled water mean that businesses will see overall energy cost savings along with the added resilience. Plus, the resilience itself provides financial benefits.
“I was talking to one of the engineers, and they said it’s the worst thing when the hot water or air conditioning goes down or when the power goes out because they have to give refunds or discounts to their customers,” Tarvin says. “When that hits a tourist and they get upset, you get bad reviews and it makes you look bad.”
With some proven success stories in Hawaii, Tarvin sees potential for cogeneration to spread throughout the U.S. mainland. In California, for example, where the utility’s public safety power shutoffs can leave homes and businesses in the dark, propane cogeneration systems could keep resorts and grocery stores in business. With a reliable energy source in on-site propane, businesses can enhance their resilience while meeting the desire for clean, sustainable energy.
To learn more about how CHP works and the best uses for it, check out “Propane Micro-CHP for Homes and Commercial Buildings” at Hanley Wood University.
Top photo: The Westin Princeville Ocean Resort Villas.