The emerging power of microgrids


Attractive Attributes

Sophisticated energy management systems enable project developers today to design microgrids that can bring a diverse mix of distributed energy sources — rooftop solar photovoltaic panels, fuel cells, wind turbines, biomass-fired combined heat and power plants — together with state-of-the-art storage.

The result is a small-scale electricity-generating powerhouse that can balance and smooth variations in energy supply; provide services, such as voltage support and frequency regulation, to the conventional grid; and export electricity to the larger grid to make a profit or provide a boost during emergencies. Most notably, it can also keep its operator — whether a university campus, military installation, hospital or other facility — up and running in the event the main grid goes down.

[stextbox id=”custom” float=”true” align=”right” width=”300″ bcolor=”d2d0d1″ bgcolor=”dbdbdb” image=”null”]The microgrid projects Honeywell is designing for its customers place high value on the centralized management of supply and demand.[/stextbox]

“In some of these more forward-thinking microgrid approaches, it’s been resiliency, the availability of the grid for some sort of critical mission” that’s the big draw, says Paul Orzeske, president of Honeywell Building Solutions, which installs and designs systems that enable buildings to operate more efficiently.

Orzeske says the microgrid projects Honeywell is designing for its customers place high value on the centralized management of supply and demand. These energy management systems ensure, he says, “that you have very dynamic capability of adjusting the demand if the supply was going to drop off; if the supply hit an economic point where you want to be off the grid; if a storm was coming; if you had an opportunity to maximize wind resources, and then [re-adjust] when those wind resources went away after an hour or two.”

Where Microgrids Make Sense

Microgrids already make sense in areas with high energy prices, in remote locations (such as islands that have historically burned expensive imported diesel fuel for electricity), or facilities, such as military installations, that cannot risk losing power.

Take, for example, a project under development on the Hawaiian island of Kauai. The U.S. Navy’s Pacific Missile Range Facility  is located at the end of one branch of Kauai’s electricity distribution system. Eager to clean its power supply and reduce its energy bills — the average retail price of electricity in Hawaii is three times the national average — the Navy installed multiple rooftop solar arrays.

But when the Navy later sought permission to connect a large solar array atop a hangar, the local utility, Kauai Island Utility Cooperative, resisted on the grounds that electricity generated by the panels could strain its equipment and lead to backfeeding  — power flowing in the opposite direction than usual — at the point of interconnection between the base and KIUC grid.

The Navy turned to experts at the National Renewable Energy Laboratory for a solution,  and Honeywell was tasked with designing the energy management system used to smooth the surge and slumps in solar output triggered by passing clouds. The system couples fast controls with a small battery to rapidly respond to variations in the solar power supply.

According to Honeywell, discussions are underway to expand and upgrade the energy management system to a cyber-secure microgrid and use the solution at other U.S. military installations to enable greater penetration of renewable energy.

In remote areas without reliable access to the conventional grid, microgrids that can reduce consumption of expensive and dirty diesel fuel by substituting renewable energy and storage are also the obvious choice.

“If the business case for storage is built on reducing or optimizing the use of diesel fuel, it doesn’t take much to get a positive return on investment (ROI) for a storage asset,” Anissa Dehamna, a senior research analyst with Navigant Research’s Smart Energy practice, recently wrote at Navigant’s blog.

“In the case of remote microgrids,” she added, “the storage system typically provides several benefits: diesel reduction, higher renewables penetration, and improved power quality. Even if the business case is based only on diesel reduction, though, the ROI is still positive in less than 4 years across all advanced battery chemistries.”

In an ironic twist, Bill Siddall, vice president of marketing and sales for microgrid technology supplier TM3 Systems, says his company has been approached to develop microgrids capable of running on renewable energy for the energy sector, including offshore oil and gas drilling platforms.

“You would think, ‘Oil and gas, why do they care? They make the fuel, why would they care how much it costs?’” he says. But offshore platforms that are not tied to mainland power grids typically generate electricity by burning huge quantities of natural gas in inefficient gas turbines. With a microgrid in place, solar panels and wind turbines could be added to the generation mix, and gas turbines would operate at full capacity, boosting efficiency. Energy storage would capture surplus electricity generated by the gas turbines, enabling them to be turned off when not needed, and balance output from the mix of generation sources.

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