Fire Island is a small
island near the top of Cook Inlet in the Municipality of Anchorage, Alaska.
While it once served as an Air Force station, the island now sits vacant other
than a private FAA aviation airfield and a wind farm.
The 11-turbine,
17.6-MW wind farm, built by Fire Island Wind LLC in
2012 (a subsidiary of island owner Cook Inlet Region Incorporated or CIRI), is
the first megawatt-scale project in South-central Alaska. According to Fire
Island Wind, the aim of the project was to ease the strain on the natural gas
supply in Cook Inlet.
Although the wind farm
can generate more than 50,000 MW-hours annually for the utility, Chugach
Electric Association, leveraging the project’s full capacity has been a
challenge over the years.
“Power usage of this
wind farm is relatively low,” says Massimo Danieli, President of ABB’s Grid
Automation division. ABB is a power technology company currently
working with Chugach Electric on better managing the Alaskan transmission grid.
“The wind farm sells roughly 4% of the retail capacity of Chugach Electric, so
it is not a large proportion or quota of the overall electricity sold by the
utility into the Anchorage area.”
Upon completion of the
wind farm, Fire Island Wind entered into a long-term power purchase agreement
with Anchorage utility Chugach Electric Association. The 25-year contract
provides a flat net price of $97/MW-hour throughout its term.
“A problem for the
utility is variability of the load and supply.” Danieli points to the
variability of wind along with a number of different energy sources that feed
and impact the local transmission system. Anchorage is served by wind energy,
hydropower, gas, and fire
or thermal capacity. Transportation of fuel is another concern.
“The city has ports,
which can mean heavy transportation loads coming from vessels and cranes. This
can lead to further pressure on the utility to keep up with power demands,” he
says. “To better manage the load and demands, Chugach Electric needs to add
regulatory capacity to the transmission grid, which, at only about 500 MW, is
not a large grid. ”
There is also talk of
expanding the wind farm. CIRI wants to double the number of wind turbines on Fire Island from 11 to
22. It announced a framework deal with utility Golden Valley Electric
Association late last summer. So there may be more wind power on the way.
“The two devices — the flywheels and
lithium-ion batteries — will connect to the grid together with a control system
we call PowerStore,” says Danieli. “This system has the important task of
master control by monitoring and sharing power capacity across the wind farm,
flywheel, and battery. Its goal is to continually maintain grid stability.”
He explains that the
flywheel and battery will connect to the grid and act like two generators.
“Together, they can take in, sync, and release power to ensure a stable online
frequency — in fact, it is very much like a form of load sharing.”
While the two power
devices work to share the load, the PowerStore control system continuously
monitors the status of the transmission grid. Ultimately, it is in charge of
when energy should sync into the flywheel or battery storage. “It also has to
‘decide’ when to release energy, first from the flywheel and secondly from the
battery,” says Danieli. “It is constantly assessing and redirecting the power
supply or surplus.”
Lithium-ions are the
battery of choice here because they are a low-maintenance, high-density
battery. One other advantage of lithium-ion cells is that their rate of
self-discharge is much lower than that of other rechargeable cells, such as
Ni-Cad and NiMH forms.
But why the need for a
battery and flywheel? “It is proven that when you have high variability of
power generation and a sudden heavy load on the grid, such as when you have
strong wind gusts at a wind farm, it is necessary to release that energy
quickly to maintain the frequency or stability of the transmission system,”
shares Danieli. “Try that over several cycles on a battery used for storage,
and you quickly reduce the life of that battery.”
Batteries may work
well for storing or generating a constant flow of energy, but they are less
than ideal for sudden or abrupt changes, such as those that occur at wind
farms. Enter the modern flywheel. It consists of a large rotating mass
supported on a stator by magnetic bearings. Furthermore, it typically operates
in a vacuum to reduce drag.
Flywheels can bridge
the gap between short-term power and long-term energy storage with excellent
cyclic and load following characteristics.
“The PowerStore system
uses a flywheel for fast release and sync of power, which can go up to one
megawatt per second and then back down again. So, these fast variations are
managed by a flywheel, where it excels, and the slower variations are dealt
with through battery storage.”
High-speed software
controls the power flow into and out of the flywheel, essentially making it a
high inertia, electrical shock absorber that can instantly smooth out power
fluctuations.”
The hybrid system
prioritizes one over the other, flywheel or battery, depending on the system
conditions,” says Danieli. “It rapidly stabilizes voltage, but also improves
power quality by absorbing or injecting that power to ensure a smooth network.”
PowerStore can stabilize voltage and frequency, hold 18 megawatt-seconds of
energy, and shift from full absorption to full injection in one millisecond to
stabilize the grid.
What makes ABB’s
microgrid system ideal for integration with the Fire Island wind farm
is that it is modular and made for extreme weather conditions.
“If tomorrow the size
of the wind farm becomes twice what it is today, as may be the case at Fire
Island, there will be a PowerStore with twice the capacity. The equipment
itself is modular and contains all the connections needed to build on one
another or increase in capacity.”
Danieli explains
further. “Say you add another 10 or 20 turbines to your wind farm, from a microgrid
standpoint, you simply add a small controller for each turbine to the network,
and they automatically link up to the network and start co-operating with the
other controllers.”
The system is built
for efficiency and to minimize installation times. It is also build to endure
the Alaskan climate.
“The system is
extremely robust and made to last in harsh conditions,” he says. “The
lithium-ion batteries, of course, have a degradation period that is in the
range of years. But this also depends on the way they are used and maintained.”
Danieli says the units are equipped with air conditioning to better sustain the
electronic equipment and to evacuate gases and elements that could build up
inside the batteries. “There is definitely a bit of art and engineering in
making sure the equipment is made and used appropriately.”
A well-devised O&M
plan is essential along with system versatility. As more microgrid and energy
storage projects develop, the equipment supporting these systems must fit each
climate and application.
“One cannot say that
this industry is booming yet because I think that most numbers or predictions
given on the microgrid market are probably a little optimistic, but we are
seeing more and more projects,” he says. “And what’s interesting is that they
started in only remote areas, and now projects are developing in other
locations where the grid is weak or where there are opportunities to add
renewable capacity and storage behind the meter.”
Danieli says
regulatory framework in most places still needs to catch up to the advances in
microgrid equipment and technology, but the possibility to install these
systems is now available to utilities and grid managers. “We’ll see more
microgrid systems in the near future, I think, and not just in remote places
such as Alaska, but maybe closer to home, providing service to local grids.”
Reference: http://www.windpowerengineering.com/slider/microgrid-system-stabilize-grid-power-alaska/
