A lithium-ion energy storage system specially equipped with a ‘cold temperature package’ is helping an Alaskan community make the most of its wind resource, writes Jim McDowall
Energy storage system at Kotzebue, Alaska
Until recently, the city of Kotzebue in Alaska relied on diesel generation for its main power source. The community of more than 3000 people lies 30 miles north of the Arctic Circle and is not connected to a transmission grid.
Its electricity cooperative KEA (Kotzebue Electric Association) has made use of wind turbines since the late 1990s to hedge against high and volatile diesel prices. This strategy has brought success: in 2015 its wind turbines enabled KEA to cut its diesel consumption by 250,000 gallons and save $900,000.
Energy is essential to the survival and viability of communities in the far north and KEA recognizes the impact of rising diesel prices – its fuel bills rose from $1.5 million to $6 million between 2002 and 2008.
To counter such volatility, KEA is committed to making every conceivable effort to reduce its dependence on diesel and has invested in wind energy.
However, the intermittent nature of the wind means that KEA has often had to curtail wind output and needed solutions to utilize the excess wind capacity. This was especially noticeable during the summer nights when community loads were low, but could happen any time of the year.
It’s a rule of thumb that microgrid operators can optimize fuel savings without a battery when penetration (the proportion of the load that is supplied by renewables at any instant) is below 50 per cent. When penetration rises above 50 per cent, an energy storage system (ESS) is essential to maintain grid stability.
If penetration exceeds 100 per cent, when wind power exceeds demand, that same ESS can shift wind energy to help minimize curtailment. In KEA’s case, its wind capacity of 2.9 MW is almost equal to its peak load of around 3 MW, making energy storage essential.
So, in 2015 KEA commissioned a Saft Intensium Max+ 20M ESS to achieve the full potential of wind by riding through fluctuations in wind output and time-shifting wind energy.
In addition, the operator had the goal of operating in diesel-off mode, where it would rely only on the combination of wind and storage for several hours at a time during periods of high wind and low load.
As a battery technology, lithium ion (Li-ion) has several advantages for KEA. Firstly, because it can react quickly to changing supply and demand, Li-ion is particularly well suited to riding out variations in wind output from seconds to hours, matching the intermittent breaks and gusts in wind power. Li-ion performs predictably over a large number of charge and discharge cycles. This translates into a calendar life of 10 years or more.
In addition, its high energy density combined with the low weight of lithium means that Li-ion batteries are relatively small and lightweight, providing close to 1 MWh of energy in a single six-metre container and with a power capability of up to 2 MW. Intensium Max containers can also be shipped fully assembled and factory tested, thus minimizing the work that has to be performed on-site.
Installation is also straightforward. Saft delivered the Kotzebue battery as a fully integrated system with battery modules, battery management systems, temperature control and safety systems. The ESS includes a 1.2 MW power conversion system (PCS) and grid connect transformer supplied by ABB, housed inside a generator building.
KEA has worked hard since the 1990s to develop wind infrastructure that works in the harsh conditions of the Arctic. Maintenance can be very challenging or even impossible when temperatures drop to -50à‹Å¡C and annual snowfall exceeds one metre. Equipment must be extremely rugged to operate reliably.
Saft designed KEA’s battery container with a ‘cold temperature package’ that combines advanced insulation material with a hydronic heating coil. The coil uses the same hot glycol solution that maintains the diesel gensets at their operating temperature.
Logistics were a challenge as Kotzebue is not connected to a road network. Being situated to the north of the Seward Peninsula that reaches out towards Russia, its port is restricted by sea ice for more than nine months of the year. As a result, the city is only served by three freight barges per year. Saft had to ensure its ESS was on board the last of the 2015 barges to meet KEA’s milestones for installation and commissioning.
The PCS can deliver continuous power of 1.2 MW and up to the full 2 MW battery capability for short durations, giving KEA the ability to stabilize the network if wind generation ramps up or down suddenly.
Cold climate maintenance is challenging
Normal wind ramps are handled by the ESS controller, which manages charge and discharge and has latency in the region of 100 milliseconds. However, when the inverters detect a sudden drop in frequency, typically resulting from a trip event, they can bypass the controller and inject power in 40 milliseconds to stabilize the grid.
While the ESS power is used for grid stabilization, its energy capacity enables KEA to time-shift excess wind energy to times with higher demand or lower wind output.
With a year of operation under its belt, KEA has reported that it is satisfied with progress and the contribution the ESS is making to the microgrid. The operator is now working towards enabling fully automatic operation, which is an essential step in enabling diesel-off mode.
Solar PV installation at Colville Lake in Canada’s Northwest Territories
Working towards diesel-off
Early experience has been that the ESS has worked well to optimize wind generation as part of KEA’s microgrid. The system has behaved in line with expectations.
From a technical and economic point of view, energy storage has three drivers. The first is that increasing the usage of renewables will reduce the running hours of the gensets. This avoids curtailing excess wind and smooths the power output.
Second, energy storage is being incorporated into the KEA demand control system to replace diesel peaking units and further utilize excess wind capacity. This reduces fuel consumption and reduces wear and tear on the gensets.
Lastly, energy storage brings potential to operate in diesel-off mode. KEA is now reviewing operation with a view to switching diesel generators off completely at times during summer months when low load coincides with strong wind. While the ESS is already allowing KEA to run its diesel generators at optimum efficiency and maximize wind penetration, these savings will be enhanced by reducing the running hours in diesel-off mode.
It’s hard to estimate payback through fuel savings alone, particularly because an ESS is essential for grid stability when operating with more than 50 per cent renewable generation. So it’s not the investment in the storage alone or the fuel savings that KEA is looking at, but the performance of the microgrid as a whole, taking into account greater use of wind energy, a drop in fuel bills and maintenance savings.
Adding an ESS can enable an operator to maximize penetration of renewables but there is no single unit that will meet the needs of all sites.
One thing to consider when specifying a ESS for a site like Kotzebue is the unique set of conditions in terms of wind or solar PV surveys, diesel generation and load patterns. It’s important to use this data to tailor the ESS in terms of its power and energy storage capacity. This ensures an optimized total cost of ownership (TCO) that takes account of the microgrid as a whole.
In addition, without diesel-based spinning reserve being immediately available, it’s important to specify an appropriate control system that can react quickly to sudden changes in generation.
Saft recently delivered another ESS for an Arctic community. Canada’s Northwest Territories Power Corporation (NTPC) has commissioned an ESS for its Colville Lake community, where a single shipping container integrates both the ABB power conversion system and the battery system. That system also has a ‘cold temperature package’ and is part of a solar/diesel hybrid microgrid.
Colville Lake’s 150 inhabitants represent a 150 kW peak and 30 kW base load, which was being met by aging generators. In 2015 NTPC installed new diesel generation and augmented the existing 50 kW solar array to bring its output to 136 kW. The ESS implements full-time grid-forming capability and is rated at 200 kW and 232 kWh.
As for KEA, it is already considering its next foray into energy storage and will no doubt build on the experience from its first Li-ion ESS installation. The operator delivers grid planning for smaller communities in Alaska’s Northwest Borough. The Alaskan Energy Authority has funded the deployment of wind power in two outlying communities with a goal of adding storage using a different grant source.
KEA is also developing 500 kW of solar to be added to their system that will make energy storage even more critical. Solar in the Arctic is viable and NTPC has proved that there’s good solar resource in extreme northern latitudes, especially during the summer months.
Jim McDowall is Business Development Manager for Saft America.
‘The battery market is booming’
Saft chief executive Ghislain Lescuyer on the importance of batteries to the energy market and the sector’s key trends and advances:
Q: Why are batteries so important to the future?
A: The battery market is booming. Energy storage can be found at the intersection of several macro trends that are changing the world as we know it. Whether it is industrialization and urbanization in emerging countries, increased mobility, greater global interconnections or renewable energy, there is a need for energy storage. And batteries are a clean, recyclable and high-performance solution.
Q: What major technological advances are helping meet today’s needs?
A: Today, electrical storage is possible. Saft began producing batteries a hundred years ago. It has grown from manufacturing non-rechargeable batteries for flashlights to learning to charge batteries and increase the number of cycles to store more and more energy to deliver more power. We are now pushing the limits to provide more power under more extreme conditions, using less space and at a lower weight.
Q: What role do batteries play in the key changes that the world is facing?
A: Take the energy transition. Intermittent renewable energies require storage to smooth energy output and balance electricity generation coming from multiple sources. The real challenge of the energy transition will consist in managing production and consumption, where batteries also play a role. Batteries will be key in developing autonomous energies, just as they are essential in creating smart cities, for airline safety, or for communications satellites.
Q: Which areas are seeing battery applications today?
A: Batteries are everywhere, covering all markets. Traditional applications such as those for rail and aviation are evolving. In addition, new applications are arising in such areas as renewable energy, data centres and vehicles. Environment and mobility, to name just a few trends, are driving these needs. At a scale similar to the digital revolution – and parallel to it – more and more people and companies need batteries.
Q: What strategy is needed to meet these challenges?
A: Today, all companies need a differentiated offer. Saft’s strategy is to differentiate through quality and innovation, focusing resources and R&D on high-performance applications tailored to customers’ specific needs. We must make the most of our strengths: we are a world-leading developer and manufacturer of advanced battery technologies for industry. With this as a base, we have a focused roadmap organized by market, offering customers the best solutions from Saft’s full spectrum of possible products for their own differentiation. In doing so, customers reap the benefits of best practices and economies of scale between divisions.