The successful integration of energy storage with wind-power production holds great possibilities for the industry. Storing wind energy helps even the difference between the electricity supply and demand, and creates additional revenue streams for wind-plant owners.
Dan Girard • Director, Business Development • Renewable Energy and Energy Storage, S&C Electric Company • www.sandc.com
The 11.5-MW MinWind Energy LLC wind plant in Luverne, Minn. helped address concerns regarding how well a storage management system would integrate with wind energy in the real world.
One of the barriers holding back broader adoption of wind energy is the impact it will have on electric power grids. As a variable resource, wind energy acts differently than the conventional generation sources managed by most grid operators. Wind energy production is also subject to rapid, somewhat unpredictable fluctuations in output, which can impact the stability of power grids, creating control problems for grid operators and reliability issues for customers. As a result, many electric utilities and transmission system operators have developed stringent grid-interconnection requirements to mitigate the impact that wind energy resources can have on the power grid. If a wind farm does not meet interconnection requirements, it faces mandated production curtailments, limiting plant productivity and profitability.
Natural gas is often cited as a complementary resource that, when paired with wind energy, can ensure a predictable and stable power supply. However, natural gas generation is a carbon-emitting energy source. It is also prone to significant cost fluctuations as the price of natural gas rises and falls due to shifts in global demand as well as supply availability. Concerns about future regulations on hydraulic fracturing technology (or “fracking”), for instance, have raised questions about the future price and availability of natural gas. For these reasons, there is continued interest in other approaches to address the variability issues associated with wind energy.
An emerging technology, however, holds great potential to accelerate the adoption of wind energy resources, without the drawbacks of natural gas. Energy storage can help address the intermittency issues of wind energy and make wind generation perform more like conventional generating plants. In the process, energy storage can also help wind-plant operators create new revenue streams and maximize plant profitability.
Making wind plants act like conventional generating plants
The main priority of grid operators is to maintain a stable, reliable power system. Conventional power plants provide a number of functions beyond power generation to ensure power grid stability, such as contingency reserves to maintain generation and load balance. Frequency regulation is another important ancillary service of fossil fuel-fired power plants—one that is crucial to maintain a stable power grid. With energy storage, wind energy plants can offer similar capabilities to grid operators, and can thus duplicate the functionality typically available from conventional power plants. By providing these additional functions, wind energy plants can foster much greater utility acceptance of wind energy resources.
First and foremost, energy storage helps utilities balance electricity supply and demand. It stores excess wind energy generated when demand is low and can be easily dispatched when needed. There is no time lag waiting for stored electricity to come online, as there can be in starting up conventional generating plants to meet higher than anticipated demand. In this respect, energy storage makes wind a more flexible energy source, letting grid operators react and adjust quickly.
Energy storage also makes it practical to reliably predict and schedule wind plant output, much as it’s possible to schedule output from conventional power plants. Plant operators typically need to schedule outputs in advance, about 14 to 36 hours. Energy storage can also provide wind leveling, which assures that actual plant output matches scheduled output. If actual wind output is below what was scheduled, the energy storage makes up the difference with energy stored when demand was low. In this way, energy storage enhances the ability to predict plant production. The batteries can also store excess wind generation when actual output exceeds what was scheduled, so the electricity can be sold at a later time.
Ramp-rate control, usually provided by conventional power plants, is another important consideration for wind plants. Energy storage can counter increases and decreases in wind plant output, and give power system operators more time to react to output changes. This smoothing function improves overall grid efficiency and power reliability.
In 2009, S&C installed its 1.0 MW smart grid storage management system for Xcel Energy’s Wind-to-Battery Project. To date, the project has been successful in delivering energy when needed.
Finally, energy storage can provide frequency regulation. Frequency regulation is an ancillary service typically provided by conventional generating plants, and it’s a necessary function to protect the reliability and stability of power grids. Grid operators must continually balance electricity supply and demand in real time to maintain the frequency of the power grid. In addition, a battery-based energy storage system operates more efficiently than a traditional power plant when it comes to frequency regulation. Traditional generators balance grids by speeding up or down, a process that consumes energy and results in greater carbon emissions.
Addressing grid interconnection requirements
Many transmission system operators have implemented strict grid interconnection requirements to ensure that fluctuations in wind energy generation do not impact power grid reliability. If these interconnection requirements are not met, wind plants may face production curtailments, and in some cases, they may not be able to sell any electricity generated at the plant.
Reactive compensation solutions that provide rapid response, such as dynamic static compensators (DSTATCOMs), have proven effective at mitigating some of the impact on power systems. DSTATCOMs provide VAR support, but real power is needed to level electricity generated by wind energy plants.
Energy storage, a source of real power, provides another approach to meet grid interconnection requirements. It provides the real power along with a fast response needed to firm voltage levels and effectively fill gaps created by large voltage swings and fluctuations. It offers the potential to provide a more complete solution to these grid interconnection requirements while also delivering additional capability.
Increasing plant profitability
Energy storage can do more. For example, it gives wind-plant owners a new tool to maximize plant revenues and plant profitability. It also gives wind plants the capability to meet demand at any time of day—particularly during peak demand when power prices are typically at their highest. Energy storage lets plants store energy generated off-peak so it can be sold when demand is high, regardless of whether the wind is blowing.
Energy storage also provides wind plants the ability to sell ancillary services such as frequency regulation to transmission system operators, and, thus, opens a potential new revenue stream. By providing such services, along with functions to help protect power grid reliability, energy storage can offer a solid return on investment for plant owners. On a larger level, this helps make wind a more attractive option for generation. Flexibility and profitability are crucial for boosting investment in clean energy resources.
S&C’s battery storage capabilities at the Santa Rita Jail in Dublin, California including PureWave SMS. It lets the jail purchase power during non-peak hours from a local utility and store the reserves. This microgrid support will save the jail nearly $100,000 per year.
Real-world proof
Wind-energy storage is a new technology, but it is showing great promise in real-world renewable energy applications. The most prominent example is Xcel Energy’s Wind-to-Battery project initiated in 2009 and based in Luverne, Minn., at the 11.5-MW MinWind Energy LLC wind plant. This project was intended to help address questions about what storage can do to integrate renewable energy generation in a real-world context. The project used a 1.0 MW (7.2-MWh) sodium-sulfur, or NaS, battery-based system connected to the grid via an S&C PureWave storage management system, which managed battery charging and discharging.
The project has demonstrated that energy storage can be effective in delivering a wide variety of functions, including time-shifting energy, wind smoothing, and dispatched wind-leveling. Batteries were also evaluated for frequency regulation capabilities.
Despite wind variability, the project demonstrated that it needs a relatively small amount of power and energy to better integrate a wind plant with the power grid. For instance, roughly 15 to 20% of a wind plant’s nameplate power rating and just 2 to 3 hours of battery storage makes the wind plant look like a traditional dispatchable resource.
The Wind Energy Institute of Canada also recently initiated a project to evaluate the benefits of energy storage when used with wind energy. They are installing a 1 MW (2 MWh) energy storage system at their Wind R&D Park on Prince Edward Island, featuring sodium nickel chloride batteries connected to the power system by S&C’s PureWave SMS. The project will demonstrate the ability of energy storage to store excess energy in times of low demand and to supply it for use in times of higher demand, along with other functions. The institute anticipates that this demonstration of wind-energy generation with storage will facilitate the integration of more renewable energy into the generation mix.
Energy storage applications in microgrids are also growing. Chevron Energy Solutions recently completed a microgrid system serving the Santa Rita Jail in Dublin, Calif. The microgrid serves the 113-acre correctional facility and combines wind, solar, and fuel cell energy sources, along with emergency diesel backup, to generate electricity for the facility. An energy-storage system plays an important role in the microgrid. When the facility is off the local utility grid, the energy stored balances the microgrid’s load with the total power generated from on-site sources by automatically and instantly storing energy generated that is in excess of load requirements. The energy-storage system also supplies electricity when demand exceeds the output of onsite generation sources. WPE
A promising technology to accelerate wind energy adoption
Energy storage continues to show great promise to help wind-plant developers, owners, and operators overcome barriers to acceptance of wind energy. It lets wind energy plants perform like conventional generation plants—and even offer better output control—while meeting requirements set in place to ensure wind plants don’t adversely impact power system reliability. Furthermore, by increasing plant productivity and offering new revenue streams, an energy storage investment can also improve financial returns for a wind energy plant. This may be a high hurdle as the industry prepares for the day when the U.S. production tax credits expire and wind has to stand on its own. As such, energy storage technology complements new and existing wind energy plants, and plays an important role in the industry’s ability to compete and serve as a high quality, modern generation source.
Filed Under: Energy storage, Featured, News, Turbines
A Stanford paper published a month before this article suggests that battery storage of wind generated power is not an efficient solution. Better to shut down the turbines when the power is not needed. Makes one wonder if we are being practical even building any wind turbines until we have a good method of storing the energy and redelivering to the grid when needed
Battery storage will significantly up the already large subsidies wind companies get. Although it does have some benefits, it’s still a waste of subsidies because many days pass with low to no output from wind turbines. I’ve monitored the output from thectyrbine in Lewes, DE and other installations. Wind energy is a very expensive joke.
Using energy storage to levelize the output of an individual wind plant is inherently sub-optimal and wastes resources. It makes about as much sense as installing a battery in conjunction with every toaster. After all, toasters are a very intermittent load.
A former colleague performed a careful study of applying storage with the wind plants on one of the iHawaiian Islands. If the storage is located with each plant and deployed to levelize each plant on an individual basis, the total amount of storage required is an order of magnitude greater than if the storage is deployed to levelize the aggregate of all the wind plant. In a much larger grid, such as one of the three major grid interconnections in the continental US, the difference between individual plant levelization and system-wide levelization would be far, far greater – perhaps many orders of magnitude greater resource requirements for the individual approach. In addition, individual levelization creates substantial energy waste due to the rather significant round-trip losses of storage. The strength of the interconnected power grid is diversity, and the short-term variations of individual plants are quite diverse. All the grid needs is for the aggregate of both load demand and variable generation output to be smoothed, and this is most efficiently done on a system basis.
There may be a time in the future when renewable penetration is so great as to require storage to manage the variability. However, it is presently far more efficient, both economically, and in terms of carbon emissions, to use gas generations flexibility to balance renewable plant and load variations. The natural gas plants are operating anyhow, and the efficiency penalty for these plants to vary output to follow net load (load minus non-dispatchable renewable generation) is quite small compared to the rather large round trip losses of energy storage. To state this differently, where fossil generation remains in the mix, using energy storage increases the amount of fossil generation output, in order to cover the storage losses. So storage is quite “brown”, not “green” as commonly believed.
How about some old fashioned storage at most of the places where the wind blows? All you need is at least 30 meters vertical difference and water, something present on a lot of wind farms that already have the electrical infrastructure in place. For most Great Plains sites, it costs much less than $1.00 per watt, installed.
Dear Mr: President,
My name is Luis M Carion from Puerto Rico, I am the inventor of a turbine that use compressed air for mechanical rotation. Compressed air may come from sea wave, solar energy and wind. Compressed air may be storaged and use later for electrical generation. I would like to bring this new technology for commercialitation.Please take a minute for your evaluation. Thanks.
http://www.iaergpr.com/projects/power-generation-by-buoyancy-prime-mover/
Att: Luis M Carrion
Carrion Turbine
Inventor
USA patent: US8151565B2