The Wind Power Storage Issue

Storing the energy from wind is obviously useful.  But is it essential?  Numerous studies cover the matter both asserting that storage can useful and asserting its not.  The practical common result is the continental U.S. could increase wind energy production another ten times before the capacity would merit storage at scale.

It’s just not that simple.  In Hawaii where the ocean limits interconnection over a wide area the local conditions rule.  To get to high wind use a buffer needs to be in place between the source, the wind and to the consumer.  Hawaii has a 70% renewable target and to get there some form of moving energy production from the time it’s generated to the time it’s used has to be in place.

But numerous studies as well as European wind integration experience have demonstrated that in the continental 48 states the use of wind energy could increase by more than 10-fold without energy storage.  The opportunity is in using the sources of flexibility that are already present on the electric grid. Every day, grid operators constantly accommodate variability in electricity demand and supply by increasing and decreasing the output of the flexible generators – power plants like hydroelectric dams or natural gas plants that can rapidly change their output of generation.

The peak demand is met by the stored energy in the dammed water or the natural gas in the tank or pipeline.  Grid operators also move power from regions with momentary excesses of electricity to other regions that have a need for electricity at that moment. Grid operators use these same flexible resources to accommodate any additional variability introduced by wind energy.

In the U.S. now, demand for electricity can vary by a factor of three or more depending on the time of day and year, which nationwide translates into hundreds of gigawatts of flexibility that are already built into the power system.

Its almost always much cheaper to use the existing flexibility than to build new sources of flexibility like energy storage facilities.  When the existing sources of flexibility are eventually saturated, a number of additional low-cost sources of flexibility can be deployed, such as building additional transmission lines, encouraging additional demand response resources, reforming grid operating procedures, or making the generating fleet more flexible.

Continuing advances in energy storage technology can make it more economically competitive as a provider of grid flexibility.  Its important to remember that resources like wind energy can already be cost-effectively and reliably integrated with the electric grid without energy storage for quite some time to come.

Compare that to Hawaii’s plan to install a 15-megawatt battery on a new 30-megawatt wind farm.  Computers will work to keep the battery exactly half-charged most hours of the day. If the wind suddenly gets stronger or falls off, the batteries will smooth out the flow so that the grid sees only a more gradual increase or decrease, no more than one megawatt per minute at some hours of the day.

The Hawaiian installation is designed to succeed at a crucial but obscure function: frequency regulation. The alternating-current power system has to run at a strict 60 cycles per second, and the battery system can give and take power on a micro scale, changing directions from charge to discharge or vice versa within that 60th of a second, to keep the pace steady.

The battery system can also be used for arbitrage, storing energy at times when prices are low and delivering it when prices are high. It can hold 10 megawatt-hours, which is as much energy as a 30-megawatt wind farm will produce in 20 minutes if it is running at full capacity. That is not much time, but it is huge in terms of storage capacity. The reason for the arbitrage?  Publicly disclosed figures put the project in the range of $130 million, with about $10 million for the battery. The Energy Department has provided a $117 million loan guarantee.  Folks in Hawaii are going to pay, but the cost of the investment will be lower with all of the U.S. backing the plan up.

Isolated power systems like Hawaii’s seem like highly unique cases, since geography prevents them from sending excess electricity to neighboring regions there is limited access to sources of power system flexibility, the power grid is often weak, and the price of electricity is often high.

The success of countries like Spain, Germany, Denmark, Portugal, and Ireland reliably and cost-effectively obtaining 10% or more of their electricity from wind farms without adding any storage resources is instructive.  As well, the main grid operator in Texas has regularly obtained 20% of its electricity from wind energy, also without the use of energy storage.

The National Renewable Energy Laboratory summed the matter up in a remote quote, “At present levels of wind penetration on the electrical grid, storage has not been a priority consideration. But eventually, as system resources and not exclusively due to wind or other renewable resource capacity adds on, the nation’s electrical grid will benefit from energy storage technologies. Essentially, the power system already has storage in the form of hydroelectric reservoirs, gas pipelines, gas storage facilities, and coal piles that can provide energy when needed. Today, storing electricity is more expensive than using dispatchable generation. In the future, through, advances in technologies such as batteries and compressed air, energy storage may become more cost-attractive.

The point is that Hawaii is an isolated set of islands that needs to store back energy production and move it to the time its needed.  The other side of the point is, as the renewables become a larger proportion of the total, the continental U.S., as big as it is, is a set of islands as well.


Original post: New Energy and Fuel

Wireless Sensor Networks: 5th European Conference, EWSN 2008, Bologna, Italy, January 30-February 1, 2008, Proceedings


Produit DescriptionThis book constitutes the procedure arbitrated from 5 º Atelier European on the Networks of sensors inal

Ultracapacitors Ready for Power Storage

When you couple ultracapacitors with lithium batteries performance of an electric vehicle is dramatically boosted. Ultracapacitors give electric vehicles the instant response needed to get going, recover braking energy, work across a wide temperature range, and charge very quickly for thousands or millions of cycles.  There is more out there than Eestor, and some are going to market right now.

San Diego-based Maxwell thinks it has a cost-effective solution for carmakers. The company makes the K2 2000 ultracapacitor a unit about the size of a soda can that could be of excellent strategic use with electric vehicles.  Maxwell Technologies is supplying a major European automaker that expects to release a hybrid vehicle this year that couples advanced batteries with the company’s ultracapacitors.

Maxwell's Ultracapacitor. No larger image available.

Maxwell is suggesting they have a partner in the European deal, the $30 billion Continental AG parts supplier, who is a competitor to Bosch in Europe. Continental expanded recently with acquisition of another high-profile European auto supplier, Siemens VDO, in 2007.  These are not firms that go to market with immature technology.

Maxwell CEO Dave Schramm said of the project, “They’re ramping up the car now,” adding that he expects the model’s volume to double by 2012. “We’re already shipping product.” Schramm said that starting the car’s gasoline engine, especially in cold weather, is the largest load batteries go through. Ultracapacitors allow a much smaller pack. “We’re definitely taking cost out of the system,” Schramm said. “Batteries don’t like the kind of power spikes you get with the start-stop cycle, but that’s the way ultracaps work best.”

The primary driver for Maxwell is the European fuel economy standards, which strongly incentivizes “start stop technology” where the engine is always shut down for a stop.  The technology is expected to be employed across Europe in the majority of new cars by 2015 in addition to the “Micro-hybrids” that are already selling well. For the U.S. start stop isn’t likely, as the fuel economy advantage isn’t credited by the EPA’s system –no incentive payoff – technology denied.

Maxwell’s ultracapacitors are installed in about 2,000 hybrid buses with regenerative braking.  The firm is involved in the Ford Transit Connect electric van with Azure Dynamics.  These and other automotive ultracapacitor projects have pushed Maxwell sales from $57 million in 2007 to $100 million in 2009.

Meanwhile, Eestor has gotten its saga into trouble.  Words like ridiculous, mystical and sham are coming out from various writers.  The hard facts are Eestor has missed its own promise to introduce and show the world a working ultracapacitor by the end of last year.  Now that a full calendar quarter has passed and most of another month, the credibility matter is the lead Eestor item for news and blogs.  To add injury to the situation, a major source of information, the tiny ZENN Motors, has stopped building their cars entirely, leaving the firm with nothing other than its license with Eestor for any form of revenue.  ZENN seems to dream of being the sole supplier of Eestor ultracapacitors to automotive capacitors.  The question is quickly becoming will there be a ZENN at all if the Eestor products do come to market.

Technology never waits, even when you’re Eestor.  Last week saw Popular Science cover the “Electric Luxury Racer” an exercise in engineering with the latest technology.  Of note the vehicle sports a graphene-based ultracapacitor—a device currently being developed in university labs, which uses sheets of carbon only one atom thick to store twice as much electricity as today’s capacitors offering immediate bursts of power.  The question is will the unnamed university labs come up with production prototypes.  Doubling capacitor storage might not get the idea to ultracapacitor status, but graphene-based caps seem quite possible.

The face of the capacitor market is changing fast.  Ioxus of Oneonta New York has announced 1,000-, 3,000- and 5,000-Farad (F) ultracapacitors.  These are quite different numbers from micro or pico farads.  Ioxus prides itself with smaller dimensions packed in rectangles that offer more power density than the competition.

Ioxus Ultracapacitors. Click image for the largest view.

Right now ultracapacitors can be used as rechargeable energy storage devices to prolong the lifespan of other energy sources, such as batteries. They are lightweight, weighing one-fifth the weight of a comparable battery, and their manufacture and disposal has no detrimental effects to the environment.

Ultracapacitors can take on all of the power functions, except for extended time operation, and this is actually only dependent on the ultracapacitor system size.  The state of charge of the battery array does not affect the characteristics of ultracapacitor energy delivery capability.  Due to buffering by the ultracapacitor array, the battery array is not subjected to large current loading, which makes its operating conditions, under all conditions of line and load more moderate, extending the battery life.  It’s very hard to imagine a smart electric power storage system without ultracapacitor support.

One of the more interesting capacitor applications can be seen on the Ioxus site where they offer a white paper about capacitor use for starting diesel locomotives in Russia.

Will Eestor get from stealth mode to supplying working samples to amaze and impress all of us?  Time will tell, but a near four-month delay on a one’s own announcement doesn’t encourage folks.  In the meantime there are ultracapacitors out there.  Maybe the available products are not so amazing as the Eestor leaked power, but the real products are intensely valuable for supporting electrification of transportation.


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Wireless Sensor Networks: 6th European Conference, EWSN 2009 Cork, Ireland, February 11-13, 2009, Proceedings


This book constitutes the refereed proceedings of the 6th European Conference on Wireless Sensor Networks, EWSN 2009, held in Cork, Ireland, in Februar 2009. The 23 revised full papers presented were carefully reviewed and selected from 145 submissions. The papers are organized in topical sections on performance and quality of service, routing, coordination and synchronisation, data collection, security, as well as evaluation and management.
Wireless Sensor Networks: 6th European Conference, EWSN 2009 Cork, Ireland, February 11-13, 2009, Proceedings