Energy Storage Breaking Through

Harnessing the power of wind and solar

Ken Silverstein | May 31, 2011


Duke Energy is now part of the next wave of clean energy technology: Energy storage, which gives utilities and large industrials the flexibility they need to respond to power shortages and price spikes. As for Duke, it is installing batteries at a wind farm in Texas to harness excess energy there that would be discharged during peak periods.
It is a budding concept, which is considered critical to building out the smart grid. In essence, it would add new efficiencies and thereby make room for alternative sources of power. Utilities may have excess generation that serves to firm up the system in case of a failure, or during peak demand. An energy storage device would give those power companies the latitude to keep that energy when it is not needed and to release it when the demand for it is highest.

According to the Department of Energy, the technology has a lot of market potential and environmental benefits. It can help utilities avoid downtime and thereby save billions in repairs and lost opportunities while also allowing such companies to sell blocks of peak power at premium prices.

Environmentally, it will facilitate the development of more wind and solar power, although the wind power sector says it needs no such leaps to keep growing. It says that wind power simply replaces electricity generated by base-load systems.

Energy storage research is moving forward. In November 2009, the Energy Department said it would put up $22 million to install large-scale batteries to install a 36-megawatt capacity system for Duke’s project there. The utility will invest $22 million of its own money. When complete in 2012, the battery storage system that is being designed by Xtreme Power will be one of the world’s largest.

By comparison, most such trials taking place today store about 1 megawatt. Some are larger as is a project in New York State that is 20 megawatts. That one is being built by Beacon Power and is using flywheel-based storage that can ramp up quickly when supply and demand are imbalanced. 
Altogether, the federal stimulus plan is providing $185 million to 16 energy storage demonstration projects. Meantime, the Energy Department's Office of Science is also working to advance battery technologies.

“Bringing more efficiency and reliability to the grid will help cut costs for consumers and power a cleaner energy future,” says Energy Secretary Steven Chu.

To be clear, storage devices come in many forms: The most prevalent ones today are batteries that are the size of a house. They link to the transmission grid where they siphon off power and store it, such as the one used by Duke. That process can occur at night when the cost of electricity is lowest and it can be dispatched during the day when prices rise. Then there’s the fast-response flywheels, and a deviation of that called kinetic energy storage that is practical for short-term needs.

Beyond those tools, there's also compressed air energy storage that holds air underground and releases it in heated form to create electricity. And there’s the mature pumped hydro storage, whereby turbines push water into reservoirs at night and then let it go during the day when demand is highest.

The younger products are now relatively expensive and it is still unknown how they would operate in a commercial setting. If they are to be cost effective, they must be able to offer other services, say experts. Until then, the federal government will partner with private industry to help foster this sector.

Recently, the Energy Department awarded a $17 million loan guarantee to AES to support the construction of a 20-megawatt capacity energy storage system using lithium-ion batteries. The project is purported to bring about efficiencies to the grid in Johnson City, New York, allowing more room for green electrons. It will also reduce carbon emissions, AES says, by storing the energy and using it later -- as opposed to firing up a fossil fuel plant to kick in when the wind is not blowing.

Balancing the electricity load is a difficult job. Storage devices, if they can be shown to work at commercial scale, would be a huge boon to an industry -- and an economy -- trying to advance renewable power.

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Related Topics


how can we separate hydrogen from air or water

Question:how can we separate hydrogen from air or water and also how hydrogen is used as a fuel

Answers:Hydrogen is very reactive and combines with other elements such as oxygen to form other compounds, most commonly water when it combines with oxygen. It requires approximately 50 kilowatt hours of electricity to separate from water an amount of hydrogen with the energy equivalent of one gallon of gasoline. When that amount of hydrogen is used in a fuel cell you recover approximately 15 to 18 kilowatt hours of energy. The process is relatively inefficient and you have a rather large net loss of energy. Where electrical energy is used to produce hydrogen for use as a fuel is at night when you have a large excess of generating capacity and that electrical energy would otherwise be wasted. This is done in France where over 80% of their electricity is produced in nuclear power plants. At night they use the excess generating capacity to produce hydrogen which is then used in buses the next day. If you use the electricity to produce hydrogen you recover some of the energy. A more efficient process would be to use excess generating capacity at night to charge the batteries of electric cars.

Can't store MW

Ken, when talking about the storage, could you please use units of energy?    I understand that you're not the only energy writer who is a little casual with units, but the practice can confuse the public and even some specialists.  

For example, in this article, it is said that Duke is installing a 36 "MW" capacity storage system.  MW is a measurement of power -- the rate of energy transfer.  Batteries store energy, not its derivative, which I'm sure you know.  But a non-technical reader should be forgiven for thinking that if a 36 "MW" battery is hooked up to a 36 MW wind farm, then, since the numbers are equal, the problem of wind variability is solved.

In reality, I suspect -- but cannot know -- that the battery said to store 36 "MW" can only store minutes or less of this wind farm's peak prouction.

But if you'd use a unit of energy, like joules or MW-hour, then we could figure out what you meant.

Distribution is the key

Adding storage optimizes the value and accessibility of renewables. But distributed generation and storage, as provided by the Sunverge Solar Integration System, brings the value proposition into focus at a mass scale.

Combining a grid-tied PV array with a hybrid inverter, lithium-ion storage and gateway interoperability in a self-contained residential unit, Sunverge delivers the advantages of capacity firming and demand response by aggregating the stored energy of a neighborhood, a community or a whole region of ratepayers – while saving the homeowner up to 70% on annual energy costs. Since launching earlier this year, Sunverge is slated for installation in net-zero developments in California and Pennsylvania, while statements of work are being finalized with a half-dozen national industry leaders in Distributed Energy Resource and Demand Response.

How can you say that?

What were you thinking!!!!   Take away wasting more Federal Resources from what should come out of a for-profit company's stock holders as R&D, not it's rate payers and tax dollars. How ludicrous to not waste our Federal Dollars to line a few more pockets...  it's not the Dysfunctional American Government Way...   

Storage is an Expensive Luxury

There has indeed been a lot of focus on storage, but it is still far too expensive compared with alternatives.  The Duke Energy project will spend $44 million for 36 MW of batteries, or around $1200/kW.  That's roughly the cost of a new combustion turbine, but Xtreme's lead-acid battery systems have unknown costs and an unknown lifetime.  Lead-acid batteries are notorious for limitations on their ability to deep cycle.  Moreover, lead-acid batteries are probably the cheapest storage technology currently available.

At this stage, industry and government need to focus on reducing costs, increasing storage densities and improving operating life.  Building lots of expensive storage that is likely to be superceded by significantly better alternatives in a few years is a waste of money that will eventually have to be repaid by consumers.

In the meantime, there are those alternatives....

Jack Ellis, Tahoe City, CA

How about Fuel Cell

Hi, I think Hydrogen can play a very important role in energy storage, that is,using extra energy from wind, solar to produce h2, and then when needed, transform h2 to electricity by means of fuel cell.