Does Wind Need Energy Storage?
Posted August 27, 2009 in Solving Global Warming
With the recent news of PG&E's bid for stimulus funds for compressed air energy storage (CAES) to balance wind, the question again arises whether energy storage is really necessary to put wind and other variable renewables on the grid. I believe the answer is a qualified yes.
On the one hand, it has become almost cliché to call energy storage the holy grail of renewable energy and recently it seems the space is getting increasing levels of interest from investors, lawmakers, and venture funds alike. However the wind industry itself has been quick to downplay the importance of storage. In response to another recent piece on CAES Michael Goggin of the American Wind Energy Association suggested that "it's important to temper enthusiasm about storage with the recognition that wind power can be integrated onto the electric grid without energy storage."
The truth is that today wind is only about 2% of the US electricity supply, and at current levels of penetration wind can often be readily integrated without impacting system reliability. But wind power is growing quickly, and if it is to be a part of our nation's solution to global warming, it must continue to do so on a big scale. This means in the long term we will need every cost-effective means at our disposal to integrate renewables. This includes aggregating diverse resources (geographically distributed wind, wind and solar, etc), demand response, careful use of hydroelectric and natural gas plants that ramp quickly to balance wind's fluctuations, and yes, energy storage.
Technologies like CAES have important, unique advantages. For example, storage can be used to provide more constant power output to fill power lines. Ultimately, that means that for each unit of wind power, we need less high voltage transmission capacity, and ultimately that means less "energy sprawl". Furthermore, if wind and storage can displace coal directly by producing baseload power, that increases the greenhouse gas abatement value of wind substantially.
While there is some degree of hype in the recent buzz around these technologies, its clear storage will provide real benefits to the system as the contribution from variable renewables continues to grow. And although the variability of wind is not a barrier to its growth today, energy storage could nevertheless play a critical role in paving the way toward a clean energy future.
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Comments
Michael Goggin, American Wind Energy Association — Aug 28 2009 07:13 PM
Thanks for covering this topic on your blog Samir – it’s great to have a friendly discussion of the issues to help clear up some of the misconceptions out there about how wind is integrated with the electric grid. AWEA’s main concern with energy storage being presented as the “holy grail” for wind integration is that some energy storage advocates tend to over-sell their product by claiming that wind on its own is unreliable and therefore storage is essential for wind integration. In reality, large amounts of wind are reliably being added to the grid today without any new storage being built, and wind integration studies and operating experience from around the world indicate that we can add much more wind without storage becoming necessary.
At the same time, the wind industry is more than happy for people to build storage, since as you note it is one tool that can facilitate wind integration. Of course, as you also correctly note, other tools like demand response, combustion turbines, more efficient grid operations, changing grid rules to make the grid less balkanized, making existing generating plants more flexible, and most importantly building transmission are also great for helping to integrate wind. The fact that these tools are being used today, while commercial-scale storage is not being built, leads us to think that in the current market these other tools are more cost effective. For a longer discussion of AWEA’s views on energy storage, please see: http://www.awea.org/pubs/factsheets/Energy_Storage_Factsheet.pdf
While you are correct that storage can be installed on a transmission line serving a wind or solar plant to increase the utilization rate of that line, building a marginally higher-capacity line would be a much lower-cost solution. For example, increasing the voltage of a transmission line from 345-kilovolts to 765-kilovolts increases the amount of power that can be carried over that line by a factor of 6, while the cost only increases by a factor of 3 and land use only increases by 33%. In addition, the higher-capacity line is about 10 times more efficient than the lower-capacity line.
It’s also important to remember that energy storage alone cannot bring on large amounts of new renewable resources – only transmission can do that. Since almost all of our best wind and solar resources are located in parts of the country where there is no electric grid at all, building transmission is the only way to access those resources.
I’d also take issue with the idea that we need storage so that wind can more effectively displace coal generation. In fact, wind energy is ideally suited for displacing coal power, and in many regions it has begun to do so drastically already. Because it is very difficult for coal plants to change their level of output, adding large amounts of wind to the grid puts coal plants at a major disadvantage versus power plants that can better change their level of output, chiefly lower emitting natural gas plants. For those who are interested, here’s a more in-depth discussion of that topic:
http://www.awea.org/pubs/factsheets/Baseload_Factsheet.pdf
There are also some interesting studies in Europe showing that, until a power system gets to very high wind penetrations (>50%), the net effect of adding energy storage is actually to increase CO2 emissions since it chiefly allows coal plants to run more and displace more gas generation. Here’s an interesting one from Ireland: http://elecrc.ucd.ie/files/slideshows/2009_01_12/Aidan_Tuohy.pdf
Thanks again for posting Samir – let’s keep this constructive discussion going.
Michael Goggin, American Wind Energy Association
Joe Spease — Aug 29 2009 12:39 PM
My company, Windsohy, is developing wind/CAES projects in the Midwest. We believe that wind/CAES will increase development of new wind projects while at the same time reducing the need for new coal or nuclear plants. Our baseload wind projects can come on line quicker than the long-term planning and construction timelines for EHV transmission line projects, which will allow for quicker acceptance of new wind projects by power purchasers. We also disagree with Mr. Goggin about the issue of displacing coal generation. Wind/CAES is the far quicker way to displace coal power on the grid. The idea of building 20 GW of wind in widespread geographic locations, with power distribution coordinated over multiple RTO's to serve as baseload power SOMEWHERE at a certain time (a system that does not exist) does not compare to the simplicity of wind/CAES doing the job right now within the existing infrastructure.
AWEA's opposition to wind/CAES makes absolutely no sense. Our projects will expedite wind project development quicker while at the same time displacing coal IMMEDIATELY, to better answer the pressing needs for CO2 reduction expressed by the Intergovernmental Panel on Climate Change.
Samir Succar — Aug 31 2009 09:27 AM
Michael,
Thank you for your thoughtful comments. While it is true that bulk storage is not currently being deployed on a large scale, this might not be a reflection of its ability to provide cost effective wind balancing. Rather I strongly suspect there may be other reasons why we haven't seen more storage projects to date, such as problematic and unclear market access rules for storage, the lack of clear designation of storage as either transmission or generation assets on the grid, the specific expertise that this kind of development requires, the historic risk aversion of most utilities and the low average wind penetrations throughout most of the country.
The points you make about the small land use benefits from downsizing lines are well taken in the context of a single line, but taken in the context of a large development of wind over the next few decades, the impact of storage to mitigate transmission needs could have extremely important value in the aggregate. Summed over hundreds of GW's of wind, storage could play an important role (together with demand response, etc) in reducing the amount of transmission we ultimately need to deliver that wind energy to market. I don't argue that we don't need transmission, but as I've mentioned in prior posts, we have to build that infrastructure in the right way and that also means using all the tools at our disposal so we don't build more lines than we need nor disturb more land than necessary.
I'd like to make a clarification on the issue of displacing coal; this gets a little subtle, but the point is critical. Certainly in areas where coal is on the margin, wind is displacing that generation when it is able to compete in economic dispatch. However the issue is the extent to which wind can actually displace new capacity. This has a great deal of value since each new plant embodies 30-60 years of guaranteed emissions. Wind by itself gets very low capacity credit because output tends to be lowest on those hot august afternoons when the grid needs power the most. This means it takes a lot of wind to displace conventional, dispatchable generation. Having a more flexible system (through, again, demand response , etc) will certainly improve the capacity credit (ELCC, etc) of wind, as will resource aggregation and the rest, but I believe storage has a role to play as well. With the very old coal fleet we have in this country, the ability of wind to provide intermediate or baseload services to the grid will be increasingly important. I'm not saying storage is the only way to get there, but it can certainly play a big role.
Joe - Great to hear about new developments from Windsohy. Great point on transmission development timescales relative to storage.
Thank you both for your comments!
al cavallo — Aug 31 2009 11:08 AM
“It’s the vision thing.”
If our vision is to reduce fossil fuel consumption drastically (80% or more) using intermittent energy resources, storage (specifically, CAES) must be an integral part of our energy supply system.
An 80% or more reduction is technically feasible using CAES; power from a wind/CAES/transmission system will be affordable although more expensive than from cheap coal and cheap natural gas.
Utilities are already worried about fossil fuel prices, not availability. They actually remember what happened in the first seven months of 2008, that not only oil but also natural gas and coal prices increased dramatically. As one power company executive stated at EP 2009, “If China is willing to pay more to Peabody Coal than I am, that coal is going to go to China.”
CAES should be presented as a central part of our long term vision. If it is not, nuclear power, never shy about pushing its ideas forward, will have the future to itself. Consumers will not tolerate freezing in the dark.
Craig Severance — Aug 31 2009 04:12 PM
This is a good discussion among informed players. I would like to add two resources, and a comment.
Direct rebuttal of the propaganda regarding wind's intermittency and rebuttal of assertions wind is therefore a poor energy resource:
"The Wind Does NOT Blow Only 1/3 of the Time" here:
http://energyeconomyonline.com/When_the_Wind_Blows.html
Very recent-- posted Saturday night -- full scope article on Utility Scale Energy Storage, especially in light of need to cut CO2 emissions 80% by 2050:
http://energyeconomyonline.com/Utility_Scale_Storage.html
My general comment refers to the public policy debate surrounding renewable energy and in particular wind energy. The MAIN point raised (again and again) by opponents of renewable energy -- most notably the nuclear power industry -- is that renewables cannot supply "baseload" power. Insecurity is a powerful emotion and the opponents of renewable energy are using this to their advantage.
The renewable industry and its supporters ignore this argument at their peril. If renewable energy already had a track record of linking with storage to provide fully dispatchable (better than baseload) power, I believe there would be no discussion of providing hundreds of billions in Federal Loan Guarantees to the nuclear industry. We would also have a much clearer path to reaching the stupendous cuts in CO2 emissions in a GHG reduction bill.
I agree storage is not needed now for low penetrations and with abundant and cheap natural gas. So, it is hard to argue on today's prices that it needs to be done. However, we need to set out a full plan on how we will get where we need to go in just the next few decades -- and storage is the key.
Susan Kraemer — Aug 31 2009 06:28 PM
You’re welcome, Samir, one thing I am unclear about from the rather generic announcement from PG&E:
Does CAES require the use of some natural gas to run the generator? Can this all be done using wind power electricity? Your long pdf raised the question but didn’t clarify it for me.
Do you mind adding your answer back in comments at
http://cleantechnica.com/2009/08/31/for-base-load-wind-cheaper-than-fossil-fuels-caes/
Much appreciated!
Eamon Keane — Aug 31 2009 06:48 PM
Great blog, succinctly written! You make an interesting point about storage displacing new build of coal plants. Are new coal plants still under development in the US? Would sufficient storage be feasibly built in the near to medium term to discourage these plants?
I wish I'd come across this blog before I wrote my own piece on the same topic:
"Energy Storage is Not Needed for Renewables Integration"
http://seekingalpha.com/instablog/345817-engstudent/24647-energy-storage-is-not-needed-for-renewables-integration
Jon Myers — Sep 1 2009 03:20 PM
My company is SEQEnergy which has among its IP a process for developing barrier-protected, non-excavated geologic storage broadening the settings prospects for geologic storage. This capability would be useful in maturing markets as the need to get more projects built in optimized settings intensifies. As such, we have been interested in CAES, though this is an early market at best. As CEO, it has been my responsibility to discern why there a (until recently) lack of momentum and enthusiasm for CAES - particularly important given the strong 'academic' arguments in favor of bulk energy storage. I have concluded, after discussions with a number of ISO-types, regulators, utilities, analysts and wind-operators that the core problem is not that the AWEA is in denial but that wind operators, in many cases, simply are not seeing bids for day-time, peak power that are consistent with the data the promoters of CAES rely on. Without sufficient prices and price dispersion, storage cannot be justified as a capital investment. I believe the reason this is the case has to do with the failed deregulation of utilities in that utilities can and do preferentially dispatch their holding company owned assets when prices are favorable. Thus, there is a, I would contend, serious lack of price transparency in the market. This, by the way, sits well with the observed failure of the conventional independent power market to develop. I would welcome comments. For now, we regard CAES as a long-shot without policy measures addressing the price transparency and the structure of the market for electricity.
James Mason — Sep 2 2009 01:08 AM
Power plants built today will be in operation in 2050. And the U.S. and world are entering an era of increasing fossil fuel resource supply constraints and rapidly escalating climate change consequences. The task in front of us is to plan power plant capacity with the goal to minimize long-term electricity prices within the context of maximizing carbon dioxide emissions reduction.
Wind and CAES power plants are proven, on-the-shelf technologies capable of solving both the fossil fuel price and climate change problems. The current method of wind power plant deployment, which utilizes fast ramping natural gas combustion turbine power plants to balance and firm variable wind electricity supply to maintain grid reliability, does not solve either problem.
The U.S. is studying the impacts of wind power plants supplying 30% of the nation’s electricity by 2030 with the DOE/EERE sponsored EWITS (Eastern Wind Integration and Transmission Study) program. EWITS demonstrates that while wind power plant capacity is able to reduce the need for base load coal power plant capacity, there is a corresponding large increase in natural gas combustion turbine power plant capacity to balance and firm variable wind electricity supply, which enables the reduction in coal power plant capacity.
In contrast, the high wind penetration level in northern Europe is being supported by the export of the wind electricity from the European continent to Sweden where the wind electricity is used in conjunction with Sweden’s large hydro power infrastructure. And it has been noted that northern Europe is not realizing the steep carbon dioxide emissions reductions projected by wind proponents.
I have analyzed the EWITS power plant capacity allocation model to support the 30% wind electricity production scenario and find that it will result in unnecessarily high electricity prices and does not meet desired carbon dioxide emissions reduction (80% reduction by 2050). And importantly, the wind with backup natural gas plant model exposes electricity prices to the expected increasing volatility of natural gas prices in coming years. This does not take into account the exposure of electricity prices to carbon dioxide emissions reduction policies that have a significant probability of being instituted over the next twenty years as the known consequences of climate change mount.
The carbon dioxide emissions of aggregate wind-CAES electricity production are 80% less than the carbon dioxide emissions of a natural gas combined-cycle power plant and 70% less than the carbon dioxide emissions of natural gas combustion turbine plants providing backup support to wind electricity production. The major the weakness of the wind with backup natural gas power plant deployment model is the amount of time that the natural gas power plants have to spend in spinning reserve mode, which increases fuel consumption by 16% compared with the same plants operating in full power mode.
While coupling wind plants to CAES plants represents a large increase in upfront capital costs for power plant capacity, the fuel cost is zero. Annualized cash flow balances are the relevant metric to compare fossil fuel power plant and coupled wind-CAES power plant costs. My projection of $0.11/kWh electricity production cost (about $0.15/kWh retail when long-distance transmission and local utility company costs are added in) for base load wind-CAES plants is about 30% greater than the EIA estimate for new plant electricity prices but will be a bargain in the long term with increases in natural gas prices and carbon taxes.
The highest quality onshore wind resources are in the Midwest U.S., and this means that we will have to rely on deep saline aquifers for CAES air storage reservoirs, which will require about seven years for reservoir identification, testing and development. Therefore, we need to implement a plan now to finance the search for air storage reservoirs in the most desirable high wind regime areas of the Midwest to prepare for the large-scale deployment of wind capacity to meet the 30% wind by 2030 goal.
Other wind electricity storage options such as batteries, including the pluggable electric vehicle idea, and pumped hydro have major development and implementation obstacles to overcome before they can even begin to be considered economically viable candidates. Also, recent cost estimates for nuclear power plants indicate that they will be considerably more costly than coupled wind-CAES base load power plants. And finally, the wind-CAES plant design is flexible and is an ideal option for dispatchable peak electricity supply.
James Mason, American Solar Action Plan, Farmingdale, NY.