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Can Demand Response Help Us Achieve 100% Renewable Energy?

Jessica Kennedy's picture
Energy Consultant Energy Curtailment Specialists

Jessica Kennedy has worked in the energy industry since 2008. She earned her bachelor's degree in English from the State University of New York at Geneseo. She earned her master's degree in...

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  • Jan 12, 2013


renewable energy solar wind 
A recent study published in the Journal of Power Sources has proposed that a mix of wind and solar energy production, along with energy storage technology and a standby supply of fossil fuel could create a 99.9% renewable energy grid by 2030. The study, titled “Cost-minimized combinations of wind power, solar power and electrochemical storage, powering the grid up to 99.9% of the time,” by Cory Budischack et al, investigates not only the issue of a renewable energy grid, but also minimizing the cost associated with renewable energy.  The possibility of up to 99.9% renewable energy capacity is promising, but the study almost ignores demand response, and that could provide the extra .1%.

Demand response (DR) involves consumers curbing their energy use, or implementing distributed generation, to relieve stress on the electric grid when supply falls short. DR programs are already in use all over the country, and successfully prevent blackouts and brownouts every year. The added benefit of employing DR resources rather than fossil fuel generation is that DR is less costly than operating peaking plants.  The focus of Budischak et al in the study was to keep costs to a minimum, so it seems DR may be a more fitting resource to consider.

The study models several different combinations of solar, wind, and batteries incorporated into a 72GW grid system based on PJM Interconnection data from 1999-2002. Potential output of wind and solar energy is estimated using weather data sampled from within the PJM territory. The study directly addresses the problem of intermittent renewable energy generation by employing a mix of wind and solar power.  The result, according to the model, is renewable energy supply with very few gaps in generation. Energy storage technology, such as fuel cells and grid-scale batteries can be used to fill any gaps in generation that do arise.  This creates an almost entirely reliable and renewable electric grid.  According to the models presented by Budischak et al, supply would fall short only about 9-72 hours over four years.  The authors suggest fossil fuel fired standby generation will fill this supply shortage, but this could prove to be more expensive than simply reducing electricity demand.  At the very end of the article, Budischack et al note “maintaining old fossil plant [sic] may be uneconomic if rarely used, in which case, other existing mechanisms – such as demand management, interruptible rates, or preloading storage from lower capacity fossil – could be used to retire old fossil plants.” Since this study focuses on ways to implement a renewable grid at the lowest cost possible, DR may be the ideal resource to meet the needs of a renewable grid that falls short only a few hours per year.

Whether or not demand response can supply the capacity needed to prevent a blackout or brownout in Budischak et al’s virtual renewable grid is still questionable.  It is not only a matter of how often a renewable electric grid may fall short of supply, but also the amount of energy that would need to be conserved to keep the grid stable.  Energy storage can keep this situation to a minimum by storing excess energy when generation exceeds demand, and discharging energy when demand is high, but there is a limit to how much energy can be stored.  In the study’s scenario where solar, wind and storage produced 99.9% of PJM’s energy, only 17MW of fossil fuel generation was needed, an amount easily met by DR resources.

This study presents an optimistic view of how our electric grid may function by 2030. The study’s most exciting calculation is that the renewable grid’s cost to consumers will be no more than what we pay for electricity today.  It would take sweeping changes in government policy and private industry for a shift to 100% renewable energy to be realized, but most experts agree that it must happen eventually.  2030 may not be the year we reach 100% renewable electricity generation, but there is no doubt that renewable energy will soon make up a large part of our energy resource pool.  Demand response is a clean energy tool that can ensure our grid maintains reliability even when those resources reach their maximum generating capacity.  Perhaps, with diverse energy assets and technology at our disposal, a 100% renewable energy future can be achieved sooner than we think.

Image: Renewable Energy via Shutterstock

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John NIchols's picture
John NIchols on Jan 17, 2013

 The authors of the study ignore the cost of constructing new transmission lines and include the price of "externalities", which are based on unproven and unverifiable models to assume price parity.  Sounds a lot like the climate change model "debate".  We still are involved in a debate aren't we? Alternative energy is  a pipe dream, unless and until a cost-effective utility scale storage solution is invented.

Joe Geranio's picture
Joe Geranio on Jan 17, 2013

I am in no way a expert on this subject, but doesnt fuel still have to be used to run the wind turbines?  I am wondering what the cost and how are we really saving on fossil fuels?  I also cant see Americans cutting back on heat and cooling.  Is this just a political power play for the EPA to conscript us into their regulatory ideology.  I Don't trust this.  Is anyone looking at SAFE nuclear power in the USA, or has that just died off?





Bill Storage's picture
Bill Storage on Jan 18, 2013

"Energy storage technology, such as fuel cells and grid-scale batteries can be used to fill any gaps in generation that do arise."

On what technology is this statement based? No utility-scale storage system is remotely close to being practical. We might with equal accuracy say that wind power is unnecessary as electricity can be generated from fusion.

It is such statements that have led some to conclude that environmentalism is a religion. This is little more than an appeal to faith.


Jessica Kennedy's picture
Jessica Kennedy on Jan 19, 2013

Hi Bill,

It is true that grid-scale energy storage technology is still in its infancy.  Different chemical batteries, flywheel storage, hydrogen fuel cells, thermal and hydro storage systems among others, are all being researched as possible storage solutions.   
A whitepaper published by the International Electrotechnical Commission covers the topic in great depth.
With the current amount of R&D being done, it's hopeful that a grid-scale storage solution will be viable in the near future.

Thanks for your comment!


Jessica Kennedy's picture
Jessica Kennedy on Jan 18, 2013

Hi Joe,

I'm not aware of any turbines that use fossil fuels to operate - except for the manufacturing process.  They use the wind to create kinetic energy & turn the blades.  That gets transfered to the generator & sent through the transmission line. 
manufacturing wind turbines certianly has an environmental cost, but once the turbines are operating they tend to cancel that cost out. 

And yes, nuclear power is also being re-investigated!  The Wall Street Journal published an article on that in November.  It discusses smaller reactors with underground radiation containment that may be safer. 

Thanks for commenting! 

Jessica Kennedy's picture
Jessica Kennedy on Jan 18, 2013

In the original study the authors actually implemented the lowest-cost options into their model.  It will cost a huge amount of money to implement these changes to our electric grid, but the fact is that our electric transmission system is seriously out-of-date and in need of upgrades anyway.  Whether we integrate more alternative energy transmission lines or replace the current infrastructure - which is an average of about 50 years old - we'll need to spend the money.

As far as climate change, it may or may not be a reality, but our finite supply of fossil fuels is definately a reality.  We need to have energy sources on hand for the day we finally run out of coal and oil.



Joe Geranio's picture
Joe Geranio on Jan 18, 2013

Thanks for your reply, I will look into the article on safe nuclear power.



Michael Hogan's picture
Michael Hogan on Mar 7, 2013

Both the referenced study's scope of storage options and your description of the role of demand response are way off the mark. The commentator who remarked on the utter lack of any grid-scale storage technologies on the horizon that have the ability to do what the study claims they would do, at the scale required and at a cost that any sane person would be willing to pay, was absolutely correct. Not to say something won't emerge from the many R&D efforts focused on the question, but relying on genies popping out of bottles is no way to create an energy strategy, and 2030 is right around the corner so a grid-scale tecnology so new is unlikely to be deployed commercially in sufficient quantities to have a material influence by 2030 anyway. But here's the point: grid-scale storage is not the answer, distributed end-use energy storage is. Some call it energy storage, some call it demand response, but converting electricity to hot water for its many end uses, ice for space cooling, non-energy end-use services (e.g., over-production of crushed stone at aggregate operations, off-peak pumping of water at municipal water facilities) and any of hundreds of other such electricity-intensive, storable end-use applications are all feasible today at very low cost and with much higher ene-to-end conversion efficiency than any of the grid-scale storage technologies available today or likely to be available at scale, if at all, by 2030. Several much more credible studies than the one you cite incorporate the potential for this form of energy storage/demand response as one of the several keys to integrating very large shares of renewables reliably and affordably into the modern power grid by 2030. NREL's Renewable Energy Futures Study and the European Climate Foundation's Roadmap 2050 and Power Perspectives 2030 study are probably the most comprehensive and robust pieces of work out there. I don't know if 100% renewables by 2030 is realistic, nor am I convinced it's an objective worthy of much time and effort, but we can reach very high shares of renewables by 2030 (80% renewables by 2030 would be an heroic accomplishment and would have us comfortably on track to where we need to go from a climate perspective) without relying on magical electricity storage ideas and with a much more comprehensive understanding of what's currently feasible and very affordable at the level of "demand response."

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