Wind, solar power paired with storage could be cost-effective way to power grid

Dec 10, 2012 by Teresa Messmore
A University of Delaware study finds a combination of wind power, solar power and storage could be a cost-effective solution to energy demands. Credit: Lisa Tossey

(Phys.org)—Renewable energy could fully power a large electric grid 99.9 percent of the time by 2030 at costs comparable to today's electricity expenses, according to new research by the University of Delaware and Delaware Technical Community College.

A well-designed combination of , solar power and storage in batteries and fuel cells would nearly always exceed demands while keeping low, the scientists found.

"These results break the conventional wisdom that is too unreliable and expensive," said co-author Willett Kempton, professor in the School of and Policy in UD's College of Earth, Ocean, and Environment. "The key is to get the right combination of electricity sources and storage—which we did by an exhaustive search—and to calculate costs correctly."

The authors developed a to consider 28 billion combinations of and storage mechanisms, each tested over four years of historical hourly weather data and electricity demands. The model incorporated data from within a large regional grid called PJM Interconnection, which includes 13 states from New Jersey to Illinois and represents one-fifth of the United States' total .

Unlike other studies, the model focused on minimizing costs instead of the traditional approach of matching generation to electricity use. The researchers found that generating more electricity than needed during average hours—in order to meet needs on high-demand but low-wind power hours—would be cheaper than storing excess power for later high demand.

Storage is relatively costly because the , batteries or hydrogen tanks, must be larger for each additional hour stored.

One of several new findings is that a very large electric system can be run almost entirely on renewable energy.

"For example, using hydrogen for storage, we can run an electric system that today would meeting a need of 72 GW, 99.9 percent of the time, using 17 GW of solar, 68 GW of offshore wind, and 115 GW of inland wind," said co-author Cory Budischak, instructor in the Energy Management Department at Delaware Technical Community College and former UD student.

A GW ("gigawatt") is a measure of electricity generation capability. One GW is the capacity of 200 large wind turbines or of 250,000 rooftop solar systems. Renewable electricity generators must have higher GW capacity than traditional generators, since wind and solar do not generate at maximum all the time.

The study sheds light on what an electric system might look like with heavy reliance on renewable energy sources. Wind speeds and sun exposure vary with weather and seasons, requiring ways to improve reliability. In this study, reliability was achieved by: expanding the geographic area of renewable generation, using diverse sources, employing storage systems, and for the last few percent of the time, burning fossil fuels as a backup.

During the hours when there was not enough renewable electricity to meet power needs, the model drew from storage and, on the rare hours with neither renewable electricity or stored power, then fossil fuel. When there was more renewable energy generated than needed, the model would first fill storage, use the remaining to replace natural gas for heating homes and businesses and only after those, let the excess go to waste.

The study used estimates of technology costs in 2030 without government subsidies, comparing them to costs of fossil fuel generation in wide use today. The cost of fossil fuels includes both the fuel cost itself and the documented external costs such as human health effects caused by power plant air pollution. The projected capital costs for wind and solar in 2030 are about half of today's wind and solar costs, whereas maintenance costs are projected to be approximately the same.

"Aiming for 90 percent or more renewable energy in 2030, in order to achieve climate change targets of 80 to 90 percent reduction of the greenhouse gas carbon dioxide from the power sector, leads to economic savings," the authors observe.

The research was published online last month in the Journal of Sources.

Explore further: Researchers convert carbon dioxide into a valuable resource

More information: www.sciencedirect.com/science/… ii/S0378775312014759

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User comments : 18

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Lurker2358
1 / 5 (5) Dec 10, 2012
the wind energy industry could use a little imagination.

If they had automated cleaning and inspection systems on the turbines, they could save enormously on labor costs and down time.
Bob_Wallace
2.3 / 5 (3) Dec 10, 2012
The wind industry has imagination.

GE is working on fabric blades which could lead to a 40% cost drop.
djr
3.7 / 5 (3) Dec 10, 2012
If they had automated cleaning and inspection systems on the turbines, they could save enormously on labor costs and down time.

Could you provide data on the current costs of cleaning and inspection - and how how much that would be reduced by automation. If one MW of wind power cost say $60, what percentage of that is in cleaning and inspection.
djr
not rated yet Dec 10, 2012
Correction - I should have said if 1 MwH costs $60.
tpb
1 / 5 (1) Dec 10, 2012
At this time and in the foreseeable future storage is totally impracticable.

Generating hydrogen from electricity is less than 50% efficient, storing it will require compressing it and or liquefying it, another approx 50% loss, turning hydrogen back to electricity is about 50% efficient with fuel cells.
So, you only have 12.5% of the original energy after conversion, storage, and conversion back to electricity.
Also massive tanks to store the hydrogen and expensive high temperature fuel cells, not to mention huge motor/generators or inverters to convert the DC output of the fuel cells to AC.
It would be far better to overbuild capacity of renewables, and use fossil or nuclear to supplement and forget about storage completely.
Lurker2358
1 / 5 (4) Dec 10, 2012
It would be far better to overbuild capacity of renewables, and use fossil or nuclear to supplement and forget about storage completely.


I actually agree, but few seem to get that, because most are still thinking like idiots trapped in the existing concept of energy economics.
3432682
2.1 / 5 (8) Dec 10, 2012
If there were cost-effective storage of electricity, we would have started driving electric cars 100 years. Perhaps in another 100 years...
CapitalismPrevails
1.7 / 5 (6) Dec 10, 2012
the wind energy industry could use a little imagination.

If they had automated cleaning and inspection systems on the turbines, they could save enormously on labor costs and down time.


That kind of automation is probably too IMAGINARY and cost prohibitive to employ. Otherwise, they would have done it already.
kochevnik
2 / 5 (4) Dec 10, 2012
@tpb So, you only have 12.5% of the original energy after conversion, storage, and conversion back to electricity.
Hydrostorage can be 80% efficient. Your entire post is baseless.
That kind of automation is probably too IMAGINARY and cost prohibitive to employ. Otherwise, they would have done it already.
Do you understand the meaning of the word NOW?
tpb
2.3 / 5 (3) Dec 10, 2012
kochevnik
If you READ THE ARTICLE, I commented on hydrogen storage which is mentioned in the article. I didn't bother with batteries because they are even more absurd. I also didn't discuss hydro-storage which isn't mentioned in the article either.
However, the land area needed at the heights required for efficient hydro-storage doesn't exist in the area from Illinois to New Jersey which is the area used for the model and calculations according to the article.

Eikka
2.2 / 5 (6) Dec 11, 2012
The main point of the paper is, that they're proposing to build 3x more capacity than the demand is, and dumping the excess into heating. However...

"For example, using hydrogen for storage, we can run an electric system that today would meeting a need of 72 GW, 99.9 percent of the time, using 17 GW of solar, 68 GW of offshore wind, and 115 GW of inland wind,"


Incredible.

They have 200 GW of total capacity. The figures suggest that they're assuming nearly 36% capacity factor for the entire thing, which is much much too optimistic when you realize that solar has capacity factors well below 20% and wind power rarely tops 25%

Realistically, they're getting at most 50 GW out on average, and out of that, the vast majority is going to come when there's not enough demand and would have to be stored, at a loss of anywhere between 20% and 80%.
antialias_physorg
not rated yet Dec 11, 2012
They have 200 GW of total capacity. The figures suggest that they're assuming nearly 36% capacity factor for the entire thing, which is much much too optimistic when you realize that solar has capacity factors well below 20% and wind power rarely tops 25%

Since they simulated their ideas using REAL historical weather data I'd rather trust their figures than your ad hoc made up ones.
Uncle Sandy
1 / 5 (1) Dec 11, 2012
What we need are more people like these to try to find ways to make it work rather than naysayers to say it can't work. The bottom line is that it must work. If the resources currently spent protecting the interests of fossil fuel and nuclear power producers were instead spent on renewables, those same players could share the wealth and we'd all be much better off.
antialias_physorg
not rated yet Dec 11, 2012
If the resources currently spent protecting the interests of fossil fuel and nuclear power producers were instead spent on renewables,

The 'problem' is that the initial investments and bureaucratic hurdles to get alternative powerplants up and running are much lower than those for the conventional ones.

So it's a lot harder to monopolize that kind of energy production. And anything that can't be monopolized is bad for business - because that kind of stuff is open to free market pressures.

Naturally certain large companies aren't too thrilled about the prospect. It's hard to pay large hierarchies of useless managers and fat CEO bonuses with something that doesn't provide obscene profits.
djr
not rated yet Dec 11, 2012
"So it's a lot harder to monopolize that kind of energy production"

You are right antialias - as you can tell from many of the comments on this kind of thread - many people have not recognized the extent of the changes happening in the energy sector. This is a very exciting time. You might be interested in this article on the failure of many utility companies to adjust to the coming changes. http://cleantechn...-coming/
Eikka
1 / 5 (4) Dec 16, 2012
Since they simulated their ideas using REAL historical weather data I'd rather trust their figures than your ad hoc made up ones.


The weather data may be real, but they're necessarily making assumptions on how the simulated windmill or solar panel should react to that weather. They're also making overarching assumptions about local wind conditions from point samples without real small scale patterns like turbulence that affects the turbines.

The figures they're getting out of the simulated model don't appear to be anywhere near the figures real windmills do in the real world, in the real weather. It means their simulation is flawed. I wouldn't be surprised if they simply used an idealized model of a windmill that churns out power at wind speed cubed, and that's that.

antialias_physorg
not rated yet Dec 16, 2012
The weather data may be real, but they're necessarily making assumptions on how the simulated windmill or solar panel should react to that weather.

So? It's not like there aren't windmills/photovoltaics out there (and their power data) that can tell them EXACTLY how such systems react to various weather scenarios.

As noted: I'd go with their numbers instead of the ones you're pulling out of thin air. (And I hope so are decision makers/investors)
VendicarD
not rated yet Dec 16, 2012
"The figures suggest that they're assuming nearly 36% capacity factor for the entire thing," - Eikka

Eikka didn't read the article well enough to see...

"The authors developed a computer model to consider 28 billion combinations of renewable energy sources and storage mechanisms, each tested over four years of historical hourly weather data and electricity demands."

Historical hourly weather data.