The success of solar depends on storage

Storage helps the sun keep shining even on cloudy days

Posted by Kristina & Jason Makansi (Guest Contributor) at 4:18 PM on 22 Dec 2007

Read more about: energy | solar voltaic power | Arizona | electricity grid

New project and technology announcements have kept solar energy in the news lately. But, as with wind, the issues of intermittency and the grid still lurk in the shadows. Some still argue that intermittency isn't a problem, or that it can be solved without storage.

In a new piece in the Arizona Daily Star, reporter Tom Beal talks about those issues. As we've previously argued here, here, and here, energy storage has a big role to play in enabling solar and wind to compete with the big boys -- coal, gas, and nuclear.

The engineers that actually operate the grid on a minute-to-minute, day-to-day basis know that intermittency is a technological problem that must be solved one way or another if solar and wind are to generate more than a token percentage of our electricity. Storage needs its own day in the sun, and now that sun is in the limelight, maybe storage will finally get some respect as well.

Full piece below the fold:

There is a shadow over the bright future of solar power in Arizona, cast by the clouds that blanket our metropolitan areas when our demand for electricity is greatest.

They call the problem "intermittency," and it could have its biggest impact midafternoon in midsummer, when we're all running our air conditioners to counter the heat.

Whether those solar panels are part of a big power plant or distributed across the rooftops of Phoenix and Tucson, they will lose their power source just when the electric grid needs it most.

If Arizona is to become "the Saudi Arabia of solar energy," it needs to find ways to keep the electrons flowing through those summer storms and during the total lack of sunshine at night.

Scientists say we simply need to expand our vision of what constitutes a storage battery to include lakes, caverns, tanks of heated liquid and fleets of parked electric cars. In the future, we might use solar power when it's not in demand to compress air and store it underground, releasing it to spin turbines when the clouds come by.

Other solutions include fleets of privately owned electric cars whose batteries can be plugged into the electric grid or bi-level lakes where water is pumped uphill when power is plentiful and run downhill through turbines during peak demand. Add to that the proven solar technology of solar troughs, which use mirrors to focus the sun's warming rays on liquid-filled pipes that in turn heat and vaporize gases that power turbines.

Scientists say a mix of these strategies will be needed if solar is to become a dependable solution to our urgent need to find power sources that don't give off greenhouse gases.

The solutions are a few years off, but so is the problem. Arizona's utilities aren't generating vast amounts of power from renewable sources right now because of solar's other impediment -- high cost.

Still, the intermittency of renewable power sources is already a technological problem, said Tucson Electric Power spokesman Joe Salkowski.

At its Springerville power plant, where coal is burned to produce 760 megawatts of power, TEP adds another 4.6 megawatts to the same transmission lines from a photovoltaic array. Even at that low level, said Salkowski, "we feel that hiccup" in the operation of the coal-fired generators when clouds pass by.

It's no threat to the grid yet, but TEP is currently supplying less than 1 percent of its power from intermittent, renewable sources. In the future, said Salkowski, "It's a challenge we need to overcome."

Olgierd Palusinski, of the University of Arizona's Electrical and Computer Engineering Department, is working on a cure for the hiccups, and perhaps for the entire problem.
Working with researchers from Arizona State University and the University of California-Irvine, Palusinski is electro-plating metals into the extremely small pores of a non-conductive membrane, creating a storage battery that doesn't need the wet chemistry of standard ones. It simply stores electrons.

If it works, it will be more efficient, smaller, less costly and longer lasting than a standard battery, he said. An array of the devices could store enough electrons to provide 24-hour power from solar, he said.

Ben Sternberg, a professor in the UA Department of Mining and Geological Engineering, proposes a survey of underground caverns where compressed air can be stored for days before its pressure is released to spin turbines.

Sternberg wants to employ the skills and imaging techniques he honed searching for oil and gas over the past two decades, to find appropriate places to sequester compressed air underground.

Tom Hansen, a vice president for research at TEP, said the anticipated phenomenon of power loss at peak demand during Arizona's monsoon season is one of the biggest impediments to growth in solar generation.

And, he told a group of scientists at the UA last month, it could be their biggest research opportunity in coming years. UA scientists, already researching a variety of solar topics, want to use some of the solar research money given them by the Legislature earlier this month to attack the intermittency problem.

The electric grid can't handle more than a 10 percent fluctuation in power without shutting down, said Hansen, and his company, along with other Arizona utilities, has been ordered by the Arizona Corporation Commission to generate 15 percent of its power from renewable sources by 2025.

Solar is the best bet for meeting that goal, he said, and for supplying even larger levels of power in the years to come, as oil and gas supplies dwindle, and coal falls into disfavor as an energy generator.

The Arizona Corporation Commission knew of the intermittency problem when it ordered Arizona's utilities to meet the 2025 goal, said Commissioner Bill Mundell, but dismissed the utilities' argument that it would keep them from meeting the goal.

"We said, 'Look, when you get close to the 10 percent and reliability is still a concern, some future commission will address it, but right now it's a hypothetical concern,' " said Mundell.

Mundell is betting that technology will solve the problem well before the goal is met, and he predicts that, by that time, solar will also be a cheaper source of energy than others. The price of oil and gas is going up, he said, and some sort of carbon tax on coal burning is inevitable.

The basic technology for capturing sunlight for electricity is good and increasingly reliable, Hansen said.

TEP's array of photovoltaic panels near its coal-fired plants in Springerville has been generating electricity for six years and TEP has had to replace only 150 of the 34,000 modules in that time. It costs the utility $5,000 to $10,000 a year to operate the array, Hansen said, and most of that cost is for cutting the grass.

Wind turbines are already competitive with natural gas for generating electricity, said Mundell, but the state has very few areas with sufficient, consistent wind. He said solar is the future.

"We should be the Saudi Arabia of the world for solar," he said.

For story: The success of solar depends on storage
16 Comments | Post a Comment

Interesting thought

Here in Seattle we have recycling trucks that come by once a week to pick up recycling bins. It is cost effective only because most of the work is done for free by consumers. We sort it, store it and then transport it to the curb all for nothing save slightly lower trash rates. The city uses our tax money to buy the bins and give them to us.

I can see a similar situation where hybrid car batteries are used for free by the government and the consumer gets a charged battery for free by letting them use them to balance loads, store energy.

In the end, it all comes down to biodiversity. Poison Darts--Protecting the biodiversity of our world

by biodiversivist at 6:38 PM on 22 Dec 2007

biodiversist's model...

could also be used for residential and commercial PV panels. Why not have the utility own the panels, inverters, and all the power they generate and offer some sort of rent-offset to the roof owner? solves the up-front capital problem of market penetration of PV (since the utility will have to build destructive "renewable" power plants otherwise, so they are spending regardless), and keeps the wilderness from suffering, yet again, from man's greedy urban consumption.

local, residential/commercial solar is the answer if you ask the right questions. one of the pre- questions has to be "how steeply tiered can we make these utility bills so people start conserving and stop wasting?"

the greenest energy is that which you needn't ever produce.

by stopgreenpath at 7:39 PM on 22 Dec 2007

John Mashey

There is one basic action that can be taken that helps, and without which, one should not expect much useful to happen [according to the CEO of CA's PG&E, http://www.pge.com/ ]:

state PUCs have to change the rules to incent electric utilities by rewarding efficiency, not just generating megawatts. When they do that, utilities start doing things like giving away CFLs... and other things to get smarter.

Does your state do this? How well does it work? {Since there are different ways.]

-John Mashey

by JohnMashey at 8:50 PM on 22 Dec 2007
[ Parent ]

Storage, wider grid or both

I think it's a matter of both better storage and a better grid. One recent development shows that much higher energy densities are possible - see here - although this is more applicable to EV's than home or grid storage that isn't constrained by size or mass but could make the use of plugged in vehicles for storage more attractive - except don't we want that for driving around? Better batteries could also make it possible to ship electricity around the world much as fossil fuels are now, but that's not really a very elegant solution. Personally I see the grid, and somehow making it global as the real solution to intermittency. Under ocean HVDC between continents? Orbital energy transmission systems as proposed for Space Power systems, but with the solar collectors on the ground (more achievable than launching them into orbit)? Whichever way it's a massive project - but then the need is there.

by Ken Fabos at 1:51 AM on 23 Dec 2007

Solar Thermal Stores Well

(pun intended)

Solar thermal power plants allow relatively basic storage of load capacity in the form of steam, hot salts or geothermal injection/recovery of steam. They also collect more power per unit area of surface than existing PV systems.

Stirling engine generators combined with the ability to use stored thermal energy could allow power generation levels to be maintainned at night. The reduction in thermal input compensated for by the increased ability to shed waste heat. There are associated costs but no real egineering challenges.

In Arizona's specific case demand flexibility could be easily achieved by conversion of HVAC systems to GeoExchange based systems. Much of Arizona's peak load is being spent attempting to dump excess building heat into already hot air. Even a simple load shift using ice storage systems at the point of use would significantly reduce peak load requirements if the systems were installed.

Of course it would be too simple to demand that utility users in hot climate areas convert their roofing to a high thermal albedo/low thermal mass materials (white metal roofs) in order to retain there ability to use air conditioning. Looking down on Pheonix from Google Earth you will see miles upon miles of black asphalt or red tile roofs. Replacing those roofs or shading them would save untold megawatts of cooling load.

Arizona is a sustainability disaster any way you want to look at it. In water policy, food, energy, transportation or population it can not possibly support it's existing population with local resources.

Put the Carbon Back

by Pangolin at 5:54 AM on 23 Dec 2007

Sort of the same..

This is kind of similar to your idea bio-d. But it leaves your own battery in your car.

Since you know when you need a fully charged battery to drive your car most of the time (in emergencies you can always fire up the gas burning part of a plugin hybrid), to go to work, school, shopping for instance, the power company could use your battery to smooth the grid flow up until about 2 hours before you need it.

In return they would recharge your battery in that 2 hour window (about the charge time of the new nano lithium ion batteries) for free.

Pretty good deal for consumer and grid operator alike. No need to remove batteries.

This would necessitate a smart grid connected with internet switching/metering devices in each car. That way it can be plugged into the grid anywhere, at work, home, school, or even shopping center. If you give the grid a certain number of hours per day to use your car batteries, you get a free charge.

The grid computer knows your car through it's device identity then takes care of timing and charging or crediting your power account, similarly to a credit or debit card account. Over the net, the net that runs over the grid.

For more storage if needed (30 million plugin hybrids, even 10% of the car fleet in the uS ought to be enough storage), everything from your fridge or freezer at home to large cold storage facilities, and cooling/heating systems from homes to malls, could be turned on and off as needed by their own internet switches, in response to power supply and demand.

Like ants on a log, one ant keys of the next ant, and they never have a traffic jam and fall off. These distributed computing devices, the internet enabled switches, acting like a hive mind to ensure a steady power flow.

Clouds or nightfall dip the solar power supply, the demand not supplied by other sources, wind, water, or biogas power; is met by turning off some freezers or cooling/heating systems. The cool/heat stored (using either building or frozen mass or heat/cold storage media)to allow coasting for a few hours.

Separating solar out as specifically needing storage to be practical and not taking into account the other various renewable sources, like wind, water, and wave power, and backup sources like distributed cogenerators using biogas (or natural gas as a fossil fuel ultimate backup), tends to paint an unecessarily difficult challenge.

The picture is much brighter taking all thr various aspects of a renewable distributed generation and storage smart grid into account. Folks like Al gore and Amory lovins, and our media darlings (hehey) from the blog world, like DR, Sean, and Joeseph, need to take a leap and start talking up this still sci-fi like notion.

Google and others are working on it. That's my partially informed guess.

Kristina and Jason take note especially! You two could really research what's going on and push this technology into the media spotlight and the conference network attended by utility engineers and managers.

http://amazngdrx.blogharbor.com/blog

by amazingdrx at 8:50 AM on 23 Dec 2007

engineering

Much of the domestic hot water in Arizona is made from electricity. APS (Arizona Public Service) claims there is no market for solar hot water.

Hot deep ground storage can make 24 hour power with conventional big turbines, at a cost less then $0.01/kWh(e).
http://gristmill.grist.org/story/2007/9/21/124735/407#com ...

Those who think solar Stirling or any other untested solar thermal power should be deployed on a massive scale should read this testimony at the CEC.
(I've known Dr. Butler well since 1978, a leader in the industry)

Barry Butler CEC

First order of business should be to shut down dead carbon combustion. Solar energy is a large resource. Solar electricity is a subset of solar energy and most economical when used for cogeneration of heat/cooling and power.

by sunflower at 9:55 AM on 23 Dec 2007

hmm

I thought I read that the subtitle of solar power is the 'air conditioning energy source.' A sunny day, lots of power and air conditioning needs. A cloudy day, not so much power, not so much air conditioning needs.

But hey, if the utilities say they need storage, I couldn't disagree.

by trock at 4:39 PM on 23 Dec 2007

Solar storage, later

Based on Sunflower's comment, and I did read the attached testimony, let's just use solar for some residential rooftop electricity and some hot warm water for now. A nice solar energy storage device would be a hot water tank, thank you.

Onward through the fog

by Sam Wells at 5:33 PM on 23 Dec 2007

You don't really need

You don't really need anything as esoteric as stirling generators to do solar thermal storage.

They've been doing "Molten Salt" steam generators for quite some time in California's Death Valley solar thermal arrays.

The real question there being which solar thermal is best.

Solo towers, multi towers, or troughs.

Dishes, while effective, and capable of some correction for shading, don't really offer storage.

by GreyFlcn at 10:31 PM on 23 Dec 2007

There were two dish central steam turbine plants

Lajet Southern California and GE Shenandoah GA.

by sunflower at 6:16 AM on 24 Dec 2007

Talk About Shaky

Recently, the 400 scientists who proposed that nanotechnology would be a medium term answer to GC worries were criticized by Gristers by making their cure dependent on an unknown.

Yet, now you admit that all the darlings of green energy -- solar, wind -- are incapable of handling baseload without "storage". And battery "storage" has been the most elusive technology of all for the last 100 years!

Thankfully, this weeks nanowire breakthrough may be a panacea for you all.

But, still, 4 stars for hypocrasy. Keep it up.

Texeme.Construct(function(x)=Participation(x))

by jabailo at 9:25 AM on 24 Dec 2007

missing the obvious answer

This is a fine post in that brings up and explores an important issue. If we can't provide energy when its needed then its not all that helpful.

Well there's a really simple answer this post fails to acknowledge, just use fossil fuels to bridge the gap. If we can get solar and wind to provide electricity demand by 85%, the current coal plants can go online 15% of the time. That's a fair trade for 85% less carbon emissions and constant energy supply. Should be pretty easy.
We can't just slash out our fossil infrastructure. So lets use it as a stop gap and invest all new generation in renewables. Let's be honest, its going to be a while before this electricity provides so much that it stress the ability of the grid to provide energy.

by danielbell at 10:15 PM on 25 Dec 2007

Wrong solution

Thankfully, this weeks nanowire breakthrough may be a panacea for you all.

While nice, storage has far more to do with economics and durability

than charge speed and portability.

Great news for electric cars though.

by GreyFlcn at 10:39 PM on 25 Dec 2007

Recommendations to maximize energy-cost - why?

Danielbell wrote: So lets use [our fossil infrastructure] as a stop gap and invest all new generation in [epithet deleted].

What if solar and wind are more-expensive than alternatives?

by Nucbuddy at 1:34 AM on 26 Dec 2007
[ Parent ]

What if

What if renewable energy were cheaper buddy?

Then the jobs created by a renewable energy boom would result in lower cost energy and greater productivity, raising everyone's standard of living.

Those energy related dollars charged to consumers and taxpayers go to mega-klepto multinational energy corporations and military contractors now.

All moved offshore to Dubai or Switzerland as quickly as possible. The corporatistas see their legal jeopardy and are moving their money to places beyond extradition. And investing it in low cost manufacturing nations, outsourcing US jobs.

Invest that money in domestic, local, distributed renewable power and everyone wins. Except a few corporate "citizens" who make their living through stealing (Enron), torture, and murder (Blackwater).

Give them one vote per corporate "citizen" instead of unlimited bribery (lobbying) and their agenda would be history. To be studied but never repeated.

http://amazngdrx.blogharbor.com/blog

by amazingdrx at 7:16 AM on 26 Dec 2007

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