Archive for Wind power

Large Scale Electricity Storage.

One of the biggest barriers to the adoption of wind and solar electricity generation is the lack of storage technology with the capacity to handle the hundreds or megawatt hours necessary.    

Large scale electricity storage technology also allows utilities to flatten their demand, and defer construction of expensive new generation. 

Here’s a quick rundown of some of the technologies vying to meet this need.  Most of this is information is drawn from the Electricity Storage Association website.




$/kWh; efficiency

Investment opportunities?

Pumped Hydro: Reservoir to Reservoir

Energy is stored by pumping water from a low reservoir to a higher one, and recovered by running the water back out through a turbine.  This system can be easily retrofitted into existing reservoirs, but has limitations due to water regulations.  First used in 1890.

The cheapest and most developed technology, pumped hydro is nevertheless limited by the availability of suitable sites.

$3-$50 per kWh;

70% to 85%

The major supplier in the business is private.  Could look for opportunities in utilities that have good potential projects.

Compressed Air Storage (CAES)

Energy stored by compressing air into large underground caverns.  Air combined with natural gas on exit and burned in turbine.  The gas compensates for the cooling as air decompresses. 

Gas used is about 40% of the amount used in comparable peaking turbine.  First built in 1978.

70% to 80% efficient; $30-$100 per kWh


Underground Pumped Hydro

As above, but water is pumped between an aquifer and an above ground reservoir.

More sites available, developing application.  Might have some water quality issues.

Costs Low

75% to 85% expected efficiency.

Small turbine/pump makers.

Polysulfide Bromide battery

A regenerative fuel cell based battery technology (aka “Flow Battery.)  Seems have run into difficulties due to the toxicity of the chemicals involved.  

15 MW demonstration project in 2003; more recent projects canceled.

75%, unknown cost;

Regenysis, the owner of this technology, was a subsidiary of
Germany’s RWE.  No recent activity; the program may have been wound down.

Molten Sodium-Sulfur (NaS) Battery

Molten battery technology.  “Safety concerns addressed in

30 sites in
Japan, mostly for peak shaving.  Largest is 6 MW for
Tokyo electric

Cost “High” compares to BrS and hydro/ CAES.

NGK, Japanese power equipment supplier focused.  Can be bought by US investors on the Pink Sheets NGKIF.PK

Regenerative Fuel Cell (Hydrogen)

Fuel cells can be run in reverse for electrolysis, with the hydrogen stored in large tanks.

First pilot project 2004

“much less” than 80%

Fuel cell manufactures: Ballard, FCEL, and others.

All these technologies except hydrogen are dealt with very well on the Electricity Storage Association site.  They have some great technology comparison graphs which deal with a lot more variables than I have here in their technology comparison section.

Cost Comparisions

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Efficiency/Quality Comparisons:

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Of these technologies, Pumped Hydro and CAES are the only ones ready for near term, large scale deployment (with NaS and Flow Batteries applicable in some markets highly constrained markets.)

The major downside for pumped hydro is siting, part of which problem can be solved with the smaller scale reservoir to aquifer option.   For CAES, the downside is the need to use gas to run the turbine, albeit a very efficient one.  One option might be to substitute for the natural gas used in CAES with hydrogen from electrolysis, allowing the system to work at locations remote from natural gas supply, and, for wind energy storage systems, be 100% renewable.

 10/20/06- Article about a flow battery from VRB power systems for an Irish wind farm.

8/5/07: Here’s an article I just wrote about two potential investments in utility scale electricity storage.

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I spent much of the last week at the 25x’25 “Twenty-Five by Twenty-Five” second implementation planning meeting.  25x’25 is a coalition advocating the vision that “By 2025,
America’s farms, forests and ranches will provide 25 percent of the total energy consumed in the
United States, while continuing to produce safe, abundant, and affordable food, feed and fiber.”   That’s at least 25% of our energy from renewable sources.

            25x’25 is an open alliance; the participants are the organizations who have endorsedthe 25x’25 vision outlined above.  These include 18
US Senators, 91 Congressmen, 18 state governors, 4 state Legislatures (including
Colorado).  I attended the conference as the representative of the
Colorado Renewable Energy Society. 

            I highly encourage my readers to endorse 25x’25 (you can endorse as an individual, or as an organization, or both.)  Your endorsement helps them demonstrate that a broad swath of Americans support the 25x’25 vision, and will help convince the US House and Senate to pass the concurrent resolutions for 25% of the nation’s energy supply to come from renewable sources.

We are currently in the process of coming up with our vision of how
America can achieve 25x’25.  Any endorsing individual or organization can participate.  The goal is agree on a series of recommendations (the Implementation Plan) as to how we can achieve the 25x’25 vision.  When the Implementation Plan is complete, which we plan to achieve by January, in time for the next congressional session, all partners will have a chance to endorse the plan.

Since the whole process is by consensus, and the 25x’25 goal is an ambitious one, it would be easy to believe that the Implementation Plan will turn out to either be watered down to the point where it does not say anything, or end up endorsing so many points of view that it would be ludicrous to call it a plan at all.

Having now participated in two conference calls and two days of face-to-face meetings, I’m happy (and somewhat surprised) to report that we’re actually managing to form a consensus among a large group of people and organizations you would not expect to get along under ordinary circumstances.  For this, I can only shake my head in wonder at the diplomacy and perseverance of the Steering Committee.  They managed, though two days of what could have turned into a verbal free-for-all, to keep us all focused on the need to work together to reach the very ambitious goal we’ve all agreed upon.  (In that same spirit, and understanding that many of the participants have been willing to voice their true opinions and step away from the party line, I will not name any names here.  This also has the advantage of covering for my lousy memory for names.)

How do they do it?  By keeping us focused on the fact that we all agree on the goal: 25% of our nation’s energy from renewable sources by 2025, and reminding us that we’re never going to get there by half measures.   The second thing they did was keeping the discussion focused on “Yes, if…”: continually reminding people to stay in the mode of working together, and instead of thinking about all the reasons that something was impossible to accept, to instead say “I could accept that if it were this were also to happen.”

So my kudos to the people I met on the steering committee.  I was impressed.

Read the rest of this entry »

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Watts and Revolts- more Intermountain Rural Electric controversy


In the September issue  of Watts & Volts, IREA management attempts to make three arguments:

  1. They say the investment in Comanche 3 will save their customers money relative to gas generation.
  2. “There is no way to produce large amounts of reliable power without CO2.”
  3. They attempt to brand members who oppose their actions as extreme environmentalists who want to ruin our economy and send us back to the Stone Age by imposing gigantic taxes on CO2 emissions.

None of these arguments hold water.  I will deal with each in the order I’ve listed them above. Read the rest of this entry »

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Water and energy

Last month, several nuclear power stations in Europe had to shut down during a heat wave (and consequent period of extreme electricity demand) to avoid releasing overheated water back into the environment.  As many other astute observers have pointed out, this pokes another big hole in the arguments that nuclear is our best choice of carbon-neutral generating technology.  A power plant that goes down precisely when you need the most power is almost useless for the current grid.

It also brings up the broader point of the role of water in electricity generation.  Nuclear is not the only technology that uses water for cooling.  Coal plants, including “next generation” IGCC plants mostly use water for cooling (air cooling can be used, but it makes them less efficient, and hence more expensive to run, and is seldom used in practice.)

This is a problem because water, in most countries is under-priced.  Resources that are under-priced tend to be overused, since the user does not have to bear the full cost of supply.  This is the cause of a large number of ills, such as the drying up of the Aral sea due to irrigation for cotton farming.  It is not only poor countries who don’t have enough water.  In the US, mispricing means that almost every aquifer is being pumped at much faster than sustainable levels.  In this context, it seems certain that power plants are also paying too little for the water they use for cooling.

 With a looming need to increase farming to supply biofuels, it is more important than ever that water be priced appropriately, especially in planning scenarios for power plants.  When water is under-priced, generation technologies which use more water are likely to be inappropriately favored in comparison to technologies which use little or no water for generation.

 Like nuclear, thermal electric systems are usually water cooled.  Fossil-fueled power plants account for approximately 39 percent of the water used in the United States, second only to agriculture. For coal plants, this typically amounts to 3 gallons of water (Texas study) or 0.5 gallons (NREL study) for every kWh produced (25 gallons are used for cooling, but only 3 evaporate in the process).  Nuclear, Biomass, and Oil fired plants also require large amounts of water lost as steam in the cooling process.   Some Solar thermal technologies also require significant water for cooling.

Water use by large hydropower projects is more complex, since water in reservoirs is more useful for some purposes (recreation) but often less useful for wildlife.  However, there is no question that reservoirs increase evaporative losses.  An NREL study quantifies these losses in the US.  Overall, in the US evaporative losses average over 18.2 gallons per kWh of hydroelectric power generated.  These numbers vary widely depending on the reservoir, from 2-3 gallons per kWh in cool northern states, up to over 100 gallons per kWh in KY, OK, SD, and WY.  Keep in mind that a lot of these reservoirs have other uses besides power generation, such as storing water for dry seasons, but the numbers can be mind-boggling.

Technologies which use little water include gas turbines (both natural gas and gas from renewable sources such as landfill gas), and geothermal (the water is typically re-injected into the ground).

Wind, photovoltaic, and wave power require no water to generate electricity. 

Energy efficiency, by its nature, uses no water.  Readers will recognize that as an ongoing theme: Given the choice, it is better to avoid using a kWh than it is to generate a kWh (regardless of source… even renewables have environmental impact.)

Renewable energy advocates should also be advocating for more rational water pricing, especially in planning scenarios.  Water use in generation will eventually come to be recognized as a significant cost (and source of uncertainty, as France found out last month).  The sooner this happens, the better for everyone.  Pricing water properly will not only save water, it will help move us to renewable energy technologies.

Investors may do well by concentrating their investments on low water use technologies, especially in parts of the world where water is (or will soon be) scarce.

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John Turner’s Renewable Energy Future; renewable technologies compared.

When you want an informed, but unbiased opinion, it’s usually best to ask someone John A Turnerwhose livelihood does not depend on coming back with the “right” answer.  When it comes to comparing different renewable energy technologies, one of the best experts I’ve heard from is John Turner.   Dr. Turner is a principal scientist for the Center for Electric & Hydrogen Technologies & Systems at the National Renewable Energy Laboratory (NREL), in Golden, Colorado.

The Hydrogen economy is that long hoped for world in which one day our cars will fill up at the corner hydrogen station, and combine that fuel with oxygen in the air, a process which will create electricity for the car’s motor, and with the only emissions being water.  It all sounds wonderful, but to reach that nirvana of zero emissions, the hydrogen itself needs to be produced with non-emitting technology.  That is because, contrary to oversimplified hype from politicians, hydrogen is not an energy source, but rather an energy carrier.  Like a battery, it has to be produced (charged) before it can be used.

Dr. Turner’s goal is to guide us to the hydrogen economy with as few missteps as possible, with missteps in his mind being the used of unsustainable technologies to get there.  Since he wrote his visionary 1999 article in Science, outlining a path to a “Renewable Energy Future” in which hydrogen serves as portable energy storage for an economy fueled solely by renewable sources of power.  The weak link in this chain is fuel cell technology.  Fuel cells are used to efficiently convert hydrogen and oxygen to electricity and water.  They have been around for well over a century, but are still too expensive for use in cars, although they are practical in some military and larger scale civilian operations.  A similar problem exists for hydrogen storage.

In contrast, hydrogen as a storage medium for electricity from intermittent power sources such as wind is a technology whose time has come. Norsk Hydro is currently doing a trial run of a wind/hydrogen combination system on a small Norwegian island, powering 10 homes.

What is most interesting to me about his presentation, is his unbiased comparison of different renewable technologies, along with nuclear, and Internal Gasification Coal Combustion (IGCC) with carbon sequestration.

He compares these technologies for robustness: the ability to meet our future energy needs; for expense, and for Energy Payback.  Energy payback and the related measure EREOI (Energy Return on Energy Invested) give us an idea of how much of our energy will have to be devoted to making more energy.

Here’s the run-down (with some additions of my own):


Energy Payback/ EROEI Robust? Price per kWh (approximate 2003 prices) Long term?

3-4 months; 20-30x


5-8 cents


Solar PV

3-4 years; 8x


21-24 cents


Concentrating Solar

5 months; 40x


8 cents





7 cents



varies by source


4-7 cents



1 year, not counting waste disposal. <20x


13-18 cents


Coal (w/ carbon sequestration)

16% of energy required for sequestration.

For now

5-6 cents

70 yrs, at current growth rates.

Energy efficiency

months; 50x +

Can never get all energy from efficiency

1-2 cents


(Items with links are from linked sources)

We’ll need all these energy sources, but Wind and concentrating Solar (CSP) stand out as near-term, robust, economical solutions, while Energy Efficiency and Geothermal will give us the most bang for our buck as we try to get started down the road.

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Maui: Wind Farms and more

 Picture: Kaheawa Wind Farm on Maui

Kaheawa Wind Farm on Maui

It seems that every time I turned around in the last three weeks I’ve been hearing about Hawaii.  First, I was in Maui for a week, and I read in the paper that Shell is proposing a second wind farm for the island… and the first was not yet complete. (One thing that puzzled me was that the proposed wind farm was shown on the map to be on a part of the island with the least wind… what’s up with that?) 

When both farms are operational, Maui will be getting about 20% of its electricity from wind.  It will be an interesting experiment in terms of how much wind a system can handle… 20% is the most often quoted number, but Maui will definitely put that to the test, since it is a small, closed system… the Danes also get about 20% of their electricity from wind, but when they have excess electricity on windy nights with low deman, they can sell the excess to Germany.  In Maui, excess electricity has nowhere to go.Still, while there are costs to adding a variable resource like wind to the electric grid, these costs have been overblown.  They do not take into account the risks associated with alternative generation such as nuclear (which has to be shut down completely for refueling every few months) and gas (which is subject to extremely volatile energy prices.) Keep in mind that the electric grid is designed to deal with a loads which are just as variable as wind resource, if not more so, and while different wind farms are producing electricity at different times, electric demand tends to all happen at once, due to air conditioning or heating loads.  In fact, since wind in some locations is very predictable as to when it blows, the variable nature of wind can actually help with this problem.  Last February, we had blackouts here in Denver during a severe cold snap, which was attributed to a shortfall in natural gas generation capacity due to a massive increase in demand by households for gas for heating (a good example of the risks of powering electricity generation with gas.)It turns out that in the windy areas along the northern Colorado border with Wyoming, the wind tends to blow strongest at night… exactly when we were having blackouts due to lack of generation capacity in Denver.

Wind’s variability may end up being an asset, instead of the liability it is made out to be. Maui will be an interesting test case for that. 

[Side note: I’ve noticed that a lot of people are finding this article by typing “Will Maui wind farm pay for itself” in search engines.  So I thought I’d answer that question.  Yes.  This project is projected to cost $300 million.  It’s a 40MW faceplate capacity.  Given a typical 30% capacity factor, and sells its electricity for 10 cents per kWh, it will generate over $300 million in revenues in three years.  On Maui, 94% of non-wind electricity generated from fuel oil, and I can’t find a reference for the cost per kWh of generation from imported fuel oil but we can safely assume that it’s more than the cost of generation from coal or natuaral gas on the continent, which ranges from 2 to 6 cents per kWh, hence my assumption of 10 cents per kWh price.  However, at the extremely conservative price of 5 cents per kWh, the farm will still pay for itself in 6 years.]

My wife and I also took some time off from snorkeling to tour the Alexander & Baldwin Sugar Museum, which got me thinking about ethanol.  Ethanol from corn, as it is normally made in the
US is not a very economic proposition without subsidies (of which there are many) and the energy balance is not great, either.  However, Brazil has been quite sucessful at producing ethanol from sugar, and it takes less energy to produce ethanol from sugar than from corn.  In fact, Brazilian ethanol producers are so sucessful that the US feels the need to impose a tariff of $.54 a gallon.

According to the President of the Hawaiian Solar Energy
, whom I bumped into at Solar 2006, there is currently a pilot plant for making ethanol from molasses, which sounds like a great idea to me, because molasses is practically a waste product of sugar refining… it’s shipped to California and fed to cattle. 

The final recent appearance of Hawaii in my lfe came at a Rocky Mountain Institute event in Snowmass, last week, when I got to talk to a couple of RMI’s staff about the work they are doing there.  They’re working with Governor Lingle, as well as the utilities and the regulators there to completely redesign the rules by which the energy game is played. 

Typically, the largest barriers to the adoption of energy efficiency and renewable energy are perverse incentives in the way that utilities are compensated.  Ratepayers typically pay the electricity prices based on how much the utility pays for its fuel.  Hence, there is no incentive for the utility to manage fuel price risk, because someone else picks up the tab when prices rise; the utility is typically gauranteed a fixed return on investment, no matter how bad those investment decisions were in the first place… just so long as they can get the Public Utility Commission to sign off on the investment at the time.

Another perverse incentive for utilities is that typically they make more money if the customer buys more electricity, so it is very difficult to design a system in which the utility encourages its customers to use energy more efficiently, or generate electricity on site.  At the Intermountain CHP Summit, I heard of a couple cases when a utility heard that a customer was looking into generating their own electricity, and the utility preemptively decided to lower their rates for that customer, making the proposed project uneconomic.

According to RMI staffers, they’re helping design a new regulatory regime for Hawaii, with input all the interested parties, which removes these perverse incentives.  The rate structure will be changed so that the utilities will actually be rewarded for helping their customers become more efficient users of electricity, etc.

I like what’s happening in Hawaii.  Because they are acting now to deal with rising energy prices and working on a system which will help them control their CO2 emissions, the utilities there will likely be much better equipped than most US electric utilities to deal with the regulation of  CO2 emissions, when that finally happens.  

Investors looking for the steady income stream of an electric utility, who are also concerned about the impact of future CO2 regulation should consider HE (Hawaiian Electric Industries.)

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