(Isothermal) Compressed-Air System Could Aid Wind Power

[OKIsItJustMe]

http://www.technologyreview.com/energy/37896/?p1=A4

Energy

Compressed-Air System Could Aid Wind Power

A startup says its compressed-air technology could do a better job of storing the power generated by wind turbines.

Tuesday, June 28, 2011 | By Prachi Patel

http://www.sustainx.com/index.html">SustainX, a startup in West Lebanon, New Hampshire, has received $20 million in venture capital to test its compressed-air energy storage technology on a large scale.

The technology could allow for a wider use of compressed-air storage, which in turn could make renewable energy more attractive, since it would allow wind power generated at night to be stored until daylight hours, when http://www.technologyreview.com/energy/26247/">demand is higher. If it's successful, the technology could decrease the need to build natural gas plants to supply peak power demand.

The need for storage is http://www.technologyreview.com/energy/37699/">increasing as governments mandate the use of http://www.technologyreview.com/energy/32383/">more renewable energy. SustainX has demonstrated a 40-kilowatt prototype and is now completing a one-megawatt system, slated to be deployed next year with the power company AES.

In conventional compressed-air storage, electricity is used to compress air, which is stored in underground caverns or aquifers. That air is then released to drive a turbine-generator to produce electricity when needed. Such storage costs roughly a tenth of what battery storage costs, but it isn't used much because in large part because it requires a location with underground storage space. SustainX's system eliminates this problem because it can efficiently use above-ground storage tanks rather than caverns.

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[Tesha]

1. General Compression is another company involved in this. (NT)

http://www.generalcompression.com/

This is the sort of technology that will make
renewables fully competitive with thermal base
load power plants.

Tesha

[OKIsItJustMe]

2. Indeed

If you continue on in the article, you will find them mentioned as well.

[kristopher]

5. That isn't their market niche;.

This creates another form of flexible generation that finds its main value in shaping the variable load of high penetration renewables around demand.

It would be a total failure as a competitive replacement for "baseload", which is an economic artifact of centralized thermal, not a technical necessity with added value.

[Gregorian]

3. Nope. Not buying it.

I don't see the benefit to generating directly at the source, and storing in batteries. The question of storage is no doubt legitimate, but is being challenged through diversity of generating sources.

Even though it's not adiabatic, it's big enough that being isothermal, it's essentially adiabatic. Or something like that. So it's an interesting idea that is probably just interesting.

[Bill USA]

4. very interesting.

[pnwest]

6. eh?

gonna use electricity, to make compressed air, to make more
electricity?

[FBaggins]

8. Close

Going to use free electricity that you have no use for now to make compressed air to make more electricity when you do need it.

[OKIsItJustMe]

7. 3.1. Current State of Electric Storage

http://www.oe.energy.gov/DocumentsandMedia/OE_Energy_Storage_Program_Plan_Feburary_2011v3.pdf

…

3.1. Current State of Electric Storage

Currently, energy storage is utilized in the grid primarily for diurnal energy storage, to enable use of cheap baseload energy, available at night, for serving high daytime loads that would otherwise require expensive peaking power plants. These plants (primarily pumped hydroelectric plants) are effective, and have some capacity to provide grid support for shorter-term imbalances (10s of minutes). However, these plants tend to be large, capital intensive, and with specific siting requirements.

A number of existing EES technologies can be potential candidates for other grid applications. These EES technologies store electricity either directly in charges or via energy conversion into a different form of energy. Super-capacitors are an example of a direct charge type of storage that features high power but low energy. Most of EES technologies involve energy conversion from electricity to kinetic energy, potential energy, or chemical potential. Flywheels are an EES technology that store electricity in kinetic energy. Like direct storage, flywheels are characterized by high power but low energy, and thus are most suitable for the category of power management. Compressed-air and pumped-hydro storage are capable of a very large amount of electricity energy, allowing hours or even longer duration, but are not well suited to power quality management. The largest group of EES technologies is the one that stores electricity in chemical (or electrochemical) potential driven by an external voltage. These EES technologies include redox flow batteries, Na-based batteries, and Li-ion batteries. With some limitations, batteries are capable of uptake and release of electrical energy rapidly or over a longer time period, and thus are potentially applicable to both power and energy applications depending on performance characteristics of a specific technology. The chart in Figure 3-3, again generic in nature, includes an overlay of some current energy storage technologies on the operational and application characteristic space already presented in Figure 3- 2. While not inclusive of all energy technologies, this overlay shows the diversity of applications even for technologies within a single class.

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[txlibdem]

10. +1, The greatest benefit to the utility is avoiding the use of expensive "Peaking" plants

from your quote: "energy storage, to enable use of cheap baseload energy, available at night, for serving high daytime loads that would otherwise require expensive peaking power plants"

These plants generally burn natural gas but have to be ramped up to full power too quickly to burn it efficiently. In addition, they sit idle for much of the day and are almost never used at night --so they have to pass along the entire cost of building and operating the plant to the utility for the brief period each day that they are needed (read: more expensive power). Third, since these plants are burning inefficiently they are no doubt putting out more greenhouse gases such as methane (which is known to be 17 times as harmful to the climate as CO2).

So the greatest benefit of energy storage for renewables to you and me is cleaner air and possibly a smaller rate hike next year from the electric company (ok that one probably won't happen but it's nice to dream). To me, just knowing that no wind farm will have to temporarily shut down its power output because the grid doesn't need the power right at that second --you and I will receive that electricity later in the day or tomorrow as needed.

As I recall, on March 23, 2010 the wind farms in the Texas Panhandle had to be shut down --because they were putting out far too much power for the electrical lines to take, so they shut down the wind generation to protect the lines from damage! Wind power without energy storage will be shut down when things like that happen. Wind power WITH energy storage can just save that excess power for use later.

EJ Peaker Power Plants - NYC by ssbx

This map details all the peaker power plants located within a 1/2 mile radius of an environmental justice community (as defined by NYSDEC). "Peaker" is a designation given to power plants that are only intended to operate on high electrical demand days when the generating capacity of base load plants is strained, like on hot summer days. Peaker plants often emit more pollution per unit of energy produced than base load plants. All of the peaking units shown in this map operate without post-combustion pollution controls.

http://habitatmap.org/profiles/41
...Note: you can select EJ Peaker Power Plants on that page and click View Map to see the ones that are constructed in environmentally sensitive areas.

[Grids]

9. CAES already available

It will be interesting to see what the newer version of CAES technology costs, particularly in terms of storage cost per MWh. A key advantage of underground-based CAES is the relatively low cost of constructing the air cavern (if you're using salt geology). It allows for an extremely low cost of construction per MWh of storage. Allowing for multiple hours of storage in places where there is neither that geology nor good pumped storage sites is a good thing. But the opportunity for CAES already exists. The article didn't mention the Iowa Stored Energy Project - CAES using aquifer-based storage. Gridflex Energy has a CAES project in Kansas that would directly serve wind development in the area. As for the inevitable question of efficiency, round-trip efficiency of energy in-energy out for conventional CAES is about 55%. But this figure shouldn't be used to compare CAES with batteries and pumped storage, because CAES is a mixture of mechanical storage (like pumped storage) and thermal generation (like a gas turbine). 55% actually is favorable as a generation efficiency when compared with conventional gas-fired combined cycle generation.

[Kaleva]

11. Read an article about how this could be used with solar.

During the day, a certain percentage of solar power being generated would drive compressors that would build up the pressure in underground sites up to about 1000 psi. At night, the air would be released to facilitate natural gas driven turbines.

[txlibdem]

12. For Solar PV, yes, but Concentrating Solar Thermal has an even better energy storage

...and that is by using molten salt heat storage.