Texas Calls for 317 MW of Compressed Air Energy StorageCompressed-air energy storage, or CAES, is one of the cheapest ways to store really massive amounts of energy for long periods of time. In fact, beyond pumped hydro storage, compressing air when power’s cheap and plentiful and then using it to boost natural gas-fired power turbines during times of peak demand is really one of the only ways to shift hundreds of megawatts of load from one hour to the next.
So why have so few CAES-backed power plants been built? One problem is cost: while they’re much cheaper and easier to site than pumped hydro projects, CAES projects are still massive infrastructure projects at the $100-million-and-up scale.
They also have their geographic restrictions: specifically, the availability of vast underground cavern structures to use as reservoirs for all that compressed air. Then, of course, there are regulatory and economic factors that have limited energy storage’s appeal in general, which apply to CAES as well.
Put caves and power plants together, however, and the energy storage that results is cost-effective and reliable, as the world’s two first CAES projects -- the 290-megawatt plant in Huntorf, Germany, built in 1978, and the 110-megawatt McIntosh, Alabama plant, built in 1991 -- have proven over their combined decades of operation. That’s led to a resurgence of CAES projects over the past half-decade or so, driven by technology advances, as well as grid operators’ growing need for energy storage to balance intermittent wind and solar power with ever-shifting demand.
The latest comes in Texas, where Dresser-Rand and Apex Compressed Air Energy Storage announced last week that they’re building the first big CAES project in the United States in decades. Known as the Bethel Energy Center, the 317-megawatt, $200 million project will serve Texas grid operator ERCOT, and is the first of more to come from the partners, both in the United States and elsewhere, the companies said.
The project is being built near Tennessee Colony, Texas, a rural crossroads about 100 miles southeast of Dallas featuring a church, a general store, and a Calpine natural gas facility. That part of the state has its share of giant underground “salt dome” caverns, suitable for storing natural gas, as well as pumped air.
Dresser-Rand, the Houston-based supplier of “high-speed rotating equipment and services solutions” for the oil and gas industries, also built the equipment for the Mcintosh, Ala. CAES plant in 1991. Since then, it’s developed an integrated energy storage technology, called SMARTCAES, that it’s using in the Bethel project.
greentechmediaIsentropic’s Pumped Heat System Stores Energy at Grid ScaleMark Wagner, the Chairman of Isentropic, spoke at a recent energy event and said that the capital cost for Isentropic's energy storage technology was very low, with "a levelized cost of $35 per megawatt-hour." Jonathan Howes, the CTO of Isentropic, has claimed a path to large-scale storage costs that are an order of magnitude lower than lithium-ion batteries or other stored energy technologies.
In 2012, the firm announced a $22 million investment from the U.K.-government-backed Energy Technologies Institute (ETI).
The short-term goal is to deploy a 1.5-megawatt, 6-megawatt-hour storage unit on a U.K. grid-connected primary substation owned by Western Power Distribution, a distribution network operator with 7.7 million customers -- and to get it to demonstration scale.
Wagner, the company's Chairman, shared some conclusions on energy storage based on what he called a "whole-systems approach" in the form of a U.K. grid model developed with a university. The grid model accounts for all generation assets, transmission and distribution, and interconnection.
According to the model, the value of storage decreases after the third hour. Wagner said, "Three hours is enough," adding, "Distributed storage is significantly more valuable than centralized storage."
Wagner takes the stance that "peak shifting is the most valuable thing you can do -- but there is no value after six hours; optimum is about 3 hours." He also said that "The value of storage depends strongly on the nature of the system." With a renewable penetration of greater than 50 percent, storage has a "huge value." Wagner believes that high frequency storage is much less valuable.
greentechmedia
Human history becomes more and more a race between education and catastrophe. H. G. Wells.
Fatih Birol's motto: leave oil before it leaves us.