New Compressed Air Storage Deals Fatal Blow To Zombie Lies About Wind And Solar

We don’t expect the wind and solar naysayers to give up any time soon, but new utility-scale energy storage solutions are beginning to come on line, and they will put to rest this whole notion that intermittent energy sources (namely, wind and solar) can’t provide a significant proportion of reliable power to the national grid.

The latest development comes from a company called SustainX, Inc. The technology is called an isothermal compressed air energy storage system, and since we’ve been following its progress for the past several years we’re happy to tell you that SustainX has completed construction of its first utility scale system. It was hooked up to the grid earlier this month and it’s now in the process of revving up to speed.

Isothermal Compressed Air Energy Storage System

An Isothermal Compressed Air Energy Storage System

We first took note of SustainX back in 2009, when it spun out of Dartmouth College. The goal was to store four megawatt-hours worth of energy in transportable 40-foot long containers, while achieving a 70% reduction in the amount of energy needed for conventional compressed air energy storage (CAES) systems.

Last year, the company took a big leap forward by entering a technology licensing agreement with the University of Minnesota.

Isothermal refers to storage of compressed air at a constant temperature, which is a key element in the improved energy efficiency of the system.

The new SustainX CAES system is located in New Hampshire, at the SustainX headquarters. As SustainX describes it, the new system represents a next-generation improvement over earlier CAES systems dating back to the 1970′s which typically are located underground and run on fossil fuel.

The SustainX system was designed to run on grid-supplied electricity, so depending on the local grid mix it can potentially run exclusively on emission free sources including wind and solar. That also means that it is not dependent on caves or other geological quirks for site selection.

Some patented, cutting edge tweaks by SustainX make all the difference, but other than that, the entire system consists of practically nothing but steel, water, and air. Here’s how it works:

A mechanical drivetrain utilizes an electric machine and a crankshaft…This efficient mechanical link powers a two-stage, mixed-phase (water-in-air) heat-transfer process within pneumatic cylinders. During piston strokes, water is sprayed into the air-filled chamber of each cylinder, allowing heat to be transferred from water to air during expansion or from air to water during compression. The same ICAES power unit provides both isothermal compression and expansion, eliminating the cost of separate compressor and expander subsystems.

We Built This CAES!

If the new facility proves successful we taxpayers can all do a group hug because SustainX received a $5.4 million award from the Department of Energy to help accelerate the project, as part of the Obama Administration’s Smart Grid initiatives.

The project, which also includes private sector investors, appears to be on track. Completion of the test phase is due by the end of this year and a final technology report is due in 2015.

CAES and other new storage technologies fit into the Smart Grid concept partly by eliminating the need to construct new peaking plants. Peaking plants, which typically run on natural gas, are designed to come on line quickly to address demand spikes, but most of the time they sit idle, which means that they are a very expensive way to provide for variations in local energy consumption to say nothing of their dependence on fossil fuel sources.

In terms of the levelized cost of energy (LCOE, not to be confused with EROI), a mechanically simple system like the SustainX solution has some clear advantages over building new peaking plants, including the potential for far lower operating, maintenance and repair costs in addition to lower fuel costs.

In the past, CAES systems were primarily sited to take advantage of caves and other geological quirks, so the Smart Grid goal of developing more geographically flexible, above ground systems is also critical if CAES is to play a major role in the national grid. More

 

Making clean energy pay off by storing it as squeezed air

A stumbling block to increasing our reliance on electricity from cleaner energy sources such as solar panels and wind farms has always been figuring out how to efficiently store the energy for use when the wind isn’t blowing and the sun isn’t shining. Danielle Fong could make clean energy significantly more practical on a large scale by introducing a novel way to use tanks of compressed air for energy storage. “It could radically reorient the economics of renewable energy,” she says.

Danielle Fong

The idea of using compressed air to store energy is not new. Electricity from solar panels or wind turbines can turn a motor that’s used to compress the air in a large tank, and the air pressure can then be converted into power to drive a generator when the power is needed. The problem is that during compression the air reaches temperatures of almost 1,000 °C. That means energy is lost in the form of heat, and storage in conventional steel vessels becomes impractical.

Fong stumbled on a possible solution while skimming through a nearly century-old book: water spray is great at cooling air. She asked, why not spray water into the air while compressing it, so that the air stays cool? To make the process practical, she developed a technique for separating the heated water from the compressed air and diverting the water into a tank, so the heat can be recaptured to minimize energy loss. The process is about as efficient as the best batteries: for every 10 kilowatt-hours of electricity that goes into the system, seven kilowatt-hours can be used when needed.

Fong founded a company called LightSail Energy in Berkeley, California, to develop the technology. Initially, she planned to produce compressed-air-powered scooters. But backer Vinod Khosla of the venture capital firm Khosla Ventures convinced her to go after the much bigger market of electricity for the power grid.

Batteries are the current state of the art in storing excess wind and solar energy, but Fong says the LightSail system will cost less to purchase and will last for a decade or more. Over the long term, she says, the system could cost as little as one-tenth as much to own and operate as batteries do. A single system, which is about the size of a shipping container plus a car-size unit, will store the energy generated by a one-megawatt wind turbine running for three hours. More