Handbook of Energy Storage for Transmission or ... - W2agz.com

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for holding and cycling compressed air. The tests that EPRI performed at the Pittsfield site (after
taking over the project from DOE) indicated that compressed air could be stored and cycled
successfully in the St. Peter sandstone underneath the Pittsfield site. However, if air is left in this
sandstone for more than three months before it is cycled, the stored air starts to react with local
pyrites in the sandstone, causing a reduction in the concentration of oxygen. It has been
hypothesized that, at some point, the oxidation process would be self-limiting at the site.
Lessons learned
During construction and initial operation of the McIntosh and Huntorf plants, the project
participants conducted a number of optimization studies and analyses related to various aspects
of the CAES plant engineering and operations. The lessons learned – some of them of a
conceptual nature and some related to engineering details – have been presented in technical
publications [23] and EPRI reports.
The generic conceptual findings are summarized as follows:
• CAES plants can be built within estimated funds and schedule.
• The plants confirmed the expected high efficiency, reliability, availability, and competitive
economics.
• The underground storage caverns were developed using well-established techniques and were
completed on time within budgeted funds.
• Careful optimization of the CAES plant design can significantly enhance plant economics.
For example, the McIntosh plant was optimized based on specified off-peak and peak hours,
off-peak and on-peak power costs, fuel costs, and cost equations describing equipment and
storage costs as a function of major cycle parameters.
• The recuperator requires a particular care in its design. The so-called Advanced Recuperator
[11] is used to prevent the tubes from operating at temperatures below the dew point.
• Underground storage reservoirs can achieve negligible leak rates.
• The negligible amount of sodium chloride in the compressed air drawn from salt caverns
does not cause corrosion problems in the aboveground turbomachinery equipment.
• The role of the house engineer involved in the CAES project is very important because there
is no standard CAES plant. To minimize plant costs and to enhance the plant performance
and operations, the house engineer should integrate and optimize the aboveground and
underground components and systems for the specific site conditions and economic
parameters of the plant owner.
• CAES plants can be constructed using commercially available equipment; mainly
components developed for the combustion turbine and oil/gas industries over that last 50
years.
Compressed Air Energy Storage (CAES) Page 20