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Tri-State’s research projects range from compressed air storage to improved transmission reliability


Compressed-air energy storage plant

In addition to working through a long list of project improvements to its generation and transmission system in 2009, Tri-State is ramping up research and development studies that could bring even greater value to the power it provides to its membership.


In addition to Tri-State’s ongoing participation in several carbon capture and sequestration research and demonstrations projects, the G&T has also partnered with the Electric Power Research Institute (EPRI) and, in some instances, other utilities on at least four projects ranging from gaining improvements in transmission line-loading data to a possible future investment in a compressed-air energy storage facility.



Solar-assist project studied


With a goal of increasing power plant efficiency while incorporating renewable technologies, the association is studying a solar project for Escalante Station. 


According to Riley Moore, senior engineer, Tri-State is working with EPRI on a study to explore the viability of siting concentrating, trough-type solar collectors to supply heat to Escalante Generating Station’s steam reboiler.  This would allow for a full return of cold reheat steam to the plant’s boiler and would boost steam turbine output closer to the rated capacity of the plant, thereby improving overall station performance. 


Tri-State is also participating with several other utilities on an ancillary solar-to-steam study project that could be applied at natural gas-fueled, combined-cycle plants in Arizona, Nevada and other states.


Other potential benefits of a solar-augmented steam-cycle facility include adding utility-scale solar power generation without the challenges of siting a new plant and new power block, reducing the plant’s CO2 footprint, as well as gaining valuable experience with solar thermal technologies to assess their future potential in the utility’s generation mix.



ITM could boost advanced coal plants


The G&T is studying a new technology under investigation by EPRI that could be applied in an advanced coal plant, such as an integrated gasification combined-cycle (IGCC) or an oxy-combustion unit.  IGCC is a process in which a fuel, such as coal, is converted to low heating value, high-hydrogen gas in a process called gasification.  The gas is then used as a primary fuel to operate a gas turbine.


Successful application of this technology could be a critical next step in viably moving forward with a fleet of clean coal-fueled power plants.  The process, referred to as ion transport membrane (ITM), uses dense, nonporous, mixed-conducting ceramic membranes to separate oxygen from air for use in an IGCC plant’s gasifier. 


Potential benefits of this unique technology are a 7 percent reduction in the capital costs associated with an IGCC plant, a dramatic reduction in the internal power required in the IGCC process and a decrease in the oxygen footprint of an IGCC plant by up to 50 percent.  Tri-State’s participation in this research would partially support the testing of a pre-commercial test unit that could be integrated with a 5-to-15-megawatt gas turbine.



Compressed-air storage


Tri-State is working to host a compressed-air energy storage (CAES) demonstration project in its service territory.  The G&T is pursuing an effort with EPRI that could site a project in eastern Colorado, which could help the G&T and other participating utilities further develop the next generation of this promising energy storage technology.


CAES plants use off-peak electricity to compress air into a storage system such as a tank or underground cavern. When electricity is needed, the air is withdrawn from the storage vessel, heated (usually with gas or oil) and processed by an expansion turbine to drive an electric generator.


Tri-State could eventually use CAES technology to augment the intermittent characteristics of renewable generation such as wind power.  The utility applications for bulk energy-storage CAES plants include peak shaving, load management, load following, frequency regulation, spinning reserve and wind energy storage and dispatch.


Compressed-air energy storage (CAES) power plants are not a new technology. PowerSouth Energy Cooperative has operated its 348-megawatt CAES McIntosh Power Plant in Alabama since 1991. This first generation CAES unit at McIntosh produces 110 megawatts of capacity in conjunction with two gas-fired combustion turbines to achieve the total output of 348 megawatts. It remains as the only utility-scale CAES plant operating in the United States today.



Power line rating methods


One study aimed at reviewing and standardizing line rating methodologies is being spearheaded by Tri-State’s Mark Graham, transmission planning manager, and his engineering staff.  As transmission line loads increase and warm temperatures heat up lines, ground clearance must be maintained and conductors must be protected from overheating to prevent permanent damage.


“With the help of EPRI’s statistical studies, we plan to develop standardized benchmarks for rating power lines,” explained Graham.  “This research will help us more precisely estimate how much power can safely be transferred on transmission lines at various times of the year at different locations.”




Updated: January 15, 2009




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