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Solar Total Energy Project

Georgia Power commitment

Georgia Power Company has a history of support for nonconventional renewable energy technology, investing millions of dollars in initiatives for development of solar thermal, solar photovoltaic (PV), wind, and biomass. Significant investment began in the 1980s with STEP and construction of a new corporate headquarters in Atlanta, which included active and passive solar energy systems. GPC also supported a major PV project to provide energy for the natatorium on the Georgia Tech campus, used for the 1996 Olympic Games. GPC continues to support development of residential and commercial solar systems and energy conservation measures that make a difference to its customers.

Information sources

The information in this project summary, including scanned photos, is extracted from technical reports, project summaries and presentations produced and widely distributed by GPC during the early 1980s as part of STEP information dissemination and technology transfer initiatives, an important element of the contract work scope [DoE Task 6]. As part of the deliverables associated with this government-financed project, the material is neither confidential nor restricted by special copyright requirements beyond source acknowledgment.

Project history

In 1977, DoE selected a joint proposal by GPC and the Westinghouse Advanced Energy Systems Division from a field of 16 competitors from 14 states for STEP site and commercial application. Design work was completed between 1978 and 1980 under DoE sponsorship (with GPC cost-sharing support) through the construction and test operations phases. The project was formally dedicated and began test operations in May 1982. GPC assumed full responsibility for STEP commercial operation in 1984 and continued the project beyond 1987. The project was conceived by Edward J. Ney, a Westinghouse energy physicist who later became a nationally-recognized expert on solar energy systems. Ney was the Project Integrator while with Westinghouse, later joining GPC as Manager of Solar Operations and STEP Project Manager. He brought the involved parties into a joint-venture agreement and subsequently oversaw design, construction, test operations, commercial operations, and eventual decommissioning and disassembly of the Project.

Site

The site for the five-plus acre project was Solar Circle, along Amlajack Boulevard, in a commercial park within the planned community of Shenandoah, Georgia (now part of the city of Newnan). The location is 35 miles southwest of Atlanta, on the west side of I-85 at Exit 47 (GA Hwy 34 and Bullsboro Drive): 33 24 15.84 N and 84 44 49.33 W.

While STEP was shut down and dismantled by 1991, the site of the collector field is still visible from the air, albeit with brush growing through the crumbling pavement. The overall site includes a renewable energy education center (between the former collector field and Amlajack Blvd.) that has accommodated classes from the University of Georgia and other educational institutions.

Industrial application

The industrial application for the Project was a knitwear factory operated by Bleyle of America Inc. STEP provided a large part of the electricity for the facility, displacing fossil fuels normally used to generate power to run the factory. STEP also provided process heat for absorption air conditioning within the building, as well as steam (downstream from the turbine) for pressing the knitwear products. The building was designed with a series of features for energy efficiency, including reduced height to minimize wall area and interior volume, a 4-ft insulating earthen berm around the building, north-south orientation, heavily-insulated roof and walls, high-efficiency fluorescent lighting, energy-efficient production equipment, and an air conditioning system with an economizer cycle. According to GPC, which monitored the facility energy requirements as part of the STEP design process, energy conserving features alone reduced the factory energy consumption by 46 percent.

Technical description

In general, a olar total energy system captures solar radiation [insolation] to supply high-grade electrical and mechanical energy and low-grade thermal energy for a given application, with any excess electrical power being fed into the power company grid. As described in the technical reports, TEP was a fully cascaded total energy system with parabolic dish solar collectors and steam Rankine cycle power conversion system capable of supplying 100-400 kWe output with process steam extraction. Technical specifications in this section are extracted nearly verbatim from interim project reports published and distributed by GPC. Supporting information is available in this document in section 16.2.3.

STEP utilized a field of 114 parabolic dish solar collectors, each 23 feet in diameter, arranged in alternating rows of 9 and 10 units (12 rows total).

STEP's 23-ft diameter collectors tracked in two directions: east/west daily and north/south seasonally.

Tracking the sun east to west daily, and north/south during the seasons, the collectors concentrated solar energy onto a receptacle at their focal points, heating a circulating silicone-based heat transfer fluid (HTF) to 750F. The HTF was then pumped to a heat exchanger in the generating facility, where the heat was used to boil water to produce superheated (high-pressure) steam, which in turn drove a turbine generator and alternator to produce electricity. Medium-pressure steam (350F) from the turbine was then used for pressing the clothing, which required 1000 lb/hr for normal operations. The remaining low-pressure steam was used to produce chilled water (absorption process) for air conditioning or released through an air-cooled condenser.

Solar Collector Subsystem (SCS): The parabolic dish collectors were fabricated in the field from die-stamped aluminum etal segments laminated with aluminized acrylic reflective firm. Each collector tracked the sun independently in both polar and declination axes to remain focused from sunrise to sunset throughout the year. The receiver at the focal point of each collector was a avity type, capable of receiving an incident concentrated solar flux equal to 235 suns. he concentrated solar flux impinges upon the receiver coil absorptive surfaces enclosed within the insulated cylindrical shell to heat the circulating HTF. The field piping network consisted of welded pipes in the main manifolds, and steel tubing with flexible joints in the branches connecting to the tracking collectors. The entire HTF piping system was thoroughly insulated. Power Conversion Subsystem: This consisted of three-piece pool-type boiler with preheater, boiler and superheater, a steam turbine-alternator rated at 500 KVA, an air-cooled condenser and condensate storage tank, make-up demineralizer, deaerator, and pumps. In normal operation, steam at 720F and 700 psig was generated in the boiler-superheater and delivered to the turbine inlet.

Thermal Utilization Subsystem: This was the condensing medium for the steam and the heat source for the cooling of the knitwear plant. Exhaust heat from the steam turbine was recovered through this subsystem during power generation; however, when the turbine was not operating, steam from the boiler was used directly as the heat source. Steam from the turbine or turbine by-pass was routed to the absorption air conditioning system to cool the facility, with excess heat routed to an air-cooled condenser. Control and Instrumentation Subsystem: STEP control subsystem provided a range of operations from minimum operator control to extensive monitoring and data collection for subsequent analysis as part of DoE test operations requirements. The subsystem partitioned control functions between a minicomputer [state of the art in 1982] and peripheral equipment and micro-processors installed throughout the project infrastructure. The control subsystem received information from the sensors and provided signals to field devices such as drive motors on the tracking collectors and valves throughout the heat transfer system. It also alerted operators to anomalies that might damage the collectors or tracking system.

System Loads: STEP was designed according to electrical, air conditioning and process steam loads already established by the knitwear factory, which began operations during STEP design phase. These parameters, which represent the facility relatively constant peak load profile, were used for system design.

Load Type

Peak Load Requirement for Plant

STEP Capacity

Electrical

161 kW

400 kW

Cooling

1,420 MJ (113 tons[vague])[citation needed]

3,260 MJ (257 tons[vague])

Process steam at 177 C (350 F)

626 kg/h (1,380 lb/h)

626 kg/h (1,380 lb/h)

Meteorology Station: During its operational period, STEP monitored weather and insolation data via a meteorology station at the northeast corner of the collector field, operated and maintained by Georgia Tech faculty and students, it fulfilled a vital role by cross referencing operational data with weather statistics to obtain an accurate performance database for future solar project designers. The original weather station, at ground level, consisted of eight solar radiation and surface weather instruments, support structures and digital data loggers. The original STEP Weather Monitoring Station contained these instruments, which monitored the specified variables.

Instrument

Variable

Horizontal Pyranometer

Global Radiation

Pyrheliometers

Direct Normal Radiation

Resistance Thermometer

Dry Bulb Temperature

Humidity Cell

Relative Humidity

Cup Anemometer

Wind Speed

Wind Vane

Wind Direction

Pressure Transducer

Barometric Pressure

Performance highlights and conclusion

As might be expected with a first-of-a-kind project, STEP encountered numerous electrical and mechanical anomalies during startup and test operations, each of which was resolved and made part of the record for future designers. For instance, the original motors and potentiometers for all 114 collectors had to be removed and waterproofed due to high failure rates in Georgia rainy environment. Overall, STEP achieved these objectives as listed in the 1983 project report:

1. A significant number of engineers, scientists and students were trained and validated as system operators and data analyzers.

2. All major thermo dynamic components met their design values, including the steam turbine generator, collectors, absorption chiller, and high-temperature fluid storage system.

3. Solution of anomalies related to small mechanical components (motors, pumps, potentiometers, and valves) provided invaluable information for future system designers.

4. Additional checkout time and effort applied to the hardware and software aspects of the control and instrumentation system provided a significant base for more efficient designs and checkout procedures for future systems.

5. Formal processes were determined for a variety of test modes, providing a manual of demonstrated procedures for application to other solar thermal systems.

6. Both DoE and Bleyle, STEP two primary ustomers, documented their satisfaction with the Project and reported that all their objectives and requirements were met safely and efficiently. DoE benefited from the wealth of data collected during operations, and Bleyle benefited as the beneficiary of the electrical power and thermal energy provided by the Project.

Subsequent to the end of the 10-year contract period in 1987, operations were continued for another year until a failure of the steam turbine and the need for other high-value replacement components proved too costly for continuation of the Project. STEP was subsequently decommissioned and dismantled during 1990.

Project participants

STEP had a large cast of participants during its first six years, comprising design, development, construction, test operations and data monitoring/assessment. During this period, funding was provided primarily by DoE with support from GPC. The final four years of commercial operation and subsequent shut-down were supported exclusively by GPC.

Design team

General Electric Co. (Valley Forge): http://www.ge.com/company

Lockwood-Greene Engineers (A&E): http://www.lg.com

Scientific Atlanta: http://www.sciatl.com

Dow Corning Corp.: http://www.dowcorning.com

Mechanical Technology Co.: http://www.mticontrols.com

Construction team

Dow Corning Corp.: http://www.dowcorning.com

L.B. Samford Co. [Defunct]

B&W Mechanical Contractors: http://bwmech.com (link nonfunctional)

Joe North Inc.: [Defunct]

General Electric (Daytona Beach): http://www.ge.com/company

Solar Kinetics: http://www.kinetics.net

Site operations team

Georgia Power Company: http://www.gpc.com

Georgia Institute of Technology: http://gatech.edu

Heery & Heery Inc., A&E: http://www.heery.com [now Heery International]

Shenandoah Development Co.: [Defunct]

Owens-Corning Insulation: http://owenscorning.com

Westinghouse Electric Corp.: [Heritage Westinghouse now Defunct]

Bleyle of America: http://www.bleyle.com

Sandia National Laboratories: http://www.sandia.gov

U.S. Department of Energy: http://www.doe.gov

References

1. Ney, E.J. (Manager, Solar Operations), Georgia Power Company. olar Total Energy Project, Shenandoah, Georgia Site: Summary Technical Progress Report (July 1, 1980 through June 30, 1982). Prepared for the U.S. Department of Energy, Division of Solar Energy under Cooperative Agreement DE-AB04-77ET20216.

2. Ney, E.J. (Manager, Solar Operations) and W.H. Weidenbach (Industrial Marketing Manager), Georgia Power Company. evelopment of the Solar Total Energy Project (STEP) at Shenandoah, Georgia (U.S.A.). Paper for the International Solar Energy Symposium, Palma de Mallorca, Spain; October, 1983.

3. Ney, Edward J. (Manager, Solar Operations), Georgia Power Company. olar Energy Training Program: Overview and Course Guide. June, 1984. Prepared under U.S. Department of Energy Cooperative Agreement DE-AB04-77ET20216 [Task 6: Technology Transfer and Information Dissemination].

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