K. Scott Rawlinson

Status of the Advanced Dish Development System Project

The Advanced Dish Development System (ADDS) project is a system-level dish/engine development activity aimed at the extensive but challenging remote power market. The ADDS project involves integration and test of advanced dish/Stirling systems. The ADDS designs utilize the WGAssociates solar concentrator and controls, and the SOLO 161 Stirling Power Conversion Unit. Development has focused on extending the application of dish/Stirling systems to water pumping, and reliability and performance improvement. Testing includes unattended, automatic operation of stand-alone dish/Stirling solar power generation systems in both on and off-grid modes at the National Solar Thermal Test Facility (NSTTF) in Albuquerque, NM. In 1999, a first generation (Mod 1) system was fielded at the NSTTF and routine unattended operation initiated. In 2000, a system reliability tracking system was implemented on the Mod 1 system and an upgraded, second-generation (Mod 2) system, including a stand-alone water-pumping capability was developed. In 2001 and 2002 system performance and reliability were improved. Overall, the ADDS project has been successful with most of the original system specifications and objectives having been met or exceeded. The ADDS designs are efficient and maintainable and have proven the ability to operate autonomously in a remote environment. The Mod 1 system net power rating was increased from 9 to 10 kWe even while the concentrator mirror area was reduced by over 14%. The Mod 2 design is the first modern dish/engine system to operate independent of the utility grid and is capable of interfacing with standard three-phase, 480-volt, water-pump or other single motor applications. In this paper, the ADDS project plan and history, technical approach, and the major system components and features are briefly described. Project milestones and status along with test results are also presented.© 2003 ASME

Improved alignment technique for dish concentrators.

Parabolic dish concentrators have shown significant promise of generating competitive electric energy for grid and off-grid applications. The efficiency of a dish-electric system is strongly affected by the quality of the concentrator optics. Most parabolic systems consist of a number of facets mounted to a support structure in an approximate parabolic arrangement, where the individual facets have spherical or parabolic optical shapes. The individual facets must be accurately aligned because improper alignment can compromise performance or create hot spots that can reduce receiver life. A number of techniques have been used over the years to align concentrator facets. In the Advanced Dish Development System (ADDS) project, a color look-back alignment approach that accurately aligns facets (mirror panels) and in addition indicates quantitative information about the focal length was developed. Key factors influencing the alignment, some of which had very large effects on the quality of the alignment, were also identified. The influence of some of the key factors was characterized with a flux mapping system on the second-generation ADDS concentrator. Some of these factors also affect other alignment approaches. The approach was also successfully applied to two other concentrators with differing facet arrangements. Finally, we have extended the method to a 2-f approach that eliminates the need for a distant line-of-sight to the dish and permits alignment at near vertical dish attitudes. In this paper, we outline the color look-back alignment approach, discuss the key alignment factors and their effect on flux distribution, and discuss extensions to non-gore dishes. A companion paper discusses the 2-f color alignment approach in detail.© 2003 ASME

Design, fabrication and testing of a 15-kW gas-fired liquid-metal evaporator

This paper describes the development and testing of a compact heat- pipe heat exchanger that is designed to transfer thermal energy from hot combustion gases to the heater tubes of a 25-kW{sub e} Stirling engine. In this system, sodium evaporates from a surface that is heated by a stream of hot gases and the liquid metal then condenses on the heater tubes of a Stirling engine where energy is transferred to the engine`s helium working fluid. Recent tests on a prototype unit illustrated that a compact (8 cm {times} 13 cm {times} 16 cm) sodium evaporator can routinely transfer 15-kW{sub t} of energy at an operating vapor temperature of 760{degrees}C. Four of these prototype units will eventually be used to power a 25-kW{sub e} Stirling engine system. Design details and test results from the prototype unit are presented in this paper.