James E. Pacheco

Engineering aspects of a molten salt heat transfer fluid in a trough solar field

An evaluation was carried out to investigate the feasibility of utilizing a molten salt as the heat transfer fluid (HTF) and for thermal storage in a parabolic trough solar field to improve system performance and to reduce the levelized electricity cost. The operating large-scale solar parabolic trough plants in the USA currently use a high temperature synthetic oil in the solar field consisting of a eutectic mixture of biphenyl/diphenyl oxide. The scope of the overall investigation included examination of known critical issues, postulating solutions or possible approaches where potential problems existed, and the quantification of performance and electricity cost using preliminary, but reasonable, cost inputs. The two leading candidates were the so-called solar salt (a binary salt consisting of 60% NaNO3 and 40% KNO3) and a salt sold commercially as HitecXL (a ternary salt consisting of 48% Ca(NO3)2, 7% NaNO3, and 45% KNO3). Operation and maintenance (O&M) becomes an important concern with molten salt in the solar field. This paper addresses that concern, focusing on design and O&M issues associated with routine freeze protection, solar field preheat methods, collector loop maintenance and the selection of appropriate materials for piping and fittings.

Final Test and Evaluation Results from the Solar Two Project

Solar Two was a collaborative, cost-shared project between 11 U. S. industry and utility partners and the U. S. Department of Energy to validate molten-salt power tower technology. The Solar Two plant, located east of Barstow, CA, comprised 1926 heliostats, a receiver, a thermal storage system, a steam generation system, and steam-turbine power block. Molten nitrate salt was used as the heat transfer fluid and storage media. The steam generator powered a 10-MWe (megawatt electric), conventional Rankine cycle turbine. Solar Two operated from June 1996 to April 1999. The major objective of the test and evaluation phase of the project was to validate the technical characteristics of a molten salt power tower. This report describes the significant results from the test and evaluation activities, the operating experience of each major system, and overall plant performance. Tests were conducted to measure the power output (MW) of the each major system, the efficiencies of the heliostat, receiver, thermal storage, and electric power generation systems and the daily energy collected, daily thermal-to-electric conversion, and daily parasitic energy consumption. Also included are detailed test and evaluation reports.

Sandia National Laboratories' work in solar detoxification of hazardous wastes

Abstract Sandia National Laboratories is working with the Solar Energy Research Institute to develop and apply solar technology to the destruction of hazardous chemicals. The program is part of the United States Department of Energys Solar Detoxification of Hazardous Waste Initiative. Sandias efforts are focused on two distinct technologies for destroying chemical wastes: a low-temperature, photocatalytic process for destroying dilute organic compounds in water and a high-temperature, thermal-catalytic process that destroys organic wastes by steam reforming over a metal catalyst. In support of both areas, laboratory studies are performed to screen alternative concepts, to identify reaction products, and to quantify key processing parameters. Sandias experiments are conducted in the field with sunlight at a scale approaching that needed for industrial applications. The objective of Sandias efforts is to spur commercial application of these technologies by demonstrating their feasibility at this practical scale.

Evaluation of a Molten Salt Heat Transfer Fluid in a Parabolic Trough Solar Field

An evaluation was carried out to investigate the feasibility of utilizing a molten salt as the heat transfer fluid (HTF) and for thermal storage in a parabolic trough solar field to improve system performance and to reduce the levelized electricity cost. The operating SEGS plants currently use a high temperature synthetic oil consisting of a eutectic mixture of biphenyl/diphenyl oxide. The scope of this investigation included examination of known critical issues, postulating solutions or possible approaches where potential problems existed, and the quantification of performance and electricity cost using preliminary, but reasonable, cost inputs. The two leading candidates were the so-called solar salt (a binary salt consisting of 60% NaNO3 and 40% KNO3 ) and a salt sold commercially as HitecXL (a ternary salt consisting of 48% Ca(NO3 )2 , 7% NaNO3 , and 45% KNO3 ).Copyright