THE DISS PROJECT : DIRECT STEAM GENERATION IN PARABOLIC TROUGHS OPERATION AND MAINTENANCE EXPERIENCE UPDATE ON PROJECT STATUS
The DISS (DIrect Solar Steam) project is a complete R+TD program aimed at developing a new generation of solar thermal power plants with direct steam generation (DSG) in the absorber tubes of parabolic trough collectors. During the first phase of the project (1996-1998), a life-size test facility was implemented at the Plataforma Solar de Almería (PSA) to investigate under real solar conditions the basic DSG processes and evaluate the open technical questions concerning this new technology. This paper updates DISS project status and explains O&M-related experience (e.g. main problems faced and solutions applied) with the PSA DISS test facility since January 1999. NOMENCLATURE DAS Data acquisition system DISS Direct solar steam (the project) DSG Direct steam generation (the process) PSA Plataforma Solar de Almería P Pressure T Temperature INTRODUCTION Solar thermal power plants based on parabolic trough collectors are presently the most successful solar technology for electricity generation, as demonstrated by the SEGS plants in California. Direct steam generation in the absorber tubes is seen as a promising option to further the competitiveness of this technology. Replacement of the oil by direct steam generation results in lower investment and operating costs, as well as reduced environmental risk and fire hazards in case of leaks. Simultaneously, the performance can be improved by avoiding the thermodynamic losses associated with the oil water/steam heat exchanger of the SEGS plants. In combination with further improvements of the collector field and overall system integration, a 26% reduction in the electricity cost seems to be achievable (Langenkamp, 1998). Taking into consideration this expected benefit, a group of German and Spanish partners, with the financial support of the European Commission JOULE Programme, started in 1996 the DISS (Direct Solar Steam) project, which is an R+D program aimed at developing a new generation of solar thermal power plants with parabolic trough collectors. Expected improvements are based on three main factors: 1. Development and implementation of improved components for parabolic trough collectors (e.g. new, more economical absorber tubes with good optical and thermal properties; cheaper sun-tracking systems; better mirrors, etc...). 2. Development of the Direct Steam Generation (DSG) process to eliminate the oil used at the existing solar thermal plants as a heat carrier from the solar field to the power block. Since the DSG process is a promising way
A survey on control schemes for distributed solar collector fields. Part II: Advanced control approaches
This article presents a survey of the different advanced automatic control techniques that have been applied to control the outlet temperature of solar plants with distributed collectors during the last 25 years. A classification of the modeling and control approaches described in the first part of this survey is used to explain the main features of each strategy. The treated strategies range from classical advanced control strategies to those with few industrial applications.
CFD simulation of hydrodynamics and heat transfer in gas phase ethylene polymerization reactors
Abstract The hydrodynamics and temperature of a two-dimensional gas–solid fluidized bed of gas phase olefin polymerization reactor had been studied. A two-fluid Eularian Computational Fluid Dynamics (CFD) model with closure relationships according to the kinetic theory of granular flow has been applied in order to simulate the gas–solid flow. Fluidization regime and gas–solid flow pattern were investigated using three different drag models. Model predictions of bed pressure drop were compared with corresponding experimental data reported in the literature to validate the model. The predicted values were in reasonable agreement with the experimental data. The temperature behavior of fluidized bed with various drag models was investigated. The temperature gradient in the primary section of the bed was much larger than the gradient in other sections and the effect of all drag models on temperature gradient along the bed was approximately similar.