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.
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.