Parabolic Trough Empirical |

A parabolic trough system is a type of concentrating solar power (CSP) system that collects direct normal solar radiation and converts it to thermal energy that runs a power block to generate electricity. The components of a parabolic trough system are the solar field, power block, and in some cases, thermal energy storage and fossil backup systems. The solar field collects heat from the sun and consists of parabolic, trough-shaped solar collectors that focus direct normal solar radiation onto tubular receivers. Each collector assembly consists of mirrors and a structure that supports the mirrors and receivers, allows it to track the sun on one axis, and can withstand wind-induced forces. Each receiver consists of a metal tube with a solar radiation absorbing surface in a vacuum inside a coated glass tube. A heat transfer fluid (HTF) transports heat from the solar field to the power block (also called power cycle) and other components of the system. The power block is based on conventional power cycle technology, using a turbine to convert thermal energy from the solar field to electric energy. The optional fossil-fuel backup system delivers supplemental heat to the HTF during times when there is insufficient solar energy to drive the power block at its rated capacity. The empirical parabolic trough model uses a set of equations based on empirical analysis of data collected from installed systems to represent the performance of parabolic trough components. The model is based on Excelergy, a model initially developed for inernal use at at the National Renewable Energy Laboratory. For a description of the type of parabolic systems that Solar Advisor can model, see About the Solar Advisor Model. For information about the physical parabolic trough model, see Parabolic Trough Physical. Note. Many of the input variables in the parabolic trough model are interrelated and should be changed together. For example, the storage capacity, which is expressed in hours of thermal storage, should not be changed without changing the tank heat loss value, which depends on the size of the storage system. Some of these relationships are described in this documentation, but not all. If you have questions about parabolic trough input variables, please contact Solar Advisor Support at solar.advisor.support@nrel.gov. To use the parabolic trough empirical model:
• | Open the sample parabolic trough sample template: On the File menu, click Open Sample Template and choose Sample Parabolic Trough Systems from the list, or
• | In the Technology and Market window, choose Concentrating Solar Power, Empirical Trough System.
The sample template contains four cases. The first three cases use the physical trough model, and the fourth case uses the empirical model. The fourth case represents a 100 MW baseline system with a medium temperature heat-transfer fluid and an indirect 2-tank thermal energy storage system. The parabolic trough input pages for this option described in this section are:
• | Trough System Costs
• | Solar Field
• | SCA / HCE (solar collector assembly / heat collection element)
• | Power Block
• | Thermal Storage
• | Parasitics
• | User Variables