An introduction to heat transfer

Solar Engineering Of Thermal Processes

Introduction to heat transfer

A concentrating solar power (CSP) system converts sunlight into a heat source which can be used to drive a conventional power plant. Thermal energy storage (TES) improves the dispatchability of a CSP plant. Heat can be stored in either sensible, latent or thermochemical storage. Commercial deployment of CSP systems have been achieved in recent years with the two-tank sensible storage system using molten salt as the storage medium. Considerable research effort has been conducted to improve the efficiency of the CSP system and make the cost of electricity comparable to that of the conventional fossil-fuel power plant. This paper provides a comprehensive summary of CSP plants both in operation and under construction. It covers the available technologies for the receiver, thermal storage, power block and heat transfer fluid. This paper also reviews developments in high temperature TES over the past decade with a focus on sensible and latent heat storage. High temperature corrosion and economic aspects of these systems are also discussed.

Review on concentrating solar power plants and new developments in high temperature thermal energy storage technologies

The use of solar energy in recent years has reached a remarkable edge. The continuous research for an alternative power source due to the perceived scarcity of fuel fossils is its driving force. It has become even more popular as the cost of fossil fuel continues to rise. The earth receives in just 1 h, more energy from the sun than what we consume in the whole world for 1 year. Its application was proven to be most economical, as most systems in individual uses requires but a few kilowatt of power. This paper reviews the present day solar thermal technologies. Performance analyses of existing designs (study), mathematical simulation (design) and fabrication of innovative designs with suggested improvements (development) have been discussed in this paper.

A review of solar thermal technologies

An ideal air standard cycle analysis of the solar chimney power plant gives the limitingperformance, ideal efﬁciencies and relationships between main variables. The presentpaper includes chimney friction, system, turbine and exit kinetic energy losses in theanalysis. A simple model of the solar collector is used to include the coupling of the massﬂow and temperature rise in the solar collector. The method is used to predict the per-formance and operating range of a large-scale plant. The solar chimney model is veriﬁedby comparing the simulation of a small-scale plant with experimental data.@S0199-6231~00!00503-7#

Solar Chimney cycle analysis with system loss and solar collector performance.

An experimental investigation of the performance of a solar chimney turbine is presented. The design features a single rotor and uses the chimney supports as inlet guide vanes (IGVs) to introduce pre-whirl. This reduces the turbine exit kinetic energy at the diffuser inlet and assists the flow turning in the IGV-to-rotor duct. The rotor configuration allows the supports to be placed directly under the chimney walls. Measurements from a scale model turbine are used to calculate the turbine performance and efficiency. Efficiencies over a wide operating range and detailed performance measurements at two operating points are presented. Total-to-total efficiencies of 85-90% and total-to-static of 77-80% over the design range are measured. The detailed measurements give insight into the turbine performance and possible design improvements. These results allow more accurate simulation of solar chimney power plants.

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Solar Chimney Turbine Performance

Chimneys as tall as 1500 m may be important components of proposed solar chimney power plants. The exit air density will then be appreciably lower than the inlet density The paper presents a one-dimensional compressible flow approach for the calculation of all the thermodynamic variables as dependent on chimney height, wall friction, additional losses, internal drag and area change. The method gives reasonable answers even over a single 1500 m step length used for illustration, but better accuracy is possible with multiple steps. It is also applicable to the rest of the plant where heat transfer and shaft work may be present. It turns out that the pressure drop associated with the vertical acceleration of the air is about three times the pressure drop associated with wall friction. But flaring the chimney by 14 percent to keep the through-flow Mach number constant virtually eliminates the vertical acceleration pressure drop.

Theodor W. von Backström

Papers

Solar Chimney cycle analysis with system loss and solar collector performance.

Solar Chimney Turbine Performance

Compressible Flow Through Solar Power Plant Chimneys

Maximum fluid power condition in solar chimney power plants - An analytical approach

System value and progress of CSP