0
Research Papers

Thermodynamic Cycles for a Small Particle Heat Exchange Receiver Used in Concentrating Solar Power Plants

[+] Author and Article Information
Kyle Kitzmiller

Department of Mechanical Engineering,  San Diego State University, San Diego, CA 92182

Fletcher Miller

Combustion and Solar Energy Laboratory, Department of Mechanical Engineering,  San Diego State University, San Diego, CA 92182 e-mail: Fletcher.Miller@sdsu.edu

Although carbon is indeed oxidized in this receiver, we will show that the carbon consumption is 2-5% of that of a standard gas turbine producing the same power.

The value 0.05 is arbitrarily given, and represents the authors’ opinion of a “green” technology. For practical implementation, this value will also be a function of local laws and fuel costs.

J. Sol. Energy Eng 133(3), 031014 (Jul 28, 2011) (8 pages) doi:10.1115/1.4004270 History: Received February 10, 2011; Revised May 11, 2011; Published July 28, 2011; Online July 28, 2011

Gas-cooled solar receivers for concentrating solar power plants are capable of providing high temperature, pressurized gas for electrical power generation via a Brayton cycle. This can be accomplished by expanding hot, pressurized gas directly through a turbine, or through using a heat exchanger to indirectly heat pressurized air. Gas-cooled receivers can be divided into two basic technologies. In tube based solar receivers, thermal energy is transferred to air through convection with the heated tube wall. This limits receiver efficiency since the tube wall needs to be substantially hotter than the gas inside due to the relatively poor gas heat transfer coefficient. In volumetric receivers, solar energy is absorbed within a volume, rather than on a surface. The absorption volume can be filled with ceramic foam, wires, or particles to act as the absorbing medium. In a small particle heat exchange receiver, for example, submicron sized particles absorb solar radiation and transfer this energy as heat to a surrounding fluid. This effectively eliminates any thermal resistance, allowing for higher receiver efficiencies. However, mechanical considerations limit the size of volumetric, pressurized gas-cooled receivers.

In order to solve this problem, several thermodynamic cycles have been investigated, each of which is motivated by key physical considerations in volumetric receivers. The cyclic efficiencies are determined by a new MATLAB code based on previous Brayton cycle modeling conducted by Sandia National Laboratories. The modeling accounts for pressure drops and temperature losses in various components, and parameters such as the turbine inlet temperature and pressure ratio are easily modified to run parametric cases.

The performance of a gas-cooled solar receiver is largely a function of its ability to provide process gas at a consistent temperature or pressure, regardless of variations in solar flux, which can vary due to cloud transients or apparent sun motion throughout the day. Consistent output can be ensured by combusting fuel within the cycle, effectively making a solar/fossil fuel hybrid system. Several schemes for hybridization with natural gas are considered here, including externally fired concepts and combined receiver/combustor units. Because the efficiency of hybridized cycles is a function of the solar thermal input, the part load behavior of the recuperated cycle is examined. However, off-design models are simplistic in this research, as the goal of the work is an introductory evaluation of different potential cycles.

Copyright © 2011 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

Schematic of a small particle heat exchange receiver.

Grahic Jump Location
Figure 2

Efficiency versus turbine inlet temperature for a simple-cycle gas turbine engine. Compressor pressure ratio is shown along the curve.

Grahic Jump Location
Figure 3

Recuperated gas turbine cycle with solar receiver and combustor. Note the combustor bypass used if the air exiting the solar receiver is too hot.

Grahic Jump Location
Figure 4

Recuperated cycle thermal efficiency versus pressure ratio for various turbine inlet temperatures and two values of recuperator effectiveness.

Grahic Jump Location
Figure 5

Gas temperature at various stages in the recuperated cycle for five levels of solar thermal input. Legend: R = receiver, C = combustor.

Grahic Jump Location
Figure 6

Efficiency as a function of solar input with different firing methods. Legend: R = receiver, C = combustor.

Grahic Jump Location
Figure 7

Receiver depth needed to absorb 95% of the light before it strikes the wall for various pressure ratios and fuel consumption ratios (see Eqs. 2,3).

Grahic Jump Location
Figure 8

Cycle with a nonpressurized receiver and external combustor.

Grahic Jump Location
Figure 9

Thermal efficiency of the cycle incorporating a nonpressurized receiver versus compressor pressure ratio. Shown for various turbine inlet temperatures (○ = 800 °C, □ = 900 °C, × = 1000 °C, ⋄ = 1100 °C).

Grahic Jump Location
Figure 10

Efficiency of a cycle with an atmospheric-pressure receiver as a function of solar input with different firing methods. Legend: R = receiver, C = combustor.

Grahic Jump Location
Figure 11

Receiver depth needed to absorb 95% of the light before it strikes the wall in an atmospheric-pressure receiver for various pressure ratios and fuel consumption ratios.

Grahic Jump Location
Figure 12

Gas temperature at various stages in the nonpressurized receiver cycle for four levels of solar input. Legend: R = receiver, C = combustor.

Grahic Jump Location
Figure 13

Cycle with an external combustor and pressurized receiver.

Grahic Jump Location
Figure 14

Gas temperature at various stages in the pressurized receiver with external combustor for four levels of solar thermal input.

Grahic Jump Location
Figure 15

Semiclosed-loop receiver cycle.

Grahic Jump Location
Figure 16

Semiclosed-loop cycle efficiency versus turbine inlet temperature for various pressure ratios.

Grahic Jump Location
Figure 17

Semiclosed-loop cycle efficiency versus turbine inlet temperature for various pressure ratios.

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In