Solar Power Plant

We are going to use the solar power plant as our first study case for the analysis of a complete thermal system.  Throughout this class, and the second class as well, we are going to revisit this system over and over again.  The main purpose is to provide you an integrated view of the entire system and to show the connectivity between different disciplines in thermal science.

What is a solar power plant?  Go visit SunLab and other Internet links to learn more about it.

Technology
Solar Trough System

Solar Power Towers

Solar Dish/Engine Systems

Relevant Subjects
Heat Transfer

• General Description-A short definition 
• Radiation
• Convection
• Conduction-links to lecture notes
• Heat Exchanger-CyclePad models thermal cycles by analyzing each component.  This links to CyclePad's definition of a Heat Exchanger.

Fluid Mechanics

• Mass, Momentum & Energy Conservation-to lecture notes
• Turbine
• Pump
• Compressor- definitions & analysis for various thermal devices.
• Turbomachinery- Pictures of flow devices
• Piping system

Thermodynamics

• 1st Law: Energy conservation-energy conservation principle applied to either an open or a closed system 
• 2nd Law: 
  • reversibility- reversible processes,
  • Entropy-A large page explaining the concept of entropy
• Processes
  • Cycles-an overview of several thermodynamic cycles
   
• Properties-A database maintained by NIST that provides thermophysical properties for many fluids

• Other links: TEST, 2nd law, entropy, thermo. resources.

Why solar energy?

Clean, Abundance, renewable & getting cheaper everyday

Explore other renewable energy sources by visiting National Renewable Energy Laboratory and the following other sites

• Wind-This site provides information on wind energy products.
• Geothermal-Information on how to use this resource, as well as proposed projects and laws. 
• Ocean thermal -Information about this as-yet-untapped resource, and potential applications
• Hydropower-Includes facts about hydropower research and systems. 
• Hydrogen-Based Energy - Information about hydrogen, fuel cells infrastructure technology program
• Biomass - Applications in the biomass energy program

Solar Trough System

Trough systems predominate among today’s commercial solar power plants.   Trough systems convert the heat from the sun into electricity. Because of their parabolic shape, troughs can focus the sun at 30 to 60 times its normal intensity on a receiver pipe located along the focal line of the trough. Synthetic oil captures this heat as the oil circulates through the pipe, reaching temperatures as high as 390°C (735ºF). The hot oil is pumped to a generating station and routed through a heat exchanger to produce steam. Finally, electricity is produced in a conventional steam turbine.

Solar Power Towers

These systems produce electricity on a large scale. They are unique among solar technologies because they can store energy efficiently and cost effectively. They can operate whenever the customer needs power, even after dark or during cloudy weather.

Power towers operate by focusing a field of thousands of mirrors onto a receiver located at the top of a centrally located tower. The receiver collects the sun's heat in a heat-transfer fluid, which is used to generate steam for a conventional steam turbine located at the foot of the tower for production of electricity.

Schematic of electricity generation using molten-salt storage:

1. sun heats salt in receiver;
2. salt stored in hot storage tank;
3. hot salt pumped through steam generator;
4. steam drives turbine/generator to produce electricity;
5. salt returns to cold storage tank

Solar Dish/Engine Systems

These systems, with net solar-to-electric conversion efficiencies reaching 30%, can operate as stand-alone units in remote locations or can be linked together in groups to provide utility-scale power 

Solar dish/engine systems convert the energy from the sun into electricity at a very high efficiency. Using a mirror array formed into the shape of a dish, the solar dish focuses the sun’s rays onto a receiver. The receiver transmits the energy to an engine, typically a kinematic Stirling engine (although Brayton-cycle engines are also being considered), that generates electric power.

Because of the high concentration ratios achievable with parabolic dishes and the small size of the receiver, solar dishes are efficient at collecting solar energy at very high temperatures. Tests of prototype systems and components at locations throughout the United States have demonstrated net solar-to-electric conversion efficiencies as high as 30%. This is significantly higher than any other solar technology.

Study Plan for Heat Transfer

(1) Energy conservation, heat diffusion equation.

(2) Conduction: thermal resistance concept, extended surface/fin analysis.

(3) Transient heat transfer: lumped capacitance method, spatial effects, Heisler charts.

(4) Convection: Newton's cooling law, thermal boundary layer concept, Nusselt/Reynolds/Prandtl numbers, Reynolds analogy, empirical correlations for internal and external flows.

(5) Free convection: Grashof/Rayleigh numbers, combined modes.

(6) Radiation: Planck emission, blackbody emission, absorption, transmission & reflection, greenhouse effect, shape factor.

(7) Heat exchanger design.