Abstract
This chapter describes the modelling of a parabolic-trough (PT) concentrating solar power (CSP) plant that produces electricity. To do this, the modelling of the solar field itself is explained first and then the power cycle, consisting of a reheat Rankine cycle, with steam as the working fluid. This power cycle will be used subsequently to be coupled to a desalination plant, creating what is known as a dual-purpose solar power/water cogeneration plant.
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Abbreviations
- A abs :
-
Absorber tube area (m2)
- A c :
-
Aperture area of the collector’s reflective surface (m2)
- A T :
-
Total collector area required for the solar field (m2)
- C p :
-
Specific heat (kJ/kg °C)
- DCA:
-
Drain cooler approach (°C)
- d i :
-
Inlet diameter of the absorber tube (m)
- DNI:
-
Direct normal irradiance (W/m2)
- d o :
-
Outlet diameter of the metallic tube (m)
- E th :
-
Thermal energy required by the process (kWh)
- E th,stored :
-
Stored thermal energy (kWh)
- E th,row :
-
Thermal energy supplying a collector row (kWh)
- F cond :
-
Refrigeration water flow rate in the power plant condenser (m3/h)
- F e :
-
Collector foiling factor
- F w :
-
Specific fresh or seawater flow rate (m3/MWeh)
- GOR:
-
Gain output ratio
- h :
-
Specific enthalpy of the steam and liquid in the power cycle (kJ/kg)
- h f :
-
Specific enthalpy of the steam in its final state in the thermodynamic cycle (kJ/kg)
- h i :
-
Specific enthalpy of the steam in its initial state in the power cycle (kJ/kg)
- h in :
-
Specific enthalpy of the working fluid at the collector inlet (kJ/kg)
- h out :
-
Specific enthalpy of the working fluid at the collector outlet (kJ/kg)
- K :
-
Incidence angle modifier
- L :
-
Absorber tube length (m)
- ṁ :
-
Mass flow rate of the steam and liquid in the power cycle (kg/s)
- ṁ fluid :
-
Mass flow rate of the oil inside the collector (kg/s)
- \( \widehat{n} \) :
-
Normal aperture vector plane in a parabolic-trough collector
- N C :
-
Number of collectors
- N F :
-
Number of rows
- N T :
-
Total number of collectors in the solar field
- P :
-
Steam and water pressure in the power cycle (bar or kPa)
- \( {P}_{\mathrm{c}} \) :
-
Thermal power dissipated in the condenser (kWth)
- P dry :
-
Power consumption required for the air condensers (kWe)
- P cond :
-
Power consumption by the pump that draws water from the sea to the power cycle condenser (kWe)
- P i,pump1 :
-
Ideal power required by pump 1 (kWe)
- P i,pump2 :
-
Ideal power required by pump 2 (kWe)
- P net :
-
Net electrical power generated in the power cycle (kWe)
- \( {P}_{\mathrm{r}} \) :
-
Thermal power required in the reheater (kWth)
- P r,pump1 :
-
Actual power required by pump 1 (kWe)
- P r,pump2 :
-
Actual power required by pump 2 (kWe)
- P pumps :
-
Total power consumed by the two pumps in the power cycle (kWe)
- P turb :
-
Total power generated by the two turbines in the power cycle (kWe)
- P turb,ST1 :
-
Power generated by turbine ST1 (kWe)
- P turb,ST2 :
-
Power generated by turbine ST2 (kWe)
- P Q,collector→environment :
-
Thermal PTC losses (Wth)
- P Q,collector→fluid :
-
Useful thermal power supplied by a collector (Wth)
- P spec, dry :
-
Specific power consumed by the air condensers (kW/MWnominal)
- P Q,sun→collector :
-
Available solar radiation on the collectors' aperture plane (Wth)
- \( {P}_{\mathrm{PCS}} \) :
-
Thermal power required in the power conversion system (kWth)
- P w :
-
Specific power consumed by the water pump that circulates water through the power cycle condenser (kWh/m3)
- P th,field :
-
Thermal power supplied by the solar field (kWth)
- P th, row :
-
Thermal power supplied by a row (kWth)
- P th :
-
Thermal power required by the process (kWth)
- q e :
-
Heat transfer per unit of mass of the oil in the power cycle (kJ/kg)
- q s :
-
Heat transfer per unit of mass of the steam in the power cycle (kJ/kg)
- Re :
-
Reynolds number
- s :
-
Entropy (kJ/kg °C)
- \( \widehat{s} \) :
-
Solar vector
- \( {\widehat{s}}_{E-Z} \) :
-
Projection of the solar vector onto the E–Z plane
- \( {\widehat{s}}_{\mathrm{N}-\mathrm{Z}} \) :
-
Projection of the solar vector onto the N–Z plane
- S :
-
Useful pass section of the metallic absorber tube (m2)
- S E :
-
East coordinate of the solar vector
- SM:
-
Solar multiple
- S N :
-
North coordinate of the solar vector
- S Z :
-
Z coordinate of the solar vector
- t storage :
-
Period for which the system can operate with the thermal energy stored in the storage tank (h)
- t int :
-
Time intervals into which the design day is divided (h)
- t op :
-
Period of process operation using thermal energy supplied by the collector field (h)
- T :
-
Steam and liquid temperature in the power cycle (°C)
- T abs :
-
Average temperature of the metallic absorber tube (°C)
- T amb :
-
Ambient temperature (°C)
- T i :
-
Oil temperature at the collector inlet (°C)
- T o :
-
Oil temperature at the collector outlet (°C)
- T sat :
-
Temperature of the saturated liquid (°C)
- TTD:
-
Terminal temperature difference (°C)
- U L :
-
Global thermal loss coefficient from the absorber tube to the environment (W/m2 °C)
- v :
-
Specific volume of the liquid through the pumps present in the power cycle (m3/kg)
- V :
-
Oil velocity inside the absorber tube (m/s)
- w e :
-
Work per unit of mass realised by the steam over the power cycle (kJ/kg)
- w s :
-
Work per unit of mass realised by the steam circulating through the cycle (kJ/kg)
- x :
-
Steam quality
- γ c :
-
Average annual usage factor of the thermal storage charge
- γ d :
-
Average annual usage factor of the thermal storage discharge
- γ St :
-
Annual storage losses factor
- δ St :
-
Fraction of energy absorbed by the solar field that is sent to the storage system
- Δh :
-
Specific enthalpy difference of the oil between the collector inlet and outlet (kJ/kg)
- ΔT :
-
Temperature increase demanded by the process (°C)
- ΔT c :
-
Oil temperature difference between the collector inlet and outlet (°C)
- ρ :
-
Fluid density (kg/m3)
- η ST :
-
Isentropic efficiency of the turbine
- η th :
-
Thermal efficiency of the power cycle
- μ :
-
Dynamic viscosity of the fluid (kg/m s)
- π:
-
Pi number
- θ i :
-
Incidence angle (°)
- PTC:
-
Parabolic-trough collector
- FWH:
-
Feedwater heater
- ST1:
-
High-pressure turbine
- ST2:
-
Low-pressure turbine
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Palenzuela, P., Alarcón-Padilla, DC., Zaragoza, G. (2015). Steady-State Modelling of a Parabolic-Trough Concentrating Solar Power Plant. In: Concentrating Solar Power and Desalination Plants. Springer, Cham. https://doi.org/10.1007/978-3-319-20535-9_4
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DOI: https://doi.org/10.1007/978-3-319-20535-9_4
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