Power Cycle |  |  |  |

The power cycle converts thermal energy to electric energy. The power cycle is assumed to consist of a Rankine-cycle steam engine, two open feed-water heaters, and a pre-heater, boiler and super-heater.

The parameters on the Power cycle page describe the steam turbine size and other properties.

Page numbers relevant to this section from the Wagner (2008) and Kistler B (1986) references are:

• | Wagner 83, 86, 114, 164

• | Kistler 224

The power cycle page displays variables that specify the design operating conditions for the steam Rankine cycle used to convert thermal energy to electricity.

Input Variable Reference

Power Block Parameters
Variable | Description | Units
Nameplate Capacity | The power block's full-load, continuous rating under design conditions in kilowatts of electricity, excluding parasitic electric loads. | MWe
Rated Cycle Conversion Efficiency | The Rankine cycle thermal-to-electric conversion efficiency at design conditions. | -
Design Thermal Power | The turbine's design thermal input. It is the thermal energy required at the power block inlet for it to operate at its design point, as defined by the value of the nameplate electric capacity and an estimate of the parasitic losses: Design thermal power = nameplate electric capacity + total parasitic loss estimate. (See Parasitics for a description of the total parasitic loss estimate.) | MWe
Design HTF Inlet Temp | The design temperature in degrees Celsius of the hot heat transfer fluid at the power block inlet. The design values are the operating conditions at which the power block operates at its nameplate capacity. | °C
Design HTF Outlet Temp | The design temperature in degrees Celsius of the cold heat transfer fluid at the power block outlet. The design values are the operating conditions at which the power block operates at its nameplate capacity. | °C
Boiler Steam Pressure | The saturation pressure of the steam as it is converted from liquid to vapor in the boiler or steam generator. Solar Advisor uses this value to determine the steam's saturation temperature and thus the superheating capability of the heat exchangers. | Bar
Min Temp to Load | The lowest heat transfer fluid temperature allowed at the power cycle inlet. Whenever the fluid temperature falls below this point, the power cycle shuts down. | °C
Low-Resource Standby Period | During periods of insufficient flow from the heat source due to low thermal resource, the power block may enter standby mode. In standby mode, the cycle can restart quickly without the startup period required by a cold start. The standby period is the maximum number of hours allowed for standby mode. This option is only available for systems with thermal storage. | hours
Standby Mode Thermal Fraction | The fraction of the turbine's design thermal input required from storage to keep the power cycle in standby mode. This thermal energy is not converted into electric power. | --
Turbine Startup Time | The time in hours that the system consumes energy at the startup fraction before it begins producing electricity. If the startup fraction is zero, the system will operate at the design capacity over the startup time. | hours
Turbine Startup Energy Fraction | The fraction of the turbine's design thermal input required by the system during startup. This thermal energy is not converted to electric power. | --
Ref Condenser Water dT | The temperature difference of the water at the inlet and outlet of the condenser at design conditions. Solar Advisor uses this value to size the condenser. | °C
Temperature Correction Mode | Determines whether Solar Advisor uses the wet bulb or dry bulb temperature data from the weather file as the condenser inlet water temperature. | --
Minimum Load Fraction | The fraction of the nameplate electric capacity below which the power block does not generate electricity. Whenever the power block output is below the minimum load and thermal energy is available from the solar field, the field is defocused. For systems with storage, solar field energy is delivered to storage until storage is full.The default value is 0.15. | --
Max Over Design Operation | The maximum allowable power block output as a fraction of the electric nameplate capacity. Whenever storage is not available and the solar resource exceeds the design value of 950 W/m2, some heliostats in the solar field are defocused to limit the power block output to the maximum load. The default value is 1.1. | --