Generator - Internal Combustion Engine

Generator:InternalCombustionEngine

Used in:   Hot water loop, supply side DHW loop, supply side

The Internal Combustion (IC) Engine generator uses a modified Otto cycle. This generator model uses the electrical load and rated engine generator size to compute part-load ratios (PLR). Fuel energy input and recoverable jacket and lube oil heat are then computed. Finally, the recoverable exhaust heat is calculated.

Manufacturer’s curves must be obtained for IC engine generators to derive the equipment performance parameters that are specified in the quadratic curve fits. Note that simple transformation of the form of the manufacturer’s curves may be required. Electric energy output/fuel energy input is related to the part-load ratio (i.e., electric/load generator capacity) with a polynomial. Recoverable jacket heat/fuel energy equipment, recoverable lube oil heat/fuel energy input equipment performance, total exhaust heat/fuel energy input equipment, exhaust gas temperature/fuel energy input equipment performance parameters are all specified with a quadratic curve fit.

When the heat recovery curve fits = 0.0, this means that no heat recovery is done on the IC engine generator exhaust gas; and no heat recovery is specified.

General

Name

This alpha field contains the identifying name for the IC engine generator.

Type

Select the type of generator from the list:

• 1-Internal combustion engine - as described on this page.
• 2-Micro turbine

Operation

Availability schedule

Select the schedule that defines the times that the generator can operate.

Note: The way that this Availability schedule interacts with the Plant equipment operation, Scheme schedule for the attached Plant loop, depends on the Electric load centre, Generator operation scheme type setting as follows:

For the 1-Base load scheme type the generator availability schedule overrides the Plant equipment operation scheme schedule, so the generator can run whenever this schedule has a value > 0 regardless of the scheme schedule value.

For the 5-Follow thermal or 6-Follow thermal limit electrical scheme types, both this Availability schedule and the Plant equipment operation scheme schedule must have a value > 0 for the generator to operate.

Power Output

Rated thermal to electric power ratio

This setting allows you to define the ratio of the rated thermal output to the rated electric output. This nominal ratio is only used for control and dispatch decisions and should be generally consistent with the more detailed performance input in the rest of this dialog, but it is not used in the component model. It is only used if the operation scheme is set on the Electric Load centre dialog is set to 5-Follow thermal or 6-Follow thermal limit electrical.

Rated power output

This setting is used to define:

1. The design nominal capacity of the generator (in W or Btu/hr) for the component simulation and,
2. Nominal electric power output to be requested from the generator for supervisory control and generator dispatch for electric load centres. More specifically, it defines how much a generator is loaded (i.e. requested electric power output) and can also impact the operation of an electric storage unit if one is selected on the associated Electric load centre. Search for "Electrical Storage" in the EnergyPlus Engineering Reference for more details on this input and its relationship with electric storage.

Shaft power curve

Select the shaft power quadratic curve which is used to calculate the electric energy output divided by the fuel energy consumption as a function of part-load ratio. The defining equation is:

where RL is the Ratio of load to rated power output.

Fuel

Fuel type

This alpha field determines the type of fuel that the generator uses. The default is 3-Diesel. Valid values are:

• 1-Natural gas,
• 2-Propane gas,
• 3- Diesel,
• 4-Gasoline,
• 5-Fuel oil 1,
• 6-Fuel oil 2,
• 7-Other fuel 1,
• 8-Other fuel 2.

Fuel higher heating value

This numeric field contains the higher heating value of the fuel used (in kJ/kg or Btu/lb).

Part Load Ratios

Minimum part load ratio

This setting contains the minimum allowed operating fraction of full load. The input value must be >= 0.0 and < = 1.0.

Maximum part load ratio

This setting contains the maximum allowed operating fraction of full load. The input value must be >0.0 and < = 1.0.

Optimum part load ratio

This setting contains the optimal operating fraction of full load. This is the part load ratio that gives the optimal production of electric power with the least amount of fuel usage.

Exhaust

Design minimum exhaust temperature

This is the design engine stack saturated steam temperature (in °C or °F).

Maximum exhaust flow per unit of power output

Maximum exhaust flow per unit capacity for the generator. The parameter sets an upper limit on exhaust gas flow and exhaust gas heat recovery for the generator. Units are (kg/s)/W or (lbm/sec)/(Btu/hr).

Total exhaust energy curve

Select the Total exhaust energy quadratic curve which is a quadratic equation used to calculate the total exhaust heat as a function of part-load ratio. The defining equation is:

where RL is the Ratio of load to rated power output.

Exhaust temperature curve

Select the Exhaust temperature quadratic curve which is used to determine the exhaust gas temperature as a function of part-load ratio. The defining equation is:

where RL is the Ratio of load to rated power output.

Exhaust U-Factor Times Area Curve

The UA curve applies to the exhaust gas heat exchanger. The curve is an equation that determines the overall heat transfer coefficient for the exhaust gases with the stack. The heat transfer coefficient ultimately helps determine the exhaust stack temperature. The defining equation is:

The following two fields contain the coefficients for the equation.

Coefficient 1 of U-Factor times area curve

This numeric field contains the first coefficient for the overall heat transfer coefficient curve.

Coefficient 2 of U-Factor times area curve

This numeric field contains the second (exponential) coefficient for the overall heat transfer coefficient curve.

Heat Recovery

Design heat recovery water flow rate

Design water volumetric flow rate through heat recovery loop (in m3/s or gal/min).

Heat recovery maximum temperature

This field sets the maximum temperature (in °C or °F) that this piece of equipment can produce for heat recovery, putting an upper on the recovered heat and limiting the maximum temperatures leaving the component. As temperatures in the loop approach the maximum temperature, the temperature difference between the entering water and the surfaces in the piece of equipment becomes smaller. For the given heat recovery flow rate and that temperature difference the amount of heat recovered will be reduced, and eventually there will be no heat recovered when the entering water temperature is equal to the maximum temperature specified by the user in this field. The reduced amount of heat recovered will diminish if the temperature of the loop approach is the maximum temperature, and this will show up in the reporting. This allows the user to set the availability or the quality of the heat recovered for usage in other parts of the system or to heat domestic hot water supply.

Jacket heat recovery curve

Select the Recovery jacket heat quadratic curve which is a quadratic equation that determines the ratio of recovery jacket heat to fuel energy. It is used to calculate the recoverable jacket heat as a function of part-load ratio. The defining equation is:

where RL is the Ratio of load to rated power output.

Lube heat recovery curve

Select the Recovery lube heat quadratic curve which is a quadratic equation that determines the ratio of recovery lube heat to fuel energy. It is used to calculate the recoverable lube oil heat as a function of part-load ratio. The defining equation is:

where RL is the Ratio of load to rated power output.