23 Nov 2012

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APPENDIX 2: Sample Calculations

2.1: Power Generation Calculation

Power = ∆H*m*efficiency

ie: Power Generated in Turbine 1 = (Hstream 4 – Hstream 6)*mstream 4*efficiency

= (2947.4 kJ/kg – 2548.8 kJ/kg)*(8.9 kg/s)*0.72 = 2554.23 kJ/s = 2.554 MW

This method of calculating power was used for all power calculations that involved

turbines, as turbine power generation is simply the product of the mass flowrate and the

change in enthalpy between the inlet and outlet streams. This product is then multiplied

by the efficiency of the turbine to give the actual power generated.

2.2: Power Loss Due to Efficiency Calculation

ie: Power Lost in Turbine 1 = (Hstream 4 – Hstream 6)*mstream 4*(1 – efficiency)

= (2947.4 kJ/kg – 2548.8 kJ/kg)*(8.9 kg/s)*(1-0.72) = 993.3112 kJ/s = 0.993 MW

This calculation is very similar to that in 2.2, the difference being that losses are being

calculated, so instead of multiplying the ideal power generation by the efficiency, it is

multiplied by 1 – efficiency. This gives the difference between the actual and ideal power

generated: the losses.

2.3: Power Balance Calculation

Power In = Power Out

Power In

MW

Power Out

MW

Boiler

83.25668

Power Produced in Two Turbines

6.3825104

Inlet Water

0.04656

Pipe Losses

8.553

Pump

0.051666667

Condensor Losses

54.165

Hospital Usage

0.25

Boiler Losses

12.488

Turbine Losses

1.5153496

Pump Losses

0.0060528

ie: 83.25668 + 0.04656 + 0.051666667 = 6.3825104 + 8.553 + 54.165 + 0.250+ 12.488 +

1.5153496 + 0.0060528

This power balance was used to check to make sure that all of the power generated and

consumed in the system balanced out. In reality, there are inherent errors in all

calculations, so this balance was off by 0.05 MW, which we deemed to be a very low

amount of error due to the total power generation being over 83 MW.