Wb Jp3 dV Jp4dV144

These calculations are repeated for several strokes, until the difference between p1 and p2 is negligibly small. The resulting boundary work terms of all strokes are added to give a total value, and then the result is divided by the time required for the strokes to occur to obtain the average power output of the system.

Table 14.4 System performance with a 40 C (72 F) temperature difference at 300 psi.

Temperature of heat source (oC/oF)

50/122

Temperature of cold sink (oC/oF)

10/50

48 gallon tank configuration (2 pair)

Overall heat transfer coefficient, U (Btu/h ft2 F)

8.36

Heat transfer rate, Q (Btu/h)*(per tank)

26,304

Operating pressure (psig)

300

Carnot efficiency (%)

12.38

Projected hourly output for 4-tank configuration, each tank having 48 gal.

1.92

(kW h)

Projected daily output for 4-tank configuration, for 10 h/day operation (kW h)

20

Revenue for 10 h operation at $110/MW h ($)

2.20

Annual revenue for 10 h operation/day at $110/MW h ($)

803

432 gallon tank configuration (8 tanks)

Overall heat transfer coefficient, U (Btu/h ft2 F)

8.00

Heat transfer rate, Q (Btu/h)*

208,469

Operating pressure (psig)

300

Carnot efficiency (%)

12.38

Projected hourly output for 8 pair-tank configuration, each tank having 432

30

gal. at 50% efficiency (kW h)

Projected daily output for 8-pair tank configuration, for 10 h/day operation

304

(kW h)

Projected daily output for 8-pair tank configuration, operating 10 h/day high

516

output and 14 h/day low output (kW h)

Projected hourly output for 8-pair tank configuration, for 24 h/day steady op-

729

eration (kW h)

Revenue per day at $110/MW h for 10 h/day high output and 14 h/day low

56.77

output ($)

Revenue per day at $110/MW h for 24 h/day steady operation ($)

80.15

Revenue per annum at $110/MW h for 24 h steady operation ($)

29,253

* The heat transfer rate is evaluated as Q = UAA.T.

* The heat transfer rate is evaluated as Q = UAA.T.

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