EXCEL Process Simulation
Hybrid Collector/
Bottoming Cycle
by Greenwood
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EXCEL Process SimulationHybrid Collector/Bottoming Cycleby Greenwood |
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Vision
PV film could be build in vacuum space of pair glass. PV film side is cooled by hot water. Thus you can make hybrid collector.
Using hot water as heat source and using air or sea water or cooling tower water as heat sink you can build bottoming cycle.
The purpose of this study is to investigate viability of such system. Mass production type size was selected as the basis of the study.
Design of Hybrid Collector
Max solar radiation: IEC60904-1 AM1.5：Q/A=1kw/m2
Cover glass transparency hc=0.8
Efficiency of PV=7%、Window Area: A=5mx8m=40m2, Max Power Output from PV: W=40x0.07=2.8kW
Radiation of PV at surface temp. of tp Stefan-Botzmann's equation
E=4.88((tp+273)/100)4 (kcal/m2h) or E=5.68((tp+273)/100)4 (W/m2)
Emissivity of PV: e=0.05
Overall heat transfer coefficient from PV to water through substrate: U=50kcal/m2 h C=58.2W/m2 C
Thermal conductivity of styrene form insulation （l=0.02m）: k/l=0.084W/m2 C
Ambient temperature: ta=30oC、Specific heat of water: Cp=0.997kcal/kg C
Neglecting heat loss through edge of the plate and micro spacer.
| unit | Air Cooled Ammonia Water | ASW Cooled Ammonia Water | Cooling Tower Water Cooled Pentane | |
| PV temp. at inlet: tp1 | oC | 100 | 90.35 | 100 |
| PV temp. at outlet: tp2 | oC | 100 | 100 | 100 |
| Solar radiation to PV surface: Qp | kW | 32 | 32 | 32 |
| PV output | kW | 2.8 | 2.8 | 2.8 |
| Radiation loss at inlet: Qpu1 | kW | 2.2 | 1.98 | 2.2 |
| Radiation loss at outlet: Qpu2 | kW | 2.2 | 2.2 | 2.2 |
| Heat Transfer fromPV to water: Qpw | kW | 27.0 | 27.11 | 27.0 |
| Heat loss from insulation: Qi | kW | 0.167 | 1.44 | 0.167 |
| Heat collected: Qw | kW | 26.84 | 26.97 | 26.84 |
| Water circulation rate: G | kg/h | 694.9 | 538.9 | 6,879 |
| Water inlet temp.: t1 | oC | 64.7 | 54.86 | 86.6 |
| Water outlet temp.: t2 | oC | 98 | 98 | 90 |
0.859845kcal/h=1W
Overall Efficiency
Case-１：Hybrid Collector/Air Cooled Ammonia-Water Cycle
Hot Water temperature: 98-64.7oC
Air Temperature: 30oC
TH Diagram
Case-2: Hybrid Collector/Sea water Cooled Ammonia-Water Cycle
Hot Water temperature: 98-54.86oC
Sea water temperature from the depth of 100m: 20oC
TH Diagram
Case-3: Hybrid Collector/Air Cooled Uehara Cycle
Hot Water temperature: 98.0-64.68oC
Air Temperature: 30oC
TH Diagram
Case-4: Hybrid Collector/Cooling Tower Cooled Pentane Cycle
Hot Water temperature: 90-86.6oC
Cooling tower water temperature: 32oC
Wet bulb temperature: 27oC
Dry bulb temperature: 30oC
TH Diagram
Case-5: Hybrid Collector/Cooling Tower Water Cooling Stirling Cycle
Hot Water temperature: 150-140oC
Cooling tower water temperature: 32-33.7oC
Free piston type Stirling engine now in market only produce power above hot temperature over 150oC. Therefore, PV hybrid collector gives no chance for Stirling cycle.
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Case |
Site |
Bottoming Cycle |
Hot Water Temp. |
PV Output | Bottoming Cycle Output | Total | Eff. | Max Press. | Water |
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oC |
kW | kW | kW | % | atm | liter/h | |||
| 1 | Roof top | Ammonia-Water | 98-64.7 | 2.8 | 1.80 | 4.60 | 11.5 | 32.6 | 0 |
| 2 | Sea | Ammonia-Water | 98-54.86 | 2.8 | 2.77 | 5.57 | 13.9 | 35.1 | 2,306 |
| 3 | Roof top | Uehara Cycle | 98.0-64.68 | 2.8 | 1.84 | 4.64 | 11.6 | 35.0 | 0 |
| 4 | Roof top | Pentane Cycle | 90-86.6 | 2.8 | 2.25 | 5.05 | 12.6 | 4.44 | 34.2 |
| 5 | Roof top | Stirling cycle | 150-140 | 2.8 | 0 | 2.8 | 7 | - | - |
Summary
February 8, 2010