Exergo-Economic Evaluation of the Cost for Solar Thermal Depuration of Water
Abstract
:1. Introduction
1.1. Pasteurization of Water with Solar Collectors in Recirculation System—Existing Research and Investigated Plant
2. Methodology
2.1. Design and Off-Design Simulation; Energy Analysis of the System
2.1.1. Sizing the Natural Circulation Pasteurisation System
2.1.2. Off-Design Simulation of the System
2.2. Exergy Analysis
- Solar collector exergy destruction—resulting from the exergy balance of solar collector component; as energy transferred to the fluid is conserved, this destruction is essentially a heat transfer irreversibility;
- Piping insulation exergy loss—resulting from standard heat transfer models for thermally insulated pipe lines
- Piping friction exergy destruction—predicted using turbulent flow pipe correlations; entropy calculated from the overall pressure loss
- Regenerative heat exchanger exergy destruction (spill-over)
- Make-up mixing exergy destruction (spill-over)
- Piping insulation exergy loss (spill-over; make-up and discharge pipes)
- Piping friction exergy destruction (spill-over; make-up and discharge pipes)
- Compensation tank unsteady exergy destruction—this results from the model of the compensation tank as a dynamic-effect carrier; the tank is modelled as a fixed volume with variable temperature, internal energy, and closed-system exergy accumulation [18]. The transient exergy destruction rate associated with the compensation tank is a difference between exergy rate of water flowing into the tank and water leaving the tank at given time step and change of internal exergy of the tank during the whole time step.
2.3. Exergo-Economic Analysis
2.4. Tools
3. Results
3.1. Results: Productivity (from Thermo-Fluid Off-Design Analysis)
3.2. Results—Exergy Analysis
3.3. Results–Exergo-Economic Analysis
4. Comparison with PV Driven Reverse Osmosis System
5. Summary and Conclusions
Acknowledgments
Author Contributions
Conflicts of Interest
Abbreviations
PET | Polyethylene terephthalate, common thermoplastic polymer |
PVC | Polyvinyl chloride |
RHE | Regenerative heat exchanger |
SODIS | Solar Water Disinfection |
UV | Ultraviolet |
Symbols
Surface (solar collector or PV module) or cross section (pipe), m2 | |
Cost rate associated with exergy transfer, €/s | |
Cost rate associated with exergy transfer, €/day | |
Collector constant (non-dimensional) | |
Collector constant, W/(m2·K) | |
Collector constant, W/(m2·K2) | |
Cost per unit of exergy, €/J | |
cp | Constant-pressure specific heat, J/(kg·K) |
Specific cost, €/kg | |
Exergy rate, W | |
ExD | Exergy destruction, J |
ExL | Exergy loss, J |
g | Gravitational constant, m/s2 |
G | Overall radiation, W/m2 |
h | Enthalpy, kJ/kg |
ir | Interest rate |
m | Mass, kg |
Mass flow rate, kg/s | |
Mass flow rate, kg/year | |
Mass flow rate, kg/day | |
H | Driving head, m |
k | Pressure constant |
Operation period, year | |
N | Number |
p | Pressure, Pa |
Overall Radiation heat rate, W | |
Useful solar collector heat rate, W | |
s | Entropy, J/(kgK) |
T | Temperature ( average temperature), K |
U | Internal energy, J/kg |
v | Velocity, m/s |
V | Volume, m3 |
Power, W | |
Cost rate associated with capital investment and operating and maintenance costs, €/s | |
Cost rate associated with capital investment and operating and maintenance costs, €/s | |
Cost rate associated with capital investment and operating and maintenance costs, €/day | |
Z | Purchase cost, € |
Vertical distance from ground level, m |
Greek Symbols
Δ | Variation |
η | Efficiency |
ρ | Density, kg/m3 |
τ | System time step (variable), s |
Subscripts
amb | Ambient |
av | Average |
D | Destruction |
Discharge pipe | |
HP | Holding pipe |
i | Time step i |
in | Inlet |
Installation | |
Plant component | |
L | Loss |
MU | Make up (treated water) |
Makeup pipe | |
out | Outlet |
Heat transfer associated | |
rel | Relative (exergy loss or destruction) |
ric | Recirculating |
Solar Collector | |
Supply tank | |
tank | Tank |
Treated water | |
Treated water tank | |
Work transfer associated | |
x | Exergy |
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Mixer | Solar collector | RHE | Tank | Pipes | |
---|---|---|---|---|---|
Relative Exergy Destruction | |||||
Relative Exergy Loss |
System Parameters | |||||
---|---|---|---|---|---|
C0 | 0.78 | C1 | 1.75 W/(m2·K) | C2 | 0.00625 W/(m2·K2) |
Tamb | 30°C | G | 1000 W/m2 | ASC | 2·1.95 m2 |
L/H | 5.3 | H | 1.5 m | DHP | 0.15 m |
Design Sizing Results | |||||
---|---|---|---|---|---|
D | 0.02 m | L | 8 m | 0.0255 kg/s | |
Δp | 360 Pa | k | 552,000 | η | 0.692 |
2.7 kW | AHP | 0.785 cm2 | ΔzHP | 0.147 m |
No | Location | Manila (Philippines) | Aden (Yemen) | Johannesburg (South Africa) | Nairobi (Kenya) | Brindisi (Italy) | Pantelleria (Italy) | Larnaca (Cyprus) |
---|---|---|---|---|---|---|---|---|
1 | Coordinates | 14.52° N 121°E | 12.83° N 45.03° E | 26.13° S 28.23° E | 1.3° S 36.75° E | 40.65° N 17.95° E | 36.82° N 11.97° E | 34.88° N 33.63° E |
2 | Annual solar radiation, MWh/(m2·year) | 1.818 | 2.244 | 2.254 | 1.933 | 1.701 | 2.111 | 1.702 |
3 | Annual productivity, m3 | 48.792 | 106.354 | 56.819 | 41.961 | 28.342 | 28.347 | 59.525 |
4 | Solar collector: annual exergy destruction, MWh/(m2·year) | 0.869 | 1.121 | 1.084 | 0.931 | 0.787 | 0.910 | 0.799 |
5 | Solar collector: annual exergy loss, MWh/(m2·year) | 0.626 | 0.739 | 0.777 | 0.677 | 0.584 | 0.642 | 0.617 |
6 | Water production cost—Natural circulation, €/m3 | 4.64 | 2.24 | 4.19 | 5.20 | 6.80 | 6.77 | 4.01 |
7 | Water production cost—ROPV, €/m3 | 5.34 | 4.02 | 3.81 | 5.13 | 5.96 | 6.87 | 4.83 |
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Dainelli, N.; Manfrida, G.; Petela, K.; Rossi, F. Exergo-Economic Evaluation of the Cost for Solar Thermal Depuration of Water. Energies 2017, 10, 1395. https://doi.org/10.3390/en10091395
Dainelli N, Manfrida G, Petela K, Rossi F. Exergo-Economic Evaluation of the Cost for Solar Thermal Depuration of Water. Energies. 2017; 10(9):1395. https://doi.org/10.3390/en10091395
Chicago/Turabian StyleDainelli, Nicola, Giampaolo Manfrida, Karolina Petela, and Federico Rossi. 2017. "Exergo-Economic Evaluation of the Cost for Solar Thermal Depuration of Water" Energies 10, no. 9: 1395. https://doi.org/10.3390/en10091395