Transcript Thermally-driven desalination systems

Solar powered adsorption cooling cum
desalination
Professor Kim Choon NG,
Mechanical Engineering,
National University of Singapore,
and
Visiting Professor
Water Desalination and Reuse
Centre, KAUST, SA
Email: [email protected]
Adsorption-triggered-evaporation
28-36°C
12-33°C
7-28°C
Cooling power, Tchilled = 720°C, 25- 32 Rtons/tonne
25-33°C
Desorption-activated-condensation
45-75°C
28-33°C
25-30°C
Mesoporous
adsorbent
SiO3.nH2 O , Potable water TDS
800m2/g <10ppm, pH =7.3,±0.1
5 to 12 m3/tonne.day
55-85°C, from Solar
or waste heat
Advantages:
-Produce two useful effects with low-temperature heat input,
-low specific energy (electric) consumption (1.38kWh/m3),
-no major moving part, inexpensive materials for construction
•
The daily average radiation in Thuwal (KAUST) is about 22
MJ/m2.day (latitude λ=22o , sunshine hours from 9 to 13
h/day)
•
Estimated thermal rating is 1300 kWh/m 2.year, as compared
with 925 kWh/m 2.year @ 65o C in Singapore .
•
Recommend to use tube collectors because (i) it is easy to
handle, (ii) it reduces the dust accumulation – dust particles
will slide over the tube curvature whilst those accumulated
on top could be blown over by strong wind.
Provide shading that
reduces heat stress in
green houses.
5
Why Co-Generation ?
Conventional
approach
Primary fuel
Electricity from
grid (th  0.42 )
diesel
“Kettle” Boiler
(8 bar)
electricity
Electricallyoperated
decicant
dehumidifier
DARI’s energy
needs
Electricity (- max at
1.3 MW)
Co-generation cum solar
Primary fuel, (Town gas)
Gas Turbines x 2
units of 700 kW
375 to 500oC
Steam (4800 kg/h)
• Cooling
(7o C and 15-18
0C)
• Water
(5 l/m2 .day)
Waste
heat
operated
boiler (8
bar)
Steam
driven
AB/AD
chillers
Temperature
cascaded
utilization of
exhaust energy
with AB_AD
chillers
125o C
Conventional
EUF=0.52
TriGen EUF =0.85
- Thermally-driven design
Exhaust Gas
Grid of
KAUST
Electric
chillers (400
Rtons)
CWS =7 C
500-600 kW for
use in DARI
360 kW
1000 to 1200 kW
50-60 kW
Gas Turbines
(2x 700 kW)
Steam
(177 C, 8.3
bar)
Further waste
heat recovery
40 – 55 kW
Exhaust leaving
at < 125 C
AB chillers (COP
0.9 to 1.1) giving
800 to 1000 Rtons
CWS = 9-10 C
20 to 25 kW
AD Chillers (COP
=0.5 to 0.65)
giving 120 to 150
Rtons
CWS = 14 to 18 C
Water production
75 m /day
Seawater Cooling
Towers (1200
Rtons)
7
Sea water feeding line
Sea Water Tank
Pre-treatment sea water tank
8
Release Valve
Condenser
Collection tank
Condensate drainage
Reactor Bed
9
Condenser
Cooling water system
and evaporator
valves
11
Sea water
Silo-type adsorber-desorber beds
E x haust
gas
2 0 0 to 25 0 C
Post treatme
nt
tank
Hot water
storage
Pretreatment
tank
Fresh water
storage
Waste heat recovery
from exhaust
Can the AD cycle scale to a commercial size ?
– to work closely with industry partners of KAUST
4
Condenser
2
3
5
H
Reaction
bed tower
Purified
water
storage tank
Reaction
bed tower
Evaporator
1
d
d
12
14
15