solar absorption cooling

1. Project Phase – I
Review -III
Design and Analysis of Solar Absorption Chiller - Phase
Change Material Integrated Technology (SAPIT) for
cooling telecommunication shelters in India
Undertaken by: Anirudh B Mentored by: Dr.R.Velavan
11MN01 Associate Professor
School of Energy
PG Scholar PSG College of Technology
ME Energy Engineering
School of Energy
PSG College of Technology

2. Transient analysis of telecom shelter using TRNSYS 16
Building simulation wizard

3. Theoretical model of SAC
Thermal energy required by the absorption chiller,
𝑄𝑐
𝑄 𝑐ℎ =
𝐶𝑂𝑃 𝑐ℎ
Where, 𝐶𝑂𝑃 𝑐ℎ is the coefficient of performance of the absorption chiller
which varies with demand is given in a fourth order polynomial for partial
load efficiency of absorption chiller,
4 3 2
𝐶𝑂𝑃 𝑐ℎ = 𝑎𝑓𝑐ℎ + 𝑏𝑓𝑐ℎ + 𝑐𝑓𝑐ℎ + 𝑑𝑓𝑐ℎ + 𝑒
Where, a=-2.0821,b=6.2385,c=-7.2852,d=3.8055,e=0.023
Where, 𝑓𝑐ℎ is the ratio of the cooling load and the chiller nominal capacity
and given by
𝑄𝑐
𝑓𝑐ℎ =
𝐶𝐻 𝑐𝑎𝑝
Courtesy: N. Fumo, V. Bortone, J. C. Zambrano, “Solar Thermal Driven Cooling System for a Data
Center in Albuquerque New Mexico”, Journal of Solar Energy Engineering, ASME(2011)

4. Building simulation wizard- Time vs. Cooling load_W

5. Building simulation wizard- Time vs. Zone temperature

6. Building simulation wizard- Time vs. PLF

7. Building simulation wizard- Time vs. COP

8. Building simulation wizard- Time vs. Required thermal energy

9. PCM properties and specifications
Types Properties Value Application
Phase change temperature 27 – 29 deg C
Operating range 22 – 34 deg C
Density 1550 kg/𝑚3
Latent heat 190 kJ/kg
Maximum operating 80 deg C
temperature
HS 29 Quantity per kWh 20 kg Telecom
HDPE profile size 840X200X20 mm
shelter cooling
Maximum amount of heat to 5000 W
application
be removed
Operating hours of PCM 16 hrs
Quantity of PCM required 1515 kg
No. of panels required 379 panels
Courtesy: Pluss polymers Ltd., www.thermalenergystorage.in

10. Evacuated tube collector- thermal analysis
Solar radiation incident on the tube,
𝐸 𝑖𝑛𝑐𝑖𝑑𝑒𝑛𝑡 = 𝐺𝐴 𝑝𝑜
Where, 𝐺 is the Global horizontal solar radiation on a typical day and
𝐴 𝑝𝑜 is the aperture area of the outer borosilicate tube
Solar radiation transmitted through the tube,
𝐸 𝑡𝑟𝑎𝑛𝑠𝑚𝑖𝑡𝑡𝑒𝑑 = 𝐸 𝑖𝑛𝑐𝑖𝑑𝑒𝑛𝑡 𝜏
Where, 𝜏 = 0.92
Useful heat gained by the collector,
𝐸 𝑢 = 𝐸 𝑡𝑟𝑎𝑛𝑠𝑚𝑖𝑡𝑡𝑒𝑑 𝑁 𝑡
Where, 𝑁 𝑡 is the number of tubes in the collector
Outlet hot water from the collector is given by,
𝐸 𝑢 = 𝑚ℎ,𝑐𝑜𝑙 𝑐ℎ,𝑐𝑜𝑙 (𝑇ℎ,𝑐𝑜𝑙 − 𝑇 𝑎𝑣𝑔 )
Where, 𝑇 𝑎𝑣𝑔 is the average temperature of the storage tank
Courtesy: Siddharth Arora, Shobhit Chitkara, R. Udayakumar, Muhammad Ali, “Thermal analysis
of evacuated tube solar collectors”, Journal of Petroleum and Gas Engineering, Vol. 2(4), pg: 74-
82, April 2011

11. Transient analysis of SAC model using TRNSYS 16
TRNSYS Simulation Studio

12. Inputs to the Simulation – Evacuated tube solar thermal circuit
Parameters Value
Number of collectors in series 6
Collector Area 8𝑚2
Transmissivity of the tube 0.92
Absorptivity of the tube 0.04
Outer borosilicate tube diameter 47 mm
Length of the evacuated tube 1500 mm
Intercept efficiency 0.7
Negative Ist order efficiency coefficient 𝑘𝐽
10 ℎ𝑟.𝑚2 𝐾
Negative 2nd order efficiency coefficient 𝑘𝐽
0.03 ℎ𝑟.𝑚2 𝐾
Hot water pump maximum flow rate 200 kg/hr
Maximum power 0.2kW
Inlet mass flow rate 120 kg/hr
Thermal storage tank volume 1.2 𝑚3
Tank loss coefficient 𝑘𝐽
3 ℎ𝑟.𝑚2 𝐾
Temperature levels used in the tank 6

13. Inputs to the Simulation – Chiller hot water
circuit components
Parameters Value
Chiller rated capacity 4TR (14kW)
Rated COP 0.8
Hot fluid, chilled water fluid, cooling 4.19 kJ/kg.K
water fluid specific heat
Chilled water inlet temperature 15.5 deg C
Chiller water mass flow rate 2173 kg/hr
Cooling water inlet temperature 28 deg C
Cooling water mass flow rate 2613 kg/hr
Hot water inlet temperature 90 deg C
Hot water mass flow rate 3456 kg/hr
Chiller set point temperature 10 degC
Auxiliary heater maximum capacity 0.5 kW
Overall loss coefficient 𝑘𝐽
10
ℎ𝑟.𝑚2 𝐾
Efficiency 0.8
Set point temperature 90 deg C

14. Inputs to the Simulation – Chiller cooling
water circuit components
Parameters Value
Cooling tower rated capacity 5TR (17.5kW)
Fan power at maximum capacity 0.5 kW
Sump volume 1 𝑚3
Initial sump temperature 26 deg C
Sump make up temperature 26 deg C
Wet bulb temperature 25 deg C
Dry bulb temperature 28 deg C
Rated flow rate for variable speed pump 700 kg/hr
Rated power 0.5 kW
Power coefficient 1
Pump efficiency 0.6
Motor efficiency 0.9

15. TRNSYS simulation studio – Time vs. Total horizontal global
radiation

16. TRNSYS simulation studio – Time vs. Total global radiation on the
collector surface

17. TRNSYS simulation studio – Time vs. global radiation on collector
surface on a typical day of January month

18. TRNSYS simulation studio – Time vs. global radiation on collector
surface on a typical day of April month

19. TRNSYS simulation studio – Time vs. global radiation on collector
surface on a typical day of July month

20. TRNSYS simulation studio – Time vs. global radiation on collector
surface on a typical day of December month

21. TRNSYS simulation studio – Time vs. Hot water inlet to the
collector and tank average temperature

22. TRNSYS simulation studio – Time vs. Hot water outlet
temperature from the collector

23. TRNSYS simulation studio – Time vs. Hot water outlet
temperature from the chiller

24. Economic Analysis – Equipment and utility cost
Parameters Value
Conventional air-conditioner 30000 Rs./TR
Auxiliary heater 3000 Rs./kW
DG set cost (20kVA) 2,15,000 Rs.
Hot water fired absorption chiller 50000 Rs./TR
(inclusive of cooling tower)
Evacuated tube solar collector 12000 Rs./𝑚2
PCM cost 50 Rs./kg
Thermal storage tank 7500 Rs./𝑚3
Electricity rate 7.5 Rs./kWh
Diesel rate 50 Rs./ltr

25. Economic Analysis – Annual energy and cost savings
Parameters Value
Operating hours per day (air – conditioner) 24hrs
Electrical energy consumed by a telecom shelter 5 kW
Percentage of energy consumed by AC from both grid and DG set 60%
Electricity consumed by the air-conditioner of capacity (2.5 TR min) 26,280 kWh
Electricity cost per year Rs. 98,550
DG set operating hours per day 12hrs
Diesel cost per year Rs. 2,62,800
Total cost per year Rs. 6,15,350
SAC investment and operational cost (inclusive of PCM cost) Rs. 4,60,537
Operational hours of the AH per day 10hrs
Electricity consumed by AH per year 1460 kWh
Total energy savings 24,820 kWh
Total cost savings Rs.1,54,812
Payback period 9 months

26. Environmental Benefits
Parameters Value
Carbon Emission factor of lignite coal 101.2 kg/TJ
Carbon Emission factor of diesel 74.1 kg/TJ
Diesel consumption per hour 2 ltr
Calorific value of Lignite coal 15000 kJ/kg
Calorific value of diesel 45000 kJ/kg
Energy supplied by lignite coal 0.147825 TJ
Energy supplied by diesel 0.1963116 TJ
𝐶𝑂2 emission by coal 14.95 tons
𝐶𝑂2 emission by diesel 14.54 tons
Total 𝐶𝑂2 emissions per year 29.506 tons
𝐶𝑂2 emission by AH per year 2.07 tons
Total 𝐶𝑂2 mitigated per annum 27.42 tons

27. Conclusion
Solar driven absorption chiller has been designed and analyzed for part
load condition using TRNSYS 16
The cooling load profile for a typical telecom shelter has been generated
for a year and has been used for further analysis
Simulation results showed that to achieve a solar thermal efficiency of
65%, the mass flow rate was to be maintained at 120kg/hr in a total
collector area of 8𝑚2
The hot fluid temperature at the outlet of each collector must be
maintained between 90 deg C to 130 deg C to achieve the average
temperature of the tank between 75 deg C to 85 deg C and in order to
maintain the COP of the chiller between 0.68 to 0.76
The chilled water and cooling water temperature difference was found to
be around 5 deg C and 4 deg C respectively
The economic analysis shows that the total energy savings potential per
year as 24,820kWh and the total cost savings potential as Rs.1,54,812
The environmental analysis shows us there is a potential of mitigating 27.8
tons of CO2 per annum if the SAPIT cooling system replaces the
conventional cooling system