Undertaken by: Anirudh B

11MN01

PG Scholar

ME Energy Engineering

School of Energy PSG College of Technology

Mentored by: Dr.R.Velavan

Associate Professor

School of Energy

PSG College of Technology

Design and Analysis of Solar Absorption Chiller - Phase

Change Material Integrated Technology (SAPIT) for

cooling telecommunication shelters in India

Project Phase – I

Review -III

Transient analysis of telecom shelter using TRNSYS 16

Building simulation wizard

Theoretical model of SAC Thermal energy required by the absorption chiller,

𝑄𝑐ℎ =𝑄𝑐

𝐶𝑂𝑃𝑐ℎ

Where, 𝐶𝑂𝑃𝑐ℎ 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,

𝐶𝑂𝑃𝑐ℎ = 𝑎𝑓𝑐ℎ4 + 𝑏𝑓𝑐ℎ

3 + 𝑐𝑓𝑐ℎ2 + 𝑑𝑓𝑐ℎ + 𝑒

Where, a=-2.0821,b=6.2385,c=-7.2852,d=3.8055,e=0.023

Where, 𝑓𝑐ℎis the ratio of the cooling load and the chiller nominal capacity

and given by

𝑓𝑐ℎ =𝑄𝑐

𝐶𝐻𝑐𝑎𝑝

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)

Building simulation wizard- Time vs. Cooling load_W

Building simulation wizard- Time vs. Zone temperature

Building simulation wizard- Time vs. PLF

Building simulation wizard- Time vs. COP

Building simulation wizard- Time vs. Required thermal energy

PCM properties and specifications Types Properties Value Application

HS 29

Phase change temperature 27 – 29 deg C

Telecom

shelter cooling

application

Operating range 22 – 34 deg C

Density 1550 kg/𝑚3

Latent heat 190 kJ/kg

Maximum operating

temperature

80 deg C

Quantity per kWh 20 kg

HDPE profile size 840X200X20 mm

Maximum amount of heat to

be removed

5000 W

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

Evacuated tube collector- thermal analysis Solar radiation incident on the tube,

𝐸𝑖𝑛𝑐𝑖𝑑𝑒𝑛𝑡 = 𝐺𝐴𝑝𝑜

Where, 𝐺 is the Global horizontal solar radiation on a typical day and 𝐴𝑝𝑜 is the aperture area of the outer borosilicate tube

Solar radiation transmitted through the tube,

𝐸 𝑡𝑟𝑎𝑛𝑠𝑚𝑖𝑡𝑡𝑒𝑑 = 𝐸 𝑖𝑛𝑐𝑖𝑑𝑒𝑛𝑡𝜏

Where, 𝜏 = 0.92

Useful heat gained by the collector,

𝐸 𝑢 = 𝐸 𝑡𝑟𝑎𝑛𝑠𝑚𝑖𝑡𝑡𝑒𝑑𝑁𝑡

Where, 𝑁𝑡 is the number of tubes in the collector

Outlet hot water from the collector is given by,

𝐸 𝑢 = 𝑚 ℎ,𝑐𝑜𝑙𝑐ℎ,𝑐𝑜𝑙(𝑇ℎ,𝑐𝑜𝑙 − 𝑇𝑎𝑣𝑔)

Where, 𝑇𝑎𝑣𝑔 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

Transient analysis of SAC model using TRNSYS 16

TRNSYS Simulation Studio

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 10 𝑘𝐽

ℎ𝑟.𝑚2𝐾

Negative 2nd order efficiency coefficient 0.03 𝑘𝐽

ℎ𝑟.𝑚2𝐾

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 3 𝑘𝐽

ℎ𝑟.𝑚2𝐾

Temperature levels used in the tank 6

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

water fluid specific heat

4.19 kJ/kg.K

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 10 𝑘𝐽

ℎ𝑟.𝑚2𝐾

Efficiency 0.8

Set point temperature 90 deg C

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

TRNSYS simulation studio – Time vs. Total horizontal global

radiation

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

collector surface

TRNSYS simulation studio – Time vs. global radiation on collector

surface on a typical day of January month

TRNSYS simulation studio – Time vs. global radiation on collector

surface on a typical day of April month

TRNSYS simulation studio – Time vs. global radiation on collector

surface on a typical day of July month

TRNSYS simulation studio – Time vs. global radiation on collector

surface on a typical day of December month

TRNSYS simulation studio – Time vs. Hot water inlet to the

collector and tank average temperature

TRNSYS simulation studio – Time vs. Hot water outlet

temperature from the collector

TRNSYS simulation studio – Time vs. Hot water outlet

temperature from the chiller

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

(inclusive of cooling tower)

50000 Rs./TR

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

Maintenance cost 50000 Rs./year

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

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 𝐶𝑂2emissions per year 29.506 tons

𝐶𝑂2emission by AH per year 2.07 tons

Total 𝐶𝑂2mitigated per annum 27.42 tons

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