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Below we show a TEWI (Total Equivalent Warming Impact) comparison.
TEWI is a statistic which is being quoted on a more regular
basis these days and we thought this information may be of
interest.
TEWI = (GWP x L x n) + (GWP x m [1-a] + (n x E x b
)
leakage
losses + recovery losses + energy
consumption
( direct
global warming potential) + (indirect global
warming potential)
GWP = global warming potential [equivalent
CO2 -related ]
L =
leakage rate per year [Kg] (typical 10% of charge/ year)
n =
system operating time [ years ]
m =
refrigerant charge [Kg]
a =
recycling factor (charge lost during end of life recovery)
E =
energy consumption per year [ Kwh]
b =
CO2 – emissions Kg per Kwh (energy- mix)
(European/UK average CO2 equivalent =
0.6/0.43)
TEWI comparison
NH3 vs. R407c Water cooled water chillers 1,000Kw
TEWI NH3 = (0x{160x10%}x15)+(0x160x{1-0.75})+(15x{1,040X222}x
0.6)
(0 )
(0)
( 2,077,920) = 2,077,920 KgCO2e
TEWI R407c= (1725x{160x10%}x15)+(1725x160x{1-0.75})+(15x{1,040X250}x
0.6)
(414,000 )
(69,000)
( 2,340,000) = 2,823,000 KgCO2e
Compared to Ammonia R407C;
( leakage effects +100%) (recovery
loss +100%) (energy effects
+12.6%)
Overall effect + 36%
Assumptions:
- 15 year life
- Multi screw compressors machines
- DX evaporators
- 2,500 equivalent operating full load hours per annum
- CHW 6 – condenser water 30<35 deg C
- Refrigerant charge
- Energy consumption
- COP NH3/407c = 4.5 /4.0
- CO2 emissions Kg per Kw/Hr (0.6 typical for Europe)
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