170
Md. A. Islam and B. B. Saha
Since the solar cooling system has low electricity consumption, indirect emission
is also lower for all three applications. However, the dimension and weight of the
solar cooling system are much higher than the conventional system. Hence, indirect
emission for raw materials is higher for the adsorption cooling system. Additionally,
direct emission for the solar cooling system is zero because of deploying natural
refrigerants as working fluid.
Total equivalent warming impact is much higher for conventional cooling systems,
as shown in Fig. 9.6. Lower evaporation temperature causes higher TEWI.
9.5 Conclusions
In this assessment, performance and environmental impact of conventional and solar
cooling system have been evaluated and compared. Three different applications:
room air-conditioning (T eva at 12 °C), medium temperature application (T eva at −
7 °C) and low-temperature applications (T eva at −25 °C) have been considered for
both the systems. R32, R134a and R404A have been selected as working fluid for
the conventional system. Whereas, silica gel/water, activated carbon/methanol and
activated carbon/ammonia pairs have been considered for the solar cooling system.
A constant cooling load of 10 kW is considered for all the applications. The results
indicate that COP of the conventional cooling system is higher than thermal COP
of the solar cooling system. However, electrical COP of the solar cooling system is
considerably high due to the thermal input for desorption (thermal compression).
Indirect emission for electricity consumption is definitely higher for the conventional cooling system. It happens due to the huge electricity consumption by the
mechanical vapour compressor. However, the weight of the used raw materials is very
high that build the solar cooling system. Hence, annual indirect warming impact to
build the system is relatively higher for the solar cooling system. In the case of direct
emission, the solar cooling system is better because it uses natural refrigerants, and
the GWP of those refrigerants are zero. Currently deployed refrigerants (R32, R134a,
R404A, etc.) in conventional systems have high GWP, and hence, the direct warming
impact is higher. However, the situation might change if low GWP refrigerants are
introduced in conventional systems.
Currently, TEWI (summation of indirect and direct emissions) is very high for
conventional cooling systems. Therefore, now is the appropriate time to switch from
conventional systems to solar cooling technology.
Appendix 1
The Sensitivity of TEWI with a Refrigerant Leakage Rate
The refrigerant leakage rate of a conventional cooling system could vary for several
reasons such as evaporation and condensation temperature, selected refrigerant and
Md. A. Islam and B. B. Saha
Since the solar cooling system has low electricity consumption, indirect emission
is also lower for all three applications. However, the dimension and weight of the
solar cooling system are much higher than the conventional system. Hence, indirect
emission for raw materials is higher for the adsorption cooling system. Additionally,
direct emission for the solar cooling system is zero because of deploying natural
refrigerants as working fluid.
Total equivalent warming impact is much higher for conventional cooling systems,
as shown in Fig. 9.6. Lower evaporation temperature causes higher TEWI.
9.5 Conclusions
In this assessment, performance and environmental impact of conventional and solar
cooling system have been evaluated and compared. Three different applications:
room air-conditioning (T eva at 12 °C), medium temperature application (T eva at −
7 °C) and low-temperature applications (T eva at −25 °C) have been considered for
both the systems. R32, R134a and R404A have been selected as working fluid for
the conventional system. Whereas, silica gel/water, activated carbon/methanol and
activated carbon/ammonia pairs have been considered for the solar cooling system.
A constant cooling load of 10 kW is considered for all the applications. The results
indicate that COP of the conventional cooling system is higher than thermal COP
of the solar cooling system. However, electrical COP of the solar cooling system is
considerably high due to the thermal input for desorption (thermal compression).
Indirect emission for electricity consumption is definitely higher for the conventional cooling system. It happens due to the huge electricity consumption by the
mechanical vapour compressor. However, the weight of the used raw materials is very
high that build the solar cooling system. Hence, annual indirect warming impact to
build the system is relatively higher for the solar cooling system. In the case of direct
emission, the solar cooling system is better because it uses natural refrigerants, and
the GWP of those refrigerants are zero. Currently deployed refrigerants (R32, R134a,
R404A, etc.) in conventional systems have high GWP, and hence, the direct warming
impact is higher. However, the situation might change if low GWP refrigerants are
introduced in conventional systems.
Currently, TEWI (summation of indirect and direct emissions) is very high for
conventional cooling systems. Therefore, now is the appropriate time to switch from
conventional systems to solar cooling technology.
Appendix 1
The Sensitivity of TEWI with a Refrigerant Leakage Rate
The refrigerant leakage rate of a conventional cooling system could vary for several
reasons such as evaporation and condensation temperature, selected refrigerant and