Solar Water System Conclusions

• Great portions of the total heating and cooling loads are satisfied by solar energy at the optimum conditions and the overall system efficiency is within the previously published results.

• The cost of unit energy for solar heating and cooling systems approximately equals to 68% of the corresponding cost of the conventional fuel at the current prices. This maximum energy is attained with a solar collector area of 38 m2.

• An annual solar savings of about $1900 is achieved at these optimum conditions which confirms the feasibility of solar heating and cooling systems in Kuwait climate.

• The avoided CO2 emission has been found to be equal to 9.7 tonne/year corresponding to a reduction cost of $10.3/tonne.

• The results of this study should encourage wide utilization of solar energy systems which will help in keeping our environment healthy and clean.

Nomenclature

Ac Collector area (m2)

As Storage tank surface area (m2)

cp Specific heat of the water (J/kg K)

Solar energy investment cost which is directly proportional to collector

CC Cost of kW h generated using conventional electricity system ($)

CE Solar energy investment cost which is independent of collector area ($)

Unit cost of delivered conventional energy for the first year of analysis

Chc Cost of kW h generated using solar heating and cooling system ($)

CR Avoided cost or reduction cost ($)

D

Discount rate (%)

Ea

Avoided CO2 emission (tonne CO2)

Ec

CO2 emissions from conventional system (tonne/kW h)

Energy generation cost of the solar heating and cooling system

Eg

($/kW h)

Ehc

CO2 emissions from solar heating and cooling system (tonne/kW h)

FAC

Solar fraction of space cooling

Fd

Solar fraction of domestic water heating

Fe

Plant emission factor (tonne CO2/kW h)

Fs

Solar fraction of space heating

Ft

Total solar fraction

Fr

Heat removal factor

G

Incident radiation on horizontal surface (W/m2)

Kt

Clearness index

L

Total load (kJ)

lcs

Life cycle savings ($)

Ms

Mass of the water in the storage tank (kg)

Pi

Factor relating life cycle fuel cost to first-year fuel cost savings

Factor relating life cycle by additional capital investment to initial

P2

investmet

Pg

Annual power generation (kW)

Qu

Useful energy rate gained by the collector (W)

Ta

Ambient temperature (°C )

Ti

Inlet collector temperature (°C )

1 o

Outlet collector temperature (°C )

Temperature of the combined stream of water returning from the air

TRN

conditioner (°C )

Ts

Temperature of water in the energy storage tank (°C )

Ul

Collector overall heat loss coefficient (W/m2 K)

Uls

Storage tank heat transfer loss coefficient (W/m2 K)

mc

Mass flow rate of water to the collector (kg/s)

mF

Mass flow rate of water to the air conditioner or air heater (kg/s)

ml

Mass flow rate of water to the service hot water system (kg/s)

Ws

Wind speed (m/s)

Vac

Space cooling efficiency

nc

Collector efficiency

no

Domestic water heating efficiency

ns

Space heating efficiency

n

Total system efficiency

(ra)

Transmittance-absorbance product

References

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Energy Information Administration (1999) Emissions of Greenhouse Gases in the United States 1998" Chapter 2, "Carbon Dioxide Emissions," DOE/EIA-0573 (98), Washington, DC.

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Kuwait Institute for Scientific Research (2006) Personal Communication.

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