1. Ambient Temperature (˚C) Results and Discussion
Design and Analysis of a Solar Domestic Water Heating System with an Auxiliary Boiler for the conditions of Dhahran
Prepared By: Mohamed Hussein ( ), Muhammad Lari ( )
Instructor: Dr. Shahzada Zaman Shuja
ME-458 (Design of Thermo-Fluid Systems)
Abstract
Table 1. Meteorological data for Dhahran for the average day of March 2013.
Hour
Solar radiation
(W/m2)
Ambient Temperature (˚C)
Wind Speed
(m/s)
07:00
121.4
13.49
6.59
08:00
403.8
14.11
7.066
09:00
678.2
15.49
6.318
10:00
890.7
16.9
5.824
11:00
1032
18.29
6.248
12:00
1092
19.4
6.716
13:00
1070
20.6
6.797
14:00
950.2
21.85
6.223
15:00
769.4
21.58
6.431
16:00
542
20.73
7.073
17:00
228.1
19.92
7.97
Depletion of fuel reserves and an increase in pollution has triggered enormous research in the utilization of renewable resources, such as solar as an alternative source of energy.
In this study, a domestic solar water heating system was designed using HVAC solution software and analyzed using EES software for the meteorological conditions of Dhahran.
The system consists of a flat plate solar collector, a heat exchanger, and an auxiliary boiler with hourly climate data for March 2013 and a hot water load profile for a 4-person family used as inputs.
Results show that contribution of solar energy in water heating remains high for the most part of day hence the conditions of Dhahran favor the installation of the proposed system.
Figure 6. Hourly auxiliary thermal energy required from the boiler to cover the thermal load.
System Description
System consists of a flat plate solar collector with an area of 4 m2 , sloped at angle of 26˚(latitude of Dhahran) receiving water at a mass flow rate of 0.022kg/s per unit collector area. The heat exchanger housed inside the water storage tank has an effective heat transfer area of 0.4 m2 . An auxiliary boiler of 2 kW is used to meet the thermal load on the system in case solar energy is insufficient.
Hourly meteorological data experimentally measured at Centre of Engineering Research, King Fahd University of Petroleum and Minerals for Dhahran for the average day of the month of March 2013 are used as input.
Thermal load is provided to the system in the form of a load profile, as shown in Figure 4, which is assumed as the hourly hot water consumption rate for a household of 4 persons. Cold water feed to the hot water tank enters at a temperature of 10˚ C and is assumed to leave at a temperature of 50˚ C to the hot water fixtures.
Figure 4. Hourly load profile of hot water consumption per person.
Results and Discussion
Figure 7. Hourly solar fraction, denotes the percentage of thermal load covered by solar
Collector fluid experiences a steady rise in temperature due to incident radiation which heats up the fluid. Useful thermal energy from the sun increases along the day, reaching a peak value of 1400 W at 12:00 hours (noon) and then decreases throughout the remainder of the day. This trend can be observed from Figure 5.
To heat water up to the required temperature for domestic use, additional thermal energy is required, which is obtained from the auxiliary boiler. The amount of additional energy required depends on the thermal load. Figure 6 shows the hourly trend for auxiliary energy which matches the hourly trend for the load (Figure 4).
Figure 7 shows the hourly trend for solar fraction which denotes the percentage of thermal load covered by solar. Solar fractions are generally high during mid-day with a peak solar fraction of 80% at (3:00 AM).
Conclusions
In this study the performance of a flat plate solar collector, used in combination with an auxiliary boiler, is analyzed for the meteorological conditions of Dhahran.
Results show that the contribution of solar energy in heating water remains higher than 50% for the most part of the day.
Hence solar water heating for domestic purposes in Dhahran can be a very attractive option.
Although the results favor the use of solar water heating in Dhahran, further analysis should be done to assess the economic feasibility of the system.
Figure 1. Layout of the solar water heater system.
Figure 3. Schematic drawing of a flat plate collector
Figure 5. Hourly useful thermal energy gained from the solar collector
Figure 2. Flat plate collector