MAB 4523 ALTERNATIVE ENERGY LABORATORY MECHANICAL ENGINEERING DEPARTMENT

January-May 2011

SECTION B (To be filled by students)

NAME ID TIME IN TIME OUT SIGN

SECTION D (by Examiner)

ITEM MARKS

ALLOCATED SCORE REMARKS

Abstract 10

Objectives 10

Theory & Procedure 10

Data collection 20

Results 20

Conclusions & Discussion 20

Report Format / Style 10

TOTAL 100

SECTION A (To be filled by students)

DATE

EXP # & TITLE

GROUP

2

- FOR INTERNAL USE ONLY -

INSTRUCTION TO STUDENTS 

 

1. Read the Laboratory manual before lab session begins 

2. There are 2 experiments in solar forced circulation unit in this lab session 

3. Do all the experiments and report on the sheet attached 

4. The total maximum duration of the laboratory session is 4 hours 

5. Each group should submit a report at the end of the lab session.  

6. Plagiarism is strictly prohibited. Any report found improperly referenced and 

copied from others will be rejected 

   

Mechanical Engineering Department Universiti Teknologi PETRONAS 

2011 

MAB 4523 ALTERNATIVE ENERGY  LABORATORY MANUAL 

SOLAR ENERGY – SOLAR WATER HEATER 

3

I. Introduction 1.1 Solar energy The sun is a source of almost all of the energy available on earth. The exceptions are

attributable to moon-tides, radioactive material, and the earth's residual internal heat.

Solar energy produced directly by the sun and can be gained almost elsewhere on the

Earth. It has been harnessed by humans since ancient times using a range of ever-

evolving technologies. Solar radiations, along with secondary solar-powered resources

such as wind and wave power, hydroelectricity and biomass, account for most of the

available renewable energy on earth.[1]

Solar technologies are broadly characterized as either passive solar or active solar

depending on the way they capture, convert and distribute solar energy. Active solar

techniques uses electrical or mechanical equipment, include the use of photovoltaic

panels and solar thermal collectors to harness the energy. Passive solar techniques

include orienting a building to the Sun, selecting materials with favorable thermal mass

or light dispersing properties, and designing spaces that naturally circulate air.[2]

1.2 Solar water heater Solar water heating is heating of water using the solar energy. Solar heating systems are

generally composed of solar thermal collectors, a water storage tank or another point of

usage, interconnecting pipes and a fluid system to move the heat from the collector to the

tank. This thermodynamic approach is distinct from semiconductor photovoltaic (PV)

cells that generate electricity from light; solar water heating deals with the direct heating

of liquids by the sun where no electricity is directly generated. A solar water heating

system may use electricity for pumping the fluid, and have a reservoir or tank for heat

storage and subsequent use. The water can be heated for a wide variety of uses, including

home, business and industrial uses. Heating swimming pools, under-floor heating or

energy input for space heating or cooling are common examples of solar water heating.[3]

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Figure 1. Forced circulation solar water heater

(http://en.wikipedia.org/wiki/Solar_water_heating)

II. AUTOMATED SOLAR UNIT (Measurement and Determination of Solar Collector Efficiency)

(Series)

2.1 Experiment Objectives At the end of the lab demonstration and experiment, students are able to determine the

efficiencies of a solar collector at different water flow rates.

2.2 Equipment Details TD403 - Automated Solar Unit The system is designed for the study of the problems encountered in transforming solar energy into thermal energy. The efficiency of a solar panel can be calculated by carrying out experiments at different temperature and irradiation values and with reflected or diffused energy. Using a double

5

panel, it is possible to carry out experiments with panels connected in series or parallel. An electronic panel is used to automatically control the system at different temperatures. The system consists of: 1. Hydraulic Circuit

a. Aluminium and copper panel

o Black surface to be exposed to the sun with an extremely high absorption

o Rear insulation o A mount for tilting with respect to the horizontal plane o Divided into two sub-panels for series and parallel operation

b. Circulation pump

o Power 40 W o Variable speed

c. Expansion box

o Max pressure of 5 bars o Capacity 4 liters

d. Safety valve e. Boiler

o produces sanitary hot water, complete with thermostatic electrical

resistance. o Capacity 50 liters

f. Flexible piping

o 1/2 in. insulated

2. Instrumentation

a. Electronic panel

o Complete with probes. It switches the circulator on and off at preset temperatures

b. Flowmeter

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o Range 10 t 100 liters/hour

c. Rod thermometer

o TWO (2) Analogue thermometers

d. Portable digital thermometer

o Portable industrial electronic instrument having the following

characteristics: - digital display - resolution 1°C - accuracy ± 0.2% - probe k-type thermocoupling for contact employment, - standard length 200 mm; Diameter = 4 mm - feed 19 V battery

3. Trolley Base

o Moveable trolley with 4 casters

7

Figure 1. Solar automated circulation unit assembly.

8

2.3 Test Procedures

Panels in Series

1. Close valves 7 and 8

2. Open valve 4

3. Adjust the flow rate using valve 10

4. Note the thermometer readings

5. Note the measurement on the flow meter, identical for both collectors

2.4 Efficiency of the solar collector The "eta" (η) efficiency of a collector is defined as the ratio between the power

absorbed by the thermal carrier (Pu) and that absorbed by the collector exposed to

radiating energy (Pi); this is expressed by the formula:

η (eta) = Pu / Pi Pu [W] can be calculated using the formula:

][sec/3600)(hr

crttQP ofifu

u

−=

Where;

Q = water flow rate as indicated by the flow meter [liters/hour]

tfu = temperature of the same fluid at the output of the collector indicated on

the appropriate thermometer [ Co ]

tfi = fluid temperature in the input [ Co ]

ro = mass, assumed constant, of the thermal carrier; as a first approximation

for water we can consider ro = 1 [kg/liter]

C = specific heat, assumed constant; as a first approximation for water we

can consider c = 4 180 [J/kg°C].

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Using these approximations the formula becomes:

Pu = 1.161 Q (tfu - tfi) Pi[W] can be calculated using the formula:

Pi = Ps . A Where;

Ps = specific flow of radiating energy and can be measured using a solarimeter

[ W/m2]

A ≈ 2.3 m2 (Rough actual collecting area).

2.5 Results and Calculations

2.5.1. Efficiency of the unit (in Series) Record the data and calculate the efficiency in series connection.

No Q [lit./h] tfu [oC] tfi [oC] Pu [W] Ps [W/m2] Pi [W] η [%]

1

2

3

4

5

Efficiency of collector (in series) : 1 ................%

n

n

n

ηη = =

∑

10

2.5.2. Efficiency of the unit (in Parallel) Record the data and calculate the efficiency in series connection.

No Q [lit./h] tfu [oC] tfi [oC] Pu [W] Ps [W/m2] Pi [W] η [%]

1

2

3

4

5

Efficiency of collector (in series) : 1 ................%

n

n

n

ηη = =

∑

11

III. The Cussons P7140 Solar Heating Apparatus 3.1 Experiment Objectives At the end of the lab demonstration and experiment, students are able to determine the

efficiencies of a solar collector at different inlet water temperature to the panel.

3.2 The Cussons P7140 Solar Heating Apparatus The Cussons P7140 Solar Heating Apparatus is designed to allow experiments to be carried but on the performance of this type of Solar Heating Apparatus. The apparatus is mounted in and on a simple metal frame, which is provided with castors for ease of movement. Carried on four adjustable feet projecting through the top of the frame is a shallow fibreglass-evaporating tray, on which is mounted the solar panel and which, in turn, is covered by a sheet of armour plate glass. The glass is mounted at an angle of 120 to the base of the tray to ensure that any condensate that forms within the tray will run down the glass even when the tray is at its maximum tilt when reversed. Mounted inside the metal framework is an insulated reservoir, an electrically driven pump, a venturi flow meter, and a control panel. A lamp arrangement may be mounted over the glass as an optional extra, in place of sunlight. Water is pumped from the reservoir via the flow meter into a lower manifold from where it feeds through a number of heat collecting pipes of the solar panel, emerging in the upper manifold, from where it flows back into the reservoir for re-circulation around the system.

Figure 1 Schematic View of Apparatus

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Heat is transferred from the sunlight, or artificial light, into the solar panel gradually raising the temperature of the water in the circuit. When the water becomes too hot or the experiment is ended, mains water can be fed through a cooling coil passing through the reservoir. The solar panel comprises of a backing copper plate, painted black, which can be used on its own, or covered with a heat absorbing mat as required. The system is equipped with a pump of minimum size (10W output) to provide an acceptable flow rate. The purpose of the experiment is to record the heat absorbed from the light rather than from the pump. For this reason venture meter is used to record the flow rate as it has the lowest head loss. Instrumentation in the unit includes 8 thermocouples connected to a selector switch, the output of which is connected to a digital temperature display. The thermocouples measure temperatures at the following points: 1) Upper panel surface 2) Water reservoir temperature 3) Upper glass surface 4) Lower glass surface 5) Air space within the tray 6) Water onto the solar panel 7) Water out of the solar panel 8) Ambient air 3.3 Efficiency of the solar collector: The "eta" (η) efficiency of a collector is defined as the ratio between the power

absorbed by the thermal carrier (Pu) and that absorbed by the collector exposed to

radiating energy (Pi); this is expressed by the formula:

η (eta) = Pu / Pi Pu [W] can be calculated using the formula:

][sec/3600)(hr

crttQP ofifu

u

−=

Where;

Q = water flow rate as indicated by the flow meter [liters/hour]

tfu = temperature of the same fluid at the output of the collector indicated on

the appropriate thermometer [ Co ]

tfi = fluid temperature in the input [ Co ]

ro = mass, assumed constant, of the thermal carrier; as a first approximation

for water we can consider ro = 1 [kg/liter]

13

C = specific heat, assumed constant; as a first approximation for water we

can consider c = 4 180 [J/kg°C].

Using these approximations the formula becomes:

Pu = 1,161 Q (tfu - tfi) Pi[W] can be calculated using the formula:

Pi = Ps . A Where;

Ps = specific flow of radiating energy and can be measured using a solarimeter

[ W/m2]

Take 15 measurements and find the average. Five point along the center

line, five points along the diagonal line and five points along on one side)

A ≈ 1.34m2 (Rough actual collecting area).

3.4 Results and Calculations

Keeping the water flow rate constant Q = 144 Lit/Hr (2.4 Ltr/min) calculate the

efficiency of the water heater as the temperature of water at the inlet increases.

No tfi [oC] tfu [oC] Pu [W] Pi [W] η [%]

1

2

3

4

5

1 ................%

n

n

n

ηη = =

∑

14

Reference 1. Hersch, Paul & Zweibel, Kenneth; Basic Photovoltaic Principles and Methods;

Colorado, Solar Energy Research Institute US DOE; 1982 2. http://en.wikipedia.org/wiki/Solar_energy 3. http://en.wikipedia.org/wiki/Solar_water_heating 4. STEM-ISI Impianti, Solar Forced Circulation Unit. Technical Manual No.

1013/GB/91, 5. P7140-Cussons Technology –Solar Heating Apparatus