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Prepared by:

Hanan Radi Hala El_Shorafa Kholoud Thabet Rania Nassar

Supervised by: Dr. Hatem El_ AidyDiscussed by : Dr. Basel Hamad

Introduction Objective Heating water types Solar water heating system Motion of the sun Hardware design Software design Simulation and results Conclusion Recommendation and future outcomes

Statistical

30 houses in Nusseirat area were surveyed on what methods they used for water heating. All of these houses owned a solar water heating system; in addition to an electrical tankless heaters.

In the same specified area we found that people suffer four times a week from power outage.

The table shows a model of weekly power outage for the Nusseirat area.

Weekly power outage schedule

TimesDays

8 am : 2 pm 2 pm : 10 pm

Saturday

Sunday

Monday

Tuesday

Wednesday

Thursday

Friday

Fixed Solar system:

The installation of solar waterheating has become the norm in Gaza Strip since 1980’s.

Problem:

The mirrors do not move, and the peak energy reach at noon where the sun is perpendicular on the mirrors. But at night time this system is idle.

Solution:

For developing the solar system and making it more efficient in heating water.

A new sun tracking system is proposed.

Tracking solar system:

The idea is to make this system more efficient by supply peak energy at all the times. This means that the sun is always perpendicular on the mirrors.

Tracker types:

1.Single axis trackers

2.Dual axis trackers

a Tip – tilt dual axis tracker (TTDAT)

b Azimuth-Altitude dual axis tracker

(AADAT)

Geographical Location

• The climate of a place depends on its geographical location.

• The geographical location depends on:

1. Latitude

2. Longitude

Astronomical Location of the Sun

The basic position of the sun at any instant can be described by two angles: 1. The azimuth angle

2. The altitude angle

1. Azimuth angle

The solar azimuth angle is the angular distance between due South and the projection of the line of sight to the sun on the ground.

cos (AZ) = (sin (Al) * sin (L) - sin (D)) / (cos (Al) * cos (L))

Where:

AZ = Solar azimuth angleAl = Solar altitude angleL = Latitude D = Declination

2. Altitude angle The altitude angle describes how high the sun appears in the sky.

sin (Al) = [cos (L) * cos (D) * cos (H)] + [sin (L) * sin (D)]

Where:

Al = Solar altitude angle.L = Latitude D = Declination H = Hour angle.

1. Electrical circuits

2. Mechanical implementation

1. Electrical circuits:

Power circuit

Control circuit

Driver circuit

Controller Motors

Mirror

Outputref.

Power circuit

Control circuit:

Keypad Microcontroller LCD

DS1307 74LS244

Keypad Microcontroller LCD

DS1307 74LS244

1. DS1307

• Real-Time Clock (RTC) Counts Seconds,Minutes, Hours, Date of the Month, Month,Day of the week, and Year with Leap-Year

• 56-Bytes, with NV SRAM.

• I2C Serial Interface

• Battery - backed

• Consumes Less than 500nA in Battery-Backup Mode with Oscillator Running

Typical operation circuit

b 74LS244 ( 3-state buffer)

2. 74LS244 ( 3-state buffer)

• In digital electronics 3-state logic allows an output port to assume a high impedance state in addition to the 0 and 1 logic levels

• Active-low input called OE (Output Enable)

L = LOW logic level

H = HIGH logic level

Z = High impedance

Three-state buffers can also be used to implement efficient multiplexers especially those with large numbers of inputs.

For two stepper motor, using 74LS244 to select the motor which must rotate.

Driver circuit

• The SLA7024M is designed for high-performance operation of 2-phase, Unipolar stepper motors .

• This driver is most important for limiting and regulating the input current to the stepper motors.

How the stepper motor can turn left and right??

For half step operation for stepper motor the truth table of SLA7024M is shown in the table

0 0 1 0 = 0xF21 0 0 0 = 0xF8

1 0 1 0 = 0xFA

2. Mechanical design

• Our system is designed to have dual axis that connected with two stepper motors.

• The size of the load mirror is (35*35cm).

• Using limit switch.

Stepper motor

The motor's position can be controlled precisely without any feedback mechanism (Open-loop controller).

For solar system using unipolar stepper motor than other types of motors

a.Unipolar stepper motor than bipolar

b. Unipolar stepper motor than servo motor

a. Unipolar stepper motor than bipolar

A unipolar stepper motor has two windings per phase, one for each direction of magnetic field. It can be reversed without switching the direction of current.

Other hands, bipolar motors have a single winding per phase. The current in a winding needs to be reversed in order to reverse a magnetic pole, so the driving circuit must be more complicate.

b. Unipolar stepper motor than servo motor

Servomotors require analog feedback control systems of some type. Typically, this involves a potentiometer to provide feedback about the rotor position.

Stepper motors can be used in simple open-loop control systems.

Calibration

For high precision required in the angle were used a half step operation than full step, for normal unipolar full step have 1.8°, so for half step is 1.8°/2 = 0.9°. As is well known that the full period have 360°.

To find out the number of turns which must be the motor full cycle of rotation:

1.For full period

360/0.9 = 400 steps

2. The half stepper operation from its truth table must rotate 8 steps for full turn, so, the numbers of turns for motors to have full cycle is

400/8 = 50 turns .

• For the altitude angle, the vertical axis from the experiment at this axis was found that for every 1.5 turns have 1°, so, to know angle which the full turns make

Al angle = (50 turn * 1°) / 1.5 turn

• For the azimuth angle, from experiment at the horizontal axis, for every 1 turn have 1°.

Az angle = (50 turn * 1°) / 1 turn

1. Keypad

In solar system simulation by proteus using 3*4 keys matrix as shown in the figure.

3*4 keypad

In hardware implementation using 4*4 keypad because of motors functions.

4*4 keypad

2. Microcontroller (PIC18F4620)

The advantages of PIC18F4620:-

• Program memory 64 Kbytes.• Data memory SRAM 3968 bytes.• Data memory EEPROM 1024 bytes.• CPU up to 10 MIPS • 8 x 8 Single-Cycle Hardware Multiplier

3. LCD

2*20 LCD is used as shown in the figure

Solar LCD messages

After building hardware system, from the response of the system, we observe many errors that are differences between the hardware values and the actual values from data base, and mechanical design error.

Software errors

1. Differences in Sunrise and sunsetTable (5-1) Sunrise, sunset values

Sun rise(data)

Sun rise (simulation)

difference Error percentage

6:31 6:32 0.01 0.15 %

6:31 6:31 0.00 0.00%

6:30 6:30 0.00 0.00%

6:29 6:29 0.00 0.00%

6:28 6:28 0.00 0.00%

6:27 6:28 0.01 0.15 %

6:27 6:27 0.00 0.00%

To calculate the percentage error for one value at 6/2/2011 let:Error percentage = [(theoretical value – practical value) / theoretical] * 100%(6:31 – 6:32) / 6:31 = 0.15 %

Sun set(data)

Sun set (simulation)


5:22 5:21 0.01 0.19 %

5:22 5:22 0.00 0.00%

5:23 5:23 0.00 0.00%

5:24 5:24 0.00 0.00%

5:25 5:25 0.00 0.00%

5:26 5:26 0.00 0.00%

5:27 5:26 0.01 0.19 %

2. Differences in angles value

Altitude

(data base)

Altitude

(simulation)


35.27 35.25 0.02 0.05%

41.08 41.06 0.02 0.05%

43.03 43.03 0.00 0.00%

40.67 40.67 0.00 0.00%

34.54 34.54 0.00 0.00%

25.73 25.73 0.00 0.00%

15.20 15.20 0.00 0.00%

Azimuth

(data base)

Azimuth

(simulation)


144.84 144.76 0.08 0.05%

161.70 161.61 0.09 0.05%

-178.99 -179.06 0.07 0.04%

-159.82 -159.89 0.07 0.04%

-143.27 -143.34 0.07 0.04%

-130.01 -130.08 0.07 0.05%

-119.44 -119.51 0.07 0.05%

Hardware errors

As known practical results are not always as accurate as the theoretical results, after we build the mechanical model we noted that the azimuth angle began at approximately 120° and ideally it must begin at 90° so there’s 30° as error.

• The problem is the power cut.

• The solution is to convert fixed solar system to movable one.

• Using microcontroller to program all equations to find the two angles.

•Using stepper motor to achieve the exact position.

• Using photovoltaic cells ( solar cells ) in our system instead of the mirror because of it's ability to produce direct current electricity from sun light, which is solve the problem of electricity cut off.

• For large system, using servo motor instead of stepper.

• In power station generation, using PLC than microcontroller.

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