Summary

• Thermotecnical part (Valerio)

• Renewable energies• Solar panels • Astronomical calculations

• Electronic part (Matteo 2nd)

• Temperature sensors• PLC and control tecniques• Actuators

Our project

• One of the subjects of Comenius Project is to use renewable energy sources applied to domotica

• Therefore we thought to project a solar panel plant for sanitary warm water

• The main components of the plant are– solar panels– pipes– a pump and valves– a solar boiler

• The system will be electronically controlled in order to save energy

The solar panel• A typical flat-plate solar

panel is a metal box with a glass or plastic cover (called glazing) on the top and a dark coloured absorber plate

• Sunlight passes through the glazing and the energy changing by solar into heat energy

… but it is possible create a solar panel also

with…

Bottles…..

Captation system• A solution (water and nanti-

freeze) flowing in the circuit is heated by the sun and transfers heat to the water contained in a storage tank

• A pump lets the water to circulate in the system. If the water-no frost solution temperature is lower than setup value, the pump is stopped and the heating is guaranted by hot water heated by gas or electric boyler

Solar panel position (slope and orientation)

Solar radiation catched by fixed solar panel, especially in north regions, is unsufficient to guarantee enough hot water production

We thought to project a rotating panel able to follow the sun in order to maximize the solar radiation

Panel slope• The panel should be located

perpendicular to sun direction when it is at its peak

• Sun direction changes during the

year. Therefore in winter the panel should be almost vertical, in summer almost horizontal

• But in winter the radiation is weak, in summer is excessive, so we prefer to maximize radiation in spring and autumn times. In this case the angle of the sun is equal to the latitude. The slope of our panel in Modena is 44°

Chief parameters

• Latitude Φ: angle from the equator line to our place location:– Modena 44,23° N– Beckescaba 46,69° N– Pilsen 49,74° N – Genk 50,97° N– Recklinghausen 51,57° N– Kokemaki 61,26° N

Φ

Panel orientation

• The fraction of solar radiation catched by panel depends from sun position from sun raise to sunset

• We calculated the angle covered by sun for each month. It depends from the solar declination, the latitude, the daylight

Solar declination

• δ: angle between the sun direction when it is at peak and the equator line. It is variable during the year, on 21 March and 21 September the sun is perpendicular to equator line and his value is 0; on June and December 21 it is perpendicular to Cancer and Capricorn tropic and the angle is +/ - 23°

The sun position

The sun position when it is at peak changes during the year according to δ and the latitude: relation is 90° - (Φ – δ)

Today february 5, the sun position on the horizont and the day light are:

• Modena 29,5° 9 50

• Kokemaki 12,3° 7 42

• Beckescsaba 26,9° 9 36

• Pilsen 23,8° 9 18

• Recklinghausen 22° 9 06

• Genk 22,6° 9 12

Calculation of each hour radiation

• The data of radiation for the whole day have been taken on www.solaritaly.it

thanks to this graph we calculated the radiation each hour and the fraction catched by panel

Panel efficiency

• The efficiency of the solar panel is the ratio between the energy transferred to the fluid vector and the catched radiation. Infact a part of the radiation is reflected, a part is lost due to the environment. Therefore the efficiency is variable and depends upon the external temperature, the radiation, and the fluid temperature

Results: the moving panel tansmits to the fluid 25% more energy. A family of 4 persons needs 200 kwh in one month for sanitary water. Using 2 m2 panel we are self sufficient from march to september

July 160 114

Aug 129 92

Sept 118 98

Oct 84 77

Nov 63 56

dec 46 41

Kwh/m2 per month

Transmitted by moving panel

Transmitted by fixed panel

Jan 62 55

Feb 75 66

March 96 79

Apr 123 101

May 127 108

june 144 104

How does the system work?

• Each sensor converts a temperature in a proportional voltage – solution– tank water

Temperature sensors

Thermocouples

Termistors

Resistance Termal Devices (RTD)

Thermoresistors

Integrated sensors

Temperature sensor: LM335

• The LM35 series are precision integrated-circuit temperature

sensors, whose output voltage is linearly proportional to the

Celsius (Centigrade) temperature.

LM335 used• enviroment temperature• heating system temperature

How does the system work?

• PLC controls the temperature of the water using PID regulation

PID

• PID regulation is a mathematic calculation that allows to control a process or a system, changing the value of a signal to achieve the set point value.

• This calculation uses proportional, integrative and derivative functions to maintain this value in time

Electronic part

• The project is controlled by a PLC (programmable logic controller) Siemens S7-200

• This device is the brain of the system

How does the system work?

• Actuator can be activated by the PLC to generate heat

Heating system regolation

Methods to control the heating system:

• ON-OFF: the actuator (the heatresistance) is completly off or completly on at the max power. This control can let oscillate the system and stress hardly the actuator.

• PWM (Pulse Width Modulation): it is a regulation technique that controls the power given to the actuator changing the duty cycle and not the frequency of the control signal.

What we mean to do in the future

• This year:

• Project pannel, boiler, pump, pipes and draw a P.& I. scheme

• Introduce devices in our boiler

• Make the constructive drawning of the rotating pannel

• Next year: realize the mechanical structure