Graphical Overview of a Solar Thermal System

Thermoelectric ConverterSun Available

Heat

Electronic-Control - Unit

General Design of a Solar Thermal System

Collektor

Main

Pump

T2

T1

ECUT)

Electronic Control Unit

Electronic Thermometer

Electronic Thermometer

Storage-Tank

Solar Thermal Model

Collektor

Pump

T2

T1

ECUT)

Electronic Control Unit

Electronic Thermometer

Electronic Thermometer

Storage-Tank

Solar Thermal Model Collector with Thermo-Tubes

Thermal-Solar-System-ControllerStorage Tank (Thermo-Flask)

Pump

Special thanks are going to Wellner Haustechnik, Bad Kreuznach, www.wellner-haustechnik.de, contributing the Thermotubes Collector Model

Panel-Sensor

Storage Tank Sensor

Thermoflask – Tubes

How evacuated tube collectors work

Thermos flasks can keep coffee and tea hot for hours because there is a vacuum insulated intermediate layer between the double vessel walls. With the two concentric glass tubes, evacuated tubes also form a hermetically sealed space that is vacuum insulated.

In addition to this, the outer surface of the inner tube is coated with a highly efficient, environmentally friendly absorber coating. This converts incident sunlight almost completely into heat and radiates almost no heat. The inner tube becomes hot while the outer enclosing tube remains cold.

Solar Thermal System - Controller

Flow-Chart Sensor Check and Heat-Control

Constant DELTA_T = 10

Restart Program

Read SerialNumber Sensor T1 (b7)

Copy SN Sensor T1 (b1 = b7)

Read SerialNumber Sensor T2 (b7)

b1=SN_T1 AND

b7=SN_T2?

Yes

No

„Sensor error“

Constant SN_T1 = 120Constant SN_T2 = 15

Read T1, T2

Show „T1 [°C] , T2= [°C ]“

Yes

NoT2 > T1?

ΔT = T2 – T1

ΔT > DELTA_T

No

Yes

„Pump ON“ „Pump OFF“

„Heat Control OFF“

Sensor-Check

Heat - Control

Program Pump-Control

• ;----------------------------------- constants ---------------------------------------------------• ;• symbol SN_T1 = 15 ; SerialNumber Sensor 1 (DALLAS 18B20)• symbol SN_T2 = 120 ; SerialNumber Sensor 2 (DALLAS 18B20)• symbol DELTA_T = 8 ; pump switching temperature difference • ; (betweeen solarpanel and storage tank)• ;• ; -------------------------------- main program --------------------------------------------------• ;• init: low 0:high 5 : high 6 ; Pump OFF (port 0), Sensor-LED's OFF (port 5,6)• gosub message ; displays starting initialization• gosub init0 ; checking the temperature sensors • ;• main: gosub lcd1 ; status message• readowsn 6 ; reading the serial number of T1• b1 = b7 ; caching b7 of the serial number• readowsn 7 ; reading the serial number of T2• b2 = b7 ; caching not absolutely required but more systematically • if b2 = SN_T2 AND b1 = SN_T1 then ; sensors connected ?• readtemp 6,b1 ; reading the value T1 (requires about 700 ms) • readtemp 7,b2 ; reading the value T2 (requires about 700 ms)• gosub lcd2 ; displays the sensor values on the LCD device• if b2 >= b1 then ; in this case, the difference b2-b2 is greater 10 • b3 = b2-b1 ; calculating delta T• if b3 > DELTA_T then ; delta T > DELTA_T-degrees: makes pump working ?• high 0 ; pump ON• gosub lcd3 ; message pump ON• else ; if not, do this:• low 0 ; pump OFF• gosub lcd4 ; message pump OFF• endif• else • gosub lcd10 ; if T2 < T1 then message: “heat control = 0ff”• endif • else• goto init ; if one ore both sensors are failing• endif • goto main • end