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