Erasmus+ ERASMUS+-project: 2016-1-BE02-KA202-017316

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“Solar Power Unit”

1 Description

The greenhouse that VTI-Tielt has in mind is not only a special shaped

structure but it’s also a “green” house. That means, it generate its own

electricity, store it and the power management can be monitored from a

distance.

So in this project we will build the setup. The mechanical installation of the

solar panels, the connection via the charger with the batteries. On top we will

add sensors to check the current and voltage produced by the panels, the

current drained from the batteries and a sensor that keeps an eye on the

battery voltage. An Arduino will collect the data, transmit it to the master

computer, a Raspberry PI3, and to a local LCD display.

2 Task.

Belgium is a country close to the sea. So it has a mild climate. But we also

have a lot of overcast days. Sometimes the sun is hidden for a week. That

reduces the solar energy dramatically. Because of that, one panel won’t be

enough so we will take 2.

The solar panels we use, generate a voltage of about 27 Volt. Reducing 27V

to 12V to charge a battery isn’t the best option. Instead we will use 2x12V

batteries and take 24V as main power. The advantage is that it makes it

possible to work in the future with industrial PLC’s and sensors as well.

3 Setup.

The hart of the facility is 2 silicon batteries 12V each, 2 solar panels and a

charger. With these we will be able to collect, store and deliver electricity to

the greenhouse. Beside the main voltage of 24VDC we also need 230VAC. To

generate this we will use a convertor with 24VDC input to 230VAC output. A

300W type is enough to feed the 230V users.

On top we will need a fuse box so the installation is safe against short-circuit

and overload.

That makes a setup that can be simplifies to this.

Erasmus+ ERASMUS+-project: 2016-1-BE02-KA202-017316

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4 Technical info

The solar panels. Version 1 Version 2

Solar 1 Solar 2

Charger Batteries Invertor

24VDC 230VAC

300W2x12V

Erasmus+ ERASMUS+-project: 2016-1-BE02-KA202-017316

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The charger: Steca PR2020. Nedis Power Inverter 24 VDC - AC 230V -

300W

Fusebox: Fuses: 2A / 6A / 25A 2P 3KA

GE EPP32C02/ 06/ 25

Arduino UNO I2C-

LCD

Current sensor ACS712 20A Voltage sensor: 25V to 5V

Erasmus+ ERASMUS+-project: 2016-1-BE02-KA202-017316

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DC-DC convertor: Input 4-40V Output 1.3-37V 2A. (LM2596)

5 Wiring

Wire-up step by step the “Solar Power Unit”

Warning, batteries are charged and can be dangerous when shorten

the poles.

Solar panels

- Check the voltage with a Voltmeter and determine the positive and negative pole

- Connect the solar panels in parallel or series according information of the

charger.

- Extend the wires for at least 8m

- Connect the wires with the charger

- Connect the solar panels and check the voltage on the charger

Batteries

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- Before the connection is made between the batteries extend the wires 2m

- Disconnect the solar panels

- Connect the battery wires to the charger. Pay attention on “+” and “-“

- Prepare the connection to put the batteries in series. Pay attention on “+” and “-“

- Check the voltage on the charger. It has to be 24V.

Invertor

- Disconnect batteries and solar panels in order to work save.

- Connect the invertor parallel with the “+” and “-“ on the batteries.

- reconnect the batteries and de panels.

- But a load on the invertor output.

- Check the voltage on the invertor on both ends.

General test

- Check the charger, test voltage, current and al parameters according the manual

- Check the invertor and put a 230V load on it of at least 200W.

- Determine the relation between fully exposed or partly covered solar panels and

the output

- Look for the best orientation to the sun according the compass directions.

- Clean-up the wiring.

End of part one.

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6 Electronics

Part 2. This can fully prepared in the classroom. Once ready the elektronics

can be hooked on the outdoor Solar Power Unit

As mentioned we will use a Arduino to collect the sensor information. The

current and voltage sensor are analogue, so use analogue inputs. Display the

information on a 4x20 LCD.

Learn to work with a IC2 LDC. Hook the display on the IC2 lines and the 5V.

Example: I2C_LCD_4x20_OK

The current voltage.

- For this we use a ACS712 sensor. There are 3 types, 5A, 20A and 30A.

We will use the 20A version. To learn more about, watch the video’s.

https://www.youtube.com/watch?v=UF5jrnXvTlM

https://www.youtube.com/watch?v=lisprJs5sNU

https://www.youtube.com/watch?v=etsIFUUhO6I

- Write a program to determine the correct current values and check the

results with a power supply. Display the info on the I2C LCD display.

The voltage sensor.

- The voltage sensor is actually a voltage divider, made with two resistors.

Input 25V- output 5V. In order to make the sensor ready to accept a

higher voltage, 40V, an external resistor in series is needed. Calculate the

right one to measure 40V instead of 25V. Adapt the software and

calibrate the calculated value before display the results. Use a Voltmeter

to check.

- Example: LCD_I2C_2x16_I_U_leonardo (The program is written for a

Arduino Leonardo)

- Adapt the program to use it on a UNO and the new sensor ready for 40V

instead of 25V.

Screen layout.

- In order to display the information in a proper way, group solar panel and

battery information. First Solar Voltage, Solar Current then Battery

Voltage and Battery Current

- Prepare a string with the four values and send the it via RS232 to the

Raspberry PI3. The Raspberry will make the connection with internet.

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- Hook the electronics on the Solar Power Unit out door and compare the

results with the ones you see on the Charger and your personal

voltmeter.

7 Final setup