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Email :[email protected] Skype: ianfourfaith Tel:+86 130 2399 5926 Solar energy (also called photovoltaic power station) mostly consists of hundreds and thousands of photovoltaic panels.Stability of Photovoltaic power station is related to the output power of the photovoltaic array and even the working statue of every panel. How to monitor and diagnose the failure is the main problem for managing the photovoltaic station. At present, the main problem of the photovoltaic is hot spot.The so called hot spot phenomenon is part of the photovoltaic cells in photovoltaic panels monomer the obscured for a long time.According to Kirchhoff Voltage Law, these obscured photovoltaic cells monomer will get negative voltage, becomes the load circuit, and other work in the form of heat consumption of monomer of photovoltaic battery power, the heat accumulation for a long time can damage photovoltaic panels of packaging materials, even destroy the physical structure of the photovoltaic panels, and will cause permanent damage. At present, there are two ways for monitoring Photovoltaic array direct method and indirect method. Direct method is to directly measure the voltage and current of each panel, and then transfer the data to the pc by mod bus. But there exist a lot of problems in planning layout, default interface, line detection, line capacity etc..Indirect is to judge the working statue of battery by measuring the temperature difference of the battery. However, this method has some defects, such as can not distinguish between the state of the temperature difference is not obvious, real-time performance, accuracy and efficiency of fault detection depends on the testing equipment (infrared thermal imager) level, is not easy to implement online fault analysis and alarm, and so on. In comparison of these two methods, using wireless sensor to monitor the photovoltaic is of incomparable superiority. Wireless sensor transferring the data to three dimensional, space,conductor medium is no needed thus saving the lavor cost and maintain cost. This Solution is based on ZigBee Technology, Four-Faith ZigBee device is need for networking. 1 Solution 1.1 System The whole system is divided into three parts: terminal acquisition layer, data transmission layer and application managing layer. Terminal acquisition acts as performer, including monitoring node and center node. Monitoring node will transfer the date to the center node in form of multi-hop. Center node will transfer the data from Zigee monitoring area to the data transmission layer. Data transmission layer will act as agent will transfer the data from collection layer to application layer. Application layer is the monitoring center,as as the decider, responsible for data analysis and system managing maintain to realize remote monitoring in time and alarm. 1.1.1 Collection Terminal Device It needs to monitor multiply parameter, collection terminal device is used for realizing the parameter collection for each monitoring node. Such as photovoltaic modules voltage, Current sampling module is responsible for sampling photovoltaic components of voltage and current values to judge if there is failure. Temperature, humidity and light sensor is responsible for collection the environment data, and provide some data support. Acquisition terminal will transfer it via rs232 to ZigBee transfer unit.

Solar Energy Monitoring Based on ZigBee

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Solar Energy Monitoring Based on ZigBee

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Page 1: Solar Energy Monitoring Based on ZigBee

Email :[email protected] Skype: ianfourfaith Tel:+86 130 2399 5926

Solar energy (also called photovoltaic power station) mostly consists of hundreds and thousands of

photovoltaic panels.Stability of Photovoltaic power station is related to the output power of the

photovoltaic array and even the working statue of every panel. How to monitor and diagnose the failure is

the main problem for managing the photovoltaic station. At present, the main problem of the photovoltaic

is “hot spot” .The so called hot spot phenomenon is part of the photovoltaic cells in photovoltaic panels

monomer the obscured for a long time.According to Kirchhoff Voltage Law, these obscured photovoltaic

cells monomer will get negative voltage, becomes the load circuit, and other work in the form of heat

consumption of monomer of photovoltaic battery power, the heat accumulation for a long time can

damage photovoltaic panels of packaging materials, even destroy the physical structure of the

photovoltaic panels, and will cause permanent damage.

At present, there are two ways for monitoring Photovoltaic array direct method and indirect method.

Direct method is to directly measure the voltage and current of each panel, and then transfer the data to

the pc by mod bus. But there exist a lot of problems in planning layout, default interface, line detection,

line capacity etc..Indirect is to judge the working statue of battery by measuring the temperature

difference of the battery. However, this method has some defects, such as can not distinguish between

the state of the temperature difference is not obvious, real-time performance, accuracy and efficiency of

fault detection depends on the testing equipment (infrared thermal imager) level, is not easy to implement

online fault analysis and alarm, and so on.

In comparison of these two methods, using wireless sensor to monitor the photovoltaic is of

incomparable superiority. Wireless sensor transferring the data to three dimensional, space,conductor

medium is no needed thus saving the lavor cost and maintain cost.

This Solution is based on ZigBee Technology, Four-Faith ZigBee device is need for networking.

1 Solution

1.1 System

The whole system is divided into three parts: terminal acquisition layer, data transmission layer and

application managing layer. Terminal acquisition acts as performer, including monitoring node and center

node. Monitoring node will transfer the date to the center node in form of multi-hop. Center node will

transfer the data from Zigee monitoring area to the data transmission layer. Data transmission layer will

act as agent will transfer the data from collection layer to application layer. Application layer is the

monitoring center,as as the decider, responsible for data analysis and system managing maintain to

realize remote monitoring in time and alarm.

1.1.1 Collection Terminal Device

It needs to monitor multiply parameter, collection terminal device is used for realizing the parameter

collection for each monitoring node. Such as photovoltaic modules voltage, Current sampling module is

responsible for sampling photovoltaic components of voltage and current values to judge if there is failure.

Temperature, humidity and light sensor is responsible for collection the environment data, and provide

some data support. Acquisition terminal will transfer it via rs232 to ZigBee transfer unit.

Page 2: Solar Energy Monitoring Based on ZigBee

1.12 ZigBee Data transmission Unit

ZigBee data transmission layer use Four-Faith F8914 and F8114 to establish the data

transmission turn channel. When the ZigBee device receive data from acquisition layer or through

ZigBee, the data will be transf fed to the managing layer. Meanwhile, application layer will also send the

control command to each node via ZigBee network to realize double way communication realize remote

monitoring.

In this case, we use two model of ZigBee Products: One is ZigBee terminal F8914, another is

ZigBee GPRS modem F8114. F8914 fistly send the data to the center node via ZigBee network, then

F8114 works as center node, then transfer thedata to the monitoring center via gprs network.

1.1.3 Application managing layer

Application layer is mainly center monitoring system, which consist of pc server and platform

software. When the center system receive the data from the transmission layer, it will analysis the data

and operate according to the analysis like send our alarm information or send out control command.

1.2 Network Structure

According to the distance between the managing center and the photovoltaic array, we use two

kinds of structure.

When the center is near the photovoltaic array, we will use only F8914, only Zigbee network is

needed.

As below shows:

Page 3: Solar Energy Monitoring Based on ZigBee

When the center managing center is far away from the photovoltaic,F8914 will work as monitoring

node and F8114 as center node, F8914 will transfer the data to F8114 via ZigBee network, and then

F8114 RS422 ZigBee will transfer the ZigBee data to TCP/IP data and then via gprs network to send to

managing center.

When F8114 transfer the data to the monitoring , there are several access to the network

1. The center use APN special line, all the terminal use fixed ip. The client center access the mobile

company via gprs wireless network, an GRE channel is established between GGSN and router. An

special APN is assigned for the client, others can not apply for the APN.The user can establish RADIUS

server internal to ensure the internal security. User can build DHCP server, and assign the internal

address for the authentication user.

This solution is greatly improved in real time , security and stability compared with the previous

solution.

Page 4: Solar Energy Monitoring Based on ZigBee

The control center adapt ADSL connection, and use IP+DNS. User need to open the dynamic

domain name .IP MODEM need to connect to the DNS server by domain addressing way first, and then

find center pubic IP by DNS server ,establishing a connection.This way can greatly save the cost of the

public static IP, but stability is subject to the stability of the DNS server, so looking for reliable DNS

service is necessary .This solution is suitable for small-scale applications.

3.Control center use ADSL INTELNET public network connections, such as using public fixed IP

service.This solution need o apply to operators for ADSL broadband business, center has a public static

IP.IP MODEM directly connect to the center. It is reliable connection, this solution is recommended.

Other network

Four-Faith Zigbee device not only can be used for transparent data transmission, also support IO

acquisition. In this solution, we can also use Zigbee device for terminal IO acquisition and data

transmission. Four-Faith ZigBee device supply 5 IO.3 analog input ,2 digital input, puzzle input and

output.Analog voltage input is 0-5v, current input is 0-20ma, digital input is 0-0.33v, acquisition accuracy

is 12bit.

When Four-Faith device used as IO acquisition, the working mode should set as AT or API. The

difference between this working mode and transparent mode is that for transparent mode, the center

send out the data in the form of broadcast, the terminal can not be set unless the address is changed

every time. For AT mode,it is used in the data acquisition terminal and receiver terminal, IO acquisition

report the data in the form of AT command. Meanwhile, under the mode of AT,the center mode can use

AT+TXA= Address, the value is for which ZigBee terminal to send to. The function of API mode is same

as AT mode, hexadecimal is used by API mode, and there is check code, xor and inspection.

When ZigBee Device is used as IO data acquisition, the working mode should be set as AT. When

data is collected, there are two mode for data reporting. When the reporting time is set as non zero value,

it is automatically reported,the IO will report the data every several time according to the setting time.

When the reporting time is set as zero, it needs the upper software to send the command AT+Nvn=to

consult the data, analog acquisition need to be transferred get the real value as below:

Page 5: Solar Energy Monitoring Based on ZigBee

Voltage=(collected value)*3.3*20.16/(2047*12.1)(V)

3.3: Voltage

20.16: Resistance Value// Two resistance 12.1(Resistance 1)+8.06(Resistance 2)

2047: ADC Range //211

12.1:(Resistance 1)

Current=(Collected Value)*3.3*1000/(2047*150) (mA)

3.3: Voltage

1000: mA unit transfer

2047: ADC Range //211

150:Resistance Value

Meanwhile, when ZigBee device used as IO acquisition, the upper software should be developed

according to Four-Faith protocol, that is should according to the AT command in the user manual.

2. Features:

Page 6: Solar Energy Monitoring Based on ZigBee

1.Wireless, reduce the complexity of the photovoltaic array monitoring system

2.Low cost: Simple and free of patent change

3.Intelligent, each node will set up the connection automatically

4.Support the star, tree, the net network with strong network connection capability, can support

65000 nodes

5.Industrial grade design with metal shell, DC12V/500mA power supply.Operate temperature:

-25~+65ºC. Storage temperature -40~+85ºC. Relative humidity 95%(unfreezing); Multi WDT design,

suitable for oil well application.

6.The communication range for ZigBee terminal is 2k meter.

7.No cost is needed for ZigBee communication, large cost is saved for the whole project.

8.Easy configuration, easy installation

With the increase of the request and technology, ZigBee will have a broad application in remote

monitoring.

Ⅲ. Conclusion

ZigBee wireless data transmission is stable, reliable and convenient. Low installation cost, easy

maintaining, no need to upgrade, no need to rent the public internet, also do not need huge operation

cost. This solution is the best one for modern data acquisition and remote transmission system.