I have always been very interested in solar power generation. Through the internet and various channels, I studied and researched the feasibility and calculated the relevant parameters. Finally, with the support of my family, I decided to install a rooftop power station.

I emphasized to the master making the solar panel brackets that good materials should be used, able to withstand the level of a level 12 typhoon, so the stainless steel materials used had to be thickened and ordered.

Overall view, there are a total of 18 pieces of 200W monocrystalline solar panels, each panel can be independently disassembled for future maintenance.

Before installation, it is necessary to test whether the screw positions of each panel are correct. The screws are also made of stainless steel, ensuring longevity without rust issues.http://img.pconline.com.cn/images/upload/upc/tx/itbbs/1311/19/c9/28770341_1384828601923_1024x1024.jpg

The completed bracket overall view, it requires four people to lift it, very heavy.

The stainless steel pillar base is also made of stainless steel, and the drilling is very difficult, a total of six pillars.

This is the cabinet, a total of three layers. The top layer holds the inverter and solar controller, circuit breakers, and other switch devices; the second and third layers are for battery placement, accommodating 8 pieces of 12V 200AH batteries.

12V 200AH solar specialized deep cycle batteries, very heavy, carrying them to the 6th floor nearly broke my hands.

Reserve the opening positions, considering instruments, wiring, switch buttons, fans, etc.

Completion effect diagram.

The cabinet has output AC voltage, output AC current, battery voltage, cabinet temperature, and corresponding buttons, fan switches, outdoor LED light tube switches, etc., and there are two reserved switches.

18 solar panels are divided into two groups, one group is 2 strings of 4 in parallel, and the other group is 2 strings of 5 in parallel, connected to 60A solar controllers; the following is a DIY junction box that can intuitively see the current solar power generation situation. The red is the voltage, the blue is the current. The red voltage can reach around 55 under load, and under no load, it can reach a maximum of around 90 (in November sunlight). The maximum blue current of one group can reach around 23A (10 panels).The internal situation of the cabinet, the black one is a 6000W inverter (DC main supply type, can fully utilize solar power generation, when the battery has no power, it will directly switch to mains power, and when the battery is fully charged, it will automatically switch back to inverter power supply, the switch will be seamless, without any feeling).

Two 60A solar controllers have very detailed real-time data viewing functions, allowing you to understand the current battery level, temperature, charging current, battery voltage, power generation ampere-hours, and power consumption ampere-hours, which is very useful. There is an 8A switching power supply, mainly used to provide 12V DC power for instruments, cabinet fans, and outdoor LED light tubes. Several two-phase and three-phase sockets are for testing.

Each layer has a cooling fan, currently keeping the temperature below 30 degrees.

Dual power switch for switching.

Panoramic view, considering the water leakage problem at the seams between the solar panels, aluminum foil fiber tape was used, which is sun-proof, waterproof, and not easy to tear, with strong adhesion.

There is a water tank at the bottom, which can be used to water plants on rainy days.

The overall structure is quite solid and should withstand typhoons.

Each panel is connected using MC4 specialized connectors, making maintenance easy, and the wiring uses iron wire troughs for durability. Below the trough, there are four waterproof LED light tubes that are very bright at night.

I had the master make a ladder for easy climbing and maintenance.

After a while, the surface of the solar panels will accumulate dust, affecting power generation efficiency, so the panels need to be cleaned regularly. Below is the cleaning tool for the solar panels (used for washing cars, with a water gun).

After cleaning, the panels look brand new (it is best to clean when the sun is about to set, as the panels have cooled down and are not generating power).

Two small panels used for solar emergency lights, very convenient, used them for solar angle testing.Solar water heater, used for several years, was where I first discovered the benefits of solar energy.This is a satellite antenna, another hobby.

Installation of the lightning protection device.DC lightning protection device, one for each solar panel (best installed after the fuse and circuit breaker), ground wire connected to the cabinet (it is required to connect to the nearest steel structure).

AC lightning protection device (the yellow heat shrink tube in the picture is the ground wire, the interface has not been welded by the master yet, just simply resting on the steel frame).

Solar DC ammeter modified to be powered by solar batteries (the DC ammeter requires at least DC 4V or more voltage, up to 28V, so it cannot be powered by 48V solar batteries and needs two small panels for power supply. Using a switching power supply at night without any current passing is also a waste, and most importantly, using one switching power supply for two DC ammeters can easily burn them, so they must be powered separately to be stable)..The solar panel is only the size of a palm, very cute (dimensions: 130×190×15MM output voltage/current: 9V, 260MA power: 2W-2.3W).

Specifically made a stainless steel bracket to support two small panels, DIY clamp fixed on the handrail.Installed wireless video surveillance cameras and network cameras to achieve real-time monitoring of solar power generation via TV, handheld 2.4G wireless video receiving devices, and computers and mobile phones.

Handheld 2.4G wireless audio-visual receiving device, no need to turn on the TV, quick and convenient.

Hikvision C2 network camera, supports WIFI, allowing remote viewing on computers and mobile phones.

DIY camera bracket made of aluminum alloy.

The camera bracket is directly fixed on the cabinet, and it can be pushed back when the cabinet needs to be opened.

It is possible to remotely view power generation status on a computer, and a dedicated software can also be installed on a mobile phone for viewing, without the need to purchase a network domain name, and the configuration is very simple.

Replace the PC-level dual power automatic switch and install a remote control circuit breaker.The secondary remote control circuit breaker (with distribution box) was decided to only use internal components for system integration and aesthetics.The two white ones are 3000 meters ultra-long-distance dual-key remote controls, which can easily control the circuit breaker in the stainless steel cabinet on the sixth floor from the first floor.The PC-level dual power automatic switch has a switching time of less than 80MS, which will not cause power outage for daily appliances (the actual test shows that LED lights will flicker, but appliances like TVs, washing machines, and refrigerators will not lose power).

Fix the PC-level ATS switch and remote control circuit breaker on the electrician’s wooden board (phenolic laminated paper board), then fix it inside the distribution cabinet, and tidy up the wires to complete the image.

You can freely switch between solar energy and mains electricity based on power consumption.

Ultra-long-distance circuit breaker remote control switch.

Install temperature-sensitive cooling fans, rail voltmeters, and expand the solar power generation system from 3600W to 6000W.12V temperature control switch, currently set to start at 25 degrees Celsius.

Rail voltage meter, ammeter, and power meter.

Cooling fan, very useful on hot days,for cooling the inverter.

Currently, there are 18 pieces of 200W monocrystalline solar panels, with an installed capacity of 3600W, expanded to a 30-piece 6000W system (three input groups, consisting of 2 strings of 4 in parallel, 2 strings of 5 in parallel, and 2 strings of 6 in parallel, all using 60A solar controllers).

DIY lead-acid battery monitor. Using multiple batteries in series inevitably encounters consistency issues. To extend the life of lead-acid batteries, a 100V DC voltmeter with upper and lower limit flashing and sound alarms is selected. It can not only intuitively detect the voltage status of each battery in real-time but also provide warning prompts for batteries reaching critical voltage. Each voltmeter corresponds to a battery placement position.

It is best to use a pulse charger for maintenance after the batteries have been used for a period to extend their lifespan (to prepare for replacing lithium iron phosphate batteries).

All equipment (via network relay, DIY Arduino mechanical switch to mimic finger action for remote control of the white switch).

Main mechanical structure diagram, driven by servos.

Test and verify the program wiring on the breadboard.

Remote control of Arduino switch video via mobile phone.

Installation effect diagram.

Inverter version of Arduino remote control switch.

Considering the miniaturization of the switch, a Digispark kickstarter micro Arduino development board ATTINY85 was used.

Three-position boat switch on the inverter being operated (only the normal start position I and the shutdown position are used).

Remote control of the photovoltaic inverter can be realized on a computer or mobile phone, switching between mains and photovoltaic power, and the remote control software can set timing for turning on and off, achieving unattended operation.

DIY network ammeter (transmits data such as voltage, temperature, humidity over the network, and can also be viewed directly on a mobile phone or computer via a WEB page).

Server hostClient host (can be placed in the living room, office, or anywhere with internet access, allowing real-time viewing of current solar usage, with sound and light alarms, without having to open video surveillance to check).

Through Arduino, it is convenient to collect sensor data and transmit it over the network, and then configure dynamic domain names through routers, making it easy to view current solar power generation status on various terminals.

Replacing lithium iron phosphate battery packsthe selected battery is a 48V 240Ah lithium iron phosphate battery. This battery can theoretically store 12.3 degrees of electricity, has no battery memory effect, can be used down to 0%, continuous discharge current of 200A, instantaneous 300A, and has a long lifespan (theoretical design life of 8 years).

The battery case can be customized in size, just fitting into the battery cabinet. It uses a 16Ah large single battery (16 in series, 2 in parallel), customized protection board, equipped with a coulomb meter (automotive BMS management system, can directly view remaining power, voltage, battery temperature, current, and other information),connected to the battery using an RS232 interface (the battery end uses aviation connectors, eight-wire network cables only use four wires).

The battery interface is easy to install, apart from the positive and negative terminals, there is also a coulomb meter aviation connector for direct replacement of ordinary lead-acid batteries, and there is a power switch to control the current cutoff, which is very practical.

A very useful coulomb meter, especially suitable for photovoltaic energy storage scenarios, can intuitively show various information. Current information is also very practical; positive current indicates that the current loss is greater than the charging current, negative current indicates that the charging current is greater than the usage loss, which can be understood as the battery is charging, and zero indicates that there is no current usage or that usage and charging offset each other.

A good smart wireless current, voltage, power bidirectional meter.

The off-grid photovoltaic system is now considered to be completed (from design, collection, energy storage to inversion, power switching, data remote transmission, remote control), hoping to share some experience with everyone.

Attached are design drawings and some materials (note that the best angle for solar panels in Guangzhou is 16.13 degrees, and Huizhou has a similar latitude; I finally set it to 18.81 degrees). The best tilt angle is generally related to the local latitude, which can vary slightly based on specific conditions, the following can be used for reference:

City Latitude θ (°) Best Tilt Angle (°)

　Harbin 45.68 θ+3　　Changchun 43.9 θ+1　　Shenyang 41.77 θ+1　　Beijing 39.8 θ+4　　Tianjin 39.1 θ+5　　Nanjing 32.0 θ+5　　Taiyuan 37.78 θ+5　　Zhengzhou 34.72 θ+7　　Xining 36.75 θ+1　　Lanzhou 36.05 θ+8　　Yinchuan 38.48 θ+2　　Xian 34.3 θ+14　　Shanghai 31.17 θ+3　　Changsha 28.2 θ+6　　Guangzhou 23.13 θ-7　　Haikou 20.03 θ+12　　Nanning 22.82 θ+5　　Chengdu 30.67 θ+2　　Guiyang 26.58 θ+8　　Kunming 25.02 θ-8　　Lhasa 29.7 θ-8　　Hefei 31.85 θ+9　　Hangzhou 30.23 θ+3　　Nanchang 28.67 θ+2　　Fuzhou 26.08 θ+4　　Jinan 36.68 θ+6　

In general cases, you can take the latitude directly, or add 5, or 10 directly.

The following are design drawings:

Finally, in summary, a total of 18 pieces of 200W monocrystalline solar panels were used for a 3600W system, with 4 pieces of 12V200AH batteries connected in series to form 48V. The inverter is 48V 6000W, capable of supporting three 2-horsepower air conditioners simultaneously, powering all household electricity, as well as network, monitoring, automatic water pumps, and corridor lights, meeting daily living needs. It should be noted that the inverter can adjust the charging current; if you do not want to use mains power, you can set this current to zero, allowing for more fully utilizing solar power generation.

4 batteries can meet all-night power needs, and by 7 or 8 o’clock the next morning, when the sun rises, solar power can be used again to charge. No need to spend a penny on electricity bills. 4 batteries are still a bit insufficient; considering the fast discharge (two groups of batteries are much more stable in voltage than one group) and support for high-power appliances, I have now increased to 8 batteries, totaling 200 * 8 = 1600AH (because the inverter has a battery protection mechanism, a maximum of 70% can be used, which is approximately 11.2 degrees of electricity). This way, it can be used for about one day without sunlight (each household’s electricity usage varies, which can be adjusted according to one’s own household usage).

Now, after a few days, with 4 batteries, the maximum power generation in a day is over 11 degrees, because there are not enough batteries to charge, and I cannot use that much electricity (8 batteries are still being tested). The entire solar power generation system cost nearly 50,000 yuan, of which the stainless steel brackets and cabinet wiring cost 16,000, and the batteries are too expensive. I did a lot of preliminary research and study before taking action. Overall, I am still very satisfied with solar energy and hope that battery technology can make breakthroughs in the future, allowing for more storage and durability. I believe that solar energy will become more popular in the future.

Source: Pacific Computer Network

Author:liunanqing

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