Calculation method of solar home system configuration

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The calculation principle of solar power generation system configuration is the principle of conservation of energy: that is, the electricity generated by solar energy is equal to the power consumption of the load. And consider the loss of the system

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The calculation principle of solar power generation system configuration is the principle of conservation of energy: that is, the electricity generated by solar energy is equal to the power consumption of the load. And consider the loss of the system

step:

1. Determine the power consumption of the load for a day:

Q1=P*T

Q1 is the electric quantity, the unit is WH; P is the power, the unit is W; T is the time, the unit is H

2. Estimate the energy loss of the system:

In a small AC system, the use efficiency of the inverter is 80%; a large power generation system can reach 90%; because the energy loss of the solar controller is very small, it can be ignored here. Then the solar panel needs to generate at least Q2=Q1/η in a day to reach equilibrium.

3. Calculate battery capacity:

The capacity of the battery is related to the backup time of the consumption. Also according to the law of conservation of energy, for lead-acid batteries, since deep discharge is very harmful to the battery life, it is generally only placed to 80% of the full capacity of the battery. In addition, because the battery is charged The battery is charged in a floating state in the later period, so there should be a 10% battery margin to make better use of the electricity generated by the solar battery (this needs to be determined according to the customer’s electricity use time, if it is to generate electricity during the day and use it at night) There should be a 10% margin. If it is used for daytime power generation during the day, there is no need to leave a power generation margin. Therefore, in general, the system that generates power during the day and discharges at night has only 70% of the full capacity of the battery. The discharge capacity of the battery can reach 80% of the full capacity of the system. The dischargeable capacity of the battery must meet the power consumption during continuous backup time; for systems with backup time requirements, the median value is taken.) So C*U *δ=Q2*d; so C=Q2*d/(V*δ)

C is the battery capacity, the unit is A.H; U is the system voltage, the unit is V; δ the battery discharge capacity, generally 70% to 80%; d is the number of backup days.

4. Calculation of solar panel power:

In addition to the power generation capacity of the solar cell, the power generation capacity for the battery must be added to the power generation capacity of the load. Therefore, for the system with a long backup time, sufficient power generation margin should be reserved for charging the battery. The size of the margin depends on how fast the battery is fully charged. According to the principle that the power generation is equal to the power consumption of the load plus the power charged into the battery, P3*T2=Q2+Q3; P3 is the power of the solar panel, T2 is the effective power generation hours per day, and Q2 is the power consumption of the load plus System loss, Q3 is the charge into the battery. The size of Q3 depends on the situation. For the case of no backup days, the value of Q3 is the battery's self-discharge capacity, which is generally 1% to 3% of the rated capacity * rated voltage; for the case of backup time requirements, it can be taken as the sun About 20% of the solar panel's power generation can be reduced to 10% in places where love is the mainstay of the year, and it can be appropriately increased to about 30% in places where there are often cloudy and rainy days.

5. The choice of solar controller

The rated current of solar control should not be less than the maximum current emitted by the solar current panel, so as to avoid damage to the device or loss of power. For places with good sunshine, it can be 120% of the maximum output current of the battery panel, and for places with bad sunshine, it can be appropriately reduced.

6. Selection of AC system inverter

A square-wave output inverter can be selected for systems with a household load of less than 300W. The reason is that the load of electrical appliances that generally require sine waves usually exceeds 300W. It can be specially configured for special requirements of customers (note that it is impossible to use a vehicle-mounted square wave inverter for long-term use of the load)

For systems above 600W, sine wave output inverters should be used as the main reason. The reason is that inductive loads similar to refrigerators need to use sine wave voltage waveforms. The selection of inverter power is generally 120% to 150% of the rated power of the system. Adjust the size of its power according to the needs of customers. System example:

Taking Africa as an example, the load and power consumption time of a user is as follows: energy-saving lamps 30W, 4 lamps are used for 6 hours a day on average; a LCD desktop computer (100W) is used for 8 hours a day on average; a 90L refrigerator is used for 24 hours on average Electricity is 0.8KW.h/24h. A 150W liquid display TV set is used for an average of 5 hours a day; the backup time is 3 days.

1. Calculation of load power consumption:

First, calculate the total power consumption in a day as Q1=30*4*6+100*8+800+150*5=3070W.h; the maximum power consumption is P1=30*4+100+500+150=870W . Since it is an AC load, assuming that the efficiency of a general industrial frequency inverter is 0.8, it is equivalent to the total power consumption of one day as Q2=Q1/0.8=3070/0.8=3837W.h.

2. Calculation of battery:

The total power consumption of the 3-day backup time is Q2*3=3837*3=11511W.h; the discharge coefficient of the battery is taken as 0.76, and the cell voltage is taken as 12V. According to the law of conservation of energy 11511=C*12*0.75; C=11511/(12*0.76)=1262A.H. Taking into account that solar cells can also generate electricity on cloudy days, the total capacity is 1200A.H. 6 monomers of 200A.H/12V form 2 strings and 3 and form a 24V battery pack.

3. Calculation of solar panel power:

Taking the sunny areas of Africa as an example, the effective daily power generation time of solar cells is 6 hours, and the battery capacity is required to be more than 90% in 10 days under sunny conditions after the battery is used up. Then the battery board's remaining capacity for rechargeable batteries per day is Q3=11511/10≈1150W.H. The daily electricity generated by the battery board is Q3+Q2=3837+1150=4987W.H, so the power of the battery board is P3=4987/6=831W; it can be 6 pieces of 140W/18V battery boards.

4. The choice of solar controller

Since the solar system is selected as a 24V system, the maximum power generation current Imax=831/24≈35A, which is less than 0.25C of the total battery capacity. So choose 35A/24V solar controller

5. The choice of inverter

Because the refrigerator is an inductive load and the maximum power of the total load is 870W, a 1000W/24V pure sine wave output inverter is selected.

If this system has no backup time, the configuration is: total battery capacity C=3837/(12*0.8)≈400A.H. Two 200A.h batteries can be used to form a series 24V system; the power of solar panels is P=3837/6≈640W, and two 160W/18V panels can be used.

step:

1. Determine the power consumption of the load for a day:

Q1=P*T

Q1 is the electric quantity, the unit is WH; P is the power, the unit is W; T is the time, the unit is H

2. Estimate the energy loss of the system:

In a small AC system, the use efficiency of the inverter is 80%; a large power generation system can reach 90%; because the energy loss of the solar controller is very small, it can be ignored here. Then the solar panel needs to generate at least Q2=Q1/η in a day to reach equilibrium.

3. Calculate battery capacity:

The capacity of the battery is related to the backup time of the consumption. Also according to the law of conservation of energy, for lead-acid batteries, since deep discharge is very harmful to the battery life, it is generally only placed to 80% of the full capacity of the battery. In addition, because the battery is charged The battery is charged in a floating state in the later period, so there should be a 10% battery margin to make better use of the electricity generated by the solar battery (this needs to be determined according to the customer’s electricity use time, if it is to generate electricity during the day and use it at night) There should be a 10% margin. If it is used for daytime power generation during the day, there is no need to leave a power generation margin. Therefore, in general, the system that generates power during the day and discharges at night has only 70% of the full capacity of the battery. The discharge capacity of the battery can reach 80% of the full capacity of the system. The dischargeable capacity of the battery must meet the power consumption during continuous backup time; for systems with backup time requirements, the median value is taken.) So C*U *δ=Q2*d; so C=Q2*d/(V*δ)

C is the battery capacity, the unit is A.H; U is the system voltage, the unit is V; δ the battery discharge capacity, generally 70% to 80%; d is the number of backup days.

4. Calculation of solar panel power:

In addition to the power generation capacity of the solar cell, the power generation capacity for the battery must be added to the power generation capacity of the load. Therefore, for the system with a long backup time, sufficient power generation margin should be reserved for charging the battery. The size of the margin depends on how fast the battery is fully charged. According to the principle that the power generation is equal to the power consumption of the load plus the power charged into the battery, P3*T2=Q2+Q3; P3 is the power of the solar panel, T2 is the effective power generation hours per day, and Q2 is the power consumption of the load plus System loss, Q3 is the charge into the battery. The size of Q3 depends on the situation. For the case of no backup days, the value of Q3 is the battery's self-discharge capacity, which is generally 1% to 3% of the rated capacity * rated voltage; for the case of backup time requirements, it can be taken as the sun About 20% of the solar panel's power generation can be reduced to 10% in places where love is the mainstay of the year, and it can be appropriately increased to about 30% in places where there are often cloudy and rainy days.

5. The choice of solar controller

The rated current of solar control should not be less than the maximum current emitted by the solar current panel, so as to avoid damage to the device or loss of power. For places with good sunshine, it can be 120% of the maximum output current of the battery panel, and for places with bad sunshine, it can be appropriately reduced.

6. Selection of AC system inverter

A square-wave output inverter can be selected for systems with a household load of less than 300W. The reason is that the load of electrical appliances that generally require sine waves usually exceeds 300W. It can be specially configured for special requirements of customers (note that it is impossible to use a vehicle-mounted square wave inverter for long-term use of the load)

For systems above 600W, sine wave output inverters should be used as the main reason. The reason is that inductive loads similar to refrigerators need to use sine wave voltage waveforms. The selection of inverter power is generally 120% to 150% of the rated power of the system. Adjust the size of its power according to the needs of customers. System example:

Taking Africa as an example, the load and power consumption time of a user is as follows: energy-saving lamps 30W, 4 lamps are used for 6 hours a day on average; a LCD desktop computer (100W) is used for 8 hours a day on average; a 90L refrigerator is used for 24 hours on average Electricity is 0.8KW.h/24h. A 150W liquid display TV set is used for an average of 5 hours a day; the backup time is 3 days.

1. Calculation of load power consumption:

First, calculate the total power consumption in a day as Q1=30*4*6+100*8+800+150*5=3070W.h; the maximum power consumption is P1=30*4+100+500+150=870W . Since it is an AC load, assuming that the efficiency of a general industrial frequency inverter is 0.8, it is equivalent to the total power consumption of one day as Q2=Q1/0.8=3070/0.8=3837W.h.

2. Calculation of battery:

The total power consumption of the 3-day backup time is Q2*3=3837*3=11511W.h; the discharge coefficient of the battery is taken as 0.76, and the cell voltage is taken as 12V. According to the law of conservation of energy 11511=C*12*0.75; C=11511/(12*0.76)=1262A.H. Taking into account that solar cells can also generate electricity on cloudy days, the total capacity is 1200A.H. 6 monomers of 200A.H/12V form 2 strings and 3 and form a 24V battery pack.

3. Calculation of solar panel power:

Taking the sunny areas of Africa as an example, the effective daily power generation time of solar cells is 6 hours, and the battery capacity is required to be more than 90% in 10 days under sunny conditions after the battery is used up. Then the battery board's remaining capacity for rechargeable batteries per day is Q3=11511/10≈1150W.H. The daily electricity generated by the battery board is Q3+Q2=3837+1150=4987W.H, so the power of the battery board is P3=4987/6=831W; it can be 6 pieces of 140W/18V battery boards.

4. The choice of solar controller

Since the solar system is selected as a 24V system, the maximum power generation current Imax=831/24≈35A, which is less than 0.25C of the total battery capacity. So choose 35A/24V solar controller

5. The choice of inverter

Because the refrigerator is an inductive load and the maximum power of the total load is 870W, a 1000W/24V pure sine wave output inverter is selected.

If this system has no backup time, the configuration is: total battery capacity C=3837/(12*0.8)≈400A.H. Two 200A.h batteries can be used to form a series 24V system; the power of solar panels is P=3837/6≈640W, and two 160W/18V panels can be used.