Solar panel power calculation method

1.0 Introduction

Photovoltaic systems vary in scale and application. For example, the scale of the system is very large, ranging from 0.3 to 2W solar garden lights to MW solar photovoltaic power plants. Its application forms are also varied and can be widely used in many fields such as home, transportation, communications, and space applications. Although the PV system is of different sizes, its composition and working principle are basically the same. This article will briefly introduce the structure of the photovoltaic system and focus on its power calculation method.

2.0 PV system composition

Figure 1 is a schematic diagram of a typical photovoltaic system that supplies DC loads.

Several major components in a photovoltaic system:

1. Photovoltaic module: It is composed of solar modules (also called photovoltaic modules) that are connected in series and in parallel according to system requirements. It converts solar energy into electrical energy under the irradiation of sunlight. It is the core component of a solar photovoltaic system.

2. Storage battery: The energy generated by the solar cell module is stored. When the light is insufficient or at night, or the load demand is greater than the amount of electricity generated by the solar cell module, the stored energy is released to meet the energy demand of the load. It is a solar photovoltaic system. Energy storage components. At present, the solar photovoltaic system is commonly used lead-acid batteries, for the higher requirements of the system, usually used deep-discharge valve-regulated sealed lead-acid batteries, deep-discharge liquid-absorbing lead-acid batteries.

3. Controller: It defines and controls the charging and discharging conditions of the battery, and controls the solar module and the battery to the power output of the load according to the power demand of the load. It is the core control part of the entire system. With the development of the solar photovoltaic industry, controllers have become more and more powerful. There is a trend to integrate traditional control parts, inverters, and monitoring systems. For example, the AES SPP and SMD series controllers integrate the above three. Functionality.

4. Inverter: In a solar photovoltaic power supply system, if there is an AC load, an inverter device is used to convert the direct current generated by the solar cell module or the DC discharged by the battery into the alternating current required by the load.

The basic working principle of the solar photovoltaic power supply system is that under the irradiation of sunlight, the power generated by the solar cell module is charged by the controller to charge the battery or directly to the load when the load demand is met, if the sunshine is insufficient or at night Then, the battery supplies the DC load under the control of the controller. For the photovoltaic system containing the AC load, an inverter needs to be added to convert the DC power into AC power. Photovoltaic systems have many applications, but their basic principles are similar.

3.0 solar cell module power calculation method

Silicon solar panel capacity refers to flat panel solar panel power generation WP. The amount of solar power depends on the power H(WH) that can be consumed by the load for 24h. The power consumed by the load rated power and the load for 24h determines the capacity P(AH) consumed by the load for 24h, taking into account the average daily sunshine. Calculate the operating current IP(A) of the solar arrays based on the number and impact of rainy days.

From the load rated power supply, select the nominal voltage of the battery, determine the battery serial number and battery float voltage VF (V) from the nominal voltage of the battery, and then consider the temperature rise voltage VT (v) caused by the temperature rise of the solar battery and The influence of the voltage drop VD(V) of the reverse-charged diode PN junction can calculate the working voltage VP(V) of the solar array, and the working power source IP(A) and operating voltage VP(V) of the solar array. The power generation power WPW of the flat panel solar panel can be determined to design the solar panel capacity. The designed capacity WP and the solar cell array operating voltage VP determine the serial number and parallel group number of the silicon battery flat panel.

The specific design steps of the solar array are as follows:

1. Calculate the load 24h consumption capacity P.

P=H/V

H—Power consumed by the load for 24 hours (WH, watt hour)

V - load rated power

2. Select the daily sunshine hours T(H).

3. Calculate the solar array operating current.

IP=P(1+Q)/T

Q——According to the rainy period excess coefficient, Q=0.21~1.00

4. Determine the battery float voltage VF.

The cell float voltages of the cadmium-nickel (GN) and lead-acid (CS) batteries are 1.4-1.6V and 2.2V, respectively.

5. Solar cell temperature compensation voltage VT.

VT=2.1/430(T-25)VF

6. Calculate the solar cell array operating voltage VP.

VP=VF+VD+VT

Where VD = 0.5 to 0.7

About equal to VF

7. Solar array output power WP, flat panel solar panels.

WP=IP×VP

8. According to the VP, WP in the silicon battery flat panel assembly series table, determine the number of serial blocks and the number of parallel groups of the standard specifications.

In addition, the AC system or grid-connected system must also consider inverter conversion efficiency and other power losses.

4.0 examples

The following uses 100W output power and uses five hours per day as an example to introduce the calculation method:

1. First calculate the watt-hours consumed per day (including inverter losses): If the inverter conversion efficiency is 90%, when the output power is 100W, the actual output power should be 100W/90 %=111W; if used for 5 hours per day, the power consumption is 111W*5 hours=555Wh.

2. Calculate solar panels:

According to the daily sunshine duration of 6 hours, taking into account the charging efficiency and the loss during the charging process, the output power of the solar panel should be 555Wh/6h/70%=130W. 70% of this is the actual power used by the solar panel during the charging process. (The author WeChat public account: Photovoltaic experience network)