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27-28 Solar Peak Sunshine Hours and Resource Partitioning

Author: Source: Datetime: 2016-12-24 18:21:52
Calculation of peak sunshine hours and power generation

It is preferred to distinguish between sunshine hours and sunshine hours

Sunlight time refers to the sunshine during the day from sunrise to sunset exposure time. Sunshine hours refer to the time that a certain day the sun reaches a certain irradiance (usually 120W/m2 measured by the meteorological station) until it is less than this value .Obviously, the sunshine hours is less than the sunshine time.

Under the number of hours. Ie the ratio H / G of the total solar radiation H to the standard irradiance G at the surface (irradiance G = 1000W/m2) Level over a period of time (month or year), sometimes referred to as the equivalent utilization hours. Internationally, solar energy resources are usually divided into three categories:

(1) high-irradiance regions(2000kWh/m2a), such as the United States southwest and sub-Saharan Africa;

(2) in the irradiance region(1700kWh/m2a), , such as most parts of the United States and southern Europe;

③ low-irradiance regions(1100kWh/m2a)   (such as Central Europe, Germany and so on).

China's solar energy resources are listed in Table 2-1.

Table 2-1 Annual peak sunshine hours in China's solar energy belt

grade

resource strip number

 

annual total radiation

/(MJ/m2)

annual total radiation

/(kWh/m2)

average daily dose

/(kWh/m2)

annual peak sunshine hours

/h

richest band

≥6300

≥1750

≥4.8

≥1750

Very rich band

5040~6300

1400~1750

3.8~4.8

1400~1750

more rich band

3780~5040

1050~1400

2.9~3.8

1050~1400

general

<3780

<1050

>2.9

<1050


We can obtain the total solar radiation from the meteorological department, and then use the method described in section 1.3 of this book or directly use software such as Retscreen to calculate the total solar radiation on the oblique plane of the fixed inclination square, the result should Be compared with the horizontal plane. Out of 10% -15%.

A photovoltaic power generation system (power plant) before the formal project, the PV array power generation must be predicted. This is a pre-feasibility or feasibility study of the indispensable. Because investors to invest in the construction of photovoltaic power generation projects in an urgent need to know its power generation in order to understand the project after the implementation of the expected level of profitability and the potential reduction of CO2 and other economic and social benefits. Of course, the factors that affect the cost of power generation or the feed-in tariff include a series of factors such as local solar energy resource, PV system efficiency and power generation, system reliability and grid quality, initial investment scale, operation and maintenance cost, loan ratio and interest rate tax. One of the most important indicators. If a period of time is set to year, the annual power generation of PV system (power plant) is estimated as:

EAC = KP0Yr


Where: EAC           PV system annual power generation (AC), kWh;
           P0
             PV array rated DC power kW;
          
Yr              Solar annual peak sunshine hours, h;
          
K               Integrated System Efficiency

There are many influence factors on the K value, including the influence of PV module string, parallel matching loss, temperature rise loss, component performance attenuation, line loss, shadowing and dust pollution loss. Please refer to Chapter 3 of this book solar photovoltaic power generation system design principles and methods of 3.1 analysis of the parameters of the detailed analysis. For a glance, give a list 2-2. As can be seen from the table, the optimum K value is 0.84. Engineering design, K value of the grasp and practical experience. At present, for domestic PV power generation, K value is 60% ~ 70% for stand-alone PV power plant, 80% ~ 85% for centralized grid-connected PV power plant, 75% ~ 80% for distributed grid- .

Table 2-2 Factors that affect the efficiency of the integrated system

affect the performance parameters

description and influencing factors

optimal index

calculated

incident sunlight

occlusion loss

photovoltaic arrays are directly and peripherally obscured

2.0%

0.980

reflection attenuation

due to the different angles of incidence caused

0.2%

0.998

 

dust and supplies

local conditions and maintenance levels

1.0%

0.990

spectral deviation

deviation from the power deviation of the AM1.5 spectrum

0.9%

0.991

measurement error

error of total radiation table ±0.5%

0

1.000

 

DC side

loss of PV modules

crystalline silicon 0.44%/, amorphous silicon 0.22%/

NOCT45/

0.956

performance degradation of PV modules

crystalline silicon 0.5%/year, amorphous silicon 1%/year

0.50%

0.995

DC circuit loss

<3% (including DC equipment and cables)

2.00%

0.980

series and parallel losses

inconsistent electrical performance of components (barrel effect)

1.00%

0.990

loss of nonlinearity

change in the light intensity is non-linear

0.20%

0.998

MPPT tracking error

tracking method, grid / weather conditions

0.50%

0.995

measurement error

electrical parameter measurement error of ±0.5%

0

1.000

AC side

inverter Efficiency

inverter Design, Devices and Fabrication

98%

0.980

transformer efficiency

inverter materials, design and recycling

99%

0.990

AC line loss

including other AC equipment and cables

0.5%

0.995

measurement error

electrical Parameters Vehicle Error ±0.5%

0

1.000

 

fault and maintenance, itself / grid

depends on the plant equipment, design and installation

1.0%

0.990

 

optimum K value (minimum one year cycle)

 

0.840


In the evaluation of PV power system performance, the performance ratio (Performance Ratio, PR) is one of the main indicators. It is defined as the ratio of the amount of photovoltaic power generated to the amount of solar energy resources, that is;


Performance ratio = full power hours / peak sunshine hours = actual AC power generation / ideal DC power, expressed as:

Calculate Solar Power Generation System Performance
The performance ratio PR is equivalent to the integrated system efficiency K in comparison with the previous generation formula (2-1). As the reflected factors include: the electrical efficiency of the system (component series and parallel losses, inverter efficiency, transformer efficiency and other equipment efficiency, temperature loss, line loss, etc.), component degradation, occlusion, optical reflection loss error, measurement Error, fault conditions and operation and maintenance level, no doubt the performance ratio is the most important PV system evaluation index. This index eliminates the geographical and solar energy resource differences, more objective reflection of the PV system's own performance and quality.

In addition, the temperature and spectral correction, excluding these two differences can be called after the standard performance ratio. Will be divided by the ratio of performance area occupied by the unit area ratio, which is not only good quality, and the area is also excellent design.
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