An analysis of PV power generation and attenuation of photovoltaic modules

Polaris solar PV net news: 1, introduction

Due to the global energy crisis, resource-rich new sources of energy, such as wind and solar power gradually occupies an important position. World Solar photovoltaic power generation system maintains sustained rapid growth in recent years, by 2012 the world PV cumulative installed capacity has reached 102GW[1] and become the fastest-growing electricity generation technology, photovoltaic power in more than 20 countries to achieve parity.

As the core component of photovoltaic modules technical breakthroughs, and constant improvement in the efficiency, cost per kilowatt of photovoltaic power generation system will gradually approach the traditional thermal power generation cost, simultaneously with the development of energy storage technologies, and photovoltaic systems due to its system free, low threshold installation requirements will be applied more generally from around the world.

PV system in the market as a whole, grid-connected photovoltaic system at present has an absolute leading position is dependent on the development of grid-connected photovoltaic technologies mature, continuous research and development progress of the corresponding device performance and cost, as well as Governments actively promote the policy.

2, the principle of photovoltaic power generation system

As broadly divided into grid-connected photovoltaic power generation system based on actual application system and individual system [2], due to the large grid-connected systems share application, this article focuses on grid-connected systems electricity production estimates.

Also, due to the different size and condition of the system, grid-connected systems and there are also some systems, this assessment is based on how much electricity large-scale PV power station as a model, and photovoltaic power plant’s environmental conditions are relatively good.

Figure 2-1 block diagram a typical of large power stations generate electricity.

2-1 principles of large-scale power generating diagrams

The entire system consists of photovoltaic array and (straight) composed of streaming transmission, PV array output DC power on after DC lines after the confluence of the inverter into the AC waveform frequency stability rules, and then following a step-up to medium voltage in-place, in the medium voltage AC lines on the confluence of two concentrated booster, and finally connected to the grid for grid-connected.

According to the diagram, usually in property rights installs an effective power meter to measure the PV power plant generating capacity, which is the most accurate statistics. According to the early years of revisions to statistical data analysis of simulation data, can more accurately forecast future capacity.

3, PV power plant generating capacity loss factor analysis [3]

Early in the project more accurate estimates of PV power plant generating capacity, in addition to the structures have a deep understanding of the PV system or major equipment performance parameters must be have a deep understanding. Also, if you want a longer period of electricity when estimates are, you should take full account of the long term effects of environmental factors and plant operation status forecasts.

Analysis of photovoltaic power plant generating capacity estimates for the first year, usually loss factors to consider are as follows:

⑴ the inclined angle sunlight exposure correction;

⑵ component effects of surface dirt and other foreign objects from the light;

Effect of temperature on the photovoltaic module output c;

⑷ PV module’s own decay;

⑸ string component matching losses;

⑹ square shadows between before and after the loss;

⑺ DC transmission line losses;

H inverter efficiency losses;

⑼ local transformer losses;

⑽ AC line losses;

⑾ transformer loss;

⑿ utility power loss;

⒀ downtime losses;

PVSYST is usually used when software-emulated output, without considering the loss of electricity and downtime is to consider other factors, an integrated data.

Analysis after 24 years behind when PV power plant generating capacity, operations management is the most important factor, but poor estimates of, often assumes other factors that you don’t change, just consider the decay of PV modules itself.

4, PV module power of attenuation

In practice, after the PV module manufacturing has been in a State of decay, but is not in the package, see light attenuation is very slow, once after receiving sunlight, decay will dramatically speed up decay after a certain percentage gradually stabilize, as shown in Figure 4-1, the first annual decline curve model diagram:

Figure 4-1 PV modules in the first year the attenuation curve model

Figure 4-1 the first year 3% total attenuation data attenuation from astronergy solar polycrystalline silicon components for 25 years guarantee, which guarantees 25 attenuation is shown in Figure 4-2,

4-2 photovoltaic module decay curves

As can be seen from Figure 4-2 PV module maximum attenuation value is 3% for the first year, followed by 24 year attenuation value is 0.7%.

Due to the initial stages of decay are directly connected with intensity, so that in the first year, on the average light intensity conditions basically renders sharply attenuated in the early, late State progresses smoothly. But, in fact, a solar power station from components start to install grid-connected to finally begin this time span is not certain, metering capacity of time to begin, a component may have a certain ratio of attenuation, in order to reduce the actual and theoretical estimates of error, in addition to time after warranty requirements, General components at the factory, there will be a certain percentage of power deviation, Deviation can cover a portion of the power components due to some human factors in some of the cases where no power attenuation loss.

So in theory calculations, power output rated power the starting point of the simulation can be equated to photovoltaic module factory rated power and linear attenuation attenuation can be regarded as a component within a year.

5, PV electricity production estimates

PV energy output calculations are in fact PV power output in real time with the time integral of the function, as shown in Figure 5-1,

5-1-time curve of PV power schematic drawing

For ease of calculation, usually pictured above is equivalent to the standard light intensity of output power and peak sunshine hours, rectangle, as shown in Figure 5-2,

Figure 5-2 photovoltaic power-time equivalent rectangular drawing

Photovoltaic power plant generating capacity each year equivalent power p ′ x q = peak time Hx365 days of sunshine, with equivalent power p ‘ in the actual day is a fluctuating values calculated under the formula (5-1) said,

The equivalent power p rated installed power Px system efficiency η ′ = (-5-1)

For the purpose of computing 25 years power output of photovoltaic power station, 5-1 can be expressed as 5-2, as follows

Equivalent power p rated average installed power Px component efficiency η ′ = 1x system efficiency η 2 other loss elements (5-2)

Integrated above, PV station years electricity Q= rated installed power Px component average efficiency η 1x system other loss factors integrated efficiency η 2x peak sunshine time Hx365 days, in 25 years term in the, except component average efficiency η 1, other items of product can considered a not variable of constants Q?, is eventually of expression type for PV station years electricity Q=Qx component average efficiency η 1 (type 5-3).

Component average efficiency η 1–(beginning of component proportion rated + percentage components rated capacity at the end)/2

Power deviation deviation can cover a portion of the power components due to some human factors in some of the cases where no power attenuation loss.

So in theory calculations, power output rated power the starting point of the simulation can be equated to photovoltaic module factory rated power and linear attenuation attenuation can be regarded as a component within a year.

To sum up, to chint solar grade polysilicon components Attenuation to ensure, for example, 25 years component average efficiency is shown in the following table:

Table 5-125 component rated capacity changes in the forecast table

Estimation of annual energy output in table 5-225 relation

Such as PVSYST software estimation when PV power plant capacity in the first year, and system efficiency is not considered in power station self power and downtime of both, but it does not affect calculated according to estimates for the first year after 24 years behind estimated generating capacity. According to previous statements, first year generation time estimated by PVSYST, in the Detailedlosses, if Moduleefficiencyloss is set to 1.5%, then calculate the average efficiency of the component 98.5% in the first year, estimated power output for the first year is the second year of 98.12%, to 97.41% in the first year for the third year, fourth year to 96.7% in the first year, followed by example, as can be seen from the second year onwards, Behind the annual estimated generating capacity of approximately 0.7% reduction on the basis of the previous year.

6, summary

According to the above calculation generally draws the following conclusions: in the case of other factors being equal, an attenuation of the PV electricity generation with PV modules are compared. However, the actual operation, component surface cleaning, the failure rate of the device, power management is the main factor affecting the capacity of power stations in the late record loss of power station operation factors influence, then the estimate amending the electricity production has a very important significance.

Original title: an analysis of PV power generation and attenuation of photovoltaic modules

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