درس تبدیل مستقیم انرژی

2

I L : Light current I D : Diode current I SH : Shunt current k: Boltzmann constant N S : number of cells in series q: electronic charge n: ideality factor of the diode 3

Ref: reference Incident irradiation : 1000 w/m 2 temperature: 25 o C Air mass ratio: 1.5 Short circuit current condition Open circuit voltage condition 00 4

Maximum power condition: ≈ 0 5

Temperature coefficient of short circuit current Temperature coefficient of open circuit voltage Temperature coefficient of maximum power point Temperature dependence 6

Messenger and Ventre (2004) For cells with a significant slope at nonconcentrating radiation levels the slope is found to decrease (and thus the shunt resistance increase) as the radiation level decreases (DeSoto et. al, 2006) 7

Real maximum power point calculation 8

For many modules, μ I,sc is small. which indirectly results in a value of dl mp /dT of approximately zero and dV mp /dT to be approximately equal to dV oc /dT: 9

Wind speed efficiency of the module in converting Incident radiation into electrical energy 0 The loss coefficient U L will include losses by convection and radiation from top and bottom and by conduction through any mounting framework that may be present, all to the ambient temperature T a. 10

11

With an incident solar radiation of 1000 W/m 2 the cell efficiency is: 65.2/(0.633×1000) =0.103 or 10.3% 12

The cell efficiency is then 35.5/(0.633×648.3)=0.086,or 8.6%. 13

pyranometer 14

Sunshine recorder Campbell–Stokes recorder 15 The Campbell–Stokes recorder (sometimes called a Stokes sphere) is a kind of sunshine recorder. It was invented by John Francis Campbell in 1853 and modified in 1879 by Sir George Gabriel Stokes.

16

The Blake-Larsen Sun Recorder 17 The present version of the Blake Larsen Sun Recorder is the result of a long collaboration between Alan Blake in Cornwall UK and Ole Jul Larsen in Denmark.

pyrheliometer Hukseflux,Hukseflux, Kipp & Zonen, Eplab and EKOKipp & ZonenEplabEKO 18

19

20

inverters Inverters, convert DC current into AC current allowing us to use these renewable energy sources for powering our homes and businesses. 21

22

23

Traditional String Inverters: Are more than sufficient for your energy needs in most cases Are less expensive than microinverters Can connect to third party monitoring systems Convert DC to AC electricity using a large centralized unit If one panel isn't performing due to shading or another performance issue, the entire energy output of your system will be affected The string inverter accepts DC power from a “string” of many solar panels wired to a large single inverter. So, in the string approach, there is a single large inverter producing the AC power for all of the solar panels. 24

25

Microinverters: Are great if your roof has shading issues Produce 10-25% more energy than traditional inverters Convert DC to AC electricity at the solar panel level instead of a centralized unit Safer since they don't have live DC wires connected to a centralized unit Connect to a monitoring system and allow monitoring at the module level Are modular so they allow you to increase the size of your solar panel system as your energy needs increase If one panel isn't performing correctly or is shaded for a period of time during the day, the entire energy output of your system will not be affected The micro inverter is a small inverter that converts power from a single solar panel. In the micro approach, there is small inverter for every panel on the roof. 26

27

28

29

A charge controller, charge regulator or battery regulator limits the rate at which electric current is added to or drawn from electric batteries. It prevents overcharging and may prevent against overvoltage, which can reduce battery performance or lifespan, and may pose a safety risk. Pulse width modulation (PWM) and maximum power point tracker (MPPT) technologies are more electronically sophisticated, adjusting charging rates depending on the battery's level, to allow charging closer to its maximum capacity. charge controller 30

charge controller MPPT: maximum power point tracking 31

32

33

Retscreen 34

35

36

37

For tracking surfaces, the slope β of the array and the incidence angle θ for every hour are determined by equations from Braun and Mitchell (1983). 38

Once tilted irradiance for all hours of the day is computed, the daily total H t is obtained by summing individual hours. η r is the PV module efficiency at reference temperature T r (= 25°C), and β p is the temperature coefficient for module efficiency. T c is related to the mean monthly ambient temperature T a through Evans’ formula: 39

40

The energy delivered by the PV array, E P, is: where S is the area of the array. It has to be reduced by “miscellaneous PV array losses” λ p and “other power conditioning losses” λ c : where E A is the array energy available to the load and the battery. The overall array efficiency η A is defined as: 41

Off-Grid Model 42

D DC : the total DC demand D AC : the total AC demand inverter efficiency Types of loads Positive. For example, the case of a fan connected directly to a PV module; the fan works only when there is solar energy to power. Zero. the case of a constant load, i.e. a load that has the same value throughout the day. This of course requires the use of a battery. Examples are monitoring systems. Negative. In this case all the energy flows through the battery first before being delivered to the load. (all cases not falling into the Positive and Zero categories.) Note that daytime intermittent loads (e.g. refrigerator) also fall into this category. kWh/d 43

D matched is the part of the demand that is met directly by the PV modules whenever there is enough energy produced (Wh). D continuous is the part of the demand that is constant throughout the day (Wh) D battery is the part of the demand that will be met primarily by the battery (Wh) P crit : the critical PV absorption level (W) 44

Utilisability method I tc : A critical radiation level defined as the level of radiation that must be exceeded in order for the PV array to produce more energy than can be immediately used by the constant load The monthly average critical radiation level, defined as the ratio of the critical radiation level to the noon radiation level on a day of the month in which the day’s radiation is the same as the monthly average: the overall array efficiency 45

the monthly average daily utilisability: the sum for a month, over all hours and days, of the radiation incident upon the array that is above the critical level, divided by the monthly radiation: the monthly ratio of radiation in the plane of the array to that on a horizontal surface the ratio for the hour centered at noon of radiation on the tilted surface to that on a horizontal surface for an average day of the month 46

the energy delivered directly to the continuous load the energy delivered to the matched load the energy delivered directly to the load the energy delivered to the battery where r t,n, and r d,n, are the ratio of hourly total to daily total radiation and the ratio of hourly diffuse to daily diffuse radiation, both for the hour centered around solar noon. 47

48