How to Design and Implement a Reliable PV System which could last 30+ years ZAKI IQBAL SENIOR R&D ENGINEER RAK RESEARCH AND INNOVATION CENTER

Content Current trends of Solar PV market Electrical concept in Solar PV Decoding I-V curve Factors affecting the choice of components Summary

Question Why highly skilled PV designers and installers are required for the PV market today ??

Growing installed capacity of PV Answer Growing installed capacity of PV

PV Installed Capacity and Projection

Rise in Global investment in PV Answer Rise in Global investment in PV

Global investment in renewables

Question What could be the consequences of poor PV design/ poor PV installation??

Lack of trust ( investors) Increase in system fail ratio Answer Lack of trust ( investors) Increase in system fail ratio Extra overhead in maintaining the system Fire leading to injury and death Loss of property

How to design and install a reliable PV system?? Question How to design and install a reliable PV system??

Understanding the basics of Photovoltaic electricity Answer Understanding the basics of Photovoltaic electricity

V Voc Vmpp I Isc Impp Voltage Current Electric concepts in Solar PV V ( Voltage) ~ Pressure Voltage V Voc Vmpp Current I (Current) ~ Flow I Isc Impp

Basics of I-V Curve Voc Open circuit Voltage Isc Short circuit Current @ V= 0, I= Imax ~Isc @ I= 0, V= Vmax ~Voc Isc Impp Current [A] Voltage [V] Vmpp Voc STC Conditions @ 1000 W/m2 25ₒC AM 1.5

I-V Curve interpretation Solar Irradiation effects the Current 1000 W/m2 800 W/m2 600 W/m2 400 W/m2 Current [A] Solar irradiation Voltage [V]

I-V Curve interpretation Temperature effects the Voltage TIP : Design based on Cell temp and not ambient temperature ! 0ₒC 25ₒC 50ₒC 75ₒC Current [A] Temperature rise Temperature drop Voltage [V]

Choosing the reliable components for Solar Answer Choosing the reliable components for Solar

PV Module Always look for Tier 1 manufacturers Always analyse the datasheet of manufacturer carefully Be careful analysing the Power Warranty Look out for Power Tolerance Tip : Always go for positive only power modules ! Module power at STC +2% -2% 250 W 255 W 245 W 300 W 306 W 294 W Look out of TkVoc and TkVmp values

PV modules ( design consideration) Cell ~ 0.5V Cells in PV module are connected in series Bypass diode are connected to reduce the effect of shading

Shading ( design error) Loss of total or partial power output Prolonged shading lead to failure of bypass diode Can even lead to fire due to built up heat in module

PV module ( design consideration) Site Survey and predictive design modeling is very important Shading calculations are very important Know the highest and lowest historical temperature data ( in the last 20 years ) Max.mod.Voc = Voc * [ 100% + [ ( Tmin – Tstc ) * TkVoc ]] Particularly important for sizing the string Higher voltage than the operating voltage of inverter can damage them

Inverter selection Depends on the application and can change case-to-case Module Level ( MLPE) Microinveters DC-DC Optimisers String Inverters Central Inverters Operating DC voltage window of the inveter is an important constraint for design consideration Must have ground fault protection Newer version coming with Arc-fault protection

Inverter ( design consideration) Temperature effects the inverter selection 600 Coldest Day voltage (Voc) Inverter input voltage window Voltage [V] 200 Hottest Day voltage (Vmp) Time of the day Source: SEI,US

Wiring conductors Choose correct wire size based on Ampacity required for the design Maximum ambient temperature recorded Voltage drop No of wires in the conduit Heat dissipation Installation/removal Tip: The total number of bends in the conduit should not exceed 270 degree in each wire run !

Wiring ( design consideration ) Crimping of the lugs for the DC wires correctly Source: Etco.com

Wiring ( design consideration) Using Torque wrench and screwdrivers to torque each wiring terminations, installation as per manufacuter recommendation Source: solarprofessional.com

Grounding Ungrounded , Grounded , Grounding conductor, Ground Fault (GF) Ensure proper equiment grounding has been done to bond all the non-current metal carrying enclosure, equipment Module/racking should all be connected to ground via the inverter Inverter checks for GF everytime it boots up. It would not be able to detect GF, it if the earlier is not bonded Source: solarprofessional.com

Summary Inorder for a system to surpass its design life : Design of the system should be spot on Components chosen should be of high quality Use of symmetric design pattern would help in troubleshooting Wiring terminations should be torqued as per manufacturer torque setting Proper labeling of the wires, breaker, distribution boards is a must Overcurrent protection devices & disconnects has to be used adequately for the servicablility Onsite and remote Monitoring of plant/system with timely manitence should be done

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