Solar Photovoltaic Modules • Introduction to Photovoltaics • Component Parts • Panels • Mountings • Inverters • Ancillary components, cabling etc. • Electrical Installation • MPPT Strings • Grid Connection • System design; • For Part L • For Energy Production
Background Electronic Controllers for Grid tied and off-grid hybrid solar/wind systems.
Solar PVs • Photons cause electron flow across junction between two types of silicone • Process degrades at rate of about 0.7% per annum • Commercial efficiency typically 16% (compared to 60% thermal) • Complements wind as part of national renewable energy • Initially developed for remote power (satellites, then lighthouses) – Over 50 years in use • Massive price decreases as volume production rises
Solar PVs Spain
Charanka Solar Park 550Mw 3km from end to end 2,750,000 Panels
Charanka Solar Park 550Mw 3km from end to end 2,750,000 Panels
Potential for hvdc solar distribution
Economics • UK - Feed in tariff 16p plus savings or 4p for export • Germany - Production 12c plus savings • Ireland - Nil for production, 9c for exports (currently halted) • 4kw system in UK will earn € 1,000 to € 1600 per annum • 4kw system in Ireland will earn up to € 700 depending on self- consumption (can use diversion systems) Stick rather than carrot
System Design for Part L Technical Guidance Document Part L 2011 - 10 kWh/m2/annum contributing to energy use for domestic hot water heating, space heating or cooling; or - 4 kWh/m2/annum of electrical energy; or - a combination of these which would have equivalent effect.
Component Parts 1 PV array, 2 PV array combiner/junction box, 3 Grid-tied inverter, 4 Import/export meter, 5 Connection to grid, 6 Loads. Other configurations are possible Grid-tied photovoltaic systems 4-1
Monocrystalline module Cut from solid silicon rods with round edges removed. Hence appearance Photovoltaic effect 3-11
Polycrystalline module • Tends to have less of the blue tinge in modern production • Can come on white or black backsheet. White is more efficient due to better heat loss • Can be black or natural aluminium frame. Black usually more discreet but powder coating pushes up price Photovoltaic effect 3-12
All black (black backsheet) • Black mono so white triangles are not conspicuous • White is more efficient due to better heat loss, but black more aesthetically acceptable • Can be black or natural aluminium frame. Black usually more discreet but powder coating pushes up price Photovoltaic effect 3-12
Standards MCS in UK. • UK Microgeneration Certification Scheme • UK market standard as pre-requisite to feed in tariff • Sets standards for major components and for installation practice TUV tested Standards Required • EN 61215 - Energy Production • EN 61730 - Mechanical Safety • EN 62716 – Ammonia Corrosion Testing • EN61701 – Salt Mist Corrosion Testing
Dimensions • Most common panels are approx 1650mm x 992mm • Can be mounted in portrait of landscape format
Electrical Characteristics
Electrical Characteristics • At 800W/m 2 , 73% of 1kw production • Note Isc at 800W/m2 is less than Imp at 1kw • Therefore fuse protection on single string is not possible, (nor necessary)
Effect of temperature on the operation of solar pv modules Typical temp coefficient of pMax: 0.41%/K • Roof integrated systems will have poorer cooling • Important to calculate Voc at minimum temperature Photovoltaic effect 3-14
Voc (Open Circuit Voltage) • Must be calculated for the lowest possible temperature in that region (voltage rises with temperature) • Voc of panels in series must be less than Vmax for inverter • Voltage at 25 O C is 38.4V (STC is 25 O C and 1000W/M 2 ) • Temperature Coefficient is -0.32%/K • At -20 O C coefficient is 45 X 0.32% or 14.4% • Voc at -20 O C is 38.4+14.4% or 43.8V per module • If inverter V max is 450V, you should have no more than 10 panels in series in a string MCS Requires • Voltage: Voc(stc) x 1.15 • Current: Isc(stc) x 1.25
Effect of irradiation levels Unlike thermal, output is almost pro-rata Module current (A) U MPP voltage range Module voltage (V) Photovoltaic effect 3-15
Cabling Options
Cabling Options MCS Standard: Because PV array cables almost exclusively rely on double or reinforced insulation as their means of shock protection they should not be buried in walls or otherwise hidden in the building structure as mechanical damage would be very difficult to detect and may lead to increase instances of shock and fire risk. Where this cannot be avoided conductors should be suitably protected from mechanical damage, suitable methods may include the use of metallic trunking or conduit or the use of steel wire armoured cable in accordance with BS 7671
Cabling Options • Cables are to be well supported, especially those cables exposed to the wind. • Cables must be routed in prescribed zones or within mechanical protection, fully supported / cable tied (using UV stabilised ties) • Cables must also be protected from sharp edges • Observe procedures for dealing with live cables and prevent this where possible • Be aware of potential capacitor discharge delay on inverter
DC Layout – typical 4 panel array
Layout 8 panel dual-tracking system for partial shading or East/West
DC Isolator • Disconnects panels from inverter • No other connections should be broken or made while this connector is closed
Inverter • Injects DC from panels into grid • Must conform to EN50438 • Unique Irish variants • Usually under-sized slightly for improved efficiency • May include DC isolator • Most also offer wifi connectivity as optional extra • Micro-inverters – vs- Wall mounted MCS on Power ratio - It is common practice for an inverter power to be less than the PV array rating. In the UK, inverters are typically sized in the range of 100 - 80% of array capacity.
Inverter Specs
Inverter Specs Note: Higher Vin mad, Multi string, current per string,
Inverter Specs Lower efficiency at low power- hence tendency to slightly under-size inverter.
Inverter Micro-inverters – vs- Wall mounted
Inverter – Irish Standards
AC Isolator • Provides clear instructions on how to isolate system in event of fire or other hazard • Labelling also standardised under MCS process MCB in consumer unit • Usually an MCB in the consumer unit • Generally no RCD required.
Labelling Requirements
Labelling Requirements
Labelling Requirements
850W 850W Nothing on
1400W 600W 2000W
500W 600W 100W
400W ZZZzzz … 400W
400W ZZZzzz … 400W Residential Import Price: 22c approx Export Price: Was 9c. Now zero Currently not available
Immersion Diversion Units
Immersion Diversion Units • Solic uses triac to switch on load in mid-cycle in the same way that a dimmer switch works • This causes spike on the grid at the moment of switch on as seen on oscilloscope reading
Immersion Diversion Units • Products like EMMA ™ and Immersun ™ use high frequency switching using IGBTs or mosfets which do not require zero-crossing switch-off • Sine wave is unaffected • Some loss in the switching circuit due to voltage drop across IGBT/mosfet. • Much more expensive units.
Immersion Diversion Units • Typical solar thermal system will delivery 1800 KwHrs of hot water per annum • Typical solar PV 2kw system will deliver 1900 KwHrs of POWER per day • If 33% of this is used as electricity, saving is 19c per KwHr on that portion • Remaining 66% diverted to heating water will save approx 9c per KwHr. • Immersion diversion would cause de-rating of the system under DEAP so should be a retrofit • Viable alternative to export tariff until this returns • Only really viable for systems above about 1.5kw • Low cost units generally not adequately certified.
Applying for Grid Connection • Complete form NC6 or for new dwelling, inform ESB of the size of inverter which will be used • Provide EN50438 certificate for inverter (with Irish Variants) • Industrial systems (over 6kw) require Mainspro or similar relay http://www.esb.ie/esbnetworks/en/commercial-downloads/NC6.pdf Systems above 25A (6kw) single phase or 16A (11kw) 3 phase • Complete form NC5 • Will require use of Mainspro or similar relay to isolate system • Fee of € 700 for desktop survey • You can ignore most of the requirements on the form for sub 50kw Systems. Above that, it will cost yer! (will require G10 relay and site testing by ESB) • http://www.esb.ie/esbnetworks/en/commercial-downloads/NC5.pdf
Roof Mounting
Roof Mounting
Spacing Roof Hooks • Max space between roof hooks – 800mm • Max over-run from (A) to end of rail – 200mm • Rails may be joined (C)
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