Solar Photovoltaic Modules

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

4-1

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

Monocrystalline module

3-11 Photovoltaic effect

Cut from solid silicon rods with round edges removed. Hence appearance

Polycrystalline module

3-12 Photovoltaic effect

• 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

All black (black backsheet)

3-12 Photovoltaic effect

• 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

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/m2, 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

3-14 Photovoltaic effect

Typical temp coefficient of pMax: 0.41%/K

• Roof integrated systems will have poorer cooling • Important to calculate Voc at minimum temperature

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 25OC is 38.4V (STC is 25OC and 1000W/M2)

• Temperature Coefficient is -0.32%/K

• At -20OC coefficient is 45 X 0.32% or 14.4%

• Voc at -20OC 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

3-15

UMPP voltage range

Module voltage (V)

Mo

du

le c

urr

en

t (A

)

Photovoltaic effect

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

Nothing on

850W

600W

2000W

1400W

600W

100W

500W

ZZZzzz…

400W

400W

ZZZzzz…

400W

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)

Roof Hooks Pantile Tiles

Wider base plate so that hook can be in tile dip. Usually one every 60cm to 80cm

Best practice to notch pantiles at roof hook

Roof Hook Flashing

Roof Hook Flashing

Rail Spacing

Roof Hook Spacing

Roof Integrated Benefits • Less visual impact • Lower wind exposure Disadvantages • Higher installation time

& cost (partly offset by reduced slates)

- e.g. 2kw system • €2520 on-roof • €2870 in-roof

- 1kw System • €1460 on-roof • €1690 in-roof

• Reduced output due to higher temperature

Trapezoidal Steel

Corrugated Steel Trapezoidal Steel

• Very low-cost industrial systems

• As little as 4c per watt

• Very quick to fit

• Mounting screws self—drilling

Standing Seams

Various fittings to attach rails to standing seams

Industrial Systems

• Often better payback as displacing all power at retail price

• Use monitoring in advance to assess baseload

Potential Use • Super-valu and similar supermarkets • Hotels • Industry • Anywhere with environmental

credentials to maintain

Industrial Systems East/West

• South facing 30O pitch optimal for yearly production • South facing 65O pitch optional for winter production (road signs) • Wind loading, especially ballasted roof systems, makes mounting expensive • Self consumption power available over a longer period with some facing

east and west. However, winter production reduced. • Lower pitch is often used to reduce wind load

• South facing 4kw system at 30O slope produces 3976 KwHrs per year • South facing 4kw system at 15O slope produces 3751 KwHrs per year • East-west facing 4kw system at 10O slope produces 3319 KwHrs per year • Loss of 16.5% production can be compensated with additional panels

Industrial Systems East/West

• Quick assembly, low wind loading, ready ballasted • Faces east and west at 10O pitch • Full wind load data available

Industrial Systems Consol

Industrial Systems Consol

Industrial Systems Consol

Industrial Systems Consol

Industrial Systems Consol

Industrial Systems Consol

Industrial Systems

Industrial Systems

Industrial Systems

Industrial Systems Energy provided over longer period

0

500

1000

1500

2000

2500

3000

3500

4000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

16S/15d

8EW/10d

16S/30d

Industrial Systems But diminished in mid-winter

0

500

1000

1500

2000

2500

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

16S/15d

8EW/10d

16S/30d

Industrial Systems Lightning Protection

Generally not required except on tall buildings • Consult lightning specialists • If isolated air termination

system fitted, maintain separation distance and place modules within protected area

Industrial Systems Lightning Protection

• No air termination • Use type 2 surge

protectors on both AC and DC sides

Industrial Systems String Combiners / Fuses

Multiple Strings can produce higher current in short circuit

In > 1.5 x Isc stc In ≤ 2.4 x Isc stc In ≤ Maximum series fuse value Fuse both +ve and -ve

Industrial Systems String Combiners / Fuses

Can use string combiner boxes to implement double pole fuse

Industrial Systems String Combiners / Fuses

Can use string combiner boxes to implement double pole fuse

Industrial Systems String Combiners / Fuses

Can use string combiner boxes to implement double pole fuse

Industrial Systems Mainspro Relay

• Required if exceeding

6kw single ~ or 11kw 3~

• Over 50Kw becomes “Embedded Generation” requiring G10

Commissioning

Commissioning the system The grid should be connected to the inverter first, then the DC isolator closed. The inverter will then power up and can have its country settings set. If there is a need to disconnect the system, it is generally preferred to isolate the grid from the inverter first, and then open the DC isolator.

Commissioning

• Should provide handover documents detailing the system

• Will require online certification of inverter installation

System Design – for Part L

• Renewable Energy equivalent to 10KwHrs thermal or 4KwHrs Electricity per m2 per annum

• Also must meet CPC and EPC targets (usually with building envelope, but small excesses can sometimes be remedied with PV)

• For example, house 150m2 will need to produce 600KwHrs electricity. Need to consider; • Roof orientation • Roof pitch • Shading factor

System Design Part L

• Apendix M of DEAP Manual; The electricity produced by the PV module in kWh/year is 0.80 x kWp x S x ZPV where S is the annual solar radiation from Table H2 (depending on orientation and pitch), and ZPV is the overshading factor from Table H3. • Take a system with three off 250W panels. Total panels = 750W or 0.75Kwp • Lets assume house has pitch 30 degrees and roof facing SE.

Orientation & Pitch

0.80 x kWp x S x ZPV • KwP = 0.75 • Roof pitch 30 degrees facing SE has S (solar radiation) = 1021 (KwHrs/m2/yr)

Shading Factor

0.80 x kWp x S x ZPV • KwP = 0.75 • Roof pitch 30 degrees facing SE has S (solar radiation) = 1021 (KwHrs/m2/yr) • Assume shading from Table H3 is “none or very little”. ZPV = 1

Calculation

0.80 x kWp x S x ZPV • KwP = 0.75 • Roof pitch 30 degrees facing SE has S (solar radiation) = 1021 (KwHrs/m2/yr) • Assume shading from Table H3 is “none or very little”. Zpv = 1

• Output is • 0.8 x 0.75Kwp X 1021 X 1 = 612.6KwHrs/Yr.

• System meets renewables obligation of Part L for house 150m2

• PvSyst suggests this system in Dublin would produce 675 KwHrs.

Calculation

0.80 x kWp x S x ZPV • KwP = 0.75 • Roof pitch 30 degrees facing SE has S (solar radiation) = 1021 (KwHrs/m2/yr) • Assume shading from Table H3 is “none or very little”. Zpv = 1

• Output is • 0.8 x 0.75Kwp X 1021 X 1 = 612.6KwHrs/Yr.

• System meets renewables obligation of Part L for house 150m2

Another formula

Panel size in Peak Watts = 4 x area in m2 / (S x Zpv x 0.8)

Online Part L Calculator

Online Energy Production Calculator

Entering in DEAP

Entering in DEAP

• Enter calculated production for both Part L contribution and Delivered Energy. • Look up current value for Primary Energy Conversion Factor on SEAI website

(currently 2.37) • Look up CO2 Emission Factor for electricity on SEAI website (currently 0.522)

• http://www.seai.ie/Your_Building/BER/BER_FAQ/FAQ_DEAP/Results/What_are_the

_electricity_factors_used_in_the_latest_version_of_DEAP.html

Combining Thermal and PV

• Clients for one-off houses may prefer to use solar thermal. • For large one-off houses, (over 200m2), it is economically difficult to meet Part L with

solar thermal alone • In such cases, design an optimal solar thermal system to meet the clients’

requirements • See what percentage of renewable energy component has been met • Calculate remaining energy required and meet this with PV.

Combining Thermal and PV

Example • House 300m2 requires modest 300L solar thermal system. • Would need 3,000 KwHrs/yr thermal • 4m2 solar thermal panel and 300L cylinder produces 1700KwHrs/yr • 1700/3000 = 56.67% • Need to produce 43.33% of requirement using PV • 300 x 4 x 43.33% = 396Kw Hrs. • On south facing roof at 30O pitch, 2 off 250w panels would produce

430KwHrs/yr. • Likely price €1,000 for hardware.

Other ways of achieving Part L

• There is no “one size fits all” • Some households use large amounts of hot water in summer, others use

showers, dishwashers and washing machines. • Maintenance of solar thermal required.

• Heat dump strategy required;

• To cope with excess summer production / holidays • Lack of heat dumps has given industry bad reputation

• Stagnation

• Puts pressure on component parts • Degrades glycol

• Heat Pump

• May be justified if large amount of space heating required • In well insulated envelope, or near-passive, savings negligible and would

not be recouped in the lifetime of the system

Planning Exemptions

Solar Thermal or PV panel in a domestic setting • Total panel area must not exceed 12 sq. m or 50% of the total roof area including

existing panels • The distance between the plane of the wall or pitched roof and the panel must not

be more than 15cm. • The distance between the plane of a flat roof and the panel must not exceed 50cm. • The panel must be a minimum of 50cm from the edge of the wall or roof on which

it is mounted. • A free standing array’s height must not exceed 2m above ground level. • The erection of a free standing array must not reduce the area of private space to

the rear or side of the house to less than 25 sq. m. All assumes not in a visually sensitive area.

Planning Exemptions

Solar Thermal within a light industrial or business setting • Can not be erected on a wall. • Total panel area must not exceed 50 sq. m or 50% of the total roof area including

existing panels. • The distance between the plane of the pitched roof and the panel must not exceed

50cm in a light industrial building and 15cm in a business premises. • The distance between the plane of a flat roof and a panel must not exceed 2m in a

light industrial setting and 1m in a business premises. • The panel must be a minimum of 50cm from the edge of the roof on which it is

mounted or 2m on a flat roof. • Any associated equipment or storage must be within the roof space of the building. • A free standing array’s height must not exceed 2m above ground level. • The total aperture area of a free standing array must not exceed 25 sq. m. • No advertising can be placed on the panel and a free standing panel must not be

placed to the front of the premises.

www.constructionpv.ie

Office / Tech Support: 01 254 4140 Quentin: 086 869 3140 quentin@constructionpv.ie Philip: 085 888 0005 philip@constructionpv.ie