Solar PV Systems (Engineering, wiring & grid connection) - Martin Cotterell (Sundog Energy)

Solar photovoltaic systems

Engineering, wiring & grid connection

1. PV array options2. Siting & design considerations3. Component selection4. Grid connection5. MCS & installer selection

Installing systems since 1995

Installed hundreds of systems across the UK

Installations on houses, schools, offices, community centres, churches, village halls, libraries, museums, farms, railway stations and more.

Sundogs (or parhelia) are brilliant spots of light sometimes seen around a solar halo

Sundog Energy

Sundog Energy current live projects

Kings Cross Station

Client – Kier / Network Rail

Project size – 240kWp / £1.3M

Technology – Bespoke PV glazing

Ferrier Point

Client – Rydon / Newham Council

Project size – 50kWp / £200K

Technology – PV facade

PV module

Semiconductor devices that convert sunlight directly into electricity

No moving parts PV modules typically offer a 25 years performance warranty (life expectancy ~50 years)

Grid connected PV systems Solar array – generates DC electricity

Inverter – converts DC to AC

Connected to Fuse Box / Distribution Board

Electricity used in property and/or exported

Above roof systems

Cost effective solution

Comprise standard framed modules, fixed to a mounting assembly just above the existing roof.

Robust and weather-tight fixings are available for almost all roof types (slates, tiles, metal sheet etc).

Array options

Pitched roof - Integrated systems

Directly replaces conventional roofing materials

Various products available Selection depends on tile type and the visual effect desired. Small format PV tiles are typically more costly than larger format solutions

Typically installed on new roofs or as part of re-roofing schemes.

Flat roof systems

Can be installed to a fixed frame or to a ballasted mount

Ballasted systems are the simplest (rely on the weight of the ballast to resist wind loads); require no roof penetrations; simple to move for any subsequent roofing works.

Fixed frames are typically new build / re-roofing solution

PV glazing systems

Can replace glass in roofs, skylights and facades

Cell layout, cell spacing, single / double glazing and desired light transmission all variable

As a bespoke product is a more expensive option - typically of interest for commercial or high value projects

PV facades

PV modules and PV glazing can be used within building façades

Often use bespoke modules or laminates, but standard modules can be used in some circumstances

Wind loading issues to be considered on large facades

Ground mounted

Huge variety of locations and structures will accept PV array

Ground mounting often very cost effective & practical option

Structures such as pergolas, shelters and canopies can be created or adapted to take PV

Tracking devices can boost performance by 20% or more

Effect of orientation and pitch on array performance (% of ideal)

Vert. 80 70 60 50 40 30 20 10 Horiz.

EAST 58 65 70 76 80 84 86 88 90 90

SE 69 77 84 89 93 96 96 96 94 90

SOUTH 71 80 87 93 97 100 100 98 96 90

SW 67 75 82 87 92 95 96 96 94 90

WEST 56 63 69 74 78 82 86 87 89 90

Ideal site is one that faces south with a slope of around 30-40 °.

Other orientations and pitches may also be viable with relatively little drop in performance

Siting considerations

Orientation and pitch

Other factors

Shade - Any shade, such as from trees or neighbouring buildings, can make a large impact on performance

To work effectively, the whole PV array needs to be free from shade for the majority of the day

Size - a 1kWp PV array will occupy at least 8m² of roof. Positioning an array too close to the edges of a roof may compromise the aesthetics of the installation and has implications on wind loading.

Rule of thumb: 1kWp array per year … Generate approx 800kWh (units) of electricity Save approx 0.4 tonnes of CO2

Not a sundog site!

Field arrayLand usage rules of thumb

Dense layout ~ 4acres / MWp Open layout ~ 5acres / MWp

Site shape, slope and shade factors all influence capacity

System performance modellingSoftware models such as PVSyst can estimate can estimate likely performance

System Monitoring Optimising yield

Ensuring performance

Rapid fault detection

PV array Inverter

FIT meter

Siteconnection

to maindistribution

board

• Bankable?• Reliable?• Warranties

System selection - Key components

Site dependant components

PV array InverterFIT meter

Siteconnection

to maindistribution

board

Mounting frameGrid connection

Commercial and agricultural roofsKey considerations

• Size• Aspect • Pitch• Shading

• Structural strength• Wind loads• Fixing type

• Roof material (asbestos)• Access (fragile roofs)• Caustic environment?

Ground mounted systems

Site• Size• Aspect • Slope• Shading• Ground conditions• Wind loads• Land usage• Access

Array design• Mutual shading (density)• Ground clearance • Maximum height (planning)• Speed of installation• Fixed / adjustable / tracking

Grid connection

Single installations

• Install and commission system• Notify DNO within 30 days and provide commissioning info

• System <16A / phase• Type tested inverter to G83/1• Installed in accordance with G83/1

Multiple installations

• Discuss scheme with DNO• Install & commission as agreed

Small systems

G83/1 compliant

≤ 50kW 3 phase≤ 17kW 1 phase Larger system

DNO consent required prior to connection? No Yes Yes

Protection requirements To meet G83/1-1

To meet G59/2

Type verified protection equipment accepted

To meet G59/2

Witnessed commissioning by DNO? No At discretion of DNO

LV: At discretion of DNO

HV: Yes

Connection variations – larger systems

Project planning phaseInitial system design – ensuring compliance to standards

Information phase ( Information exchange with DNO) System design, protection arrangements, peak and fault current, harmonics, earthing etc. Network issues

Design phase (Formal submission of design to DNO)Where new infrastructure required >>> DNO prepares connection design and issues a connection offer

Construction phase Construction of plant. Installation of grid connection infrastructure (DNO and/or ICP)

Testing and commissioning phase G59/2 commissioning (witnessed?).

DNO connection process

“to evaluate microgeneration products and installers against robust criteria, providing greater protection for consumers”

MCS mark owned by UK GovernmentMark licensed to scheme administrator (Gemserve)Mark sub-licensed to Certification bodiesCertification bodies issue mark to product suppliers & installersInstaller provides customer with MCS certificate for system

MCS certificate enables FIT payments

MCS Mark

Scope: Up to 50kWp (relevant for larger schemes?)

Installer

MCS001 Installer certification scheme requirements

MCS3002 Rrequirements for contractors undertaking the supply, design, installation, set to work, commissioning and handover of solar photovoltaic (PV)

microgeneration systems

Product

MCS005 Product Certification Scheme Requirements: Solar PV

MCS011 Test and acceptance criteria

MCS010 Generic Factory Production Control (FPC) requirements.

MCS – Key PV documents

Photovoltaics in buildings - Guide to the installation of PV systems

BS7671 Requirements for Electrical Installations

MIS3002

What MCS does NOT do …

Important to recognise exactly what MCS covers

MCS accreditation process does not particularly scrutinise H&S

A recent photo from the UK press... spot the scaffolding & PPE?

Relevant experience …

MCS accreditation process does not particularly differentiate in terms of scale, complexity & experience

… PV installations obviously vary!

MCS scope up to 50kWp …. But client must evaluate if experience relevant

www.sundog-energy.co.uk