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

Solar photovoltaic systemsEngineering, wiring & grid connection

PV array options
Siting & design considerations
Component selection
Grid connection
MCS & installer selection

Sundog Energy
 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 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

Array options
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).

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

Siting considerations
Orientation and pitch
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

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 array
Land usage rules of thumb
Dense layout ~ 4acres / MWp
Open layout ~ 5acres / MWp
Site shape, slope and shade factors all influence capacity

System performance modelling
Software models such as PVSyst can estimate can estimate likely performance

System Monitoring
Optimising yield
Ensuring performance
Rapid fault detection

System selection - Key components
Site
connection
to main
distribution board
FIT meter
PV array
Inverter
Bankable?
Reliable?
Warranties

Site dependant components
Site
connection
to main
distribution board
FIT meter
PV array
Inverter
Mounting frame
Grid connection

Commercial and agricultural roofs
Key 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

Small systems
System <16A / phase
Type tested inverter to G83/1
Installed in accordance with G83/1
Single installations
Install and commission system
Notify DNO within 30 days and
provide commissioning info
Multiple installations
Discuss scheme with DNO
Install & commission as agreed

Connection variations – larger systems

DNO connection process
Project planning phase
Initial 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?).

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

MCS Mark
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 systemMCS certificate enables FIT payments
Scope: Up to 50kWp (relevant for larger schemes?)

MCS – Key PV documents
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
MCS005Product Certification Scheme Requirements: Solar PV
MCS011 Test and acceptance criteria
MCS010 Generic Factory Production Control (FPC) requirements.

MIS3002
BS7671 Requirements for Electrical Installations
Photovoltaics in buildings - Guide to the installation of PV systems

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

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

by Farming Futures on Oct 15, 2010

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