Onboarding Best Practice Guidelines

8.1. Construction and operation under EPC warranty

Construction and installation: company or country relevant requirements

In the construction phase, the solar power plant is installed based on installation manuals provided by suppliers to assure the proper storage, handling and installation of mounting systems, PV modules, inverters, transformers, cabling, monitoring system/sensors and other balance of system components. It also ensures the quality of the installation as well as the long-term stability of the PV system.

A proper schedule and preparation of several activities around the construction are important and should preferably be organised according to common project management techniques. This includes clear definition of objectives, activities, and responsibilities (who does what?), time plans and milestones (when?), cost planning, and quality assurance. To achieve this, an effective and efficient communication, documentation and reporting flow between the Asset Owner, the EPC service provider and the subcontractors is necessary. This will help encourage accountability, potential construction defects are promptly identified, high standards upheld, and monitoring the EPC service provider’s performance is easier.

The overall construction activity can be divided into two phases: firstly, the preparatory phase, related to the preliminary activities and secondly, the construction implementation phase, including site preparation, civil, mechanical, and electrical works necessary to complete the plant and bring it to the production phase.

A. Mounting structure (fixed tilt)

Racking systems hold valuable modules in place and ensure stability of the installation of the PV system. Mounting components consist of various metal parts with different coatings or materials, such as aluminium, alloy, stainless steel, or galvanised steel. Corrosion can occur due to the constant and long-term exposure of these materials to each other, to soil conditions and to environmental stresses, such as rain and moisture and other atmospheric pollutants like chlorides in marine environments or sulphur dioxide and nitrous oxides in industrial locations. As corrosion intensifies over time, serious structural failures in racking and mounting components can result in instability in the PV system and cause it to malfunction. It lays at hand that quality of mounting systems plays a tremendous role in each step from manufacturing to installation, maintenance, and recycling.

As lifespans of solar PV systems can reach up to 30 years, racking manufacturers must target a similar life span for the racking materials. The following norms and guidelines are of great significance and should be adhered to during the project development and during the construction stage:

·       The manufacturing process of mounting systems should be in accordance with Eurocodes 1991 1-1 - 1-6 Actions on Structures. The norm includes guidance on the actions to be performed on structures designed for use in buildings and other civil engineering works

·       In addition, to prevent corrosion of the mounting structure, manufacturers should comply with the standards “Specifications and test methods on hot dip galvanised coatings on fabricated iron and steel articles” (EN ISO 1461) and “Continuously hot-dip coated steel flat products for cold forming - Technical delivery conditions” (EN 10346). The two quality standards underline the importance of corrosion free purlins, aluminium mounting brackets and bolts and focus on the chemical composition and mechanical characteristics of the components for racking systems in general. Information on coating thickness (e. g., zinc coated steel, anodised aluminium, etc.) can be determined by measurements in testing labs or on site

·       A third standard, the “Execution of steel structures and aluminium structures - Part 1: Requirements for conformity assessment of structural components” (DIN EN 1090-1), assures the quality of steel components, aluminium components, and kits in the manufacturing process

·       The material quality should be verified on documentation basis (alloy, etc.). Spot checks of the anti-corrosion coating thickness can be performed in factory or onsite. Further the dimensions and tolerances of the delivered parts shall be verified against the available documentatio

B. Mounting structure (trackers)

Tracker systems offer a significant additional complexity to a PV power plant system as it entails moving parts being added to an otherwise static system. When considering tracking, be it single axis or dual axis tracking, in addition to the previous section, the following points should be considered:

Tracker system selection

·       Structural calculation according to applicable standards in the country of the project and international codes like ASCE or Eurocodes. This calculation should consider the specific conditions known or foreseen for the soil conditions. It is highly recommended to check whether the tracker system has undergone wind tunnel testing, and in addition, CFD (computer fluid dynamics) modelling to simulate wind situations. This is particularly important for resonant frequency conditions that can occur at wind angles of attack that can hardly be simulated in a wind tunnel. Note that catastrophic failure at resonant frequencies does not necessarily require high wind speeds

·       Certification of the PV tracker against relevant standards like IEC 62817, UL 3703 or UL 2703. Specific confirmation that the components used in the trackers to be supplied are listed in those certificates

·       Accelerated lifetime tests beyond those associated with the certifications mentioned above

·       Justification in the form of studies, wind tunnel measurements or tracker measurements showing that all the aero-elastic stabilities are properly added to the structural calculation mentioned above. Particularly, the following instabilities should be considered as a minimum: flutter/galloping, torsional divergence, buffeting, vortex-induced vibrations, and aero-elastic deflection. Justification of the values used for the damping ration and natural frequency should be provided.

Tracker system reception and installation

Once on site, the delivered equipment should be verified by collecting a sample of each element of the structure which is then measured and verified against the specifications. Certificates for the steel and galvanisation are provided directly from the manufacturer’s sub-suppliers with site measurements of dimensions and thickness.

It is recommended that the installation process should be overseen by a representative of the manufacturer and the following recommendations should be a general checklist for this stage, being part of the project commissioning stage.

1.       Torque verification according to manufacturer specifications 

2.       Tolerances in installation are within the levels accepted by the manufacturer

3.       Piles driving are tested (pull-out) showing minimum recommendation by the manufacturer

4.       Tracker Control Units (TCUs) and Network Control Units (NCUs) are installed and connected with configuration approved by the manufacturer and Owner’s engineer

5.       Meteorological stations are commissioned according to manufacturer recommendations and testing to see whether the stowing strategy is working

Special care should be taken if material is galvanised. To maintain the corrosion protection, the galvanisation must not be damaged by scratching or any machining.

C. Construction

Construction preparatory phase

The construction preparatory phase includes those planning and preparatory activities that ensure the smooth realisation of the PV plant. For this purpose, it is important that the construction project is correctly set up according to project management principles: the Asset Owner and the EPC service provider define project organisation and objectives, arrange main parts of the project in a work-breakdown structure (WBS), deduce a time schedule with clearly defined work packages, including responsibilities/accountabilities (responsibility matrix, for example, a RACI matrix), interdependencies, duration and resources. This time schedule shall be the reference for monitoring the project’s progress from both a physical and cost control perspective and needs to be regularly updated.

Site survey

The site survey aims at checking that there are no physical and geographical constraints or inconsistencies with the assumptions and technical details defined in the Execution design. If there are inconsistencies between the execution design and the site survey, the EPC service provider should consider doing another topographical survey with a drone.

The survey is also necessary for checking the actual status of the site and for planning the preliminary activities necessary to prepare the site for the mobilisation of personnel and equipment and the start of the main construction activities.

While the effective mobilisation of the EPC service provider and their subcontractors usually takes place once contracts enter into force (in general when a notice to proceed is issued by the Asset Owner), the execution of certain early works, sometimes also called preliminary works, is a project strategy that is becoming more frequent.

With reference to construction activities set-up, the key topics to be investigated during the site survey are:

·     Mapping of the construction site (allotment and boundaries, topography, etc.)

·     Definition of the area for temporary facilities and storage/warehouse

·     Identification and mapping (geolocalisation) of interferences to be considered during construction, for which drones can be used

·     Assessment of critical elements for construction and identification of mitigating actions (technical risks, rests of bombs, hazardous waste, but also archaeological discoveries)

·     Detailed survey of transportation facilities and routing and other logistic items

·     Execution of the pull-out test, necessary for the final test of the selected foundation design of the mounting structures

Stakeholder management

The primary tool for understanding the context in which the project is implemented is to identify and understand the stakeholders involved in, or affected by, the project. This allows one to become aware of their expectations and to determine the effective, potential, or perceived impact that the project can have on them identifying methods for involving them.

The identification of the stakeholders and their needs and expectations requires suitable knowledge of the relationships that exist between the different actors that are present and active in a given context. For this purpose, all subjects that could influence or be influenced by the project must be considered.

It is important that the identification of the stakeholders is not limited to local and administrative authorities but should also consider people and organisations that are relevant for local communities, as they represent their interests and identity.

Construction preparation plan

Construction Planning aims at planning all construction activities properly and guaranteeing that resources are available and scheduled consistently with activities. This avoids any unplanned stops.

After definition of the project scope of work, the project management team structures the project by organising the activities in a hierarchical structure, the Work Breakdown Structure (WBS). Only the activities identified with the WBS shall be within the project scope and, therefore, can be planned and controlled. There is only one WBS per project. A well-defined WBS:

·     Provides complete definition of the project scope at different levels

·     Allocates tasks and responsibilities

·     Defines a numbering system, which is used as reference in project plans, reports, and technical documentation

·     Provides an input to integrate cost and schedule data

·     Ensures the alignment with the contracting execution strategy

·     Facilitates the roll up of cost, progress, and schedule performance information for reporting purposes

All parties (the Asset Owner, the EPC service provider and other service providers) involved in the project should comply with the WBS and related coding system. Clear and effective communication between the Asset Owner, the EPC service provider and other service providers (and in general, all third parties involved in the project), and constant monitoring of the construction work progress according to the WBS, are key to ensuring full alignment on scope of work, objectives, deliverables, and timing.

WBS’s lowest hierarchical items are the work packages (WP). By defining each WP in detail and considering dependencies, the project plan is created. Each WP should contain at least the following information:

·     Name

·     Unique number/code

·     Version and status information

·     Description of content and results to be obtained

·     Prerequisites and dependencies (deliverables required etc.)

·     Projected duration

·     Resource requirements (people, material, tools, vehicles, etc.)

·       Person responsible for the WP

A detailed scheduling of the activities, including milestones, is essential to completing the work in a timely manner. Proper scheduling of the works is mandatory for correctly managing and controlling the progress of the project. If the work plan has not been prepared appropriately, mistakes and delays cannot be identified, and corrections cannot be implemented. Furthermore, the project plan needs to be updated regularly.

Project managers derive subordinate plans and documents from the central project plan. For example, the EPC service provider and other service providers will have planning, scheduling, reporting, and documentation obligations, according to the stipulated contract. With reference to the WBS, contractors should be responsible for the lower-level activities schedules and plans. A typical document for this phase is the mobilisation plan, which includes:

·        Construction site organisation chart: the subcontractors (civil and electro-mechanical) need to provide the construction site organisation chart which indicates all the expected positions, the staff residence times and the expected hours.

·       List of site vehicles and equipment: subcontractors must provide the list of vehicles and equipment they intend to use for different kinds of work, accompanied by certificates of suitability and maintenance and/or testing sheets.

Work plan and mobilisation plan guarantee in-time arrival and accommodation of construction site personnel and assembly materials. They also ensure that the different elements of the construction phase are properly coordinated.

Based on the defined project schedule (baseline), the associated physical progress curve should be determined, to establish a reference plan for the percentage of physical completion of the project at each date. This is key for proper project monitoring.

To calculate the project’s physical progress, one must define specific calculation rules to apply to each elementary activity type, as well as determine the weighting criteria (see details in the chapter 11.1. Project Performance KPIs of the EPC Best Practice Guidelines).

The construction plan should also define processes and procedures relating to the interface of the construction team with the rest of the project staff, in particular with the engineering, EHS and quality management teams.  It should be assured, for example, that all the project changes proposed by the EPC service provider and other service providers are checked and approved by engineering department (change management). Furthermore, the construction activities should be verified in accordance with the quality control plan and HSSE procedures (quality management). Other control activities concern cost/budget, HSSE compliance, documentation, etc. 

Check and finalisation of working permits

Country-specific legislation and regulations around HSSE and construction activities are continuously evolving. It is critical to be sure that all works, administrative permits, and authorisations have been obtained to avoid breach of any legal provision. Such a breach could result in severe consequences, both in terms of personal and administrative sanctions and in downtime and delay in the execution of the activities.

A useful tool to ensure full compliance is the prescription and authorisation checklist which should identify all the relevant legislation and regulations applicable to the specific project and location. It also lists all requisites necessary to start the construction activities (authorisations, particular training requirements for certain works, such as works at height, land lease agreements, etc).

Activation of external suppliers (services and materials)

Once all preliminary activities have been assessed and completed, the construction activities are ready to start. All subcontractors and suppliers must be activated according to the specific clauses of the relevant contracts and based on the scheduled activities. The scope of this phase is to ensure that all resources are present at the site in a timely manner to avoid any downtime and delay.

Construction implementation phase

Construction site activities must be supervised by the EPC service provider’s Construction Manager. They should coordinate with the Asset Owner’s Construction Manager and the Construction Supervisor on the monitoring and control of subcontractors. Throughout construction, drone construction monitoring flights should be carried out periodically to monitor, record and report on construction progress and quality. The data from these scans can also provide valuable support to H&S, stock management, and adherence to local planning and environmental regulations. For HSSE-related best practices, refer to Chapter 5 of the Guidelines in question and Chapter 3 on Health, Safety, Security, and Environment of the EPC Best Practice Guidelines.

Construction site organisation

Construction site organisation refers to the preparation of the site for the start of civil, mechanical, and electrical works.

The effective mobilisation of the EPC service provider and related subcontractors usually takes place approximately 60 days from the signature of the contract. However, preliminary site preparation and executive engineering may begin immediately after signing.

In the mobilisation phase, contractors will begin to mobilise direct and indirect labour, equipment and means so that all planned activities can start as scheduled.

Site preparation main activities are:

·     Opening of the construction site

·     Archaeological survey may be requested by local authorities depending on the historical interest of the site

·     Removal of vegetation removal and the superficial part of soil where foreseen (this kind of activity should be minimal in accordance with a positive biodiversity strategy)

·     Staking and beating of the poles of the structures

·     Visual mitigation works planned

Civil works

Civil works refers to excavation for the construction of cable ducts, including foundation, MV overhead line supports, preparation of the areas where inverters and DC boxes will be installed, distribution station, road construction, and any earthworks in general.

They must be planned and implemented to minimise the interference and the overlap with the electro-mechanical activities described below, which are often difficult to manage from a safety point of view.

Biodiversity issues need to be considered to minimise the impact of civil works. Where this is not possible, restoration or compensation measures should be taken, but it is always better to reduce destruction during works. Raising the awareness of personnel and clear guidelines can help to achieve this.

Electro-mechanical works

Mechanical activities mainly consist of:

·     Withdrawal of materials from the Contractor warehouse

·     Assembly of metal structures

·     Installation of PV equipment / panels

·     Package / cabin assembly

·     Tests and inspections

Electrical activities mainly consist of:

·     Laying ground network (equipotential bonding)

·     Laying DC (LV) solar cabling and related components for connecting PV module strings to inverters using tools certified/qualified by the manufacturer for PV cable-connectors assembly. At present DC cabling configurations can vary a lot but nevertheless, laying DC cabling is a key element of the electrical works

·     Laying MV cables from transformer stations to the distribution station

·     Laying LV auxiliary cables

·     Cabin and field connections

·     Tests and inspections

Ancillary works

Ancillary works are activities that are not directly connected with the assembly of the “electric generation plant”. They refer in general to security (fencing, CCTV, lighting, …), vegetation care, internal roads, signposting, and so on and so forth.

These works, even if not prioritised, must not be underestimated because they could delay the handover of the entire plant.

Grid connection

Utility scale PV plants need to be connected to the network, usually managed by the Transmission System Operator (TSO). Connection complexity depends on the distance between the plant and the substation, its conditions and the technical solution identified for the connections. These works are the final stage of the construction activities and normally require the involvement of the TSO, which should be scheduled well in advance.

Checks and functional tests

Once the plant is completely built and connected to the grid, one must test that it works properly. It is important that tests are carried out according to a detailed procedure agreed between the EPC service provider and the Asset Owner.

To this end, the EPC service provider must send the Asset Owner a detailed plan of execution of all the work necessary to reach Start-up (Start-up Plan), before the start of the Mechanical Completion and Pre-Commissioning activities of the plant.

The plan should include the following minimum requirements:

·     Definition of a start-up team

·     Definition of the project functional units and related sub-units

·     Definition of the plant sections that can be put into production in sequence

·     Definition of the schedule and procedures for carrying out the preparatory tests for the start-up for each functional unit and plant section

·     Description of how to perform the Mechanical Completion and Pre-Commissioning tests on the functional units

·     Description of the execution of the Commissioning tests on the functional units and on the entire system

Mechanical completion

When the plant is completely built and connected to the grid, after a visual inspection, the Asset Owner issues the Mechanical Completion Certificate (MCC). 

The aim of the visual inspection is to verify:

·     That all components and materials are present and in accordance with the project documentation

·     The compliance of the completed project with the project documentation, the Technical Specification, and the current legislation

·     The electro-mechanical completion of the plant

·     That all components are free of visible damages that could compromise the safety of the components and personnel

·     That the components have been installed correctly

·     The correct identification and labelling of all components such as inverters, DC boxes, cables, support structure rows, switches, communication devices, monitoring elements, etc.

·     The correct execution of the connections 

·     An aerial survey to validate the asset against its design layout

Training of Asset Owner and O&M service provider

As soon as the plant is ready for operation, after MCC has been issued, the EPC service provider should arrange for a specific training for the Asset Owner and the O&M service provider’s personnel (that could be a third-party or the O&M division of the EPC service provider). This training can transfer the knowledge and philosophy with which the plant has been designed and constructed.

Training is important as it allow the O&M service provider’s staff to familiarise themselves with the plant and its operations. Poor training standards can result in lower performance of the plant, due to delays in detecting system malfunction signals, resulting in longer downtime as faults are resolved. This is also an opportunity for the O&M service provider to give feedback to the construction (and engineering) team, especially if both belong to the same company.

The Asset Owner’s personnel should also receive training. This will help avoid misunderstandings between the Owner and O&M service provider and make their collaboration more efficient and effective.

  A comprehensive and detailed as-built documentation (Annex E), manuals and procedures (Annex C “Documentation set accompanying the solar PV plant” of the O&M Best Practice Guidelines) should be part of the training activities. For more information on the handover to a specialised O&M service provider, please refer to Chapter 10 on Handover to O&M.