SOLA4012 2025

Commercial PV project

1 Scope summary

You are a graduate engineer in a large engineering department of a well-known PV installer (SPREEnergy). The company has received a tender request from a large retailer, for the installation of a non-exporting, grid-connected PV system for their commercial buildings around Australia, with an energy storage option. You will have to find a suitable warehouse from the retailer somewhere in Australia and produce a full system design for the tender response. Your design needs to comply with all relevant safety and performance standards, and it needs to go through a thorough techno- economic optimization to ensure optimal financial and technical performance. A summary of the tender requirements can be found below.

2 Compliance and tender report summary

The project incorporates a roof mounted grid-connected PV system, with no grid export  (non- exporting system), that must comply with all the requirements from the Clean Energy Regulator (CER) and Solar Accreditation Australia (SAA), to be eligible for the creation of  Large-scale Generation Certificates (LGCs) or Small-scale Technology Certificates (STCs) depending on the final size of the system. The layout of the PV array must be designed to:

- Maximise the system capacity (trying to achieve a minimum size of 100 kWdc),

- Maximise the annual yield within the roof space available (avoid self-shading and shading, and good ventilation of the PV modules must be ensured), and

- Minimise the levelized cost of electricity.

You are fully responsible for all design matters of the system and selection of components, including the PV modules, support structures, fixings to existing roof sheeting, DC cabling from PV panels to inverters, cabling to the building distribution boards, earthing, and protections. Easy access to all PV panels is essential, to allow for cleaning and maintenance, by means of clear access corridors. The panel layout also must allow for continuous access to the existing perimeter roof gutter system.

The system must be suitable for connection to the low voltage distribution system of the building (400/230 V, 3 phase, 50Hz). The inverters are to be installed in a suitable room on the ground floor (from now on the ‘inverter room’). The proposed point of grid connection is the building Main Switch Board (MSB), located on the ground level, next to the service area (usually close to loading docks).

The existing service riser and cable trays can be used to route the cables from the roof to the MSB. The MSB has available circuit breaker spaces for the connection of the PV system; however, the designer must size and select the circuit breakers adequately.

As this system will be installed by SPREEnergy, your design must adhere to the Design and

Construction guidelines for PV systems (section E3.5) as described in this LINK. You will receive a year of interval load data for the building:

•    You must fill any missing data with appropriate methods.

•    You must scale this load data to achieve an energy intensity of 240 kWh/m2/year before using it.

• You will use this data to size your system for both design options (with and without storage).

2.1 Battery Option

First part of the design will include PV only option. After completing the PV only design option, you must also provide an additional design option that includes battery storage. The storage option might allow the installation of a larger PV system as any excess energy can be used to charge the battery but, the system must not export energy to the grid. Notice that a different selection of inverter might be necessary to allow for energy flow between the building, the PV system, and the grid. The preferred battery chemistry is Lithium-ion due to the number of cycles and high DOD levels that can be achieved. You must select the size and model of the battery that provides the best economic benefit to the owner of the system. You must also estimate when a replacement battery is required. Unfortunately, SPREEnergy does not have current battery prices, so you will need to do some cost investigation for lithium-ion batteries.

The battery system installation must comply with all relevant  Australian  Standards  (including AS/NZS 5139: 2019) and be able to supply energy to the three-phase electrical system of the building. The battery inverter/charger must comply with the same conditions as the solar inverter.

2.2 Economic Assessment

SPREEnergy has asked you to produce a design that offers the lowest Levelised Cost of Electricity (LCOE) and highest Net Present Value (NPV) for each option (with and without battery storage) in order to win the tender. Assume a life span of 25 years for the PV system, but bear in mind that some components might need replacement over that period. The capital investment of the system is important but secondary. The electricity tariff structure for the building is shown in Table 1.

Table 1 – Customer Electricity Tariff

To calculate the direct costs of your system, SPREEnergy has provided you with  the values presented in Table 2. The tender specifies an inflation rate of 2.4% and a real discount rate of 7%.

Table 2 - Approximate costs of components and installation

PV module 22% efficiency               0.80 $/Wdc

Engineering & Installation              0.32 $/Wdc

The final cost are the direct costs plus the profit margin. As part of the tender, you must prepare a project installation plan including timeframe, activities, and milestones (a Gantt chart is preferable).

2.3    Model, Assumptions, and Drawings

You must explain all your decisions (for example component selection, design parameters and selection), list all your assumptions (for example module degradation) and quote all your reference sources (for example data sheets). The objective of this project is to present a comprehensive design of the system to submit a good tender, which must include ‘workshop drawings’ containing the full design of your system (panels per string, strings per MPPT, protection, switches, cable lengths, voltage drop, etc.). In other words, a contractor should be able to build the system if you give them the report.

The compliance part of the report will focus on the correctness of the design in terms of matching and selection of components, safety, estimated costs, and agreement with the Australian Standards. You must provide calculations showing how your design adheres to the Australian Standard.

The techno-economic optimisation part of your report will require using one of the available PV simulation software  like  PV-Syst, SAM,  Helioscope etc. and  running  many simulations varying different system variables for with and without storage design options to optimize the LCOE and NPV.

The workshop drawings consist of PV system design outline drawings and single line diagrams (SLD) which must include designs for both with and without battery options.

2.4 Performance Guarantee

The design must include a guarantee of the yield output for the first five years. You must include an estimation of the expected the power output over the lifetime of the system (25 years) and a methodology to compare the expected output to the measured output.  You must specify the metering and monitoring option, including weather conditions if necessary.

3 Compliance and Tender Format

The main body of the report should have a maximum of 11 pages plus appendices. The appendices should include a full set of technical drawings and data sheets for all the components used in the design.

Your system design must include all the aspects required for a system compliant to Australian Standard:

• Selection of components (PV, inverter, frame, protection, etc.)

•   Sizing of all components including cables and protection, and calculation of voltage drops (this will be delivered as an excel input sheet).

•    Lightning protection assessment.

•   Wind load assessment.

•    Drawing with the physical layout of modules, inverters, wiring, switching and protection gear required by AS/NZS5033, including earthing and lightning protection.

In addition, the report must include techno-economic optimisation for the chosen system variables for with and without storage design options.

The report must include the following sections:

1.   Executive summary (1 page max)

2.   Project context, site and weather assessment

3.   Summary of selected system design with and without battery

4.   System design and calculations  (compliance,  includes Excel Design Spreadsheet to be submitted separately)

5.   Techno-economic optimisation

6.   Lightning and wind load assessments

7.   Estimated cost, financial parameters and performance

8.   Project plan

9.   Performance guarantee

10. Conclusion and recommendations

11. Appendices

a.   Tender return forms (see this document appendices)

b.   Workshop drawings (single line diagrams and system layouts)

c.   Data sheets and warranties.

d.   Others (if necessary)

Note: The Engineering Manager is very strict with the number of pages for the main body of the report and will not review any information beyond the specified limit. The purpose of this is for you to decide what’s relevant and to show your work and results in a concise way.