# Photovoltaic system design: procedures, tests and component sizing (Part 2)

## Photovoltaic system design: procedures, tests and component sizing. The advantages of photovoltaic system design using a software

In this follow-up article we’ll be seeing the design criteria behind PV system sizing and how the various components are checked in terms of compatibility.

### Calculation procedures

The design principle is essentially based on a very simple requirement and that is to capture as much of the available annual solar radiation as possible.
Exposure of the PV generator according to the optimum exposure is a major factor. In general, the photovoltaic generator should be positioned prioritizing the south orientation (north if the PV system is located in the southern hemisphere) and should avoid the effects of shading by nearby objects. Other aspects also involve evaluating the architectural characteristics of the building in relation to the PV generator power requirements. Appropriate orientations and shadowing phenomena are allowed, provided they are adequately monitored during the design phase.
Energy losses due to these phenomena affect the cost of the produced kWh and the investment’s pay back time.

When considering a Building-integrated photovoltaics (BIPV) system, where modules can be smoothly integrated into the building’s design and construction constraints, generator orientation and inclination is directly linked to these surfaces, for example, the building’s roof top. The great advantage is that these installation solutions, also aesthetically pleasing, can be seamlessly integrated into the building envelope to give it a sleek, modern look.

### Criteria for estimating produced energy

The generated energy therefore depends on the following factors:
• installation site (latitude, available solar radiation, temperature, effects of surface reflection in front of the modules)
• module exposure: Tilt angle and orientation (Azimuth)
• any shading or deterioration of the photovoltaic generator
• module characteristics: nominal power, temperature coefficient, decoupling or mismatch losses
• BOS characteristics (Balance Of System)

### Photovoltaic system design: configuration and sizing

Example of a PV system installation

In order to size a PV system correctly, we’ll start off from the basic data such as:
• client data (name and address)
the site’s:
• latitude (North, South)
• longitude (East, West)
• altitude (m)
• annual solar irradiation on a horizontal plane (MJ/m²)

and the building’s technical data:
• total surface area (m²)

• energy per kW (kWh/kW)

• total number of modules

• BOS (%)

• total number of inverters

• phase power (L1-L2-L3) (kW)

• total annual energy (kWh)

• energy accumulation system

• total power (kW)

• useful accumulation capacity (kW)

External storage system

The external accumulation system allows storage of excess energy from the PV production system or generator, to be reused when the generator isn’t producing enough energy.
This important aspect also requires attention in order to define the battery type (code, brand, model, and electrical characteristics) and the storage system configuration.

Landscape scenario with PV system in foreground

### What are the advantages of designing a PV system with a software?

Using a software to address professional PV systems design allows the user get an accurate evaluation of solar photovoltaic panels energy output base of the location’s solar irradiation data and exposure.
Here we have listed some of the major advantages that can help to analyze the best possible design solution, in terms of energy efficiency and financial benefit, when using Solarius-PV a software developed and distributed by the Italian based software company, ACCA software S.p.A.
Definition of the avaialble installation surfaces using specific graphical objects assigned with the relavant technical specifications necessary for system sizing, or directly imported from a traditional DXF/DWG CAD file.

PV module positioning for installation on roof tops or on ground surfaces automatically selected by the software from an extensive library of makes and models produced by worldwide manufacturers.

Photovoltaic shading simulation produced elements at the horizon and located at a given distance from the photovoltaic system. An integrated shading analysis that evaluates these effects on the PV system’s energy production capacity from a simple photographic survey of the site.

PV System configuration with single-phase and three-phase inverters in low voltage (LV) and medium voltage (MV), multiple MPPT inverters together with inverters using built-in or independent energy storage capacity (external photovoltaic batteries). Photovoltaic batteries and inverters are automatically selected and recommended by the software in order to obtain the best possible energy production rate.

Photovoltaic system efficiency calculation (total annual output with time-period based production details) and profitability assessment with the photovoltaic system’s amortization period.

Calculation results, in numerical and graphic form, with dynamic updating of any changes in project data. Full support with an integrated diagnostic tool that quickly detects any design errors.

Scene photo-simulation tools for producing precise visual impact assessments.

Here are a few screenshots of the Solarius-PV interface.