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Solar Panels, Solar Inverters and BOS

A Solar System is not a Plug and Play Appliance

Each core component can affect the performance and the system’s lifespan. A system can be broken down into three components: Module, Inverter and Balance of System (BOS) as well as two delivery mechanisms: the retailer and the installer. All of these factors need to be selected carefully to ensure you get the right system for your energy needs, your budget and your home.

Panels

There are predominantly four different types of panels available for residential applications each with different efficiencies and characteristics. It is important to remember not all panels are capable of performing adequately in the challenging Queensland conditions.

Main Type of Solar Panels

Monocrsytalline Panels – These panels have the highest efficiency and also the highest cost of production. The solar panel is made out of a single crystal of pure silicon which is called monocrystalline. Monocrystalline panels get their name from the fact that the silicon wafer used to make them is cut from a single crystal or ‘boule’ of silicon. Silicon is grown in a laboratory to achieve a high degree of purity and is then sliced very thinly to make wafers The cell efficiency of this type of panel can vary between 18% to 24% for the normal monocrystalline silicon technology. Due to higher production costs, monocrystalline cells are more expensive than other cells. Monocrystalline cells don’t perform as well as polycrystalline cells or thin film under higher temperatures (e.g. 25°C +). All cells are subject to ‘de-rating’ as the ambient temperature increases, and monocrystalline cells tend to produce less at higher temperatures than the other technologies.

Polycrystalline Panels –These cells are cut from an ingot of melted and recrystallised silicon. In the manufacturing process, molten silicon is cast into ingots of polycrystalline silicon, then saw-cut into very thin wafers and assembled into complete cells. Polycrystalline cells (also known as multicrystalline) are cheaper to produce than monocrystalline ones, due to the simpler manufacturing process. However, they tend to be slightly less efficient for the same size cell. These panels have an efficiency of between 13% to 17%. Polycrystalline cells typically offer a lower cost per watt of power produced. These cells have a better temperature de-rating co-efficient compared to monocrystalline, meaning they produce more power in hotter weather, which usually more than offsets their slightly lower cell efficiency. Polycrystalline cells are slightly less efficient than monocrystalline cells, so they need more roof space to produce the same output capacity

Amorphous Silicon – Amorphous silicon (a-Si) is related to the polycrystalline family. Thin film, or amorphous, silicon cells are made up of silicon atoms in a thin layer rather than a crystal structure. Amorphous silicon can absorb light more readily than crystalline silicon, so the cells can be thinner. For this reason, amorphous silicon is also known as ‘thin film’ photovoltaic (PV) technology. The difference is the amount of silicon being used and how it is used. Amorphous silicon uses a fraction of the silicon that is used in other panels. The cost of the panel is lower and although the panel’s space efficiency is the lowest of all the technologies. Don’t be put off by this! The high quality thin film amorphous panels hold their own in the important measure of kWh out for kWs installed. If you have the roof space these are a great option. The bonus to having more panels on the roof is the reduction of transferred heat through to your home.

Hybrid Panels – A hybrid panel has a dual-layer structure of microcrystalline and amorphous silicon. The panels have a higher efficiency of power generation than the standard amorphous silicon panels.

Inverters

The differences between transformer and transformerless TL inverters are:Transformer inverters are built with an internal transformer that synchronises the DC voltage with the AC output. This type of inverter is heavier and produces more heat in comparison to TL inverters.

Transformerless (TL) inverters use a computerised multi-step process and electronic components to convert DC to high frequency AC, back to DC, and ultimately to standard-frequency AC. TL inverters use electronic switching rather than mechanical switching the amount of heat and humidity produced in comparison to standard inverters is greatly reduced.

TL inverters maintain the unique ability to utilise two power point trackers which allow installations to be treated as separate solar PV systems. In other words, with TL inverters solar PV panels can be installed in two different directions (i.e. north and east) on the same rooftop and generate DC output at separate peak hours with optimal effects.

Note - Inverter efficiency is determined by the percentage measurement of energy convergence (i.e. the closer to 100% of DC to AC convergence for the longest amount of time the more refined inverter efficiency).

A micro inverter converts direct current (DC) electricity from a single solar panel to alternating current (AC). Micro inverters have several advantages over traditional inverters. The main advantage is that, even when there are small amounts of shading on any one solar panel or a panel failure, this will not disproportionately reduce the output of an entire array. Each micro-inverter obtains optimum power by performing maximum power point tracking for its connected panel.

Balance of System (BOS)

The Balance-of-System or BOS is a critical part of a solar system and is the least talked about or considered component, often left up to the discretion of the installer and their budget. The BOS is 1/3rd of a PV solar system and accounts for the majority of maintenance and servicing requirements.

BOS refers to the mechanical and the electrical components that secure the system to your home and the components that transport, control and isolate energy produced by solar panels through to the inverter and distribution mechanism (sub-board/switchboard) for both the AC and DC side of the installation.

The mechanical component relates to the mounting of the system, fittings and fixtures. The electrical component relates to the cables (AC, DC and Earth), switches and breakers (AC and DC), enclosures (AC and DC), plugs and connectors, cable protection as well as module and frame earthing components.

The BOS also includes the components that connect and control the system within the distribution mechanism. The components and their application can have a serious affect on a PV solar system’s performance. BOS applies to all types of solar installations.

If you are unsure about the quality or safety of your system, contact us today to arrange an inspection and safety audit.

There are a few basics that should be adhered to if you are buying a system

  1. Shop for quality and not price you get what you pay for in this industry.
  2. Ask the tough questions and check the facts.
  3. Know what you are buying – panels – Inverter - BOS.
  4. Know who you are buying from and who is installing it.
  5. Don’t rely on retailer warrantees as some very large solar icons have fallen over the past few years and so to have with their warrantees.
  6. There have also been manufacturers that have exited the industry both in the panel and inverter markets.