What is solar energy?

Solar energy technology

The are 2 main types of solar energy technology:

• concentrated solar thermal (CST)
• solar photovoltaic (solar PV).

CST uses a field of mirrors to reflect sunlight on to a receiver, which transfers the heat to a thermal energy storage system.

Typical solar PV cells are covered in glass and protected by aluminium frame, collectively known as a solar panel. The panels can convert sunlight directly into electricity.

Solar PV is currently the most used solar technology in Queensland.

Technology is improving, with flexible solar PV roof tiles now available and solar paint in development.

Efficiency and reliability

The efficiency of solar PV (how much solar energy is converted into electricity) depends on the types of cells. Monocrystalline cells and polycrystalline cells are very efficient.

As they don’t have any internal moving parts, solar panels are generally reliable and low maintenance, but their output (efficiency) depends on a few factors, including:

• location
• size
• installation.

Queensland has more than 300 days of sunshine every year, but solar panels don’t need direct sunlight to work.

Even on a dark, cloudy day, colours reflected from the sky are absorbed to create 10–25% of their normal output.

For maximum efficiency and reliability, solar panels should not be placed in shade from trees, buildings or other structures.

Recycling

Up to 95% of the materials used in a solar panel can be recycled.

Silicone solar panels primarily consist of plastic, glass and aluminium, all of which can be repurposed in large volumes.

The Queensland Government and Smart Energy Council is developing an Australian-first pilot program to best recycle PV solar panels. The program will investigate collection and disposal of unwanted residential, commercial and large-scale solar panels.

Rooftop solar

Queensland has the highest rate of household solar installations in Australia, with 1-in-3 homes using solar.

Altogether, more than 830,000 small businesses and homes now have rooftop solar.

The collective power of small-scale solar is important in helping us reach our renewable energy targets. On average, over 150 new rooftop PV systems are installed across Queensland every day.

Learn more about installing solar in your home.

Cost benefits

The cost to install a solar PV network can be offset within 4 to 7 years by not having to pay traditional power bills. Households may also be eligible for interest-free government loans for installation.

These benefits don’t take into account government rebates or subsidies for households and small businesses, which represent a huge saving over a rooftop system’s 25– to 30–year lifespan.

Maintenance and lifespan

Solar panels don’t contain moving parts, which means you don’t need to do anything special to keep them running.

Most quality solar panels are designed to be self-cleaning in the rain. Dust, debris and bird droppings can accumulate when there hasn’t been rain and reduce the amount of electricity produced.

The general recommendation is to have your panels cleaned by a professional once a year.

The average lifespan for a rooftop solar PV system is 20–30 years with proper maintenance. Near the end of a panel’s life, its efficiency can drop by 12–15%. The inverter responsible for converting Direct Current (DC) from the panels into Alternating Current (AC) may need replacing after 10–15 years of use.

Solar farms

A solar farm is another name for a large group of solar panels converting solar energy into electricity.

Many solar farms use similar panels to those on home roofs across Queensland. The main difference is the size and number of panels. Solar farms have the room to host more panels and therefore produce large volumes of electricity.

The output of a solar farm can range from 5 megawatts (MW) to several hundred megawatts.

Required land size

Approximately 2–3 hectares of land are needed for every megawatt of solar power capacity.

The ideal sites for large solar farms have:

• lots of sunlight
• flat, stable ground
• a low risk of flooding
• lower ecological and agricultural value.

Developing large-scale solar farms can require varying levels of land clearing and grading. Any impacts to the local environment must be carefully managed and mitigated according to the development approvals process.

Grid connection

The low-voltage DC electricity produced by PV panels is passed through onsite inverters and transformers to produce high-voltage AC electricity.

This AC electricity is then exported to the grid, therefore solar farms need to be close to grid connection points such as a local substation or overhead transmission line infrastructure.

Agriculture

Land that is more compatible for a solar farm is often less compatible for farming. However, there are many solar farms being trialled on agricultural land across Australia.

In some cases, grazing livestock and solar farms may be a good match and successful trials are underway with sheep grazing.

Solar farm land can also grow low-lying, deep-rooted plants, grasses and flowers that rebuild the soil. These plantings can support honeybees, butterflies, hummingbirds, and other pollinators.

The Queensland Government and Queensland Farmers Federation developed the Queensland Renewable Energy Landholder Toolkit to help landowners make informed decisions.

Land use after a solar farm

At the end of a solar project’s 20– to 30–year working life, there are 3 common options:

• continue operating the solar farm using the existing infrastructure
• upgrade the solar farm with the latest technology
• decommission the site by removing the solar infrastructure and remediating the land.

The decommissioning of a solar farm involves the recycling and repurposing of materials, including the solar panels.

Land can be reverted to agricultural uses once a solar farm is decommissioned. The 20– to 30–year working life of a solar farm can provide a recovery period for agricultural land.

More information

• Learn about other renewable energy technologies that make up Queensland’s SuperGrid
• Solar for your home
• Solar for small-to-medium businesses