Feature

Guide to solar panels

G Magazine

Tapping into the sun’s energy to power your home is as green as it gets. G magazine runs through what to expect and how to go about buying solar panels.

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One of Conergy’s polycrystalline panels.

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BP’s mono-crystalline panel.

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A polycrystalline panel by Kyocera.

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Sanyo’s new hybrid panel.

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Solar panels have the ultimate green credentials, and gone are the days when you needed to pay tens of thousands of dollars to catch the sun. With government rebates and increasing demand, solar panels have moved into the realm of possibility for the average homeowner.

Once installed, panels can generate pollution-free electricity from the sun for 25 years or more. Even manufacturing them takes relatively little energy. According to Martin Green, executive research director of the Photovoltaics Centre of Excellence at the University of NSW in Sydney, “the energy payback is less than three years, even less for thin film”.

As well as protecting you from electricity price hikes, installing solar can give you that feel-good experience of helping to reduce demand for peak electricity loads in summertime. Assuming you install a 1.5 kW system, it will also save about three tonnes of carbon dioxide per year, a similar amount to the emissions produced by driving a car for 40,000 km. So what are you waiting for?

Here’s G’s guide to get you started on your solar panel journey.

What are solar panels?

Solar panels consist of modules that are put together in an array (an arrangement of rows and columns). Modules are made up of solar cells. There are basically three main types of solar cells on the market: monocrystalline, polycrystalline and thin film.

Ninety per cent of solar cells are made from crystalline silicon. Monocrystalline cells, made from a single silicon crystal, are the most efficient, with the brand Sunpower leading the way with efficiencies of up to 18.1 per cent. Polycrystalline cells are made from many silicon crystals and, while less efficient than monocrystalline, they’re catching up – Kyocera have panels on the market with efficiencies of 17.5 per cent. Polycrystalline cells are also generally cheaper than their mono counterparts.

Capturing about 10 per cent of the market is thin film technology. Thin films are also called ‘amorphous’ because the silicon doesn’t form crystals. Made by brands such as Kaneka and Uni-Solar, this technology is significantly cheaper to manufacture than alternatives because it uses one tenth of the silicon compared with crystalline cells. This also means less energy is required to make the cells. The efficiency of the final product is, however, only 7 to 10 per cent, so they require up to two-and-a-half times the roof area to produce the same amount of energy as crystalline panels. Thin film panels are therefore less useful in inner city areas where roof space is at a premium. They are well suited to hot and partly shaded conditions, though, whereas crystalline cells are more effective in cold conditions.

Newest on the market is hybrid technology, such as Sanyo’s HIT panels, which have module efficiency of 16 per cent. Hybrid technology consists of a thin monocrystal wafer surrounded by amorphous silicon. The big advantage of the Sanyo HIT panels is that, unlike crystalline panels, their function is not hindered in high temperatures.

Is my house suitable?

The basic requirement for installing solar panels is an unshaded, north-facing roof. According to the Clean Energy Council, panels need to be installed at the same angle as the latitude where you live. In Sydney, for example, this is 22 degrees, which is also a common roof pitch. If your roof is not at the correct angle, panels can easily be installed on a frame.

The roof also needs to be large enough to fit the panels. Danin Kahn, chief eco officer of sustainable retailer Todae, says a 1.5 kW system will take up 8 m x 1.5 m of roof space. While quite achievable for a large suburban house, this can be a squeeze for a tiny inner-city terrace. In this situation, Kahn recommends installing high-efficiency panels such as those made by Sunpower, which provide significantly more power per area.

Installing panels in apartments is even more difficult, although not totally impossible. It depends on roof access and support from the body corporate. Kahn has heard of apartment blocks that have installed solar panels to power communal areas, and he also knows of a case where an individual owner was able to convince the body corporate to allow him to install panels for his own personal use. Kahn also once had a woman purchase a single panel that was simply propped against a chair on the particularly sunny verandah of her apartment, allowing her to power some of her appliances sustainably.

How many panels will I need?

The ideal scenario is to be self-sufficient in energy, although your ability to achieve this will depend on your current energy consumption, roof size and how much money you are prepared to spend. The effectiveness of the panels also varies depending on where you live – Darwin and Adelaide get 30 per cent more sun than Hobart and Melbourne.

The average Australian home uses about 20 kW of electricity per day. A 1-kW system provides about 4.8 kWh per day (depending on location), which means to be self-sufficient you would need a 4-kW system costing a hefty $43,000. Even with government help it’s prohibitively expensive!

It makes far more sense to work on minimising your household energy use first, before you draw power from your solar panels.

Solar panels cost about $11 to $12 per watt before rebates. From 30 June 2009 the new solar credits scheme is expected to provide about $7,500 per 1.5 kW system. Feed-in-tariffs may also substantially reduce your overall cost, again depending on where you live (see G issue 20, p26).

Suburban environmentalists Alison Mellor and Richard Walter recently went through this process for their two-person home in Wollongong, NSW. They found they could get their energy use down to 2.5 kWh per day after installing solar hot water and insulation and making other changes. This meant they only needed a 1-kW system, which cost an affordable $4,400 after rebates. Now they feed energy into the grid because their system produces twice as much as they need.

Plug your yearly electricity costs into this handy little solar panel calculator. You’ll find out how many panels you need, how much energy it will save and approximate cost of the system.

Grid connected versus stand-alone

Solar panels can be connected to the grid, in which case you won’t need a battery. A grid-connected system consists of PV modules, a meter and an inverter. The panels create DC electricity, which is converted (by an inverter) to AC electricity. You need AC electricty to be able to run appliances. A meter allows you to measure how much electricity you generate versus how much you buy back from the grid at night.

Few people realise that grid connection means that during a blackout your system will also lose power because it will be automatically turned off for safety reasons. If you want uninterruptible power, a battery system is required, which will substantially increase costs and maintenance. Angus Hawke, manager of renewable energy at Enviro Friendly Products, recommends installing a diesel generator as a back-up instead.

If, however, you live in a remote area you’ll want a stand-alone system. Remote users will need a battery to store energy, a back-up system and a solar regulator, which controls the amount of charge going into the batteries to prevent them from being overcharged. Installing solar panels in remote areas is usually very cost-effective when compared with paying to connect to the grid, even factoring in the additional costs of batteries and back-up systems.

Which model?

How do you choose a solar PV system now there’s a bewildering array of brands and suppliers? John Payne, director of Enviro Friendly Products, says “it’s advisable to go with established companies and brands.” He also cautions that “if the offer is too good to be true it probably is”. Payne advises consumers to read the terms and conditions carefully, and check if the warranty is based in Australia and what happens if you want a refund. The module should also meet Australian standards.

Hawke recommends choosing an operator who will carry out a site inspection in person. He says some operators rely on Google Earth to check the property, potentially missing tree shading or a neighbour’s renovation.

How to get the panels installed

After you’ve chosen your panels you’ll need to find an accredited installer. “It’s very important to get correct installation because there is a potential for fire or electrocution if it’s done incorrectly,” Hawke explains.

However, just because they are accredited doesn’t mean they are good. “I would always ask to see few examples of an installation,” Kahn says. Hawke agrees. “You want to know if the installer left ugly holes in the roof!”

It’s also worth talking to your energy retailer. Walter says he “had a few hiccups with the energy company” – they didn’t read the meter. “Next time we would contact the energy company directly and let them know we had installed solar panels”.

Finally, don’t forget to obtain approval from your local council before installation, especially if you live in a heritage area.

Resources

- List of accredited installers
- Solar panel calculator
- Detailed booklet on photovoltaics
- Richard and Alison’s blog
- Bulk Buying Schemes

Solar panel manufacturers

Monocrystalline
- BP Solar
- Sharp
- Siemens
- Sunpower

Polycrystalline
- BP Solar
- Kyocera
- Sharp

Thin film
- Global Solar
- Kaneka
- Sharp
- Uni-Solar

Hybrid
- Sanyo