A solar photovoltaic (PV) system is a small scale power generation plant and can be a complex electrical system. The voltage of a domestic system can be up to 600 volts d.c., a potentially lethal level, so it is extremely important that design is optimised and installation is to best practice standards.
The essential operation of a PV system, however, is reasonably straightforward. On this page we will examine:
- Basics of a Solar PV System
- Grid Connect, Off Grid and Battery Back-up Systems
- Tariffs and feed-in tariffs
- Considerations in a Good Choice of Solar Power
- Frequently Asked Questions
Basics of a Solar PV System
Solar panels have a silicon structure which undergoes a chemical reaction when photons from the sun pass through the panel. Each such reaction causes an electron to move creating the electrical current that passes from the panels.
Note that it is not heat, but radiation that is causing the reaction. In fact, lower temperature are better for maximum output from solar cells.
The panels are wired together into ‘strings’ and the resulting collection of panels is known as a PV array.
The array cables run to a rooftop junction box then on to a disconnecting switch located next to the inverter, the next stop for the signal. The job of the inverter is to take the direct current (d.c.) and convert it to the same 240 volt alternating current (a.c.) signal that is used throughout the home for common appliances.
The a.c. current flows on through another isolating switch to the electrical switchboard. Here the power is available to be used in the circuits within the house or, if not required on site, this power can be exported to the electricity grid, earning you a credit on your bill.
Grid Connect, Off Grid and Battery Backup
There are three distinct types of domestic solar PV installation. The one described above is the most common – a grid-connected PV system.
A grid connected system synchronises the PV power to match the mains electricity, however it can not operate when the grid power is not present. So a power failure on the grid means the property still has no power.
Grid-connect solar power means that you can generate your own clean energy and feed it back to the electricity grid. The surplus that you feed back will be credited against what you have purchased and thus save you money.
In order to maintain power when there is a grid power outage, the above system must be supplemented by a battery backup or storage system.
This on-grid battery backup system has the best of both worlds.
In addition to making the system an ‘uninterruptible power system’ (UPS) there is an additional benefit to battery backup when connected to the grid. When feed-in tariffs paid for solar power exported to the grid drop to the low rates that they have – well below the tariff paid for power from the grid – there is little incentive to generate power to export it.
A better option is to store that power in a battery bank when the sun is shining and to use that power in the evening rather than drawing power from the grid.
The third alternative is to power your house entirely independently, and this is known as an off grid or standalone power system (SPS). A stand alone power system is commonly installed where access to the grid is difficult or expensive.
In this type of power system the battery storage must be sufficient to maintain the household power usage even in winter months when there is limited solar radiation and no sun over a number of days. This system will generally include a diesel or petrol generator to recharge the battery bank.
Read more on off grid power systems.
Tariffs and Feed-in Tariffs
The price that your solar-generated power is sold at depends on your power retailer and the agreement you sign with them.
In recent years generous government subsidies in some states meant feed-in tariffs paid for exported solar were well above the rate paid for grid power. The feed-in tariff varies state to state and to a smaller degree between electricity retailers, but is now paid at a much reduced rate.
Currently in Victoria all energy retailers must offer you a minimum feed-in tariff of just 8 cents per kilowatt hour (kWh) for energy exported from your home. With retail rates commonly three times this tariff the incentive to generate power and export to the grid has diminished rapidly.
Considerations in a Good Choice of Solar Power System
Now let’s look at some of the factors to consider when deciding, if, when, and how to choose and install a solar PV power system.
Location
The ideal mounting surface for solar is a north-facing roof with no shading from trees of other buildings. If a house is not oriented to provide this, a roof with a more easterly or westerly aspect may be quite suitable.
Shading can have a significant effect on the output of the solar PV system. If you have a shaded roof surface an assessment of the impact of this shading will be required and the system will be designed to suit, or an alternative location may be discussed.
Other Mounting Factors
There are two reasons to confirm that a roof surface is in good condition before installing solar panels. Firstly the roof must provide strong structural support for the solar panels in all weather conditions. Secondly, if repair or painting is required to a roof later on, it is costly to remove the solar array (the array is the collection of interconnected panels).
The most common mounting technique is to fix a racking system to the roof battens and then to mount the modules on this rack in rows. The modules are then about 150mm off the roof surface allowing them to be well ventilated thereby reducing the temperatures of the solar cells. This means the system will perform most efficiently.
When a roof is flat or on a slight angle, it may be preferable mount the array using ’tilt frames’. Tilt frames are a mounting system that sets the panels on an higher pitch then the roof.
The ideal pitch or inclination of the panels depends on the latitude of the location. A system can be designed for best performance at a particular time of year or for best overall performance throughout the year.
When a system is not connected to the grid it is generally designed for best performance in winter when the sun tracks lower in the sky. For grid connect solar systems, the ideal tilt angle may also be affected by your energy usage patterns in different seasons.
Performance
The estimated production of a power system should be calculated and provided to you before you commit to installation. These performance estimates are calculated using solar radiation data for your location, adjusted for the orientation and inclination of the solar array, as well as being adjusted for the location temperature averages and other impacts on system efficiency.
As mentioned above, lower temperatures allow for higher output for a solar PV module. The power is produced by radiation rather than heat. So performance adjustments are made for the temperature averages for each month of the year.
Other factors include losses to performance due to the length of cable runs, conversion efficiency losses in the inverter, the affect of dirt and dust on the modules and the gradual reduction in output of the modules over their many years of service.
Switchboard
It is important that a check is made on your electricity switchboard prior to installation. In some cases, electricity meters or even the whole switchboard may need to be replaced. We believe you should be fully informed before you commit, so organise a site visit to check on any potential issues.
Price
As the saying goes, “Compare apples with apples”. Many discount solar power companies offer systems at rock bottom price. There is always compromise in this business model.
SolarQuip will not compromise safety as we work to ensure you have system components and an installation that will last the test of time in Australia’s harsh conditions. Cheaper components can easily be damaged by the effect of exposure to sun, wind, water and even fauna.
We will work with you to provide the best performance and overall clean energy solution according to your individual situation and requirements.
Frequently Asked Questions
3. How can I estimate how much solar energy can be generated from my roof?
4. Can I expect to meet my power needs with renewable energy?
5. How long will it take to recoup my investment in a solar power system?
6. Solar power seems complicated. What will I need to do to look after this system?
7. How will I know how much power my solar system is producing?
1. I’m not sure what I should do first to improve the energy efficiency of my home. Is a solar PV the first step?
Installing solar power is just one of the actions you might be able to take to minimise your carbon footprint, along with purchasing “Greenchoice Power” from your retailer and taking basic steps to improve your lifestyle sustainability. Whilst we are very happy to design and install your solar power system, we want to see you have the best possible outcomes. Please look at the following simple Home Sustainability Guide, before deciding that solar power should be your first priority.
1. Consider solar hot water. An electric hot water system can consume up to 40-50% of your total electricity use. Even gas water heaters still have a serious greenhouse gas emission footprint, and solar should be your primary water heating approach. An electric heat pump may alternatively be more suitable for your site, if you have limited solar space available, or there are other factors.
2. Avoid electric heating where possible. Electric heaters are a big power bill item. Especially avoid the small “bar” electric heaters for area or space heating. Put all electric heaters on timers, and make sure you only use them when necessary.
3. A well-insulated house requires far less heating and cooling. Check that your house has appropriate roof and wall insulation and minimise drafts, especially around windows and doors, and through bathroom and kitchen exhaust fans. Make sure you use curtains and blinds, and pelmets over windows. Close doors to create “warm zones” and leave unheated, rooms that you don’t use. Think about double glazing for at least the southern and weather-facing windows.
4. In summer, consider regular opening and closing of windows and doors to encourage purging of warm air from the home, before turning on the air conditioner. Plant deciduous trees, shrubs and wall climbers to provide summer shade and winter warmth. Use external blinds in preference to internal curtains to keep out the sun.
5. Fridges and freezers can consume a lot of power. A low cost plug-in energy meter is a good way to check the power consumption of appliances and stand-by items, like wall-chargers. If replacing, look for appliances with a high energy Star Rating, and low stand-by power consumption.
If you feel you’ve covered these bases well, solar power is likely to be your top priority in your path to an energy efficient home and more sustianable lifestyle. Every home solar system is one step closer to energy self-sufficiency. It’s also further away from highly polluting coal-fired electricity generation and a step towards a clean energy future for Australia.
2. How can I be sure I’m getting good quality solar panels and inverter, and a safe system installation?
Australia is fortunate to have an industry standards committee working to ensure the safety and confidence of consumers. Our principal, Glen Morris, is a member of the Standards Australia EL-042 committee, helping to promote world’s best practice in the renewable energy sector and safeguards for everyone.
Despite this degree of protection, customers must ensure their installer is applying these standards to be sure of meeting the criteria for safe, durable installations and to access government rebates.
SolarQuip uses only solar panels that meet international standards (classified as Class A modules meeting safety standard IEC61730). Inverters used in grid-connect systems have a Certificate of Suitability and comply with AS 4777 (.2 & .3).
SolarQuip is accredited to design and install off-grid, stand-alone (remote, also known as SPS) and grid-connect (GC) photovoltaic power systems. Some cusdtomers are even thinking about using a small, addtional battery back-up system to be charged by their on-grid system, further reducing their dependence on expensive grid power.
Please visit our ‘About us’ page to see our company profile, track record, and customer reviews.
3. How can I estimate how much solar energy can be generated from my roof?
We highly recommend a SolarQuip site visit to assess the likely output of your future PV solar system.
The maximum rooftop potential can be roughly estimated using a web-based tool such as ‘Roofray – http://www.roofray.com/calculator’ (as this is designed for northern hemisphere, you’ll need to change the orientation by 180 degrees to get potential PV output in the southern hemisphere).
Ideally the panels will be north-facing, roof or ground-mounted. They should be tilted (maybe at up to the latutude angle) to maximise exposure to the sun – although the optimal tilt angle can be quite different, depending on whether the installation is grid-connect or remote, seasonal variations and many other factors.
Shading from hills, trees or nearby buildings can severely affect your solar potential. SolarQuip’s site visit will identify these problems, and we are certain that we can provide you with the best solutions due to our extensive experience and a wide range of quality components avilable to us.
4. Can I expect to meet my power needs with renewable energy?
SolarQuip aims to help you meet all of your household needs as well as ultimately generating power to put back into the grid when your usage is low, thereby making you a little return on your investment. However, there are a few things to consider. To cover all of your electricity use may require quite an investment, which is why we encourage people to think about their daily energy consumption and energy efficiency, before “going solar”.
A government estimate is that an average Australian home uses approximately 21 kW per day, the equivalent of seven tonnes of CO2, one of the greenhouse gases. In colder climates, this figure tends to be higher, due to greater water and room-hating loads.
‘Space heating and cooling and water heating account for nearly 63 per cent of household energy use.’
Here is a comprehensive government fact sheet on energy use in the home.
5. How long will it take to recoup my investment in a solar power system?
Many of our customers are “going solar” because they wish to reduce their electricity bills, and to assist in reducing their “grenhouse gas footprint”. Payback duration varies, according to where and how you live, and changing government incentives and rebates. SolarQuip is able to help you understand these benefits, during our site visit and quoting procedures.
For example, in Victoria, a net feed-in tariff means that it is difficult to accurately estimate how much the financial return on your system could be. You may choose to use little electricity during the day while the PV panels are producing most and therefore put most of your daytime energy into the grid at a tariff of around 25c per kilowatt. Alternatively, if you are at home during the day, you may decide to use as much energy during the solar production period. Thus you can avoid purchasing energy from your retailer, while you do the washing, run the dishwasher, iron clothes, run the pool pump and so on.
6. Solar power seems complicated. What will I need to do to look after this system?
In general, a solar photovoltaic system that is on the grid is very low maintenance. Most components are designed to operate without complex servicing for their operational lifetime, apart from regular panel cleaning, five-yearly checks of inverter safety, and other electrical checks from time to time.
In general, solar panels have a manufacturer’s warranty of at least 10 years, and in some cases will guarantee a certain minimum output for up to 20-25 years. Inverters vary, although are often under warranty for 5-10 years, and some manufacturers offer optional warranty extensions up to 25 years. You should understand that the inverter is a complex piece of equipment, and it may need to be replaced during the lifetime of your solar installation. For example, inverters may be destroyed if struck by lightning.
For peace of mind, SolarQuip offers a 24 month guarantee of workmanship for all of its work.
7. How will I know how much power my solar system is producing?
Various options exist for monitoring renewable energy production. A remote power monitoring unit operates wirelessly, allowing you to see from the comfort of your lounge, or from your computer or some smart phones. It is often quite satisfying to know at any time just how your system is performing and to view records of the systems performance over time.
