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iSustain FAQ

Renewable Energy FAQ - Here are some answers to all those questions regarding solar,wind and all other related renewable energy FAQ.
If you're considering putting a system together for your home or business, see our Kits and Systems page for more information and prices.


How much does a Grid Connect Solar energy system cost?
The total cost for purchasing and installing a solar system is based on the size of system you require, the rebates available in your area, and the specific details of the layout of your home.
Small solar power system costs start at around $ 6,000 after rebates and a system to provide most of the electricity for an average home can cost more than $30,000 for on-grid.
Some facts to get together before calling for a quote:

Your average household usage in kWh/day (The average household uses 25 kWh/day)
Accessibility of your roof and the direction it faces
Space available on roof, shade on roof

The aproximate distance from where your solar panels will go to where your switchboard or sub-board is.
A base installation rate includes the grid connect system being installed on a pitched metal roof facing north with appropriate surface area available. Additional costs will be incurred for a flat or tiled roof; any equipment upgrades and extended warranties.
What size system will I need to run my home?
That entirely depends on your energy usage and your geographical location. A 1 kW system will cover between 16 and 25% of the energy consumption of a medium household. A 4 kW system will cover aprox 100% of the energy consumption of a medium energy use household.
Does roof orientation really matter?
Most certainly. For example, a system with solar panels facing in a westerly direction will generate far less than one with a northerly aspect.
How does a Grid Connect Solar system generate electricity?
When sunlight shines onto your Solar modules, our advanced photovoltaic (PV) technology converts the light into direct current (DC) electricity. Your system’s inverter then converts the DC electricity into 240V alternating current (AC) electricity for normal use in your home.
How is the solar electricity metered?
In Australia there are two different ways of metering the electricity your Solar system produces.

One method used is called ‘net metering’. Electricity utilities allow the excess electricity generated (generation exceeding consumption) by your solar system to be sent to the grid at the retail rate for that given time period by allowing the utility meter to effectively spin backwards. This arrangement allows all electricity produced by your system to be used to offset the remaining portion of your utility bill. In other words, the utility buys back the excess electricity your Solar system exports to the grid at the same retail price you pay for that electricity. However, for most large homes or homes with high electricity demand, a solar electricity system will cover only a portion of the total demand, thereby simply reducing the amount you take from the grid.

The second method used is ‘export metering’ or ‘gross metering’. This is where utilities allow all the electricity generated by your solar system to be sent to the grid at the retail rate for that given time period. This is done via a dedicated utility meter which is separate from your utility consumption meter. This arrangement allows all electricity produced by your solar system to be offset against your entire utility bill. In other words, the utility buys back all the electricity your Solar system produces, at the same retail price you pay for that electricity.
What will happen in utility electrical blackouts?
By law, any grid-connected solar electricity system must shut down until utility power returns in order to assure a safe working environment for utility line workers. The system will automatically come back online when the blackout is over.
With grid connect systems, what can I do to keep power during a blackout?
You will need battery back-up.
How much of a reduction in carbon dioxide emissions will I achieve?
Using a comparison to a car, the average vehicle in Australia travels 20 000 km per annum, which is equivalent to 3.3 tons of carbon dioxide discharge annually. A 2kw grid connected system will prevent 3.3 tons of carbon dioxide being generated through coal fired power generation - so it's the equivalent of taking a car off the road each year.
How safe is a Grid Connect Solar system?
Solar electricity systems are very safe. They have no moving parts and require very little maintenance. Solar components carry all appropriate/recommended electrical certifications. As with any electrical appliance, you should always use proper care when handling solar system components.
iSustain Australia highly recommends that installation and maintenance of solar systems be handled by BCSE-accredited solar installers and that licensed electricians be used for grid-connected systems.

Remote Area Power Systems FAQ

How much does a RAPS cost?
A RAPS system to provide all of the power requirements for an energy-efficient house with a typical range of appliances can cost between $15,000 and $50,000. The size of the system needed will depend on the number of people in the home, what appliances are in use, and how often they are used. Rebates are available to pay for up to half of the system costs.
Connecting to a grid may cost $10,000 per kilometre of power lines, making the option of a RAPS system a viable alternative.
The cost of a small renewable energy system to run a farm shed light using one panel and a small battery can be as low as $200.
How does a remote power system work?
The DC electricity produced by the wind turbine or solar panel array is routed through wiring to a solar regulator or charge controller, which regulates the charging of the deep cycle battery bank. DC appliances can then be run off the battery or via a power inverter to supply standard household appliances with 240 volt electricity.
How many solar panels will I need?
This will vary greatly, but as a very general guide, 75 to 120 watts of solar panels are required for every 200 AH of batteries.
How many batteries do I need?
Depends greatly on your energy requirements. For example, if you just wish to run a notebook all day, LED lighting and a few small appliances intermittently, a 100 AH battery may suffice, assuming you have the correct sized solar panel to charge it. To run a household will require far more battery storage.

Solar Panels FAQ

What is a solar panel?
A solar panel converts light energy into electricity without causing pollution. Solar panels are also referred to as a photovoltaic or PV modules (photo = light, voltaic = electricity).
How does electricity get stored for use after sun goes down?
With Remote Access Power Systems (not on mains power) the energy is stored in deep cycle batteries for use as required.
Grid connect systems direct excess electricity produced during the day back into the local electricity grid. This turns your electricity meter backwards in the process. You then receive credit for any power that you put back into the grid. At night time, you automatically use electricity straight from the grid.
Can solar panels work in the shade?
The output of any panel will be reduced or cut off if shaded. However, some solar panels do work better than others in the shade. If a single cell is heavily shaded, that cell is cut off.

Deep Cycle Battery FAQ

What is a deep cycle battery?
Deep cycle batteries used in solar power systems are batteries designed to be discharged over a long period of time (e.g. 100 hours) and recharged hundreds or thousands of times, unlike conventional car batteries which are designed to provide a large amount of current for a short amount of time.

Power Inverters FAQ

What is an inverter?
Most household appliances use alternating current (AC) electricity, which is what comes out of the power point of a mains-grid connected house. However, the batteries used in RAPS supply (DC) electricity. To make conventional appliances run in a RAPS house, this DC electricity must be converted to AC.
This conversion is done by a device called an inverter. The inverter is connected to the battery bank, and provides mains-type AC electricity to the house. The inverter needs to be sized to suit the house's electrical requirements, a common size being around 2000 watts, or 2 kilowatts.
Do power inverters store power?
Power Inverters cannot store power, they just act as a 'converter' to change the power from a 12VDC power source to 240V AC. This enables you to use normal household appliances and tools from your vehicle.
What are the different types of inverters?
There are two different types of power inverters: modified sine wave and true sine wave inverters.
The difference between the two types is how close the output power replicates standard AC mains power.
The difference in output between mains power, modified sine wave and true sine wave inverters is shown below:

Modified sine wave inverters
A modified sine wave inverter can adequately power some household appliances and power tools. It is cheaper, but may present certain compromises with some loads such as computers, microwave ovens, laser printers, clocks and cordless tool chargers. Virtually all low cost inverters are "modified sine wave". A modified sine wave is easier and cheaper to produce than a sine wave inverter. True sine wave inverters
A true sine wave inverter is designed to replicate and even improve the quality of electricity supplied by utility companies. To operate higher-end electronic equipment, a sine wave inverter is recommended. Efficiency has reached up to about 98% and the electricity from these devices is of a higher quality than grid power almost anywhere in the world.
What is a suitable power source to operate an inverter?
To operate an inverter and supply power to an appliance, a suitable 12V DC power supply is required. This can be a vehicle, boat or caravan battery, portable power pack or an independent 12V lead acid battery. For most applications, a deep cycle battery is recommended for best performance. For 24V power inverters a 24V DC power source is required and are designed for those that use a 24 Volt System or battery.

Solar Controller and Regulator FAQ

What is a solar regulator?
A regulator is an electronic device which controls the voltage of the charging source. Regulators are used to stop the batteries from being overcharged. When the batteries are fully charged, the regulator halts the flow of power from the solar panels to the batteries. Additionally, a regulator stops any power flow from the batteries at night. The controller is also used so that the batteries get charged at the correct voltage. In order to calculate the Amp rating of a controller you must follow this simple equation:

Amps x Volts = Watts.

So, if you have a 175W panel at 24 volts the following calculation should be made Amps x 175 = 24, then the regulator should be at 175/ 24= 7.3 Amps.
What size regulator should I allow for?
The solar regulator's measured amp rating should slightly exceed the total amp rating of the solar panels.

Battery Charger FAQ

What size battery charger do I need?
You should buy a charger which is 1/10 of the battery size. ie. If you have a 100amp deep cycle battery, buy an automatic 10amp battery charger.
Different types of batteries require different charging regimes. SLA (sealed lead acid), AGM (absorbent glass matt) and gel batteries are traditionally charged at a lower voltage than flooded lead acid batteries. This varies depending on the manufacturer and you should always check what charging voltage is required before you buy deep cycle batteries and a battery charger.

Wind Power FAQ

How is wind power generated?
The terms "wind energy" or "wind power" describe the process by which the wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy in the wind into mechanical power. This mechanical power can be used for specific tasks (such as grinding grain or pumping water) or a generator can convert this mechanical power into electricity to power homes, businesses, schools, and the like.
Wind turbines, like aircraft propeller blades, turn in the moving air and power an electric generator that supplies an electric current. Simply stated, a wind turbine is the opposite of a fan. Instead of using electricity to make wind, like a fan, wind turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity.
Why is wind power more difficult to calculate?
The vagaries of the wind in different areas, differing loads, land mass heights and potential structures that will cause wind turbulence are major considerations. The closer you are to the sea the greater likelihood of stronger winds. This has its own challenges with wind strengths that can destroy the generator. Turbulence must be considered.
How can I get a reasonable calculation on wind turbulence?
One of the best non technical methods is with a kite. You have streamers tied to the kite string and by taking careful note of how the streamers react you can easily judge how far you need to have the generator placed from the cause of the turbulence.
What maintenance is required on wind generators?

No easy answer. In some cases it is the tower with guy wires not able to support the structure adequately. In turbulent areas bearings. Most modern wind generators do not have brushes, replacement of leading edge protective tape in sandy areas is common.

When should I have a combination of wind power and other sources?

Unless you have an exceptional site for wind power it is common to have a hybrid site with a combination of say wind, solar and diesel power.


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