Safe Low Voltage - you don't have to be a licenced electrician to wire the equipment. [Note: If the system includes a DC to AC Inverter you must get a qualified electrician to connect the 240 Volt AC wiring).
Independent Supply of Power - Blackouts won't bother you anymore. A simple solar system to run DC 12V lights and small appliances such as a TV, fans and computer is easy to put together.
Transportable - a small system can be used on camping trips and holidays. When you get back home it becomes backup power.
Save the Planet - every watt you produce from your Solar System is one less that is needed from the electricity grid.
SOLAR SYSTEM COMPONENTS
The basic parts of your system are:
SOLAR MODULES - convert the sunlight to electricity. No moving parts and expected life of 40 years. They cost about A$8.00 per Watt or A$500.00 for a 60 Watt module.
BATTERY BANK - stores the energy produced by the SUN for later use. 12 Volt battery banks are popular for camping and mobile use. Larger banks of 24 Volt and 48 Volt Batteries are used in home power systems.
REGULATION & METERING - these control the charge going into the battery bank and prevent damage to the battery bank. Meters indicate the rate of Charge (AMPS) and the System Voltage (VOLTS).
FUSES are installed for SAFETY and to prevent system damage if faults occur.
PUTTING A SYSTEM TOGETHER If you are familiar with car battery type connections than you should have little difficulty connecting up a SOLAR SYSTEM. Just 2 wires connect each part in most cases. Red wires are used for Positive (+) connections and Black wires are used for Negative (-) connections. The 2 most important things to remember are wire size and fuses. To ensure your safety don't neglect this area. Wire needs to be much heavier than normal house wiring because low voltages mean that high current flow (AMPS) occurs. Although not as dangerous as AC household power care still needs to be taken.
See the link to Aurora for an intro to Basic Electricity and a simple Design Calculator.
ADDING AN INVERTER
In the last few years high quality DC to AC inverters have become available. An inverter converts the battery power to standard 240V AC house power. They come in all sizes from 75 Watt units to full house size 5000 Watt models.
Early inverters produced a rough approximation of 240 V which was fine for things like power tools but very hard on sensitive appliances. These were called SQUARE WAVE inverters.
A much improved type called the MODIFIED SQUARE WAVE inverter appeared on the scene and are still available particularly at the low price end of the market. Although more reliable and efficient they are still not recommended for use with all types of appliances. In particular any motor driven device such as washing machines can be prone to early failure when used on these types of inverters.
SINEWAVE inverters are now available from many suppliers and are the only type I recommend. This type is virtually identical grid power and will run virtually all 240V appliances as long as they are within the capacity of the inverter. You will pay more initially but you will be rewarded with BETTER PERFORMANCE and reliability.
REMEMBER: 240V AC power from an INVERTER, however small is just as LETHAL as grid or mains power. Be very careful with any AC voltage.
Finally when purchasing equipment think Quality before price. Cheap goods that perform well are rare and often break down when you need them most.. Well made products last longer and save you money in the long run.
Taking the time to sit down and work out your energy needs is the most important step in building a reliable Solar System. This will take only a short time and could save you a lot of money.
First of all we need to understand that a Solar Power System is a NO WASTE SYSTEM. This means that only energy efficient devices are allowed if you wish to minimise your cash outlay.
So when we consider lights for example, the ordinary light globe is out and the flourescent light is in. Refrigeration is another. Standard 240 Volt refrigerators use at least double the amount of energy compared to same size low voltage (12V or 24V) models. (See article on Where do all those WATTS go?)
A clever chap called Ohm came up with a few simple rules concerning the relationship between Volts, Amps, Resistance and Watts. The simple formulae are used in all our calculations and will guide you to working out how many Solar Modules and Batteries are required. See AURORA Web Site for Basic Tutorial on Electricity.
Rule 1: Volts = Amps X Resistance or V = A X R
Rule 2 Amps = Volts / Resistance or A = V / R
Rule 3 Watts = Volts X Amps or W = V X A
We tend to use rule 3 a lot. We also use TIME in hours to calculate how much power is used per day.
LIGHTING - no need for sitting in the Dark.
Using flourescent lights we can expect to light up 5 rooms at once with around 100 Watts of power. One 40W 1200mm Flouro and four 14W Compact Flourescent globes for example.
For convenience lets work with 12 Volts. Our lights use a total of 96 Watts if all are switched on. If we used all lights for 4 Hours per day we would require a system that can supply 4 hours X 96 Watts = 384 Watt/Hrs per day.
Solar Modules are sold by their size in Watts. A solar module will produce its maximum output at noon on a clear sunny day. Because the output is changing throughout the day we calculate the daily output by multiplying the Watts [80 for example] by an average number of hours relative to your location on the earth. Here in sunny Central Queensland I use 5 hours per day.
So 80W X 5Hrs = 400Watt/hours per day in sunny weather. Thus a 80 Watt Solar Module is capable of providing enough power for the lighting requirement we worked out. Now that wasn't to hard.
As the sun shines during the day and we want to use our lights at night we have to store the power. The most common storage is a LEAD ACID BATTERY. Now although a car battery can be used it is NOT recommended. Solar systems use a special DEEP CYCLE battery for long life and high capacity storage. Yes they cost more up front but they last a lot longer and won't let you down.
A battery can be likened to a bucket of water. Once emptied it must be refilled. Batteries have their capacity measured in AMP/HOURS [Ah]. Lets use a battery with 100 Ah capacity at the 100 Hour rate. A 12 Watt light connected to a 12 Volt battery would cause 1 Amp of current to flow. If used for 1Hour we would drain 1Ah from our battery. If we used it for 10 hours we would drain 10Ah.
In theory you could run the light for 100 hours before the battery is flat. In practice you should never completely flatten a lead acid battery as this will permanently damage it. A DEEP CYCLE battery can be safely discharged by 50%. So the practical useable capacity of our 100Ah battery is 50 Ah.
Now 2 lights @ 12Watt each will draw 2 Amps per hour. Run them for 10 hours (2A X 10Hrs] = 20Ah or 20% of the battery capacity is used.
RUNNING A CAR FRIDGE
A typical use for this same combination of 100Ah battery and 80 Watt Solar module is running a car fridge. If the fridge uses 4 Amps and runs for 12 hours per day the 4A X 12Hr = 48Ah per day. Our single 80W module will produce around 25Ah per day in practice. Thus we have a shortfall of 25Ah per day. In practice typical car fridges NEED two 80W modules for continuous operation.
A couple of Australian car fridge manufacturers have made models that will use only 25Ah per day. These fridges have THICK INSULATION and eutectic plates and are capable of running on only one 80W solar module. Therefore by purchasing the right product you save the additional cost of a $A600 solar module. Remember the golden rule. No Waste. By reducing waste in this case we saved $A600.
The simple maths used to calculate the above is used over and over for each LOAD. A colour TV uses 5 Amps and is watched for 5 Hours per day. 5A X 5Hrs = 25 Ah / day and so on.
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