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Solar Power Basics
Please feel free to contact us for expert technical assistance.

Producing electricity with solar power
Solar energy is commonly used to produce both heat and electricity.  Solar Thermal applications use solar energy to heat fluid or air, which is then converted to water or space heating (Solar thermal basics) .  In solar electric applications, sunlight charges a silicon-based photovoltaic, or PV panel, creating electric current flow. 

Components in a typical solar power system
The four primary components of a typical solar power electrical system which produces common 110/220 volt power for daily use are

Solar panels


Charge controller


Grid tie only would not need the battery or charge controller.

Solar panels charge the battery. The charge regulator insures proper charging of the battery. The battery provides DC voltage to the inverter, and the inverter converts the DC voltage to normal AC voltage.

Solar Power Panels
The output of a solar panel is usually stated in watts, which is determined by multiplying the rated voltage by the rated amperage. The formula for wattage is VOLTS times AMPS equals WATTS. For example, a 12 volt 60 watt solar panel measuring about 20 X 44 inches has a rated voltage of 17.1 and a rated 3.5 amperage.

V x A = W
17.1 volts times 3.5 amps equals 60 watts

Since sunlight intensity varies throughout the day, we use the term "peak sun hours" as to smooth out these variations into a daily average. Early morning and late-in-the-day sunlight produces less power than does the mid-day sun. Naturally, cloud cover also affects power production. Each geographical region has an Average Peak Sun Hours per Day rating which compensates for regional weather conditions and latitude.  See the section   "Determining your solar power requirements" for your region's ratings.

If an average of 6 hours of peak sun per day is available in an area, then a 60 watt panel produces an average 360 watt hours of power per day:

                                                                               60w times 6 hrs. = 360 watt-hours.

Solar panels are wired in series or parallel to increase voltage or amperage respectively.  They can be wired in both series and parallel to increase both volts and amps.

Series wiring refers to connecting the positive terminal of one panel to the negative terminal of another. The resulting voltage across the across the terminals of the combined panels is the sum of the voltage of  the two individual panels, but the current remains constant for both panels.  For example, two 12volt/3.5 amp panels wired in series produce 24 volts at 3.5 amps.  Four series wired panels produce 48 volts at 3.5 amps.

 Parallel wiring refers to connecting positive terminals to positive terminals and negative to negative. The resulting  voltage stays the same, but amperage becomes the sum of the number of panels.  Two 12 volt/3.5 amp panels wired in parallel  produce 12 volts at 7 amps. Four panels would produce 12 volts at 14 amps.

Series/parallel wiring refers to combining both of the above - increasing volts and amps to achieve the desired system voltage as in 24 or 48 volt systems and desired amperage. The following diagram reflects this. In addition, the four panels below can then be wired in parallel to another four and so on to make a larger array. Most grid tie panels are series wired to increase voltage which makes wire size smaller and decreases the amount of wire in such systems.

solar power panel wiring example

We recommend you also review our page Helpful Solar Power Glossary which will provide useful terms.

Solar Power Charge Controller
A charge controller monitors the battery's state-of-charge to ensure the battery receives charge-current when needed. It also ensures the battery isn't over-charged. Connecting a solar panel to a battery without a regulator seriously risks damaging the battery and potentially causing a safety concern.

Solar Power Battery
Deep cycle batteries used in solar power systems are designed to discharge and re-charge hundreds or thousands of times. These batteries are rated in Amp Hours (ah) - usually at 20 hours and 100 hours. Amp hours refers to the amount of current - in amps - supplied by the battery over the period of hours. A 350ah battery supplies 17.5 continuous amps over 20 hours or 35 continuous amps for 10 hours. The total watts  available in a 6 volt 360ah battery is found by multiplying 360ah times the nominal 6 volts,  2160 watts-hours or 2.16kWh (kilowatt-hours). Like solar panels, batteries are wired in series and/or parallel to increase voltage and amp hours.  

A battery in a solar power system needs sufficient amp hour capacity to supply needed power during the longest expected period "no sun" or extremely cloudy conditions. A lead-acid battery should be sized at least 20% larger than this amount. If there is a source of back-up power, such as a standby generator along with a battery charger, the battery bank does not have to be sized for worst case weather conditions.

The size of the battery bank depends on the storage capacity required, the maximum charge and discharge rates, and the minimum temperature at which the batteries will be used. When planning a power system, all of these factors are looked at, and the one requiring the largest capacity will dictate battery size.

Using an Inverter in a solar power system
An inverter changes DC power stored in a battery to standard 120/240 VAC electricity (also referred to as 110/220). Most solar power systems generate DC current which is stored in batteries or fed directly into the grid with a grid tie inverter. Nearly all lighting, appliances, motors, etc., are designed to use ac power, so it takes an inverter to make the switch from battery-stored DC to standard power (120 VAC, 60 Hz).

The inverter switches direct current (DC) back and forth to produce alternating current (AC).  The resulting AC current is transformed, filtered  etc. to produce an acceptable output waveform. The more processing, the cleaner and quieter the output, but the lower the efficiency of the conversion. The goal becomes to produce a waveform that is acceptable to all loads without sacrificing too much power into the conversion process.

Two basic inverter outputs designs are available  - sine wave and modified sine wave. Most ac devices can use the modified sine wave, but there are some notable exceptions. Laser printers which use triacs and/or silicon controlled rectifiers are damaged when provided mod-sine wave power. Motors and power supplies usually run warmer and less efficiently on mod-sine wave power. Items such as fans, amplifiers, and cheap fluorescent lights, give off an audible buzz on modified sine wave power. However, modified sine wave inverters make the conversion from DC to AC very efficiently, they are relatively inexpensive and can power many common electrical devices very effectively. 

Sine wave inverters can virtually operate anything. Your utility company provides sine wave power, so a sine wave inverter is equal to or even better than utility supplied power. A sine wave inverter can "clean up" utility or generator supplied power because of its internal processing. All grid tie inverters are true sine wave inverters

Inverters are made with various internal features and many permit external equipment interface. Common internal features are internal battery chargers which can rapidly charge batteries when an AC source such as a generator or utility power is connected to the inverter's INPUT terminals. Auto-transfer switching is also a common internal feature which enables switching between different AC sources, or from utility power to inverter power for designated loads. Battery temperature compensation, internal relays to control loads, automatic remote generator starting/stopping and many other programmable features are available.

Most inverters produce 120VAC, but can be equipped with a step-up transformer to produce 120/240VAC. Some inverters can be series or parallel "stacked-interfaced" to produce 120/240VAC or to increase the available amperage. There are new inverters on the market today that are capable of producing both 120/240 VAC and most grid tie inverters produce 240 VAC because it is more efficient.

Please feel free to contact us for expert technical assistance.

Solar Power


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