25 June 2017
Solar Electric

Solar electric is often referred to as solar PV or solar Photovoltaic. Solar PV panels are only about 15% efficient, but convert the suns energy directly into convenient electricity.

Solar PV panels are extremely reliable, usually with 20 to 30 year manufacturer warranties. They are an excellent choice for mobile or back country power solutions because once they are correctly installed they are essentially maintenance free.

If you or your business is interested in Solar PV, please contact us and we will be glad to give you an estimate on an installation or the parts to do the project yourself. Check out some of our Solar PV installations in our gallery!

We also offer a wide selection of panels, inverters, and electrical components in our online store.

Solar PV on pole mount
How does a Grid-Tied Solar Electric system work? Minimize

A grid tied solar electric system is comprised of three main parts; the utility grid, the solar array, and the home/business AC power loads. Follow along in the diagram below as the parts are explained.

The solar array generates high voltage DC electric power. This power is put through an inverter that changes it to AC power. During operation the power goes to the home/business AC power loads and any extra is put back onto the grid. An AC disconnect is put between the inverter and the circuit breaker to allow the PV system to be easily disconnected by the utility company for maintenance.

Grid Tied Solar PV system layout

During the day, when the solar produces more power than the home/business uses, the power travels back to the grid. As it travels back to the grid it goes through your power meter and spins it backwards. At night or when the solar power does not meet the demand of the home/business, power is simply drawn from the grid turning your power meter forwards. The utility company will pay for any power that was put back onto the grid. The utility company will pay you with the same price rate that you pay them.

A common misconception with grid-tied solar is that when the utility power is ‘out’, the solar home or business will still have power. This is almost never the case, as additional expensive equipment would be necessary to prevent the power from traveling back out to power the neighborhood. When the utility power goes out, the inverter will shut down to prevent an overload.

How does an Off-Grid Solar Electric system work? Minimize
An Off-Grid Solar system has four main parts; the solar array, the battery bank, a backup generator, and the home/business AC power loads. Follow along in the diagram below as the parts are explained.

Unlike a grid tied solar system, an off grid solar array generates low voltage DC electric power. The electric power goes through a charge controller and to the battery bank. The charge controller regulates the voltage and protects the batteries from being over charged. Also between array and the battery bank is a DC disconnect. This device allows the array to be electrically disconnected from the battery bank during maintenance.

When the home/ranch's AC power loads start drawing power, the inverter converts the DC electricity from the battery bank into just the right amount of AC power to meet those demands.

Off Grid solar system layout

During the day the solar array charges the battery bank. The inverter draws from the battery bank when ever AC loads need to be powered. In the summer when the sun is high, the amount of energy from the solar panels can equal the amount of energy drawn by the inverter. In the winter however, when the sun is lower, the amount of energy from the solar array may not be enough to meet the AC demands. The solar energy is most often supplemented with a diesel or propane generator. The generator is tied into the AC side of the inverter, and can power loads as well as charge the battery bank.

It is possible to have a solar array big enough to never need a generator, but it is economically prohibitive. To meet large off-grid winter demands it is more economical to utilize wind, hydro or generators.

How does a charge controller work? Why do I need one? Minimize
A charge controller performs two important functions:
Charge Controller

1. Protect the batteries from over charging - The controller uses a logic circuit to prevent pushing the batteries higher than 15 volts. This prevents the power source(solar or other) from boiling off the electrolyte and ruining the batteries.

2. Boost low input voltages to maximize battery charging - This is done with complex electronics and DC-DC conversion. It is often advertised as "maximum power-point tracking". This technology can often increase the charging potential of a solar array by more than 30%. The method is certainly proprietary company for company, but basically the controller increases the voltage until the maximum available current is utilized.

For Example: The sun is just coming up and the solar array is putting out a potential of 11v. On a directly connected system no current would flow because the 11v is less than the 13v required to charge the batteries. If you were to short circuit the array through a multi-meter, the array may have a current of 8 amps. When the charge controller is added to the system it converts this 11v at 8amps into 13v at 6amps. This voltage potential is now greater than the battery potential and charging begins. Thus the benefit of a charge controller is that it takes the useless 11v power and converts into usable 13 volt power.

Check out charge controllers in our online store. Each one has a pdf specifications that can help you learn more about their use and operation.
Do Seasons Affect Solar Energy Production? Minimize
Solar energy production is the greatest in the early summer. The longest day and largest solar energy production day in the northern hemisphere is the summer solstice.
Seasons image courtesy noaa.gov

Due to the earths orbit about the sun; there are more sun hours in the summer than in the winter. For example Boise, Idaho receives 7 nominal sun hours in the summer and 3 nominal sun hours in the winter. Nominal sun hours are hours that a solar panel will produce its rated output on a clear day. These hours depend on the latitude at a given location.
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