Some of the Basics of Solar Electric Systems
Finding a way to decipher the different types of solar power systems in todays myriad of online articles can be daunting and confusing to say the least. Much of the public think that you have to have batteries in order to have solar power, this is untrue, as a matter of fact most residential solar systems being installed today are “grid tied” or “grid connected”, without batteries. No batteries required!
Photovoltaic systems can be configured in a variety of ways. This post describes the 7 main types of configurations and a few examples of their uses.
1. Battery charging systems with integrated photovoltaics – This system charges the batteries of a complete component system. Like backpacks that have a cellphone, ipod, or laptop charger as well as the PV panels integrated within it. Or something as simple as a solar powered calculator.
2. Day use system – These systems incorporate solar panels wired directly into a DC (direct current) appliance with no storage device. When the sun shines on the panels you have power to the appliance. Some examples would be remote water pumping or to operate fans blowers or circulators for solar thermal.
These next 4 systems described require the use of an inverter to “invert” the DC (direct current) from the PV array or batteries to AC (alternating current) to power AC appliances and to connect to the grid if desired. These are the most common types of residential and small commercial/industrial/institutional systems that are in common use now.
4. DC System to power both AC and DC loads – This system has essentially the same components as the “DC system with storage batteries” listed above with the exception of the inverter for AC appliances. These systems are used in many off-grid applications because of the availability of common AC appliances and are usually significantly cheaper than the same unit powered by DC.
5. Hybrid Systems – Hybrid solar systems are a way to use other sources to charge the battery bank such as a wind generator, micro hydro, or gas/diesel generator. By having other sources to charge your battery bank you can be assured that during bad weather for a significant amount of time will not discharge your batteries beyond their desired capacity. Hybrid systems can be “grid connected” or “off-grid”.
6. Grid Connected without batteries – This is the simplest and most widely used system at this time. The components include a PV array, an inverter, and a two way meter from your utility. This system you are using the utility grid as your storage device. when the grid is off or down so is your electricity. All inverters made for grid tied systems must “sense” the electricity from the utility grid or they will not work. How a system like this works is the sun shines on the array during the day (usually low load use) and powers the appliances you use and the rest goes to the utility grid in the form of a credit to you, the power provider, at night (usually higher load use) you use those credits to power your home. Simple right!
7. Grid Connected with batteries – Solar systems like these are virtually identical to “DC Systems to power AC and DC loads” and/or “Hybrid Systems” listed above with the exception of being tied to the grid. When the grid is off or down your batteries then take over the job that the grid was doing. It is also refered to as “Grid tied with a battery back-up”. It is the second most common type of system in use today. Many commercial and institutional applications use this type of system where uninterrupted power is essential.
Some of these systems are flexible to meet the needs of the individual project. Keep in mind that all of these systems, especially where batteries are concerned, are complex and need important mathematical calculations in order to function properly and efficiently. They all also need proper installation to comply with national, state and local electrical codes (for example: disconnects, proper marking of all system components and voltages, etc.)
The national code is NEC (National Electrical Code) #690, this covers photovoltaics.
These are the 7 main types of Solar PV systems in use today. This will probably change as technology changes.
I hope this helps you out in your decision to go solar and what system will work best for your application and budget.
May the sun shine in your direction:
Peace and Prosperity
Rich @ NY Homesteader
Originally Written & Published by Richard Gately: © November 8th, 2009 all rights reserved.
Keep in mind that unless you have a U.L. (Underwriters Labs) certification on your homemade panels most, (but not all) major utility companies may be reluctant to give you an interconnect agreement for hooking up to the grid. You may have to use them in an Off-Grid application only.
Click the Image Below, and check it out for yourself.