Elements of Solar PV

It may come as a pleasant surprise that solar electric systems are very simple to operate. The tricky part is designing the correct system for a homeowner?s energy needs and location. Solar electric systems are made up of four main categories of equipment: energy sources, energy conversion, energy storage and everything else.

Solar panels are a fantastic energy source. Solar panels are also known as solar electric (photovoltaic, or PV) panels. A group of solar panels is known as a PV or solar array.

Solar electricity is not the only renewable energy source available for homeowners. Wind and falling water can be used, but few locations have the resources available. Due to the lack of resources, an investment in these may not be worthwhile. However, solar power is abundant in most areas and has proven to be a smart investment that will save the homeowner money and help the environment.

Energy Storage

Electrical energy can be difficult to store. Since PV technology doesn?t work at night, some kind of storage is essential. There are two options for storing energy: a large bank of batteries, or the utility power grid from which most Americans purchase their electrical energy.

The grid is usually the optimal choice for homeowners. Batteries eventually war out and will need to be replaced. If you need energy, the grid pumps it to you and you?ll be responsible to pay for it at the end of the month. If your solar PV system is creating more energy than you are using, you can sell the extra energy back to the grid. However, the amount you?ll be paid can greatly vary. Off-grid systems have no connection to the grid at all, and rely solely on batteries for energy storage.

 

The main issue with using the grid to store energy is that when it goes down (during a blackout), you?ll be in the dark. It doesn?t matter if your PV system is bathed in sun during a blackout, you will only have power for your home if the grid is working. In areas where blackouts are common, PV systems may include batteries as a backup. These are known as ?islanding? PV systems.

Energy Conversion

If you purchase electricity from the grid, it comes in the form of alternating current (AC), often referred to as ?house current.? All PV systems produce electricity in the direct current (DC) form. Therefore, PV power must first be converted into something usable. Inverters and controllers are the two devices that do this.

Inverters
These smart boxes convert DC power from a solar array or a battery bank into AC house current that you can use yourself, or sell back to the utility. An inverter will control all the buying and selling for you. If you have no batteries, the inverter also works as a PV controller. Also, there are ?micro-inverters? available that attach behind each solar module to streamline installation and allow detailed monitoring of each module of the array. An inverter is usually installed near the array to reduce wiring costs, primarily outdoors or in a garage.

Controllers
If a system is off-grid or has a backup battery bank, all PV energy will be used to directly charge the battery. Once the battery is full, the inverter takes control of selling any excess energy to the utility. Since batteries are quite fragile, a controller is necessary to keep the battery from over- or under-charging damage.

Everything else
Racking: Photovoltaic modules are exposed to extreme weather conditions so sturdy mounts are essential. These are called ?racking,? and racks are available for all types of roofs, for vertical poles, and for your yard. Commercial racking systems make the installation of PV modules simple providing sliding module clips and minimal hardware difficulties.

Disconnects: Disconnects are required for all the load circuits in your home and in certain parts of a PV system by the National Electrical Code. They are imperative for both safety and convenience. Convenience is important when electrical work or upgrades are needed so the entire system doesn?t need to be shut down.

Monitoring: Solar electricity is an investment so you?ll want to know if your investment is paying off, and how quickly it is. If the system involves battery storage for backup or off-grid use, metering is necessary for extending battery life. The meters used for monitoring range from rudimentary designs that keep track of energy used vs. energy gained to elaborate wall-mounted color displays that are wireless and Internet-enabled. These fancy systems allow you to monitor your system remotely and often include impressive charts and graphs to detail performance. If you prefer, some companies can monitor your system for you. If you choose this route, you?ll simply log onto a website when you would like to check the status.

(c) FreeCleanSolar, Inc.

Source: http://blog.freecleansolar.com/2011/06/10/elements-of-solar-pv.aspx?ref=rss

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