How Solar-Electric Systems Work
Conceptually, solar-based electric systems are not that complex to understand. The technology has been around for decades, yet it has not gained widespread acceptance or application by the public.
Things are beginning to change, and we are approaching a tipping point with the convergence of high petroleum prices that will likely never return to the historic lows we were accustomed to, improvements in renewable energy components, and more public awareness about renewable energy.
There are three common options in solar-electric systems:
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grid-intertied (or grid-connected)
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grid-intertied with battery backup
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off-grid (or standalone)
Understanding the basic components of a solar system and how they function together is a first step in embracing the idea that renewable energy systems are viable alternatives or additions to on-grid systems.
Benefits of Solar Power
The greatest benefit of solar power is that the source of the power is free--the sun. And some of the other benefits are:
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Clean and green energy source, very environmentally friendly
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Quiet, almost silent operation
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Very reliable, with almost no maintenance costs
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Aids in reducing green house gases
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Long system life
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Nearly fixed cost of electricity for the life of the system
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Energy independence
A Standalone (Off-Grid) Solar Electric System
Off-grid solar systems are most common in remote locations, typically where providing grid power is cost prohibitive. Of course, a standalone system can work anywhere (and they do!). They've been retofitted into RVs and boats, and are used to provide emergency power during grid power failures. Place such a system on a platform that allows it to be towed by a vehicle and you have portable solar power - just like the systems North Star Energy Services manufactures.
The components required for a standalone system are:
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Photovoltaic (PV) panels
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Array mounting rack
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Array DC disconnect/breaker
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Charge controller
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Battery bank
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System meter
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Main DC disconnect
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Inverter
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AC breakers
Photovoltaic (PV) Panels
Photovoltaic (or solar) panels start the process. They convert sunlight into direct current (DC)electricity. A panel is composed of modules, which are in turn made up of individual solar cells. Each cell in a panel contains semiconductor material that uses light (or photons) to generate electricity. This is known as the Photovoltaic Effect, discovered by Edmond Becquerel in 1839. Basically, photons strike the panel displacing electrons in the semiconductors, causing voltage to be created and a current to flow, if a circuit is connected to the panel. The firstpositive/negative (p/n) junction solar cell was not created until 1954 at Bell Labs.
PV panels are rated according to the maximum number of watts they can produce under ideal conditions of sunlight and temperature. When multiple panels are connected together they are called an array. An array is connected together to produce a single electrical output. The bigger the array (i.e., the more panels), the more wattage produced.
The performance of a solar cell is measured in by its efficiency at turning sunlight into electricity. Only sunlight of significant strength will work efficiently to create electricity, and much of it is reflected or absorbed by the material that make up the cell. Because of this, a typical commercial solar cell has an efficiency of 13% to 15%—about one-sixth of the sunlight striking the cell generates electricity. Higher end cells have efficiencies of over 16%, but to get this extra efficiency, they are significantly more expensive.
These panels are very durable and rugged, and will last many years. Most PV panels, like the ones used by North Star Energy Services, are warrantied for up to 25 years.
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