Terminology Tuesday

Published on June 25th, 2013 | by growwny

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Solar Panels: Photovoltaic vs. Thermal

BY JOSHUA BERES, THE GROWWNY TEAM

Have you been noticing solar panels appearing on neighbor’s roofs or in a business’ backyard? You probably know they are there to provide electricity but did you know that there are two different kinds of solar panels? While most are aware of the “photovoltaic” (PV) solar panels, there are also “thermal” solar panels being put to use. Although they both derive their energy from the sun, there are several significant factors that vary greatly. We’re going to explain the differences in this blog.

Photovoltaic panels convert energy from sunlight directly into usable electricity. This electricity can used immediately to power various appliances and systems or just be transferred into the electrical grid supply and stored until needed. The conversion is accomplished via a reaction between the light photons from the sun and the silicon compounds within the solar panel. When the photons are absorbed by the solar panel, the silicon becomes energized by the reaction and releases electrons that are able to flow freely throughout the surface. Since the front of the solar panel is engineered to have a negative charge and the back has a positive charge, the electrons may flow freely between them when they are connected. Effectively creating what we know as electricity. Unfortunately, sunlight is obviously required for this process to occur; rendering the solar panels virtually useless at night or in certain weather conditions.  Ironically though, WNY is actually a very good area to implement solar panels as an energy source. Despite the long winter and snow, we actually get an above average amount of sunlight and solar energy can be efficiently harvested. With that being said, PV solar panels have many positive features; they are non-polluting, quiet, and fairly easy to maneuver and install

Photovoltaic Solar Panel

 

On the other hand, thermal solar panels capture the sun’s energy to generate heat. The solar panels are covered in a light absorbent material that captures energy from sunlight and heats up. In order to capture the heat from the solar panel, a fluid is flowing in close proximity to the heated panel so that the heat it is generating from the light is transferred to the fluid. Common fluids that are used include water, air, oil, helium, and nitrogen. From here, the fluid flows into a heat engine that is able to use the thermal energy from the fluid to turn a generator that produces electricity. However, if air or water is being used then it can provide hot water or increase the air temperature. Due to the fact that they require a fluid system and other mechanical components, they are harder to install, need maintenance, and are not as quiet as PV solar panels. Luckily, they make up for this problem with up to 40% energy efficiency compared to the 15% of PV solar panels. Not to mention that even though they aren’t effective in low sunlight conditions, heat energy is much easier to store than electrical.

 

Thermal Solar Panel

As you can see, both have their own unique positive and negative characteristics. When deciding which to choose, it is important to determine if you need a direct source of electricity (PV) or want to use it to heat your water and home (thermal). Considering the variety of weather conditions in WNY, a combination of the two might be the best option. Despite their promising future, there is still plenty of room to improve. Hopefully, they will continue to become more efficient so that they can meet the demands of modern society so we may become truly sustainable.

For information on installing solar panels, go to:  http://www.growwny.org/whats-new/1983-myth-monday-solar-panels-are-high-maintenance-and-too-expensive

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