Tuesday, September 6, 2011

Solar Generated Energy for Your Home: How Sunlight Hours and Sun Angle Effect Production (Part 6)

The angle at which the sun hits a solar cell effects the amount of solar energy produced. The following article explains these effects as well as some common residential solar systems characteristics such as tracking and mounting solutions. You may be surprised to find out that reflected light can actually produce solar energy even if you think it may not.

The Sun's Irradiance Throughout the Day

Many graphs and charts, found on the Internet via searching, show a solar cell module's output when it faces south throughout the 4 days following the fall equinox. These graphs most often show a bell curve of the power output, where peak production occurs around 12 to 1pm with a morning ramp-up and a decline as the sun goes down. This is due to intensity of light as well as deflection. As the days get shorter, the total irradiation falls as expected. The sun no longer is directly square with the panels, since it is lower in the sky.

Panel Tracking Devices for Home Solar Energy Systems

The best way to get around this decline in energy output is to place the solar array on a tracking device to keep it in direct sunlight for more time throughout the day. Looking at a sunflower can give you a good idea. The sunflower wakes up in the morning facing due East to catch the morning sun. As the day progresses, the sunflower turns its head to track as much sunlight as possible. It's perplexing why sunflowers grow so tall and sturdy? They soak up as much sun as possible.

There are two different types of tracking systems for residential solar energy units. Often there are alternate methods to mount a solar array. You could mount the solar panels on a fence, a flat wall, on a light pole, but the methods that follow are the most common.

1) Horizontal or flat mount array favors the summer months when the sun is highest.

2) Fixed angle at the optimum tilt angle yields the most kWh for a fixed array over the course of the entire year.

These two types of tracking systems create dramatically more exposure and higher sun hours all year long, but still more in the summer months. This relates to the overall need to calculate and take into account the total amount of energy required per month and per year then average out to the highest electric needs on a monthly basis. All of this data is included with the solar energy sizing estimates.

There are single axis tracking solar systems that track the sun from east to west. There are also dual axis tracking solar systems that track both from east to west and up and down, following the sun's altitude and azimuth to optimize production throughout the season. In the winter, the sun is much lower in the sky than in the summer therefore solar energy systems that can tilt up or down have a greater chance of catching all of the sun's energy.

Forms of Sun Irradiance

The sun reaches the solar panels in various paths, not just directly from a sun's beam being directly overhead. Because of this fact, there may be good generation of solar electricity on even overcast days or when you would not think the sunlight is of proper intensity.

There are three types of irradiance. 1. Diffuse Irradiation: Scattered light comes from the whole sky. Diffuse light from the sun does not exist on blue sky days where there are not clouds. On the other hand, it is found a lot in areas of smoggy or cloudy weather.

2. Direct Irradiation: A beam of sun light goes straight from the sun to the solar module and directly interacts with the solar cells

3. Reflected Light (i.e. the Albedo effect): This is light that is reflected or scattered by the ground or nearby surfaces like trees or other buildings. Snow gives off a lot of this albedo light and grass or dirt gives off very little.

Sun Path Diagrams and Home Solar Energy Systems

A sun path diagram plots the position of the sun throughout the year. This is very useful when designing and installing solar arrays, to optimize the performance by determining the best angle and to avoid shadows from trees, vents, other buildings, etc. Understanding where the sun traces across the sky at your home, allows you to place your solar energy unit in the correct location. You can also determine if you may need to supplement your solar power system with a tracking device.

Expanding Options for Residential Solar Energy

New solar energy technology is continually coming to market that takes the idea of solar power to a new and simpler levels. Homeowners, while it is very useful to know the nuts and bolts of solar power systems, do not have to know the level of detail as presented in this article. New solar technology and home solar panel rental services provide energy efficiency and better control of power consumption. These solar power rental programs enable electric services that are more responsive, more reliable, and more renewable.


At Solargies (Solar Energies), our objective is to spread the adoption of renewable solar energy as rapidly as possible. Daniel Stouffer is writer and promoter of green energy. Learn about Renting your own Solar Energy system at: =>

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