Ground Mounted Solar PV Systems

There are several ways to mount solar photovoltaic (PV) systems on the ground. As with most choices, their are advantages and disadvantages to each.

Fixed Ground Mounted Solar PV

Fixed Solar PV Array

Fixed systems do not move, thus the name "FIXED". This systems tend to be the least cost choice and easiest to install. If you are handy, a fixed system can often be self-installed.

On the down side, Fixed solar PV systems tend to produce the least amount of power, of any of the ground mounted solar alternatives. Generally they can be pointed directly at true south, which provides an advantage over most rooftop systems.

Variations

One Panel High - mounted on a simple frame, to hold just one row of panels, this variation usually uses ballasted weight to hold the structure in place. With ballasted weights, a 10kW system can be installed in a few hours. As you are not attaching the frame to footings, it's the fastest, easiest and cheapest way to mount solar panels. It has these same advantages when it's time to move or remove the solar panels after their useful lifetime. On the down side, this mounting system also takes up the most space.

Fixed ground mounted solar

2 or 3 Panels High - another very common arrangement is to place the solar PV panels on frames 2 or 3 rows high. As you add more height, the framing structure increases in strength and weight. These systems usually attach to cemented footings or large screw footings. Again, as the mounting increases in height, so increases the force of the wind on the structure. Fixed solar mountings of 2 or 3 rows height, are still relatively cheap to install and reduce your footprint over a single panel framework.

Adjustable Ground Mounted Solar PV

Adjustable solar PV systems are very similar to a Fixed system, but have the ability to adjust the surface of the solar array, such that it faces the height of the sun in the sky. In the summer months, the sun will be much higher in the sky. Conversely, in the winter, the sun passes through an arc that is at it's lowest point in the sky. By adjusting the solar array either 2, 3 or 4 times per year, you can increase the power output by up to 10% over a fixed solar mount. Adjustable solar PV systems also tend to have little maintenance as there aren't any constantly moving parts.

This website shows the number of kWhs of electrical production, per kW of installed solar panels, by month, for various Fixed angles:

Natural Resources Canada PV Potential

Here's a sample output for London, Ontario:

PV potential (kWh/kW)

South-facing vertical (tilt=90°) South-facing, tilt=latitude South-facing, tilt=latitude+15° South-facing, tilt=latitude-15°
January 62 61 65 55
February 74 80 82 74
March 82 104 102 101
April 70 114 105 118
May 63 123 108 132
June 57 123 105 136
July 60 127 109 139
August 66 119 107 126
September 71 104 98 104
October 76 92 92 86
November 52 56 58 51
December 50 50 53 45
Annual 782 1152 1084 1166

Variations

Adjustable Racks - very similar to a FIXED mount, these racks allow you to easily adjust the angle of the solar array, to aim it at the sun. This system does not TRACK the sun, it's adjusted 2-4 times per year, to the proper height of the sun in the sky.

Adjustable Solar Mounts

Pole Mounted Adjustable Solar Systems - another very common arrangement is to mount the solar array on a metal pole. These setups are usually in array configurations of up to 12-15 panels. Again, a very simple adjustment is made to point the array at the sun, 2-4 times per year. With only a few minutes of effort, your output can be increased by 10%. Pole mounted systems tend to cost more than a rack mounted system. However, poles keep the solar array up out of the snow and away from most animals.

Solar PV Trackers

Solar Trackers move the array of solar panels across the sky, instep with the position of the sun. Tracking the sun has a very significant improvement upon production output. Of course, trackers require regular maintenance as they move every day.

Pole Mounted Solar Systems - Spacing

Here's a Microsoft Excel spreadsheet from Wattsun that allows you to see the shading throughout the year, based on how you space your pole mounted solar system. Solar Tracker Spacing

solar tracker spacing

 

VariationsSingle-axis solar tracker

Single-axis Tracker - mounted on a pole or on a rotating frame, the single-axis solar tracker moves the solar array across the sky, from sun-up to sun-down. This tracking of the sun, will increase production by 25-30%. Some single-axis trackers can also be adjusted a couple of times per year, to further increase production. Adjustable, single-axis trackers can increase production up to 35% over a Fixed solar PV system

 

Dual-axis Trackers - usually mounted on a pole, the dual access tracker moves both east to west and on a vertical axis. With a dual axis tracker, output levels of 30-40% over a fixed system are possible.

Dual-axis solar tracker

Active or Passive Tracking - An active tracker measures the strength of the sunlight and moves the array to the brightest spot in the sky. On a cloudy day for example, an active tracker may lay the array down horizontally, so the panels point straight up at the sky. A passive tracker is programmed to know where the sun is located and tracks that path in the sky. A very good active, dual-axis tracker, may be able to produce up to 45% more than a Fixed array.

 

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