Could solar panels in space supply Earth with clean energy?
As a prototype prepares for tests in orbit, Nature looks at five of the biggest challenges for space-based solar power.
For 100 years, people have dreamed of sending vast arrays of solar panels into space and beaming their energy down to Earth. Unlike intermittent renewable-energy sources on the ground, these orbiting panels would always bask in bright sunlight and would potentially offer a continuous supply of power.
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How Beijing’s deadly floods could be avoided
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What is a ground-mounted solar panel?
Put simply, it is what it sounds like: solar panels mounted closer to the ground than a typical roof mounting. They’re generally mounted either to posts or racks that are anchored to the ground. You typically won’t find panels literally on the ground, but rather tilted at an angle to face the sun and at least a few feet above the surface to allow for air to flow around them and water underneath.
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There’s more to it than that, though that’s the gist. Ground-mounted solar panels have some advantages over rooftop panels, but come up short elsewhere.
Standard ground-mounted solar panels
Most standard ground-mounted solar arrays involve metal framing that is driven into or secured to the ground, typically with cement. There are any number of configurations that can be achieved using various racking and mounting systems.
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Standard mounting is a great option when access to the panels is a priority. This can be useful in locations that receive a lot of snow, or in situations where servicing, adjusting or replacing the panels is anticipated.
Ground mounting is also often selected simply because rooftop mounting isn’t an option for some reason. It’s possible but very unusual to install tracking systems on standard ground mounts due to the degrees of freedom required to rotate the panels to track the sun as it moves across the sky daily, and higher and lower during the course of a year. That said, racking systems can allow for some basic seasonal adjustments in tilt.
Pole-mounted solar panels
A primary reason for putting a rack of solar panels atop a single pole rather than a standard support structure is to allow for the use of a tracking system that can maximize the amount of power produced.
Typically a pole is driven into the ground permanently and a rack of tracking-equipped panels are affixed to the top. Trackers are usually a combination of sensors and motors that rotate the panels to follow the path of the sun across the sky. This means the panels can be pointing at the morning sunrise in the east and track that big ball of fire throughout the day until it sets below the opposite horizon. Ideally such systems will also tilt to accommodate the varying height of the sun between seasons.
You get 18 percent more [electricity] with a tracking system, said Wyldon Fishman, founder of the New York Solar Energy Society.
Pros of ground-mounted solar panels
The true advantage of ground-mounted panels is that they don’t have to go on your roof. If your house is in a nice, shady spot but you’ve got a sunny backyard, you can put them there.
Rooftop panels are also captive to your roof design, which may not be ideal since solar panels work best at a specific slope and direction. While the optimum tilt depends on your latitude, the best direction is basically toward the equator. Since most roofs weren’t designed with solar panels in mind, they likely aren’t perfectly positioned to maximize solar energy production. A ground-mounted system can be ideally positioned.
You also get better airflow than putting panels on a roof, which also can improve performance, especially when it’s hot out.
They’re kind of pretty in the yard, Fishman said. It’s also a shade spot, so you can put them up on a canopy and park your car under them and charge your car.
Fishman cites ease of access for service, replacement and snow removal as primary reasons for ground mounting. There’s also a few downsides to roof-mounting, which can require significant labor costs and increase the complexity of a future roof replacement.
Fishman notes that, in the rare case of a house fire where the fire needs to be vented, firefighters often need to cut a hole in the roof.
So there’s another reason to not have all that valuable glass and aluminum up on your roof.
Another advantage to leaving your roof out of the equation is eliminating the risk of damaging it. While solar installers offer warranties against roof leaks, they often don’t extend for the length of your solar panels’ life. While this is a manageable issue and solar panels typically require little maintenance, keeping panels off your roof eliminates the issue altogether.
If your panels do require maintenance, reaching them on the ground is easier than climbing up on the roof.
Disadvantages of ground-mounted solar panels
The biggest drawback of ground-mounted panels is cost. Instead of using a structure that’s already been built.- your roof.- installers will need to build a new one. This often involves more materials, upfront costs and trenching an underground line to connect the ground-mounted array to controllers and the rest of the system.
Ground-mounted solar panels might also be more susceptible to damage. While a lawn mower probably won’t throw a rock up onto the roof, ground-mounted panels might be in the line of fire depending how close to the ground they are. Being close to the ground brings your panels closer to animals or kids or other potentially destructive agents. There isn’t definitive data on maintenance costs for ground-mounted panels, though.
In many areas, zoning and setback rules may make it difficult to do a ground-mounted system, simply because many properties may not have the required space from property lines to allow for the construction of an array.
While rooftop panels don’t take up any space that’s regularly used otherwise, ground-mounted solar systems might consume coveted backyard space.
Ground-mounted solar system cost
Typically ground mounting is going to cost a bit more, but it really is a case-by-case evaluation process. Heaving big panels onto a roof, drilling holes in the roof and weatherizing those punctures can sometimes be a more ambitious undertaking than driving a pole in the ground and putting some panels on it. The energy analysts at Wood Mackenzie estimate that 8 kilowatts of rooftop solar costs 5000.99 per watt (or 23,920 in total).
If a ground-mount system means being able to install trackers, consider how quickly the roughly 18 percent boost in power production might allow you to make up for the extra cost and eventually save more than a rooftop system.
PowerRack System Design Notes
Product Specifications
- Length: 41
- Width: 26
- Height: 26
- Tilt Angle: 25°
- Warranty: 25 years
- Wind Load: 120 mph
- Snow load: 93 psf / 5400 Pa
- Max allowable solar panel width: 39.8
Ballast specifications
Any aggregate or solid material can be used as ballast, including sand, gravel, concrete, etc. The amount of ballast required is measured by the depth of the ballast in the center of the PowerRack unit.
- 4 deep at center of rack = 100 lbs. ballast
- 7 deep = 200 lbs.
- 10 deep = 300 lbs.
- 11 deep = 350 lbs.
- 13 deep = 400 lbs.
- 14 deep = 450 lbs.
- 15 deep = 500 lbs.
- 16 deep = 550 lbs.
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We’ll custom design this system for you and calculate how many solar panels you need to meet your goals.
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Is Ground Mounted Solar Cheaper?
Ground-mounted solar panels are safer to install, since there is no need to work on a rooftop, and their maintenance is also simpler. However, the total project cost is higher. Here are a few reasons why:
- You must build a structure to support the PV panels. A rooftop solar installation has a lower cost because the roof itself is the supporting structure.
- The support structure for ground-mounted solar panels also increases the labor requirements for your installation.
- Ground installations also have a more complex permitting process, since they involve foundations and a structural design and are treated as an independent construction.
Keep in mind that while they are more expensive, ground-mounted solar panels are much more productive, and with a solar tracking system can achieve even higher power output.
This means you can recoup your investment faster. If you want to start comparing the cost of a ground-mounted system or rooftop system for your home, you can click below to get a free quote from a top solar compan in your area.