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Rising Use of Solar Trackers in Grid-Scale PV

Posted January 18, 2017 12:00 AM by Engineering360 eNewsletter

According to a recent report from GTM Research, 12.6 GW of PV trackers will be installed globally this year, up from 5 GW in 2015. As the use of grid-scale photovoltaic (PV) systems continues to grow, a new solar tracking technology can improve production at PV farms by anywhere from 15-30% when compared to a fixed-tilt system.


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#1

Re: Rising Use of Solar Trackers in Grid-Scale PV

01/19/2017 4:04 AM

It is not clear exactly what is meant by a "fixed tilt system!"

Do they mean fixed in the elevation, as I suspect, but otherwise tracking the sun, or possibly also fixed in direction?

Or that both are fixed, as I see in all the big solar "farms" here in Germany, for example? No movement whatsoever.

I have long been of the opinion that investing in more solar cells, but fixed in both elevation and direction, is probably the best way to go, as moving things around properly, costs money as well as possibly extra maintenance costs. Which could be better invested in more cells!

Even if the direction is changed to "follow" the sun, and the elevation is adjusted by hand, to the best one of say three or four possibilities in the year, that simplifies the system quite a bit.

Furthermore, it is not necessary to "track" the Sun through sensors of any sort (as many apparently do!), as the sun is always at the same horizontal angle to any point on the earth, at the same time (local) on any day of the year. Many forget or simply do not understand that!!

The only variation is its height above (or below!) the horizon through the year.....(that is whether you can actually see it or not!)

Any system that tracks the sun in some optical method, has to be designed to still work in spite of thick cloud, fog, mist and time of day! Or even cars, people and animals, accidentally parked where the sun is shining from!! Which makes it more complicated than needed.

Many years ago, a friend of mine made such a tracking system, that simply went "wild" looking for the sun, if the rays were blocked in the daytime.......it was quite funny to watch!!

A 24 hour clock, synchronised to the midday sun's highest point at local 12 midday, will give the angle of the sun accurately for any point on the earth, once the simple conversion of the time to 360° has been made....even though, for part of that time, the sun will not be visible, due to it being "set" (or clouds or other "things"!).

Such a system does not need sensors to "watch" the sun that may need regular cleaning, it also simply ignores fog, mist and clouds, and stillpoints to the sun's actual position.

Obviously, once sunset has happened, then the system can shut down, till sunrise.

A simple system could position itself to the direction that sun rises on say mid summers day, each and every day of the year, and track from there, even when it's still dark at other times of the year.

Where a more intelligent system, could be programmed to know the time and angle for each and every day of the year, exactly where the sun will appear on the horizon (and disappear as well in the evening!).

I hope that I have explained myself well enough, if not, please ask!!

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Re: Rising Use of Solar Trackers in Grid-Scale PV

01/19/2017 9:25 AM

There are advantages and disadvantages to tracking systems, depending on economic factors and climate:

Advantages:

  • Trackers generate more electricity than their stationary counterparts due to increased direct exposure to solar rays. This increase can be as much as 10 to 25% depending on the geographic location of the tracking system.
  • There are many different kinds of solar trackers, such as single-axis and dual-axis trackers, all of which can be the perfect fit for a unique jobsite. Installation size, local weather, degree of latitude and electrical requirements are all important considerations that can influence the type of solar tracker best suited for a specific solar installation.
  • Solar trackers generate more electricity in roughly the same amount of space needed for fixed tilt systems, making them ideal for optimizing land usage.
  • In certain states some utilities offer Time of Use (TOU) rate plans for solar power, which means the utility will purchase the power generated during the peak time of the day at a higher rate. In this case, it is beneficial to generate a greater amount of electricity during these peak times of day. Using a tracking system helps maximize the energy gains during these peak time periods.
  • Advancements in technology and reliability in electronics and mechanics have drastically reduced long-term maintenance concerns for tracking systems.

Disadvantages:

  • Solar trackers are slightly more expensive than their stationary counterparts, due to the more complex technology and moving parts necessary for their operation. This is usually around a $0.08 – $0.10/W increase depending on the size and location of the project.
  • Even with the advancements in reliability there is generally more maintenance required than a traditional fixed rack, though the quality of the solar tracker can play a role in how much and how often this maintenance is needed.
  • Trackers are a more complex system than fixed racking. This means that typically more site preparation is needed, including additional trenching for wiring and some additional grading.
  • Single-axis tracker projects also require an additional focus on company stability and bankability. When it comes to getting projects financed, these systems are more complex and thus are seen as a higher risk from a financier’s viewpoint.
  • Solar trackers are generally designed for climates with little to no snow making them a more viable solution in warmer climates. Fixed racking accommodates harsher environmental conditions more easily than tracking systems.
  • Fixed racking systems offer more field adjustability than single-axis tracking systems. Fixed systems can generally accommodate up to 20% slopes in the E/W direction while tracking systems typically offer less of a slope accommodation usually around 10% in the N/S direction.

http://www.solarpowerworldonline.com/2016/05/advantages-disadvantages-solar-tracker-system/

There are two factors that affect the efficiency. The cosine law implies that the amount of energy captured by the panel is proportional to the cosine of the tracking error. But the increased slant range through the atmosphere (Beer's law) lessens the advantage of tracking at low elevations.

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