Choosing PV structures: Trackers vs Fixed vs East-West (Case study inside!)
Choosing the right PV structure for your project leads directly to greater efficiency, power output, and ROI. In this post, we outline the three main PV plant structures and share RatedPower analysis of their performance.
19 Jul, 22
Adapting the structure of a solar photovoltaic (PV) installation to its geographic location and terrain is key to maximizing two important factors: the amount of energy it can produce and balancing costs with output. This becomes more important with utility-scale plants as it affects the amount of return on investment a project can generate.
The good ol’ times of unlimited available areas for greenfield PV projects are gone with the wind. Hilly terrains are common nowadays —and earthworks are more needed than ever. Learn how solar developers can face the challenge of topography using software in our webinar. Watch it now.
There are three main types of mounting structure for solar module design. In this post, we look at each one and how they work at two plants in Europe. Find the whole engineering documentation for each project at the end of the article.
PV plant structures explained
The mounting structures that support solar PV panels can be fixed in place or they can include a motor to change the orientation of the modules to track the sun. There are advantages and disadvantages to each design depending on the project.
Horizontal single axis trackers (HSAT) rotate on a single fixed axis with motor-powered tubes. The PV panels are mounted on the tubes, which rotate from east to west on a fixed axis throughout the day to track the movement of the sun across the sky and maximize solar generation.
Tracker structures create higher power generation as they keep panels at the optimal angle to receive the most sun rays during the day — meaning that for the same peak power an installation can generate more energy. They also have an overall lower levelized cost of electricity (LCOE), despite requiring higher capital expenditure, as the increased efficiency reduces the cost of the electricity produced.
While the greater number of PV modules you have placed in a tracker the more cost-effective your project will be, this creates long rows of trackers that are not suitable for sites with limited or irregular space. Single-axis trackers also have limitations in sites with undulating terrain or uneven sloping.
In some places, the geotechnical conditions at a site can make single-axis trackers unfeasible, as they require large foundations to accommodate wind loads.
For sites that require low pitch with a high power capacity, some of the benefits of trackers are lost by the backtracking algorithms.
Rather than using a tracker structure that adjusts the angle of PV panels to follow the sun during the day, a fixed-tilt structure angles panels towards the equator, so the angle depends on the latitude of the site. Panels are tilted towards the south in the northern hemisphere and towards the north in the southern hemisphere.
Fixed structures allow more peak power to be installed than trackers, providing more total energy for the same area despite the lower specific production (kWh/kWp) especially during the morning and evening.
Taking into account the shading between rows created by the tilt of the panels, fixed structures can reduce the pitch distance by installing more rows and increasing the amount of peak power and total energy generated. Fixed panel designs can be tailored to fit the highest quantity of panels at each site.
The duck curve — which shows the difference between solar generation at a given time of the day and electricity demand and resembles the shape of a duck when charted — is more pronounced with fixed structures.
The problem with the duck curve is that as more solar PV is installed and the power generated is injected into the grid it causes the market price of energy to fall sharply in the central hours of the day, cannibalizing its own profit. This is why trackers, by spreading their generation over the morning and evening, reduce their risk.
In east-west systems, solar panels are installed at 90-degree azimuth angles, with half of them facing towards the east and half facing towards the west.
Panels can be placed back-to-back to reduce the space between rows and allow for more modules to be installed to increase power generation. This is ideal for regions such as northern Europe, to maximize output from sites that have limited space.
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East-west structures also tend to be used more at higher latitudes as the sun does not rise as high in the sky and panels can be placed closer to structures without shading, generating more energy from the same area.
As east-west systems are installed lower to the ground, they reduce wind loads on the panels as winds pass over the array. And as they produce energy at a stable rate throughout the day, they reduce the chances of the inverter becoming overloaded by a midday spike.
East-facing and west-facing panels need to have separate electrical systems, requiring a different layout and site analysis from traditional configurations. And as there is less space between each panel, performing maintenance is more difficult than with a tracker system.
The large amount of modules installed that are operating outside its optimal angle causes the specific production of the PV (kWh/kWp) plant to drop and the total cost of the PV plant to increase, thus increasing the LCOE ($/kWh).
Comparing PV structures: a RatedPower case study
A comparison of sites designed and analyzed by RatedPower shows that the cost of the land in relation to the cost of the models, the cost of tracking equipment, and the actual energy output are all important factors when choosing a PV structure.
In Germany, for example, PV plant sites tend to be relatively small, so projects will use fixed or east-west structures that can install more power and deliver more energy versus tracker structures that occupy more space. East-west structures are also useful at higher latitudes, so projects at northern latitudes that need to generate a certain amount of electricity from a small site will tend to favor fixed or east-west structures. Projects that have more available space and focus on efficiency rather than specific power output would tend to use trackers.
The analysis shows that in Germany, tracker structures had a lower LCOE but generated 43% less energy — so while efficiency increased, the total output was lower. Specific price (€/kWp) was also higher for tracker structures than for fixed structures. East-west structures had higher costs and lower efficiency, as the panels do not face the south or the equator.
Get the 300 pages of technical documentation for each structure type. Download sample documentation.
We see similar results in Spanish projects regarding peak power, efficiency, energy production, and LCOE for the different structures — generating more energy at a lower price. But land costs are lower in Spain versus Germany, giving projects the freedom to use structures that take up more space.
Use pvDesign to plan your PV project structure
The structure of a utility-scale PV installation has a bearing on the energy efficiency, output, and revenue it generates. The most appropriate structure to get the highest returns will depend on the conditions of each project, with the cost of the site area and its latitude among the important considerations.
RatedPower’s pvDesign software can help you to automate the design of your project’s structure to find the best layout and maximize the return on investment.
What you should do now
Whenever you’re ready, here are 4 ways we can help you grow your solar business and reduce LCOE of your PV plants.
- Get hands-on with a free pvDesign demo. If you’d like to learn the ins and outs of how top photovoltaic software can help your engineering team, go ahead and request your free demo. One of our solar experts will understand your current design and engineering workflows, and then suggest practical tips on how to speed up them though the right tool.
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