astronomy

Solar tracker

Solar tracker is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Solar tracker rather than just read about it. In short: A solar tracker is a device that orients a payload toward the Sun. Payloads are usually solar panels, parabolic troughs, Fresnel reflectors, lenses, or the mirrors of a heliostat.

Key takeaways

Solar tracker belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Solar tracker to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Solar tracker from memory before moving on to harder problems.

Reference excerpt

A solar tracker is a device that orients a payload toward the Sun. Payloads are usually solar panels, parabolic troughs, Fresnel reflectors, lenses, or the mirrors of a heliostat. For flat-panel photovoltaic systems, trackers are used to minimize the angle of incidence between the incoming sunlight and a photovoltaic panel, sometimes known as the cosine error. Reducing this angle increases the amount of energy produced from a fixed amount of installed power-generating capacity. As the pricing, reliability, and performance of single-axis trackers have improved, the systems have been installed in an increasing percentage of utility-scale projects. The global solar tracker market was 14 gigawatts in 2017 73 GW in 2022, and 94 GW in 2023. By 2024 the solar tracker market was 111 GW and 99% of new utility-scale solar projects used single-axis tracking due to lower LCoE. By contrast, fixed-tilt was primarily used in places with difficult terrain, brownfields, or high winds. In concentrator photovoltaics (CPV) and concentrated solar power (CSP) applications, trackers are used to enable the optical components in the CPV and CSP systems. The optics in concentrated solar applications accept the direct component of sunlight light and therefore must be oriented appropriately to collect energy. Tracking systems are found in all concentrator applications because such systems collect the sun's energy with maximum efficiency when the optical axis is aligned with incident solar radiation.

Basic concept

Sunlight has two components: the "direct beam" that carries about 90% of the solar energy and the "diffuse sunlight" that carries the remainder – the diffuse portion is the blue sky on a clear day, and is a larger proportion of the total on cloudy days. As the majority of the energy is in the direct beam, maximizing collection requires the Sun to be visible to the panels for as long as possible. However, on cloudier days the ratio of direct vs. diffuse light can be as low as 60:40 or even lower. The energy contributed by the direct beam drops off with the cosine of the angle between the incoming light and the panel. In addition, the reflectance (averaged across all polarizations) is approximately constant for angles of incidence up to around 50°, beyond which reflectance increases rapidly.

Notes

For example, trackers that have accuracies of ± 5° can capture more than 99.6% of the energy delivered by the direct beam plus 100% of the diffuse light. As a result, high-accuracy tracking is not typically used in non-concentrating PV applications. The purpose of a tracking mechanism is to follow the Sun as it moves across the sky. In the following sections, in which each of the main factors are described in a little more detail, the complex path of the Sun is simplified by considering its daily east-west motion separately from its yearly north-south variation with the seasons of the year.

Solar energy intercepted The amount of solar energy available for collection from the direct beam is the amount of light intercepted by the panel. This is given by the area of the panel multiplied by the cosine of the angle of incidence of the direct beam (see illustration above). Put another way, the energy intercepted is equivalent to the area of the shadow cast by the panel onto a surface perpendicular to the direct beam. This cosine relationship is very closely related to the observation formalized in 1760 by Lambert's cosine law. This describes that the observed brightness of an object is proportional to the cosine of the angle of incidence of the light illuminating it.

Reflective losses

Not all of the intercepted light is transmitted into the panel; some is reflected at its surface. The amount reflected depends on both the refractive index of the surface material and the angle of incidence of the incoming light. The amount reflected also differs depending on the polarization of the incoming light. Incoming sunlight is a mixture of all polarizations, with equal amounts in direct sunlight. Averaged over all polarizations, the reflective losses are approximately constant at angles of incidence up to around 50°, beyond which they increase rapidly. See for example the accompanying graph, appropriate for glass. Solar panels are often coated with an anti-reflective coating, which is one or more thin layers of substances with refractive indices intermediate between those of silicon and air. This causes destructive interference in the reflected light, diminishing the reflected amount. Photovoltaic manufacturers have been working to decrease reflectance with improved anti-reflective coatings and with textured glass.

Daily east-west motion of the Sun The Sun travels through 360° east to west per day, but from the perspective of any fixed location, the visible portion is 180° during an average half-day period (more in summer, slightly less in spring and fall, and significantly less in winter). Local horizon effects reduce this somewhat, making the effective motion about 150°. A solar panel in a fixed orientation between the dawn and sunset extremes will see a motion of 75° to either side, and thus, according to the table above, will lose over 75% of the energy in the morning and evening. Rotating the panels to the east and west can help recapture those losses. A tracker that only attempts to compensate for the east-west movement of the Sun is known as a single-axis tracker.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Solar tracker

Start with the simplest possible case. Write down what Solar tracker claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Solar tracker before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Solar tracker ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Solar tracker

In research: Solar tracker appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Solar tracker in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Solar tracker is common in secondary-school and first-year university syllabi. It links to neighbouring topics Photovoltaics, Solar energy, Tracking, so understanding it makes those chapters shorter.
In everyday life: Look for Solar tracker outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Solar tracker in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Solar tracker means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Solar tracker out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Solar tracker in simple terms?

A solar tracker is a device that orients a payload toward the Sun. Payloads are usually solar panels, parabolic troughs, Fresnel reflectors, lenses, or the mirrors of a heliostat.

Why does Solar tracker matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Solar tracker?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Solar tracker.