Buying Solar Trackers?

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Solar Trackers are devices that come in conjunction with the mounting structures and help direct the panels in the direction the sun moves.

As the solar industry progresses, developers are increasingly becoming aware of the enhanced CUFs that tracker implementation can bring about. But being a nascent market, there is a lot of uncertainty in selecting the best trackers for a solar power plant, especially with regard to cost savings and generation output per MW they could bring about.

Solar Mango, the #1 Solar Guide, can assist you in choosing the most appropriate solar tracker.

A single axis system is most commonly used for most standard PV Power Plant. Single axis solar trackers rotate in one direction moving back and forth. These types of trackers usually have simple levers which can be used to tilt the panels depending on the season so that it can harness the maximum energy from the Sun.

Single-axis trackers make sense in the Southern states due to their proximity to the equator.

Dual-axis trackers

Dual axis systems – as indicative of the same – move in two directions, on both the horizontal and the vertical axis making complete use of the sun’s rays for the entire day. With a Dual Axis Tracking system more energy can be generated from a given land area, as compared to Fixed tilt installation or Single Axis.

In northern parts of India like Punjab, Rajasthan etc, which are located at a higher latitude, these could be beneficial. They can produce an increase in performance of up to 35%.

Why trackers are gaining acceptance in Indian solar power plants?

• Solar System with trackers can bring about a CUF of 21%. In comparison with solar plants without trackers, this means an increase in performance of around 20-25%.
• Nowadays, most EPCs guarantee a power production of 19 lakh units with trackers in comparison to 15-16 lakh units without them.
• During high wind conditions, the panels are aligned horizontally to reduce the load on the panels and the mounting structure thereby prolonging the life of the power plant.

These are questions for which a non-expert will need guidance, especially considering how a wrong choice could mean considerable monetary losses over the long term.

How to Ensure You Are Selecting the Right Trackers for Your Solar Plant?

One aspect that many developers are concerned about when it comes to use of trackers is the extra maintenance required. Many of them have misgivings as to whether trackers could impose significant maintenance costs, and whether trackers could break down often, leading to disruption in the solar power plant operations and output.

The decision to opt for a superior tracker technology can be an enduring task for a non-expert who doesn’t possess the much-needed expertise.

However, there is a simple and effective method for even non-experts to ensure quality of the solar trackers – buy it from the right tracker company.

Take Solar Mango Assistance in Choosing the Right Vendor for Solar Trackers

Solar Mango can be of invaluable assistance to you in selecting the optimal vendor for supplying solar trackers.

Here’s why.

Selection of Trackers is More Challenging

Unlike many other components of a solar power system, selecting a tracker is more challenging because of the following reasons:

1. It is the only component in a solar pv system that has moving parts so selection needs to focus on a trouble-free, low maintenence system
2. Use of trackers in Indian solar power plants has been a recent phenomenon, and hence little information is available from real life installations
3. There are both Indian and international tracker brands available, and each has its own set of features and unique selling points, making comparison and selection quite intricate

Solar Mango’s Expertise in the Solar Sector

Solar Mango is one of the most respected brands in the Indian solar sector. Considered the #1 solar guide, our expertise in the technical, market and commercial aspects of solar energy has benefitted over 1500 stakeholders – ranging from industries, commercial establishments, small businesses, entrepreneurs, government, educational institutes and more.

Through our focused consulting assignments and research reports, and our team of industry specialists, we bring in in-depth expertise in many critical aspects of solar power, especially solar PV.

Solar Mango’s Contacts in the Indian Solar Sector

Being a pioneer in solar power industry research and consulting (we have been serving the Indian solar power market since 2009 when the solar power growth was just beginning), and also owning some of the leading online resources for solar energy in India, Solar Mango has one of the most extensive contact networks with vendors, specialists and experts in the field.

Vendors We Work With

Over the last decade, we have interacted extensively with solar tracker manufacturers in the country and have an exceptional understanding of the solar industry. Our interactions with these vendors have been in all the key dimensions – technical, strategic, operational and marketing.

During this period, based on our work, we have identified select vendors who are the top of the heap when it comes to the key parameters – quality, reliability and flexibility.

We work with vendors both small and large, and having operations in different regions in India. While specifics of our vendors vary, all of them have some things in common – very high quality and reliability.

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Trackers FAQs

Why are trackers needed?

Solar panels generate most electricity when the they are perpendicular radiation from the sun. That is, the angle of incidence is 0°. (The angle that a ray of light makes with a line perpendicular to the surface.) As the sun goes from east to west, the angle of incidence on a horizontal surface, e.g. from -45 to +45°. Further the seasonal movement of sun in the sky (which happens because the earth’s axis is tilted at 23.45° from the perpendicular to its plane of orbit around the sun).

Figure: Sun’s trajectory in the sky during different times of the year. Source: Phy6.org

In solar plants, tracker (one tracker operates a set of modules) changes the orientation of modules to follow the sun throughout the day to minimize the angle of incidence of the solar radiation on the panels. This significantly increases the energy captured by the plant. In other words, they increase the capacity utilization factor (CUF).

When to use trackers for my plant?

Trackers are used in majority of MW-scale commercial solar plants, but, in India, haven’t been used in residential rooftop plants.

With panels following the sun, the production per kW or CUF can increase by 25–35%. If space is a constraint, solar trackers are a good choice to generate more output from the same amount of land. If land is not a limitation, it can make more sense to buy more solar panels as trackers are expensive.

Can trackers be used for grid-tied residential rooftop solar plants?

Tracking is also not suitable for typical residential rooftop photovoltaic installations. We have not seen trackers being employed for residential rooftop solar installations in India. Since the panels tilt during the day, they need to be offset a significant distance from the roof, which requires expensive racking and increases wind load. Also, this will not be very aesthetic for rooftops. Hence, tracking is unlikely to ever be used in such installations. Further, as the cost of photovoltaic modules continues to decrease, which makes increasing the number of modules for more power the more cost-effective option.

However, in countries like United States and Australia, tracking has been been applied for ground mount solar, where greater freedom of movement is possible. Whether trackers can help in getting more energy rather than just adding more panels (considering area is not a constraint) depends on particular parameters of the case.

But if I use trackers, won’t a lot of additional maintenance efforts be required?

One aspect that many developers are concerned about, when it comes to use of trackers is the extra maintenance required. Many of them have asked us at Solar Mango whether the trackers could impose significant maintenance costs, and whether trackers could break down often, leading to disruption of plant output. We can say that these fears are unjustified, as long as you procure the tracker solution from a reputed company. Yes, trackers have moving parts and hence require regular maintenance, mainly regular inspection and lubrication. However, the tracker movements are slow and gradual, and not subject to the same wear and tear that a fast running motor would, for instance.

In summary, trackers supplied by reputed companies, from an Indian or an international company, will be able to provide you with a significantly higher output at the cost of only a marginal increase in maintenance efforts and costs.

What do single axis and dual axis trackers mean?

Single axis solar trackers: They rotate around one axis moving back and forth (a single degree of freedom). It maximizes the energy captured from the sun by following it from east to west during the day. There are four types of single axis trackers based on the alignment of the axis: horizontal, vertical, tilted and polar aligned.

Dual axis solar trackers: These trackers follow the sun better than single axis trackers as they move with two degrees of freedom. Apart from following the sun east to west daily, it also follows it in the north-south direction with changing seasons.

How do these trackers actually change the orientation of the solar panels?

Trackers can be classified as active or passive based on their mechanism.

• Passive trackers depend solely on solar heat to guide and move the tracker. Basically, a low boiling point compressed gas fluid is driven to one side or the other to move the tracker like a see saw.
• Active trackers use a controller that monitors the position of the sun’s movement in order to direct motors that move the trackers.
  In most active solar trackers, Light Dependent Resistors (LDRs) are used as sensor. Their difference in output is used to generate error signals. In these systems, for instance, when the outputs of eastern and western LDRs become equal, the east to west tracking ends. A computer or a processor calculates the sun’s position from formulae or algorithms using its time/date and geographical information to send signals to the motor orient the apparatus in such direction where illumination of sensors becomes equal and balanced.
  In some high-end active solar trackers, a feedback system is employed to correct any errors and compensate for disturbances in the system.

What are horizontal single axis trackers? How do they compare to vertical axis trackers?

Utility-scale and large projects usually use these horizontal single-axis solar trackers or HSAT (dual-axis trackers are mostly used in smaller residential applications). The axis of rotation for HSAT is horizontal with respect to the ground. Panels are mounted on a cylindrical tube that is aligned in the north-south direction and supported on bearings. The tube rotates so panels can track the sun horizontally (i.e. in east-west direction). The plant layout with horizontal single axis trackers is simple as all that needs to be done for appropriate relative positioning of the trackers is to keep the axes of rotation of trackers parallel to each other.

Typically, in HSAT, the module can be mounted parallel to the axis, that is, the inclination is zero and the face of the panel lies parallel to the rotating cylindrical tube. For higher latitudes, however, the modules can be tilted to capture more energy from the sun. HSAT with tilted modules combines the advantages of the vertical single axis trackers without taking as much land area, therefore being more cost effective.

Vertical-axis trackers are suitable for high latitudes because of their fixed or adjustable angles.

Are any special considerations required for the planning plant layout if trackers are used?

Trackers increase energy capturing by panels at the beginning and end of the day when the sun is near the horizon. As an example, when the sun is 10° above the horizon, the energy available from solar radiation is around 50% or even more than at solar noon. Facing the panels towards the sun at these times can significantly increase plant performance, but at the same time the panels form long shadows. Hence, spacing is important to avoid loss of production from shadowed panels and maximize the economic benefit from the use of trackers. Good spacing can maximize the ratio of energy production to cost, which will depend on local terrain and shading conditions, as well as time-of-day value of the energy produced.

How to decide whether between single axis or dual axis trackers?

This depends on the location! In South Indian states, dual axis trackers don’t justify the additional investment required as these states are in close proximity to the equator. Note that closer to the equator, there is less movement of the sun in the sky in the north-south direction from season to season, so there is not much increase in output over single axis trackers, if dual axis trackers are used. Inn northern states like Punjab and Rajasthan, dual axis trackers could make senses. But, in India mostly single axis trackers have been used.

How do these trackers actually change the orientation of the solar panels?

Trackers can be classified as active or passive based on their mechanism.

Passive trackers depend solely on solar heat to guide and move the tracker. Canisters containing a low boiling point compressed gas fluid are fixed to the sides of panel array. As the liquid in the unshaded canister heats up, it expands into a gas, which pushes the heavier liquid to the shaded canister, shifting the weight to that side of the array, which causes it to rotate.

Active trackers use a controller that monitors the position of the sun’s movement in order to direct motors that move the trackers.

In most active solar trackers, Light Dependent Resistors (LDRs) are used as sensor. Their difference in output is used to generate error signals. In these systems, for instance, when the outputs of eastern and western LDRs become equal, the east to west tracking ends. A computer or a processor calculates the sun’s position from formulae or algorithms using its time/date and geographical information to send signals to the motor orient the apparatus in such direction where illumination of sensors becomes equal and balanced.

Are there manual solar trackers also available in the market?

In cases of some developing countries, trackers are used where manual operators replace the drives. This requires labor for the manual operation, while providing jobs to local people. This is not a significant solution in the Indian context.

How accurate are solar trackers in following the sun?

Usually, you find that trackers are able to track the sun horizontally (the east to west movement) with an accuracy of ±0.5°C.

Does the tracker follow the sun till it sets and then go back to the original position for the next day?

That is a good question. The trackers don’t simply follow the sun till it below the horizon. Towards the end of the day, if the solar panels are tilted towards the sun at a low height above the horizon, they can get shadowed reducing the energy production. If you have several panels in a row from east to west, there will be no shading during solar noon (sun is at zenith). But in the afternoon, panels could be shaded by their west neighboring panel if they are sufficiently close. First, this has implications for designing panel spacing. Secondly, most plants nowadays use “backtracking” (an optimization algorithm employed by the control system) to smoothen the daily production curves and prevent shading losses. For utility-scale projects affected by shading, backtracking has been known to increase output by 5-10%.

Are trackers something that is designed and supplied by a separate vendor from the mounting structure?

No, a tracker is in itself the mounting system, and distinct from the fixed (i.e. non-tracking) mounting system.

Just for illustration, a particular dual axis tracker has the following specification:

Note that one tracker … In the spec list, the number of panels that can be mounted on this tracking mounting system is given as 4 X 12 with total panel surface area of 85 m². As this is a dual axis tracker, both azimuthal sweep (to follow sun from east to west) and inclination angle (which will vary according to sun’s north-south movement in the sky) are mentioned.

How much do these trackers cost?

Prices vary depending on the type of tracker you choose. The double axis solar trackers add around 15-20% and single axis solar trackers cost around 8-10% to the cost of setting up a solar plant. Depending on your energy needs, you may need more than one tracker.

How heavy are trackers and how much energy will the trackers additionally consume?

The trackers weight will vary a lot, from a fraction of a ton to many tons, according to how to how much maximum panel area can be mounted. Even for a given maximum panel surface, the weight can vary according to the construction. The energy consumed will also similarly vary. Just to give an idea, for a system that is measuring a 5 tons, it could consume little more than 50 kWh in a year, which would be a single 250 kW panel’s energy production in 1–2 months.

How much area is required?

Employment of trackers necessitates a greater land area to place the panels. As such, for a 1 MW plant, the use of trackers will increase the area by around 5 acre to 6 acre (20% increase in area required).

What will be rate of return for extra investment in trackers?

Let’s say you are putting up a 1 MW power plant. Consider the following parameters with and without trackers as given in the table below.

Assuming a PPA tariff of Rs 7/kWh, the extra revenue generated (inclusive of O&M costs) when trackers are employed is a 4 Crores/MW for the entire lifetime. So, there’s is an additional revenue of 4 Crores for an extra initial capital of 40 lakhs. Besides, the additional capital expense of Rs 40 lakhs usually pays back within 2 years owing to the extra generation. These numbers show that it’s a very clear decision to go for solar trackers.