What Are Solar Collectors? Explore Types of Solar Energy Collectors, Benefits, Cons, and Applications

Solar collectors, also known as solar energy collectors or solar heat collectors, are devices that collect or concentrate sunlight using an absorber plate and convert it to thermal energy to raise the temperature of water or air for domestic and commercial use. Depending on their type, these systems can achieve up to 80% efficiency in converting solar energy into usable heat, which can then be used to raise the temperature of water and air.

The two main types of solar collectors are non-concentrating solar collectors and concentrating solar collectors. 

• Non-concentrating solar collectors: These include flat plate collectors (FPCs) and evacuated tube collectors. 
• Concentrating solar collectors: These include parabolic trough collectors, line focus collectors, and point focus collectors.

Non-concentrating solar collectors catch sunlight and absorb it in the same area. The surface that catches the light and the surface that heats up are essentially the same size; hence, temperatures are modest. On the other hand, concentrating solar energy collectors use mirrors or lenses to collect light from a large area and focus it onto a small receiver. Hence, the resulting temperatures are much higher than those of non-concentrating collectors. 

The main applications of non-concentrating solar collectors include domestic hot water, space heating, and swimming pool heating. Concentrating solar energy collectors can be used for industrial heating and steam generation to rotate a turbine in solar power plants.

In this blog, we will explain what solar collectors are, how they work, their types, applications, benefits, and limitations. We will also explain why photovoltaic solar systems are still more preferred as rooftop solar panel systems for homes, housing societies, and commercial complexes over solar collectors. 

TL;DR Summary Box: What Are the Classifications of Solar Collectors?

Solar collectors are classified into two main categories based on how they capture and concentrate solar radiation: concentrating and non-concentrating systems.

• Concentrating solar energy collectors: They use mirrors/lenses and sun-tracking to focus light onto a small receiver, reaching temperatures up to 400 °C. 
• Non-concentrating solar energy collectors: They use both direct and diffuse sunlight and usually don’t track the sun. Flat plate collectors can attain temperatures between 30-80 °C, and evacuated tube collectors can reach temperatures between 50-200 °C.

Here are the main topics covered in this blog in detail:

What Are Solar Collectors?

Solar collectors are thermal devices that absorb solar radiation and convert it into heat energy for water heating, space heating, and industrial processes. Unlike photovoltaic solar panels that use sunlight to directly generate electricity, solar heat collectors focus on capturing thermal energy (heat) through specialized absorber surfaces.

While different types of solar collectors have different components, the basic operation of all solar energy collectors involves five essential components working together:

• Black absorber plate: This is a dark-colored surface that absorbs maximum possible solar radiation and converts it to heat.
• Glazing cover: This is a transparent barrier that allows maximum sunlight penetration and prevents convective heat loss.
• Heat transfer tubes: These are copper or aluminum conduit pipes that contain the fluid that transports collected thermal energy.
• Insulation backing: This is a thermal barrier that minimizes heat loss through the sides and bottom surfaces of the collectors.
• Support structure: This is a weather-resistant frame that provides secure mounting and component protection. It must be weather-resistant so that the collectors can last for decades despite harsh outdoor weather conditions.

How Do Solar Collectors Work?

The greenhouse effect created by glazing covers traps heat within the collector assembly, allowing flat solar collectors to reach high temperatures that can heat liquid or air. 

Here’s a step-by-step snapshot of how solar collectors work using the greenhouse effect:

• Step 1 – Solar radiation capture: Sunlight passes through the transparent glazing cover and strikes the dark-colored absorber plate surface.
• Step 2 – Solar energy absorption: The black absorber plate absorbs 80-95% of incident solar radiation and converts it into thermal energy.
• Step 3 – Heat generation: Absorbed solar renewable energy heats the absorber plate to temperatures ranging from 30-400°C under optimal conditions, depending on the type of solar collector.
• Step 4 – Greenhouse effect creation: The glazing cover traps heated air above the absorber plate, which prevents convective heat loss to the atmosphere.
• Step 5 – Heat transfer to fluid: The heat transfer fluid (water, glycol mixture, or air) flowing through the tubes absorbs thermal energy from the heated absorber plate.
• Step 6 – Thermal energy transport: The heated fluid carries collected thermal energy through the circulation system to storage tanks or direct application points.

The above-mentioned process is simplified. The actual process will vary depending on the type of solar collector in question. Let’s explore all the major types and how they exactly work.

What Are the Different Types of Solar Collectors?

The two main types of solar collectors are non-concentrating solar energy collectors and concentrating solar energy collectors. The key difference is between the part that catches sunlight (the interceptor) and the part that turns it into heat (the absorber). 

In non-concentrating solar collectors, the interceptor and absorber areas are the same size; hence, the resulting temperatures are moderate. In concentrating solar collectors, a larger light-catching area (mirrors or lenses) focuses sunlight onto a much smaller absorber, which drives the temperature much higher.

Here’s a tabulated snapshot of the differences between the two main types of solar collectors:

Now, let’s check out all types of concentrating and non-concentrating solar energy collectors in detail and understand how they work.

#1. Flat Plate Solar Collectors

Flat plate solar collectors are the most widely used type of solar thermal collectors. They absorb both direct and diffuse solar radiation through a flat absorber surface. These collectors convert solar energy into thermal energy by heating a fluid that flows through tubes attached to the absorber plate. They are ideal for residential water heating, space heating, and commercial applications requiring temperatures up to 80°C.

Here are the key components of flat plate collectors:

• Absorber plate: This black-coated metal surface is made of either copper or aluminum, and absorbs solar radiation and converts it to heat.
• Glazing cover: This is a single or double layer of tempered glass that creates the greenhouse effect and protects internal components of the collector.
• Heat transfer tubes: These are copper pipes that are bonded to the absorber plate and used to transfer the heating fluid.
• Insulation: This is high-temperature mineral wool or polyurethane foam that’s used to insulate the back and sides of the flat plate collector.
• Casing frame: This is the weather-resistant aluminum or galvanized steel casing that makes the collector sturdy enough to withstand harsh weather. 
• Fluid connections: These are inlet and outlet ports with weather-sealed fittings for system integration.

#2. Evacuated Tube Solar Collectors 

Evacuated-tube solar collectors use rows of glass tubes. Each tube holds an absorber and is vacuum-sealed, which sharply cuts heat losses from convection and conduction.

These collectors excel in cold climates and cloudy conditions due to their superior insulation properties. It makes them ideal for regions with harsh winters or variable weather patterns. They can achieve higher temperatures between 50-200 °C while maintaining efficiency in low ambient temperature conditions.

Here are the key components of evacuated tube solar collectors:

• Evacuated glass tubes: These are double-wall borosilicate glass tubes with a vacuum space between inner and outer walls.
• Absorber coating: This is a selective surface coating on the inner tube that maximizes solar absorption and minimizes heat re-radiation.
• Heat pipe or direct flow tubes: These are sealed tubes that contain heat transfer fluid or direct water flow systems.
• Manifold header: This is the insulated distribution system that connects individual tubes to the main circulation loop.
• Reflector panels: These are optional curved reflectors placed behind tubes to increase solar radiation capture.
• Support structure: This is the adjustable mounting frame that allows optimal tilt angle and tube replacement access.

#3. Parabolic Trough Collectors

Parabolic trough collectors are concentrating solar thermal systems that use parabolic-shaped reflective surfaces to focus sunlight onto a receiver tube placed along the focal line of the parabola. 

These systems track the sun throughout the day to maintain optimal focus and achieve temperatures ranging from 150 °C to 400°C for industrial heating applications, steam generation, and solar thermal power plants. 

Here are the main components of parabolic trough collectors:

• Parabolic mirrors: These are curved reflective surfaces, usually silvered glass or polished aluminum, shaped in parabolic cross-section.
• Receiver tube: This is the selective-coated steel tube with a glass envelope, placed at the parabolic focal line.
• Tracking system: This single-axis tracking mechanism follows the sun’s daily path from east to west.
• Heat transfer fluid: This could be synthetic thermal oil, molten salt, or direct steam capable of high-temperature operation.
• Support structure: This is the steel framework supporting the mirrors and receiver tube assembly.
• Control systems: These include automated sun-tracking sensors and positioning controls for optimal solar alignment.

Let’s also check out how parabolic trough collectors work since their functioning is slightly advanced than that of non-concentrating solar energy collectors: 

• Step 1 – Solar concentration: Parabolic mirrors focus direct sunlight onto the receiver tube.
• Step 2 – Sun tracking: The single-axis tracking system rotates the collector assembly to maintain the receiver tube at the focal point throughout the day.
• Step 3 – High-temperature heating: Concentrated solar energy heats the heat transfer fluid in the receiver tube to 150-400°C.
• Step 4 – Thermal energy transport: Hot fluid circulates through the receiver tube to the heat exchanger or thermal storage system.
• Step 5 – Steam generation: In power plant applications, hot fluid generates steam for turbine rotation or industrial processes.
• Step 6 – Energy storage: Excess thermal energy can be stored in molten salt systems for extended operation after sunset.

#4. Line Focus Collectors

Line focus collectors concentrate solar radiation along a linear focal area using various mirror configurations. These include linear Fresnel reflectors and compound parabolic concentrators. 

These systems offer lower concentration ratios than point focus collectors but provide more uniform heating along the receiver length. It makes them suitable for industrial process heating, medium-temperature applications, and distributed thermal energy systems requiring temperatures of 100-250°C.

Let’s check out the key components of line focus solar collectors: 

• Linear reflector array: These include multiple flat or slightly curved mirrors.
• Linear receiver: This is an extended tube placed along the focal line to collect concentrated solar energy.
• Tracking mechanism: The single-axis tracking system follows the sun’s movement throughout the day to absorb maximum heat from sunlight.
• Secondary reflector: This is an optional compound parabolic concentrator to improve solar collection efficiency.
• Heat transfer system: This is the fluid circulation network that transports thermal energy from the receiver to the application point.
• Support framework: This is the structural system that supports reflectors, receivers, and tracking components.

#5. Point Focus Collectors

Point focus solar energy collectors use dish-shaped parabolic reflectors or arrays of heliostats to concentrate solar radiation onto a single focal point. They can achieve high temperatures between 200°C and 1,500°C or more. 

These systems are primarily used for solar thermal power generation, high-temperature industrial processes, and research applications that require extreme thermal conditions. They offer the highest concentration ratios but require precise dual-axis tracking systems.

Here are the key components of point focus solar collectors:

• Parabolic dish reflector: This is the large curved mirror surface shaped as a paraboloid.
• Point receiver: This is a highly efficient heat exchanger placed at the parabolic focal point to capture concentrated energy.
• Two-axis tracking: The dual-axis positioning system maintains alignment with the sun throughout the day and seasons.
• Heat engine or receiver: The Stirling engine, steam generator, or thermal receiver converts concentrated heat to useful energy.
• Control systems: These are sophisticated tracking controls and safety systems that are necessary to maintain high-temperature operation safely.
• Support pedestal: This is the heavy-duty mounting structure that supports the dish assembly and tracking mechanisms.

What Are the Applications of Solar Heat Collectors?

Solar collectors are used across residential, commercial, and industrial sectors for various heating applications. The primary uses include domestic water heating, space heating, swimming pool heating, industrial process heating, steam generation, and specialized applications such as desalination and solar cooling.

Let’s check out all residential and commercial applications of solar energy collectors in detail:

• Domestic hot water heating: These solar heat collectors can supply hot water to homes for bathing, cooking, and cleaning using flat plate collectors or evacuated tube collectors.
• Space heating: These collectors can be used for floor heating, baseboard systems, or forced-air heating.
• Swimming pool heating: They can be used to maintain a comfortable pool water temperature of 25-30°C using unglazed or glazed solar heat collectors with large surface areas.
• Commercial water heating: They can be used to supply hot water at hotels, restaurants, hospitals, and office buildings using multiple collector arrays and high-capacity storage systems.
• Industrial process heating: They can provide thermal energy up to 100°C for food processing, textile operations, and chemical manufacturing.
• Agricultural uses: These include crop drying, greenhouse heating, and livestock facility heating.
• Steam generation: Concentrating solar collectors can produce high-pressure steam above 200°C for industrial processes and power generation.
• Solar power plants: Large-scale concentrating collector plants generate electricity through steam turbines using parabolic troughs, solar towers, or dish-engine systems.
• Solar cooling: Solar collectors can power absorption chilling systems for space cooling using thermal energy instead of electricity. It’s particularly effective in hot, sunny climates.

What Are the Advantages of Solar Energy Collectors?

The main advantages of solar energy collectors include high energy efficiency, reduced power bills, and environmental sustainability. 

Let’s check out all the main advantages of solar heat collectors in detail:

• High energy efficiency: Solar collectors achieve up to 80% conversion efficiency, making them highly effective for thermal applications.
• Reduced energy bills: Instead of using expensive grid electricity for heating water or air, you can use solar collectors for the same purpose. This will substantially reduce electricity, gas, or LPG consumption and monthly utility expenses.
• Low operating costs: The only fuel solar collectors require to operate is sunlight, which is free.
• Zero carbon emissions: Solar collectors produce no greenhouse gas emissions during operation. 
• Renewable energy source: They utilize solar energy, which is inexhaustible. 
• No air pollution: These systems produce no harmful emissions, smoke, or pollutants. As a result, they can also improve the air quality index and tackle the problem of air pollution. 

What Are the Disadvantages of Solar Energy Collectors?

The major disadvantages of solar energy collectors include weather dependency, high initial costs, space requirements, and performance limitations in certain conditions.

Let’s check out the limitations in detail:

• High initial investment: Upfront costs for residential systems can be substantial.
• Weather dependency: Performance reduces during monsoon seasons and cloudy days, requiring backup heating systems for a consistent hot water supply.
• Significant space requirements: Collectors require 12-14 m² of unshaded roof space with proper orientation in large-scale installation. 
• Shading sensitivity: Even partial shading from trees, buildings, or other structures can significantly reduce collector performance throughout the day.

Solar Heat Collectors vs Solar Photovoltaic Systems: Which One is Better For Rooftop Solar at Homes?

While solar heat collectors can only supply hot water to homes, rooftop on-grid solar systems that use the PV technology can power all home appliances, including water heaters, ACs, lights, TVs, refrigerators, and fans. Not only will solar PV systems take care of hot water requirements, but they can also reduce the electricity bills at homes by 90% or more.

If you want to see your electricity bills become zero and run your entire household on solar electricity, an on-grid PV rooftop solar system is the best option because of the following benefits it offers:

• You will receive a subsidy: Homeowners and housing societies installing on-grid rooftop solar systems receive a subsidy under the PM Surya Ghar Muft Bijli Yojana. However, this subsidy is not offered for commercial rooftop systems, off-grid solar systems that use a lithium battery bank instead of the grid, and ground-mounted solar systems.
• The entire household runs on solar energy: When sized appropriately, a solar cell power plant can easily run an entire household, reducing reliance on grid electricity to such an extent that electricity bills drop by 90%, and in many cases, become zero.
• It reduces the carbon footprint significantly: Installing something as small as a 3 kW on-grid solar system is equal to planting 118 full-grown trees that can offset 77,616 kg of carbon dioxide from the atmosphere in 25 years.

Now, let’s give you a head-on comparison between the estimated cost of installing an on-grid rooftop solar system with SolarSquare in a city like Nagpur vs the substantial savings our solar systems offer in 25 years of their life:

*Please note: The above-mentioned solar panel price is indicative as of 9th September 2025 for the SolarSquare Blue 6ft variant. The final cost of installing an on-grid rooftop solar panel system at home depends on your DISCOM charges, product variant opted for, panel type, inverter type, mounting structure height, type of after-sales service, savings guarantee, roof height, etc. Prices are subject to change. Additionally, while calculating savings, we have considered the annual tariff escalation at 3% and the annual degradation at 1%. The actual final savings from solar panel installation depend on the types of solar panels you’ve installed and their efficiency, intensity of sunlight your rooftop receives, orientation of the panels and tilt angle, the pollution level and weather conditions in your city, the temperature, shadow on the roof, impact of dirt/dust, and how well you maintain your panels after installation.

Want to get an estimate of solar savings vs the installation cost with SolarSquare in your city? Use our free solar panel calculator now. For any further queries, book a free solar consultation call with our experts.

Conclusion 

Solar collectors are thermal devices that capture solar radiation to heat water or air, which can be used for residential, commercial, and industrial applications. With conversion efficiencies reaching up to 80%, these systems offer financial and environmental benefits. 

The selection between flat plate collectors, evacuated tube systems, or concentrating solar heat collectors depends on specific climate conditions, temperature requirements, and budget considerations.

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FAQs

Q1. What are the two types of solar collectors?

Ans. The two main types of solar collectors are non-concentrating solar collectors that include flat plate solar collectors and evacuated tube collectors, and concentrating solar collectors that include parabolic trough collectors, line focus collectors, and point focus collectors.

Q2. Are solar collectors the same as solar panels?

Ans. No. Solar collectors use solar thermal energy to generate heat for water or air. Solar panels (PV), on the other hand, use sunlight to produce DC electricity, which can power all household appliances. While both use sunlight, they do different jobs.

Q3. What are solar collectors made of?

Ans. Most solar heat collectors have a dark metal absorber with a selective coating, a tempered-glass cover, insulation, pipes, and a weatherproof frame. Evacuated tubes use vacuum glass tubes with a heat pipe, and concentrating collectors use mirrors or lenses and a receiver.

Q4. How efficient are solar collectors?

Ans. The efficiency depends on the type of solar collector in question. For instance, flat plate solar collectors can be up to 70% efficient and parabolic trough collectors can be up to 80% efficient.