What is Solar Cooling? Techniques, Benefits, Cons, and Working of Solar Cooling Systems

Solar cooling refers to the technology and techniques that use the sun’s heat to run special chillers for air conditioning. In simple terms, a solar cooling system is a thermal setup that uses solar thermal collectors to gather heat from sunlight, which in turn drives specialized cooling cycles that produce chilled water for maintaining comfortable indoor temperatures. 

When outdoor temperatures rise during the summer seasons and the cooling demand skyrockets, the availability of solar energy is also at its highest limit. This natural synchronization between cooling demand and solar radiation availability makes solar cooling systems effective in reducing peak electricity demand and grid stress.

The main technologies in solar cooling that are widely used include absorption chillers, adsorption chillers, desiccant cooling, and ejector refrigeration cycles. Although they all use solar energy to generate the cooling effect, they differ from solar photovoltaic systems. 

Solar systems use solar panels to produce electricity, which can be used to power regular ACs for cooling. However, a solar cooling system uses solar collectors to capture the sun’s thermal energy. The collected heat is then used to power specialized chillers that produce air conditioning. 

On-grid rooftop solar panel systems for homes are far more popular and beneficial than solar cooling systems because they generate free solar electricity to power every home appliance, not just the AC, reducing electricity bills by 90% or more. 

In this blog, we will explain what solar cooling is, different techniques used for solar cooling, the benefits and limitations of the solar cooling technology, and compare solar cooling and heating. We will also explain how solar cooling systems differ from solar PV systems, and why installing on-grid rooftop solar systems for housing societies and homes is far more beneficial than solar cooling systems. 

TL;DR Summary Box: What is the Working Principle of Solar Cooling Systems?

The working principle of solar cooling systems revolves around solar collectors capturing the sun’s thermal energy and using the heat generated to produce chilled water for air conditioning.  

The entire working principle operates through a four-stage cycle that starts with solar heat collection and ends with chilled water production.

Here are the four steps involved in how solar cooling works:

• Heat collection: Solar thermal collectors capture and convert sunlight into thermal energy. This thermal energy heats a working fluid to temperatures between 70°C and 100°C.
• Generator phase: The hot fluid enters the chiller’s generator, where it separates refrigerant from an absorbent solution through heat application.
• Cooling cycle: The separated refrigerant vapor condenses and then evaporates in an evaporator, absorbing heat from a water loop.
• Chilled water production: The cooled water provides air conditioning, and the refrigerant returns to the absorbent solution.

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

What is Solar Cooling?

Solar cooling is an advanced technology that uses a solar cooling system to convert the sun’s thermal energy into air conditioning through specialized refrigeration cycles. The system uses solar heat collectors to capture heat from sunlight. Then, it delivers the thermal energy to absorption or adsorption chillers that produce chilled water for cooling an entire building.

The solar cooling technology works on thermodynamic principles, where collected solar heat powers refrigeration cycles to remove heat from indoor spaces. Unlike photovoltaic systems, which convert sunlight into electricity, solar cooling uses thermal energy to generate the cooling effect.

What Are the Key Components of a Solar Cooling System?

A solar cooling system is made of multiple components, including solar thermal collectors, a thermal storage tank, absorption or adsorption chillers, heat exchangers, and circulation pumps. 

Let’s learn the specific roles of each component of a solar cooling system:

• Solar thermal collectors: These could be flat plate collectors, evacuated tube collectors, or concentrating collectors that can achieve the high temperatures required for chiller operation.
• Thermal storage tank: This is an insulated water storage tank or Phase Change Material (PCM) system that stores excess heat for nighttime or cloudy weather operation.
• Absorption/adsorption chiller: This is the core solar cooling unit. It uses the stored or real-time thermal energy to drive a thermodynamic cycle that produces chilled water.
• Heat exchangers: It’s the equipment that transfers thermal energy between different fluid circuits. They allow heat to transfer from one fluid stream to another without mixing the two. This way, energy is shared, but the fluids stay separate.
• Circulation pumps: They keep water or other fluids flowing through the collectors, the storage tank, the chillers, and the pipes. Without pumps, the solar cooling system would be unable to transport heat where it is needed.

How Does Solar Cooling Work?

Solar cooling works through a special system that captures heat from the sun and converts it into cooling for buildings. Heat collectors collect the sun’s thermal energy as heat. The collected heat is either stored in thermal storage or used directly. 

Before we take you through the step-by-step process, here are two important terms you should understand: 

• Refrigerant: This is the fluid that boils and later evaporates at a low temperature. When it evaporates, it absorbs heat, causing the surrounding area to cool. In many absorption chillers, this is just water.
• Absorbent: This is a liquid that soaks up the refrigerant vapor to ensure the cooling cycle can continue. A common absorbent is the lithium bromide solution.

That said, now let’s check out the entire process of how solar cooling works in simple steps:

• Step 1 – Solar heat collectors capture the sun’s thermal energy: Evacuated tube or flat-plate collectors absorb solar radiation and use it to heat a glycol-water mixture to 70-100°C.
• Step 2 – The generator uses the solar heat: The hot glycol-water transfers its heat to the chiller’s generator. Inside, a lithium bromide water solution is heated, causing the refrigerant to boil out as vapor.
• Step 3 – The condenser removes the heat: The refrigerant vapor moves to the condenser, where it releases its heat to the surrounding outdoor air or water. It turns from vapor back to liquid.
• Step 4 – The expansion valve lowers the pressure: The liquid refrigerant passes through a small valve. As its pressure drops, the temperature drops with it.
• Step 5 – The evaporator produces chilled water: At this stage, the refrigerant enters a low-pressure zone and evaporates at a low temperature. While it evaporates, it absorbs heat from the chilled-water loop. This process lowers the water temperature, which is then circulated through the building to provide a cooling effect.
• Step 6 – The absorber takes the vapor back: The refrigerant vapor leaving the evaporator is absorbed back into the absorbent. 
• Step 7 – The solution loop closes the cycle: A small solution pump sends the now-diluted solution through a solution heat exchanger and back to the generator. The generator reheats the solution, more refrigerant boils, and the cycle continues.

What Are the Main Types of Solar Cooling Techniques? 

The four main types of solar cooling techniques include absorption chillers, adsorption chillers, desiccant cooling systems, and ejector refrigeration cycles. These solar cooling techniques primarily differ based on the working fluids they use and the operating mechanisms they employ to achieve the cooling effect. 

• Absorption chillers: They use liquid absorbents through chemical processes.
• Adsorption chillers: They use solid materials like silica gel.
• Desiccant cooling systems: They focus on removing moisture for evaporative cooling. 
• Ejector systems: They use steam jets to create vacuum-driven refrigeration.

Before we take you through the ins and outs of all four types of solar cooling techniques, let’s take a look at the key differences between them:

Now, let’s check out all these types and learn a bit about how they generate the cooling effect in detail.

#1. Absorption Chillers

They’re the most widely used solar cooling technology. In these chillers, solar-heated water provides the energy to run the refrigeration process. The process itself is called the absorption cycle. 

Here, a refrigerant, such as water, is boiled out of a liquid mixture, typically lithium bromide-water or ammonia-water, using solar heat. The refrigerant then undergoes a series of steps, including condensation, expansion, and evaporation, which create chilled water.

#2. Adsorption Chillers

These chillers use a solid material such as silica gel or zeolite to hold the refrigerant vapor on its surface. 

When solar heat is applied, the material releases the vapor. The refrigerant then goes through steps such as condensing, expanding, and evaporating that produce chilled water. These systems often run in batches and are suitable for smaller or remote installations.

#3. Desiccant Cooling

This solar cooling technique is used when the main need is to handle humid air. In these systems, solar-heated water provides the energy for regeneration. The process is called desiccant dehumidification. 

Here, a desiccant wheel or bed removes moisture from the incoming air, thereby drying the air. Solar heat then regenerates the desiccant, allowing it to continue working. The dried air is cooled using evaporative cooling and supplied to the building. This approach works especially well in hot and humid climates.

#4. Ejector Refrigeration

Ejector refrigeration is a simple type of solar cooling technique that works well when high-temperature heat is available. 

In these systems, solar collectors heat water to about 80 to 120 °C to produce steam or another vapor. This vapor is sent through a device called an ejector, which creates a low-pressure zone. At this low pressure, the refrigerant evaporates and absorbs heat, producing chilled water for cooling. The vapor is then condensed, and the process repeats. 

Because the design is straightforward with few moving parts, ejector systems are robust, but their efficiency is lower compared to other solar cooling methods. They are mostly used in industrial settings and for recovering waste heat.

Solar Cooling Systems vs Solar Photovoltaic Systems: Which Is Better and Why?

While both use sunlight, solar cooling systems and solar PV systems differ significantly from each other. A solar cooling system uses solar thermal energy to provide the cooling effect. On the other hand, a solar PV system employs high-efficiency solar panels to convert sunlight into electricity directly. This electricity can then be used to power not just your regular air conditioner but all other home appliances. 

On-grid residential and commercial rooftop solar systems are more effective than solar cooling systems in achieving energy independence. Unlike solar PV systems, a solar cooling system cannot generate electricity to power any other appliance.

Using a rooftop on-grid solar system is particularly beneficial in homes and housing societies with a reliable grid because of the following reasons: 

• The government offers financial assistance for installing them: Homeowners and housing societies receive a subsidy under the PM Surya Ghar Muft Bijli Yojana for installing on-grid rooftop solar systems. This assistance is not provided for the installation of solar cooling systems, off-grid solar systems, or ground-mounted solar systems.
• They’re cost-effective and reduce electricity bills by 90%: Unlike off-grid and hybrid solar systems, which require expensive batteries, on-grid solar systems are connected to the grid. Any excess solar energy they produce is sent to the grid. Since they do not need expensive lithium batteries to store solar energy, they’re extremely cost-effective. When sized based on a home’s actual annual energy consumption, on-grid rooftop solar systems can reduce the bills by 90% or more.

Here’s a detailed table comparing solar cooling systems and solar photovoltaic systems:

If you want to check the cost of installing a solar photovoltaic system in your city vs the savings this system can offer in 25 years, you can use SolarSquare’s free solar panel calculator.

For added clarity, we’ve also chalked down a snapshot of the estimated cost of installing a 5 kW solar system in India vs the money it will save for homeowners in 25 years of its life:

*Please note: The 5 kW solar panel price in India with subsidy mentioned above is indicative as of 1st October 2025 for the SolarSquare Blue 6ft variant. The actual solar plate price depends on your DISCOM charges, city, 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, when calculating savings, we have considered an annual tariff escalation of 3% and an annual degradation of 1%. The actual final savings from a 5 kW solar system depends 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.

Solar Cooling vs Solar Heating

While both technologies use solar collectors and sun’s thermal energy, they’re quite different from each other in purpose. Solar heating uses solar thermal energy directly to produce hot water for space heating, radiant floors, and domestic hot water. Solar cooling, on the other hand, uses solar thermal energy at higher temperatures to drive absorption chillers, which produce chilled water for air conditioning. 

Here’s a tabulated snapshot to help you understand how solar heating and cooling differ:

Are Solar Heating and Cooling Systems the Same or Different?

Solar heating and cooling systems differ in their operation, despite both using the solar thermal collectors. 

Solar heating systems deliver captured thermal energy directly to building spaces through radiators or radiant floors. Solar cooling systems, however, route the captured thermal energy through absorption or adsorption chillers that use heat to drive refrigeration cycles and produce chilled water for air conditioning.

Are Solar Heating and Cooling Techniques the Same or Different?

Solar heating and cooling techniques employ identical solar thermal collection methods but differ significantly in their energy conversion and distribution approaches. 

• Solar heating techniques: They employ straightforward thermal energy capture and distribution. Solar collectors heat a working fluid, storage tanks hold thermal energy, and pumps circulate hot water to heating equipment. 
• Solar cooling techniques: They use thermal energy to drive absorption or adsorption cycles, which separate, condense, and evaporate the refrigerant to produce chilled water for air conditioning.

What Are the Advantages of a Solar Cooling System?

Solar cooling systems can reduce stress on the grid during summers when the demand for cooling is very high, as solar energy is also at its peak during the summer season. They are also beneficial for the environment because, unlike HVAC systems, they do not release carbon emissions during operation. 

Here are the main advantages of a solar cooling system:

• They reduce stress on the grid during summers: As solar energy is available in bulk, solar cooling systems can take the load off from the grid by cooling an entire building. 
• They can cut down electricity bills to an extent: Since they reduce the indoor temperatures, they reduce reliance on traditional air conditioners. As a result, electricity bills in the summer can be reduced to some extent. However, they will not provide complete energy independence, as other appliances will still consume electricity from the grid. For energy independence and 90% lower bills, consider installing a solar PV system.
• They use clean refrigerants: Most solar cooling systems use water or ammonia, which do not harm the ozone layer and have a very low global warming impact.
• They run quietly: With no large compressors, they make less noise than many conventional AC systems.

What Are the Limitations of Solar Cooling?

The biggest limitation of solar cooling is that, unlike PV systems that generate electricity, solar cooling systems can’t generate electricity. Hence, they fall short in helping you achieve the energy independence that rooftop photovoltaic systems can offer. 

Let’s check out all the limitations of solar cooling systems in detail:

• They can’t generate electricity: Unlike PV systems, solar cooling systems cannot convert sunlight directly into electricity.
• They can’t offer independence from grid electricity: While they do reduce reliance on grid electricity by handling air conditioning, they can’t offer complete energy independence, as all other appliances need electricity to work. 
• They’re expensive to install: The cost of a solar cooling system can be two to three times that of a conventional HVAC system.
• Their performance is heavily dependent on weather: Unlike high-efficiency bifacial solar panels, which can use diffused sunlight, solar cooling systems require strong and direct sunlight to operate efficiently. As a result, their output drops sharply under cloud cover.
• Maintenance is complicated: It requires specialized skills to maintain chillers and other components, such as heat collectors, to ensure the solar cooling system operates optimally. 

Conclusion 

Solar cooling is a renewable energy option for air conditioning without relying on expensive grid electricity. It uses heat from sunlight to operate absorption or adsorption chillers, which produce chilled water for air conditioning. Solar cooling works well in the summer because the strong sun and high cooling demand happen at the same time.

While solar cooling can certainly reduce electricity bills to some extent, if you’re exploring options to achieve complete energy independence, consider rooftop solar PV systems instead. For any further information on how rooftop solar systems can reduce your electricity bills by 90%, you can book a free solar consultation call with SolarSquare now.

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FAQs

Q1. Can solar be used for cooling?

Ans. Yes, solar energy can be used in multiple ways for cooling. Solar cooling systems use the sun’s heat to operate specialized chillers that produce chilled water for air conditioning. On the other hand, a solar PV system can produce electricity, which you can use to run your regular air conditioners.

Q2. Are solar cooling systems and solar panel cooling systems the same?

Ans. No. Solar cooling systems use thermal collectors to make cooling. Solar panel cooling systems, on the other hand, usually refer to regular PV systems that generate electricity, which can then power a standard air conditioner.

Q3. How do solar coolers work?

Ans. Unlike solar cooling technology, solar air coolers use evaporative cooling, not refrigeration. A fan pulls hot air through wet pads. As the water evaporates, the air cools and is blown indoors. The fan and pump can run on power from solar panels or a small battery.