Solar PV vs Solar Thermal: What's the Difference?
Solar energy is the renewable energy that comes from the sun. However, the way we capture and convert it into usable energy can differ.
There are essentially two different ways of using solar energy to generate power. They are solar PV(photovoltaic), and solar thermal. The main difference is in how these technologies capture and convert sunlight into usable energy.
Solar PV uses solar panels made of semiconductor materials to convert sunlight into electricity. While solar thermal uses the sun's energy to heat up a fluid (typically water), which is used either for space heating, generating hot water, or producing steam to generate electricity.
Solar PV is used in both residential and commercial settings, whereas solar thermal is more commonly used in industrial settings.
Let's take a closer look at each one now to see how they work.
What is Solar PV?
Solar PV is a technology that uses solar panels to convert sunlight into electricity. This is achieved by using solar cells made of semiconductor materials.
When sunlight hits the solar cell, it causes an electrical reaction that generates an electric current. This current can then be used to power electrical equipment or it can be stored in batteries for later use.
The amount of electricity generated depends on the size and type of panel, as well as the amount of sunlight it receives.
Solar PV cells are made out of materials like silicon, cadmium telluride, or copper indium gallium selenide (CIGS). Silicon is the most common material because it has a high conversion efficiency and it's relatively cheap to produce.
Solar PV systems are an excellent choice for generating electricity to power small appliances or electronics. Most homeowners can generate enough electricity to offset a portion of their power bill if they have enough installation space and sun exposure on their homes.
Solar PV is also used in larger-scale applications, like utility-scale solar farms.
Almost all solar PV systems necessitate the use of a battery to store the energy generated. This is due to the fact that solar PV only generates electricity when the sun shines.
By storing electricity in batteries, it can be used at night, during cloudy weather, or whenever there is a high demand for energy.
Solar panels by themselves aren't enough to generate electricity. They need to be used in conjunction with other equipment, like an inverter and a controller.
An inverter is a device that converts the direct current (DC) output of the solar panels into alternating current (AC). This is the type of electricity that's used in homes and businesses.
The controller ensures that the system operates safely and efficiently. It also monitors the system to make sure it's producing the most energy possible.
What is Solar Thermal?
Solar thermal is a technology that uses the sun's heat to heat up a fluid to a high temperature. This heated fluid can then be used for a variety of purposes, like conditioning air, generating electricity, or producing hot water.
Although solar thermal can generate electricity, it is not as widely used as solar PV for this purpose. It is more often preferred for applications that require heating a space or generating hot water.
In industrial settings, solar thermal is often used for heating water to produce steam. This steam can then be used to drive turbines that generate electricity.
Solar thermal can also be used in a process called absorption cooling. In this process, the heat from the sun is used to power a refrigeration system. This type of system is often used in commercial buildings to cool the air inside.
Solar thermal power plants capture and concentrate sunlight to produce high-temperature heat for electricity production. These plants consist of a large array of mirrors that reflect and concentrate sunlight onto a receiver, where the heat is transferred to a fluid.
The fluid then flows through a series of tubes to a heat exchanger, where the heat is transferred to the water. The water is then turned into steam, which drives a turbine that generates electricity.
Solar thermal power systems can use tracking technologies to follow the sun as it moves across the sky. This allows them to keep sunlight focused on the receiver throughout the day.
Solar thermal power systems may also include a thermal energy storage system component. This allows the system to continue generating electricity even when the sun isn't shining.
The thermal energy storage system can store heat from the sun during the day and release it at night or during cloudy days.
Solar thermal power plants can also be hybrid systems that combine solar energy with other fuels (usually natural gas) to supplement solar power production during periods of low sunlight.
Solar thermal systems can be either active or passive. Active solar thermal systems have pumps or fans to circulate the fluid, while passive solar thermal systems rely on convection to circulate the fluid.
Solar thermal energy used for heating water is often called “solar domestic hot water.” This type of system can be used to heat water for homes, businesses, or even swimming pools.
Solar thermal energy can also be used to heat the air in a building. This type of system is called “solar space heating.” This type of system is often used in climates where the winters are cold and there is a lot of sunshine.
Solar thermal energy can also be used to produce ice. This type of system is called “solar cooling.” Solar cooling systems are often used in hot climates to keep food and other perishables cool.
Solar cooling systems can also be used to air-condition buildings. Solar air-conditioning systems use the sun's heat to power a refrigeration system. These systems are often used in commercial buildings to cool the air inside.
Solar cooling systems work by circulating a fluid (usually water) through a solar collector.
The fluid is then circulated through a heat exchanger, where the heat is transferred to the refrigerant. The refrigerant is then used to cool the air inside the building. Solar cooling systems can generate ice when the sun is shining. The ice can then be used to cool the air inside the building when there is no sunlight.
Active solar heating systems employ solar energy to heat a fluid, usually liquid or air, and then transmit the solar heat to the interior area or to a storage system for later use. If the solar system is unable to supply sufficient space heating, an auxiliary or backup system is used.
How do Solar PV and Solar Thermal Systems Compare?
Although solar PV and solar thermal systems both use the sun's energy to generate electricity or heat, there are some key differences between the two technologies.
Here are some of the key differences:
Generated Product
Solar PV systems generate electricity, while solar thermal systems generate heat. However, generated electricity using solar PV systems can be used to produce heat (e.g., by using an electric space heater or water heater).
Similarly, heat generated by solar thermal systems can be used to produce electricity (e.g., by using a steam turbine).
Efficiency & Required Space
Solar thermal systems are more efficient at converting sunlight into electricity than solar PV systems. Solar PV conversion efficiencies range from about 15% to 20%, while solar thermal conversion efficiencies are typically around 90%.
The amount of space that each system can occupy varies. A Solar PV System may require up to 10m2 of roof space, whereas a Solar Thermal System may require only 3m2-4m2. This is because solar thermal systems are more efficient and produce more heat per square foot space than solar PV systems.
It's also worth noting that if you use a solar thermal system to heat water, it will require some interior space. On the other hand, a solar PV system primarily occupies outside space and doesn't take much room inside.
Most PV systems would only require a few cables and a transformer to be installed indoors. While solar thermal systems will require a storage tank, heat exchanger, piping which are typically placed in an attic, garage, or basement.
Complexity
Solar Thermal Systems are more complex since they have more moving parts than Solar PV systems.
They absorb light, generate heat, and use that heat to do something useful like heating water or air. To do so they are equipped with a pump to circulate the fluid through the collector and storage tank. So they have more parts that can break and need maintenance.
Solar PV systems are less complex since they don't have moving parts. They don't need to deal with the fluid flow or heat transfer. They are just made up of solar panels, an inverter, and some wiring. So they are less likely to break down and require maintenance.
Lifespan
Solar thermal technology has a shorter lifespan than solar PV technology. This is due to the fact that solar thermal systems rely on heat-absorbing materials, liquid-carrying pipes, and fans or pumps.
These components can wear down over time and need to be replaced according to the manufacturer's specifications.
Solar PV systems on the other hand use solid-state materials which don't corrode and degrade as quickly. Solar PV systems typically have a lifespan of up to 50 years, compared to solar thermal systems which have a lifespan of around 15-20 years.
Versatility
Solar PV systems are more versatile than solar thermal systems. Because they generate electricity, solar PV systems can be used to power a wide range of devices, including appliances, lights, and even electric vehicles.
Solar thermal systems on the other hand are primarily used for heating applications, especially in residential settings. So in residential settings, solar thermal will not find a lot of use as much as a Solar PV system.
Seasonality
Solar thermal systems are more affected by seasonal changes than solar PV systems. This is due to the fact that solar thermal systems rely on heat-absorbing materials, and the heating process is less efficient in colder weather.
Thus, solar thermal systems perform better in warm climates than cold climates. Conversely, solar PV systems are less affected by seasonal changes and can produce electricity year-round provided there is sunlight.
Uses
Solar PV systems are best suited for generating electricity, while solar thermal systems are best suited for heating water or providing supplemental heat.
When it comes to collecting heat from the sun's rays, solar thermal is up to 70% more efficient than solar PV.
So solar thermal is a great choice if you're looking to heat water or your home. Solar PV, on the other hand, is a better option when you're looking to generate electricity.
Cost
Solar PV systems are typically less expensive than solar thermal systems. This is because solar PV systems are less complex, more commonly used, and have more widely available components.
Solar thermal systems can be more expensive to install and maintain due to their complexity. Although solar thermal systems are more expensive, if the proper use case is applied they can be more cost-effective in the long run.
Maintenance
Solar PV systems require much less maintenance than solar thermal systems. This is because solar PV systems have no moving parts and are less complex. Solar thermal systems, on the other hand, require regular maintenance to ensure proper function.
Solar thermal systems rely on pumps and fans to circulate the fluid, collectors to absorb the heat, and storage tanks to store the heated water or air. All of these components can wear down over time and need to be maintained according to the manufacturer's specifications.
The frequency of these maintenance tasks will depend on the specific system and climate.
Conclusion
Solar PV and solar thermal systems are both great choices for generating renewable energy. Solar PV is less expensive and requires less maintenance, while solar thermal is more efficient at collecting heat from the sun.
Ultimately, the best choice for you will depend on your specific needs and climate. If you're looking to generate electricity, solar PV is the way to go. If you're looking to heat water or your home, solar thermal is the better choice.
Finally, if you're looking for the most cost-effective option, solar thermal is the way to go in the long run. Because of their efficiency, solar thermal systems can produce more energy than solar PV systems for the same amount of investment.
