Last updated on October 11th, 2019
Do you know the difference between solar thermal and photovoltaic? Here, we will have an in-depth look at solar thermal vs. photovoltaic.
Solar Thermal vs. Photovoltaic Solar: What is This Difference?
There are two types of direct solar energy technology, which includes solar thermal and solar photovoltaic. In both technologies, the principle is the same, which involves converting raw energy from the sun into electricity.
But there is also a significant difference between them. This article will focus on solar thermal vs. photovoltaic.
Solar energy is one of the fastest-growing sources of clean energy. More and more people across the globe are now embracing solar panels use to meet their energy needs since it’s renewable and cuts carbon footprint.
Therefore, there is rampant use of solar panels, which involves the absorption of sunlight and converting it into usable energy.
However, these people must decide the technology they want to use between solar photovoltaic and solar thermal. A majority of them barely know the difference between the two types of solar technologies. In some instances, some households end up installing both models in their home.
Well, this is a combination that can work well when one wants to make the most of the efficiency of the solar thermal for their hot water needs and solar photovoltaic for other uses as well as the ability to sell excess electricity back to the grid.
Actually, with the new hybrid panels, people will be able to use both solar PV and solar thermal within the same unit. That will increase the use of hybrid systems in households.
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In this piece, we will give an ultimate overview of solar thermal vs. photovoltaic to help you differentiate between these two types of solar technologies.
Solar Thermal Technology
Firstly let’s try to answer, “What is Solar Thermal Technology?” Solar thermal is a technology that collects sunlight and converts it to heat, stores it, and later transforms it into electricity. In this technology, the panels on rooftops act as the collectors for sunlight and they heat the liquid in the tubes which later goes into a cylinder ready for use.
The fluid that is usually heated by the concentrated sunlight can either be in the form of a liquid or a gas. For example, it can either be water, oil, helium, salts, or air, among others. Various engine types like gas turbines, Stirling engines, steam engines, and more can easily 10’s to 100’s of megawatts of power.
The solar thermal system differs from solar photovoltaic in that the solar thermal power generation works through the concentration of sunlight to produce heat. The heat, in turn, drives a heat engine which turns a generator to make electrical energy.
The energy is suitable for use in industries, commercial and residential sectors. Solar thermal is mainly ideal for water heating purposes.
Solar Thermal System Components
These are some of the components to a thermal solar system.
- Collectors – One of the main elements of a solar thermal system is the collector which is usually set up on a rooftop of a property by making use of frames and brackets. This collector contains a specially coated and reinforced glass pipe that captures the sun’s radiation and then transforms it into heat. The glass pipes are usually embedded in an insulated container, which helps prevent loss of heat energy.
- Heat transfer fluid – In the pipes, there is the heat transfer fluid which comprises of either water, ethylene glycol (eco-friendly antifreeze) or a mixture of the two. The fluid circulates through the hot water tank and the collector.
There are two types of hot water tanks. The first one heats the drinking water and usually consists of a steel tank which is filled with a heat exchanger and the drinking water.
The second one is a combination tank that supplies both hot water and freshwater to the heater. The tank that integrates the duel system has two smaller tanks that are inside that help keep the water for the different tasks separate.
See Related: Using Solar Energy at Home – Pros and Cons
These are some other minor components involved in a solar thermal system.
- A coil heat exchanger – The heat exchanger is placed into a water chamber and includes a ‘twin coil’ cylinder that replaces your existing chamber. Also, it consists of a backup coil usually from the previous boiler to offer extra heating of water when necessary. The two heat exchangers would connect to the collectors and the boiler.
- A pump – A pump moves the heat transporting fluid within the panels and the water chamber (cylinder). Usually, the pump gets its power from the mains electricity, although it can also function through by use of a photovoltaic cell.
- Insulated pipes – These are pipes that are between the water chamber and the panels and usually are known as flow and return pipes.
- System control panel – The system control panel helps control the pump for the heat transfer fluid. Also, it offers data on the performance of the system and on any faults, if any develops.
- Heat flow generation meter – This measures the systems’ output which is necessary if you want to receive payments for Renewable Heat Incentive.
How Solar Thermal Works
The underlying principle of solar thermal heating is harnessing the sunlight and converting it into heat, which is then transmitted into your business or home heating system in the form of space heating or hot water. Heat is generated through solar panels mounted on the rooftop which are used in conjunction with a collector, a boiler, or an immersion heater.
The solar collector uses the rays of the sun to heat a transfer fluid, which is usually a mixture of glycol (antifreeze) and water, which prevents the water from freezing. The water that has been heated from the collector is then pumped into a heat exchanger which is located inside the water tank.
The heat from the exchanger will heat the water that is inside the tank. The water will then flow back to the collectors for reheating after the liquid releases its heat. The controller helps ensure that the fluid circulates to the collector when there is enough heat available.
Pros And Cons of Solar Thermal System
Advantages of Solar Thermal
In the past, solar thermal systems were cheaper than solar PV panels. That changed after the introduction of the Feed-In-Tariffs because of the Domestic Renewable Heat Incentive.
Today, the two technologies are relatively costly, and therefore, that is not a significant determinant. Thus, one of the main reasons to select solar thermal is to save on space. While the solar PV system can take up to 10m2 of roof space, the solar thermal can only occupy 3m2-4m2.
Solar Thermal Has Higher Space-Efficiency Than Solar PV
Solar thermal can have an efficiency level of up to 70% in the collection of heat from the sun, more than a solar PV. The solar thermal is highly efficient and can turn approximately 90% of radiation into heat as opposed to solar PV, which has an efficiency of between 15% and 20%.
However, solar panel technology is making improvements to see this number consistently increase. The technology in solar thermal is not as complex as the one in the solar PV panels.
Solar Thermal Offers Excellent Business Value Compared to Solar Photovoltaic.
Solar thermal comes in handy when you want hot water as it is an ideal solution for water heating and space. Heat storage is an efficient and more convenient method which makes the solar thermal panels more attractive for large-scale production use.
That is because it can store heat within the day and convert it into electricity later at night. The storage capacity of solar thermal helps boost both economics as well as the dispatch-ability of solar power.
Cons of Solar Thermal
- In cold season like winter, solar thermal becomes less effective in exception of thermodynamic panels
- Their lifespan is also shorter than that of solar panels
- Sometimes, it can prove quite difficult to find an ideal supplier
- Solar thermal is not as versatile as solar PVs
- It only works well when offering water heating solutions
Applications For Solar Thermal Systems
The solar thermal system main application is in a commercial set-up but can also be ideal in a residential set-up where the owner wants to reduce energy bills. Mostly, it is more cost-efficient when used in facilities that have high energy demands and high-maintenance heating systems.
Integrating a solar thermal system into an already existing hot water system is relatively simple. A solar thermal system is more efficient and lasts longer, which can be up to 20 years.
Solar Photovoltaic Technology
Let’s first answer, “What are solar photovoltaic panels?” Solar PVs harness the PV technology to capture sun rays and directly convert the sunlight into electrical energy. These panels function best during the day when there is sunlight.
How Solar Photovoltaic Works
Photovoltaic directly converts the light from the sun to produce electricity. This shows that solar panels can only be operational within daylight hours.
A solar PV panel works in a way that allows light particles or photons to heat electrons from atoms which in turn generates a flow of electrical power.
Solar panels consist of smaller units which we also refer to as photovoltaic cells. Every photovoltaic cell is usually a sandwich that comprises of two semi-conductor slices such as silicon.
Types of Solar PV Panels
Solar PV panels are a recent technology than the thermal panels. Solar panels absorb sunlight and convert it into electricity through a silicon-based technology. Here are three types of solar PV panels.
Monocrystalline Solar Modules
The monocrystalline solar cells are built using monocrystalline silicon (mono-Si), also known as single-crystalline silicon (single-crystal-Si). They have an external uniform or even color which usually indicates high-purity silicon.
Silicon is formed into bars and then is cut into wafers to make solar cells for monocrystalline solar panels. The monocrystalline derive their name from the fact that the silicon that makes them is single-crystal silicon.
Since it’s a single crystal that makes the cell, the electrons that usually generate a flow of electricity have a larger room to move.
Therefore, monocrystalline panels are more efficient than their polycrystalline panels.
Polycrystalline Solar Panels
Just like monocrystalline solar panels, polycrystalline also consists of silicon. However, manufacturers melt several fragments of silicon together to form the wafers instead of a single crystal of silicon.
Also called multi-crystalline,” or many-crystal silicon, polycrystalline indicates that there are numerous crystals in each cell and therefore there is less freedom for the electrons to move.
This results in polycrystalline solar panels having lower efficiency ratings than monocrystalline panels.
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TFSCs (Thin-Film Solar Cells)
These are solar cells that are manufactured when one or multiple thin coats of photovoltaic material is deposited onto the substrate. There are various models of these thin-film cells that exist and we can categorize them based on the photovoltaic material put onto the substrate.
These materials may include Organic photovoltaic cells, Cadmium telluride, Amorphous silicon, and Copper indium gallium selenide.
Based on the kind of technology, the thin-film module samples’ efficiencies are around 7–13% and the generation modules operate at an average of 9%.
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Pros And Cons of Solar PV Panels Vs. Photovoltaic
- Solar PV is cheaper than solar thermal because the government offsets the prices with initiatives such as the Feed-In-Tariffs. That makes them a sound long-term investment for households in their bid to lower their carbon footprint.
- Solar PV generates electricity while solar thermal mainly heat water or air. This offers the solar PV owners a chance to sell their excess power back to the grid and can, therefore, generate an additional income.
- The PV panels can offer green energy for users of an extended period, which can go up to 30 years. Most manufacturers provide around 25 years warranty when selling the panels because their durability is incredible.
- With solar panels, you can cover about 60% of the total household’s energy needs
- Solar panels become amazingly efficient during summertime and can’t freeze in the wintertime
- Also, they cover all the requirements of appliances that have a high demand for energy, including freezers, refrigerator, and dryer, and more.
- In most cases, you will require a hefty initial investment to install them
- Also, they occupy a larger installation space unlike solar thermal
- Finding the right supplier can be quite daunting and time-consuming
Conclusion On Solar Thermal vs. Photovoltaic (PV)
The two technologies; solar PVs and solar thermal represent high energy technologies that guarantee you clean and green energy. Nevertheless, deciding the one to opt for, is quite tricky.
While solar thermal is your perfect solution for water heating, Solar PV is the latest technology and has more advantages. I hope this solar thermal vs. photovoltaic has given a broader picture of what to expect.
Which solar technology do you use? Please share your experiences in our comments area.
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