Up till now, solar panels are commonly known devices for generating electricity through renewable resources. What if I tell you that there are other ways too? Yes, energy from the sun is converted in 5 different methods including photovoltaic cells. Different methods of solar energy harvesting use thermal energy for different purposes ranging from individual to commercial and industrial levels.
What is Solar Energy Harvesting?
A method to generate electricity from heat and energy from solar power is termed solar energy harvesting. All methods and techniques fundamentally utilize sunlight to generate energy. Solar energy harvesting reduces dependency on fossil fuels to produce electricity, and it is beneficial in the long run. New innovations lead to more efficient solar energy harvesting methods and techniques. Along with methods you will get to know about solar energy harvesting technology used, the impact of solar panel size, along with the pros and cons of these methods.
What Are Different Methods Of Solar Energy Harvesting? What are Solar Energy Harvesting Devices?
Solar energy harvesting is the process of capturing as well as storing solar energy radiated from the sun. After this, this heat and light energy is converted into electrical energy by a suitable method. There are about 5 different methods of solar energy harvesting. Sometimes these methods are also referred to as solar energy harvesting devices.
1. Black Bodies
You are aware that black absorbs most thermal energy and this is another method through which solar energy harvesting is done. Electromagnetic radiation from the sun along with its infrared spectrum is actively absorbed by black color. The energy from the sun is converted to heat energy through this radiation. Black bodies or containers and devices are capable of absorbing and emitting all wavelengths of the electromagnetic radiation spectrum. This method is used for heating up houses and most commonly for water heating purposes on an industrial level.
2. Molten Salt Thermal Energy
This method of solar energy harvesting uses electromagnetic radiation for melting salt. The molten salt is transferred to a heat exchanger to heat water and turn it into steam. This steam is driven through turbines that in turn generate electricity. Insulated tanks enable stable thermal power generation on cloudy days too.
3. Photovoltaic Solar Panels
This is the most widely adopted method that converts energy from sunlight into electricity. Different-sized solar panels are used for this purpose. The amount of energy generated depends on the number of panels and their efficiency. Monocrystalline or polycrystalline structures of panels are commonly used along with inverters and battery banks to provide energy flow after sunset.
4. Solar Water Heater
Thermal solar panels collect solar energy for these heaters. Regions with sunny climates use this method to harvest solar energy. The black heater body is similar to a photovoltaic panel as the black surface absorbs thermal energy efficiently. A pump circulates cold water within the vessel that takes up the absorbed heat, resulting in cooling down the container and warming up water.
Another system does not have a pump instead; it uses buoyancy created by heated water. With this method, cold water sinks, warm water stays on top, and amounts of flow are reduced. This situation is known as Thermosiphon.
5. Vacuum Tube or Evacuated Tubes Solar Water Heater
It is another method of solar energy harvesting which is an enhanced version of the traditional solar water heater. Vacuum tubes ensure the entry of radiant energy in the system along with containing thermal energy. This thermal energy is absorbed by heat pipes and transferred to large water tanks. The minimum amount of thermal energy is escaped because of vacuum tubes and nearly all absorbed radiant energy is converted into thermal energy. After this, let’s learn what is solar energy harvesting technology.
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What is Solar Energy Harvesting Technology?
Three primary technologies for solar energy harvesting are as follows:
1. Concentrating solar power (CSP)
This solar energy harvesting technology uses thermal heat (heat from the sun) to drive electric turbines on a utility scale. Mirrors are used for concentrating sunlight that drives traditional steam engines or turbines and generates electricity. Parabolic trough, dish engine, compact linear Fresnel reflector, and power tower are different methods of applying the principle of concentrating solar power.
a) Parabolic Trough
Uses curved mirrors to focus energy from the sun onto a receiver tube that runs down the center of a trough. A high-temperature heat transfer fluid like synthetic oil is filled inside a receiver tube that absorbs thermal energy and its temperature reaches 750° Fahrenheit or more. This heat is passed through a heat exchanger which in turn heats water to produce steam. Conventional steam turbines get into action as steam passes through them. Individual collector models can be 15–20 feet in height and have a length of about 300–450 feet.
b) Dish Engine
The parabolic dish surface is covered with evenly distributed mirrors that receive thermal energy on a fixed focal point. Working fluid like hydrogen in the receiver is heated up to 1200° Fahrenheit, which in turn drives the engine. Each parabolic dish rotates along two axes and tracks the sun throughout the day.
c) Compact Linear Fresnel Reflector (CLFR)
It also uses trough system curved mirrors through low-cost flat mirrors in long parallel rows. Elevated receivers are the point of concentration of thermal energy that is paired with a tube system through which water flows. With this technology in methods of solar energy harvesting, water is boiled by the concentrated thermal energy, and the steam thus generated is used in power generation along with industrial steam applications.
d) Power Tower
It uses a central receiver system that is highly efficient and capable of working in high operating temperatures. Heliostats (computer-controlled mirrors) are used to track thermal energy throughout the day and focus it on the receiver at the top of a high tower. This thermal energy heats up a transfer liquid to more than 1000° Fahrenheit to produce steam that in turn runs a central power generator.
2. Photovoltaic (PV)
Light is directly converted to electricity with this method. Photons from sunlight strike and ionize the semiconductor material of solar panels, which in turn break atomic bonds of electrons and they vibrate freely. Semiconductor structure forces electrons to move in one direction, thus creating an electric current. However, only a certain percentage of light is absorbed, and the rest is reflected. Other types of photovoltaic technology are building integrated photovoltaic, concentrating photovoltaic arrays, and thin film photovoltaic.
a) Building Integrated Photovoltaic (BIPV): This system generates electricity for on-site use, or it can be exported to the grid. It serves the dual purpose of generating electricity along with being the outer layer of a structure.
b) Concentrating Photovoltaic Arrays: This system is primarily used in desert regions and uses mirrors and lenses for concentrating solar energy on high-efficient cells. Direct sunlight and a tracking system are needed for the smooth functioning of the system.
c) Thin Film Photovoltaic: This method is cheaper than its substitutes and often develops experimental technologies. It is a type of solar cell that is thin and less efficient. They serve the same purpose but at a slower rate.
3. Solar Heating and Cooling System (SHC)
This technology collects thermal energy to heat water and air along with providing cold water and air too. Solar water heating technology, solar photovoltaic with thermal technology, and solar air technology are different methods used in working on this technology.
a) Solar Air Technology
With this technology in methods of solar energy harvesting, the air in commercial and industrial buildings is heated up and serves the purpose of space heating along with agricultural drying. Mostly the system is wall-mounted, allowing maximum absorption of solar radiation during winter, especially.
On a south-facing wall, perforated solar collector panels are installed at several inches to create an air cavity. From the wall, top air is taken and heated between temperatures 30°-100° Fahrenheit on a sunny day. This heated air is ducted to Heating Ventilation and Air Conditioning (HVAC) intake via a connection.
b) Solar Photovoltaic with Thermal Technology (PVT)
Enhanced solar panels module on the roof is used to heat water and generate electricity. For improved electricity production, a photovoltaic thermal collector cools down electrical photovoltaic components and provides thermal energy, at the same time. With the capability of producing power 4 times more than a photovoltaic module, the electrical output is increased by up to 20% and the system size can range from small to industrial scale.
c) Solar Water Heating Technology
A hot water tank, insulated pipes, and solar collector are its main elements that are paired with electronic controls and freeze protection systems for colder regions. Heat collected from thermal energy is transferred to potable water that flows into hot water tanks. For backup, auxiliary heating remains connected to the hot water tank. After this, let’s learn about the impact of solar panel size on energy harvest.
Also See: What are 4 Types of Solar Panel?
What is the Impact of Solar Panel Size on Energy Harvest?
The impact of solar panel size on energy harvest is directly related to their efficiency. Yes, the size of solar panels may increase or decrease their efficiency thus impacting solar energy harvest. Similarly, an unclean solar panel means a reduced surface area that can also influence harvesting. Efficiency-defining parameters are as follows:
1. Area (Density): It measures energy output in watts per square foot. It means large-sized panels with more wattage lead to more energy generation.
2. Cell: The efficiency of the cell is measured similarly through its power. Thus, more cells, more efficiency, and more solar power harvesting.
3. Module: This is the overall efficiency of the solar panels or module. A panel with 15% efficiency means it absorbs only 15% of total solar energy falling on it. Therefore, more efficient solar modules tend to harvest more energy.
What are Advantages and Disadvantages of Solar Energy Harvesting Techniques?
After learning about methods of solar energy harvesting it is better to be aware of their pros and cons. Despite being a clean source of energy generation as its advantage, there are still some drawbacks.
1. Advantages of Solar Energy Harvesting Techniques
- Carbon footprint is reduced with a more environmentally friendly approach.
- Technology is advanced and mature with new innovations for better efficiency.
- Sustainable energy producer
2. Disadvantages of Solar Energy Harvesting Techniques
- Not completely pollution free as greenhouse gases emits during silicon solar panel manufacturing.
- Manufacturers are dependent on other countries for raw materials, resulting in long supply chains.
- Heavy and rigid panels reduce applications. Space and expenses required also act as a drawback.
Well, methods of solar energy harvesting are usually carried out on a large scale, but you can always opt for a small-size version for your house or office. There are options available in the market. Also, solar energy harvesting devices for some methods are easily available and installed for residential usage. However, each of them needs solar panels if installed on a small scale to ensure better energy output.
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