Topic of the day: Solar Thermal energy
Solar thermal energy is now a very familiar topic to me. Not only because I studied it and did my specialization in this topic but also because I can see how the sun is important to provide the essential energy for life on earth.
I have already briefly talked about the power of the sun in a previous topic (see link below), so I am not going to approach the solar power in this way, but now more focused on how the solar thermal energy can be used in our life.
The solar thermal energy is a field in the renewable energies that uses the sun to provide heat (not electricity like the photovoltaic cells). And maybe you are asking yourself for what you need heat. Well, heat is basically needed in everything:
- to heat our homes (when living in cold regions);
- for domestic use to provide hot shower and tap water;
- to cook or bake our food;
- to process and produce materials needed for various fields: chemicals, plastics, wood and paper, pharmaceutical, etc;
- for cleaning purposes in factories such as steam and hot water.
The energy of the sun can be used in all these needs described above, and much more.
In order to be able to harvest the sun’s energy, we need the so-called solar collectors. A solar collector is a device that collects and absorbs the solar energy in the form of heat that can be used in the various applications mentioned before.
Basically, the solar collectors can be divided into non-concentrating and concentrating technologies. The non-concentrating technologies just absorb the solar energy directly in the surface of the collector as shown in the images below and can produce low-temperature heat (generally below 100 ºC) and are suitable for homes and commercial applications.
In the concentrating technologies, a set of mirrors is used to concentrate the solar irradiance into an absorbing point or line, thus generating a much higher temperature at this point; up to 400 ºC in linear systems, or even above this level with the point focus systems. This is possible because the solar energy of a much larger area (the mirrors’ area) is used to heat up a much smaller area (the absorber area), see the examples of the Fresnel collectors below. These technologies are well suitable for the industry that needs the heat directly in the form of steam, hot oil or air.
The solar thermal power plants are another way of using this high-temperature heat: to generate electricity in a thermodynamic cycle similar to conventional power plants. In this case, the heat is generated by the solar energy and not using fossil fuels. This image below is an example of a Solar Tower System that uses thousands of mirrors to focus the sunlight onto the absorber installed in each tower.
The solar thermal energy can also be used to generate cold (yes! using absorbing chillers that uses the heat to regenerate the refrigerant mixture), as well as in desalination systems to produce potable water. This is just a brief of all the potential that the solar energy has. Perhaps in the future, I will write another article about some of these technologies.
The solar irradiation is variable in the different regions of the globe and varies with the seasons and climates of each region (see the map of the global irradiation below).
This can be a problem for places with lower irradiation in which, economically speaking, the solar thermal energy cannot yet compete with conventional sources of heat such as fossil fuels or biomass. Nevertheless, even in places with low irradiation such as the Netherlands, which has an average of 900 hours of sun per year, some solar thermal technologies can be applied. In Brazil, for instance, that has a range of 1400 to more than 2000 hours of sun per year, there are many more situations in which the heat can be supplied by the sun.
A great advantage of solar thermal energy is the possibility of storing this energy in the form of heat (hot water, hot oil tanks, molten salts reservoirs, etc.) Heat is much cheaper to store than electricity, and this can compensate for the fluctuations in the solar irradiation during the day and also provide heat at night.
The market for solar thermal energy is still in its infancy compared to the other technologies available but is a growing trend that will play an important role in many countries in the future for supplying clean energy.
If you are wondering in which form that solar thermal energy can be used in your house or business, ask a specialist and start familiarizing with it. If you don’t have a solar collector for supplying hot water at your home, then you should definitely consider installing one. In tropical and semi-tropical regions that electricity is used for producing hot water, a solar collector can reduce up to 40% of your energy bill.
If you want to know more, take a look at these links:
https://medium.com/@irapua.ribeiro/the-power-of-the-sun-b69e1310b5b6
https://en.wikipedia.org/wiki/Solar_thermal_energy
You are also welcome to ask me questions.
