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Solar Thermal Heating: Renewable and Profitable Energy

Solar Thermal Heating is mainly used for the consumption of domestic hot water and to heat both homes and swimming pool water.

Solar Thermal Heating: Renewable and Profitable Energy

But let’s not fool ourselves, despite having the same functions as normal heating, this is very special, since it takes care of the environment by reducing CO2 emissions, since it uses renewable energy sources for its operation , more specifically, it uses solar energy thermal through thermal solar panels also known as solar panels.

In the long run, this type of equipment causes a great economic optimization because it can be replaced by the classic primitive heating systems: butane, natural gas, propane, etc.

“Thermal solar heating is an efficient heating system that uses thermal energy with the function: to generate hot water for sanitary and swimming pools”

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Illustration of Supertiendasolar of Grupo Oscasolar SL

1. What Renewable Energy does Solar Thermal Heating use for its operation? How does this affect us?
2. Is Thermodynamic Energy the same as Photovoltaic Energy? What advantages does Thermal Energy have?
3. What are the types of Thermodynamic Panels that exist?
4. How many types of thermodynamic panel installation are there?
5. How does Solar Thermal Heating work? How does this efficient system obtain Thermal Energy?
6. What maintenance do solar thermal heating require?
7. What factors determine the efficiency of Solar Thermal Heating?
8. Is it possible to cover 100% of the needs of a home/building with thermal energy?
9. What support system should I use?
10. How many thermal panels would we need to cover a certain home or business?
11. How much can it cost me? When can I get profitable?

Renewable Energies and Solar Thermal Heating

1. What Renewable Energy does Solar Thermal Heating use for its operation? How does this affect us?

The renewable energy source used by solar thermal heating is what its name indicates, thermodynamics or thermal energy (which is not photovoltaic energy , although it is similar in some aspects).

Thermal energy takes advantage of the existing heat in the environment to generate energy. This power source becomes highly recommended due to its high energy efficiency when the ambient temperature ranges between -10º C and 40º C.

This means that there is a high percentage of places where this renewable energy can be generated , so not only large companies can benefit from solar thermal heating , but also single-family homes, collective homes, sports venues, etc.

In addition to thermal energy , there are also other types of clean energy that are used to heat environments, such as geothermal energy used in heat pumps .

two . Is Thermodynamic Energy the same as Photovoltaic Energy? What advantages does Thermal Energy have?

Initially, thermodynamic and solar photovoltaic renewable energy sources are thought to be very similar, however, they are not the same. Photovoltaic energy is obtained from photovoltaic panels , and thermal energy is obtained from thermal panels .

Thermal solar panels and photovoltaic solar panels are different although both have an extremely similar design.

Next, we leave a list of the advantages of thermodynamics compared to photovoltaic solar :

Photovoltaic solar energy can only be obtained when it is daytime and the weather conditions are favourable, however, the thermodynamic plates are self-sufficient and independent, as they obtain renewable energy 24 hours a day, regardless of whether the atmospheric conditions are unfavourable, although it is true that they obtain more energy when there is a better temperature (more heat). The reason for this advantage is due to the fact that solar panels cannot work with the refrigerant gas that we have explained in the second question.

The thermodynamic plates do not have to be installed in a specific direction and orientation unlike the solar ones, since as we have explained before, the thermal energy is acquired whatever the climatological circumstance. This helps us to give more priority to the aesthetics of the building or the house in question, the thermodynamic plates can be placed where it best suits you, without worrying about whether they work or not. However, as we will explain in the next question, it is true that much more thermal energy can be obtained for solar thermal heating if we prioritize other issues than aesthetics.

Thermodynamic panels are easier and more flexible to install, not only because it is optional to direct them towards the sun as solar panels do, but also because they can be placed both vertically and horizontally and on almost any surface without having to reinforce it, this is because the panels are light.

The thermodynamic plates are strong and robust, they can last more than 25 years. This is because they are made from sheet aluminum.

The thermodynamic plates are of low economic cost compared to the solar one, this is due to the fact that their installation and maintenance are simpler, as has been explained.

6º The thermodynamic plates in comparison to their competition have little maintenance. Its main actions are to check that there are no leaks in the circuit and that the gas charge is correct to be at -5º below zero. We have already discussed this in question 3.

thermodynamic-panels-thermal

Remember that thermal panels still cannot produce electricity, for this you would have to use photovoltaic panels.

Thermal Panels for Solar Thermal Heating 

3. What are the types of Thermodynamic Panels that exist?

There are only two classes: thermosyphon systems and forced systems . The choice of one or the other depends on the needs and problems of the user who wants to buy thermodynamic panels .

thermosyphon system

  • They are installed directly on the roof
  • They are less efficient than forced systems
  • They are placed horizontally and as their tank is outdoors, thermal losses increase
  • It is less heavy and easier to install than forced systems
  • It hardly requires maintenance
  • It has fewer components and therefore easier to handle

forced system

  • They are placed in interior rooms helping to maintain the beauty of the environment
  • They are more efficient than the thermosyphon system
  • They are placed vertically favoring the structure of hot water
  • It has more elements than the thermosyphon system and they are more expensive
  • Requires a minimum electrical expenditure for the operation of pumps and control devices

In conclusion: the forced system is better, but they require more time and more cost than the thermosiphon system.

4. How many types of thermodynamic panel installation are there?

We can classify installation into 3 classes depending on the hot water temperature we are looking for:

1. Low temperature installation: heats between 80 ºC
2. Medium temperature installation: heats between 250 ºC
3. High temperature installation: heats between 1,000 ºC

It is thought that since the water can reach a high temperature there is a risk of accidentally burning yourself, but this should not be a problem if the installation is well executed and the recommended maintenance and care of the manufacturer is followed.

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Solar Water Heater 180 liters with Resistance Included from Solis Power

Operation and Maintenance of Solar Thermal Heating 

5. How does Solar Thermal Heating work? How does this efficient system obtain Thermal Energy?

Solar thermal heating obtains thermodynamic energy through plates that must be placed on the outside of buildings. These plates are called solar thermal plates or thermodynamic plates , they have a refrigerant gas (without chlorine) at a very low temperature (generally around -10º).

This coolant runs through the panel and when it collides with the ambient temperature, which is obviously warmer than that of the gas, it causes the temperature difference to guarantee that the fluid evaporates, generating thermal energy.

operation-thermodynamics-heating
  1. The cooling liquid that is around -10º comes out of the solar thermal heating to go to the solar panel.
  2. This is how the cooling liquid appears when it is in the solar panel when it comes into contact with the heat.
  3. The cooling liquid obtains thermal energy due to the difference in temperature with respect to the medium. Being in contact with the heat usually increases its temperature a little more, perfectly from -10º it can go to -5º.
  4. The liquid returns to the heating again, this time with energy. You can only store a certain amount of energy so you can use it later.
  5. Using hot water or heating, we will notice how solar thermal heating does its job.
  6. The gas cools down again and repeats the same cycle.

6. What maintenance do solar thermal heating require?

The maintenance of solar thermal heating is simple, because it is a closed circuit. What mostly needs to be checked is whether there are leaks in the circuit. Another important measure is to verify if the refrigerant gas that flows through the thermodynamic plates is at the recommended low temperature.

Is it possible that the refrigerant gas changes temperature? Not if everything works fine. However, the temperature of the environment is changing and the greater the temperature difference between the refrigerant gas and the environment, the more energy will be obtained. For this reason, in hot climates and in summer, much more thermal energy is obtained . By this same rule of thumb, we could consider setting the temperature of this gas as cold as possible to achieve maximum performance, however, it can only withstand a certain amount of cold otherwise the compressor may be damaged.

Solar Thermal Heating Efficiency 

7. What factors determine the efficiency of Solar Thermal Heating?

  • Environment climate (the hotter it is, the better)
  • Type and quality of heating
  • Type of panels selected
  • Placement of thermal panels

The thermal panels must be directed to the maximum use of the sun, because the sun is what gives the heat. Below we leave a series of measures to optimally place these plates .

1st Place the thermodynamic plates facing south. This measurement is due to the fact that the sun reflects the plate around 12 noon solar time, the time when the sun is more intense. Exactly, the sun brings more heat to the environment and therefore more thermal energy is obtained .

Avoid that the thermodynamic plates are in shaded places due to trees, buildings, etc. Winter is the best time to check if the places where we want to place the plates have shade.

In summer, as a general rule, it will be the time where you can get more energy for solar thermal heating , obviously this is due to the heat. The more heat, the more energy. Why do we feel hotter in summer? Because the sun is further from the earth, making the sun’s rays come directly and there are more hours with light.

The inclination of the thermodynamic plates is also important, what is the inclination that has to be taken into account? Well, depending on when we are going to use more thermal heating:

– In winter the panels are placed adding 18º to the latitude of the place. For example, if Murcia has a latitude of 37 degrees, you should place the panel at 55 degrees.

– In summer the panels are placed subtracting 18º from the latitude of the place. Starting from the previous example, in Murcia they would have to be at 19º.

The radiant surface is what helps the most so that the solar thermal heating has much more energy for its operation. The incorporation of this measure would give rise to another installation opting for thermodynamic plates.

Obviously, the user of solar thermal heating will have to choose between the aesthetics of the building or achieving the maximum possible thermal energy for solar thermal heating .

Remember that the more thermal panels you have, the more energy you can get, so sometimes it is more profitable to put more thermal panels than trying to optimize a few, bothering the aesthetics of the building or house.

thermal-energy-solar-plates
Physical example of a solar thermal heating

8. Is it possible to cover 100% of the needs of a home/building with thermal energy?

Solar thermal heating in homes and in any other type of building cannot provide us with 100% coverage of all the energy that is needed, in the end you will have to resort to another source of support. At most, between 90 – 100% domestic hot water and 30 – 50% heating could be achieved. In general terms, it can be ensured that a maximum of 70% of all the energy that we are going to use would be saved.

It is not recommended to cover 100% of the energy needs in heating, because this would require a very expensive installation at the beginning, in addition to the fact that we would have to have at our disposal a lot of surface to place so many panels, in the long run it does not affect to considerable energy savings. This is because we need to use solar thermal heating more in winter (which is when we get less thermal energy ) and we do not use solar thermal heating as much in summer (which is when we get more thermal energy ).

gas-thermal-energy

Backup power is typically used only in the colder months. In summer it is rare to have to use it.

9. What support system should I use?

There are many people who believe that their support system against thermal energy may be the same as the one they already use, but this is not true. Sometimes you simply have to modify it by adding a solar water heater or some valves that allow automatic operation once it is scarce.
The most used as support are electricity, diesel and the most recommended is natural gas.

10. How many thermal panels would we need to cover a certain home or business?

We warn that this can be very variable, since many variants come into play depending on the person, the business, the home, the location… so for something more precise you can ask us here. However, we leave some approximate data of what we would need.

Factor What you need what you would get
In an area between 150 and 200 m2 ( with underfloor heating With about 6 to 8 sensors                       100% domestic hot water and 15 – 35% heating
For a 3 person dwelling 1 panel (3 to 4 square meters of catchment area)
For a house between 3 to 5 people 2 panels (3 to 4 square meters of catchment area)
For a house between 5 to 7 people 3 panels (3 to 4 square meters of catchment area)
For a house between 7 to 9 people 4 panels (3 to 4 square meters of catchment area)

To find out how to cover 100% of domestic hot water, we can make the following formula, taking into account the liters of water we use.

Collection area (m 2 ) 45 – 55
Panels (4 m 2 ) 11- 13
Accumulated volume (L) 3,000
solar production 450 – 600
solar fraction 60-75

In other words, in this example we could be a hotel that uses 3,000 liters of water per day. Obviously this is an extremely variable hypothesis, the solar production and fraction is very variable depending on the site, the temperature, the environment, etc.

Price of Solar Thermal Heating

11. How much can it cost me? When can I get profitable?

The cost of solar thermal heating depends on many factors. However, as a reference it could be between €600 and €1,000 for each m2 of capture. Using the previous example, for 3,000 liters of hot water it can cost you between €550-750. So we see a reversal in approximately 4 and 5 years.

6º A home that has good thermal insulation will reduce the demand for any type of heating (including heating with thermal energy) and therefore indirectly this helps us save more energy, which translates into

To finish we leave a very illustrative and more explanatory video of how solar thermal energy works .