how do solar heating and cooling panels work

Solar energy as a heating alternative

If we want to make the most of the possibilities of domestic solar energy, we can also install solar heating by raising the investment a little. The necessary appliances are the same,  although their size varies , of course. And it is also necessary to install a higher number of solar panels. The operating system is also similar, although the heating coverage is lower than in the case of hot water. When a heating installation is built, it  is dimensioned to cover only slightly less than 50% of the energy demand .

This is done because it is the most profitable formula for the user. Covering 100% of the heating in the colder months would require a much higher investment, which would not compensate  because it is only used for three months of the year . It is therefore necessary to have an auxiliary heating system to cover 100% of the energy demand. The most suitable type of heating emitter for solar energy is underfloor heating; Apart from its other advantages, underfloor heating works only at 40ºC, making it easier to heat. The radiators work at 70-90ºC,  a much higher temperature that means a greater energy consumption. Another type of heating compatible with solar energy is high-efficiency radiators.

How does it work?

The way it works is as follows:  a closed hydraulic circuit containing  a special liquid passes through solar panels called collectors, which are specially prepared to store the sun’s heat. This liquid absorbs the heat and is conducted to the accumulator,  where the The pipe through which it circulates acquires the shape of a serpentine . Inside this accumulator, and in direct contact with the serpentine tube, but without mixing with the liquid inside, is the water that we will later use for taps, showers or heating. When the water has not reached the required temperature, the control system starts the auxiliary equipment and this is in charge of providing the supplementary heat.

Components (edit)

When we want to have a heating system at home based on solar energy, we must take into account that it must have certain components to achieve its operation. A  solar thermal installation is made up of solar collectors , a primary and secondary circuit, heat exchanger, accumulator, expansion vessel and pipes. If the system works by thermosyphon, it will be the difference in density due to temperature change that will move the liquid. If the system is forced, then we will also need pumps and a main control panel.

Types of heating installations that can be combined with solar energy

The production of energy through solar energy to be implemented or used in heating homes, homes or businesses, is constantly evolving and every day  many more users decide by this means , since apart from being a means renewable, it offers many possibilities. Among these possibilities, we must mention that there are many other types of heating installations that can be combined with photovoltaic panels or solar energy. Among the best known and most efficient, we can find the following: underfloor heating, heat pumps and gas boilers. But they can also be used in other types  of heating installations already installed in the home, or used as a support system for them and, in this way, try to reduce the costs that originate from the production of heating for our homes.

What is solar technology?

Solar technology is divided into two groups  depending on the way the sun’s energy is captured , converted and distributed: active and passive. Passive solar energy takes direct advantage of the sun’s heat without the need for mechanisms; while with active solar technology, systems such as thermal collectors or photovoltaic panels are used to transform solar energy into usable energy such as heat and electricity. Let’s go into detail:

• Passive solar technologies

This technology is characterized by being based on the architectural design of houses or buildings, such as the thermal capacity of construction materials and their orientation with respect to it. It is also known as bioclimatic architecture. Passive technology is arguably the  oldest way of harnessing the sun , as in ancient times activities were designed around the local climate. Bioclimatic architecture is based on that same system.

• Active solar technologies

The main characteristic of active technology is that it serves to supply us with energy and the need for special equipment that captures and transforms the sun’s energy into photovoltaic, mechanical or thermal. It is divided into two categories, thermal and photovoltaic systems. Solar thermal energy is obtained by converting the sun’s heat into useful heat, to heat water or for heating; while photovoltaic energy  involves converting solar radiation into electrical energy . To this end, both technologies use individual solar cells that are combined to create solar panel modules.

It must be taken into account  that active solar technologies offer greater power than passive systems , because solar panels optimize the ways of capturing and transporting the sun’s heat. A hybrid solar system using photovoltaic energy and the benefits of bioclimatic architecture would be interesting.

Benefits of solar heating

Solar heating is a system that allows the use of the sun’s rays to convert them into electrical or thermal energy. The sun is a free, inexhaustible and non-polluting source of energy, since it does not produce greenhouse gases. Over the years, the opinions of experts  invite us to seek an efficient, economical and sustainable system  for the energy we consume. The prices of fuels and electricity do not stop rising and this directly affects the pocket of consumers:

Main advantages of solar heating:

• It is an inexhaustible source
• It does not pollute
• Ideal for isolated areas
• They are easy to maintain
• The only investment is the initial installation and can be amortized 5 years after its implementation.

Solar Cool, Operation

The  solar cooling  (or  solar cooling  ) enables the use of air conditioning devices to minimize the need for electricity, although satisfied by the in situ production with photovoltaic panels, and enhance the technological aspect of production and cooling hot water.

The  solar cooling  or  solar cooling  is a system that uses  renewable energy  for cooling environments and its most common use is for systems  air conditioning . With this technology, it is possible to save between 80% and 90% of energy in the conditioning of a building (CIEMAT), resulting in an increase in  Energy Efficiency .

Households consume about 40% in air conditioning, so the technology of solar cooling, can be  a lot of money horrar on the bill without giving up the air conditioning . It is important to add that this system also has the ability to generate hot water or heat spaces, therefore it can be used throughout the year, even with  solar thermal heating systems .

Solar cooling technology

The heat pumps used for  solar cooling  are called “absorption” and take advantage of the natural hygroscopicity of some salts such as lithium bromide, obtained from sea salt, or ammonia and water, to generate a refrigeration cycle continuously regenerated by solar heat.

The beauty of this technology is linked to the fact that the main source of energy required for cooling is heat at temperatures that solar thermal collectors can reach (70-90 ° C), especially vacuum collectors. The electrical energy required for the operation of the system is almost negligible since it is only necessary to supply the auxiliary circuits of the absorption heat pump. The residual heat from the process that must be removed can be used to produce domestic hot water.

Advantage of solar cooling 

The great advantage of  solar cooling  lies in the simultaneous nature of solar radiation and cooling needs. The energy produced is directly exploited because this contemporaneity is both seasonal and daily (especially in structures with large windows). The high summer temperatures registered in Italy and throughout southern Europe contribute to the achievement of high peaks in terms of energy demand by electrical absorption for the operation of air conditioners and are the cause of increasingly frequent blackouts.

If any summer air conditioning system were of the solar cooling type   , there would not even be the problem of the peak of summer consumption, since the energy to cool the rooms would come directly from the solar collectors of each system, whether individual or centralized. Unfortunately, solar cooling technology still has fairly low levels of market penetration and is little to no knowledge of end users, designers, and installers. The cause of this scarce diffusion are some non-technological barriers, mainly related to ignorance of the technology and the scarce number of applications and consequent experience in plant engineering.

Approximately 3 square meters of high-efficiency solar panels are required for each kW of the refrigerator, therefore with vacuum technology. Consequently, in the hypothesis of wanting to cool a house of 180 square meters, with medium insulation, assuming that there are enough 10 kW refrigerators, approximately 30 square meters of collectors are required. Some manufacturers can make absorption heat pumps even with small powers, around 12-15-18 kW.

Absorption machines are refrigeration machines that take advantage of the solubility and high affinity of two substances, one of which acts as a refrigerant and the other as an absorbent, to create a cycle in which the introduction of energy occurs mainly in the form of heat. . There are two commercially established refrigerant / absorbent combinations:

• lithium bromide (LiBr) and water (H  ₂  O), where water acts as a coolant;
• ammonia (NH  ₃  ) and water (H  ₂  O), where the refrigerant is ammonia.

From a thermodynamic point of view, the refrigeration cycle works with three heat sources:

• the cold source is at the lowest temperature and consists of the environment to be cooled;
• the hot well, in which the heat is discharged, is the external environment and is at an intermediate temperature;
• the heat that enters the cycle is introduced through the highest temperature source (boiler flame, hot solar thermal fluid).

The low-pressure part of the machine is made up of the evaporator and the absorber, thermally separated but in communication with each other. The evaporator contains a solution rich in refrigerant, which evaporates removing heat from the cold source (the useful effect if it is a refrigeration system); the evaporated refrigerant is absorbed by the solution rich in absorbent substance present in the absorber, since the refrigerant in solution has a lower surface tension than the pressure in the evaporator: this allows an additional amount of refrigerant to evaporate, without increasing the pressure in the evaporator, which would inhibit the absorption of more gaseous refrigerant. It is necessary to counteract the progressive dilution of the solution by the refrigerant, removing the mixture obtained in the absorber with a pump and treating it appropriately. The function of the pump, in addition to overcoming the pressure drops in the circuit, is to raise the pressure of the fluid to the maximum value of the cycle, sending it to a component called a generator (or desorber). The generator receives heat at the appropriate thermal level to evaporate the refrigerant present in the solution.

Solar Cold Operation

The  solar cold system  works through a paradoxical idea, that of generating cold by taking advantage of heat. This is because its operation is carried out by thermal compression, where the water heats up and evaporates.

There are two types of cooling,  absorption cooling  and  compression cooling . We will focus on explaining  absorption refrigeration  since it is the process that  solar cold technology follows .

The  absorption refrigeration  produced using cold heat absorbing substances to the transformed state liquid to gas. Lithium bromide is usually the most common material used in these circumstances because it absorbs heat very efficiently. Here is his cycle:

1º  The water passes through a low pressure circuit and evaporates due to heat (evaporation process).

2nd  The vapor is absorbed by the lithium bromide (absorption process)

3rd  This causes a concentrated or diluted solution that passes through the generator.

4th  In the generator, the solution separates solvent and solute through an external heat source (thermal energy).

5th  The water goes to the condenser, another exchange where the heat received from the generator is given.

6th  Later, as it is a concentrated solution in water, it passes through the expansion valve and returns to the absorption process, repeating the cycle again.

The  absorption refrigeration  need for a cooling tower water is completely detached from excess heat. In this system, thermal solar panels are used   as  renewable energy  for its operation and the distribution of energy to cool the environment is generally done by ceiling or  underfloor heating systems .

The  absorption refrigeration  is used only with waste heat sources, so it is more economical and environmentally friendly, however, it has a lower yield. The energy used for its operation is  thermal energy .

There is another type of refrigeration operation, called  compression refrigeration system,  which is the conventional and most widely used for air conditioning. It needs electricity, therefore it is not as ecological and economical as  absorption cooling , it also uses a cooling liquid that is dangerous for the environment.

We have reached the end of the article on how do solar heating and cooling panels work, I hope the concepts have been understood.