The Use Of Solar Collectors – Alternative energy sources are becoming widely demanded in the private sector today. At the same time, solar energy, which is available for use all year round, is of greatest interest to owners of country cottages and small country houses.
Against the background of a rapid rise in prices for traditional energy resources (“blue” fuel, electricity, oil products), the use of modern solar systems is quite justified.
Moreover, the payback period of the equipment is no more than 3-5 years. It is advisable to provide for the integration of the collector into an individual DHW and heating system even at the stage of developing a house project – in this case, it will be possible to save significantly.
A solar system for household use is a circuit in which the main structural elements are sequentially located, ensuring the “collection” of solar radiation, accumulation of heat and the subsequent transfer of the received energy to the end consumer.
Solar installations are used as all-season autonomous power systems only in the southern regions of Russia. In the north-eastern regions of the country, solar devices are part of stationary heating equipment.
But even in this case, their use can significantly reduce the cost of house maintenance in the cold season.
- The principle of operation of modern solar systems
- The difference between solar panels and collectors
- Temperature classification
- Solar collector installation diagrams
- Solar collector performance
The principle of operation of modern solar systems
The concept of “solar collectors” combines several design options for home use, but the scheme of work is not fundamentally different.
All collectors, “powered” by the Sun, are equipped with a system of tubes, which, depending on the design of the equipment, can be mounted in the form of a coil or connected in series to the output and input mains.
The tubes themselves circulate a liquid heat carrier for solar systems – water, oil or antifreeze. Absorption and subsequent accumulation of thermal energy from the Sun are carried out by absorbers.
In technical terms, the design is quite simple. The high cost of such installations is due to the use of expensive materials.
For the outer surface of the structure, wear-resistant materials with excellent light transmission characteristics are used – organic glass, polymer compounds and others. But since polymer “synthetics” do not withstand prolonged exposure to UV rays (they have a high coefficient of thermal expansion, which leads to depressurization of the solar system), manufacturers use tempered or organic glass as an alternative.
And the tubes themselves are most often made of borosilicate glass, which is characterized by a minimum coefficient of thermal expansion (8 times less than quartz glass). That is why the material does not crack at sharp temperature fluctuations.
The difference between solar panels and collectors
Before continuing the description of the main characteristics and scope of solar systems for heating water, you need to figure out how solar panels differ from collectors.
1) Solar battery
Solar battery – a device that generates electricity from the energy of the Sun using highly sensitive photocells, combined into a single autonomous system.
Since photovoltaic converters produce direct current, an inverter is additionally used, which makes it possible to obtain alternating current suitable for domestic needs: power supply and lighting.
2) Solar collector
Solar collector is a functional split system, the main task of which is to absorb near infrared radiation and visible sunlight. The batteries generate current and the collectors heat the fluid inside the tubes. This is their main difference.
The heat carrier for solar collectors is selected taking into account the season, as well as the peculiarities of operation. For multifunctional structures, antifreeze (antifreeze liquid) is usually used, and seasonal-type systems are filled with water.
Today you can buy a more versatile option – a hybrid solar collector. This device is attractive in that it simultaneously generates electricity and heats water.
The advantages of using it are obvious: photovoltaic modules are cooled by an active heat removal system, which generates twice as much electricity, and excess heat resources are spent on heating water.
Solar home appliances are often classified according to the type of heat transfer medium. Today, liquid and air systems can be found on the world market.
In addition, the collectors are divided according to the temperature mode of operation, that is, the classification is applied according to the maximum heating temperature of the working elements. The following types of systems are distinguished:
- low-temperature – the coolant for solar collectors heats up to 50 ℃;
- medium temperature – the temperature of the circulating liquid does not exceed 80 ℃;
- high-temperature – the maximum temperature of the heat carrier material can rise up to 300 degrees.
The first two options are most suitable for home use, while models of collectors with high-temperature operation are more often used in the manufacturing and industrial sectors of the economy.
This is due to the fact that in high-temperature water heating systems, the very process of transforming solar energy into heat is quite complicated. Moreover, such solar plants occupy large areas. Not every owner of “country” real estate can afford such a luxury.
Solar collector installation diagrams
In autonomous heating and hot water supply systems, it is imperative to use a storage tank to accumulate thermal energy.
This is due to the fact that the distribution of heat generated by the solar plant is not proportional to the energy consumption.
Therefore, the resources obtained are first accumulated in a special container, and then only consumed as needed.
Experts recommend using a standard storage tank for a hot water supply system for this purpose, or, alternatively, a buffer tank from an autonomous heating system.
A well-built design implies the connection of the collector with an additional heat exchanger, which is in direct contact with the storage tank. There are five field-proven equipment connection schemes.
# 1. DHW with natural circulation of the heating medium
This scheme is used mainly in small areas (for example, for a summer shower), but it is also quite applicable for small buildings – a bathhouse or a country house.
The solar collector must be installed no more than 1 meter below the storage tank level. This will ensure the natural circulation of fluid in the system. It is advisable to use ¾ ”pipes to connect the storage tank to the manifold.
If you plan to use hot water in the evening, you need to insulate the storage tank or buy a ready-made container that functions by analogy with a thermos.
Please note that the insulation layer should not be less than 10 cm. This is the most affordable solar collector connection scheme, but it has one drawback – minimal inertia.
At subzero ambient temperatures, the water will have to be drained in order to prevent depressurization of the water pipes.
#2. Winter installation of a solar collector for hot water supply
In this case, the coolant for solar collectors is antifreeze. This avoids freezing of water in pipes in winter. But here you need to use an indirect heating storage tank with a copper coil. Continuous circulation of liquid takes place directly between the internal lines of the solar system and the coil installed in the storage tank.
This installation scheme is designed for natural circulation, but it is advisable to “drive” the coolant for solar systems forcibly using a circulation pump. Additionally, you need to install an expansion tank.
#3. Collector connection diagram for home heating
This option involves the use of an indirect heating tank that runs on solid or “blue” fuel. In late spring and summer, the boiler can be turned off as the water will be heated by the collector. But in winter, the efficiency of solar systems in the northeastern regions of Russia is not very high, since the intensity of solar radiation is minimal. For this reason, the collector is used as a source of additional heating for heating systems.
But even in this case, the home owner gets the opportunity to use traditional energy resources more efficiently. To ensure heating of the house in winter using only one solar collector, the dimensions of the entire structure must be at least 30–40% of the building area.
#4. Installation of a solar system for heating and hot water supply
A typical connection diagram combines two options at once, that is, it is suitable for organizing autonomous heating and hot water supply at the same time. A double-circuit heat storage tank is used here – in addition to the copper coil, an additional internal tank is also mounted.
This installation scheme makes it possible to separate the technical liquid from the drinking water.
To automate the process of heating the coolant, a special solar collector controller is integrated into the system, which allows you to avoid excessive consumption of energy resources by controlling the temperature of the coolant in the solar system and the temperature of the water in the buffer.
#5. Installing a manifold for pool heating
This scheme is not suitable for a heating system, but is used when it is necessary to heat water in a portable outdoor pool. A standard submersible pump can be used to circulate fluid. If there is a stationary pool on your site, for greater convenience it is better to connect the equipment to a household automated pumping station.
Solar collector performance
One of the main factors affecting the performance level of solar systems is the intensity of solar radiation emitted by the Sun during daylight hours.
In addition to the level of insolation (the amount of useful solar radiation per unit area), secondary factors also affect the performance of the solar collector: the nominal volume of the heat storage tank, the material of the heat exchanger and the area of the absorbers.
When choosing a solar collector for your home, pay attention to the technical characteristics: heat loss coefficients, optical efficiency parameters, as well as the aperture and total area of the solar plant.
Based on these parameters, you can analyze the performance and calculate the maximum allowable power. By using a heat pump and solar collector, high performance can be achieved all year round.