Homemade solar water heaters

What is a solar water heater

A collector (water heater) is a device that collects energy from the sun's rays and turns it into heat. The sun heats up the coolant in the collector, which is then used for hot water supply and heating or electricity generation.

Devices associated with the energy of the sun can be correctly called solar installations or solar collectors (from the name of the ancient Greek sun god Helios).

Modern solar water heaters can be complicated, but any owner of a private house can independently make a device for their own needs. The main thing is to figure out what this device is for.

Three collectors fully satisfy the family's needs for hot water and heating

Scope of use of solar plants

In our country, many people still associate the phrase solar water heater with a black tank on the roof of a summer shower booth, but this technology is successfully used all over the world. Solar collectors are common in the southern regions of Europe. Residents of private homes in Italy, Spain and Greece are legally required to use solar water heaters. China is not lagging behind the West either. There, solar water heaters are installed on the roofs of high-rise buildings and provide hot water to all apartments. In 2000, there were so many solar plants in the world that, put together, they would occupy more than 71 million m2... Almost 15 million m2 of them would be European.

Solar vacuum collectors almost completely occupy the roofs of Chinese new buildings

Such devices are used for hot water supply of domestic premises and industrial buildings, heating of private houses, office buildings, workshops. They are most in demand in the food and textile industries, since it is in this area that there are many production processes using hot water.

In the private sector, each person from Germany accounts for 0.14 m2 of solar collector area, from Austria - 0.45 m2, from Cyprus - 0.8 m2, and from Russia - 0.0002 m2. The intensity of solar illumination in Russia is only 0.5 kWh / m2 less than in the south of Germany. This means that the low popularity of solar collectors in the northern regions is not due to geographical reasons.

With an extensive manifold system, even pool water can be heated

Summer design option

The black plate absorbs heat and transfers it to the coolant moving through the tubes (water or antifreeze). The glass has 2 functions: it allows solar radiation to pass to the heat exchanger and serves as protection from precipitation and wind, which reduce the performance of the heater. All connections are made hermetically so that dust does not get inside and the glass does not lose transparency. Again, the heat of the sun's rays should not be vented by the outside air through the cracks; the efficient operation of the solar collector depends on this.

Getting Started

Before constructing a solar collector, it is necessary to make appropriate calculations and determine how much energy it should generate. But you should not expect high efficiency from a self-made installation. Finding out that it will be enough - you can proceed.

The work can be divided into several main stages:

1. Make a box
2. Make a radiator or heat exchanger
3. Make an advance chamber and drive
4. Assemble the collector

To make a box for a solar collector with your own hands, you should prepare an edged board 25-35 mm thick and 100-130 mm wide. Its bottom should be made of textolite, equipped with ribs.It should also be well insulated with foam (but mineral wool is preferred), covered with a galvanized sheet.

Having prepared the box, it's time to tinker with the heat exchanger. Follow the instructions:

1. You need to prepare 15 thin-walled metal tubes with a length of 160 cm and two inch pipes with a length of 70 cm
2. In both thickened tubes, holes of the diameter of the smaller tubes are drilled into which they will be installed. In this case, you need to ensure that they are coaxial on one side, the maximum step between them is 4.5 cm
3. The next stage - all pipes must be assembled into a single structure and welded securely
4. The heat exchanger is mounted on a galvanized sheet (previously attached to the box) and fixed with steel clamps (metal clamps can be made)
5. It is recommended to paint the bottom of the box in a dark color (for example, black) - it will better absorb solar heat, but in order to reduce heat losses, the external elements are painted white
6. It is necessary to complete the installation of the collector by installing a cover glass near the walls, while not forgetting about reliable sealing of the joints
7. A distance of 10-12 mm is left between the tubes and the glass.

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It remains to build a storage device for the solar collector. Its role can be played by a sealed container, the volume of which varies about 150-400 liters. If you cannot find one such barrel, you can weld several small ones together.

Like the collector, the storage tank is thoroughly insulated against heat loss. It remains to make an advance chamber - a small vessel with a volume of 35-40 liters. It must be equipped with a water-dropping device (articulated faucet).

The most crucial and important stage remains - to put the collector together. You can do it this way:

1. First, you need to install an advance camera and a drive. It is necessary to ensure that the liquid level in the latter is 0.8 m lower than in the front chamber. Since water in such devices can collect a lot, it is necessary to think about how they will reliably overlap
2. The collector is located on the roof of the house. Based on practice, it is recommended to do this on the south side, tilting the unit at an angle of 35-40 degrees to the horizon.
3. But it must be borne in mind that the distance between the storage and the heat exchanger should not exceed 0.5-0.7 m, otherwise the losses will be too significant
4. At the end, the following sequence should turn out: the avancamera must be located above the drive, the last one - above the collector

The most crucial stage comes - it is necessary to connect all the components together and connect the water supply network to the finished system. To do this, you will need to visit a plumbing store and purchase the necessary fittings, adapters, squeegees and other stop valves. High-pressure sections are recommended to be connected with a pipe with a diameter of 0.5 ", low-pressure - 1".

Commissioning is carried out as follows:

1. The unit is filled with water through the bottom drain hole
2. An avancamera is connected and liquid levels are regulated
3. It is necessary to walk along the system and check that there are no leaks
4. Everything is ready for daily use

You can make a solar collector with your own hands quickly enough, this is not a very difficult job. To use it in the country, in the summer, you do not need complex circuits and special equipment:

• If water is needed only outside (outdoor shower, hot water for washing, swimming pool, washing dishes, other household needs), the tank is also installed outside.
• When water is needed in the house, the tank will be installed inside.
• In such a system, there is a natural circulation of liquid, so the tank must be installed 8-10 centimeters above the battery level.
• To connect the tank to the battery (absorber), you need pipes of a certain diameter.
• With a large length of the system, it is better to install a pump that will enhance the movement of the coolant.

Solar collector made of metal-plastic pipes

Types of solar collectors

Engineers have developed flat, tubular with vacuum, concentrators with parabolic cylindrical reflectors, aerial, solar towers and other types of installations. The most popular for domestic purposes are flat and vacuum water heaters.

Table: Comparative characteristics of flat and vacuum collectors

Features of Flat Panel Solar Water Heaters

The device is a panel, inside of which there are copper tubes with a dark coating. They heat up water, which is then collected in a tank and used for hot water supply (hot water supply). If you make the collector yourself, then expensive components can be replaced with available materials:

• instead of copper pipes, you can take steel, polyethylene or just a radiator from an old refrigerator;
• a wooden frame can become a replacement for a metal one, although it weighs more;
• the chrome-plated absorber will replace the usual black paint;
• a sheet of glass or cellular polycarbonate will serve well as a protective cover, and foam plastic will serve as a heater.

The main thing is to ensure the tightness of the panel, but for this it is enough to seal all the seams with construction silicone. The main disadvantage of such devices is that the heated coolant radiates heat into the air and cools a little before entering the storage tank. The use of thermal insulation and sealing of seams is designed to combat precisely this effect.

Expensive parts of an industrial collector can be replaced with cheaper counterparts, for example, steel pipes can be used instead of copper pipes, and the device frame can be made of wood

If water is not taken from the flat collector, on a hot sunny day it can heat up to 190–210 ° C, which can lead to rupture of pipes with a coolant or connecting elements. For those who occasionally use a solar water heater, it is important to install a storage tank that can eliminate excess pressure in the pipes. Another option is to use mineral oil rather than water as a heat sink. Its boiling point is higher, which reduces the risk of damage to the system. In this case, a heat exchanger is needed, in which the oil will transfer the accumulated heat to the water without direct contact.

Flat solar collectors are cheaper and easier to manufacture, but are only suitable for summer use in the country or as an auxiliary water heater. Use them only for DHW.

Features of vacuum collectors

This type of solar water heater consists of individual tubes, each of which is in an airless environment. This design made it possible to reduce heat loss on the way from the collector to the storage tank and increase the efficiency of the system.Thanks to this, vacuum collectors work perfectly during the changing seasons (autumn, spring) and in winter.

The vacuum manifold consists of tubes placed in an airless environment

Copper tubes are also used in vacuum solar water heaters as this material provides good heat transfer and hygiene at the same time. The rest of the elements are similar: glass (borosilicate for better heat transmission), under it is a black absorbing layer, a tube with a heat carrier and a substrate. It is easier to ensure the tightness of the system, since there is only one seam - the connection between the tube and the storage tank.

Separate pipes are connected to the main pipe of the vacuum water heater

Cold water gradually heats up from alternate contact with hot copper pipes. This is the only way to dissipate heat from a vacuum solar plant, so it is important to provide it with a regular flow of cold water, that is, use hot water throughout the day. To increase the durability of the system, antifreeze is used as a coolant in vacuum solar collectors. It tolerates heating up to 300 ° C well and does not freeze when the temperature of the device drops to -40 ° C on a cloudy day.

For year-round hot water supply and heating of a country house, a vacuum solar collector is required. It is more expensive, but more efficient and reliable than a flat one.

It is impossible to create a full-fledged vacuum solar collector with your own hands: making a thick-walled tube from borosilicate glass is unthinkable in artisanal conditions. Therefore, a more reliable option would be to buy factory flasks (coaxial and feather varieties are offered) and assemble the solar water heater on site. But since even such work requires remarkable locksmith skills, it is better to buy a finished product with a guarantee from the manufacturer.