These are devices converting solar energy into heat. Solar collectors save more money spent on traditional heating systems. More and more people install solar collectors on the roofs of houses. It is a result of promoting renewable energy sources and funding for ecological heating solutions.
In summer, the collectors provide full protection for the needs for hot water and heating the house. In winter, they allow you to reduce heating costs. Solar collectors are not the cheapest solutions, but their initial cost is quite fast. In Poland, the collector has no chance to become the main and only source of heat in the home, in hot-water installations, and even more so in heating systems. There are too few sunny days here during the year and it is too often hidden behind the clouds. However, this does not mean that it is not worth considering the assembly of the solar system. Because from March to October well-chosen set is able to provide up to 80-90% of the demand for hot water. In the warmest months, the collectors will provide 100% of the energy used to heat the water. They will heat up hot water even in colder periods. Sometimes two or three hours of sunshine are enough during the day to warm the water in the tank by a few degrees. They may prove irreplaceable in houses heated only by electricity or a solid fuel boiler. The hot water can then be obtained from the collectors, heating it with only an electric heater. It is worth knowing that the higher the consumption of hot water at home, the collectors become a more profitable investment. Before installing solar collectors Before you decide on solar panels, you should check whether they will work well with the heating system. In single-family homes, heat for c.o. and c.w.u. they usually supply gas boilers or solid fuels. This allows solar collectors included in the installation to produce heat in a more ecological, cheaper and also more convenient way.
In a solar energy conversion plant, at least two or three collectors, a storage tank, a solar group, and a controller are needed to heat the water for the average family. In total, you need 10-20 thousand for the investment. PLN, depending on its size and the quality and brand of the elements used.
The most important element of the solar installation is the collector. It is he who captures heat from solar radiation and transmits it so. working factor for hot-water installations The companies offer two basic types of collectors: flat and vacuum pipe.
The flat plate collector is the most popular one. It has slightly lower energy efficiency and loses heat faster than a pipe collector, but its main advantage is a much lower price. Both are mainly used for seasonal hot water heating. between March and October.
The working factor may be water, which allows for additional reduction of installation costs. Due to the deposition of scale in such a water installation, it is not recommended by collector manufacturers. A better and most commonly used working medium is an anti-freeze glycol solution.
The flat collector contains a solar absorber connected to the copper tubes that flow the working medium. It receives heat from the absorber and transfers it to the hot-water system. The absorber is a plate (made of steel, copper, aluminum or plastic) covered with a special thin coating that increases the efficiency of absorbing solar radiation.
From the outside, the collector is protected by a glass of tempered glass, Teflon or transparent plastic. It protects against weather conditions such as rain, hail or snow. First of all, the glass stops the radiation inside the collector creating so-called “greenhouse” effect, which allows to achieve a higher temperature of the heating medium. From the bottom, the collector is protected by a thermal insulation layer that prevents the heat from being released outside.
Vacuum tube collectors are more efficient but also more expensive. They use both direct and diffuse radiation, i.e. one that breaks through a thin layer of clouds. This allows the collectors to work efficiently also on cloudy days.
There are two types of pipe collectors on the Polish market: with direct flow of working medium or with a heat pipe. Vacuum tube collector with direct flow of working medium has a few or a dozen or more glass tubes. In each of them there is a vacuum, which means that the heat losses to the environment are much lower than in flat plate collectors, which means that their efficiency is higher. An absorber and a tube in which the working medium heats up is built into each vacuum tube. Inside the pipes there may be special mirrors that direct the sun’s rays to the absorber. This technology allows for even more efficient use of solar energy. Heat tubes are a more technologically advanced solution. These collectors have the highest efficiency from all available types. They are especially effective in winter and on cloudy days, when diffuse radiation dominates. For one resident, 1-1.5 m² of flat collector area is needed for heating DHW. Therefore, a family of four needs a set of 4-6 m².
Instead of a flat collector it is possible to install a pipe collector, it is enough to use 0.6-0.8 m² of such a collector per person, ie 2.4-3.2 m² for a family of four. In the case of a solar installation cooperating with the c.o. installation it is assumed that the collectors will heat a maximum of 30% of water for c.o.
The heat generated by the collector must be stored somewhere. Therefore, an essential element of the solar installation is the storage tank in which hot water is collected. From there it is taken for home use. The container should have a capacity of several hundred liters, which is sufficient for 1.5-3 days of demand for hot water. A family of four, consuming an average of 200 l of water per day should have a tank with a capacity of 300-600 l.
The collector does not use a direct flow of heated water, but a tank with a built-in coil, which flows hot water from the collector. And the water on the collector-tank road circulates in a closed cycle forced by a circulating pump. Thanks to this, the boiler can work as the main source of heat with a solar collector, which only supports the water heating system.
If the sun’s radiation is too weak, the control system activates additional water heating, eg a boiler for any fuel. This reduces heating costs by reducing fuel consumption, also provides comfort of using hot water, regardless of the number of sunny days. A cheaper solution can be a container with a built-in electric heater that will heat the water if necessary.
The cheapest existing solution is to use the collector in a gravity installation. You do not need to install a circulating pump in it, as the heated water flows up. If the tank is mounted above the collector, additional devices will be unnecessary. This solution is ideal in holiday homes or in simple installations with an electric heater.
Another way is to use a circulating pump, which sends cold water to the collector. This solution is more flexible in terms of the ability to mount the collector and the water tank in relation to each other. Such an installation is used primarily in single-family houses. It should be remembered that water that flows through the collector must meet the requirements for drinking water and must not contain too much iron, which, depositing on the walls of copper pipes in the collector, after some time may block the flow of water through the collector. In this case, you should also remember to drain the water from the collector before the winter. If you plan to use solar energy all year round, the collector circuit must be circulated by an antifreeze agent, which is usually a glycol solution. The heating of domestic hot water takes place through the exchanger, which causes a slight decrease in the efficiency of the system and increases the installation costs.
In order to coordinate the operation of a system consisting of a collector and boiler or an electric heater, we must use automation. In the absence of heat, the second heat source will be turned on from the collector.
The collector works most effectively if it is directed to the south. It may be deflected by 10 ° in the east or west direction, but the greater the deviation, the lower the efficiency of the collector operation. We assemble it in a place unimproved by trees and building. Otherwise it will be inefficient.
The cost of a solar system is not only the collector itself, but also the other elements:
In addition to them, we still need:
a large water tank;
supporting structure for mounting on the roof or on the ground;
collecting vessels of the solar circuit;
collection vessel of the United States;
pipes, lagging, fittings, culverts through covering (eg so-called solar roof tiles),
Additional elements significantly affect the price, for example, for a container with two coils, we will spend at least PLN 1500. Therefore, the low price of the collectors is deceptive. If we need a typical installation, it is best to buy all items sold as a brand set from one manufacturer. Then we do not have to worry about matching the components. Contrary to appearances, even factors such as pump performance have a significant impact on the effective operation of the system.
A good quality set with two flat collectors, a 200 liter container and the necessary accessories can be purchased for approx. PLN 6,000 (VAT 23%). When buying equipment together with the assembly service, we can save a bit, because then we will pay a lower VAT rate of 8%. For this you need to remember about assembly costs. They are valued individually, depending on the level of complexity of the work. Usually, an expenditure of at least PLN 2000-3000 should be expected. We will pay much more for more complex installations, or using vacuum collectors. In systems with a circulating pump, there is still the cost of electricity to supply the pump.
Although the costs are quite high, a reasonably planned and operated solar system can be profitable, reducing the cost of hysteresis by 70% on average. When considering the purchase of the system, all pros and cons should be analyzed, and when deciding to solve a particular company, take into account the availability of the service and the costs of periodic inspections.
Solar collectors are the cheapest way to use hot water. At the same time, they are environmentally friendly and require no maintenance. The trick is to optimize the installation so that with minimum outlays it gives maximum profits and does not cause any problems.
In recent years, the heating demand for heating has dropped considerably, houses have improved insulation, windows, and ventilation with a recuperator. However, the consumption of hot water and energy to heat it remained the same. You can effectively reduce them by choosing collectors. Properly selected solar system allows you to reduce energy consumption for h.a. about half of the year. Therefore, users of liquid gas boilers, heating oil and those using electricity should think about reaching for the heat coming from the sun.
The savings will be greater if we have a solid fuel boiler started in the season, and during the summer we heat up the water with electricity, to avoid embarrassing smoking. Electricity is, after all, at least 4 times more expensive than heat from coal or wood. Contrary to appearances, even by exploiting the boiler throughout the year, we can gain a lot by opting for collectors. This applies first of all to owners of boilers with a feeder.
Outside the heating season, acting only for the needs of DHW, such a boiler works with very low efficiency, more heat absorbs just maintaining the heat than heating the water. Efficiency is therefore at least twice as bad. The actual energy saving is therefore much higher than calculated on the basis of the average annual efficiency of the boiler. Collectors are mainly effective in the warmer half of the year.
Free energy acquisition is one thing, and the reduction in heat generation in the building directly affects the lower emission of pollutants into the atmosphere, improving local air quality. It is also important that solar collectors have the lowest load on the ecological footprint, which means that their production and subsequent utilization are safe for the natural environment. After the minimum 25-year service life, the materials from which the solar collector was made can be recycled. Collectors provide the lowest heat generation costs unattainable for other sources.
In summary, the sun produces clean and inexhaustible energy which is also free, which is important in looking for savings in the home budget. Dynamic changes in construction and the constantly growing requirements and standards of technologies used force us to use alternative solutions. “Renewable energy is the energy of the future”.