Autonomous energy plays a big role in the modern world now. The trend of using renewable energy sources is growing every day and is used in various fields. Such energy is considered cheap to use, but the installation and maintenance of renewable energy systems are complex and expensive.

Autonomous homes do not depend on networks. Such structures are called the ZNE – zero net energy building type. They are houses with zero energy consumption. The building independently provides itself with electricity from renewable energy sources. This energy is distributed autonomously by a specially installed system throughout the house and provides it with electricity, heating and hot water. The main advantage is that buildings consume fossil fuels, but do not emit carbon monoxide, being environmentally friendly [1].

Non-volatile houses can be: passive, active. The former are fully self-sufficient, but consume a certain amount of energy from the networks. It is efficient, but not completely autonomous. An active building simply functions on its own energy, derived from renewable energy sources. The house produces more of it than it needs to keep a supply. But at the same time, unallocated energy can be sold, thereby generating income from your own home.

Advantages of self-contained houses [2, 3]:

• taking care of the environment;
• the same price for electricity, the owners of such houses can be sure that they are completely independent of electricity prices, which are growing exponentially;
• the cost of home maintenance is reduced. The only expenses will be required for preventive maintenance equipment. This is beneficial for large properties that require a lot of light and heating.;
• there are always some failures and malfunctions in every power system, but for owners of houses with an autonomous power system, this is not scary, because they do not depend on centralized power grids;
• bad weather is not a problem for photovoltaic systems that provide electricity to the house and have a 25-year warranty;
• such a house will be very profitable for sale. There are few offers of non-volatile homes on the market. Due to rising energy tariffs, demand will be high;
• More and more countries are adopting legislation to improve the environmental situation, which means that the law is on the side of nature. Owners of non-volatile homes should not worry about taxes, which will soon appear or are already available in some countries. For example, a carbon tax may force motorists to switch to electric cars, and home owners to upgrade them to reduce harmful emissions and energy consumption.

In Europe, where electricity is an expensive resource, the introduction of energy-efficient technologies is becoming more profitable. One of the most popular home automation systems in non-volatile homes in Europe is KNX.

Of course, standard windmills cannot be installed in a private house. They take up a lot of space, because the diameter of the blades alone is about 20 m. There are special mini wind turbines that can be used to generate wind energy for a private home. Such systems will work effectively both in steppe and coastal, as well as in mountainous areas. The height of such a mast will be 5 meters, the length of the blade will be 1 meter. With the help of one such installation, with a wind of 12-15 meters per second, the installation produces power up to 1 kW. The minimum wind speed for energy generation is 3-4 meters per second [4]. Of course, at this speed, the wind turbine will not produce a nominal amount of energy, but still the installation will work for you. Wind turbine manufacturers calculate electricity generation depending on the average annual wind speed at the location of the system. 4 such wind turbines can provide an average house with energy. It is clear that the wind depends on weather conditions, and this is an uncontrollable thing.

However, ensuring a reliable and uninterrupted supply of electricity to a private home generated only by wind turbines can be problematic, even taking into account the possibility of accumulating excess electricity by wind turbines.

Installation of a set of equipment is very expensive. The cost of a windmill for a private house pays off in 5-20 years. The term is long, but after it expires, the energy will be practically free. Figure 1 shows how energy is generated through a wind turbine.

Figure 1 – Operation of a wind turbine for a private house

Geothermal energy (heat from the earth’s interior) is usually used in places where hot seismic sources are released in the Far East, Kamchatka, etc. Geothermal energy obtained from the heat of the earth’s interior was previously used mainly on an industrial scale, but with the development of technology it becomes possible to use it for heating houses and in the future for generating electricity privately. Heating a house using geothermal sources is very similar to the operation of a conventional air conditioner that works as heating (Figure 2).

Figure 2 – The principle of operation of a geothermal installation for a private house

Two circuits are required for the operation of a heat pump-based heating system. The first one provides normal heating, including pipes and batteries. The second circuit is located underground or in water and uses water as a coolant. It takes the temperature of the medium through which it passes, transmits it to the heat pump and heats the primary coolant, which circulates through the heating system of the house.

This technique will allow you to heat the house in this way in any region. Even a small temperature difference of only a few degrees will allow you to get enough energy to heat an average private house [5].

For a private home, a possible alternative is to install a mini hydroelectric power plant. The compact device does not require the construction of additional structures, such as a dam. At the same time, the possibility of obtaining electricity depends on the presence of a river, canal or conduit at a short distance from the house. The water flow rate should be at least 0.7 meters per second. The operation of the installation is shown in figure 3.

Figure 3 – The principle of operation of a hydroelectric power plant

Mini hydroelectric units for the home, immersed in the flow of a river, conduit or canal, are capable of converting turbine rotation into electricity. They usually have a power of 0.3 to 5 kW, which allows you to fully provide a private house with energy. In addition, storage mini-hydroelectric power plants allow you to store excess energy in batteries that can be used when consumption exceeds production [6].

If we take into account all the details that were described above, namely technologies and approaches, then we can say that a non–volatile house is not a fantastic invention or a fairy tale, but a very real project. For the implementation of which everything is very carefully designed.

The acquired knowledge of Russia’s neighboring countries shows that the «gold of the 21st century» is energy resources. Therefore, humanity is introducing programs for the introduction of renewable energy sources into everyday life.

The main advantage of a non-volatile house is certainly that it can be built wherever you like, and alternative energy will save a lot of money on its operation in the future. What is necessary for an autonomous home:

1. It is required for the consumer to determine whether a site with communications is needed. If not, buying land without communications will be much cheaper.
2. It is also necessary to solve the issue of the dimension of the house. If you have the same budget, you can, for example, instead of 300 m², build a house with an area of 150 m², which will be more technologically advanced and modern.
3. Take into account that even a well-insulated house consumes about 200 kWh / year of energy per m². The bigger the house, the more money will be spent on its operation.

Technology is moving forward, and the construction of a zero house is becoming more and more affordable. The owner of such a house gets the opportunity to save money in the future, enjoy comfort today and remain independent. Gradually, the number of zero houses in the world is increasing, which will eventually lead to a new way of life based on the reasonable use of energy and care for nature.

To make accurate calculations on the feasibility of implementing an autonomous power plant, it is necessary to know the exact parameters of the house project. We will introduce into the calculations the project of a private house located in the Leningrad region, village Red Lake. The house project is shown in figure 4.

Figure 4 – Project plan for a private house in the village Red Lake

The house is located on a hill, as well as next to the well. These conditions are considered the most optimal for the placement of solar installations, because trees and other objects will not create additional shade. The total area of residential premises on two floors of the house is 328 m².

Since the house project initially assumes that an autonomous power plant will be installed during construction, it is necessary to calculate the approximate energy consumption of the house. To do this, we will compile an indicative list of consumers. Being indicative, the given power consumption values accurately reflect their real values, since they are taken from the technical data sheets for the corresponding equipment. The sum of consumers is 31.54 kW, however, the calculation will require taking into account the demand coefficient shown in table 1.

Table 1

 Electricity demand coefficient for private homes

From the above data, it follows that the estimated energy consumption for a private house will be 18.92 kW/h.

The system that is being implemented in the work of a private house is called autonomous, since the production of electric and thermal energy without the use of centralized «traditional» networks. The project uses such sources as: solar energy, wind energy.

The autonomous complex, which includes an energy system powered by renewable energy sources, includes a number of equipment components.

The solar generation system consists of solar modules, a charge controller, a solar inverter and a rechargeable battery. Wind generation contains the windmill itself, a charge controller, a battery pack and an inverter.

Before implementing an autonomous system, it is also necessary to study the market of equipment for its installation. Various countries and manufacturers can act as suppliers, as this area has been developing rapidly over the past decades. Using these characteristics, it is necessary to select potential suppliers. Their selection is made due to the evaluation method based on three criteria: price, delivery time and duration of existence on the market.

Works carried out during the maintenance of equipment for solar and wind farms [7]:

— wind generator: balancing control of the shaft leading to the generator, updating the lubrication of bearings;

— solar panels: annual polishing of the panel surface;

— Charge controller: firmware update, contact group lubrication;

— inverter: ensuring the tightness of the contacts, updating the lubrication of the contact group;

— battery: ensuring the tightness of the contacts, changing the electrolyte.

Maintenance costs account for 5% of total costs, this is due to the fact that these prices are mainly set in the market. Thus, after talking with different manufacturers, it was found that this parameter should be calculated with exactly this rate.

Installation of an energy solar installation includes the following steps:

1. Exploring the area and choosing the optimal location for installing solar panels. Important factors here are the angle of inclination of the panels, the direction of their rotation and the absence of shadows from surrounding objects. Conducting engineering calculations to determine the required power of the solar system and select the appropriate equipment.
2. Installation of support pillars for mounting solar panels and installation of mounting structures on them.
3. Installation of solar panels on mounting structures using special hooks and bolts.
4. Installation of a solar inverter that converts direct current produced by solar panels into alternating current, which is used to power the devices.
5. Connecting solar panels, inverters and other components of the solar system to the electrical network of a house or building.
6. Checking the operation of the system and its configuration, including determining the optimal parameters for the operation of solar panels and other.
7. Installation of a solar installation can be carried out by professional specialists or independently if there is appropriate knowledge in the field of electrics and construction. Installation of a wind power plant usually includes the following steps:
8. Preparation of the installation site. At this stage, the site is being prepared, where the installation of a wind power plant will take place. In particular, soil fertilization, road adaptation and other works are carried out.
9. Installation of the foundation. The foundation for a wind power plant can be either on copra piles or on a monolithic concrete base.
10. Installation of the tower. The tower is installed on the foundation and secured with bolts.
11. Installation of a wind turbine. After installing the tower, a wind generator is mounted on it, which includes blades and a mounted generator.
12. Connection of the power transmission system. Once the generator is installed, it must be connected to the power transmission system in order to generate electricity and optimize the operation of the station.
13. Testing and configuration. After installing and connecting the system, it is necessary to test the operation of the station and adjust its parameters for optimal performance.
14. Starting the station. After all the checks and settings, the wind power plant is ready for operation and can be put into operation.

As for taking risks into account, this is an important factor in the implementation of the project. There are many conditions under which you can lose money from the installation.

Risks to be considered when installing a photovoltaic system [8]:

1. Fire. When installing solar panels, it is necessary to take into account possible fire hazards, especially in cases where untested components and cable products are used.
2. Electric shock. Improper installation or illiterate connection of solar panels can create an electric shock or short circuit.
3. Damage to climatic conditions. Solar panels are prone to damage and damage in strong winds, hail, heavy rains and snowfall.

In a wind farm, the following elements can come out of standing:

— wind turbine blades;

— generator;

— the rotor;

— stator;

— control electronics;

— wind turbine tower;

— mounting and suspension units of the blades.

Breakdowns caused by adverse weather conditions, corrosion of metal elements and other causes are also possible.

Justifying the amount of equipment is an important step in designing or updating any project. It depends on many factors, which include [9]:

1. Performance: the decision on the number of equipment depends on many factors, including performance. Each type of equipment has its own performance, so it is necessary to determine the amount of equipment that will provide the required volume of production.
2. Budget: each piece of equipment costs money. It is necessary to make sure that the budget allows you to buy all the necessary equipment and determine how much can be purchased.
3. Room size: the amount of equipment also depends on the size of the room in which the project will be carried out. It is necessary to determine the optimal amount of equipment based on the optimal use of the room area.
4. Focus: a different amount of equipment is required at each stage of the process. It is necessary to determine the minimum amount of equipment that will allow you to perform the work quickly and efficiently.
5. Materials: the amount of equipment may also depend on the materials used. Some materials may require specialized equipment, so it is necessary to take this factor into account when choosing the required amount of equipment.

In general, justifying the amount of equipment can be a difficult process, but if all factors and established requirements are taken into account, it is possible to do the work efficiently and without unnecessary costs.

The justification for the amount of equipment purchased in this project is that, for example, solar panels according to the project are placed on the roof of the house itself, and the space there is limited. That is why, from the point of view of physical capabilities, it was decided to install solar panels in the amount of 10 pieces. The remaining elements are required in 1 piece, because according to the installation concept and technical parameters, a larger number is not required.

The project budget is not limited at this stage of the project, because calculations are primary. Thus, if the desired result is not obtained, the number of necessary elements will be adjusted by carrying out additional measures to improve work efficiency.

The costs of implementing a project can be very different and depend on the type of project, its scale, duration and other factors. However, in any case, a certain budget will be required for the implementation of the project.

The list of project costs usually includes expenses for various stages of the project, such as:

1. Project planning: here you need to determine not only the goals and objectives of the project, but also the budget, allocation of resources, cost of equipment, etc.Development: Development costs depend on which product of the project will be created. Resources include the costs of design, software code development, content creation, testing, etc.
2. Implementation: in this case, the costs may range from the cost of training employees, purchasing equipment and tools to paying for contractors.
3. Implementation: the costs of this stage of the project include the costs of installation, configuration, testing and further maintenance of the product.

In addition, the total costs of project management should be taken into account, such as the salary of the project manager, office rent, utility bills, etc.

In addition to the direct costs of the project, indirect costs should also be taken into account, such as losses due to delays in deadlines, inefficient use of resources, risks of deterioration in the quality of work, etc. Experts recommend taking into account at least 10% of the indirect costs of the project.

In general, the costs of implementing a project can vary significantly. Therefore, accurate data on each stage of its implementation is needed to correctly assess the budget and determine the scale of the project.

The project for the installation of an autonomous energy system takes into account such cost items as:

— the cost of purchasing equipment and materials;

— shipping costs;

— installation and installation costs;

— additional costs (maintenance, risk accounting).

Maintenance of solar and wind systems is necessary to ensure their efficient operation and prolong their service life. During operation, the panels may be exposed to weather conditions, pollution, mechanical damage, etc. Over time, this can lead to a deterioration in the quality of energy production and even equipment failure.

In addition, regular maintenance helps to prevent possible accidents and protect the equipment from serious damage.