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Abstract

Content

Introduction

Energy-saving – a complex of measures aimed at the economical use of energy resources. In the power engineering sector under the energy-saving, as a rule, realize lower power consumption and the use of alternative energy sources. The other side is the rational use of energy-efficiency, that is, using less energy to provide the same level of energy supply of buildings and manufacturing processes across the enterprise. Now these concepts are complementary and are one.

In recent years energy prices increased significantly, because more often raised the issue of reducing energy dependence. In Ukraine, the majority of governmental institution in the past raised the issue of energy-saving is not often. But in a difficult economic situation of the preparation program of rational use of energy, particularly electricity, in educational institutions is a priority.

In the Donetsk National Technical University had hardly addressed the issue of power optimization of multi-storey school buildings. This question is multifaceted and needs a comprehensive review. Optimization of the system of electric lighting of buildings and manufacturing equipment can bring big conservation. The main features to reduce energy bills are as follows:

The purpose of master's thesis is an analysis of methods for saving energy and increasing energy independence of the eighth academic building of Donetsk National Technical University.

1. Energy-saving due to lighting

The easiest method of saving energy at home – improving lighting facilities, first of all – the use of efficient lighting [1].

Today, the market can meet the following types of bulbs:

Incandescent lamps (IL) for many decades, produced a passport-life 1000 hours. In the catalogs of leading manufacturers are present in IL Longlife double life.

Yet how many have worked for FN in our real world? Tests have shown the major brands of variation from 700 to 1300 hours [2]. Formally, this is just a few months of operation (typically 6–10). Experience shows that the IL may well serve for 2–3 years, yielding little in the fluorescent lamps (FL). There are two reasons:


The dependence of the parameters of the IL voltage

Figure 1 – The dependence of the parameters of the IL voltage

But another side of life improvement is the reduction of efficiency. In addition, the dimmer – not the stabilizer, and in severe cases (frequent surges, such as disabling a powerful load) IL will continue to burn out more often than would be desirable [3].

Currently, there are two main types of energy-saving bulbs: compact fluorescent (CFL) and LED.

Consider the CFL. In luminous efficiency (~ 75 lm/W) CFL approach to conventional incandescent. At the same time, 10 W CFL provides the same light as ordinary incandescent power of 50 W. In addition, modern compact fluorescent lamps are used in the 6–8 times longer and can be easily integrated into existing lighting fixtures, which formerly used incandescent bulbs.

The disadvantages of fluorescent lamps are slowly warming up, a strange light, and sensitivity to changes and reduce stress.

Damaging the lamp are frequent inclusion – this not only wears out ballast (electronic ballasts), but the cathode in the discharge bulb. It is believed that each switch takes at least an hour of the resource. This shortage is deprived of CFL are equipped with soft-start function.

In addition, the composition of these bulbs contain highly toxic mercury. In this connection, damaged and burnt CFL are dangerous to health and the environment and must be disposed of properly.

LED lamps, including LEDs, are now among the most promising types of lamps. Compared with other types of bulbs, they are more reliable and efficient than incandescent and fluorescent lamps. LED lights are stable in all climatic conditions and resistant to thermal stress. In addition, they are very durable and do not contain mercury.

LED lights allow you to adjust the lighting voltage reduction (traditional lamps HID lamps do not permit, at lower voltages are turned off).

The main advantage of LED lamps over other types of lamps is a low power consumption and very long service life (20–50 thousand hours). Bulb 40 W LED bulb corresponds to the power of 5 W and an incandescent bulb with 75 W – LED power 10 W [2].

Summing up, we see that there are great opportunities for energy-saving through lighting. In addition to replacing outdated incandescent light bulbs with modern compact fluorescent or LED, is a promising plant motion sensors to turn on/turn off lighting in hallways and exterior lighting buildings.

2. Use of automated electric power accounting

Since the academic buildings equipment, consume reactive power, has very little time of inclusion (coefficient of inclusion), may be appropriate installation of meters, which separately account for the active and reactive energy. This will help reduce the cost of electricity costs and avoid additional capital to the compensating device.

The main disadvantages of the traditional system of energy accounting are:

  1. Fixing only the outcome of the measurement results for the billing period.
  2. Accounting only for the interface with the energy supplier and, therefore, the inability to estimate the distribution of energy within the company.
  3. Low accuracy and reliability of the (older means and methods of accounting error when copying the testimony, non-simultaneous removal of information from multiple, geographically distributed instruments, taking into account one type of energy source), low information content and a large labor input by the manual data collection and processing [4].

Accounting for electric power can be divided into commercial and technical. In custody are used more accurate counts, and rates are transmitted to the utility companies. With the technical accounting data from the meters are used only within the institution that allows the use of counters from the lower class of accuracy [5].

In addition to the simplicity and accuracy of automated electric power accounting allow you to store collected evidence in the databases. This opens up the possibility for long-term monitoring of the process energy consumption and data analysis for better implementation of energy saving technologies in order to optimize the electrical networks of multi-storey school buildings.

The feasibility of using smart meters for commercial and technical accounting of electric power is solved on the basis of technical and economic calculation.

3. Compensation of reactive power

3.1 The main provisions


All processes in the electrical systems can characterize of three parameters: the voltage U, current I and the active power P. However, for ease of calculation and accounting of use, and other options, including reactive power Q. Reactive cardinality is the creation of magnetic and electric fields. Inductive load is regarded as a consumer of reactive power, and the capacitance – as its generator.

To characterize the capacity of the AC circuit requires an additional indicator of the phase shift of voltage and current – angle φ (fig. 2, а).


Changing current and voltage in AC circuits (a) and delta power (b)

Figure 2 – Changing current and voltage in AC circuits (a) and delta power (b)

The reactive power consumed by the three-phase power transformer is consumed, as well as in AM, the magnetization of the magnetic circuit of the transformer (QТ.0) and the establishment of field scattering (QТ.Р).


Amination: 21frame, 8 reps

Figure 3 – Equivalent circuit of power supply system and the change in the angle φ and the voltage at nodes A, B, C, D, E

The consumption of reactive power to the transformer magnetization is several times lower than AM, lack of air gap in the transformer. But due to the fact that the numbers of transformations in the system power supply voltage attains 3–4 and has a tendency to rise to 5–6, total rated capacity of transformers for many times greater than that of AM. The costs of reactive power in the AM and transformers in this system are comparable.

Of the total consumption of reactive power transformers, about 80% is spent on the magnetization [6].

The transfer of a significant reactive power supply in the system leads to additional loss of voltage, active power and reactive power load lines.

It follows that it is technically and economically feasible to provide additional measures to reduce transmission of reactive power, which can again be divided into two groups:

An example of CD can be capacitor bank, connected parallel to the active-inductive load, such as an asynchronous motor. The principle of the CD is illustrated in fig. 4. Connect a capacitor C reduces the phase angle between current and voltage, respectively, increases the load and power factor loads. Consumption of the network current is reduced I1, to I2.

Equivalent circuit of the line receiver circuit power capacitor connected in parallel (a) and the vector diagram (b)

Figure 4 – Equivalent circuit of the line receiver circuit power capacitor connected in parallel (a) and the vector diagram (b)

The main disadvantage of capacitive CD is that at low voltage, they reduce the issue of reactive power is proportional to the square of the voltage reduction, while the need of improvement. Power control CD is only steps rather than smoothly and requires of installation expensive switching equipment.

Synchronous machines can generate and consume reactive power, that’s have on the electricity network effects, identical effects of capacitive and inductive loads. When overexcited synchronous machine generates reactive component of the stator current, whose value increases with increasing excitation current. Overexcited synchronous machine generates advanced current, similar to the condenser.

Synchronous compensator (SC) is a synchronous electric machine operating in the motor with no load on the shaft. They are specifically designed to produce reactive power. Unit cost generate power UAH./kvar, and specific losses, kW/Mvar for SC significantly higher than for SM, as the unit cost and loss account for the entire reactive power. When the great deficit of reactive power at the connection point for consumers that require a smooth and high-speed acting device voltage regulation input of is SC advantageous. With the availability high-variable reactive load application zone extends SC equation.

The disadvantages of SC include:

3.2 Reactive power compensation in multi-storey buildings


In multi-storey buildings of educational institutions have the equipment that consumes reactive power. Such equipment may include engine labs and elevators, other laboratory equipment. In the network there are power surges, the phase shift of current and voltage, reactive power flows. All this leads to an increase in energy costs, as well as to the deterioration of power quality, which negatively displayed on the work of other equipment.

According to the [5] takes into account active and reactive energy, which is obtained from the consumer utility company.

Necessary to identify the sources of reactive power and to solve the above-mentioned problems, or unregulated use of step-controlled capacitor banks (CB).

In multi-storey buildings, which have a very extensive power grid, the key question is the optimal place of installation of compensating devices.

Straightforward solution would be installing additional capacitors at each power-consuming equipment, which consumes reactive power. However, this scheme in practice it is difficult to use because it requires a lot of different power capacitors, and this - great investment.

Another solution is to install the CB on the tires of 0,4 kV TS, that supply education building. Installing CB in urban TS and their exploitation is not a significant hardship, but may have less economic impact and does not solve the problem of the availability of reactive power flow in a complex electrical network of multi-storey buildings.

The most advantageous from the viewpoint of a mixed scheme, when the reactive power is compensated by the most powerful receivers with individual compensators, and the balance of reactive power – with the help of automatic capacitor banks connected to the input of the shell or on the buses in the power of TS [6].

The choice of compensation schemes affect diagram of the electrical network of the building.

When the radial pattern is convenient to use the general scheme of reactive power compensation. With a relatively small length of line and load balancing, setting tires on the CB TS will offload 0,4 kV mains supply and transformers.

When the trunk power supply circuit can be used individually or mixed compensation scheme, which will reduce the current in the main cable (conductors)[8].

Feasibility of installation of compensating devices, as well as their connection scheme is solved on the basis of technical and economic calculation.

4. The use of alternative energy sources

The main and most common to date with alternative sources of energy are wind and solar.

Wind turbine – a device designed to convert the kinetic energy of wind into electrical energy. Requirement for stable operation of wind turbine is a high wind.

The drawback is the discreteness of energy flows – frequency variability of income and energy potential. The instability of the wind flow leads to a reduction in the amount of electricity generated, and to reduce the service life due to wear of the brake system. Modern technologies and equipment, as well as methods of rational use of wind farms virtually eliminated the obstacles with respect to their widespread introduction [9].

Solar panel – some combined photovoltaic (PV) – semiconductor devices directly convert solar energy into direct current.

The current in the solar cell will vary in proportion to the number of photons captured by the surface of the photocell. This figure, in turn, will depend on a number of additional factors - is the intensity of light radiation, the area occupied by the solar cell, the time of operation, efficiency of the device, which depends on the temperature (if it is increasing the conductivity decreases significantly photocell) [10].

Power of solar radiation flux at a distance of 150 million miles from the sun, without loss in Earth's atmosphere is about 1350 W (in the southern regions of Ukraine) and 1300 W (eastern) per square meter. At the same time, the specific power of solar radiation in a very cloudy day, even during the day may be less than 100 W/m2. With the help of the most common solar cell can convert this energy into electricity with an efficiency of 9–24 %. The price of batteries will be about 8–24 UAH. Tues of rated power. In the industrial generation of electricity using solar cells price per kWh is 2 UAH.

It is known that in some laboratories obtained solar cells with an efficiency of 43 %. In 2012, the expected entry into the market of solar cells with an efficiency of 39 % [11].

Alternative energy sources are not capable of producing super-large capacity (taking up little space for their work), they can not operate continuously to maintain the necessary and constant values (stabilization) of the main parameters: current and voltage – it is necessary to use additional devices (regulators, batteries). But as an additional source of electrical energy into multi-storey education buildings, they are fully fit.

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