IMPROVING THE EFFICIENCY OF THERMAL ENERGY USE WHEN HEATING BUILDINGS THROUGH THE INTRODUCTION OF TECHNOLOGIES «SMART HOME»

Purpose. Investigation of the effectiveness of application in the heating systems of administrative, residential, industrial and other buildings of automated thermal management systems for premises using the «smart home» technology Methods. Analysis and synthesis of information, mathematical modeling of the heat supply process of a building, statistical data processing, a computational experiment to assess the effectiveness of the use of «smart home» technologies in heat supply systems. Results. A natural object was selected and investigated for the introduction of energy-saving technologies − a 3-storey fragment of the O.M. Beketov National University of Urban Economy in Kharkiv administrative building with a total heated area of 225,3 m 2 ; investigated: structure, principle of operation, efficiency of the use of an automated control system for thermal conditions of the premises HERZ Smart Comfort. Conclusions. The efficiency of using the HERZ Smart Comfort system was assessed according to the following criteria: the relative and absolute values of the decrease in thermal energy for heating a building a natural object, the reduction in atmospheric emissions of carbon dioxide CO2, and the economic efficiency from saving thermal energy.The heat loss calculation was performed at round-theclock temperature in premises +18 ° C for average monthly outside air temperatures in Kharkov during the heating seasons 1981-2016. It has been established that the use of «smart home» technologies allows reducing the costs for heating a natural object during the heating season by 16.6%, which is 4709 kWh and leads to a reduction in CO2 emissions from the production of heat in the amount of 0.95 tons/year; The economic effect in this case is 6430 UAH.


Introduction
In recent years, a significant number cities of Ukrainian, in particular, Kyiv, Kharkiv, Lviv, Ternopil, Chernivtsi and others, joined the "Covenant of Mayors on Climate and Energy" [1], which provides carrying out measures by the municipal authorities on a significant reduction of greenhouse gas emissions by 30% by 2030. Achieving this result requires a new strategy for the use and development of municipal power system, which envisages increasing the ecological safety of boiler plants and heat-energy centers through the introduction of innovative highly effective energy and environmental technologies [2,3]. It should take into account such problems homeland heat energy as: outdated technology of production and equipment, high energy intensity and material capacity, which exceeds 2-3 times the corresponding indicators of developed countries; the lack of proper environmental protection systems, the lack of proper legal and economic mechanisms which would stimulate development of environ-mentally sound technologies and environmental protection systems, etc. [4,5]. At the same time, stimulation of effective consumption of heat energy by the population will reduce the resource-intensive of urban heat networks, which will reduce the pollution of the environment and emission reductions into the atmosphere of greenhouse gases [6].
The price increase of the energy resources stimulates the development and improvement of energy saving technologies. In Ukraine, there is a significant potential for energy saving due to the reduction of heat loss through the walls, ceiling, windows, and other enclosing structures of residential and public buildings. Unlike residential buildings, where in accordance with the requirements of public health regulations the temperature must be maintained continuously throughout the heating period, in administrative buildings it is possible to reduce the temperature during the absence of staff and visitors. According to the authors of this publication, a temporary decrease in temperature is advisable if premises are not occupied for at least 10-12 hours at a time, which takes place in administrative buildings and classrooms at night, on weekends, and during holidays. In order to avoid the disruption of the desirable humidity levels and thermal movement a temporary decrease in temperature should not exceed 3 °C. The purpose of this work was to develop technical proposals for optimizing the heat supply schedule of the administrative building with further evaluation of the ecological impact.

Object and methods of research
Description of natural object for realization of researches. As an object of research, a section of the administrative building at the Kharkiv National University of Urban Economy has been selected, which houses a lecture hall, laboratory, conference room, and offices of the university administration ( fig. 1). It is a three-story building with two exterior walls and two interior walls adjacent to heated rooms. As a result of a full-scale building survey, the constructive parameters of enclosing structures necessary for carrying out thermal calculations were obtained. According to the indications of meters, the average actual value of specific heat consumption for the entire administrative building in the 2017 heating season was q averag = 97,5 kWh /m 2 . The selected section of the building has two external walls and window openings facing north. The ratio of the window opening area to the exterior wall area is substantially larger than the average value of the entire building. Therefore, it can be assumed that the value of specific heat consump-tion in the selected section of the building will exceed the average value of specific heat consumption for the entire building according to the indications of meters. The average temperature inside the building during the heating season 2017 is t ex = +18 °С.
Method for calculating heat consumption management efficiency natural object. The technique is designed to assess the effectiveness of the use of a remote control system for thermal conditions of an object's premises -HERZ Smart Comfort, which automatically reduces the temperature in rooms that are not currently used, by an average of 3 °C. The restrictions of the temperature schedule were adopted in accordance with the requirements of the current regulatory acts, considering the temperature should remain between 17-23 °C during classes in classrooms and auditoriums. The maximum permissible value of the specific annual energy demand for the University campus buildings was used in order to assess the energy efficiency class of the building, which were used as well as standard values of the heat engineering characteristics of the walls, ceiling, windows, and other enclosing structures [7].
Heat flow (heat loss) Q, W through the enclosing structures (exterior walls, windows, floors, ceilings) is determined in accordance with the expression: F − is the surface area, m 2 ; Δt − the difference between the exterior and interior temperatures, о С; Heat transfer coefficient could be calculated according to the formula: where α in − heat transfer coefficient from indoor air to the wall, W/м 2 · К; d 1 − thickness of the first layer of the building envelope, m; λ 1 − thermal conductivity coefficient of the first layer of the enclosing structure, W/(m·K); d 2 ,…, d n − thickness of the second and subsequent layers of the enclosing structure, m; λ 2 ,…,λ n − thermal conductivity coefficient of the second layer and subsequent layers of the enclosing structure, W/(m·K); α ex − heat transfer coefficient from the wall to the outside air, W/м 2 · К.
Infiltration heat loss is defined as: where c is the average heat capacity of humid air, determined in accordance with [7], kJ / kg о C; m -normative air permeability of enclosing structures of buildings, kg / m 2 hour; Δt − the difference between interior and exterior temperature, о С.
In Kharkov during the heating season of 2017 the average monthly air temperature used in the calculation is shown in table 1. The results of the heat loss calculations with Kharkov average monthly outdoor temperatures during the 2017 heating season and at +18 °C room temperature are listed in table 2.
The calculated average value of specific heat consumption of the section of the building in the heating season of 2017 was obtained q average = 115 kWh/m 2 , which is 17% higher than the average value of specific heat consumption according to meter readings for the entire building.
The comparative analysis of the average monthly air temperatures in Kharkov in the heating season of 2017 showed that it is not representative of the average temperatures of the heating season taken over a long-term period [9], presented in table 3.
For example, the average outdoor temperature in December 2017 differed from the average air temperature in December for a thirty-five year period by more than 5 °C.
The heat loss calculation was performed at round-the-clock temperature in premises +18 ° C for average monthly outside air temperatures in Kharkov during the heating seasons 1981-2016. Its results are presented in table 4.  November +0, 9 7 December − 3,5 The need for heat supply of the premises was established as a result of the research: -the ground floor is used on average 30 hours per week: 6 days for 5 hours; -the second floor is used on average 2 hours a week: 2 days for 1 hour; -the third floor is used on average 45 hours per week: 5 days for 9 hours.
It is proposed to apply The remote temperature control system that uses elements from HERZ Smart Comfort system, which will ensure the automatic temperature reduction in unoccupied premises by an average of 3 °C.
System of remote-control by the thermal mode of apartments with the use of technology «clever house» -HERZ Smart Comfort. HERZ Smart Comfort is a set of components for controlling heating on a smartphone. The kit includes ( fig. 2): electronic thermal heads ETKF +; window open sensor; room wall thermostat; switching module Cube +; -Eco SWITCH + wall heating switch. All radiators in the house are equipped with electronic thermal heads ETKF +. In each room, a room programmable thermostat is installed, which measures the temperature in the room and gives commands to the thermal heads for opening and closing. It is possible to control directly the electronic thermal head according to the air temperature in the room, however, the savings are reduced, since the thermal head is installed directly on the radiator, its operation can be affected by curtains, direct sunlight. The room thermostat can be installed at an optimum height where external factors will not affect it. Each window must have a window opening sensor installed. To control thermostats via a smartphone, the system must be equipped with a Cube + module, which is located next to the router and provides connection to the Internet. The Eco SWITCH + heating switch is purchased one for the whole house, installed in the hallway and turned on when the last tenant leaves the house. The whole system HERZ Smart Comfort works as follows. The room thermostat measures the temperature in the room and through the thermal head changes the amount of heat-transfer fluid passed through the radiator. When you open the window, the sensor is triggered and the room temperature is automatically maintained at 17 °C (factory setting) or other user defined. With the help of a wall-mounted room thermostat, depending on the mode of homeowners, an hourly temperature change is configured. For example, in the afternoon from 8-00 to 17-00, when no one is home, you can set the temperature to 16 °C, and to return from 17-00 22 °C. A total of 6 hours periods can be set for a day with different temperatures. When changing the set schedule, the owner of the house through the smartphone with the pre-installed application can change.
Benefits HERZ Smart Comfort. The main factor that ensures the efficiency of the heating system and lower gas costs is flexibility in management. The temperature in the room should be exactly what is needed at the current moment and not a degree more. This functionality and provides HERZ Smart Comfort.
HERZ Smart Comfort features: control and temperature control in each room; heating control from a smartphone, laptop via the Internet; automatic temperature change in the room by periods (6 periods per day); the ability to remotely set the room temperature when changing the schedule; minimization of heat loss when airing rooms.
When managing heating from a smartphone via the HERZ Smart Comfort system, according to the manufacturer, it is possible to save up to 60% of energy resources.

Results and discussion
The results of the heat loss calculations while using the remote temperature control system are presented in table 5. In the calculations of thermal losses the average monthly temperatures of air are stopped up in Kharkiv in a heating season, got for thirtyfive-year period 1981-2016.
As follows from the comparison of the calculation results, the use of the remote temperature control system provides 4 700 kWh of heat savings for the heating season, reducing the cost of heating the building by 16.6%. As a result of switching to the optimal heat supply schedule the ecological efficiency was estimated by determining the potential fuel economy required to obtain the saved thermal energy (taking into account the averaged losses inevitable at each stage of the technological chain during energy transmission) and the corresponding environmental impact due to the fuel extraction, transportation, and combustion.
It is necessary to review the various ways of fuel production, transportation, combustion, transmission, and use of thermal energy in order to perform the precise assessment of the environmental impact. The major point for assessing the environmental performance is the reduction of greenhouse gas emissions, primarily СО 2 [9], as a result of burning natural gas. Given that in Ukraine there is no established national carbon emission factors for natural gas combustion, the potential reduction in СО 2 emissions was estimated based on recommendations of the International Expert Group.
trative building with a total heated area of 225.3 m 2 ; investigated: structure, principle of operation, efficiency of the use of an automated control system for thermal conditions of the premises -HERZ Smart Comfort.
2. The efficiency of using the HERZ Smart Comfort system was assessed according to the following criteria: the relative and absolute values of the decrease in thermal energy for heating a building − a natural object, the reduction in atmospheric emissions of carbon dioxide − CO2, and the economic efficiency from saving thermal energy.The heat loss cal-culation was performed at round-the-clock temperature in premises +18 °C for average monthly outside air temperatures in Kharkov during the heating seasons 1981−2016. It has been established that the use of "smart home" technologies allows reducing the costs for heating a natural object during the heating season by 16.6%, which is 4709 kWh and leads to a reduction in CO 2 emissions from the production of heat in the amount of 0.95 tons/year; The economic effect in this case is 6430 UAH.