On the Use of Residential Thermal Stations in Different Types of Buildings ^†

Abstract

The main purpose of this paper is to analyze the energy consumption and the efficiency of heating systems in two multi-family buildings and one collective residence equipped with residential thermal stations (RTSs) that are used for supplying individual dwellings with heat as well as hot and cold water. An additional aspect of the analysis is a presentation of the structure of total energy consumption for particular purposes in the analyzed buildings.

1. Introduction

A very important aspect that has a significant effect on energy consumption in buildings and the energy efficiency of the entire heating system is the type of this system [1,2]. The main purpose of this paper is to analyze the energy consumption and the efficiency of heating systems in two multi-family buildings and one collective residence equipped with residential thermal stations (RTSs) that are used for supplying individual dwellings with heat as well as hot and cold water. An additional aspect of the analysis is a presentation of the structure of total energy consumption for particular purposes in the analyzed buildings.

2. Materials and Methods

The subjects of the research were three buildings [one collective residence (B1) and two multi-family dwellings (B2 and B3)] located in the Lublin voivodship in Poland in the period of 31 December 2014 to 31 May 2016 for B1 and B3 buildings and in the period of 5 January 2015 to 25 May 2015 for B2 building. The following data were measured in the analyzed buildings every month: electricity consumption for individual apartments, gas consumption for cooking purposes for individual apartments, heat consumption for all apartments read from heat meters located in all RTSs, and heat consumption for the entire building read from the main heat meter.

Additionally, in the B3 building, where the heating system with RTSs was supported by solar collectors, more detailed analysis was made in order to determine the amount of heat supplied to the system by the district heating network (Q_DH) and the solar collectors (Q_solar) in 10 minute periods using the following equations:

$${\mathrm{Q}}_{\mathrm{D}\mathrm{H}}=\frac{{\dot{\mathrm{m}}}_{\mathrm{L}1}·{\mathrm{c}}_{\mathrm{p}}\left(\frac{\mathrm{T}3+\mathrm{T}2}{2}\right)·\left(\mathrm{T}2-\mathrm{T}3\right)·600}{1000000000}\left[\mathrm{G}\mathrm{J}\right]$$

(1)

where:

${\dot{\mathrm{m}}}_{\mathrm{L}1}$ – mass flow of heating medium returning from RTSs, $\frac{\mathrm{k}\mathrm{g}}{\mathrm{s}}$,

$\mathrm{T}3$ – medium temperature on the return from the RTSs after the three-way valve, ºC,

$\mathrm{T}2$ – temperature of the heating medium on the RTSs supply, ºC,

${\mathrm{c}}_{\mathrm{p}}\left(\frac{\mathrm{T}3+\mathrm{T}2}{2}\right)$ – specific heat for mean temperature from sensors T3 and T2, $\frac{\mathrm{J}}{\mathrm{k}\mathrm{g}\bullet \mathrm{K}}$,

$600$ – number of seconds between the recorder’s recordings.

$${\mathrm{Q}}_{\mathrm{s}\mathrm{o}\mathrm{l}\mathrm{a}\mathrm{r}}=\frac{{\dot{\mathrm{m}}}_{\mathrm{L}1}·{\mathrm{c}}_{\mathrm{p}}\left(\frac{\mathrm{T}3+\mathrm{T}1}{2}\right)·\left(\mathrm{T}3-\mathrm{T}1\right)·600}{1000000000}\left[\mathrm{G}\mathrm{J}\right]$$

(2)

where:

$\mathrm{T}1$ – temperature of the heating medium on the return from the RTSs before the three-way valve, ºC,

${\mathrm{c}}_{\mathrm{p}}\left(\frac{\mathrm{T}3+\mathrm{T}1}{2}\right)$ – specific heat for mean temperature from sensors T3 and T1, $\frac{\mathrm{J}}{\mathrm{k}\mathrm{g}·\mathrm{K}}$.

3. Results and Discussion

The research allowed for the analysis of energy consumption and assessment of systems by determining their energy efficiency in individual measurement periods divided into summer and winter periods. The amount of heat delivered, lost, and used in particular months of the measurement period is presented.

It was found that in the summer, the B2 system was the most energy efficient, using 67.2% of the heat supplied, while the system that was least energy efficient was the B3 system, in which 50.6% of heat was used. In the heating season, the B1 system was the most energy efficient, in which up to 82.5% of the heat supplied was used, while the B2 system was the least energy efficient with 71.2% of heat used. In the period from 11 May 2016 to 29 June 2016 in the B3 building, thanks to solar installation supporting hot water preparation, 18.2% of heat was saved, and total consumption was 66.6 GJ, of which 10.24 GJ constituted heat from the solar circuit.