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Nowadays, the supply of energy from renewable energy sources is important in the energy sector of every country, so it is necessary to pay attention to alternative sources with thermal potential. The aim of this article is to perform an analysis of the possibilities of using heat from the wastewater treated at the Vilnius wastewater treatment plant. The work determines the temperature and flow fluctuations of the wastewater treated in the treatment plant, the theoretical heat potential. The heat demand of a commercial building is calculated. Based on these data, the parameters of a heat pump using treated wastewater are determined and a system model is created in a energy simulation software and the heat supply of the building is estimated. [ABSTRACT FROM AUTHOR]

The installation of heat pumps in district heating (DH) systems is one of the most promising technologies to increase the efficiency of heat supply by using renewable energy sources and reducing heat carrier temperatures in the networks. The possibilities of installing heat pumps in DH systems are very wide, but most often the main purpose of their application is to increase the temperature of the supplied heat carrier at the heat substations of individual consumers or their groups. This paper describes a study that analyzed the possibilities of integrating an individual heat pump at a heat substation in a building to reduce the temperature of the heat carrier in the return line. The results of the study revealed the dependences of the reduction of the heat demand of the building from the DH network, the power of the heat pump, the coefficient of performance (COP), and the reduction of the return temperature. Article in Lithuanian. Šilumos siurblio integravimo centralizuoto šilumos tiekimo sistemoje atvejo analizė Santrauka Šilumos siurblių diegimas centralizuoto šilumos tiekimo (CŠT) sistemose yra viena perspektyviausių technologijų, padedančių padidinti šilumos tiekimo efektyvumą, panaudojant atsinaujinančius energijos išteklius ir mažinant šilumnešio temperatūras tinkluose. Šilumos siurblių įrengimo CŠT sistemose galimybės yra labai plačios, tačiau dažniausiai pagrindinis jų taikymo tikslas susijęs su tiekiamo šilumnešio temperatūros didinimu atskirų vartotojų ar jų grupių šilumos punktuose. Šiame straipsnyje aprašomas tyrimas, kurio metu buvo analizuojamos individualaus šilumos siurblio integravimo pastato šilumos punkte galimybės, siekiant sumažinti šilumnešio temperatūrą grįžtamojoje linijoje. Tyrimo rezultatai atskleidė pastato šilumos poreikio sumažėjimo iš CŠT tinklo, šilumos siurblio galios, naudingo veikimo koeficiento (COP) ir grįžtamosios temperatūros sumažėjimo priklausomybes. Reikšminiai žodžiai: centralizuotas šilumos tiekimas, šilumos siurbliai, žemų temperatūrų šilumos tiekimas, naudingo veikimo koeficientas (COP).

The installation of heat pumps in district heating (DH) systems is one of the most promising technologies to increase the efficiency of heat supply by using renewable energy sources and reducing heat carrier temperatures in the networks. The possibilities of installing heat pumps in DH systems are very wide, but most often the main purpose of their application is to increase the temperature of the supplied heat carrier at the heat substations of individual consumers or their groups. This paper describes a study that analyzed the possibilities of integrating an individual heat pump at a heat substation in a building to reduce the temperature of the heat carrier in the return line. The results of the study revealed the dependences of the reduction of the heat demand of the building from the DH network, the power of the heat pump, the coefficient of per [ABSTRACT FROM AUTHOR]

In order to achieve ambitious goals for energy efficiency and requirements for near zero energy buildings, various technological solutions enabling the use of renewable energy are proposed and applied. One such rapidly spreading technology is heat pumps. However, the use of air-to-water heat pumps in countries where the cold season is cold and humid has unfavourable conditions for the operation of this equipment during the heating season. As a result, the performance efficiency of the equipment decreases. This article presents the simulation results of an air-to-water heat pump operation in Lithuania using the TRNSYS modelling tool; its nominal heating capacity is 6.55 kW. The model was calibrated using real data obtained at Vilnius Gediminas Technical University when measurements were performed under heat pump freezing conditions. The seasonal performance factor of the heat pump heating mode was determined during the calculation. Parametric analysis of the model was also performed, when sensitivity of the model to the initial climatic data was observed. Comparable results are obtained for Vilnius, Prague and London. [ABSTRACT FROM AUTHOR]

Heat pumps are becoming increasingly popular and are playing an important role in the heat and cooling supply chain of buildings sector. Although more than 160 years have passed since the manufacture of the first heat pump, this technology, designed to recover low-potential heat energy and its useful use, can be called an innovative and efficient energy transformer. Air-to-water and air-to-air heat pumps are becoming more popular today due to their installation cost compared to ground-to-water heat pumps. It has been noticed that recently air-to-air heat pumps are more often installed in modern air handling units. The main energy transformers in these air handling units are the air-to-air heat pump and recovery heat exchanger. In the scientific literature little attention is paid to the thermodynamic cycle of the combination of the air handling unit and the heat pump, as well as the search for new possibilities to change and control it, this is a potential direction that can increase the efficiency of the whole system. To study the control capabilities of the unit, an experimental stand of the heat pump built into the ventilation unit is needed; it would help validate the results of theoretical studies and investigate the possibilities of expanding the control. Therefore, this paper presents a review of the experimental stands of non-integrated heat pumps and integrated heat pumps in air handling unit. Based on this review, the basic requirements for the installation of an experimental stand of a heat pump built into an air handling unit are formulated and a conceptual scheme of this stand is drawn up. [ABSTRACT FROM AUTHOR]

With the growth of energy-efficient building sector, ventilation systems are becoming increasingly important not only of fresh air supply but also in terms of energy consumption. The aim of this paper is to describe and analyse the operation of an air handling unit (AHU) with a heat pump using energy and exergy analyses under the variable environmental temperature (from –30 °C to 10 °C). The application of selected methods is illustrated in a case study of an AHU using environmental temperatures of Vilnius city during heating season (from the beginning of October to the end of April). An analytical method for determining distribution of the environmental (outdoor air) temperature is used. Energy and exergy analyses showed periods when the highest amounts of energy and exergy were consumed and the greatest exergy losses occurred. This allowed to reveal the component of the system with the highest exergy losses – the heat pump evaporator. Therefore, further research is needed for its design and application. At the end of the article, the seasonal indicators of the AHU with heat pump operation were calculated: coefficient of performance and exergy efficiency. The presented research procedure could be applied to the analysis of other energy systems and processes in them. [ABSTRACT FROM AUTHOR]

Renewable energy technologies are increasingly integrated into the modernization of multi-apartment buildings, however their benefits are rarely assessed from a complex environmental, energy and economic point of view. The article presents the results of the modernization of a particular apartment building in terms of the production and consumption of energy in a building, from the viewpoint of the life cycle. The benefits of the building’s energy modernization were assessed by introducing active (heat pumps and solar collectors for hot domestic water production) and passive modernization measures. The results show that the integration of heat pumps when electricity is produced from non-renewable energy sources according to the analyzed categories of life cycle analysis is not eco-friendly. Santrauka Modernizuojant daugiabučius pastatus, vis dažniau integruojamos atsinaujinančios energijos technologijos, tačiau jų nauda retai vertinama kompleksiniu: aplinkosauginiu, energiniu ir ekonominiu – požiūriais. Straipsnyje pateikiami konkretaus daugiabučio modernizavimo rezultatai, vertinant gaminamą ir suvartotą energiją pastate gyvavimo ciklo požiūriu. Įvertinta pastato energinio modernizavimo nauda diegiant aktyvias (šilumos siurbliai ir saulės kolektoriai karštam vandeniui ruošti) ir pasyvias modernizavimo priemones. Rezultatai rodo, kad šilumos siurblių integravimas, kai elektra nėra gaminama iš atsinaujinančių energijos šaltinių, pagal nagrinėtas gyvavimo ciklo analizės įtakos kategorijas ekologiniu požiūriu nepasiteisina. Reikšminiai žodžiai: atsinaujinantys energijos ištekliai (šaltiniai), centralizuotas šilumos tiekimas, gyvavimo ciklo analizė, pastatų modernizavimas, saulės kolektoriai, šilumos siurbliai.

Renewable energy technologies are increasingly integrated into the modernization of multi-apartment buildings, however their benefits are rarely assessed from a complex environmental, energy and economic point of view. The article presents the results of the modernization of a particular apartment building in terms of the production and consumption of energy in a building, from the viewpoint of the life cycle. The benefits of the building's energy modernization were assessed by introducing active (heat pumps and solar collectors for hot domestic water production) and passive modernization measures. The results show that the integration of heat pumps when electricity is produced from nonrenewable energy sources according to the analyzed categories of life cycle analysis is not eco-friendly. [ABSTRACT FROM AUTHOR]

This paper analyzes an experimental heat pump used for heat recovery in a mechanical room ventilation system. The aim of the work is to examine the operation, control logic of the heat pump and evaluate the possibilities of its operation modes, cycle control by outdoor air temperature. A review of scientific literature and experimental tests of the heat pump were performed to achieve this goal. Tests were performed in three stages, after each stage, according to the results obtained the heat pump stand was improved and experimental modes were adjusted. During the experiment, the tendencies of the heat pump freon and air involved in the heat exchange parameters are analyzed with different combinations of expansion valve positions and compressor power. Knowing these experimental characteristics, the extent to which the combination of these two controls can be used to efficiently control of the heat pump according to the outside air temperature is assessed. Based on the results of the research the heat pump control algorithms (depending on the variable outdoor air temperature) are prepared. [ABSTRACT FROM AUTHOR]

The article analyzes energy supply alternatives for modernised public nearly zero energy buildings. The paper examines alternative energy production systems such as heat pumps (air-water and ground-water), solar collectors, adsorption cooling, biomass boiler, solar photovoltaic, wind turbines and combinations of these systems. The simulation of the analysed building energy demand for different energy production alternatives has been performed using TRNSYS modelling software. In order to determine an optimal energy supply variant, the estimated results of energy, environmental, and economic evaluation have been converted into non-dimensional variables (3E) using multi-criteria analysis. [ABSTRACT FROM AUTHOR]

The article analyses energy supply alternatives for a partially renovated residential building. In addition to the existing district heating (base case) alternative systems, gas boilers, heat pumps (air-water and ground-water), solar collectors, solar cells, and combinations of these systems have been examined. Actual heat consumption of the building and electricity demand determined by the statistical method are used for simulating the systems. The process of simulation is performed using EnergyPro software. In order to select an optimal energy supply option, the life cycle analysis of all systems has been carried out throughout a life span of the building, and the estimated results of energy, environmental and economic evaluation have been converted into non-dimensional variables (3E) using multi-criteria analysis. [ABSTRACT FROM AUTHOR]

This paper evaluates the seasonal thermodynamic efficiency of the air-to-air heat pump used for a heat recovery ventilation system and several modulations of compressors affecting the thermodynamic efficiency of the heat pump. A variable speed and on/off-type compressors have been selected. In order to evaluate the thermodynamic potential of the device, energy analysis has been performed. Along with modelling the operation of the air handling unit during the cold time of the year, variations in the thermodynamic efficiency or different modulation compressors have been com-pared. The obtained results have shown that the use of a few simple compressors causes a decrease in the seasonal parameters of the heat pump: heat generated by a condenser is 5% lower compared to the use of variable speed compressors and therefore the seasonal coefficient of the performance (COP) of the heat pump decreases by 5%. Possible improvement on the heat pump can be provided changing the compressor into variable speed or modulatory equipment, which allows adjusting to heat demand and thus increases the seasonal efficiency of the system from a thermodynamic point of view. [ABSTRACT FROM AUTHOR]

The energy retention problems of heated buildings are treated in the paper. The potential of heat transferred through the building envelope is higher in comparison with the environmental potential at outdoor temperature. Therefore, the idea of endothermic heating with a possibility to avoid heat losses by heat recovery into premises after regeneration in the heat pump is proposed. At present, the ground of outdoor air is used as a source of low potential energy in heat pumps of engineering systems in buildings. Authors have suggested to apply the heat transferred through the building envelope as an energy source in absorbers located in the structure of the building envelope. If all heat losses are recovered, the building will become an adiabatic space. In this case, heat will circulate within the building, generating an endothermic process with some external energy needed for heat pump action. Heat losses in such a building would be almost eliminated at the operation of the proposed heating system. he advantages of the proposed heating system: heat losses of buildings into the environment are eliminated, thermal environmental pollution and greenhouse gas emission are significantly reduced, energy consumption in a building is decreased, especially in comparison with traditional heating systems. An investigation of the experimental model of a building with the endothermic heating system is foreseen at the Institute of Architecture and Construction of the Kaunas University of Technology. [ABSTRACT FROM AUTHOR]