Customer unit substation of collective heat distribution system : Benchmark of hot water comfort test standard and methodologies

The performance assessment of dwelling heating substations in terms of level of comfort is usually studied regarding temperature overshoots, stationary temperature deviations and settling time among other parameters. In fact, several standards and test methods can be found focusing on a specific target or technology. However, these methods do not always provide clear information about hot water comfort. As a result planners, developers and customers have difficulties to compare a substation product with products using other technologies for the heating of sanitary hot water. The study investigates the compatibility of already existing methods and intends to evaluate their applicability to systems where the sanitary hot water is prepared in an instantaneous way by using a heat exchanger in a district heating substation. In order to achieve that aim, a dynamic simulation model of a test setup (using TRNSYS) has been developed. The test procedures, as well as the simulation results, are described and discussed. This analysis is expected to provide the basis for an integrated performance assessment test of this kind of devices

Sensitivity analysis of heat losses in distribution systems : impact of different buildings typologies

This paper focuses on the sensitivity of heat losses in collective heat distribution systems using a simplified calculation method. The methodology considers several parameters influencing the performance of heat distribution systems. Hence, the thermal properties of the heat exchanger in the dwelling heating substation and the return temperature of sanitary hot water are considered. In addition, the recirculation control strategy, the length of service branch which is included or not in the recirculation as well as, the share in a building of dwelling heating substation with similar characteristic and control strategy are also taken into account. The present study assess the impacts of some potential variations in the input variables, on the conclusions of the methodology. A comparison of the sensitivity of heat losses in the heating distribution system between four different buildings typologies, i.e. with 13, 24, 25 and 49 apartments, is provided. In order to identify the influence of building typology and pipe layout in the heat losses calculation, for the four cases the sensitivity analysis was carried out. A study was conducted through sensitivity analysis by means of an experimental design, consisting of the combinations of parameters which were varied from the levels at which they were set. Results shows how sensitive the solution is in the face of different parameter values as well as under what circumstances the solution would change. The suitability of the improved method which allow more flexibility to consider different pipe layout characteristic within a heating distribution system was demonstrated

Simulation models and performance assessment of district heating substations

Development of new technologies and methodologies regarding district heating substation operational control strategies are increasingly found nowadays. At the same time a great number of modern buildings are provided with energy monitoring and control systems which supervise and collect operating data from different energy components. Accordingly, an exemplary district heating systems is being implemented in the city of Kortrijk in Belgium, as part of a demonstration zero-carbon neighborhood. This study deals with the energy performance assessment of one of the systems component -the consumer substationinstalled in this low-temperature district heating system. A comparative analysis of the energy performance with several existing district heating substations was carried out. Three different district heating substation models are set up (using TRNsys) for investigation of the gross energy use, energyefficiency and comfort issues. In order to evaluate the performance of the analyzed substations two scenarios concerning the space heating system (radiator or floor heating system) were considered. The study aims to investigate the impact of different operational circumstances on the performance of district heating substations. The study generate understandings for energy saving operational strategies to be developed. Results indicate that the design concept together with a suitable selection of the substation has an important impact on the energy performance of the entire system

Thermal comfort and indoor air quality on end-user satisfaction level evaluation in a Nearly Zero Carbon neighbourhood

End-user satisfaction studies in residential buildings has to be approached combining the user’s perspective and technical criteria to consider the complex interactions influencing the building energy performance. Therefore, in this study the physical characteristics of dwellings and their environments are assessed, user satisfaction is examined, and the relationship between them is investigated. The study aims to illustrate the end-user satisfaction in exemplary high performance buildings and to investigate how the users are interacting with these buildings. Examination of the building performance, thermal comfort and indoor air quality are the main focal points of the work. In general, results reflect a significant improvement on the satisfaction level of the inhabitants with the comfort of the dwelling after the refurbishment of the district. Findings from the cross-analysis of both surveys and measurements are used to further refine conclusions and identify the driving factors of the interrelationship between building performance and end-user satisfaction

Building energy performance characterisation based on dynamic analysis and co-heating test

A demonstration zero-carbon neighborhood is being raised in the city of Kortrijk, Belgium in the framework of the ECO-Life project within the CONCERTO initiative. A holistic approach is applied to achieve the zero-carbon targets, considering all aspects that are relevant for energy supply. Accordingly, alongside the integration of renewable energy sources in the community, a low-temperature district heating system is being implemented to cover the heat demand. In this context, full scale testing of building thermal performances, by use of a co-heating test and flux measurements, can be useful to analyze the thermal performance of the building envelope in situ. For that reason, as part of a more general study regarding low-energy building, co-heating test, blower-door test and flux measurements in several apartments were executed. Therefore, the paper focuses on characterization of the thermal dynamic behavior of an apartment, as a first approximation of data analysis of a monitoring system involving whole buildings. In addition, in the present study, the capability of linear regression techniques to characterize the thermal behavior of a newly built low-energy apartment in Belgium is investigated. The strengths and weaknesses of different models are identified. The limitation and possibilities of regression models are evaluated in the face of their applicability as a simplified building equation model. The identified model structure is going to be used within a complex simulation model of an entire district heating system with around 200 dwelling. Finally, the potential of this kind of regression models to be used as part of the operational control scheme of a district heating system is presented

Actual energy performance of a zero-carbon neighbourhood

The evolution towards zero-energy buildings and districts brings along uncertainties about the operational performance, strengths and weaknesses of these technologies, that are often new and unfamiliar to both the designers, owners and users. In Kortrijk, an exemplary zero-carbon neighbourhood is designed, built and evaluated in the framework of a European demonstration project ECO-Life ‘Sustainable zero-carbon ECO-town developments improving quality of life across EU’. The neighbourhood counts about 200 dwellings in highly energy-efficient buildings with different ventilation technologies and collective RES based on solar, biomass or aero-thermal energy. During the building process and the first years of operation, the energy performance of the neighbourhood is evaluated after intensive monitoring and testing by Ghent University’s research group of building physics, construction and services. This paper presents two focal points of the research: the energy demand of the buildings and the interaction with the occupants, and the energy performance of the neighbourhoods' low-temperature district heating system

A decision-making methodology for selecting trigeneration systems

The paper considers the selection of a cogeneration system as a multicriteria decision-making problem, which involves economical, technical, thermodynamic and environmental issues. Taking into account the preference information given by the Decision-Maker (DM) about the weight of each criterion, a ranked set of alternatives is obtained by solving a discrete optimization problem based on the Tchebycheff metric. The problem definition, the structure and the solution algorithms are described. The DM can identify the most favorable alternatives in a finite number of steps. The method is illustrated with the help of an example

Heat losses in collective heat distribution systems: comparing simplified calculation methods with dynamic simulations

Heat losses in collective heat distribution systems can be reduced significantly in well-insulated and well-controlled low-temperature networks. However, this reduction is not always rewarded for in legislative energy performance of building standards in Europe. In this paper, simplified heat loss calculation methods (SCM) are compared to dynamic simulations for networks that distribute heat for both space heating and domestic hot water to low-energy houses. Results show that SCMs overestimate the distribution heat losses in these systems and that the variation in heat losses due to seasonal behaviour and control strategies is little addressed. An investigation of the influential parameters showed that they can be significantly improved by a more accurate estimation of the working time of the system and average temperature of the heat conducting medium

Performance evaluation of a low temperature district heating system based on simulation, uncertainty and sensitivity analysis

This paper describes the simulation model and the performance evaluation of a low energy district heating distribution network which supplies heat to 75 apartments. Suitable criteria of thermal operation are selected: the relative heat loss in the distribution system, the specific heat loss, the heat density, the total energy consumption and the seasonal performance factor of the system. The purpose is to investigate the uncertainties on the performance of district heating systems introduced by parameters influencing heat losses in the distribution network. An uncertainty and sensitivity analysis were conducted. The analysis was carried out by using the simnulation data of one week in winter period. Results regarding performance assessment and uncertainty are discussed. They show how sensitive the solution is in the face of different parameter values and especially the interactions between them. The results demonstrate that by using a central storage tank in the heating production plant the robustness of the system increases