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

Identification of energy use time patterns of occupied dwellings using smart meter data

The increasing application of smart and digital energy meters leads to an increasing availability of frequent -e.g. hourly- and long-term measurements of the actual energy use in occupied buildings. In the resulting energy use time series, the diurnal fluctuations in energy use are recognised and similarities between diurnal profiles for various days are observed. These recurring profiles are called energy use time patterns and they are a result of various phenomena, such as patterns in the building use, occupational schedules, settings of the system control, short-term weather dynamics etc. These energy use time patterns can provide a better understanding of the energy use, which is useful in many fields including energy feedback, fault detection and energy auditing. In order to identify and characterise energy use time patterns for large data-sets, an automated approach is needed. This paper proposes a methodology for automated mathematical recognition of energy use time patterns based on cluster analysis. Secondly, a methodology to characterise the identified patterns in function of external variables is proposed, using classification analysis techniques. The methodologies allow an automated identification and characterization of energy use time patterns, allowing a better understanding of the variations and changes in building energy use and their relation to weather conditions and calendar aspects

Potentials of the new design concepts of district heating and cooling toward integration with renewable energy sources

This paper discusses the opportunities of the new design concepts of district heating and cooling towards the integration of renewable energy sources. A comparison between the medium-temperature district heating and the last generation of low-temperature networks is provided. Simulation models and performance evaluations of three different district heating design concepts are carried out. On one hand, the medium-temperature district heating was modeled with combined heat and power generation. On the other hand, the simulation of the low-temperature district heating was carried out including renewable energy sources such as solar energy, geothermal and wind energy . For the three cases analyzed the customer connection to the district network was carried out by using substation types without a local storage tank. The present work aims to investigate the renewable energy utilization in low-temperature district heating which is modeled as a hybrid solar panel and wind turbine assisted geothermal heat pump. We present a case study for a district heating distribution network which supplies heat to 75 apartments. The paper quantifies the performance of different district heating design concepts. The results highlight the potential of the new district heating design concepts towards solutions for sustainable energy planning

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

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