Super insulation material in district heating pipes

In Swedish district heating systems, 10% of the produced energy is lost at the distribution network. It is of interest to lower the energy losses both for economic and environmental reasons. Since 2011 the feasibility of using superinsulation material for insulation of the district heating pipes were studied. Apparent thermal conductivity and long term performance of vacuum panels has been identified has the crucial challenge for using vacuum insulation panels. The estimated life time of a vacuum panel in building applications at 90 °C is about 50 years. The life time estimation is based on the climate condition valid for building application. However, peak temperature in a district heating system can be about 140°C. Hybrid insulated pipes with a Vacuum Insulated Panel (VIP) have been tested and evaluated by laboratory and field measurements. The results of numerical analyses of the measured data indicate a possible small degradation of the VIP at a similar rate as building application, even though the operative temperature is between 80-100 °C. In the laboratory a hybrid insulated pipe has withstood exposure to one sided heating at 115°C for over 5 years. The results indicate that hybrid insulated district heating pipes reduce heat losses by 20-30% for a twin pipe and with more than 50% in a single pipe. It can be concluded that VIP shows promising performance in district heating pipe application

Super insulation material in district heating pipes

In Swedish district heating systems, 10% of the produced energy is lost at the distribution\ua0network. It is of interest to lower the energy losses both for economic and environmental\ua0reasons. Since 2011 the feasibility of using superinsulation material for insulation of the district\ua0heating pipes were studied. Apparent thermal conductivity and long term performance of\ua0vacuum panels has been identified has the crucial challenge for using vacuum insulation panels.The estimated life time of a vacuum panel in building applications at 90 \ub0C is about 50 years.\ua0The life time estimation is based on the climate condition valid for building application.\ua0However, peak temperature in a district heating system can be about 140\ub0C.\ua0Hybrid insulated pipes with a Vacuum Insulated Panel (VIP) have been tested and evaluated\ua0by laboratory and field measurements. The results of numerical analyses of the measureddata indicate a possible small degradation of the VIP at a similar rate as building application,\ua0even though the operative temperature is between 80-100 \ub0C. In the laboratory a hybrid\ua0insulated pipe has withstood exposure to one sided heating at 115\ub0C for over 5 years. The\ua0results indicate that hybrid insulated district heating pipes reduce heat losses by 20-30% for\ua0a twin pipe and with more than 50% in a single pipe. It can be concluded that VIP shows\ua0promising performance in district heating pipe applications

Development of a Non-destructive Testing Method for Assessing Thermal Status of District Heating Pipes

Pre-insulated district heating (DH) pipes have been in use for more than 40\ua0years. The thermal performance of these pipes decreases over time as a result of thermal and mechanical aging, which leads to higher heat energy losses. A non-destructive method based on a cooling method is under development for assessing the thermal performance of a DH network. The method utilizes the copper wire, which is already embedded in the polyurethane insulation for detection of water leakage, as a sensor for measuring the temperature at the position of the copper wire. The method involves a shutdown of a selected part of a network for less than 2\ua0h and evaluating the cooling process by measuring the supply pipe temperature and the temperature of the copper wire. The method was applied in a DH network during heating season. The thermal conductivity calculated by the method [0.027\ua0W/(m\ua0K)] was in good agreement with the reference value [0.026\ua0W/(m\ua0K)]. The cooling of the network can be measured at a valve or at other more easily accessible steel parts. It was also shown that the method is applicable for DH networks without a copper wire. However, a temperature measurement is needed on the casing pipe

Practical Applications of SIMs: Retrofitting at the Building Scale

In this extended abstract and poster, conclusions from the IEA EBC Annex 65 Subtask 3 on Field scale performance of SIMs are presented. Full scale experiments provide knowledge of practical and technical difficulties as well as data for service life estimations of super insulation materials (SIM). For certain conclusions to be drawn from existing case studies, long-term monitoring is essential. Unfortunately, monitoring is only performed in few case studies. In total 10 case studies using advanced porous materials (APM) and 22 using vacuum insulation panels (VIP), spread over 12 countries on 3 continents, have been scrutinized. Four main remaining challenges were identified and the status of these are discussed in the report based on discussions throughout IEA EBC Annex 65. The long-term performance (25-100 years) cannot be entirely determined due to lack of data for longer time period exceeding 15 years. However, there were few claims concerning the malfunction of SIMs in construction

Hydronic Pavement Heating for Sustainable Ice-free Roads

Hydronic pavement is an alternative method for de-icing of roads. A hydronic pavement (HP) could be more environmental friendly than traditional de-icing methods such as salting. The HP system consists of embedded pipes in the pavement structure, with a fluid as energy carrier. The performance of a HP system strongly depends on a number of parameters e.g. the location of the pipes, the thermal properties of pavement structure and the temperature level of the heat storage system. In this paper initial results related to the designing of a HP system are presented

Impacts of climate change and its uncertainties on the renewable energy generation and energy demand in urban areas

This work investigates the effects of future climate uncertainties in calculating the heating and cooling demand of buildings and estimating potentials for renewable energy generation (solar PV and wind). The building stock of Lund in Sweden is considered for energy simulations and for future climate, the most recent outputs of RCA4, which is the 4th generation of the Rossby Centre regional climate model (RCM), is used considering several two representative concentration pathways (RCPs) and four global climate models (GCMs). Simulations and assessment are performed for three 30-year time periods, from 2010 until 2099. Through comparing distributions of data sets, it is found that the uncertainty induced by climate models affects the estimation of renewable energy generation more than those induced by time periods. Changes in the heating demand due to climate change and uncertainties are surprisingly low while it is very large for cooling demand. This can be because of having a good quality for buildings on the average, however this should be more investigated for other cities in Sweden

Diagnostic protocol for thermal performance of district heating pipes in operation. Part 2: Estimation of present thermal conductivity in aged pipe insulation

Buried and operating district heating (DH) pipes are exposed to thermal degradation of their polyurethane (PUR) insulation over time, and their status is hard to assess without excavation. By using DH pipe valves in manholes as measurement points during a shutdown with an ensuing cooling period, non-destructive assessments can be performed. This study compares new improved field measurements with numerical simulations of the temperature decline in drainage valves and shutdown valves. The drainage valve measurements were used to thermally assess part of a buried DH network. Results indicate that by using the drainage valves as measurement points in a cooling method, the thermal conductivity of the buried DH network could be predicted with an accuracy of >95%. In addition, a general diagnostic protocol has been established for assessing the thermal status of a DH network, ready for network owners to use

Impacts of climate change and its uncertainties on the renewable energy generation and energy demand in urban areas

This work investigates the effects of future climate uncertainties in calculating the heating and cooling demand of buildings and estimating potentials for renewable energy generation (solar PV and wind). The building stock of Lund in Sweden is considered for energy simulations and for future climate, the most recent outputs of RCA4, which is the 4th generation of the Rossby Centre regional climate model (RCM), is used considering several two representative concentration pathways (RCPs) and four global climate models (GCMs). Simulations and assessment are performed for three 30-year time periods, from 2010 until 2099. Through comparing distributions of data sets, it is found that the uncertainty induced by climate models affects the estimation of renewable energy generation more than those induced by time periods. Changes in the heating demand due to climate change and uncertainties are surprisingly low while it is very large for cooling demand. This can be because of having a good quality for buildings on the average, however this should be more investigated for other cities in Sweden

Strategy for visualisation of the activity of phase change materials by transient plane source technique

Through a combination of theoretical and experimental research, this paper aims at evaluating the suitability of a transient plane heat source (TPS) method for the visualisation of the activity of phase change materials (PCMs). The TPS method provides measurements of thermal conductivity and thermal diffusivity of a material in a transient course. It has previously been tested on various building materials but not on PCMs. In this study TPS was tested in a laboratory environment on two inorganic PCMs (salt-hydrates), with melting temperatures 21 oC and 24 oC respectively. Based on the experimental trials, the technique has shown to be a valuable technique for the identification of the activity of phase change material

Determination of anisotropic thermal conductivity of VIP laminate using transient plane source method

The use of super insulation materials, such as vacuum insulation panels (VIP), is expected toincrease in buildings in the future. One key aspect for successful implementation is the qualitycontrol. At the factory, the thermal performance can easily be controlled by measuring theinternal pressure of the VIP. Preferably, the performance should be controlled again at theconstruction site before installation. The thermal conductivity of a VIP is possible to measureby using the transient plane source method (TPS). This method uses a sensor which measurethe temperature increase during a heat pulse. For the analysis of the measurement, informationon the thermal conductivity of the metalized multi-layer polymer laminate, used around the VIP,is needed. This paper presents the results obtained from different measurement setups of thelaminate. The aim of the study is to identify a practical approach to analyse the results, and togive recommendations on the best measurement setup. Two measurement submodules wereused; ‘anisotropic’ and ‘thin film’. The thermal conductivity of the laminate was measured inplaneand perpendicular to in-plane. The volumetric heat capacity was measured by differentialscanning calorimeter (DSC). The measurement results were compared to calculations. Theresults from the ‘anisotropic’ module was in best agreement with the calculated results. It wasalso illustrated that the TPS may be used for relative measurements to find damaged VIP