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- Averfalk, Helge, 1988-, et al.
(författare)
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Low-Temperature District Heating Implementation Guidebook : Final Report of IEA DHC Annex TS2. Implementation of Low-Temperature District Heating Systems
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This guidebook was written between 2018 and 2021 by seventeen authors that used approximately 15 000 hours of work within the IEA DHC TS2 annex. The content is based on more than 250 literature references and 165 inspiration initiatives to obtain lower temperatures in buildings and heat distribution networks. The author group wrote 40 internal documents about early implementations of low-temperature district heating. Fifteen of these early implementations are presented in this guidebook.The guidebook contains aggregated information about the main economic drivers for low-temperature district heating. It shows how to obtain lower temperatures in heating systems inside existing and new buildings, as well as in existing and new heat distribution networks. An applied study of a campus system in Darmstadt shows the possibility of reducing temperatures in an existing heat distribution network with rather high temperatures. The competitiveness of low-temperature district heating is explored by analysing business models and heat distribution costs. Early adopters of low-temperature district heating are presented by examples and by identified transition strategies. Five groups of network configurations with fourteen variants are presented to be used for low-temperature district heating. Finally, all 165 identified inspiration initiatives and all 137 locations mentioned are listed.
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| 3. |
- Dalla Rosa, Alessandro, et al.
(författare)
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Annex X Final report : Toward 4th Generation District Heating: Experience and Potential of Low-Temperature District Heating
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Background and ObjectiveThe evolution of district heating (DH) has gone through three generations since the first introduction of distirct heating. It is characterized by the type of transport media and the network temperature levels: the 1st generation DH system is steam-based system, the 2nd generation DH uses high network supply temperature above 100oC, and the 3rd generation DH represents the current DH system with medium network supply temperature between 80oC to 100oC. Up until now, the 4th generation DH as the low-temperature district heating (LTDH) is emerging as a new system which is going to replace the existing 3rd generation DH system. Comparing with the existing DH system, the LTDH reduces the network supply temperature down to consumer required temperature level, thus greatly improves the quality match between the energy supply and the energy demand. Meanwhile, LTDH coupling with reduced network temperature and well-designed DH network can reduce network heat loss by up to 75% comparing with the current system. This makes DH economically competitive comparing with local heat generation units in the areas with low heat density or with low-energy buildings.The traditional approach to evaluating a DH system often focuses on the production/supply aspect and only afterwards on the final users. The LTDH concept switches the perspective, starting from end-user thermal comfort and a quality match between energy supply and energy consumption, and aiming to find the best and most economical way to satisfy the heat demand through efficient distribution networks and supply systems based on waste heat and RE. The new concept therefore starts by identifying suitable in-house substations for low-energy-demand buildings at low supply temperature, goes back to design efficient and reliable networks, and finally considers environmentally-friendly heat production units.This report describes the concept of LTDH, collects and discusses successful examples of implementation LTDH in the building heating sector. The objective of this report is to raise awareness and provide insights that will stimulate the research, development and implementation of LTDH systems. It will help to increase public recognition and assist policy makers and energy planners, both at local and governmental level, in promoting cost-effective and environmentally friendly DH systems, and in planning and realizing long-term sustainable urban area development. To this end, the report addresses the following research issues:1. What are the main advantages of LTDH?2. What technology options are available for LTDH, and what are the associated challenges to consider?3. How can the risk of Legionella be mitigated in LTDH?4. What lessons can be learned from early LTDH projects?5. What heat distribution costs are associated with LTDH?
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| 4. |
- Dodoo, Ambrose
(författare)
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Life cycle primary energy use and carbon emission of residential buildings
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, the primary energy use and carbon emissions of residential buildings are studied using a system analysis methodology with a life cycle perspective. The analysis includes production, operation, retrofitting and end-of-life phases and encompasses the entire natural resource chain. The analysis focuses, in particular, on to the choice of building frame material; the energy savings potential of building thermal mass; the choice of energy supply systems and their interactions with different energy-efficiency measures, including ventilation heat recovery systems; and the effectiveness of current energy-efficiency standards to reduce energy use in buildings. The results show that a wood-frame building has a lower primary energy balance than a concrete-frame alternative. This result is primarily due to the lower production primary energy use and greater bioenergy recovery benefits of wood-frame buildings. Hour-by-hour dynamic modeling of building mass configuration shows that the energy savings due to the benefit of thermal mass are minimal within the Nordic climate but varies with climatic location and the energy efficiency of the building. A concrete-frame building has slightly lower space heating demand than a wood-frame alternative, because of the benefit of thermal mass. However, the production and end-of-life advantages of using wood framing materials outweigh the energy saving benefits of thermal mass with concrete framing materials.A system-wide analysis of the implications of different building energy-efficiency standards indicates that improved standards greatly reduce final energy use for heating. Nevertheless, a passive house standard building with electric heating may not perform better than a conventional building with district heating, from a primary energy perspective. Wood-frame passive house buildings with energy-efficient heat supply systems reduce life cycle primary energy use.An important complementary strategy to reduce primary energy use in the building sector is energy efficiency improvement of existing buildings, as the rate of addition of new buildings to the building stock is low. Different energy efficiency retrofit measures for buildings are studied, focusing on the energy demand and supply sides, as well as their interactions. The results show that significantly greater life cycle primary energy reduction is achieved when an electric resistance heated building is retrofitted than when a district heated building is retrofitted. For district heated buildings, the primary energy savings of energy efficiency measures depend on the characteristics of the heat production system and the type of energy efficiency measures. Ventilation heat recovery (VHR) systems provide low primary energy savings where district heating is based largely on combined heat and power (CHP) production. VHR systems can produce substantial final energy reduction, but the primary energy benefit largely depends on the type of heat supply system, the amount of electricity used for VHR and the airtightness of buildings.Wood-framed buildings have substantially lower life cycle carbon emissions than concrete-framed buildings, even if the carbon benefit of post-use concrete management is included. The carbon sequestered by crushed concrete leads to a significant decrease in CO2 emission. However, CO2 emissions from fossil fuels used to crush the concrete significantly reduce the carbon benefits obtained from the increased carbonation due to crushing. Overall, the effect of carbonation of post-use concrete is small. The post-use energy recovery of wood and the recycling of reinforcing steel both provide higher carbon benefits than post-use carbonation.In summary, wood buildings with CHP-based district heating are an effective means of reducing primary energy use and carbon emission in the built environment.
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| 5. |
- Haavik, Trond, et al.
(författare)
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New business models for holistic renovation solutions of single family houses
- 2011
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Konferensbidrag (refereegranskat)abstract
- Single family houses represent the biggest potential for energy savings within residential buildingsin the Nordic countries. In earlier research project [1] it highlighted that there is a missing linkbetween the single family house owner and various segregated offers of single solutions forrenovation and/or energy efficiency installations. In the two international research projectsSuccessFamiles and One Stop Shop, establishment of new business models as pilots for bridgingthis gap are now being monitored.Two of the pilots as “one stop shops”, a retailer chain in Finland and a daughter company of aNorwegian manufacturer of insulation, are described and discussed.A key issue for any business model which offers an integrated service from analysis of the houseand recommendations for measures is the trustworthiness of the supplier.As a holistic energy efficient renovation project is a “new” and unknown service to single familyhouse owner and at same time a costly investment, it is important for the suppliers to findadequate ways of communicating through each phase of the buying process. There are variouschallenges in each of the phases which have to be solved differently.
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| 7. |
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| 8. |
- Liv, Per, et al.
(författare)
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Accuracy and precision of variance components in occupational posture recordings : a simulation study of different data collection strategies
- 2012
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Ingår i: BMC Medical Research Methodology. - : Springer Science and Business Media LLC. - 1471-2288. ; 12:1, s. 58-58
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Tidskriftsartikel (refereegranskat)abstract
- Background. Information on exposure variability, expressed as exposure variance components, is of vital use in occupational epidemiology, including informed risk control and efficient study design. While accurate and precise estimates of the variance components are desirable in such cases, very little research has been devoted to understanding the performance of data sampling strategies designed specifically to determine the size and structure of exposure variability. The aim of this study was to investigate the accuracy and precision of estimators of betweensubjects, between-days and within-day variance components obtained by sampling strategies differing with respect to number of subjects, total sampling time per subject, number of days per subject and the size of individual sampling periods. Methods. Minute-by-minute values of average elevation, percentage time above 90degrees and percentage time below 15degrees were calculated in a data set consisting of measurements of right upper arm elevation during four full shifts from each of 23 car mechanics. Based on this parent data, bootstrapping was used to simulate sampling with 80 different combinations of the number of subjects (10, 20), total sampling time per subject (60, 120, 240, 480 minutes), number of days per subject (2, 4), and size of sampling periods (blocks) within days (1, 15, 60, 240 minutes). Accuracy (absence of bias) and precision (prediction intervals) of the variance component estimators were assessed for each simulated sampling strategy. Results. Sampling in small blocks within days resulted in essentially unbiased variance components. For a specific total sampling time per subject, and in particular if this time was small, increasing the block size resulted in an increasing bias, primarily of the between-days and the within-days variance components. Prediction intervals were in general wide, and even more so at larger block sizes. Distributing sampling time across more days gave in general more precise variance component estimates, but also reduced accuracy in some cases. Conclusions. Variance components estimated from small samples of exposure data within working days may be both inaccurate and imprecise, in particular if sampling is laid out in large consecutive time blocks. In order to estimate variance components with a satisfying accuracy and precision, for instance for arriving at trustworthy power calculations in a planned intervention study, larger samples of data will be required than for estimating an exposure mean value with a corresponding certainty
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| 10. |
- Liv, Per, 1979-, et al.
(författare)
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Theoretical and empirical efficiency of sampling strategies for estimating upper arm elevation
- 2011
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Ingår i: Annals of Occupational Hygiene. - : Oxford University Press (OUP). - 0003-4878 .- 1475-3162. ; 55:4, s. 436-449
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To investigate the statistical efficiency of strategies for sampling upper arm elevation data, which differed with respect to sample sizes and sample allocations within and across measurement days. The study was also designed to compare standard theoretical predictions of sampling efficiency, which rely on several assumptions about the data structure, with 'true' efficiency as determined by bootstrap simulations.METHODS: Sixty-five sampling strategies were investigated using a data set containing minute-by-minute values of average right upper arm elevation, percentage of time with an arm elevated <15°, and percentage of time with an arm elevated >90° in a population of 23 house painters, 23 car mechanics, and 26 machinists, all followed for four full working days. Total sample times per subject between 30 and 240 min were subdivided into continuous time blocks between 1 and 240 min long, allocated to 1 or 4 days per subject. Within day(s), blocks were distributed using either a random or a fixed-interval principle. Sampling efficiency was expressed in terms of the variance of estimated mean exposure values of 20 subjects and assessed using standard theoretical models assuming independence between variables and homoscedasticity. Theoretical performance was compared to empirical efficiencies obtained by a nonparametric bootstrapping procedure.RESULTS: We found the assumptions of independence and homoscedasticity in the theoretical model to be violated, most notably expressed through an autocorrelation between measurement units within working days. The empirical variance of the mean exposure estimates decreased, i.e. sampling efficiency increased, for sampling strategies where measurements were distributed widely across time. Thus, the most efficient allocation strategy was to organize a sample into 1-min block collected at fixed time intervals across 4 days. Theoretical estimates of efficiency generally agreed with empirical variances if the sample was allocated into small blocks, while for larger block sizes, the empirical 'true' variance was considerably larger than predicted by theory. Theory overestimated efficiency in particular for strategies with short total sample times per subject.CONCLUSIONS: This study demonstrates that when exposure data are autocorrelated within days-which we argue is the major reason why theory overestimates sampling performance-sampling efficiency can be improved by distributing the sample widely across the day or across days, preferably using a fixed-interval strategy. While this guidance is particularly valid when small proportions of working days are assessed, we generally recommend collecting more data than suggested by theory if a certain precision of the resulting exposure estimate is needed. More data per se give a better precision and sampling larger proportion(s) of the working day(s) also alleviate the negative effects of possible autocorrelation in data.
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