Search

This technical report combines research results from the Norwegian Research Center on Zero Emission Buildings (ZEB) and a competence project about simplified hydronic distribution funded by Husbanken. In the Norwegian definition of the passive house standard (NS3700), the current building code TEK10 or existing concepts of ZEB residential buildings, building envelopes are so-called super-insulated in order to drastically reduce the space-heating needs. Given this high level of insulation, it is theoretically possible to simplify the space-heating distribution inside the building by reducing the number of heat emitters. There is currently a lack of theoretical knowledge about the design of simplified distribution systems and lack of evidence-based feedbacks about their actual performance during real operation. The present work investigates the performance of simplified space-heating distribution in superinsulated residential buildings using one radiator per floor. The case with less than one heat emitter per floor is not considered here. In all investigated cases, the building was equipped with balanced mechanical ventilation with one centralized heat recovery and one set-point temperature for the supply ventilation air (sometimes called one-zone mechanical ventilation). In other words, all the supply ventilation air is preheated at the same temperature, without distinction between rooms. The research methodology is based on field and laboratory measurements, calibrated detailed dynamic simulations (using IDA-ICE) as well as user’s interviews. The main research question was to investigate the real, desired and perceived thermal environment in heated areas (like the living room) and in the rooms without radiators (like bedrooms). In this context, the question of window openings in bedrooms was also addressed. The research also investigated the user behavior, such as the way users operate the heating system in reality. In addition... Acknowledgement. This report has been written within the Research Centre on Zero Emission Buildings (ZEB). The authors gratefully acknowledge the support from the Research Council of Norway, BNL – Federation of construction industries, Brødrene Dahl, ByBo, DiBK – Norwegian Building Authority, Caverion Norge AS, DuPont, Entra, Forsvarsbygg, Glava, Husbanken, Isola, Multiconsult, NorDan, Norsk Teknologi, Protan, SAPA Building Systems, Skanska, Snøhetta, Statsbygg, Sør-Trøndelag Fylkeskommune, and Weber. Husbanken partly funded this research through a competence project for sustainable buildings and building quality entitled evaluation of the simplified hydronic heating system in Norwegian passive houses.

CFD modelling of wood stoves are a challenge due to the transient behavior of the combustion process, due to their batch combustion principle. Various initial and boundary conditions needs to be specified to carry out a CFD simulation of a wood stove, and many of these will be a result of sub-models that again can be partly based on experimental results. This paper deals with these boundary conditions and the generation of representative values for these as input to stationary and transient CFD simulations throughout the batch combustion process as well as thermal comfort simulations. Additionally, heat production profiles and stove wall properties are needed to calculate heat release profiles to the room in which the stove is placed. These heat release profiles are essential input for evaluating the thermal comfort of wood stoves in houses, a subject which has received considerable attention recently as energy efficient houses are increasingly introduced. Necessary boundary conditions relates to the fuel and air introduction into the computational domain and the thermal and radiative properties of the surfaces within and enclosing the computational domain. In addition initial conditions must be specified as starting point for the transient models generating the boundary conditions at any time in the batch combustion process. The ultimate goal would be to carry out transient CFD simulations where the boundary conditions are derived for each new stationary simulation based on the results from the previous time step. The choice of models and the degree of detail of these regarding e.g. the handling of the gas phase chemistry are very important. In this paper a feasible modelling approach is presented that together with experiments could be used to cost-efficiently design future's high performance wood stoves. Copyright © 2015, AIDIC Servizi S.r.l. Open Access.

This report presents the results from a sensitivity analysis regarding the influence of using emission data from Norwegian EPD’s instead of the generic data from Ecoinvent, using different CO2eq-factors (for electricity in the operational phase) and electricity load from household appliances on the overall ZEB residential building performance. The materials which contribute the most to the embodied greenhouse gas emissions in the original ZEB concept residential building were selected [1]. The sensitivity analysis is performed by replacing the generic Ecoinvent data with Norwegian EPD data where available. Even though the embodied emissions from PV contribute the most emissions, they are not included in this analysis due to the lack of Norwegian EPD data for PV. Instead, the influence of different PV technologies and different module orientations on the embodied and avoided emissions is incorporated. Even if the calculation of embodied emission has uncertainties, the results indicate the annual embodied emissions reduction from 7.2 kg CO2eq/m2 to 5.8 kg CO2eq/m2 when the generic data is replaced with Norwegian EPD data. In addition, the sensitivity study investigates the influence of CO2eq-factors for electricity in the operational phase on the emission balance. Furthermore, the analysis discusses the energy consumption of electric appliances and how it could be reduced through more efficient products, especially the hot-fed machines (i.e. washing machines, tumble dryer and dishwasher). The ZEB Centre has chosen an average CO2eq factor of 132 g CO2eq/KWh for electricity in the operational phase of the building's lifetime of sixty years. ZEB ambition level ZEB-OM can still not be reached for the residential concept building. However, to choose higher European CO2eq factors make it possible to achieve this ambition. In further work, the calculation of embodied emissions using Norwegian EPD data for other construction materials should be incorporated. In the second stage of the work, the system boundary should be extended to include end of life emissions. There is further potential to reduce the embodied emissions by considering the biogenic carbon stored in wood products and the use of alternative building materials should also be considered. In addition, further work is thus required to define the potential energy saving that would result from a shift of standard appliances to high-performance appliances with better energy efficiency. © Copyright SINTEF Academic Press and Norwegian University of Science and Technology 2015

The indoor emission of (ultra)fine particles and overheating from wood-burning stoves are crucial problems in modern houses when wood is used for heating. The main cause for indoor particle emission is the interaction between user and stove when lighting and refilling the stove. The main causes for overheating are a high thermal insulation level of the house and high (peak) wattage of the stove.This research aims to understand how low wattage stoves with a computer added device and water jacket will perform on the indoor air quality as proper heating appliances for low energy houses.Two field studies were designed to compare the influence of the auto-pilot device and water jacket on the indoor climate. The first experiments were conducted in 8 renovated detached houses using certified stoves while the following experiments were conducted in 4 low energy houses using modern and advanced stoves.The results reveal that the users interaction impacts on the indoor air quality, although, the integration of the appliances in the dwellings, the air-inlets and the design of the chimney are the most relevant aspects to ensure a high indoor air quality.

This report deals with how to define what a Zero Emission Building (ZEB) is with explanation and analysis of different parameters related to embodied emissions of CO2 equivalents. The report can be used as a guidance tool on how to assess embodied emissions, and also on what parameters should be evaluated in such an assessment. Different ambition levels for ZEBs may include life stages, operation, material, construction and end-oflife and can be documented according to EN 15978. Calculation procedures should include system boundaries, embodied emissions from materials, transport, the construction process and waste handling according to the ambition level. CO2 eq emissions factors, service life estimates and payback scenarios for CO2 emissions need to be considered. The report does not contain one single clearly defined method, but rather a state-of-the-art summary on the different issues and refers to other relevant national and international work in the field of ZEB definitions. The issues presented here are in early stages of development and will need to be verified and further developed.

The main aim of the work has been to do modeling and calculations of the energy use, embodied emission and the total CO2-emission for a typical Norwegian residential building. By doing this we try to reveal and study the main drivers for the CO2-emission, and also which performance is necessary for components and solutions in a Zero Emission Building according to the current Norwegian ZEBdefinition. The preliminary conclusions from this study are: 1. For a typical single family home (2 storeys) it is rather easy to achieve a ZEB-O (Operation) level, which in this case can be labeled a zero energy building (energy produced on-site with PV equals total electricity demand). 2. Taking into account also the embodied emissions from materials and installations it is difficult to achieve the ZEB-OM (Operation and Material) level by using only the flat roof for PV-production. 3. Even if the calculation of embodied emission (EE) has considerable uncertainties, preliminary results indicate that EE is significantly higher than the emission related to operational energy use. However, in current calculation no significant effort has been made to reduce EE, in contrast to operational energy use where high performance solutions have been used. 4. To achieve a ZEB-OM level a combination of further reduced energy demand, high COP/SPF thermal systems, reduced embodied emissions and increased PV-production seems to be the solution.

Analyse par simulation thermique dynamique de scénarios de rénovation énergétique enveloppe-systèmes HVAC de maisons individuelles à Basse Energie et Très Basse Energie.

Turbulent flows present structures with a wide range of scales. The computation of the complete physics of a turbulent flow (termed DNS) is very expensive and is, for the time being, limited to low and medium Reynolds number flows. As a way to capture high Reynolds number flows, a part of the physics complexity has to be modeled. Large eddy simulation (LES) is a simulation strategy where the large turbulent eddies present on a given mesh are captured and the influence of the non-resolved scales onto the resolved ones is modeled. The present thesis reports on the development and validation of a methodology in order to apply LES for complex wall-bounded flows. Discretization methods and LES models, termed subgrid scale models (SGS), compatible with such a geometrical complexity are discussed. It is proved that discrete a kinetic energy conserving discretization of the convective term is an attractive solution to perform stable simulations without the use of an artificial dissipation, as upwinding. The dissipative effect of the SGS model is thus unaffected by any additional dissipation process. The methodology is first applied to a developed parallel fourth-order incompressible flow solver for cartesian non-uniform meshes. In order to solve the resulting Poisson equation, an efficient multigrid solver is also developed. The code is first validated using DNS (Taylor-Green vortex, channel flow, four-vortex system) and LES (channel flow), and finally applied to the investigation of an aircraft two-vortex system in ground effect. The methodology is then applied to improve a RANS-based industrial unstructured compressible flow solver, developed at CENAERO, to perform well for LES applications. The proposed modifications are tested successfully on the unsteady flow past a sphere at Reynolds of 300 and 10000, corresponding to the subcritical regime. (FSA 3)--UCL, 2007

In this paper, we investigate the non-preemptive scheduling problem as it arises in single processor systems. We focus on non-idling scheduling, the idling scheduling is briefly introduced in the last section. We extend some previous published results concerning preemptive and non-preemptive scheduling over a single processor. The main issue that we study in this article is the applicability and/or adaptation of results obtained in preemptive scheduling. In a first part we embark on revisiting aperiodic non idling non preemptive scheduling. We review complexity results and investigate conditions under which Earliest Deadline First is optimal in non preemptive scheduling. In a second part, we scrutinize periodic non idling non preemptive scheduling and we show that for non preemptive scheduling feasibility must be checked on a time interval of duration r+2P (r denotes the maximum of the release times and P the smallest common multiple of the task periods). We also show that a well established result concerning feasibility of task sets under non preemptive scheduling (no overload on any given time intervals) has no equivalence in non preemptive scheduling even if one takes into account the blocking factor. The third part is a very quick introduction to scheduling problems in an idling and non preemptive context.