Energy flexibility of buildings can be used to reduce energy use and costs, peak power, CO2eq- emissions or to increase self-consumption of on-site electricity generation. Thermal mass activation proved to have a large potential for energy flexible operation. The indoor temperature is then allowed to fluctuate between a minimum and maximum value.
Many studies investigating thermal mass activation consider electric radiators. Nevertheless, these studies most often assume that radiators modulate their emitted power, while, in reality, they are typically operated using thermostat (on-off) control.
Firstly, this article aims at comparing the energy flexibility potential of thermostat and P-controls for Norwegian detached houses using detailed dynamic simulations (here IDA ICE). It is evaluated whether the thermostat converges to a P-control for a large number of identical buildings. As the buildings are getting better insulated, the impact of internal heat gains (IHG) becomes increasingly important. Therefore, the influence of different IHG profiles has been evaluated in the context of energy flexibility. Secondly, most studies about energy flexibility consider a single indoor temperature. This is questionable in residential buildings where people may want different temperature zones. This is critical in Norway where many occupants want cold bedrooms (~16°C) during winter time and open bedroom windows for this purpose.
This article answers to these questions for two different building insulation levels and two construction modes (heavy and lightweight).
Optimal ventilation strategies are fundamental to achieve net/nearly-zero energy buildings.
In this study, three hybrid ventilation control strategies are proposed to minimize the cooling need in an open-plan office building, located in the center of Glasgow (Scotland). The performance of the three proposals is assessed by IDA ICE (a whole building performance simulation tool) and compared to a traditional fully mechanical ventilation system.
The performance comparison includes different criteria (i.e., indoor temperature and predicated percentage of dissatisfied (PPD) for assessing the indoor comfort and CO2 level for assessing the indoor air quality).
The results show that the three proposed hybrid ventilation strategies are able to minimize the cooling need to zero. They can also imply a drastic reduction of AHU heating power, compared with a mechanical ventilation system without heat recovery (or with low efficiency heat recovery). In addition, they significantly save the fan energy.
The only drawback of the proposed strategies is that they might increase the space heating demand. For instance, the first and second strategies save about 75% and 50% of AHU (air handling unit) fan energy; however, the space heating increases by about 4.2 and 2.2 kWh/m2a, respectively. The third strategy features as the best proposal because it saves around 68% of fan energy with less increase (1.3 kWh/m2a) in space heating demand. Moreover, it ensures higher thermal comfort and indoor air quality levels compared to the first and second proposals.
Registration, identification, and re-creation of an indoor occupant’s actions are challenges in the field of building energy performance. Commonly used measurement technologies are capable of capturing partial information regarding the occupants’ activity.
However, the combination of all existing inputs cannot grant access to a satisfying description of occupant behaviour that allows capturing profiles of occupants’ intentions and habits. It seems that there is a missing type of data that could be used as a connection platform for already existing inputs.
To connect existing data sets, there is a need to deploy a monitoring method that can identify particular individuals; however, it must do so while still providing a certain level of privacy among the monitored occupants. Fulfilment of these standards can be achieved through the use of the depth registration technique.
The entertainment industry popularized this registration technique, but this registration method has many other applications in the fields of medicine and computer vision. The most commonly used device (Microsoft Kinect) delivers high-frequency sampling (up to 30 Hz) and a moderate measurement range (up to 5 m), which allows its usage in the monitoring of medium-sized indoor spaces.
The delivered input data do not allow for the direct identification of the monitored person, and it does not require any interaction from the occupants to initialise the monitoring procedure. Due to these reasons, the potential of this measurement method was explored in terms of becoming an in situ indoor occupant behaviour monitoring technique.
This work introduces a generic methodology to determine the hourly average CO2eq. intensity of the electricity mix of a bidding zone.
The proposed method is based on the logic of input–output models and avails the balance between electricity generation and demand. The methodology also takes into account electricity trading between bidding zones and time-varying CO2eq. intensities of the electricity traded.
The paper shows that it is essential to take into account electricity imports and their varying CO2eq. intensities for the evaluation of the CO2eq. intensity in Scandinavian bidding zones. Generally, the average CO2eq. intensity of the Norwegian electricity mix increases during times of electricity imports since the average CO2eq. intensity is normally low because electricity is mainly generated from hydropower. Among other applications, the CO2eq. intensity can be used as a penalty signal in predictive controls of building energy systems since ENTSO-E provides 72 h forecasts of electricity generation.
Therefore, as a second contribution, the demand response potential for heating a single-family residential building based on the hourly average CO2eq. intensity of six Scandinavian bidding zones is investigated. Predictive rule-based controls are implemented into a building performance simulation tool (here IDA ICE) to study the influence that the daily fluctuations of the CO2eq. intensity signal have on the potential overall emission savings.
The results show that control strategies based on the CO2eq. intensity can achieve emission reductions, if daily fluctuations of the CO2eq. intensity are large enough to compensate for the increased electricity use due to load shifting. Furthermore, the results reveal that price-based control strategies usually lead to increased overall emissions for the Scandinavian bidding zones as the operation is shifted to nighttime, when cheap carbon-intensive electricity is imported from the continental European power grid.
A linear complementarity model is developed and presented for two different electricity market designs comprising an energy-only as well as a capacity market. In addition, storage units are implemented, assessing the impact of the market design on these units.
Results of a case study for northern Europe show that the availability of storage units can have a significant impact on the optimal generation mix to reduce the need for mid-merit and peaking thermal generation capacity. Given a capacity market, the derating of storage technologies creates a bias towards conventional thermal units and has a significant negative impact on the profitability and hence incentive to invest in energy storage units.
Furthermore, due to the vastly different cost characteristics and round-cycle efficiencies, it is found that batteries and pumped hydro energy storage complement each other in the power system instead of reducing each other’s business opportunities.
Long-term forecasts of the aggregate electric load profile are crucial for grid investment decisions and energy system planning. With current developments in energy efficiency of new and renovated buildings, and the coupling of heating and electricity demand through heat pumps, the long-term load forecast cannot be based on its historic pattern anymore.
This paper presents part of an on-going work aimed at improving forecasts of the electric load profile on a national level, based on a bottom-up approach. The proposed methodology allows to account for energy efficiency measures of buildings and introduction of heat pumps on the aggregated electric load profile. Based on monitored data from over 100 non-residential buildings from all over Norway, with hourly resolution, this paper presents panel data regression models for heat load and electric specific load separately. This distinction is crucial since it allows to consider future energy efficiency measures and substitution of heating technologies.
The data set is divided into 7 building types, with two variants: regular and energy efficient. The load is dependent on hour of the day, outer temperature and type of day, such as weekday and weekend. The resulting parameter estimates characterize the energy signature for each building type and variant, normalized per floor area unit (m2). Hence, it is possible to generate load profiles for typical days, weeks and years, and make aggregated load forecasts for a given area, needing only outdoor temperature and floor areas as additional data inputs.
The planning of energy ambitious neighborhood pilots in Norway typically begin with the creation of holistic and socially ambitious visions based on extensive stakeholder collaboration, citizen insight generation and vision setting. However, as projects move from planning to implementation, the exploratory innovation methods are replaced by exploitative approaches. ‘The holistic vision and in particular, citizens’ described needs, fail to transfer into the implementation phase.
This paper identifies four main challenges as to why this happens and link these to theory on ambidextrous organizations that need to exploit existing knowledge while reaching into the future with its rapidly changing goals and technological opportunities. Implementing stakeholders are familiar with exploitative tools, which build on earlier experience and capabilities of the selected implementing stakeholders, and the implementation stage leaves little time and resources for innovation on a lower hierarchical level.
While extensive research on smart and integrated planning focus on ‘breaking down the silos’ meaning sectors and disciplines, our findings argue that the need to manage ambidextrous organizations and support both exploratory and exploitative innovation is equally important. An ambidextrous organization is one that has the ability to be efficient in its management of today’s business while being adaptable for coping with the changing demand of tomorrow. We propose a model in which the organizational style and management style of innovative neighborhood pilots focus more on how to transfer knowledge and learn from the bottom-up and horizontally through management that foster both innovation models.
4th generation district heating represents the new generation of district heating systems. It reduces heat loss from the grid, enables better use of surplus heat and renewable energy sources, in addition to reducing the strain on the electricity grid. In short, 4th generation district heating is a sustainable solution for supplying heat to Zero Emission Neighbourhoods.
However, there are technical challenges that must be solved before it is introduced. One of them is to determine how low the supply temperature can be in different types of buildings so that we can identify the minimum district heating supply temperature. In our research, we evaluated the minimum supply temperature in Norwegian apartment blocks by improving the thermal envelope and reducing the temperature levels for the heating system. Our analysis focuses on whether the reduced supply temperature guarantees thermal comfort in the building.
Our project implied developing a database of building models representative of Norwegian apartment blocks. The building models consisted of eight age groups and three levels of energy performance. We performed simulations with two different temperature levels for the radiators typical for Norwegian buildings: 80/60 and 60/40 °C.
We found that reducing the supply temperature to the radiators from 80 to 60 °C is possible for buildings newer than from 1970, even for non-renovated buildings. For older buildings, an intermediate renovation, i.e. upgrading the windows, is necessary to maintain temperatures above the minimum acceptable temperature of 19 °C. Still, we highly recommend to perform a more ambitious renovation for these buildings to reduce the number of hours with significantly reduced indoor temperature compared to the setpoint temperature of 22 °C. In addition to reduce the heating demand and thus achieve energy savings, this will also ensure that the occupants are satisfied with their thermal environment.
The results can be used by district heating companies, building owners, contractors and consulting companies, in order to evaluate the introduction of 4th generation district heating in Norwegian apartment blocks. The models and Excel sheets with hourly results for energy need are available for partners and researchers within FME ZEN, so that they could be used for other purposes as well.
By Øystein Rønneseth
Buildings that are designed to meet high-energy performance requirements, e.g., passive houses, require well-insulated building envelopes, with increased insulation thicknesses for roof, wall and floor structures. We investigate whether there are differences in the efficiency of thermal insulation materials at different moisture levels in the insulation and if there is a larger or smaller risk of natural convection in wood-fibre based insulation than in mineral wool.
The work has mainly been performed by use of laboratory measurements included permeability properties and full-scale measurements of thermal transmittance of mineral wool and wood-fibre insulated constructions. In addition, calculations have been used to calculate resulting effects on the thermal performance of constructions. Results showed that the thermal conductivity was unaffected by moisture in the hygroscopic range. The air permeability was found to be approximately 50% higher for the wood-fibre insulation compared to mineral wool insulation. Measurements showed that the largest U-values and Nusselt numbers were found for the wall configuration. Calculation of the U-value of walls showed that in order to achieve the same U-value for the wood-fibre insulated wall as the mineral wool, it is necessary to add 20 mm insulation to the 250 mm wall and approximately 30 mm for the 400 mm wall.
This paper explores the most influential aspects regarding the environmental and economic performance of zero-energy and zero-emission buildings and proposes a pathway for transition in building solutions. A representative zero-energy office building in Norway is investigated with alternative design solutions to achieve zero-emission status i.e., the extensive use of locally generated energy through photovoltaic (PV) panels and the use of materials with low embodied emissions, such as low-carbon concrete and wood. A life cycle environmental and economic assessment is performed to evaluate specific indicators during the building life cycle: cumulative energy (CED), global warming potential (GWP), and equivalent annual cost (EAC).
The extensive use of PV panels was most effective in lowering the operational energy because it reduced the CED by about 30% compared to the building as-built. However, the extensive use of wood in the construction contributed the most to GWP reduction, with around 30% decrease compared to the building as-built. Finally, the differences in EAC were interestingly insignificant among the alternatives, with the investment costs dominating the EAC for all designs examined.
The findings of this paper emphasise that a full compensation of the life cycle GHG emissions from materials is difficult to achieve through renewable energy, even with extensive use of PV panels, especially in a low-carbon grid situation as in Norway. A pathway strategy from zero-energy towards zero-emission buildings must therefore strongly focus on the materials’ embodied energy and emissions because low operational energy demand is already a regulatory priority in most countries.
This article sets out to describe the role of aesthetics in citizen dialogues during the upgrading of a local swimming pool in Hammarkullen, Gothenburg. The swimming pool became an important project because of its role in a larger neighbourhood renovation project that allowed the municipality to focus on citizen engagement and inclusion. The engagement process showed the importance of the local swimming pool for a marginalized group of women of Somali origin, and a decision was made to keep the swimming pool instead of demolishing it. This led to collaboration between project coordinators, the Public Art Agency, an artist and an architect. Individual qualitative interviews focusing on storytelling were undertaken with key stakeholders.
The findings show that aesthetic quality mediated the communicative processes between project coordinators and citizens. Art in public space is more than just aesthetics or something to look at; art provokes a wide variety of responses and artists use a variety of means to engage with their public and creating dialogue. Yet the project managers failed to consider the creative process of the architect and her perspective on aesthetic quality and building functionality.
Stakeholders take different stances to whether aesthetic quality can be a way of grounding, communicating and evolving, or whether it is a matter of beauty where the artist or architect takes the lead. While the project coordinators affirm sameness, different understandings of aesthetic quality actively negotiate social differences. Inability to consider creative practices’ work processes in relation to citizen dialogue can result in conflicts between art, architecture and governance during the transformation of a neighbourhood.
The building energy flexibility potential of a Norwegian single-family detached house is investigated using predictive rule-based control (PRBC) and building performance simulation (using IDA ICE). Norwegian timber buildings are lightweight and four different insulation levels are considered. Both on-off and modulating air-source heat pumps are analyzed and compared to direct electric heating which is the most common heating system for Norwegian residential buildings. A detailed model for both the heat pump system and the building is implemented, a level of detail not found in previous research on building energy flexibility.
The three PRBC investigated have the following objectives: reduce energy costs for heating, reduce annual CO2eq. emissions and reduce energy use for heating during peak hours. This last objective is probably the most strategic in the Norwegian context where cheap electricity is mainly produced by hydropower. The results show that the price-based control does not generate cost savings because lower electricity prices are outweighed by the increase in electricity use for heating. The implemented price-based control would create cost savings in electricity markets with higher daily fluctuations in electricity prices, such as Denmark. For the same reasons, the carbon-based control cannot reduce the yearly CO2eq. emissions due to limited daily fluctuations in the average CO2eq. intensity of the Norwegian electricity mix. On the contrary, the PRBC that reduces the energy use for heating during peak hours turns out to be very efficient, especially for direct electric heating. For air-source heat pumps, the control of the heat pump system is complex and reduces the performance of the three PRBC.
Therefore, results suggest that a heat pump system should be modeled with enough detail for a proper assessment of the building energy flexibility. First, by varying temperature set-points there is a clear interaction between the prioritization of domestic hot water and the control of auxiliary heaters which increases energy use significantly. Second, the hysteresis of the heat pump control and the minimum cycle duration prevent the heat pump from stopping immediately after the PRBC requires it. Finally, the paper shows that the influence of thermal zoning, investigated here by cold bedrooms with closed doors, has a limited impact on the building energy flexibility potential and the risk of opening bedroom windows.
In the last decade, some of the warmest years on record have been experienced. Failure in climate change adaptation can lead to costly short- and long-term issues, such as blackouts due to energy supply disruption. These problems partly are arising from the fact that existing buildings are not designed for atypical conditions, and their expected performance is based on most-likely conditions. Building performance simulation (BPS) empowers designers to evaluate a proposed design under the probable climate conditions that a building will face during its lifetime. This work aims at answering the question: what type of future weather files enable building engineers and designers to more reliably test robustness of their designs against climate change.
Extreme weather files are needed for a robust design in building and urban scales
The standardized weather files of today are a single-year of typical weather data that represent typical regional climate conditions based on historical data. One of the main disadvantages of this method on climate change impact assessment is its averaging nature. The averaging process can result in missing extreme values and therefore shows how systems designed taking into consideration only typical conditions could quickly become a costly mistake (due to under-dimensioning).
This study provides an overview of the major approaches for creating future weather data sets. For the first time, the effects of using major available approaches for generating future weather files are studied on the calculation of energy performance of buildings. The building models were simulated in isolation and combined to create a virtual neighborhood.
The study investigates the possibility and importance of using extreme weather years in BPS at both the building and neighborhood scales. This will allow understanding the magnitude of the risk induced at large scale by not taking into account possible future climate extremes.
The analysis of the virtual neighborhood revealed that the peak electric power demand for the neighborhood can increase up to 16.8% under extreme conditions in comparison to the typical conditions. These results underline the importance of considering extreme conditions in studying the impacts of climate change on larger spatial scales (e.g. urban and city scales) and preparing urban energy systems for such future conditions.
In conclusion, our work provided further evidence that proper weather data sets based on high resolution data from climate models and several climate scenarios, including extreme conditions, are required to empower building engineers and architects to test their design solutions under future climate uncertainties.
By Amin Moazamia
Designing a zero emission neighborhood (ZEN) from an energy point of view, has the benefit of distributing loads over time by creating a mosaic of buildings which individually may not have a zero emission balance, but reach it as an ensemble. Responsive building envelopes (RBEs) are expected to play an important role in the design of ZENs and future smart sustainable cities. RBEs are useful to optimize the balance between several energy flows at single- and multi building scale, as well as to actively manage both on-site renewable- and purchased energy in addition to improving user experience and indoor comfort by providing an interactive interface with the outdoors.
This article provides a review of the potential and the requirements associated with using RBEs to manage complex interactions between buildings, clusters of buildings and utility grids. A six-step pathway for the implementation of RBEs in ZEN-like projects are proposed. The six steps are related to identifying; purpose of response, scale and interdependency, functionality, trigger and control, interactions and finally to identifying technical solutions. The proposed process emphasizes the importance of defining specific information such as the responsive goal hierarchies, the scale of the responses in relation to their purpose, and the importance of the aesthetic expression to foster positive user experience.
This article describes challenges that should be overcome towards implementation of low-temperature district heating (LTDH). The trends in development, operational issues, and legislative framework were revised.
The new substation design with solutions to avoid legionella bacteria issue, improved network topology and control strategies, opportunities of LTDH for buildings under various renovation stages and construction year were identified as the most crucial for the transition to 4th generation district heating (DH). Importance of heat load aggregation to avoid peak load issue in the areas with low-energy buildings (LEB) and solutions for transition from high temperature to low temperatures in the DH network have been shown
The findings indicate that there is a huge potential for achieving low-carbon society and improvement in energy efficiency under transition to LTDH. The solutions for transition from high-temperature DH to LTDH exist; however, they need good policies and market availability to be implemented.
The building industry is responsible for approximately 40% of energy consumption and 36% of greenhouse gas emissions in the European Union (EU). The most efficient way of reducing a building’s environmental impact is addressing it in the design stage. Here, design freedom is the greatest, but uncertainty is high and there is a nearly limitless number of design options.
Based on experiences with zero emission buildings (ZEB) and zero emission neighbourhoods (ZEN), a mapping review has been conducted to analyse how parametric life cycle assessment (LCA) and algorithms have been used to address neighbourhoods, buildings, and construction materials. Results have identified a general gap of knowledge regarding the use of parametric LCA models for decision-support purposes, demonstrated by the substantial focus on analytical methods compared to procedural methods. Implications for the evolution from ZEB to ZEN are twofold: (i) an integrated approach with multiple tools and methods is required, and (ii) further development of algorithms in the tool are needed to address complexity, sensitivity, and uncertainty.
This study is expected to foster the development of algorithmic approaches to improve the ZEB tool as a decision-support tool. Further research should address the key questions of when and how
The importance of embodied energy and embodied greenhouse gas emissions (EEG) from buildings is gaining increased interest within building sector initiatives and on a regulatory level. In spite of recent harmonisation efforts, reported results of EEG from building case studies display large variations in numerical results due to variations in the chosen indicators, data sources and both temporal and physical boundaries.
The aim of this paper is to add value to existing EEG research knowledge by systematically explaining and analysing the methodological implications of the quantitative results obtained, thus providing a framework for reinterpretation and more effective comparison. The collection of over 80 international case studies developed within the International Energy Agency’s EBC Annex 57 research programme is used as the quantitative foundation to present a comprehensive analysis of the multiple interacting methodological parameters. The analysis of methodological parameters is structured by the stepwise methodological choices made in the building EEG assessment practice. Each of six assessment process steps involves one or more methodological choices relevant to the EEG results, and the combination potentials between these many parameters signifies a multitude of ways in which the outcome of EEG studies are affected.
The dominance of operational energy and related greenhouse gas (GHG) emissions of most existing buildings is decreasing in new construction, when primary fossil energy of building operation decreases as result of the implementation of energy efficiency measures as well as a decarbonisation of national energy mixes. Stakeholders therefore have a growing interest in understanding the possibilities for reducing embodied impacts in buildings. In the IEA EBC project ‘Annex 57’ a broad call for case studies was launched with the aim to identify design strategies for reducing embodied energy and GHG emissions (EEG) from buildings.
The aim of this paper is to identify and provide a collected and comprehensive overview of quantitative reduction potentials of the particular EEG reduction strategies which should be considered by the stakeholders engaged in, and with the capacity to influence the outcome of, individual building projects. This is done by a systematic analysis of the Annex 57 case study collection as well as additional scientific literature. While it should be noted that the actual EEG savings at building level illustrated in this collection of studies are only applicable to each specific case, importantly this multiple cross-case analysis has provided rigorous evidence of the considerable potential to reduce embodied impacts in the design and construction of new and refurbished buildings.
The Trondheim Living Lab is a detached single-family zero emission building (ZEB) that is planned to reach a zero-emission balance over the course of its estimated 60-year lifetime. This is achieved by a broad variety of technical strategies such as passive and active energy design and efficient installations, as well as calculations of embodied emissions. In qualitative experiments conducted between September 2015 and April 2016 six different groups lived in the house for 25 days each. Based on direct observation (mainly through sensors registering temperature, humidity, CO2 levels and energy use), participant observation and interviews before, during and after the stay, the paper analyses the unfolding domestication of the building along three dimensions; practical, symbolic and cognitive.
The paper provides an account of which expected or unexpected occupant actions matter in which way for the zero emission ambitions of the building. Moreover, by studying the way in which the six groups within the three different categories student, family and elderly experienced living in this demonstration building this paper contributes a more detailed understanding of the overall acceptance of a ZEB in Norway.
In this study, the objective is to redesign a previous concept for a single-family Zero greenhouse gas Emission Building (ZEB). The concept is redesigned based on comparing greenhouse gas (GHG) emission loads and compensation from different design solutions applied in Norwegian single-family ZEB pilot buildings and selected sensitivity studies. The objective is to see if a previously developed ZEB model (2011) can be redesigned to achieve a life cycle energy and material emission balance (ZEB-OM), which previously was not achieved.
Five different design parameters are evaluated: area efficiency, embodied emissions in the envelope, insulation thickness, heating systems and different roof forms with respect to the photovoltaic area. Embodied emissions reductions were possible in the ground foundation, from around 1 kg CO2/m2 to 0.6 kg CO2/m2 per year. Both models are able to compensate for all operational emissions. The new model is in addition able to compensate for 60% of embodied emissions, whereas the previous model only could compensate for 5%. The new model does not reach the life cycle energy and material balance. The paper presents and discusses different approaches for achieving the ZEB-OM balance. Further concept model optimization is needed.
The large penetration rate of renewable energy sources leads to challenges in planning and controlling the energy production, transmission, and distribution in power systems. A potential solution is found in a paradigm shift from traditional supply control to demand control. To address such changes, a first step lays in a formal and robust characterization of the energy flexibility on the demand side. The most common way to characterize the energy flexibility is by considering it as a static function at every time instant. The validity of this approach is questionable because energy-based systems are never at steady-state. Therefore, in this paper, a novel methodology to characterize the energy flexibility as a dynamic function is proposed, which is titled as the Flexibility Function.
The Flexibility Function brings new possibilities for enabling the grid operators or other operators to control the demand through the use of penalty signals (e.g., price, CO2, etc.). For instance, CO2-based controllers can be used to accelerate the transition to a fossil-free society. Contrary to previous static approaches to quantify Energy Flexibility, the dynamic nature of the Flexibility Function enables a Flexibility Index, which describes to which extent a building is able to respond to the grid’s need for flexibility. In order to validate the proposed methodologies, a case study is presented, demonstrating how different Flexibility Functions enable the utilization of the flexibility in different types of buildings, which are integrated with renewable energies.
It has been proven that occupant behavior may significantly change building energy performance. The effect of the occupant behavior is becoming even bigger when it comes to highly energy efficient buildings. Specifically Zero Emission Buildings (ZEB) may become an issue for the electric grid, because they are supposed to be actively connected to the electricity grid for electricity import and export. Therefore, the aim of this study was to evaluate the change in the energy performance of a ZEB located in Norway.
Occupant behavior was modelled by using the following methods standard schedules, well-defined profiles based on thorough statistical analysis, and stochastic methods To analyze the grid stress, 31 scenarios for different occupant behaviors were analyzed. The overall estimation of investigated parameters showed that the change in occupant behavior resulted in grid stress variance from −5% to +13% compared to the reference case based on the standard values.
The results showed that the occupant behavior might change the annual energy balance reliability by 20%. However, the results showed that the influence of the occupant behavior related to the window opening and domestic hot tap water would not significantly change the ZEB energy performance. Window opening would even decrease the cooling load. A very important conclusion of this study is that consideration of occupant behavior through challenging the standard values are highly necessary for reliable energy analysis of the ZEB solutions.
The housing sector is important for future energy savings and greenhouse gas emission mitigation. A dynamic, stock-driven and segmented dwelling stock model is applied for dwelling stock energy analyses. Renovation activity is estimated as the need for renovation during the ageing process of the stock, in contrast to exogenously defined and often unrealistic renovation rates applied in other models.
The case study of Norway 2016–2050 shows that despite stock growth, the total theoretical estimated delivered energy is expected to decrease from 2016 to 2050 by 23% (baseline) and 52% (most optimistic scenario). A large share of the energy-efficiency potential of the stock is already realized through standard renovation. The potential for further reductions through more advanced and/or more frequent renovation, compared to current practice, is surprisingly limited. However, extensive use of heat pumps and photovoltaics will give large additional future energy savings. Finally, user behaviour is highly important. A strong future rebound effect is expected as the dwelling stock becomes more energy efficient. The estimated total ‘real’ energy demand is expected to decrease by only 1% (baseline) and 36% (most optimistic scenario). Hence, reaching significant future energy and emission reductions in the Norwegian dwelling stock system will be challenging.
This paper investigates how an extensive implementation of net Zero Energy Buildings (ZEBs) affects cost-optimal investments in the Scandinavian energy system towards 2050. Analyses are done by a stochastic TIMES model with an explicit representation of the short-term uncertainty related to electricity supply and heat demand in buildings. We define a nearly ZEB to be a highly efficient building with on-site PV production. To evaluate the flexibility requirement of the surrounding energy system, we consider no use of energy storage within the ZEBs.
The results show that ZEBs reduce the investments in non-flexible hydropower, wind power and Combined Heat and Power, and increase the use of direct electric heating and electric boilers. With building integrated PV production of 53 TWh in 2050, ZEBs increase the Scandinavian electricity generation by 16 TWh and increase the net electricity export by 19 TWh. Although the increased production reduces the electricity prices, the low heat demand in ZEBs gives a drop in the electricity consumption by 4 TWh in 2050. Finally, the results demonstrate that the Scandinavian energy system is capable of integrating a large amount of ZEBs with intermittent PV production due to the flexible hydropower in Norway and Sweden.
Generation of energy at building level has an increasing interest in Norway, as in rest of Europe. Load matching is the correlation between the buildings generation and load, which in most cases aims at optimization of the amount of self-consumption. When analysing generation in relation to load, it is of interest to study the choice of resolution and what impact this has on load match indicators. This study analyses the importance of choosing the right resolution, starting with hourly measurements, and going down towards one-minute resolution.
Monitoring resolution has a significant impact on both the type of monitoring equipment and the data storage capacity needed. If the impact of lower resolution is small, less complex monitoring systems can be installed in projects that are not sensible to the uncertainty caused by the lack of minute-based data.
Norwegian case studies with solar power production gives data to the analysis, studying a nursing home in Oslo called Økern Sykehjem. The nursing home has been a pilot building in the European Fp7 research project ZenN, Nearly Zero Energy Neighbourhood (2012-2017), which led to the installation of 130 kW solar power panels while going through a large renovation process. Generation and load have been monitored with high-resolution since 2015 and this gives useful insight into the effect of high-resolution data monitoring compared to hourly-resolution monitoring.
Resulting graphs shows that by collecting data on a daily basis will give a wrong impression on self-consumption and self-generation by about 20% compared to hourly based data. The difference between minute based and hourly based resolution is relatively small (6%).
The present study examines the effect of bulk density and cement content on the thermal conductivity of cement stabilized earth blocks (CSEB). The experimental results show that the thermal conductivity increases as a function of bulk density; changes in cement content result in a small variation in thermal conductivity of CSEB at a given bulk density. No obvious linear relationship between the thermal conductivity and cement content of CSEB has been observed. However, a significant increase of compressive strength of CSEB caused by the addition of cement has been observed; moreover, the compressive strength of CSEB increases with increasing cement content. CSEB show potential in earth buildings due to their improved compressive strength and reduced thermal conductivity.
ZEN pilot project Zero Village Bergen. ©Bergen Municipality