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PhD Thesis,
NTNU, Trondheim,

The transition to a sustainable energy system requires a shift to intermittent renewable
energy sources, which call for increased flexibility on the demand side. Heat pumps
offer the possibility to couple the electricity sector and the heating sector, and when
connected to thermal energy storages, they can provide demand side flexibility.
This thesis investigates the flexibility potential of residential buildings in
Scandinavia, and more specifically in Norway. In this regard, three different
boundary levels are considered: power grid level, building level, and heat pump
system level.
At the power grid level, a methodology to evaluate the hourly average CO2eq. intensity
of the electricity mix, while also considering electricity trading is developed. In
general, the CO2eq. intensity of the electricity mix may indicate the share of renewable
energies in the mix. The proposed method is based on the logic of input-output
models and avails the balance between electricity generation and demand. This thesis
shows that it is essential to consider 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 usually is low
because electricity is mainly generated from hydropower. This hourly CO2eq. intensity
can be used as a penalty signal for demand response strategies applied to residential
heating.
At the building level, the flexibility potential of predictive rule-based controls
(PRBC) in the context of Scandinavia and Norway is studied. For this purpose,
demand response measures are applied to electricity-based heating systems, such as
heat pumps and direct electric heating. In one case study, 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. 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.
In another case study, the building energy flexibility potential of a Norwegian singlefamily
detached house is investigated using PRBC. Four insulation levels are studied
for this building: (1) passive house, based on the Norwegian standard for residential
passive houses, (2) zero emission building, based on the LivingLab located at the
Gløshaugen Campus at NTNU, (3) TEK10, based on the Norwegian building
standard from 2010, and (4) TEK87, based on the Norwegian building standard from
1987. The three PRBC investigated aim at reducing energy costs for heating, reducing
annual CO2eq. emissions and reducing the 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. It is shown 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. The PRBC that reduces the
energy use for heating during peak hours turns out to be very efficient, especially for
direct electric heating. As an example, for the ZEB insulation level and direct electric
heating, the price-based control reduces the energy use during peak hours by 18%,
and the carbon-based control by about 37%. The control strategy dedicated to reduce
the energy use during peak hours leads to a 93% reduction. For air-source heat pumps,
the control of the heat pump system is complex and reduces the performance of the
three PRBC. Therefore, it is suggested to model a heat pump system with enough
detail for a proper assessment of the building energy flexibility.
The model complexity required to adequately describe the heat pump system
behavior with regards to demand response of residential heating is investigated on
the heat pump system level. In the course of this thesis, the influence of the modeling
complexity of the heat pump system control on distinct energy-related and heat pump
system-related performance indicators is studied. The results prove that the modeling
complexity of the system control has a significant impact on the key performance
indicators, meaning that this aspect should not be overlooked. If the heat pump
operation is investigated in detail and a high time resolution is required, it is shown
that a PI-controller leads to a smoother operation than a P-controller, but tuning of
the controller is highly recommended. It is shown that the choice of the controller (P
or PI) is not crucial as long as the control signal to the heat pump is not of importance
and power is not investigated at very short time scales. Regarding demand response
measures, a strong interaction between the prioritization of domestic hot water and
the control of auxiliary heaters significantly increases electricity use of a bivalent
mono-energetic heat pump system, if demand response is performed for both,
domestic hot water and space heating. The electricity use for heating is only slightly
increased if demand control using predictive rule-based control is performed for
space heating only.
To summarize, energy flexible buildings can play a major role in the transition
towards a more sustainable energy system. The use of the hourly CO2eq. intensity as
a penalty signal for demand response strategies applied to residential heating, can
facilitate achieving the emission targets of the European Union. At the building level,
different objectives of demand response, such as reducing operational costs, reducing
CO2 emissions or increasing system efficiency are often incompatible and thus
difficult to achieve at the same time when using PRBC. When aiming at a realistic
control of the heating system of a single building, it is found that heat pump controller
tuning and DHW prioritization of the heat pump are two significant aspects that
should be considered regardless of the control strategy applied. The combination of
heating system, heat distribution system, system control and building envelope is
always case-specific and it is suggested that future work focuses on the design of a
heat pump system that considers energy flexibility. In this PhD thesis, standard sizing
of a heat pump system that is operated in an energy flexible way is applied.
Keywords
Energy flexibility; hourly CO2eq. intensity; demand response; demand side flexibility;
predictive control; rule-based control; heat pump system; heat pump modeling; model
complexity; direct electric heating; time-varying CO2eq. intensities; time varying
electricity prices; Scandinavian power market


Master Thesis,
NTNU, Trondheim,

The paper aims to investigate how a net zero energy building could be optimised in order to shift to net zero emission building by balancing greenhouse gas (GHG) emissions from the operational energy use and materials embodied emissions with those from onsite renewable energy in the tropical rainforest climate of Singapore.
The first net Zero Energy Building in Singapore, SDE4, is taken as the case study. Guided by Norwegian ZEB guideline, the principles of the Life cycle assessment (LCA) methodology are used to calculate the total GHG emissions profile of the case study, which focuses on operational emissions and materials embodied emissions. The system boundary for LCA includes the embodied emissions from materials for the transport of materials (A4) and replacement (B4) of new materials in addition to the production stage (A1-A3). These calculations provide an overview of the emissions profile of the Singaporean net zero energy building is provided, outlining the need to address the high embodied emissions. More importantly, the main emissions drivers, concrete and steel, are revealed from the results.
Based on the results, potential emissions reduction measures are discussed, and an emission-reduced scenario is proposed and calculated to demonstrate the improvement. The final result showed that, for the case study, on-site renewable energy generation could compensate for the operational emissions and materials embodied emissions if sufficient emissions reduction strategies have been adopted. In conclusion, the net zero energy building is possible to be shifted into net zero or low emission building with the implementation of emission-reducing design strategy, despite the rather challenging climate and situation in Singapore.


Master Thesis,
NTNU, Trondheim,

Bygg representerer en vesentlig faktor i en framtid med lave utslipp av drivhusgasser. En betydelig konsekvens av deres lange livsløp gjør at det haster å innføre standarder med toppmoderne prestasjoner for å unngå betydelig låsningsrisiko. Hittil har Livssyklusanalysestudier (LCA) betraktet bygg, mobilitet og energisystemer hver for seg. Nullutslippsnabolag (ZEN) gir en unik mulighet til å kombinere disse elementene, og dermed bidra til å begrense klimaendringene. I Norge har forskningssenteret på ZEN i smart byer (https://fmezen.no/) et mål om å tilrettelegge for overgangen til lavkarbonsamfunn ved å utvikle bærekraftige nabolag med null drivhusgassutslipp.

I dette studiet blir det brukt en LCA modell for nabolag som er basert på en modul struktur bestående av fem fysiske elementer; bygg, mobilitet, infrastruktur, nettverk og on-site energiinfrastruktur på Ydalir, et av ZEN senterets pilotprosjekter. Den gjennomførte LCAen viser at uansett hvilket scenario som blir vurdert, klarer ikke ZEN Ydalir innenfor nåværende plan å nå deres ambisiøse mål om null utslipp. Til tross for dette, representerer nabolagets resultater et viktig steg mot et nullutslippssamfunn, og påpeker flere vesentlige tiltak for forbedringer mot målet om nullutslippsnabolag. Resultatene viser at bruksfasen i mobilitet er kilden til en betydelig andel av de totale drivhusgassene fra nabolaget, og representerer 42-46% av de totale utslippene. Når kun livssyklussteget materialer er tatt i betraktning, er bygg og mobilitet kildene til henholdsvis 37% og 38% av drivhusgassene, i begge scenariene. Dette tydeliggjør bruksfasen til mobilitet og materialstegene til bygg og mobilitet som de beste områdene for forbedring.

Modellen og dataen som er benyttet i dette arbeidet har flere usikkerhetsfaktorer. Parametere som er antatt å være knyttet til høy usikkerhet eller som er store bidragsytere til miljøpåvirkningen, er inkludert i en sensitivitetsanalyse og er kalkulert og diskutert. Scenarier basert på tiltak for å oppnå nullutslipp er også analysert og diskutert.

Buildings represent a critical piece of a low-carbon future and their long lifetime necessitates urgent adoption of state-of-the-art performance standards to avoid significant lock-in risk. So far, Life Cycle Analysis (LCA) studies have assessed buildings, mobility and energy systems mainly individually. Zero Emission Neighbourhoods (ZEN) gives a unique chance to combine these elements and thereby contribute to climate change mitigation. In Norway, the Research Centre on ZEN in Smart Cities (https://fmezen.no/) has a goal to enable the transition to a low carbon society by developing sustainable neighbourhoods with zero Greenhouse Gas (GHG) emissions.

In this study, it was applied an LCA model for neighbourhoods based on a modular structure with five physical elements; buildings, mobility, infrastructure, networks and on-site energy infrastructure on Ydalir, a pilot project of the ZEN Centre. The performed LCA revealed that regardless of which scenario considered, the ZEN Ydalir does not manage to achieve their ambitious goal of zero emissions with the present plan. However, the neighbourhood’s results represent an important step towards a zero emission society, highlighting several crucial measures for further improvement in the field of ZENs. The results further show that the operation of mobility is the source of a major part of the GHG emissions, accounting for 42-46% of the total. When considering the life cycle stage materials, the buildings and mobility represent 37% and 38% respectively of the GHG emissions from materials in both scenarios. Thus, operation stage of mobility and the material stage of the buildings and mobility have been highlighted as the best options for improvement.

The model and data used in this work is associated with several uncertainty factors. Parameters assumed to have significant uncertainties, or are large contributors to the environmental impact, are included in a sensitivity analysis and have been calculated and discussed. Scenarios based on different measures to achieve zero emissions have also been analysed and discussed.


Master Thesis,
NTNU, Trondheim,

Denne oppgaven følger Design Science Research metoden og utforsker hvordan virtuell virkelighet-teknologier (VR) kan bli benyttet for å visualisere utslipps-data i nullutslippsområder. For å oppnå dette ble en virtuell virkelighet-applikasjon, kalt ZENVR, utviklet. Denne ble evaluert gjennom semi-strukturerte ekspert-intervjuer. De innsamlede dataene ble strukturert og analysert ved å delvis anvende prinsippene fra Grounded Theory. Systemets brukervennlighet ble evaluert gjennom brukertester med et tilhørende spørreskjema.

Resultatene indikerer at virtuell virkelighet er en egnet plattform for å kommunisere og gi kontekst til komplekse data, og at ZENVR er et egnet verktøy for å visualisere Key Performance Indicators (KPIs) i nullutslippsområder. Resultatene viser også at ved å utnytte de altoppslukende egenskapene til virtuel virkelighet er det mulig å skape en opplevelse for brukeren som kan gjøre et vedvarende inntrykk. Flere bruksområder for ZENVR har blitt oppdaget: Engasjere innbyggere, promotering og reklame for nullutslippsområder, verktøy for tverrfaglig kommunikasjon og samarbeid mellom profesjonnelle.

This project follows the Design Science Research methodology and explores how virtual reality technology may be utilized for visualizing emission data in Zero Emission Neighbourhoods (ZENs). The project involved developing a virtual reality application named ZENVR, which were evaluated through semi-structured expert interviews. The data collected was structured and analyzed by partially applying Grounded Theory. Furthermore, the usability of the system has been evaluated through user test with an attached questionnaire.

The results indicate that virtual reality is a suitable platform for communicating and contextualizing complex data and that ZENVR is an appropriate tool for visualizing Key Performance Indicators in ZENs. The findings also show that by utilizing the immersive properties of virtual reality, it is possible to create an experience for the user and subsequently making a lasting impression. Several areas of use for ZENVR were discovered, including citizen engagement, promotion and the advertisement of ZENs, tool for interdisciplinary communication and collaboration between professionals.


Master Thesis,
NTNU, Trondheim,

Nå som mesteparten av verdens befolkning bor i byer, er forståelsen av byene sine systemer stadig viktigere. I dette prosjektet utviklet forfatteren et modulært agentbasert system for modellering av byer som komplekse systemer. Modellen ble validert ved å kjøre tester og eksperimenter som viste bruken av modellen som et hjelpemiddel for å forstå trafikkmønstrene i en by. Forsøkene var simuleringsløp som hadde forskjellige verdier for priser for busser og biler, variasjoner på inngangssteder til byen og varierende mengder parkeringsplasser. Systemet vil bli videreutviklet som en annen masteroppgave der fokuset vil være på elnettet og samspillet med andre systemer i byen. Det blir lagt fram et argument for fordelene med å bruke modulære og gjenbrukbare systemer i dette feltet.

With most of the world population living in cities, the understanding of these systems is increasingly important. In this project the author developed a modular agent-based system for modeling cities as complex systems. The model was validated by running tests and experiments that demonstrated its uses as an aid in understanding the emergent traffic patterns in a city. The experiments were simulation runs that had differing values for prices for buses and cars, variations on points of entry to the city, and varying amounts of parking spaces. The system will be further developed as another master’s thesis where the focus will be on the electrical grid and its mutual interaction with other systems in the city. An argument is made for the benefits of using modular and reusable systems in this field.


Master Thesis,
NTNU, Trondheim,

The bottom-up approach model developed earlier by Næss et al. (2018) is extended to include the dynamic material flow and embodied emissions from materials during con- struction, renovation and demolition activities of a neighbourhood in time. The model is then applied to the ZEN pilot project Ydalir in order to estimate the material flows and the associated embodied emissions of the building stock of the neighbourhood for a 60 years timeframe.
In order to achieve that, the model is made up of three parts that consist of: (i) sim- ulating the long-term building stock of the neighbourhood and identifying construction, renovation and demolition over time, (ii) setting up the material inventories that charac- terize the building stock and determining the emission intensities of those materials, (iii) combining (i) and (ii) to calculate the dynamic material use and embodied emissions for the neighbourhood over time. The neighbourhood is characterized by 15 initial individual archetypes according to type of building, renovation stage and cohort.
The dynamic model of Ydalir indicates that construction and renovation activities mobilize a total of 116 kton of materials with 82.6 kton CO2-eq of embodied emissions between 2019 and 2080. Initial construction being the activity that drives most use of materials and embodied emissions. The major source of embodied emissions are the PV panels that are part of the energy system in the residential buildings, this is due to the high carbon intensity of the system but also its need to be replaced every 30 years. Wood is the second most used material in the neighbourhood, as well as the second most accountable for the neighbourhood’s embodied emissions. In terms of material flow, concrete is the dominant material, more than half of the material input to the neighbourhood is concrete.
The sensitivity analysis suggests that variations in renovation rates, material invento- ries and emission intensities of materials have an effect in the total embodied emissions, with room to reduce embodied emissions. Additionally, the material specifications and emission intensities that are selected in the material categories of concrete, wood, glass and membrane can have a greater impact in the total embodied emissions for the case of Ydalir.
The model is robust because its methodology is thorough, transparent and detailed, yet, the assumptions made and lack of knowledge about the future limit the certainty and accuracy of of the results for Ydalir. Nevertheless, some strategies related to embodied emissions and material flow of the building stock of a neighbourhoods are identified. For instance, using threshold values for the embodied emission intensity of the building stock of a neighbourhood could be implemented as a guideline to design the neighbourhood and control the embodied emissions from the building stock.


Master Thesis,
NTNU, Trondheim,

Building, transportation, and human activities are main sources to generate greenhouse gas (GHG) emissions in neighbourhood. In order to reduce GHG emissions in neighbourhoods, architects plays an important role particularly in the early design phase since this is when the architect has the greatest opportunity to make design decisions that directly lead to a reduction in the GHG associated with the consumption of energy and embodied emissions of materials used in zero emission neighbourhoods. However, it is not easy for architects to easily understand and visualise how their design contributes to the overall GHG emissions for the neighbourhood since the origin of the emission is out of architectural scope. Thus, this thesis develops a tool visualizing the relationship between the neighbourhood design and GHG emissions, which can be easily utilized by architects.
This thesis is aligned with the Research centre on Zero Emission Neighbourhoods in Smart Cities (FME-ZEN). A ZEN is defined as a group of interconnected buildings with associated infrastructure, located within a confined geographical area, aiming at reducing its direct and indirect greenhouse gas (GHG) emissions towards zero. Life cycle assessment (LCA) is used to estimate the potential environmental impacts of a product or service system throughout its life cycle. The methodology was initially developed and used for zero emission buildings and has now been expanded to include zero emission neighbourhoods (ZENs).
The FME-ZEN research centre has already developed a set of ZEN assessment criteria and key performance indicators (KPIs) that can quantify and qualify neighbourhood performance. This work defined the new criteria and indicators based on KPIs of ZEN and other assessment tools in order to apply to the visual tool developed in this work.
The main objective of this thesis is to develop a conceptual visual tool and User Interface which enable architects to holistically integrate quantitative and qualitative assessments of GHG emissions in the decision-making process considering neighbourhood-oriented designs based on the ZEN KPIs. The visual tool was developed in main two platforms (small-neighbourhood platform and large-neighbourhood platform). The small-neighbourhood platform visualises building energy performance and the GHG emissions as a quantitative assessment tool while the large-neighbourhood platform displays urban information related with the emissions as a qualitative assessment tool. The platforms of this thesis as a conceptual assessment tool do not develop the actual interconnection with the computing tools for the GHG emission assessment. However, as one of the contributions of this thesis, proper tools and database are selected and their detailed connection plan is established for practical use of the dashboard in near future.
Through the case study of Nidarvoll Skole in Trondheim region of Norway, this thesis shows how the new school design is associated with GHG emissions and how the relationships can be effectively visualised to help the decision-making process for architectural design toward zero-emission neighbourhoods. By using the visual tool developed in this thesis, the most environmentally friendly design option was able to be selected, which delivers less energy consumption and CO2 emission, compared to the original school design. The savings in the two KPIs reached to 20,508 kWh/yr and 1,871 kgCO2eq/yr respectively, compared to other design options.