| 1. |
- Johari, Fatemeh, et al.
(författare)
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Towards Urban Building Energy Modelling: : A Comparison of Available Tools
- 2019
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Konferensbidrag (refereegranskat)abstract
- Along with sustainable urban development and energy efficien-cy initiatives, city-scale energy modelling of buildings has been receiving an increasing attention as a tool for planning and eval-uating future viable cities. However, due to the lack of software developed specifically for urban building energy modelling, computer-based modelling tools, previously applied for evalua-tion of the energy use and performance of single buildings, are widely utilized. The indoor climate and energy simulation tool IDA ICE, the transient system simulation software TRNSYS, and the building energy simulation programs EnergyPlus and VIP-Energy are some of the most commonly used examples of such tools. Although these simulation tools should in princi-ple be possible to use for large-scale applications, there is no comprehensive study that reflects on the modelling procedure, inputs, outputs and validity of these tools compare to each other.Thus, to investigate the capabilities of these tools for urban building energy simulations and to identify their advantages and disadvantages, in this study, a detailed energy model of a neighborhood including 32 district-heated buildings located in Sweden was developed in each tool. Hourly and annual simulation results were compared to each other and validated against thermal energy measurement data. The results of the study show that the simulated heat demand is a reasonable ap-proximation of the real one in all of the four tools. The annual deviation from the measured heat demand is +18 % for IDA ICE, +15 % for TRNSYS and about -13 % and -16 % for Ener-gyPlus and VIP-Energy, respectively. However, the simulatedresults from EnergyPlus, TRNSYS and VIP-Energy indicated higher correlations with the hourly measurements compared to IDA ICE. The findings of this study suggest that EnergyPlus and TRNSYS are the most applicable tools for use in UBEM.
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| 2. |
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| 3. |
- Monie, Svante, 1972-, et al.
(författare)
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A residential community-level virtual power plant to balance variable renewable power generation in Sweden
- 2020
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 228
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Tidskriftsartikel (refereegranskat)abstract
- Power systems with large shares of variable renewable electricity generation, i.e., wind and solar power, require high flexibility in both power generation and demand. Heat pumps and combined heat and power units within district heating systems and thermal storages have previously been studied for their potential to increase the flexibility of the energy system. When using these technologies for power balancing, they must be operated in a non-standard way with switched merit-order. This study hypothesizes that a residential area could form a locally operated entity, i.e., a virtual power plant, that provides power-balancing services to a national power system. The hypothesis is tested with a case study in Sweden where a combined heat and power unit, heat pumps, a local heat distribution system, and thermal storage constitute the local entity. A simulation of the energy balances in the system, with optimization of storage size, was performed. The results show that all power surpluses in the system are consumed by the heat pumps. 43% of the annual and 21% of the electricity peak load are covered by the combined heat and power unit. It is concluded that inter-seasonal thermal storage is crucial for the system’s flexibility. Also, large electricity surpluses, if converted to heat and stored, limit the ability of the virtual power plant to utilize the combined heat and power unit for power balancing at a later stage. Despite this, a local virtual power plant can provide increased flexibility by offering power-balancing services to the power system.
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| 4. |
- Monie, Svante, 1972-
(författare)
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Balancing variable renewable electricity generation using combined heat and power plants, large-scale heat pumps, and thermal energy storages in Swedish district heating systems
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The global ambitions to hamper the greenhouse effect has led to ambitious targets for increasing renewable energy use. This, in combination with recent years' vast development of wind and solar power, implies that there will be significant amounts of variable renewable electricity (VRE) in future energy systems. With the inherent variability in VRE production comes a need for increased contingency in power systems. This requires both controllable production and consumption of power to cope with VRE deficits and surpluses. The purpose of this doctoral thesis is to investigate the potential for providing such power balancing services from Swedish district heating systems (DHS). Analyses are made for different system levels: community, regional, and national. Computer simulations of DH production systems with combined heat and power (CHP) plants, heat pumps, and thermal energy storage (TES), operated to supply a power balancing demand, are here shown to potentially reduce VRE deficits and surpluses. The results further show that reducing peak deficits and/or surpluses mainly depends on the installed capacities in CHP units and/or heat pumps. However, annual deficits or surpluses are reduced more if the system includes a TES. Also, the shares of wind and solar power in VRE mixes are shown to be relevant for fuel use and system performance. Solar-dominated VRE promotes heat pumps, reduces fuel use in CHP, and motivates a seasonal operation of TESs. Wind-dominated VRE matches with high capacities in CHP units, yields increased fuel use and motivates short-term operation of TESs. A crucial limitation is competition for the heat load between heat pumps and CHP units, which reduces the potential for CHP production. Competition between stored heat and heat pumps also occurs in systems with smaller TESs and large amounts of surplus electricity. In order for power balancing services to be economically viable for DHS operators, changed market structures that appropriately value the delivered services are likely required. The overall conclusions are: DHSs can offer power balancing, a high share of PV is essential to reduce fuel use, and finally, seasonal TESs are needed to cope with large amounts of surplus heat and/or replacement of peak load units.
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| 5. |
- Monie, Svante, 1972-, et al.
(författare)
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Comparing electricity balancing capacity, emissions, and cost for three different storage-based local energy systems
- 2020
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Ingår i: IET Renewable Power Generation. - : Institution of Engineering and Technology (IET). - 1752-1416 .- 1752-1424. ; 14:19, s. 3936-3945
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Tidskriftsartikel (refereegranskat)abstract
- This study provides an analysis of the potential for a sub-energy system to provide an electricity balancing service to, in this case, a national energy system with a large share of variable renewable electricity generation. By comparing electricity balancing capacity, CO2, eq-emissions, and costs, three different local residential energy system setups are assessed. The setups contain different combinations of district heating, combined heat and power, thermal energy storage, electric battery storage, heat pumps, and electric boilers. The analysis focuses on system-level integration, heat and electricity cross-sectoral operations, and unconventional production strategies for district heating production. The results show that local sub-energy systems with heat pumps, combined heat and power, and thermal energy storage has the potential to reduce national electricity balancing demand in an economically feasible way, and with modest CO2, eq-emissions. It was also shown that electricity-based heat production without district heating is economically unfavourable, even in the most optimistic scenario; it is not likely to be feasible within a 30-year period.
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| 6. |
- Monie, Svante, 1972-, et al.
(författare)
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Electricity balancing capacity, emissions, and cost comparison of three storage-based local energy systems for variable power generation
- 2019
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Ingår i: 9th International Workshop on Integration of Solar Power and Storage into Power Systems.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This study compares three energy system setups for supplying the electricity and heat demand in a residential area. Two of the setups contain district heating and a combined heat and power unit. The first setup contains a thermal storage and the second contains an electric battery. The third setup is all electric (incl. the heat production). The second setup reduced the electricity balancing demand the most, but had the highest CO2,eq-emissions. The third setup had no emissions, but the highest cost. This setup also increased the balancing demand. The first system, with the thermal storage, performed most satisfying when electricity balancing capacity, CO2,eq-emissions, and costs were weighed together.
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| 7. |
- Monie, Svante, 1972-, et al.
(författare)
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Thermal Energy Storages in Residential Areas : – a potential to increase renewable power generation?
- 2018
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Ingår i: 2018 ACEEE Summer Study on Energy Efficiency in Buildings. - Washington D.C.. ; , s. 11-1-11-12
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Konferensbidrag (refereegranskat)abstract
- With an increased ambition of implementing renewable electricity production in our energy systems follows the need of handling the inherent variability from some of these production sources (e.g. wind and solar). This could be via curtailments, infrastructural reinforcements of the power grid, and/or increased utilization of power system reserves. The aim of this study was to investigate if power surplus and deficit due to mismatch between intermittent power generation and power demand could be reduced with electric heat pumps (used for power-to-heat purposes), combined heat and power (CHP) production (for power balancing), and seasonal thermal energy storage (STES) (as buffering capacity). A residential area consisting of buildings refurbished for improved energy performance, roof top solar photovoltaic (PV) systems, a local heat distribution system, a small-scale CHP plant, central heat pumps, and a STES, was simulated. The heat pumps were given priority to use surplus power from roof top PV generation or surplus from the grid (e.g. wind power). The CHP plant produced power during power deficits. Surplus heat from the CHP plant as well as from the heat pumps was stored in the STES. The results showed a reduction of the surplus power from the local PV systems towards the upstream power grid. Also, the possibility to offer regulative service towards upstream power grid by using CHP was demonstrated. The conclusion is that power-to-heat and CHP can significantly reduce the mismatch between variable power generation and power demand.
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| 8. |
- Nilsson, Annica M., 1981-
(författare)
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Daylighting Systems : Development of Techniques for Optical Characterization and Performance Evaluation
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Successful integration of daylighting systems requires the ability to predict their performance for given climates. In this dissertation, a bottom-up approach is applied to evaluate the optical performance of a selection of daylighting systems. The evaluations are based on the optical properties of the included materials, and part of the dissertation focuses on developing new optical characterization methods.The work on characterization techniques uses an integrating sphere method to characterize the transmittance of light scattering samples more accurately. The method's principle is to reduce the discrepancy in light distribution between the reference and the sample scans by using an entry port beam diffuser. For samples exhibiting distinct light scattering patterns, the benefits of improved uniformity outweigh the errors introduced by the diffusing material. The method is applicable to any integrating sphere instrument, and its simplicity makes it suitable for standard measurements.In addition to normal-hemispherical properties, many daylighting applications require knowledge of the system's spatial light distribution. This dissertation presents a method combining experimental techniques and ray tracing simulations to assess the light distribution from a Venetian blind system. The method indicates that ray tracing based on simplified optical data is inadequate to predict the light distribution for slat materials exhibiting both specular and diffuse properties.Ray tracing is a promising complement to experimental methods used to characterize light guiding or light redirecting systems. Here, spectrophotometric measurements of a scaled mirror light pipe validate a ray tracing model. The model shows excellent agreement with experimental results for both direct and diffuse incident light. The spectral evaluation shows no dramatic color changes for the transmitted light. The ray tracing model is used to evaluate four daylighting systems for a selection of Swedish locations. The percentage of occupied time when the studied systems achieve full design illuminance is relatively low, but the systems provide a valuable contribution to the required illuminance.Additionally, this dissertation provides an overview of available energy efficient windows and illustrates the importance of including the solar energy transmittance when evaluating window energy performance.Overall, this dissertation presents optical characterization techniques for improved performance evaluations of daylighting systems.
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| 9. |
- Nilsson, Annica M., 1981-, et al.
(författare)
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Optical and thermal properties of functional coatings for future high performance windows
- 2008
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Konferensbidrag (refereegranskat)abstract
- With modern society facing the task of reducing energy consumption in all areas of life, modern windows provide an enormous potential to reduce energy consumption for the heating, cooling and lighting of buildings. For future buildings and for the retrofitting of older buildings the window is more and more becoming an integral part of the building’s energy system. In this paper we present the optical properties for a selection of different window coatings and discuss their impact on the performance of the window. Special emphasis is put on switchable glazing. Optimum performance for switchable glazing is often a trade off between minimum energy consumption for cooling heating and lighting. This can sometimes be in conflict with occupancy preferences. As an example we show how different control strategies for electrochromic windows can influence the energy balance of the window, and that small variations in the control algorithm can lead to improvements. The results were obtained by using the WinSel window simulation tool.
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| 10. |
- Nilsson, Annica, 1981-
(författare)
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Optical and thermal properties of functional coatings on glass and plastics for energy efficient windows and daylighting
- 2008
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Konferensbidrag (refereegranskat)abstract
- Over the past couple of decades a number of coated glazing products have appeared on the market, converting the window from an energy drain to a possible resource in the building’s energy supply system. In this paper the light transmittance, total solar transmittance, and thermal conductivity of coated glazing currently available on the market and of future dynamic electrochromic coatings are reviewed and their function in heating or cooling dominated climates discussed. Electrochromic coatings can switch between a transparent state and an absorbing or reflecting state when a small electrical potential is applied, and hence adapt their optical properties to the present condition. Energy balance calculations for the window component stress the importance of selecting the window depending on climate. In a heating dominated climate a low-e coating with a high g-value can result in a net energy gain on a south facing façade and thus be better than an ideal wall.
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