| 1. |
- 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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| 2. |
- 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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| 3. |
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| 4. |
- 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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| 5. |
- 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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| 6. |
- Åberg, Magnus, 1980-, et al.
(författare)
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Can electricity market prices control power-to-heat production for peak shaving of renewable power generation? : The case of Sweden
- 2019
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Ingår i: Energy. - : Elsevier Ltd. - 0360-5442 .- 1873-6785. ; 176, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- 100% renewable energy systems require high penetration of variable renewable electricity (VRE) generation. This causes the net load in the system to be more variable and could cause operational problems in local power grids. Demand side management (DSM), such as fuel or energy carrier switching in response to a price signal, can provide flexibility to meet the increased variability. This study investigates the impact of VRE production on electricity prices and their potential to act as an incentive to control district heating power-to-heat (P2H) production in order to shave VRE production peaks. Also, the potential to increase P2H production flexibility with additional heat storages is studied. Electricity prices are simulated by modification of historical electricity market supply curves. A heat storage component is implemented in an existing model for district heat production. The results show that P2H production is significantly increased (up to 98%) when electricity prices are influenced by VRE production. Thermal storages further increase the P2H production by up to 46%. The increased P2H production, however, does not necessarily coincide with the peaks of VRE. Thus, in conclusion, the pricing mechanism on the Nord pool electricity market is insufficient to control P2H production for shaving VRE production peaks.
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| 7. |
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| 8. |
- Alm, Erik, 1980-, et al.
(författare)
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A solution to the 1D NMR alignment problem using an extended generalized fuzzy Hough transform and mode support
- 2009
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 395:1, s. 213-223
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Tidskriftsartikel (refereegranskat)abstract
- This paper approaches the problem of intersample peak correspondence in the context of later applying statistical data analysis techniques to 1D 1H-nuclear magnetic resonance (NMR) data. Any data analysis methodology will fail to produce meaningful results if the analyzed data table is not synchronized, i.e., each analyzed variable frequency (Hz) does not originate from the same chemical source throughout the entire dataset. This is typically the case when dealing with NMR data from biological samples. In this paper, we present a new state of the art for solving this problem using the generalized fuzzy Hough transform (GFHT). This paper describes significant improvements since the method was introduced for NMR datasets of plasma in Csenki et al. (Anal Bioanal Chem 389:875-885, 15) and is now capable of synchronizing peaks from more complex datasets such as urine as well as plasma data. We present a novel way of globally modeling peak shifts using principal component analysis, a new algorithm for calculating the transform and an effective peak detection algorithm. The algorithm is applied to two real metabonomic 1H-NMR datasets and the properties of the method are compared to bucketing. We implicitly prove that GFHT establishes the objectively true correspondence. Desirable features of the GFHT are: (1) intersample peak correspondence even if peaks change order on the frequency axis and (2) the method is symmetric with respect to the samples.
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| 9. |
- Alm, Erik, 1980-, et al.
(författare)
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Automated annotation and quantification of metabolites in (1)H NMR data of biological origin
- 2012
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 403:2, s. 443-455
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Tidskriftsartikel (refereegranskat)abstract
- In 1H NMR metabolomic datasets, there are often over a thousand peaks per spectrum, many of which change position drastically between samples. Automatic alignment, annotation, and quantification of all the metabolites of interest in such datasets have not been feasible. In this work we propose a fully automated annotation and quantification procedure which requires annotation of metabolites only in a single spectrum. The reference database built from that single spectrum can be used for any number of 1H NMR datasets with a similar matrix. The procedure is based on the generalized fuzzy Hough transform (GFHT) for alignment and on Principal-components analysis (PCA) for peak selection and quantification. We show that we can establish quantities of 21 metabolites in several 1H NMR datasets and that the procedure is extendable to include any number of metabolites that can be identified in a single spectrum. The procedure speeds up the quantification of previously known metabolites and also returns a table containing the intensities and locations of all the peaks that were found and aligned but not assigned to a known metabolite. This enables both biopattern analysis of known metabolites and data mining for new potential biomarkers among the unknowns.
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| 10. |
- Alm, Erik, 1980-
(författare)
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Solving the correspondence problem in analytical chemistry : Automated methods for alignment and quantification of multiple signals
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- When applying statistical data analysis techniques to analytical chemical data, all variables must have correspondence over the samples dimension in order for the analysis to generate meaningful results. Peak shifts in NMR and chromatography destroys that correspondence and creates data matrices that have to be aligned before analysis. In this thesis, new methods are introduced that allow for automated transformation from unaligned raw data to aligned data matrices where each column corresponds to a unique signal. These methods are based around linear multivariate models for the peak shifts and Hough transform for establishing the parameters of these linear models. Methods for quantification under difficult conditions, such as crowded spectral regions, noisy data and unknown peak identities are also introduced. These methods include automated peak selection and a robust method for background subtraction. This thesis focuses on the processing of the data; the experimental work is secondary and is not discussed in great detail. All the developed methods are put together in a full procedure that takes us from raw data to a table of concentrations in a matter of minutes. The procedure is applied to 1H-NMR data from biological samples, which is one of the toughest alignment tasks available in the field of analytical chemistry. It is shown that the procedure performs consistently on the same level as much more labor intensive manual techniques such as Chenomx NMRSuite spectral profiling. Several kinds of datasets are evaluated using the procedure. Most of the data is from the field of Metabolomics, where the goal is to establish concentrations of as many small molecules as possible in biological samples.
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