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  • 1. Beckman, William A
    et al.
    Broman, Lars
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Fiksel, Alex
    Klein, Sanford A
    Lindberg, Eva
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Schuler, Mattias
    TRNSYS, the most complete solar energy system modeling and simulation software1994In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 5, no 1-4, p. 486-488Article in journal (Refereed)
    Abstract [en]

    The five computer programs TRNSYS, PRESIM, TRNSED, ONLINE, and PREBID have been put together into a program package which is the most complete solar energy system modeling and simulation software that is available today.

  • 2.
    Fiedler, Frank
    et al.
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Nordlander, Svante
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Persson, Tomas
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Thermal performance of combined solar and pellet heating systems2006In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 31, no 1, p. 73-88Article in journal (Refereed)
    Abstract [en]

    Various pellet heating systems are marketed in Sweden, some of them in combination with a solar heating system. Several types of pellet heating units are available and can be used for a combined system. This article compares four typical combined solar and pellet heating systems: System 1 and 2 with a pellet stove, system 3 with a store integrated pellet burner and system 4 with a pellet boiler. The often lower efficiency of pellet heaters compared to oil or gas heaters increases the final energy demand. Consequently heat losses of the various systems have been studied. The systems have been modeled in TRNSYS and simulated with parameters identified from measurements. For almost all systems the flue gas losses are the main heat losses except for system 3 where store heat losses prevail. Relevant are also the heat losses of the burner and the boiler to the ambient. Significant leakage losses are noticed for system 3 and 4. For buildings with an open internal design system 1 is the most efficient solution. Other buildings should preferably apply system 2 or 3. The right choice of the system depends also on whether the heater is placed inside or outside of the heated area. Unlike the expectations and results from other studies, the operation of the pellet heaters with modulating combustion power is not necessarily improving the performance. A large potential for system optimization exists for all studied systems, which when applied could alter the relative merits of the different system types.

  • 3.
    Huang, Pei
    et al.
    City University of Hong Kong.
    Sun, Yongjun
    A robust control of nZEBs for performance optimization at cluster level under demand prediction uncertainty2019In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 134, p. 215-227Article in journal (Refereed)
    Abstract [en]

    Collaborations among nZEBs (e.g. renewable energy sharing and battery sharing) can improve the nZEBs' performance at the cluster level. To enable such collaborations, existing studies have developed many demand response control methods to control the operation of nZEB systems. Unfortunately, due to lack of consideration of demand prediction uncertainty, most of the demand response control methods fail to achieve the desired performance. A few methods have considered the impacts of uncertainty, but they merely perform simple and limited collaborations among nZEBs, and thus they cannot achieve the optimal performance at the cluster level. This paper, therefore, proposes a nZEB control method that enables full collaborations among nZEBs and takes account of the demand prediction uncertainty. The proposed robust control method first analyzes the demand prediction uncertainty, next optimizes the nZEB cluster operation under uncertainty, and then coordinates single nZEB's operation using the cluster operational parameters. The performance of the robust control has been studied and compared with a deterministic control. Case studies show that the robust control can effectively increase the cluster load matching and reduce the grid interaction with the demand prediction uncertainty existed. The proposed method can achieve robust performance improvements for the nZEB cluster in practice particularly as uncertainty exists.

  • 4.
    Lindberg, Eva
    et al.
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Broman, Lars
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    An animation tool for demonstrating the importance of edge filters in thermophotovoltaic applications2002In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 28, p. 1305-1315Article in journal (Refereed)
    Abstract [en]

    In order to achieve high efficiency in a thermophotovoltaic (TPV) generator, it is important that a high fraction of emitted photons with energies below the TPV cell bandgap are reflected back to the emitter. This can be accomplished in several ways, and one suggestion is to place an edge filter between the emitter and the TPV cell array in an elliptical optic design. An animation tool, developed in the Excel® program, for determining the efficiency of an optical system is presented. The animation components are a black body emitter, an edge filter, and an array of TPV cells. The tool has been used to demonstrate the importance of an efficient filter and the usefulness of optics that makes the edge of the filter as sharp as possible.

  • 5.
    Lindberg, Eva
    et al.
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Broman, Lars
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    An animation tool for demonstrating the importance of edge filters in thermophotovoltaic applications2003In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 28, p. 1305-1315Article in journal (Refereed)
    Abstract [en]

    In order to achieve high efficiency in a thermophotovoltaic (TPV) generator, it is important that a high fraction of emitted photons with energies below the TPV cell band gap are reflected back to the emitter. This can be accomplished in several ways, and one suggestion is to place an edge filter between the emitter and the TPV cell array in an elliptical optic design. An animation tool, developed in the Excel program, for determining the efficiency of an optical system is presented. The animation components are a black body emitter, an edge filter, and an array of TPV cells. The tool has been used to demonstrate the importance of an efficient filter and the usefulness of optics that makes the edge of the filter as sharp as possible. It is available at www.du.se/tpv.

  • 6.
    Lindberg, Eva
    et al.
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Broman, Lars
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Fabergé optics and edge filter for a wood powder fuelled thermophotovoltaic system2002In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 28, p. 373-384Article in journal (Refereed)
    Abstract [en]

    In order to achieve high efficiency in a TPV generator, it is important that a high fraction of emitted photons with energies below the TPV cell bandgap are reflected back to the emitter. This can be accomplished in several ways. We present the idea of an internally reflecting eggshaped double cone with the emitter at one end, an edge filter at the wide center, and the TPV array at the other end. This geometry has so far been studied by means of both ray tracing analysis and by means of measurements with a simulated emitter. A sharp switchover from transmission to reflection in a multiple layer dielectric filter can be achieved only if the angles of incident rays are confined to a fairly narrow angular interval. The two methods both show that the studied optics can lower the angular spread of rays incident onto the filter and that some 96% of the emitted rays (in the ideal case) reach their goal without passing the filter or being reflected by the filter more than once. The concept of the whole of the wood powder fuelled TPV system is also given.

  • 7. Menegon, D.
    et al.
    Persson, Tomas
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Haberl, R.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Haller, M.
    Direct characterisation of the annual performance of solar thermal and heat pump systems using a six-day whole system test2020In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 146, p. 1337-1353Article in journal (Refereed)
  • 8.
    Persson, Tomas
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Wiertzema, Holger
    Win, Kaung Myat
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Modelling of dynamics and stratification effects in pellet boilers2019In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 134, p. 769-782Article in journal (Refereed)
    Abstract [en]

    Optimizing solar and pellet heating systems can be performed by system simulations in TRNSYS. However; this requires detailed boiler models that can properly model the thermal behaviour of the boilers, such as stratification and thermal response. This study uses a combination of existing models for modelling of the pellet burner part (TRNSYS Type 210) and the water volume (TRNSYS Type 340). This approach addresses the thermal dynamics and internal stratification more accurately than other available models. The objectives of this work are to develop a method for parameter identification for the model and to validate this method and the model itself. Sets of parameters are identified for two pellet boilers and one pellet stove with a water jacket (extended room heater) and the model is validated with a realistic dynamic operation sequence. The results show that modelling of stratification is essential in order to model the true behaviour of residential boilers. The test sequences used were adequate to parameterise the models and to provide the desired accuracy, except regarding the heat losses to room air. The model shows good accuracy for a stove and one boiler, but slightly worse performance for the other boiler regarding dynamics and modelling of the stratification.

    The full text will be freely available from 2021-01-01 15:49
  • 9.
    Rönnelid, Mats
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    The origin of the asymmetric annual irradiation distribution at high latitudes1999In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 19, p. 345-358Article in journal (Refereed)
  • 10. Wang, Xinru
    et al.
    Xia, Liang
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Copertaro, Benedetta
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Pan, Song
    Wu, Jinshun
    A systematic review of recent air source heat pump (ASHP) systems assisted by solar thermal, photovoltaic and photovoltaic/thermal sources2020In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 146, p. 2472-2487Article in journal (Refereed)
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