Papers by Pall Valdimarsson
Heat load for a sample building with and without insulation using Chinese and Icelandic building ... more Heat load for a sample building with and without insulation using Chinese and Icelandic building codes was calculated in this paper. The results show that the calculated heat load in Icelandic codes is bigger than that of in Chinese for the un-insulated building. However, when insulation is added to the building envelope, heat load decreases 45.4% in Chinese codes. If the thermal insulation property is improved to satisfy the Icelandic standard, which was valid at the time of construction for the sample building, the heat load decreases 70.4%, which indicates that improving thermal insulation and insulation properties could reduce energy consumption significantly.
This paper treats a few aspects of the Organic Rankine Cycle technology. The benefits of variable... more This paper treats a few aspects of the Organic Rankine Cycle technology. The benefits of variable geometry inlet guide vanes (IGV's) in radial turbines for the ORC cycle are presented and discussed. One of the areas where variable IGV's are beneficial is cogeneration of power and district heat. Cogeneration and how the district heating should be connected to the power plant is presented, as well as the benefits from the variable IGV's. The third theme treated is the so-called transcritical ORC cycle, which is already established in waste heat recovery, but is now making its entry into geothermal power production. Finally a hybrid power plant is discussed, in this case a back pressure steam turbine is used together with an ORC plant, making release of non-condensable gases easier, as well as enabling the use of wells with lower wellhead pressure than what a flash plant could use.
Production of electricity from geothermal heat - efficiency calculation and ideal cycles
Energy and Exergy Analysis of Sabalan Binary Geothermal Power Plant
Journal of the Geothermal Research Society of Japan, Jul 25, 2011
The minerals, metals & materials series, 2018
Around half of the energy consumed in aluminum production is lost as waste heat. Approximately 30... more Around half of the energy consumed in aluminum production is lost as waste heat. Approximately 30-45% of the total waste heat is carried away by the exhaust gas from the smelter which is the most easily accessible waste heat stream. Alcoa Fjardaal in east Iceland produces 350 000 tons annually, emitting the 110 °C exhaust gas with 88.1 MW of heat. This work concentrates on creating and comparing models of low-temperature energy utilization from the aluminum production. Three scenarios, including organic Rankine cycle (ORC) system for electric power production, heat supply system and combined heat and power (CHP) system, were proposed to recover waste heat from the exhaust gas. The electric power generation potential is estimated by ORC models. The maximum power output was found to be is 2.57 MW for an evaporation temperature of 61.22°C and R-123 as working fluid. 42.34 MW can be produced by the heat supply system with the same temperature drop of the exhaust gas in the ORC system. The heat requirement to supply heat to a district heating system for the local community can be fulfilled by the heat supply system. There is a potential opportunity for agriculture, snow melting and other industrial applications with the heat supply system. The CHP system is more comprehensive. 1.156 MW power and 23.55MW heating capacity can be produced by CHP system. The highest energy efficiency is achieved by the heat supply system and the maximum power output can be obtained with the ORC system. In the power generation system, the efficiency of organic Rankine cycle is significantly limited by the low temperature of the exhaust gas. It would be possible to improve the efficiency of the ORC by increasing the heat source temperature. The temperature of the heat source can be raised by reducing the dilution air from the environment into the pot. The heat balance of the smelter is studied. The positive result is found, that the efficiency of the cycle and power output are effectively improved, and a good trend of the system performance can be observed. The maximum 9.174 MW power can be produced at the exhaust gas temperature of 150 °C, and the system exergy efficiency of 54.38% can be achieved in these conditions. This work shows there is a good potential for heat and power production by recovering the waste heat from aluminum production. The efficiency of energy utilization in aluminum production can be effectively improved as studied.
60 TCT - Total Combustion Technology
Flow controller assumptions in physical models of geothermal district heating systems
Radial inflow turbines for Organic Rankine Cycle systems
Organic Rankine Cycle (ORC) Power Systems, 2017
Abstract Radial inflow turbines are widely used in a large range of systems from mini waste heat ... more Abstract Radial inflow turbines are widely used in a large range of systems from mini waste heat recovery (WHR) applications to big geothermal power plants. This chapter will be focused on the applications, design, and future development of this component.
The Minerals, Metals & Materials Series, 2018
Around half of the energy consumed in aluminum production is lost as waste heat. Approximately 30... more Around half of the energy consumed in aluminum production is lost as waste heat. Approximately 30-45% of the total waste heat is carried away by the exhaust gas from the smelter which is the most easily accessible waste heat stream. Alcoa Fjardaal in east Iceland produces 350 000 tons annually, emitting the 110 °C exhaust gas with 88.1 MW of heat. This work concentrates on creating and comparing models of low-temperature energy utilization from the aluminum production. Three scenarios, including organic Rankine cycle (ORC) system for electric power production, heat supply system and combined heat and power (CHP) system, were proposed to recover waste heat from the exhaust gas. The electric power generation potential is estimated by ORC models. The maximum power output was found to be is 2.57 MW for an evaporation temperature of 61.22°C and R-123 as working fluid. 42.34 MW can be produced by the heat supply system with the same temperature drop of the exhaust gas in the ORC system. The heat requirement to supply heat to a district heating system for the local community can be fulfilled by the heat supply system. There is a potential opportunity for agriculture, snow melting and other industrial applications with the heat supply system. The CHP system is more comprehensive. 1.156 MW power and 23.55MW heating capacity can be produced by CHP system. The highest energy efficiency is achieved by the heat supply system and the maximum power output can be obtained with the ORC system. In the power generation system, the efficiency of organic Rankine cycle is significantly limited by the low temperature of the exhaust gas. It would be possible to improve the efficiency of the ORC by increasing the heat source temperature. The temperature of the heat source can be raised by reducing the dilution air from the environment into the pot. The heat balance of the smelter is studied. The positive result is found, that the efficiency of the cycle and power output are effectively improved, and a good trend of the system performance can be observed. The maximum 9.174 MW power can be produced at the exhaust gas temperature of 150 °C, and the system exergy efficiency of 54.38% can be achieved in these conditions. This work shows there is a good potential for heat and power production by recovering the waste heat from aluminum production. The efficiency of energy utilization in aluminum production can be effectively improved as studied.
Heat transfer modelling of a plate radiator for district heating applications
International Journal of Energy Research, May 1, 1991
ABSTRACT The paper presents a heat transfer model of a plate radiator for district heating applic... more ABSTRACT The paper presents a heat transfer model of a plate radiator for district heating applications, developed by the authors. A microcomputer program based on the model was implemented for use in design and simulation of radiator space heating systems. The theoretical model is compared with a model based on experimental data. Results from using the new model to evaluate the accuracy of the German standard DIN 4703 (Q/Qo = (LMTD/LMTD0)1.3) for Icelandic geothermal district heating are presented. Conclusions are drawn on the basis of the results.
Flow controller assumptions in physical models of geothermal district heating systems
New development in the ORC technology
As a country, Uganda has a growing interest to diversify its energy mix from dependency on hydro ... more As a country, Uganda has a growing interest to diversify its energy mix from dependency on hydro power and traditional biomass. Prospects for the exploitation of the existing geothermal potential are therefore not only in power generation, but also direct use applications, although geothermal development is still in the preliminary stages. This study places emphasis on the range of opportunities for direct use of low temperature geothermal heat in Uganda. Because the transportation of heat over long distances is uneconomical; it is advisable to utilize the heat within a given radius of its source. In this study, the areas within such radii where geothermal activity is witnessed were assessed based on; fluid temperature, climate, population as well as main economic activities to better understand the market opportunities for the heat that will be extracted. Some of the more outstanding geothermal fields were studied; from which it was observed that out of the diversity of sectors for...
Energy and Exergy Analysis of Sabalan Binary Geothermal Power Plant
Inaugural US-EU-China Thermophysics Conference-Renewable Energy 2009 (UECTC 2009 Proceedings), 2009
Heat load for a sample building with and without insulation using Chinese and Icelandic building ... more Heat load for a sample building with and without insulation using Chinese and Icelandic building codes was calculated in this paper. The results show that the calculated heat load in Icelandic codes is bigger than that of in Chinese for the un-insulated building. However, when insulation is added to the building envelope, heat load decreases 45.4% in Chinese codes. If the thermal insulation property is improved to satisfy the Icelandic standard, which was valid at the time of construction for the sample building, the heat load decreases 70.4%, which indicates that improving thermal insulation and insulation properties could reduce energy consumption significantly.
60 TCT - Total Combustion Technology
The Mt Sabalan geothermal field in NW of Iran is currently under development. A double flash cycl... more The Mt Sabalan geothermal field in NW of Iran is currently under development. A double flash cycle has been selected for power generation. The obtained results show that the maximum power output from the plant can be 54 MWe with pressures equal to 5.5, 0.9 and 0.1 bar for high and low pressure steps and condenser, respectively. Mathematical models for energy and exergy flows were developed and implemented in the Engineering Equation Solver (EES) software. A few assumptions and simplifications were made. The energy and exergy rates of the waste brine have been calculated as 18.7% and 15.8% of the total available energy and exergy rates, respectively. The separated brine can be used as a heat source for a district heating system or some other forms of direct use. Reinjection should also be taken into account. The parts of the system with largest exergy destruction are the condenser, the low pressure turbine, the low pressure separator and the disposed waste brine. The overall exergy efficiency for the power plant is 45.2% and the overall energy efficiency is 9.4%. Exergy analysis was found helpful and important tool for analyzing the geothermal plant and should be considered at early stages of designs.
Production of electricity from geothermal heat - efficiency calculation and ideal cycles
Production of electricity from heat requires a heat engine working between two heat reservoirs, a... more Production of electricity from heat requires a heat engine working between two heat reservoirs, a heat source and a heat sink. The Carnot efficiency is defined for the reversible heat engine working between two reservoirs of infinite heat capacity and constant temperature. Geothermal heat source is a stream of water, either in the liquid phase or as liquid-steam mixture of any quality. The heat capacity of the heat source is thus finite, and the source temperature is not constant in the heat addition process of the heat engine. Same applies for the heat rejection of the heat engine, usually the cooling fluid available has some strict limitation on the possible temperatures, and rejection to a sink at a constant temperature is practically almost impossible. This paper analyzes electricity production when the heat source and the heat sink do not have a constant temperature. The maximum production efficiency is defined and calculated, both for pure electricity production (E) and Combin...
Transient Simulation of Refrigerated and Chilled Seawater System
Fishing technology onboard fishing vessels fishing pelagic species has received increased attenti... more Fishing technology onboard fishing vessels fishing pelagic species has received increased attention, especially the influence of storage method on fish quality and the vessel's energy consumption. More flexible storage methods are needed to give higher quality to the landed pelagic species thereby lowering energy consumption and investment costs. Today, when sizing storage systems, high capacity in the pre-chilling period is used as a designing criteria resulting in large installed refrigeration capacity and limited flexibility. To analyse the demands of better fish quality and lower energy consumption of these systems, a new storage method is simulated to compare it with standard storage methods like refrigerated seawater (RSW) and chilled seawater (CSW). The purpose of the simulation is to analyse the chilling of the catches and operational cost of the systems to see if combined system (RSW/CSW) gives better results. A mathematical model is developed and applied to simulate a ...
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Papers by Pall Valdimarsson