| 1. |
- Holmberg, Henrik, et al.
(author)
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Minimization of total drying costs for a continuous packed-bed biomass dryer operating at an integrated chemical pulp and paper mill
- 2014
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In: Biomass and Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 71, s. 431-442
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Journal article (peer-reviewed)abstract
- This paper presents a MILP (Mixed Integer Linear Programming) model for a continuous packed-bed biomass dryer. The model minimizes total drying costs, including both capital and operational costs, of the dryer. Heated air, which flows through a biomass bed and perforated conveyor, is used as drying gas by the dryer. We define the dryer size with the help of an experimentally-measured characteristic drying curve. The MILP model is tested in a case study where the dryer is assumed to have been installed at a Scandinavian pulp and paper mill. There are three different heat sources available for the heating of drying air: warm water at 60 °C, warm water at 80 °C and backpressure steam at the pressure of 0.4 MPa. The results indicate that, in practice, the use of only low-temperature warm water flows for heating of drying air is the most economic method when their prices are low (below 1 € MWh-1 in the case study). Warm water flows are usually waste heat from pulp and paper mills and their prices are low compared to the price of back-pressure steam (typically from 10 to 15 € MWh-1). The use of steam for drying may be reasonable if the price of warm water is for some reason clearly higher than the price of a typical waste-heat stream. The MILP model presented in this work can be used for minimizing drying costs of any material (not only biomass) dried in a continuous packed-bed dryer if the characteristic drying curve of the material is available.
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| 2. |
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| 3. |
- Lahdelma, Risto, et al.
(author)
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Optimization and Multicriteria Evaluation of District Heat Production and Storage
- 2019
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In: Multiple Criteria Decision Making. - Cham : Springer Nature. ; , s. 371-396
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Book chapter (other academic/artistic)abstract
- Climate change mitigation policy requires reducing dependence on fossil fuels and transition to low carbon energy production in district heating (DH). We study here inclusion of two kinds of renewable energy to a CHP based DH system in Finland: solar heat and ground source heat. In addition, we apply heat storages to balance the gap between production and fluctuating demand. The optimal operation of the extended systems is determined by a simulation and optimization model to minimize the operating costs. We evaluate the different possible extensions in terms of multiple economic, technical and environmental criteria using Stochastic Multicriteria Acceptability Analysis (SMAA). The results show that under Finnish conditions, ground source heat is more favourable than solar heat for DH.
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| 4. |
- Lahdelma, Risto, et al.
(author)
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Reference Point Approach for Multiple Decision Makers
- 2005
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In: European Journal of Operational Research. - : Elsevier BV. - 0377-2217 .- 1872-6860. ; 164:3, s. 785-791
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Journal article (peer-reviewed)abstract
- We consider multiple criteria decision-making problems where a group of decision-makers wants to find the most preferred solution from a discrete set of alternatives. We develop a method that uses achievement functions for charting subsets of reference points that would support a certain alternative to be the most preferred one. The resulting descriptive information is provided to the decision-makers in the form of reference acceptability indices and central reference points for each decision alternative. Then, the decision-makers can compare this information with their own preferences. We demonstrate the use of the method using a strategic multiple criteria decision model for an electricity retailer.
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| 5. |
- Wang, Haichao, et al.
(author)
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Heat-power peak shaving and wind power accommodation of combined heat and power plant with thermal energy storage and electric heat pump
- 2023
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In: Energy Conversion and Management. - : Elsevier Ltd. - 0196-8904 .- 1879-2227. ; 297
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Journal article (peer-reviewed)abstract
- Wind power curtailment becomes a major problem in many countries. The wind accommodation mechanisms and energy saving potentials for the combined heat and power plant with thermal energy storage, electric heat pump and both should be evaluated more systematically and accurately to accommodate more wind power. Heat-power peak shaving capacities for thermal energy storage, electric heat pump and both are analyzed using a graphical method, while the operation strategy is proposed to maximize wind accommodation. A simulation model for wind power accommodation considering the energy balances and constraints of all production units is developed based on EnergyPRO. A regional energy supply system in Jilin Province, China is selected as the case study, where the influences of different peak shaving technologies and their parameters on the wind accommodation and energy saving are studied. The wind curtailment ratio is reduced from 20.31% to 13.04% and 7.51% with thermal energy storage and electric heat pump respectively, and it is further reduced to 4.21% with both. Systems with electric heat pump can save energy from 1.1% to 5.8% with different parameters of the peak shaving devices. It was found that electric heat pump has better accommodation capability than that of thermal energy storage. Wind accommodation can be improved by adding thermal energy storage to electric heat pump, but the effect gradually decreases as the storage size increases. Electric heat pump can increase the system’s energy efficiency, but it is not always energy efficient by adding thermal energy storage to electric heat pump. In fact, thermal energy storage should not be too large, otherwise the system’s energy efficiency will be reduced.
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| 6. |
- Wang, Haichao, et al.
(author)
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Study on the performance of a forced convection low temperature radiator for district heating
- 2023
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In: Energy. - : Elsevier Ltd. - 0360-5442 .- 1873-6785. ; 283
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Journal article (peer-reviewed)abstract
- Low temperature district heating has significant advantages in energy efficiency, but a huge amount of existing radiators lack the capabilities for low-temperate heating. The innovation of this study is to develop an optimal and techno-economic method to improve the heating power of existing radiator by mounting a small fan considering different hydraulic connection modes. An experimental test rig was designed to study the optimal installation positions and angles of the fan. For a dormitory room in China, a computational fluid dynamics (CFD) model was developed and verified. The model was used to determine the lowest supply temperature of the radiator. Results show that the fan should be placed in a position and angle that blows air over the hottest surface of the radiator i.e. the hot center. The lowest supply temperatures before and after installing the fan are 42.3 °C and 39.5 °C. The response speed is increased by 28%, stability time is shortened by 13%, while the maximum indoor temperature difference is reduced by 15% and the maximum indoor air velocity is reduced by 0.07 m/s. Payback time is 63 days for case study, indicating a good economic feasibility. The method is beneficial to both the heat plant and users.
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| 7. |
- Yevseyeva, Iryna, et al.
(author)
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SMAA-Classification - A New Method for Nominal Classification
- 2007
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Reports (other academic/artistic)abstract
- We have developed a multicriteria decision aiding method for nominal classification for situations where prefer-ence information is imprecise, uncertain or absent. Such situations may appear, for instance, when the decisionmaker is not sure about his or her preferences or when there are multiple decision makers who have difficulties inagreeing about their common preference. The new SMAA-Classification method extends Stochastic Multicrite-ria Acceptability Analysis (SMAA) methodology for classification problems. The method provides the decisionmaker with descriptive information in the form of acceptability index for each alternative to be classified intoeach predefined class. We test the new method with several applications.
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