Risto Lahdelma - Academia.edu (original) (raw)

Papers by Risto Lahdelma

Finland is among the countries with the highest amount of English-taught programmes in higher edu... more Finland is among the countries with the highest amount of English-taught programmes in higher education in Europe (Wächter and Maiworm 2008). This article analyses, how the higher education language situation of a small country with a marginal majority language (Finnish) and an official bilingual status (Finnish and Swedish) has historically developed from the setting of “drawing the line” between Finland and Sweden or Finland and Russia (Harle and Moisio 2000) in the 19th century and the early 20th century (nationalism), towards drawing the line between Finnish/Swedish and English in the late 20th century (globalization). It then continues to present a case of foreign language (in practice English) programmes in higher education as an example of the globalization development in Finnish higher education. The data for the article consists of the internationalization strategies for Finnish higher education, The Finnish International Study Programme Database, and introductory texts fro...

Lecture Notes in Control and Information Sciences

The short term scheduling of a national energy production for one week time horizon is considered... more The short term scheduling of a national energy production for one week time horizon is considered. The problem is to optimize the use of various kinds of power plants such as nuclear power, conventional condensing power, counter pressure power and water power. Energy storages are also included in the optimization.

European Journal of Operational Research, 2017

This paper deals with the transmission-constrained multi-site combined heat and power (CHP) probl... more This paper deals with the transmission-constrained multi-site combined heat and power (CHP) problem and formulates it as a linear programming (LP) model with a special structure. CHP systems are treated as an extension of power-only systems. Each site can be treated as a regional energy system to supply both heat and power. Heat demand is satisfied by local production while power demand can be satisfied by local generation plus power exchange over the power network. The challenge of this problem is that power transmission needs to be coordinated with both power and heat production in each site. The transmission-constrained multi-site CHP system can be operated cost-efficiently according to hourly demand forecast for heat and power by coordinating production and transmission activities among different sites. An efficient network power Simplex algorithm is developed to this end. Numerical experiments with realistic test data show that the algorithm is 7 to 360 (with average 30) times faster than a commercial LP code.

Modelling, Identification and Control / 827: Computational Intelligence, 2015

Energies

This study is about multicriteria decision aiding (MCDA) for the green airports program of the Mo... more This study is about multicriteria decision aiding (MCDA) for the green airports program of the Moroccan Airport Authority ONDA. The goal of the program is to develop significant amounts of renewable power at airports. In particular, ONDA wants to select airports at which large solar and wind power parks should be built. Multiple criteria, including economy, technical feasibility, and environmental concerns, must be considered simultaneously. In this study, we apply Stochastic Multicriteria Acceptability Analysis (SMAA) for ranking the candidates to be developed into green airports. The analysis is conducted in phases with different sets of criteria. This study is the first application of MCDA for developing large-scale renewable energy production at airports. As a theoretical novelty, the pairwise winning indices of SMAA are used to form stochastic partial and complete rankings of the alternatives. Based on the results, two alternatives obtain the best and second-best rank in every ...

Modern decision making problems are discrete and multicriteria by nature, and involve several dec... more Modern decision making problems are discrete and multicriteria by nature, and involve several decision makers (DMs). One of the key questions in this type of problems is how the preferences of the DMs can be modelled. Usually the DMs are not sure of their preferences or will not tell them to the analyst, because they are not able to express their preferences directly. In these type of situations the decision support system should allow modelling of ignorance. Stochastic Multicriteria Acceptability Analysis (SMAA) is a family of methods to aid DMs in discrete decision aiding problems. Dempster-Shafer theory of evidence (DST) allows modelling of ignorance by using belief functions. In this paper we show how the preferences of multiple DMs or other stakeholders can be modelled and combined using DST, and how this information can then be encoded as interval constraints for sets of weights in SMAA. Our contribution has a wide range of practical applications. We present a real-world case ...

Energies, 2020

This study proposes to use gas-fired boilers as peak shaving heat sources in heating substations ... more This study proposes to use gas-fired boilers as peak shaving heat sources in heating substations due to their capability to increase the reliability, flexibility and heat capacity without the need to change the district heating network (DHN). However, the design and operational requirements with different connection modes for this kind of DH system are still not clear. This paper presents a systematic study on this kind of DH system, analyzes the connection modes of series and parallel connections between the gas-fired boilers and the heat exchangers. For each connection mode, we figured out the thermal balances and obtained the design and operational parameters including the supply temperatures of the heat exchangers, gas-fired boilers and their variations under different network temperature levels and the base load ratios (β). Under the series connection mode, the design supply temperature of the heat exchangers has no relation with the design peak shaving flow ratio (ω’); it decr...

Energy and Buildings, 2014

ABSTRACT Plate heat exchangers (PHE) have consolidated their position as key components of modern... more ABSTRACT Plate heat exchangers (PHE) have consolidated their position as key components of modern heating processes. They are widely accepted as the most suitable design for heat transfer applications in various processes, including the field of energy-efficient district heating (DH). This study refers to new DH coupling and control applied to a consumer substation. The concept introduces a new mass flow control model optimising the primary and secondary water streams to achieve remarkably higher temperature cooling in a new low temperature programme with diminished pressure losses. Here the operation of the ring network and the mass flow control in the substation are studied theoretically. A calculation procedure and transient models were constructed for the DH network, building structures, and heating heat exchangers. The PHE and its operation in the substation were studied by means of a corrugated plate model with five vertical parts and 10 elements. Variations in the flow rates, pressure losses, and overall heat transfer coefficients were received for the selected days. As a result almost equal heat capacity flows were found between the hot and cold sides of the PHE with maximum temperature cooling. The key performance factors of the heat exchanger, NTU and effectiveness, were monitored and the mean values obtained were 9.2 and 0.9, respectively.

European Journal of Operational Research - EJOR, 2005

Stochastic multicriteria acceptability analysis (SMAA) is a ,family of methods for aiding multicr... more Stochastic multicriteria acceptability analysis (SMAA) is a ,family of methods for aiding multicriteria group decision making. These methods are based on exploring the weight space in order todescribe the preferencesthat make each alternative the most preferred one, or thatgiv ea certain rank for a specific alternative. The mainresults of the analysisare rank acceptability

Omega, 2009

... Risto Lahdelma a , E-mail The Corresponding Author and Pekka Salminen b , Corresponding Autho... more ... Risto Lahdelma a , E-mail The Corresponding Author and Pekka Salminen b , Corresponding Author Contact Information , E-mail The Corresponding Author. ... P is not based on a utility or value function model; instead the DMs preferences are represented in the spirit of prospect ...

The International Journal of Advanced Manufacturing Technology, 2010

European Journal of Operational Research, 2002

Stochastic multi-criteria acceptability analysis (SMAA) is a multi-criteria decision support meth... more Stochastic multi-criteria acceptability analysis (SMAA) is a multi-criteria decision support method for multiple decision-makers (DMs) in discrete problems. SMAA does not require explicit or implicit preference information from the DMs. Instead, the method is based on exploring the weight space in order to describe the valuations that would make each alternative the preferred one. Partial preference information can be represented in the weight space analysis through weight distributions. In this paper we compare two variants of the SMAA method using randomly generated test problems with 2–12 criteria and 4–12 alternatives. In the original SMAA, a utility or value function models the DMs&#x27; preference structure, and the inaccuracy or uncertainty of the criteria is represented by probability distributions. In SMAA-3, ELECTRE III-type pseudo-criteria are used instead. Both methods compute for each alternative an acceptability index measuring the variety of different valuations that supports this alternative, and a central weight vector representing the typical valuations resulting in this decision. We seek answers to three questions: (1) how similar are the results provided by the decision models, (2) what kind of systematic differences exists between the models, and (3) how could one select indifference and preference thresholds of the pseudo-criteria model to match a utility model with given probability distributions?

Applied Thermal Engineering, 2013

ABSTRACT District heating (DH) systems are an inseparable part of the infrastructure in many coun... more ABSTRACT District heating (DH) systems are an inseparable part of the infrastructure in many countries. Today more attention is being paid to energy savings, efficiency improvements, and the replacement of fossil fuels by renewable energy. Research in the field of DH is focused on the supply of areas with low heat demand and low-energy buildings and on an increased share of heat being produced from renewable energy sources. New DH systems are expected to remain competitive in the future. In this study a new DH concept is proposed which is based on mass flow control. The DH system using mass flow control is meant for the concept of a ring network technology where mass flow rates in consumer substations are controlled by pumps with inverters to improve heat transfer. It will replace the traditional DH network and control in which water flow is throttled by control valves. The new control system will enable new temperature curves to be adopted for supply and return temperatures and more significant temperature cooling. First, a new topology and control method is presented. This ring network and the method used to control the flow rate of the primary supply water and its temperature are compared with the traditional technology. This method clearly shows the benefits of the DH applications under consideration. Second, these benefits are demonstrated by mathematical modelling. A simulation model is developed to study the area heating of six single-family houses and two apartment buildings. The static operation on the primary side of the networks is investigated for the most common outdoor temperatures. The numerical results are compared to those achieved with the traditional technology. The new flow rate is 46%, the pressure loss 25%, and the pumping power 12% of their former values in the pipes. The heat losses increase slightly with higher outdoor temperatures. The return temperature is lowest with the new technology. In the future the equipment that consumers will have will be more intelligent. The new technology that is presented allows consumers to adjust their energy consumption more easily by means of fast feedback on outdoor and room temperatures.

Journal of Clean Energy Technologies, 2015

A sustainable energy system is an integrated approach to supplying local energy demands from rene... more A sustainable energy system is an integrated approach to supplying local energy demands from renewable energy or/and high-efficiency polygeneration energy sources. The approach can be seen as a development of the distributed generation concept. The main characteristics of a sustainable energy system are (cost) efficiency, reliability and environmentalfriendliness. In this paper, we mainly discuss the role of the polygeneration in a distributed energy system and contributions of polygeneration in the sustainable energy system development. We also describe the characteristics of polygeneration plants to highlight the complexity of polygeneration technologies. In addition, we review the typical method for dealing with interdependence between different energy products for polygeneration and point out some practices in the industry may prevent the potential of polygeneration into full play. Keywords— polygeneration; energy efficiency; distributed energy system; sustainable energy system.

A framework for a multi-attribute multi-source data fusion is described. Uncertainty of data is m... more A framework for a multi-attribute multi-source data fusion is described. Uncertainty of data is modeled by fuzzy sets. The problem is considered on a general level. Credibility of sources, compatibility of data, as well as their reasonableness, are taken into consideration. The proposed method is illustrated by an example.

ELECTRE III is a well-established multiple criteria decision making method with a solid track of ... more ELECTRE III is a well-established multiple criteria decision making method with a solid track of real-world applications. It requires precise values to be specified for the parameters and criteria measurements, which in some cases might not be available. In this paper we present a method, SMAA-III, that allows ELECTRE III to be applied with imprecise parameter values. By allowing imprecise values, the method also allows an easily applicable robustness analysis. In SMAA-III, simulation is used and descriptive measures are computed to characterize stability of the results. We present a software implementing the method and show the usage by re-analyzing an existing case study.