Sensitivity analysis of sampling and clustering techniques in expansion planning models

Short and long-term power system planning models are becoming more complex in oSrder to capture current and future market characteristics comprising more variability, uncertainty, and integration of geographically spread market areas. Dimension reduction methods can be used to keep the planning models tractable, e.g. time series sampling and clustering, but they represent a trade-off between model complexity and level of detail. The accuracy of dimension reduction methods can be measured both in terms of raw data processing and model output metrics, where the latter reveals how well a sampling technique fits that particular model instance. In this study, the robustness of several sampling and clustering techniques is quantified with different model instances by independently varying model parameters, such as e.g. the marginal cost of generation. As the obtained findings indicate that the performance of the considered techniques is, indeed, model-dependent, more insight into the performance of common dimension reduction techniques in power system planning applications is provided. The results are illustrated by a case study of the North Sea Offshore Grid (NSOG) for the scenario year 2030, using a bi-level mixed-integer linear optimization program. All things considered, systematic sampling and moment matching are shown to give the most robust results from the sensitivity analysis

Вплив компартійної ідеології на професійну повсякденність освітян СРСР у 1945–1953 рр.

The article is devoted to the investigation of the everyday life of the workers of the sphere of education of the USSR in the postwar period (1945–1953) and the influence of the Communist Party ideology on the professional activity of the educators. On the basis of available research, analysis of post-war pedagogical literature and periodicals, written memories of teachers, the authors make an attempt to reconstruct the professional life of teachers and teachers, determine the role and influence of the Communist Party ideology in their activities and the peculiarities of relationships in pedagogical groups.Стаття присвячена дослідженню повсякденності працівників сфери освіти СРСР у повоєнний період (1945–1953 рр.) та впливу на професійну діяльність освітян компартійної ідеології. На основі наявних досліджень, аналізу повоєнної педагогічної літератури та періодики, писемних спогадів педагогів автори роблять спробу реконструювати професійне життя вчителів та викладачів, визначити роль та вплив компартійної ідеології у їх діяльності та особливості взаємовідносин в педагогічних колективах

Analysis of the cough sound frequency in adults and children with bronchial asthma

It is well known that the frequency distribution of cough sound varies in different pathological conditions. Its identification could have diagnostic value. In this study the cough sound frequency in adults (n=20, 51.7±11 yrs), children (n=21, 11.8±0.4 yrs) asthmatics and healthy volunteers (n=25, 21 yrs) was explored. All patients were suffering from bronchial asthma. They were on a stable therapeutic regime and in a quiet status. Voluntary cough sound was recorded by a microphone and a tape recorder and digitally processed. Overlapping technique and Fast Fourier Transform were used to estimate the sound spectra. The records were smoothed by the method of Pascal triangle. They demonstrate the mean values of cough sound spectra. The registered pseudo three-dimensional plots of cough sound frequency (1 K spectra as function in time) of adults showed that the intensity of frequencies increased from 100 to 900 Hz in 3-4 waves. These frequencies afterwards decreased and between 1 to 2 kHz a smaller elevation was present. The spectra of children resembled to the spectrum of adults but had a smoother course. The spectra of asthmatics had some specificity and differed from the spectrum of healthy volunteers

Cost-optimal energy system design in zero energy buildings with resulting grid impact: A case study of a german multi-family house

Zero Energy Buildings (ZEBs) are considered as one of the key elements to meet the Energy Strategy of the European Union. This paper investigates cost-optimal solutions for the energy system design in a ZEB and the subsequent grid impact. We use a Mixed Integer Linear (MILP) optimisation model that simultaneously optimises the building’s energy system design and the hourly operation. As a ZEB have onsite energy generation to compensate for the energy consumption, it is both importing and exporting electricity. The hourly time resolution identifies the factors that influence this import/export situation, also known as the building’s grid impact. An extensive case study of a multi-family house in Germany is performed. The findings show that the energy system design and the grid impact greatly depend on the ZEB definition, the existing policy instruments and on the current energy market conditions. The results indicate that due to the feed-in-tariff for PV, the cost-optimal energy design is fossil fuelled CHP combined with a large PV capacity, which causes large grid impacts. Further, we find that heat pumps are not a cost-optimal choice, even with lower electricity prices or with increased renewables in the electric power system

Convex Models for Optimal Utility-Based Distributed Generation Allocation in Radial Distribution Systems

© 2007-2012 IEEE. This paper introduces various models for optimal and maximal utility-based distributed generation penetration in the radial distribution systems. Several problems with different probabilistic indices as objective functions constrained by power flow equations, distributed generation penetration, voltage, and thermal limits are proposed to obtain the optimal penetration of distributed generations on rural distribution networks. There are tradeoffs between interests and risks that the distribution network operators or distribution companies may be willing to take on. Thus, to have an effective method for maximal allocation of distributed generations, new indices are proposed, and the problems are formulated as a risk-constrained optimization model. The obtained problems have mixed-integer nonlinear programming and nonconvex forms because of nonlinearity and nonconvexity of the optimal power flow (OPF) equations and indices, leading to computationally nondeterministic polynomial-time-hard problems. Accordingly, in this paper, convex relaxations of OPF are introduced instead of the conventional nonlinear equations. Efficient linear equivalents of the objective function and constraints are introduced to reduce the computational burden. Test results of the proposed models on a radial distribution system are presented and discussed

Methodology for optimal energy system design of zero energy buildings using mixed-integer linear programming

According to EU’s Energy Performance of Buildings Directive (EPBD), all new buildings shall be nearly Zero Energy Buildings (ZEB) from 2018/2020. How the ZEB requirement is defined has large implications for the choice of energy technology when considering both cost and environmental issues. This paper presents a methodology for determining ZEB buildings’ cost optimal energy system design seen from the building owner’s perspective. The added value of this work is the inclusion of peak load tariffs and feed-in-tariffs, the facilitation of load shifting by use of a thermal storage, along with the integrated optimisation of the investment and operation of the energy technologies. The model allows for detailed understanding of the hourly operation of the building, and how the ZEB interacts with the electricity grid through the characteristics of its net electric load profile. The modelling framework can be adapted to fit individual countries' ZEB definitions. The findings are important for policy makers as they identify how subsidies and EPBD’s regulations influence the preferred energy technology choice, which subsequently determines its grid interaction. A case study of a Norwegian school building shows that the heat technology is altered from HP to bio boiler when the ZEB requirement is applied