Search results for " Linear programming"
showing 9 items of 19 documents
A Column Generation Approach to Scheduling of Periodic Tasks
2011
We present an algorithm based on column generation for a real time scheduling problem, in which all tasks appear regularly after a given period. Furthermore, the tasks exchange messages, which have to be transferred over a bus, if the tasks involved are executed on different ECUs. Experiments show that for large instances our preliminary implementation is faster than the previous approach based on an integer linear programming formulation using a state-of-the-art solver.
Energy Management Systems and tertiary regulation in hierarchical control architectures for islanded microgrids
2015
In this paper, the structure of the highest level of a hierarchical control architecture for micro-grids is proposed. Such structure includes two sub-levels: the Energy Management System, EMS, and the tertiary regulation. The first devoted to energy resources allocation in each time slot based on marginal production costs, the latter aiming at finding the match between production and consumption satisfying the constraints set by the EMS level about the energy production in each time slot. Neglecting the efficiency of the different energy generation systems as well as that of the infrastructure for electrical energy distribution, the problem dealt with by the EMS sub-level is linear and can …
On the Reliability of Optimization Results for Trigeneration Systems in Buildings, in the Presence of Price Uncertainties and Erroneous Load Estimati…
2016
Cogeneration and trigeneration plants are widely recognized as promising technologies for increasing energy efficiency in buildings. However, their overall potential is scarcely exploited, due to the difficulties in achieving economic viability and the risk of investment related to uncertainties in future energy loads and prices. Several stochastic optimization models have been proposed in the literature to account for uncertainties, but these instruments share in a common reliance on user-defined probability functions for each stochastic parameter. Being such functions hard to predict, in this paper an analysis of the influence of erroneous estimation of the uncertain energy loads and pric…
Flexibility Services to Minimize the Electricity Production from Fossil Fuels. A Case Study in a Mediterranean Small Island
2019
The design of multi-carrier energy systems (MESs) has become increasingly important in the last decades, due to the need to move towards more efficient, flexible, and reliable power systems. In a MES, electricity, heating, cooling, water, and other resources interact at various levels, in order to get optimized operation. The aim of this study is to identify the optimal combination of components, their optimal sizes, and operating schedule allowing minimizing the annual cost for meeting the energy demand of Pantelleria, a Mediterranean island. Starting from the existing energy system (comprising diesel generators, desalination plant, freshwater storage, heat pumps, and domestic hot water st…
Optimization of polygeneration plants and μ-grids for civil applications
2010
The problem of combined energy production and distribution of warm and cold fluids is very complex because it includes two possible configurations, the small single unit for individual buildings and the large plant integrated with district heating networks. Dealing with such a complex problem, involving a very large number of variables, requires efficient algorithms and resolution techniques. The present study illustrates a MILP approach to the optimization of synthesis, design and operation for CHCP-based μ-grids including thermal energy storages. The proposed approach develops a method for designing and optimizing district energy systems, starting with the information available for the di…
The Multi-period Multi-trip Container Drayage Problem with Release and Due Dates
2021
Abstract The Container Drayage Problem (CDP) aims at routing a fleet of trucks, based at a common terminal, to serve customers while minimizing the total travel distance. Each trip starts from and ends at the terminal, and handles a subset of customers. Each customer requires either that a container is picked up or delivered. We introduce a more realistic variant, i.e., the Multi-trip Multi-period CDP with Release and Due Dates (MM-CDP-RDD), in which the planning horizon is composed of several periods (days). On each day, each truck may perform more than one trip respecting the Release and Due Dates (RDD) associated with customer services, corresponding to the first and the last day on whic…
Flexibility Services in a Mediterranean Small Island to Minimize Costs and Emissions Related to Electricity Production from Fossil Fuels
2020
In last years, the energy efficiency in non-interconnected islands became an important topic, since the electricity production is often based on diesel generators, thus contributing to the global warming. Italian government recently emitted two decrees to promote the introduction of renewable energy technologies in 21 non-interconnected islands, both for electrical and thermal uses. In this paper, the economic and environmental feasibility of the introduction of renewable energies in the island of Pantelleria was assessed adopting an optimization approach. Furthermore, the flexibility provided from the local desalination plant and the domestic water heaters was evaluated. The final demands …
CROSS-DOCKING TRANSSHIPMENT PROBLEM APPROACHED BY NON LINEAR PROGRAMMING AND SIMULATION ANALYSIS
2012
The need for fast product delivery causes the attention of supply chain is addressed to strategies able to optimize the distribution process. In this field the crossdocking seems to be an efficient strategy which makes possible to reduce or eliminate the storage phase by meeting customer demand. In this paper a transshipment problem for cross-docking strategy is considered by means of a deterministic model studied through the non linear programming technique. The solution found allows to determine the optimal quantities to ship, the number of routes activated and the optimal truck number when the constraint on truck capacity is enforced. The influence of the demand fluctuation is also addre…
ASPECTS REGARDING THE OPTIMIZATION OF THE QUALITY OF MANAGERIAL DECISIONS - SOLVING AN OPTIMIZATION PROBLEM IN THE SENSE OF SUSTAINABILITY WITH WINQSB
2012
In this paper we present an optimization problem solving, problem that is mathematically shaped as a linear programming problem. This is made with the purpose of finding an optimal solution which is also a sustainable one. In the present and future society, it is clear that nothing can be done honestly, but only in the sense of a professional and sustainable thinking (Konrad, C., 2011, pp.202-217, Petrescu, I., 2006, p.1). To think sustainable can also mean “to be calculated”, in popular language “to choose wisely”, all for achieving the proposed project, being careful to using non-renewable resources, to pollution, to protection for human resource, etc. Of course that the logical and preci…