Optimization of the heat plant of district energy systems (original) (raw)
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Optimization approaches in district heating and cooling thermal network
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A district energy system based on "thermal bus" was proposed, in which the heating and cooling water transmission processes shared one set of the distribution pipe network. Combined with the gas energy stations, ground source heat pumps, small-scale photovoltaic power stations and rooftop solar collectors and other facilities, it provided the users in the region with heating in winter, cooling in summer and power supply all year round. From the perspective of the bidirectional (supply/return) flow of heat energy along the thermal bus, the mathematical model of the main equipment applied for the source, pipe network, load and storage was established. The optimization model with the lowest system operation cost was proposed considering the fuel cost, the external electricity purchase fee and the satisfaction degree of all users' energy demand. The operation cost and energy consumption of the regional energy system scheme and the traditional distributed energy system scheme are studied by a practical case study. The results showed that the new scheme reduces the operating cost by 21.5% and 16.8% respectively under the typical weekly scenarios of cooling in summer and heating in winter. When no storage equipment was used, the new scheme reduced the amount of purchased electricity in summer and winter by 4.1% and 5.2% respectively.
Annals of Operations Research, 2003
District heating plants are becoming more common in European cities. These systems make it possible to furnish users with warm water while locating the production plants in the outskirts having the double benefit of lowering the impact of pollution on the center of the city and achieving better conversion performances. In order to amortize the costs throughout the year, the system often includes a combined heat and power (CHP) plant, to exploit the energy during the summer as well, when the demand for warm water decreases. A linear ...
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The aim of this work is to propose a tool for the design assistance of District Heating Network (DHN) at the beginning of an urban project, as well as for an extension of an existing network. Two goals of DHN optimization are handling at the same time: the optimization of the configuration (network layout, choice between the different production technologies, existence or not of such utilities) and the optimization of the design (mass flow rate, temperature, thermal generating capacity to install, area of the heat exchanger-HX-in sub-station...). The optimization objective is to minimize the global cost of the DHN over 30 years. It includes both operating cost (heating and pumping cost) and investment cost (line, trench, heating plant, HX). The formulation of the optimization problem leads to a mixed integer non-linear programming (MINLP) problem. That means the optimization problem has a single nonlinear objective function (the global cost) subject to numerous linear and nonlinear ...
Modelling of the District Heating System's Operation
Scientific Journal of Riga Technical University. Environmental and Climate Technologies, 2011
The development of a district heating systems calculation model means improvement in the energy efficiency of a district heating system, which makes it possible to reduce the heat losses, thus positively affecting the tariffs on thermal energy. In this paper, a universal approach is considered, based on which the optimal flow and temperature conditions in a district heating system network could be calculated. The optimality is determined by the least operational costs. The developed calculation model has been tested on the Ludza district heating system based on the technical parameters of this system.
Optimization of district heating systems based on the demand forecast in the capital region
Korean Journal of Chemical Engineering, 2009
A district heating system (DHS) consists of energy suppliers and consumers, heat generation and storage facilities and power transmission lines in the region. DHS has taken charge of an increasingly important role as the energy cost increases recently. In this work, a model for operational optimization of the DHS in the metropolitan area is presented by incorporating forecast for demand from customers. In the model, production and demand of heat in the region of Suseo near Seoul, Korea, are taken into account as well as forecast for demand using the artificial neural network. The optimization problem is formulated as a mixed integer linear programming (MILP) problem where the objective is to minimize the overall operating cost of DHS. The solution gives the optimal amount of network transmission and supply cost. The optimization system coupled with forecast capability can be effectively used as design and longterm operation guidelines for regional energy policies.
A linear programming based model for strategic management of district heating systems
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This paper is devoted to the development of a decision support system that could assist district heating authorities in strategic management of their asset. Such a tool is designed in order to answer a variety of questions asked by concerned stakeholders regarding the future of a district heating (DH) system about optimal plant and fuel choice, possible network extension, valorisation of heat surplus, etc. The kernel of this system is a simulation model which determines the energy balance of a given DH network, over any type period. The time period is cut into different time steps, assuming steady state on each time step. At each time step, a linear programming LP based approach is used in order to compute the optimal combination of heat power at the plants to meet the demand. The modelling problem is formulated on a graph and LP as the search for minimum energy production cost rooted at the sources.
Energy consumption and economic analyses of a district heating network
Energy, 2013
An approach for minimisation of the capital costs and energy consumption in a district heating network is presented using a case study based on a district heating network in South Wales, UK. A number of different design cases were simulated using the PSS SINCAL, taking into account different supply and return temperatures and target pressure losses. The operation of the district heating network was synthesised under different design cases using four district heating operating strategies. Optimisation was conducted to obtain the optimal flow rate and supply temperature for the variable flow and variable supply temperature operating strategy. The optimisation model was formulated using the FICOÔ Xpress optimisation suite. The objective of optimisation was to minimise the annual total energy consumption and costs. Using each operating strategy, the annual pump energy consumption, heat losses and the equivalent annual cost were found and compared. A variable flow and variable supply temperature operating strategy was found to be beneficial in all cases. Design cases with minimum annual total energy consumption and cost used small pipe diameters and large pressure drops. Further, by increasing temperature difference between supply and return pipes, the annual total energy consumption and the equivalent annual cost were reduced.
A Review of District Heating Systems: Modeling and Optimization
The ever-increasing demand for heating in different sectors, along with more preventative regulations on greenhouse emissions, has forced different countries to seek new alternatives to heat buildings such as district heating system (DHS). Although rudiments of DHSs can be observed over the centuries, it was not widely implemented until last two decades when the DHS became a strategy to design more energy-efficient way of heating the buildings. This paper suggests a new approach in categorizing DHSs based on their geographical location, scale, heat density, and end-user demand. Furthermore, this paper reviews system and component modeling approaches with a focus on DHS load prediction. Main limitations of the existing methods are also addressed and discussed with a comprehensive review of the recent studies. Finally, the state of the art in optimization of the different DHSs has been reviewed and categorized based on their objective functions and the techniques used for solving optimization problems (deterministic and heuristic).
2013
The present paper is focused on the optimization of combined heat and power distributed generation systems. In particular, the authors describe a mixedinteger linear programming model that has been developed in order to optimally design and operate an energy system in a limited urban area where buildings are equipped with small-size CHP plants and are connected by a heat distribution network; in the proposed model a multi-objective function is optimized, since capital and operating costs, as well as CO 2 emissions, are taken into account. The model has a general validity even if the results reported in the present paper are relative to the case study represented by a residential and tertiary district in the city of Arenzano in the North of Italy. Furthermore, a comparative study has been done in order to quantify the benefits, in terms of economic saving and CO 2 emission reduction, of having a combined heat and power distributed generation system in buildings in spite of using boilers to produce heat and of buying electricity from the grid.