Site Utility Systems Research Articles

Blockchain-based concept for total site heat integration: A pinch-based smart contract energy management in industrial symbiosis

Industrial symbiosis has gained prominence in pursuing sustainable industrial practices, aiming to optimise resource utilisation and reduce environmental impacts. A critical aspect of this endeavour is the efficient management of energy resources within an industrial ecosystem. This paper presents a novel approach to enhance Total Site Heat Integration (TSHI) implementations by employing Blockchain as a facilitator for decentralised energy management. TSHI is an efficient and widely applied method for industrial symbiosis concerning energy flows, which employs the steam mains in site utility systems as the platform for exchanging heat between industrial processes at various temperature levels. It is shown that the synergy of Pinch Analysis and Smart Contract technologies is capable of facilitating energy integration of processes belonging to independent market actors, compared with the currently dominant integration inside a single company. The proposed framework leverages Blockchain as a distributed ledger to enable secure, transparent, and automated energy management across multiple industrial entities in an industrial symbiotic network. The integration of Pinch Analysis principles ensures that the Heat Integration process is optimised to improve the overall energy efficiency. Smart contracts enable automatic negotiation and execution of energy transactions based on predefined rules, minimising the time lag for concluding deals on energy resource exchange and conservation. This paper examines several scenarios to illustrate the implementation of the proposed Blockchain-based TSHI concept within an industrial symbiosis network. It is demonstrated that up to 16 % cost savings are possible by simply enabling transparency via Blockchain. The results could drive innovative development to revolutionise decentralised energy management in a complex industrial ecosystem, especially by synchronising energy exchanges in time.

Optimization of site utility systems for renewable energy integration

Considerable attention has been paid to the electrified energy supply based on renewable energy for achieving carbon-neutrality. A systematic and integrated approach is required to identify optimal operating strategies for the integration of electrified energy sources with conventional utility systems and to understand the techno-economic impact of using renewable energy on industrial energy management. Renewable-integrated industrial utility systems are modeled, which is optimized to investigate economic trade-off between capital investment, fuel consumption, power generation, and CO2 emission tax. Sensitivity of key design parameters is examined with the optimization framework, which allows to gain conceptual understanding on the economic impact of CO2 emission tax and prices of renewable electricity on site-wide heat and power management. Compared to the utility system based on the combustion of fossil fuels only, the operating cost of renewable-integrated system in the case study can be reduced about 14% in the operating cost and 9% in the capital cost through the strategic import of 20 MWe renewable electricity. The presented case studies fully illustrate economic impacts related to the implementation of renewable electricity to industrial utility systems and demonstrate the benefit of process-integrated optimization for renewable energy integration in practice.

E-Site Analysis: Process Design of Site Utility Systems With Electrification for Process Industries

A new design methodology for the process synthesis of electrified energy systems, e-site analysis, for the application of process industries, is presented, which allows the systematic selection of electrified units in process levels and provides design guidelines for the configuration of site utility systems. Different characteristics associated with the use of power-to-heat technologies for thermal heating, compared with traditional heat supply from the combustion of fossil fuels, are discussed in the context of process design and site-wide utility management. The new design framework is developed for the transformation of conventional steam-based utility systems to electricity-based ones. The applicability of the proposed design method and its benefits from carbon-neutral energy generation is demonstrated with a case study, which clearly illustrates the impact of electrification on the design and operation of site utility systems in process industries.

New Procedure for Optimal Integration of Steam Power Plant With Process Site Utility to Produce Power, Steam, and Freshwater

Abstract Steam power plants are usually used for producing electricity and can simultaneously work as a multigeneration plant to produce steam, freshwater, and power. This study performed the optimal combination of a steam power station as the source and a site utility system as the sink of power and steam. Approximating the potential of the cogeneration before designing a central utility system for site utility systems is vital to set goals for onsite fuel demand along with power, freshwater, and steam production. For this purpose, a precise and efficient cogeneration targeting strategy was utilized to couple a site utility of a process and a steam power plant. This study proposed a novel strategy for optimal designing integrated steam power plants and site utility consisting of process station industries. Accordingly, exergy, exergoenvironmental, and exergoeconomic analyses were conducted. The environmental impacts of life cycle assessment (LCA) in exergoenvironmental analysis were apportioned to the exergy streams, pointing out the key factors of the system with the most significant impact on the environment and possible improvements related to them. Besides, the water cycle algorithm (WCA) was employed to optimize the integrated plant. The capabilities of the proposed procedure were implemented to the petrochemical complex site utility and steam power plant. The results showed that an optimum solution was achieved using the new procedure with significantly reduced computation time.

A New Algorithm for the Design of Site Utility for Combined Production of Power, Freshwater, and Steam in Process Industries

Abstract Site utility, without a doubt, is one of the major units in process industries that consumed a lot of fossil fuels and significantly emitted emission pollution. In this paper, a systematic procedure was proposed to optimize the utility system's design and integration based on a targeting approach as process integration technique, exergetic, exergoeconomic, exergoenvironmental analysis associated with life cycle assessment (LCA), and multi-objective optimization through water cycle and genetic algorithms. Total site analysis was performed to provide an essential understanding of the equipment's characteristics and interactions in the site utility system. It also aims for power production and the temperature of the boiler and each steam level with acceptable accuracy. Furthermore, the exergetic, exergoeconomic, and exergoenvironmental analyses were presented to declare the effects of irreversibility, economic, and environmental impacts on the system. In this paper, to show the proposed method's applicability, the optimal design of a site utility associated with a petrochemical complex has been considered. First, the optimal design is performed based on minimization of total annualized costs (TAC) as one-objective function through star software, genetic algorithm (GA), water cycle algorithm (WCA), proposed GA, and proposed WCA method. In the next phase, the optimal design is done based on MOGA, MOWCA, proposed MOGA, and proposed MOWCA methods based on maximum exergetic efficiency, and freshwater production, and minimization of exergetic cost, and total environmental exergetic impact. Results show by using the new procedure, the optimum solution has been achieved by a significant reduction of computational time.

Total Site Utility System Structural Design Using P-graph

This paper explores the macro optimisation decisions of energy sources selection and the structural design of the utility system within the framework of Total Site Heat Integration (TSHI). Most TSHI research on utility systems focuses on optimisation of conventional Combined Heat and Power systems. To build a new Utility Systems Planner (USP) tool, P-graph has been selected as the optimisation tool. A critical element of USP is the inclusion of low-grade heat utilisation technologies within the considered superstructure. The USP outputs include the optimal structure of the utility system including the arrangement and size of each component and estimates for Greenhouse Gas and Water Footprints. The successful application of the USP to a representative industrial case study with district energy integration shows an optimal solution with a natural gas boiler, reciprocating gas engine, condensing economiser, steam turbine, thermocompressor, organic Rankine cycle, cooling tower, and electric chiller with a total cost of 14.893 M€/y. The new tool is a platform for launching further research including site-specific application, multi-period optimisation, and sensitivity analysis.

Cogeneration Improvement Based on Steam Cascade Analysis

In site utility systems, very high pressure (VHP) steam is generated from fuel combustion in boilers and gas turbines heat recovery steam generators. VHP steam is distributed to lower pressure steam mains to satisfy process heating demand. The steam cascade in the utility system is determined by utility VHP steam from boilers, process heating and cooling demands, and process indirect heat recovery through the utility medium. Utility power is generated by fuel combustion in gas turbines and steam expansion or condensation in steam turbines. Steam mains selection, process heating and cooling demands, and process indirect heat recovery affect utility VHP steam target, the steam cascade and cogeneration. This work presents an extended graphical approach based on steam cascade analysis to explore how steam mains selection influences cogeneration improvement. The interaction among process heating and cooling demands, processes indirect heat recovery, and utility targets of VHP steam demand and cooling medium are quantified graphically. This graphical method would be helpful to scope the potential cogeneration improvement by variation of steam mains. The insights gained can be used to simplify the optimization of the utility system.

A generic algorithm of sustainability (GAS) function for industrial complex steam turbine and utility system optimisation

The GAS-function methodology is introduced in this paper in order to identify the sustainability objective function for optimisation of multiple interconnected complex steam turbines and utility network (ICSTUN) systems. Also, the complex steam turbine was modelled based on induction machine operation which enhances its performance. The boiler models were identified as the sustainability objective function which was further investigated under given operating constraints for optimisation of the ICSTUN system. The validated results show that relative error between field operation and simulation data were less than 1% on average, which is acceptable for engineering applications. The optimisation results indicate that contrary to previous authors' results and by comparing with actual field operational data information, coal flow rates for total site utility system of this investigated ICSTUN can be significantly reduced. It was therefore concluded that a significant reduction in the coal flow rate amounts is practicable in order to significantly reduce operating costs as well as the environmental and social issues associated with utilising fossil-fuels, while still satisfying the demand-side management objectives for the plant.

Footprint Reduction Strategy for Industrial Site Operation

Industrial sites efficiency and Footprints (FPs) are determined to an extent by the choices made in the Site Utility Systems, which supply the necessary process heating, cooling and power to the core site processes. While the methods for energy efficiency targeting have matured and there are studies evaluating the FPs resulting from utility system operation, a method providing guidance on the measures for FP reduction still need more development. Building upon the previous developments in utility system optimisation, energy targeting and FP analysis, this contribution combines them with the use of FP intensity indicators and analysis of the contributions of the system components to the resulting FPs, to devise a strategy and procedure for reducing the FP values. The obtained results indicate that the fundamental factor-indicator analysis, combined with the exploitation of the structural system links – e.g. the energy-water nexus manifestation, it is possible to achieve significant FP reductions in synergy with potential economic gains.

New procedure for determination of availability and reliability of complex cogeneration systems by improving the approximated Markov method

There are two procedures to solve reliability problems: analytical techniques and stochastic simulation. Each has advantages and disadvantages. One of the important analytical techniques for repairable systems is the Markov method. This method uses state space to consider all states that may occur. To use this method for complex systems, the model of the system must be simplified. For this purpose, many states are removed from the space state. In this way, although the probabilities of the states are calculated, these probabilities are often not accurate. In the present work, a new approach is proposed that considers both the simplified system and the calculation of the probability of each state accurately. The new method can calculate the probabilities by taking into account minimum states. Site utility systems are used to illustrate the procedure for applying this method. Site utilities have several repairable components (e.g. steam turbine, gas turbine, HRSG, de-aerator, boiler). So, this system can generate a large and complex state space for which it is difficult to calculate the probability. The new procedure can reduce the number of states and aggregates of the exploded state space due to the high number of components. The results show that the new procedure can predict state probabilities with high accuracy.

Targeting the cogeneration potential for Total Site utility systems

It is important to target the cogeneration potential of utility systems in the process of designing or retrofitting Total Site utility systems. Simulation software has been widely used in process design and analysis. However, it is rarely employed in estimating of the cogeneration potential of a utility system. A new method is presented in this paper for targeting the cogeneration potential of Total Site utility systems with a commercial software. The simulator is used to calculate the temperatures of steam mains, steam flowrates and shaft power rates. Shaft power generation by steam turbines in expansion zones are computed with the built-in simulation module. Compared to the existing approaches, the new method needs neither establishing iterative calculation, nor programming procedure, and it requires fewer parameters. For the illustrated case studies, the results obtained by this method are comparable to those obtained in the literature. It is shown that the calculation procedure proposed in this paper is simple, and the results obtained are accurate. In addition, the calculation of the steam turbine capital cost and environmental footprints are considered in the targeting procedure to provide decision makers with a more complete picture of the designed sites. This should allow them to efficiently screen and compare the major design options on the basis of both economic and environmental performance.

Techno-economic analysis of combined heat and power generation systems with regard to solar energy for lubricant oil refinery utilization

ABSTRACTThe heat and power demands are supplied by site utility systems. One way of increasing efficiency and reducing energy consumption in process is optimizing site utility. This paper aims to investigate transient modeling and optimization of site utility systems with regard to solar energy. This model calculates steam supply, steam flow rate for site demand, and power generated by the gas engine and steam turbines with the objective function of maximizing total revenue. By the use of this model, in a site utility of refinery, the amounts of gas engine fuel consumption, power generated, cogeneration efficiency, and total revenue will increase and boiler fuel consumption will decrease. Using heat recovery equipment to recover exhaust gas energy of engine, conformity of steam supply and demand and reduction in the amount of steam letdown are the reasons that cause to reduce boiler fuel consumption and increase cogeneration efficacy. Finally, the great advantage in combination of conventional system with the use of solar energy as parabolic trough concentrator is evaluated by a transient model.

Energy and economic analysis of an integrated solid oxide fuel cell system with a total site utility system: A case study for petrochemical utilization

ABSTRACTProviding utilities needed in the site with lowest cost and highest efficiency is one of the main concerns of the process industries owners. Over a case study in this research, the total site utility system was optimized at first and then energy and economic analysis of solid oxide fuel cell (SOFC) system was performed. Next, integration of the fuel cell with total site utility system was evaluated during two scenarios: first, steam supply through heat recovery steam generator (HRSG) of gas turbine (heat follow), and second supply of the entire generated power of gas turbine. According to the evaluation conducted, if it is aimed to supply the entire steam generated by HRSG of gas turbine, it will be more cost-effective to select SOFC system in this regard. So if the goal is to change the gas turbine system into SOFC system, system selection will be done based on supply of the entire steam generated using HRSG. In this case, 10 SOFC systems will be required by which about 27.56 MW power can be generated.

Comparative study of energy saving potential for heavy chemical complex by area-wide approach

The thought of single site approach for energy saving in a site has been evolved to that of area-wide approach which considers multiple sites together as if they were a single entity. In area-wide approach, R-curve analysis plays an important part to evaluate the energy efficiency of the site utility system for utilizing high temperature heat, which is possible to identify energy saving potential and understand the characteristics of the utility system. R-curve analysis was applied to Mizushima complex, one of the ten largest heavy chemical complexes in Japan, and identified the characteristics and the energy saving potential for the whole of the complex. In area-wide approach, low-grade heat utilization for energy saving is also important. Total site profile analysis was used to evaluate the possibility of low-grade heat utilization. Mizushima complex was evaluated for the characterization by comparison of its energy saving potential to that of another heavy chemical complex, Chiba. It was found that the energy saving potential of Mizushima complex was twice in R-curve analysis than that of Chiba complex. This meant that the equipment in the utility system in Mizushima complex performed less efficiency than that in Chiba complex.

A mixed integer linear programming model for integrating thermodynamic cycles for waste heat exploitation in process sites

Thermodynamic cycles such as organic Rankine cycles, absorption chillers, absorption heat pumps, absorption heat transformers, and mechanical heat pumps are able to utilize wasted thermal energy in process sites for the generation of electrical power, chilling and heat at a higher temperature. In this work, a novel systematic framework is presented for optimal integration of these technologies in process sites. The framework is also used to assess the best design approach for integrating waste heat recovery technologies in process sites, i.e. stand-alone integration or a systems-oriented integration. The developed framework allows for: (1) selection of one or more waste heat sources (taking into account the temperatures and thermal energy content), (2) selection of one or more technology options and working fluids, (3) selection of end-uses of recovered energy, (4) exploitation of interactions with the existing site utility system and (5) the potential for heat recovery via heat exchange is also explored. The methodology is applied to an industrial case study. Results indicate a systems-oriented design approach reduces waste heat by 24%; fuel consumption by 54% and CO2 emissions by 53% with a 2year payback, and stand-alone design approach reduces waste heat by 12%; fuel consumption by 29% and CO2 emissions by 20.5% with a 4year payback. Therefore, benefits from waste heat utilization increase when interactions between the existing site utility system and the waste heat recovery technologies are explored simultaneously.The case study also shows that the novel methodology can select and design optimal solutions for waste heat exploitation which are technically, economically and environmentally feasible from a range of technology options, heat sources and end-uses of recovered energy.

Site utility system optimization with operation adjustment under uncertainty

Utility systems must satisfy process energy and power demands under varying conditions. The system performance is decided by the system configuration and individual equipment operating load for boilers, gas turbines, steam turbines, condensers, and let down valves. Steam mains conditions in terms of steam pressures and steam superheating also play important roles on steam distribution in the system and power generation by steam expansion in steam turbines, and should be included in the system optimization. Uncertainties such as process steam power demand changes and electricity price fluctuations should be included in the system optimization to eliminate as much as possible the production loss caused by steam power deficits due to uncertainties. In this paper, uncertain factors are classified into time-based and probability-based uncertain factors, and operation scheduling containing multi-period equipment load sharing, redundant equipment start up, and electricity import to compensate for power deficits, have been presented to deal with the happens of uncertainties, and are formulated as a multi-period item and a recourse item in the optimization model. There are two case studies in this paper. One case illustrates the system design to determine system configuration, equipment selection, and system operation scheduling at the design stage to deal with uncertainties. The other case provides operational optimization scenarios for an existing system, especially when the steam superheating varies. The proposed method can provide practical guidance to system energy efficiency improvement.

Application of R-curve analysis in evaluating the effect of integrating renewable energies in cogeneration systems

Because of their higher efficiency, cogeneration systems are widely used in many industrial plants. Moreover, due to concerns about environmental issues, replacing conventional fossil fuels with clean and sustainable energy resources seems inevitable. In This paper, the effect of integrating renewable energy resources in cogeneration systems is investigated. As will be demonstrated, integration of these resources can either improve or deteriorate the performance of the cogeneration system. Therefore, R-Curve tool is used for a detailed analysis on the effect of integrating renewable energies on the performance of the cogeneration system. Different scenarios for integration of solar and wind power as well as solar heat are investigated. Also, a new benchmarking index is proposed as a comparison tool for integration of renewables into total site utility systems. Finally, three cases are studied using the proposed concepts. As the results suggest, with the same renewable system, there is a considerable difference between savings for different scenarios of integration. Accordingly, as an example, integration of a 13 MW solar power plant can be associated with either 53 or 4 MW of fuel saving in the same cogeneration system based on the operating state.

New procedure for design and exergoeconomic optimization of site utility system considering reliability

An examination is reported of the effects of equipment reliability on the exergoeconomic analysis and optimization of a site utility system. A new procedure is proposed that incorporates a hybrid method that has several advantages over the commonly used approach. The steam network design has a significant impact on the utility system, and the availability of steam mains is taken into account. An analysis of the availability of system components identifies components that can affect system operation. For this purpose, the state-space and the continuous Markov methods are incorporated in thermoeconomic analysis to improve the economic costs. Additionally, the design and optimization of utility systems potentially involve a large number of alternatives that, if properly designated, can yield significant savings in total costs. In this regard, the proposed new procedure addresses the optimal design of site utility systems. Tools applied to assist process integration include total site analysis, site utility grand composite curves (SUGCCs), the cogeneration targeting method and exergoeconomic analysis. Furthermore, multi-objective exergoeconomic optimization is performed using a genetic algorithm based on hybrid techniques in order to determine optimum solutions. The applicability of the proposed procedure is tested using STAR® software through a case study for grassroot problem.

Evaluating the potential of process sites for waste heat recovery

As a result of depleting reserves of fossil fuels, conventional energy sources are becoming less available. In spite of this, energy is still being wasted, especially in the form of heat. The energy efficiency of process sites (defined as useful energy output per unit of energy input) may be increased through waste heat utilisation, thereby resulting in primary energy savings.In this work, waste heat is defined and a methodology developed to identify the potential for waste heat recovery in process sites; considering the temperature and quantity of waste heat sources from the site processes and the site utility system (including fired heaters and, the cogeneration, cooling and refrigeration systems). The concept of the energy efficiency of a site is introduced – the fraction of the energy inputs that is converted into useful energy (heat or power or cooling) to support the methodology. Furthermore, simplified mathematical models of waste heat recovery technologies using heat as primary energy source, including organic Rankine cycles (using both pure and mixed organics as working fluids), absorption chillers and absorption heat pumps are developed to support the methodology. These models are applied to assess the potential for recovery of useful energy from waste heat.The methodology is illustrated for an existing process site using a case study of a petroleum refinery. The energy efficiency of the site increases by 10% as a result of waste heat recovery. If there is an infinite demand for recovered energy (i.e. all the recoverable waste heat sources are exploited), the site energy efficiency could increase by 33%. The methodology also shows that combining technologies into a system creates greater potential to exploit the available waste heat in process sites.

Techno-economic optimization of IGCC integrated with utility system for CO2 emissions reduction—Simultaneous heat and power generation from IGCC

An integrated gasification combined cycle (IGCC) may be used to generate steam and power while providing a capture-ready CO2 stream. This work addresses techno-economic optimization of an IGCC integrated with the utility system for a process site, with the aim of cost-effective reduction of CO2 emissions. The IGCC can generate power and produce steam in parallel with the site utility system; integration of the IGCC into the site utility system means that the heat recovered from the IGCC is fed to the utility system, where it is used to generate steam to meet site heat and power demand. A relatively rigorous simulation model of the IGCC is applied to explore steam and power generation opportunities for various fuel flow rates. A simple, linear model is regressed from these simulation results to correlate fuel consumption and steam and power generation by the IGCC. The simple model is integrated into a model for simulation and optimization of the site utility system; the operating conditions of the overall system (IGCC and site utility system) can then be optimized to minimize the operating cost, taking into account the capacity and efficiency of equipment such as boilers and steam turbines, the cost of fuel, the cost or value of power, and costs associated with CO2 emissions. The proposed optimization method is illustrated by application to an industrially relevant case study. The results indicate that integrating an IGCC with a site utility system can provide an effective route for cogeneration of heat and power with low carbon emissions and low operating costs, although the economic benefits are sensitive to fuel, power and emissions-related costs.