Auxiliary Boiler Research Articles

Dynamic model of solar heating plant with seasonal thermal energy storage

The article focuses on existing technologies developed to harvest and store solar irradiance as a source of primary energy in district heating systems. In the study particular attention was given to solar collector systems cooperating with seasonal heat storage solutions. Motivating this work was the search for a tool to assess achievable solar fraction ‒ the ratio of usable solar energy to total energy consumption. The outcomes of this work are: (i) a simplified dynamic model facilitating evaluation of the proposed solutions, and (ii) selection of optimal operating parameters of the proposed system.A brief review and discussion is made of the technical and legal limitations on possible investments. The ground rules of cooperation between solar based heat sources with seasonal storage systems and conventional industrial boilers and district heating network have been set out. The work touches on the physical components of the discussed systems. Commercially available solar collectors and heat exchangers are presented and their pros and cons discussed. Some in-depth analysis of seasonal heat storage solutions is provided, in particular on tank and pit thermal energy storage as well as storage solutions that use boreholes or aquifer layers.Examples are given of existing plants characterized by high solar fraction located in the EU region and outside of it. A simplified dynamic model developed in the Aspen Hysys software environment is described and the results discussed. Due to the high complexity of the primary problem, the model has been limited to a solar collector installation, seasonal heat storage system and auxiliary boiler. The results obtained from the model are discussed and future steps are presented in the last part of the article. These recommendations seek to further the development of an efficient way of analysis and commercial assessment of such systems.

Dynamic programming based methodology for the optimization of the sizing and operation of hybrid energy plants

The dynamic programming method is mainly used to deal with energy management and optimal control problems of hybrid energy plants. This paper extends the application of this method and documents the development of a dynamic programming based methodology for the optimization of both the sizing and operation of hybrid energy plants. The optimization problem is carried out with the aim of minimizing primary energy consumption over the simulation period. Moreover, in order to demonstrate the validity and usefulness of the optimization methodology presented in this paper, a comparison with an optimization methodology developed by the same authors is made. The optimization methodology used as a benchmark is based on the genetic algorithm and is commonly used in the literature. A case study consisting of a building located in the north of Italy is considered to demonstrate the developed methodology. The hybrid energy plant used to fulfil the energy demands of the building comprises a photovoltaic panel, solar thermal collector, combined heat and power, ground and air source heat pumps, hot water storage and auxiliary boiler. Compared to the genetic algorithm based methodology, the proposed methodology allows a primary energy saving and computation time saving of about 5.4% and 41%, respectively. In addition, compared to a traditional plant composed of a boiler and the grid, the developed methodology allows a primary energy saving of about 24%. The proposed methodology is fast, easy to implement and also addresses the non-linearity associated with the optimization problem of hybrid energy plants.

Management of renewable‐based multi‐energy microgrids in the presence of electric vehicles

This study proposes a stochastic optimisation programming for scheduling a microgrid (MG) considering multiple energy devices and the uncertain nature of renewable energy resources and parking lot-based electric vehicles (EVs). Both thermal and electrical features of the multi-energy system are modelled by considering combined heat and power generation, thermal energy storage, and auxiliary boilers. Also, price-based and incentive-based demand response (DR) programs are modelled in the proposed multi-energy MG to manage a commercial complex including hospital, supermarket, strip mall, hotel and offices. Moreover, a linearised AC power flow is utilised to model the distribution system, including EVs. The feasibility of the proposed model is studied on a system based on real data of a commercial complex, and the integration of DR and EVs with multiple energy devices in an MG is investigated. The numerical studies show the high impact of EVs on the operation of the multi-energy MGs.

A Novel Design of an Automation System for an Energy-Efficient Polygeneration Plant

Polygeneration plants are a leading means of increasing the efficiency and reducing the environmental impact of energy conversion. This study addresses the lack of studies on automation and control of systems that produce electricity, heating, cooling, and potable water. Mixed integer linear programming (MILP) optimization of the annualized total cost is used to select and size the plant components. The final layout consists of solar photovoltaic (PV) and thermal, an absorption chiller and a multi-effect desalination for electricity, heating, cooling and water, respectively. As auxiliary sources, boiler, gas turbine and grid connection are present. Storage units for electricity, heating, and water are also included in the proposed layout. The control and automation system are implemented using ladder logic. Sufficient supply, efficient resource use, and financial gain are considered in the control scheme design. Applying the methodology to a mixed industrial, commercial and residential zone in Southern Luzon, Philippines, the simulation results show successful implementation of all control scenarios. Economic analysis on the hourly cash flows of the system on a typical day show significant daily savings that outweigh the investment cost of the proposed control and automation system with monthly savings of ₱25,112.40 and payback period of 0.4 years.

Optimization of the hydraulic performance and integration of a heat storage in the geothermal and waste-to-energy district heating system of Ferrara

District heating is an effective way to increase the share of renewables in the thermal energy sector. The district heating network (DHN) of the municipality of Ferrara in northern Italy uses a geothermal reservoir at a depth of 1 km supplying hot water at 100 °C. Besides geothermal energy, the overall annual thermal demand of 170 GWh is covered by a combined heat and power (CHP) plant fed by municipal solid waste (MSW), and by auxiliary natural gas boilers. A short-term thermal energy storage having a useful capacity of 45 MWh decouples the heat production plants from the distribution network. An advanced monitoring and control system has been recently implemented to supply a high-level service to the customers connected to the network, searching for the maximum electricity saving by reducing the supply pressure of the pumping station, and targeting the maximum natural gas saving by a proper production programming of the heat supply plants. The paper describes the main design and operational features of the district heating system, and shows how the improved operation was successful in reducing the electricity and natural gas consumption. The new pressure management consists in monitoring the differential pressure in many substations, especially those located at the periphery of the network, and adjusting the water supply pressure in order to fulfil the minimum differential pressure at the most critical substation. The modified production scheduling consists in keeping using the geothermal energy and waste-to-energy plants in periods of low thermal demand and low electricity prices to daily charge the storage system. Experimental data measured in the first months of improved operation show a high saving potential of electric power for pumping equal to 400 MWh/year, which represents a saving of 30% compared to the previous “manual” optimization of the hydraulic performance. Moreover, the enhanced storage operation enables a saving of 7000 MWh/year of energy from natural gas, which finally contributes for only 11% to the annual heat demand. The calculated payback time of only a few years shows the high cost saving potential of these energy conservation measures in such systems.

A comprehensive stochastic energy management system of micro-CHP units, renewable energy sources and storage systems in microgrids considering demand response programs

Using different types of renewable energy sources considering their uncertainties causes numerous challenges for minimizing the operation cost and maximizing the reliability of system. Hence, stochastic programming is an essential tool to consider the system uncertainties. This paper presents a day-ahead energy management system to decrease the operation cost and increase the reliability of a Microgrid considering a number of challenges for supporting electrical and thermal loads. In the proposed method, micro-CHP units, renewable energy sources, auxiliary boiler and energy storage system are all responsible for supplying the electrical and thermal loads. The problem is formulated as a multi-objective optimization problem. Moreover, the influence of considering the electrical energy storage system as a non-ideal battery with charge/discharge efficiency less than 1 is investigated. Also, demand response programs are provided based on load shifting contracts to consumers. A scenario-based approach is used to cover the uncertainties of renewable energy sources, market price and electrical load. Besides, this paper considers both islanding and grid-connected modes of Microgrid and investigates the influence of demand side management on operation cost and reliability in both modes. The capability of the proposed algorithm is analyzed by simulation results of a 3-feeder Microgrid.

Techno-economic evaluation of a multi effect distillation system driven by low-temperature waste heat from exhaust flue gases

In this study, technical and economical evaluation of a multi effect distillation (MED) system is presented which utilizes the vapor produced from waste heat of exhaust flue gases. In order to recover the waste heat of flue gases, a shell and tube heat exchanger was designed with the Polytetrafluoroethylene (PTFE) material in order to resist corrosion as a result of sulfuric acid formation. Recoverable energy, which is obtained from experimental data, serves as the source of energy required to produce water vapor. Due to high fluctuations in the amount of vapor produced, an auxiliary boiler is employed for its compensation. The vapor which has been produced by the heat exchanger and/or auxiliary boiler, is used as the motive steam in the MED distillation. Economic analysis of MED distillation system driven by low-temperature waste heat is carried out and system payback period based on natural gas saving is obtained. Finally, waste-heat-driven MED distillation system is compared to a conventional MED on the basis of the levelized cost of water (LCOW) at different electrical and natural gas tariffs as well as the real interest rates. Economic evaluation shows that the LCOW is about 1.13–2.9 $/m3.

Ways of reduction of pollution of an environment by ship power installations

In the report are discussed ways of reduction of pollution of an environment by ship power installations. Among them it is necessary to select optimization of regimes of operations of main traditional ship sources of the electric power, the installation of systems of utilization of refuse energy of the exhaust gases and cooling water from main and auxiliary engines, application of new types of sources of the electric power and the using of complex automation and control systems for exhaust gases and for selecting of regimes main engine, auxiliary engine, utilize boiler, auxiliary boiler, shaft generator.

Thermodynamic and economic analysis of solar assisted CCHP-ORC system with DME as fuel

A solar assisted combined cooling, heating and power system coupled with an organic Rankine cycle (SCCHP-ORC) is proposed and investigated via both experimental and simulation methods. The dimethyl ether (DME) is used as the fuel of the proposed system for the prime mover (PM) and auxiliary boiler (AB). DME was chosen based on that it is friendly to the environment and avoids low temperature corrosion. The performance of the proposed system was evaluated during typical summer and winter days via a case study using thermodynamic and economic methods. The results show that the proposed system followed by the electricity load (FEL) strategy can satisfy most of the electricity demand. The cooling and heating profiles are supplied by utilizing the PMs’ cooling water and the parabolic trough collector (PTC). Additionally, the released energy from a thermal energy storage (TES) can significantly reduce the need for grid energy during peak load hours. Moreover, the efficiency of the proposed SCCHP-ORC system is higher than that of original system by 9.87%. The minimum values of carbon dioxide emission saving ratio are of 58.14% during summer and 17.32% during winter. The total amount of carbon dioxide saved are 778.7 kg/day during a typical summer day and 358.7 kg/day during a typical winter day duo to the technologies selected in this system. Besides, the sensitivity analysis shows that the changed electricity price has a largest impact on the payback period ranging from 4.0 year to 6.5 year.

Accident Cases Involving Marine Auxiliary Boilers

Accident Cases Involving Marine Auxiliary Boilers

Combined Heat and Power Generation Systems Design for Residential Houses

Nowadays cogeneration is recognized as one of the most effective techniques to meet the increasingly stringent requirements regarding energy efficiency increase and energy saving in buildings. In this context, the aim of this study is the definition of reference parameters for the optimal energy systems design in residential applications. To this purpose, a generation scenario with cogeneration units, heat pumps, auxiliary boilers and chillers (both compression and absorption machines) has been set for the fulfillment of residential users’ needs (in terms of electrical, thermal and cooling loads). For a given number of involved households, commercial cogeneration units have been selected, sized on the basis of the electrical peak need, and the generation scenario has been optimized by an in-house developed software, obtaining the optimal energy systems design and operation. Then, a parametric analysis has been carried out varying the number of considered households in order to define the optimal range of the energy systems size. In particular, specific values in terms of installed power for household and installed power for unitary peak load have been determined. For completeness, an economic analysis has been finally carried out for the evaluation of the return on investment and of the differential net present value – with respect to a standard generation scenario (only natural gas boilers for thermal needs fulfillment and electricity purchase from the grid for electrical and cooling needs) – considering a time horizon of ten years.

Neural Network-based modeling methodologies for energy transformation equipment in integrated steelworks processes

The paper proposes a methodology for modeling of energy transformation equipment which are commonly found in integrated steelworks, mainly focusing on steam production in the Basic Oxygen Furnace and auxiliary boilers, the electric power production in off-gas expansion turbines and some relevant steam and electricity consumers. The modeling approach is based on standard neural networks and Echo State Networks (ESN) for forecasting the variables of interest. All the models are intended as processes predictors to be used in a hierarchical control strategy based on multi-period and multi-objective optimization techniques and model predictive control. The overall target is the optimization of the re-use of off-gas produced in integrated steelworks by minimizing costs and maximizing revenues. Training and validation of models have been carried out by exploiting real historical data provided by steelmaking companies and have been successful tested.

Short-Term Scheduling Strategy for Wind-Based Energy Hub: A Hybrid Stochastic/IGDT Approach

This paper evaluates the scheduling problem for energy hub system consisting of wind turbine, combined heat and power units, auxiliary boilers, and energy storage devices via hybrid stochastic/information gap decision theory (IGDT) approach. Considering that energy hub plays an undeniable role as the coupling among various energy infrastructures, still it is essential to be investigated in both modeling and scheduling aspects. On the other hand, penetration of wind power generation is significantly increased in energy infrastructures in recent years. In response, this paper aims to focus on the hybrid stochastic/IGDT optimization method for the optimal scheduling of wind integrated energy hub considering the uncertainties of wind power generation, energy prices and energy demands explicitly in a way that not only global optimal solution can be reached, but also volume of computations can be lighten. In addition, by the proposed hybrid model, the energy hub operator can pursue two different strategies to face with price uncertainty, i.e., risk-seeker strategy and risk-averse strategy. This method optimizes energy hub scheduling problem in uncertain environment by mixed-integer nonlinear programming. This formulation is proposed to minimize the expected operation cost of energy hub where different energy demands of energy hub would be efficiently met. The forecast errors of uncertainties related to wind power generation and energy demands are modeled as a scenario, while an IGDT optimization approach is proposed to model electricity price uncertainty.

Усовершенствование системы управления рециркуляцией дымовых газов судового вспомогательного котла

Усовершенствование системы управления рециркуляцией дымовых газов судового вспомогательного котла

Assigning machinery power values for estimating ship exhaust emissions: Comparison of auxiliary power schemes

While ship exhaust emissions can be calculated at both large scales and fine resolutions due to the availability of activity data from the Automatic Identification System, there are still uncertainties in the assignment of ship engine and boiler power, which then leads to uncertainties in the estimated emissions. Reliable information is usually available for main engines, including engine type and installed power, and physical models exist for estimating propulsive power requirements. However, similar models are not available for estimating auxiliary power requirements. This study examines methods for calculating the actual operating power of auxiliary engines and auxiliary boilers. Earlier approaches assumed that installed auxiliary engine power increased in proportion to installed main engine power. Auxiliary-to-main engine power ratios were specified by ship type, and load factors were specified by ship type and operating mode. Auxiliary boiler power was generally not differentiated by ship size. More recent approaches are based on extensive ship survey data, and give tables of auxiliary engine and auxiliary boiler power binned against ship type, ship size and operating mode. These surveys show that auxiliary power does not necessarily increase with ship size or main engine power. A revised approach based on the recent data sources is adopted and applied to a case study of four ports in southeast Australia. The revised approach is informed by a local survey of ships to investigate auxiliary power demand. Comparisons are made of the impact of the different approaches on the magnitude and spatial distribution of the emissions.

Hydronic design of cogeneration in collective residential heating systems: state-of-the-art, comparison and improvements

Cogeneration (CHP) has great potential to save primary energy in collective residential buildings. However, these savings and their associated financial benefits are influenced by the design of the complete heat production system, which typically includes, besides the CHP itself, an auxiliary boiler and a storage tank. Both scientific literature and design guides focus little on the hydronic aspects of that design, although the performance of a heat production system is extremely prone to it.Therefore, this paper evaluates different hydronic designs of a central heat production system with CHP. First, an overview is given of the state-of-the-art hydronic design concepts that are used in the private sector. Two new concepts are proposed as improvements to the existing ones: one to integrate the CHP and one to integrate the boiler. A morphological chart is developed to classify the features of both the conventional and novel designs. Second, the performance of all the design concepts (and their 54 combinations) are evaluated based on a case study of an apartment block with 24 apartments. This evaluation is made by means of dynamic building system simulations.The results show that maximal primary energy can be saved if the CHP is integrated according to the novel CHP design, which allows a variable flow rate through the CHP. This concept should be preferred in a design process. Multiple hydronic configurations of the boiler, of which one is the novel hydronic boiler concept, resulted in a similar performance. Therefore, designers are advised to make a case-specific comparison to decide which one to take. The morphological chart and methodology elaborated in this paper provide a basis to make that decision.

Optimal Scheduling of Hybrid Energy Resources for a Smart Home

The present environmental and economic conditions call for the increased use of hybrid energy resources and, concurrently, recent developments in combined heat and power (CHP) systems enable their use at a domestic level. In this work, the optimal scheduling of electric and gas energy resources is achieved for a smart home (SH) which is equipped with a fuel cell-based micro-CHP system. The SH energy system has thermal and electrical loops that contain an auxiliary boiler, a battery energy storage system, and an electrical vehicle besides other typical loads. The optimal operational cost of the SH is achieved using the real coded genetic algorithm (RCGA) under various scenarios of utility tariff and availability of hybrid energy resources. The results compare different scenarios and point-out the conditions for economic operation of micro-CHP and hybrid energy systems for an SH.

Operational Characteristic of Selected Marine Turbounits Powered by Steam from Auxiliary Oil-Fired Boilers

Abstract This paper presents characteristic values and operational parameters of two selected marine auxiliary steam turbine units such as efficiency, and steam consumption per unit or per hour. For the purpose of the analysis, the cargo turbine pumps and turbogenerator have been selected. The characteristic values and operational parameters have been determined using the operational tests results for the turbounits installed on oil tankers at various power loads.

Off-design heating/power flexibility for steam injected gas turbine based CCHP considering variable geometry operation

Owing to the fluctuating energy demand from consumer side, combined cooling, heating and power (CCHP) system operates at off-design condition most of the time. Moreover, the heating/power surplus is a common problem for the conventional CCHP system. In order to improve the precision of performance prediction and partly relieve the heating surplus, a steam injected gas turbine (STIG) based CCHP system considering off-design condition is proposed. The system consists of a steam injected gas turbine, double-pressure heat recovery steam generator (HRSG), heat exchanger, absorption chiller and auxiliary boiler. Two different operation strategies including turbine inlet temperature (TIT) strategy and variable guide vanes (VGVs) strategy, are illustrated to access the part-load performance of gas turbine and CCHP system. The performance indicators, like primary energy saving rate (PESR), primary energy rate (PER) are set up to evaluate the thermodynamic performance of the CCHP system. A simple gas turbine (SGT) based CCHP is chosen as the comparative object and two energy demand cases are selected to validate the advancement. The results show that VGVs strategy does not improve the gas turbine efficiency significantly but bring more exhaust heat into HRSG. VGVs strategy advances the heating to power ratio, PESR and PER around the whole part load condition, i.e., PESR is elevated from 0.3254 to 0.3743 by VGVs at the half of gas turbine load without injected steam. Injecting steam is a more effective way to improve gas turbine efficiency rather than using VGVs strategy while implementing same gas turbine load. Steam injection does not always enhance the PESR, but the PER keeps decreasing as injected steam flow increases around the whole load. STIG based CCHP system with VGVs operation strategy gets the best performance among these studied approaches, and the maximum enhancement of PESR reaches 0.3171 in the proposed energy demand cases.

Methodology for determining the design radiation for a PTC heating system based on non-guaranteed days

Solar heating, as an alternative technology to coal-fired heating, could significantly alleviate the air pollution in China. The value of design radiation should be carefully determined when designing a solar system, as it would commonly affect the solar collector area, and then the economics and performance of the system. However, in the existing publications, most studies ignore the influence of the daily and seasonal variation of radiation, and commonly choose the fixed value of design radiation in some typical days, leading to a non-optimal performance of the system with unreasonable setting parameters. To solve this problem in the design stage, a method is proposed to determine the design radiation of a parabolic trough collector (PTC) heating system. In this method, the concept of non-guaranteed days is introduced to quickly and conveniently determine the system rated capacity. Additionally, the cost of unit heating supply is employed in this method as an optimized object of the heating system. Based on the proposed method, a case study for four typical solar radiation districts in China is conducted. Firstly, the design radiation values of each district are decided through the proposed method. Then, the relationship between non-guaranteed days and the initial investment of the system under the optimal design radiation is obtained. Finally, the economic analysis of the PTC system in Mentougou (suburbs of Beijing) is performed. This work could be a practical guide to select the design radiation for a PTC heating system without the auxiliary boiler. Moreover, the method could also be applied to more types of solar systems and regions.