Switched Linear Model of a Stratified Hot Water Tank for Control of Micro-CHP Systems

2019 ◽  
Author(s):  
Trevor Bird ◽  
Catherine Weaver ◽  
Neera Jain
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Waste Heat ◽  
Cell Model ◽  
Internal Heat ◽  
Temperature Inversion ◽  
Hot Water ◽  
Water Tank ◽  
Switched Linear System

Abstract We present a switched linear system approach for modeling the complex nonlinear dynamics associated with temperature inversion occurring in thermally stratified hot water tanks. Such tanks are commonly used for thermal energy storage, particularly in low- to medium-temperature waste heat recovery applications. By separating the influence of temperature inversion from the internal heat transfer between states in the governing differential equations, we paramaterize the nonlinearity using a vector of discrete variables. This vector is then used to define the switching between a set of linear, discrete time models. The proposed switched model is validated against a reduced-order nonlinear model of the thermal energy storage and then integrated with a fuel cell model to capture the dynamics of a micro-combined heat and power system. Simulation results demonstrate the importance that temperature inversion has on the stratification dynamics which in turn has implications for control of such systems.

scholarly journals Energy and Exergy Analysis of Sensible Thermal Energy Storage—Hot Water Tank for a Large CHP Plant in Poland

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4842 ◽  
Author(s):  
Ryszard Zwierzchowski ◽  
Marcin Wołowicz
Keyword(s):  
Energy Storage ◽  
Ambient Temperature ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Exergy Analysis ◽  
Hot Water ◽  
Water Tank ◽  
Exergy Destruction ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis

The paper contains a simplified energy and exergy analysis of pumps and pipelines system integrated with Thermal Energy Storage (TES). The analysis was performed for a combined heat and power plant (CHP) supplying heat to the District Heating System (DHS). The energy and exergy efficiency for the Block Part of the Siekierki CHP Plant in Warsaw was estimated. CHP Plant Siekierki is the largest CHP plant in Poland and the second largest in Europe. The energy and exergy analysis was executed for the three different values of ambient temperature. It is according to operation of the plant in different seasons: winter season (the lowest ambient temperature Tex = −20 °C, i.e., design point conditions), the intermediate season (average ambient temperature Tex = 1 °C), and summer (average ambient temperature Tex = 15 °C). The presented results of the analysis make it possible to identify the places of the greatest exergy destruction in the pumps and pipelines system with TES, and thus give the opportunity to take necessary improvement actions. Detailed results of the energy-exergy analysis show that both the energy consumption and the rate of exergy destruction in relation to the operation of the pumps and pipelines system of the CHP plant with TES for the tank charging and discharging processes are low.

scholarly journals Parametric Cost Optimization of Solar Systems with Seasonal Thermal Energy Storage for Buildings

2021 ◽  
Vol 246 ◽  
pp. 03003
Author(s):  
Willy Villasmil ◽  
Marcel Troxler ◽  
Reto Hendry ◽  
Philipp Schuetz ◽  
Jörg Worlitschek
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Cost Optimization ◽  
Hot Water ◽  
Water Tank ◽  
Existing Building ◽  
Solar Systems ◽  
Living Space ◽  
Solar Fraction

In combination with seasonal thermal energy storage (STES), solar energy offers a vast potential for decarbonizing the residential heat supply. In this work, a parametric optimization is conducted to assess the potential of reducing the costs of water-based STES through the use of alternative thermal insulation materials and the integration of an underground storage outside the building. The investigated configurations include: a hot-water tank, a solar collector installation, and a multifamily building with a solar fraction of 100%. The storage is either integrated inside the building or buried underground in its direct vicinity. A simulation-based analysis shows that if the tank is integrated inside an existing building (as part of a retrofitting action) – where costs are primarily driven by the loss of living space – vacuum-insulation panels can lead to significant savings in living space and a cost advantage compared to the use of conventional glass wool. Nevertheless, storage integration inside an existing building is a more expensive option compared to an external integration due to the high costs associated to the internal building modification and loss of living space. Despite the high excavation costs and increased heat losses, the concept of burying the storage underground is a promising option to allow the integration of large-volume seasonal storage systems in new and existing buildings.

Experimental Testing of a Thermoelectric-Based Hydronic Cooling and Heating Device With Transient Charging of Sensible Thermal Energy Storage Water Tank

2008 ◽  
Author(s):  
Michael J. Kazmierczak ◽  
Sreenidhi Krishnamoorthy ◽  
Abhishek Gupta
Keyword(s):  
Energy Storage ◽  
Heat Exchanger ◽  
Heat Pump ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage Tank ◽  
Hot Water ◽  
System Component ◽  
Water Tank ◽  
Te Modules

Experiments were performed to charge either cold or hot water thermal energy storage tanks using a heat exchanger equipped with multiple thermoelectric (TE) modules. The primary objective was to design a simple, but effective, modular Peltier heat pump system component to provide chilled or hot water for domestic use at the appliance level, and when arranged in multiple unit combinations, a system that can potentially satisfy small home cooling and heating requirements. Moreover, when the TEs are directly energized using solar PV panels, the system provides a renewable, pollution free and off-the-grid solution to supplement home energy needs. The present work focuses on the design and testing of a thermoelectric heat exchanger component that consists of two water channels machined from two aluminum plates with an array of three or five thermoelectric modules placed in between to transiently cool and/or heat the water in the thermal energy storage tank. The water passing over either the cold or hot side of the TE modules is recirculated to charge the cold or hot thermal storage tank, respectively. The temperatures in the prototype Peltier heat exchanger test component and thermal energy water storage tank were measured during both cold tank charging and hot tank charging operation. The thermal efficiencies of TE heat pump cooling/heating system are reported. The effects of TE power input, number of TE units and rate of fluid flow are studied.

Experimental Testing of a Thermoelectric-Based Hydronic Cooling and Heating Device With Transient Charging of Sensible Thermal Energy Storage Water Tank

2009 ◽  
Vol 1 (4) ◽  
Author(s):  
Michael J. Kazmierczak ◽  
Sreenidhi Krishnamoorthy ◽  
Abhishek Gupta
Keyword(s):  
Energy Storage ◽  
Heat Exchanger ◽  
Heat Pump ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage Tank ◽  
Hot Water ◽  
System Component ◽  
Water Tank ◽  
Te Modules

Experiments were performed to charge either cold or hot water thermal energy storage tanks using a heat exchanger equipped with multiple thermoelectric (TE) modules. The primary objective was to design a simple, but effective, modular Peltier heat pump system component to provide chilled or hot water for domestic use at the appliance level, and when arranged in multiple unit combinations, a system that can potentially satisfy small home cooling and heating requirements. Moreover, when the TEs are directly energized using solar photovoltaic (PV) panels, the system provides a renewable, pollution-free, and off-the-grid solution to supplement home energy needs. The present work focuses on the design and testing of a thermoelectric heat exchanger component that consists of two water channels machined from two aluminum plates with an array of three, five, or eight thermoelectric modules placed in between to transiently cool and/or heat the water in the thermal energy storage tank. The water passing over either the cold or hot side of the TE modules is recirculated to charge the cold or hot thermal storage tank, respectively. The temperatures in the prototype Peltier heat exchanger test component and thermal energy water storage tank were measured during both cold and hot tank charging operations. The thermal efficiencies of the TE heat pump cooling/heating system are reported. The effects of the TE power input, number of TE units, rate of fluid flow, and heat sink/source temperature are studied.

Control of a Supercritical CO2 Electro-Thermal Energy Storage System

2013 ◽  
Author(s):  
S. A. Wright ◽  
A. Z’Graggen ◽  
J. Hemrle
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Waste Heat ◽  
Storage System ◽  
Electrical Energy ◽  
Hot Water ◽  
Working Fluid ◽  
Heat Rejection ◽  
Plant Uses

Transcritical CO2 power systems are being investigated for site independent electro-thermal energy storage (ETES). The storage plant uses electrical energy with a standard vapor-compression heat pump/refrigeration cycle to store thermal energy as hot water and ice over a period of approximately 8 hours during low power demand. The power cycle is then reversed and operated as a simple Rankine cycle to produce ∼100 MWe for about 4.5 hours during peak demand. During the power generation cycle the storage plant uses the heat stored in the hot water tanks, together with ice melting, plus ambient heat rejection for the heat sink. For 100 MWe class power plants, the round trip efficiency is estimated to be up to 60%. CO2 was selected as the working fluid because it improves the ability of the plant to operate with high reversibility. In addition, it is compact and can operate below the freezing point of water. This report describes the major control characteristics of the plant, together with methods, tools, and results of the model. Because the plant is nearly “closed”, it must operate only by consuming electrical energy during the charging cycle and by producing electrical energy plus some waste heat during the discharge cycle. All other heat transfer processes occurs solely within the storage plant itself and consists of either heating or cooling water and by making or melting ice. For the plant to operate continuously, both the water thermal storage and ice storage must be returned to their initial conditions after every 24 hour period. Otherwise, small changes in the thermal environment during waste heat rejection or performance variations of internal components will cause the storage system to drift from its designed operating temperature, pressure and energy storage capability, challenging its ability to operate. The control concept for the storage plant addresses both the operation of the plant during charging and discharging. It also addresses strategies for control during off-design situations or due to disturbances such as load following or changes in ambient heat rejection conditions. The process simulations described in the paper include models for the main physical components of the plant including the turbomachinery, the heat exchanger network, states of charge of the cold and hot storage, and CO2 inventory.

scholarly journals Distributed Thermal Energy Storage Configuration of an Urban Electric and Heat Integrated Energy System Considering Medium Temperature Characteristics

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2924
Author(s):  
Wei Wei ◽  
Yusong Guo ◽  
Kai Hou ◽  
Kai Yuan ◽  
Yi Song ◽  
...  
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Internal Heat ◽  
Configuration Model ◽  
Electric Heater ◽  
Heat Network ◽  
Release Process ◽  
Medium Temperature ◽  
Temperature Characteristics

Distributed thermal energy storage (DTES) provides specific opportunities to realize the sustainable and economic operation of urban electric heat integrated energy systems (UEHIES). However, the construction of the theory of the model and the configuration method of thermal storage for distributed application are still challenging. This paper analyzes the heat absorption and release process between the DTES internal heat storage medium and the heat network transfer medium, refines the relationship between heat transfer power and temperature characteristics, and establishes a water thermal energy storage and electric heater phase change thermal energy storage model, considering medium temperature characteristics. Combined with the temperature transmission delay characteristics of a heat network, a two-stage optimal configuration model of DTES for UEHIES is proposed. The results show that considering the temperature characteristics in the configuration method can accurately reflect the performance of DTES, enhance wind power utilization, improve the operation efficiency of energy equipment, and reduce the cost of the system.

scholarly journals Self-Sufficiency and Energy Savings of Renewable Thermal Energy Systems for an Energy-Sharing Community

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4284
Author(s):  
Min-Hwi Kim ◽  
Youngsub An ◽  
Hong-Jin Joo ◽  
Dong-Won Lee ◽  
Jae-Ho Yun
Keyword(s):  
Renewable Energy ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Energy Systems ◽  
Hot Water ◽  
Pump System ◽  
Ground Source Heat Pumps ◽  
Self Sufficiency ◽  
Energy Sharing

Due to increased grid problems caused by renewable energy systems being used to realize zero energy buildings and communities, the importance of energy sharing and self-sufficiency of renewable energy also increased. In this study, the energy performance of an energy-sharing community was investigated to improve its energy efficiency and renewable energy self-sufficiency. For a case study, a smart village was selected via detailed simulation. In this study, the thermal energy for cooling, heating, and domestic hot water was produced by ground source heat pumps, which were integrated with thermal energy storage (TES) with solar energy systems. We observed that the ST system integrated with TES showed higher self-sufficiency with grid interaction than the PV and PVT systems. This was due to the heat pump system being connected to thermal energy storage, which was operated as an energy storage system. Consequently, we also found that the ST system had a lower operating energy, CO2 emissions, and operating costs compared with the PV and PVT systems.

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