Energies

Research

18 pages, 8328 KiB

Open AccessArticle

Phase Change Material Based Accumulation Panels in Combination with Renewable Energy Sources and Thermoelectric Cooling

by Jan Skovajsa, Martin Koláček and Martin Zálešák

Energies 2017, 10(2), 152; https://doi.org/10.3390/en10020152 - 24 Jan 2017

Cited by 34 | Viewed by 8185

The article deals with the use of modern materials and technologies that can improve the thermal comfort in buildings. The article describes the design and usage of a special accumulation device, which is composed of thermal panels based on phase change materials (PCMs). [...] Read more.

The article deals with the use of modern materials and technologies that can improve the thermal comfort in buildings. The article describes the design and usage of a special accumulation device, which is composed of thermal panels based on phase change materials (PCMs). The thermal panels have an integrated tube heat exchanger and heating foils. The technology can be used as a passive or active system for heating and cooling. It is designed as a “green technology”, so it is able to use renewable energy sources, e.g., photovoltaic (PV) panels, solar thermal collectors and heat pumps. Moreover, an interesting possibility is the ability to use thermoelectric coolers. In the research, measurements of the different operating modes were made, and the results are presented in the text. The measurement approves that the technology improves the thermal capacity of the building, and it is possible to use it for active heating and cooling. Full article

(This article belongs to the Special Issue Advanced Heating and Cooling Techniques)

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16 pages, 3742 KiB

Open AccessArticle

Research on a Household Dual Heat Source Heat Pump Water Heater with Preheater Based on ASPEN PLUS

by Xiang Gou, Yang Fu, Imran Ali Shah, Yamei Li, Guoyou Xu, Yue Yang, Enyu Wang, Liansheng Liu and Jinxiang Wu

Energies 2016, 9(12), 1026; https://doi.org/10.3390/en9121026 - 3 Dec 2016

Cited by 22 | Viewed by 6956

Abstract

This article proposes a dual heat source heat pump bathroom unit with preheater which is feasible for a single family. The system effectively integrates the air source heat pump (ASHP) and wastewater source heat pump (WSHP) technologies, and incorporates a preheater to recover [...] Read more.

This article proposes a dual heat source heat pump bathroom unit with preheater which is feasible for a single family. The system effectively integrates the air source heat pump (ASHP) and wastewater source heat pump (WSHP) technologies, and incorporates a preheater to recover shower wastewater heat and thus improve the total coefficient of performance (COP) of the system, and it has no electric auxiliary heating device, which is favorable to improve the security of the system operation. The process simulation software ASPEN PLUS, widely used in the design and optimization of thermodynamic systems, was used to simulate various cases of system use and to analyze the impact of the preheater on the system. The average COP value of a system with preheater is 6.588 and without preheater it is 4.677. Based on the optimization and analysis, under the standard conditions of air at 25 °C, relative humidity of 70%, wastewater at 35 °C, wastewater flow rate of 0.07 kg/s, tap water at 15 °C, and condenser outlet water temperature at 50 °C, the theoretical COP of the system can reach 9.784 at an evaporating temperature of 14.96 °C, condensing temperature of 48.74 °C, and preheated water temperature of 27.19 °C. Full article

(This article belongs to the Special Issue Advanced Heating and Cooling Techniques)

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16 pages, 6144 KiB

Open AccessArticle

Experimental Investigation of Thermal Behaviors in Window Systems by Monitoring of Surface Condensation Using Full-Scale Measurements and Simulation Tools

by Goopyo Hong, Daeung Danny Kim and Byungseon Sean Kim

Energies 2016, 9(11), 979; https://doi.org/10.3390/en9110979 - 22 Nov 2016

Cited by 6 | Viewed by 5546

Abstract

The aim of the present study was to investigate the thermal performance of window systems using full-scale measurements and simulation tools. A chamber was installed on the balcony of an apartment to control the temperatures which can create condensation on the interior surfaces [...] Read more.

The aim of the present study was to investigate the thermal performance of window systems using full-scale measurements and simulation tools. A chamber was installed on the balcony of an apartment to control the temperatures which can create condensation on the interior surfaces of window systems. The condensation process on the window was carefully scrutinized when outdoor and indoor temperature and indoor relative humidity ranged from −15 °C to −20 °C, 23 °C to 24 °C, and 50% to 65%, respectively. The results of these investigations were analyzed to determine how the moisture is influenced by changing temperatures. It appears that the glass-edge was highly susceptible to the temperature variations and the lowest temperature on the glass edge was caused by the heat transfer through the spacer, between the two glass panels of the window. The results from the simulation used in this study confirm that the thermal performance of window systems can be improved the use of super insulated or thermally broken spacers. If the values of the indoor humidity and temperature are given, then the outdoor temperature when condensation forms can be obtained by using Temperature Difference Ratio (TDR). This methodology can be employed to predict the possible occurrence of condensation. Full article

(This article belongs to the Special Issue Advanced Heating and Cooling Techniques)

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9 pages, 3793 KiB

Open AccessArticle

Performance Characteristics of PTC Elements for an Electric Vehicle Heating System

by Yoon Hyuk Shin, Seung Ku Ahn and Sung Chul Kim

Energies 2016, 9(10), 813; https://doi.org/10.3390/en9100813 - 11 Oct 2016

Cited by 46 | Viewed by 8353

Abstract

A high-voltage positive temperature coefficient (PTC) heater has a simple structure and a swift response. Therefore, for cabin heating in electric vehicles (EVs), such heaters are used either on their own or with a heat pump system. In this study, the sintering process [...] Read more.

A high-voltage positive temperature coefficient (PTC) heater has a simple structure and a swift response. Therefore, for cabin heating in electric vehicles (EVs), such heaters are used either on their own or with a heat pump system. In this study, the sintering process in the manufacturing of PTC elements for an EV heating system was improved to enhance surface uniformity. The electrode production process entailing thin-film sputtering deposition was applied to ensure the high heating performance of PTC elements and reduce the electrode thickness. The allowable voltage and surface heat temperature of the high-voltage PTC elements with thin-film electrodes were 800 V and 172 °C, respectively. The electrode layer thickness was uniform at approximately 3.8 μm or less, approximately 69% less electrode materials were required compared to that before process improvement. Furthermore, a heater for the EV heating system was manufactured using the developed high-voltage PTC elements to verify performance and reliability. Full article

(This article belongs to the Special Issue Advanced Heating and Cooling Techniques)

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13 pages, 2837 KiB

Open AccessArticle

Monitoring and Analysing Changes in Temperature and Energy in the Ground with Installed Horizontal Ground Heat Exchangers

by Pavel Pauli, Pavel Neuberger and Radomír Adamovský

Energies 2016, 9(8), 555; https://doi.org/10.3390/en9080555 - 28 Jul 2016

Cited by 9 | Viewed by 4099

Abstract

The objective of this work was to monitor and analyse temperature changes in the ground with installed linear and Slinky-type horizontal ground heat exchangers (HGHEs), used as low-potential heat pump energy sources. Specific heat flows and specific energies extracted from the ground during [...] Read more.

The objective of this work was to monitor and analyse temperature changes in the ground with installed linear and Slinky-type horizontal ground heat exchangers (HGHEs), used as low-potential heat pump energy sources. Specific heat flows and specific energies extracted from the ground during the heating season were also measured and compared. The verification results showed that the average daily ground temperatures with the two HGHEs are primarily affected by the temperature of the ambient environment. The ground temperatures were higher than ambient temperature during most of the heating season, were only seldom below zero, and were higher by an average 1.97 ± 0.77 K in the ground with the linear HGHE than in the ground with the Slinky-type HGHE. Additionally, the specific thermal output extracted from the ground by the HGHE was higher by 8.45 ± 16.57 W/m² with the linear system than with the Slinky system. The specific energies extracted from the ground over the whole heating season were 110.15 kWh/m² and 57.85 kWh/m² for the linear and Slinky-type HGHEs, respectively. Full article

(This article belongs to the Special Issue Advanced Heating and Cooling Techniques)

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15 pages, 7433 KiB

Open AccessArticle

Experimental Study of Natural Convection Cooling of Vertical Cylinders with Inclined Plate Fins

by Jong Bum Lee, Hyun Jung Kim and Dong-Kwon Kim

Energies 2016, 9(6), 391; https://doi.org/10.3390/en9060391 - 24 May 2016

Cited by 11 | Viewed by 8045

Abstract

In this paper, natural convection from vertical cylinders with inclined plate fins is investigated experimentally for use in cooling electronic equipment. Extensive experimental investigations are performed for various inclination angles, fin numbers, and base temperatures. From the experimental data, a correlation for estimating [...] Read more.

In this paper, natural convection from vertical cylinders with inclined plate fins is investigated experimentally for use in cooling electronic equipment. Extensive experimental investigations are performed for various inclination angles, fin numbers, and base temperatures. From the experimental data, a correlation for estimating the Nusselt number is proposed. The correlation is applicable when the Rayleigh number, inclination angle, and fin number are in the ranges 100,000–600,000, 30°–90°, and 9–36, respectively. Using the correlation, a contour map depicting the thermal resistance as a function of the fin number and fin thickness is presented. Finally, the optimal thermal resistances of cylinders with inclined plate fins and conventional radial plate fins are compared. It is found that that the optimal thermal resistance of the cylinder with inclined fins is 30% lower than that of the cylinder with radial plate fins. Full article

(This article belongs to the Special Issue Advanced Heating and Cooling Techniques)

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11 pages, 3983 KiB

Open AccessArticle

Performance Characteristics of a Modularized and Integrated PTC Heating System for an Electric Vehicle

by Yoon Hyuk Shin, Seungkyu Sim and Sung Chul Kim

Energies 2016, 9(1), 18; https://doi.org/10.3390/en9010018 - 28 Dec 2015

Cited by 29 | Viewed by 12117

Abstract

A modularized positive temperature coefficient heating system has controller-integrated heater modules. Such a heating system that uses a high-voltage power of 330 V was developed in the present study for use in electric vehicles. Four heater modules and one controller with an input [...] Read more.

A modularized positive temperature coefficient heating system has controller-integrated heater modules. Such a heating system that uses a high-voltage power of 330 V was developed in the present study for use in electric vehicles. Four heater modules and one controller with an input power of 5.6 kW were integrated in the modularized system, which was designed for improved heating power density and light weight compared to the conventional heating system, in which the controller is separated. We experimentally investigated the performance characteristics, namely, the heating capacity, energy efficiency, and pressure drop, of a prototype of the developed heating system and found it to have satisfactory performance. The findings of this study will contribute to the development of heating systems for electric vehicles. Full article

(This article belongs to the Special Issue Advanced Heating and Cooling Techniques)

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14 pages, 3386 KiB

Open AccessArticle

A Numerical Study on System Performance of Groundwater Heat Pumps

by Jinsang Kim and Yujin Nam

Energies 2016, 9(1), 4; https://doi.org/10.3390/en9010004 - 23 Dec 2015

Cited by 19 | Viewed by 6391

Abstract

Groundwater heat pumps have energy saving potential where the groundwater resources are sufficient. System Coefficients of Performance (COPs) are measurements of performance of groundwater heat pump systems. In this study, the head and power of submersible pumps, heat pump units, piping, and heat [...] Read more.

Groundwater heat pumps have energy saving potential where the groundwater resources are sufficient. System Coefficients of Performance (COPs) are measurements of performance of groundwater heat pump systems. In this study, the head and power of submersible pumps, heat pump units, piping, and heat exchangers are expressed as polynomial equations, and these equations are solved numerically to determine the system performance. Regression analysis is used to find the coefficients of the polynomial equations from a catalog of performance data. The cooling and heating capacities of water-to-water heat pumps are determined using Energy Plus. Results show that system performance drops as the water level drops, and the lowest flow rates generally achieve the highest system performance. The system COPs are used to compare the system performance of various system configurations. The groundwater pumping level and temperature provide the greatest effects on the system performance of groundwater heat pumps along with the submersible pumps and heat exchangers. The effects of groundwater pumping levels, groundwater temperatures, and the heat transfer coefficient in heat exchanger on the system performance are given and compared. This analysis needs to be included in the design process of groundwater heat pump systems, possibly with analysis tools that include a wide range of performance data. Full article

(This article belongs to the Special Issue Advanced Heating and Cooling Techniques)

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16 pages, 1959 KiB

Open AccessArticle

Optimal Operation of Combined Heat and Power System Based on Forecasted Energy Prices in Real-Time Markets

by Chenghong Gu, Da Xie, Junbo Sun, Xitian Wang and Qian Ai

Energies 2015, 8(12), 14330-14345; https://doi.org/10.3390/en81212427 - 18 Dec 2015

Cited by 23 | Viewed by 5414

Abstract

This paper develops a discrete operation optimization model for combined heat and powers (CHPs) in deregulated energy markets to maximize owners’ profits, where energy price forecasting is included. First, a single input and multi-output (SIMO) model for typical CHPs is established, considering the [...] Read more.

This paper develops a discrete operation optimization model for combined heat and powers (CHPs) in deregulated energy markets to maximize owners’ profits, where energy price forecasting is included. First, a single input and multi-output (SIMO) model for typical CHPs is established, considering the varying ratio between heat and electricity outputs at different loading levels. Then, the energy prices are forecasted with a gray forecasting model and revised in real-time based on the actual prices by using the least squares method. At last, a discrete optimization model and corresponding dynamic programming algorithm are developed to design the optimal operation strategies for CHPs in real-time. Based on the forecasted prices, the potential operating strategy which may produce the maximum profits is pre-developed. Dynamic modification is then conducted to adjust the pre-developed operating strategy after the actual prices are known. The proposed method is implemented on a 1 MW CHP on a typical day. Results show the optimized profits comply well with those derived from real-time prices after considering dynamic modification process. Full article

(This article belongs to the Special Issue Advanced Heating and Cooling Techniques)

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