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This study evaluated the impact of the urban heat island (UHI) in the Tokyo metropolitan area on energy consumption in the residential and commercial sectors. Although there are many indications that UHIs increase energy consumption by air conditioners, the possible decrease in consumption of heating energy in winter is usually ignored. To quantify the net impact of a UHI, it is crucial to consider...
A novel heat pipe photovoltaic/thermal (PV/T) system that could simultaneously supply electrical and thermal energy was proposed. Compared with a traditional water-type PV/T system, the heat pipe PV/T system can be used in cold regions without becoming frozen. A dynamic model of the heat pipe PV/T system was presented, and a test rig was constructed. Experiments were conducted to validate the results...
Uncertainty of performance is an obstacle for greater uptake of many renewable energy technologies that depend on local environmental conditions. The ability to successfully complete involving a groundwater-source heat pumps or other projects using groundwater for heating and cooling is highly dependent on local geological conditions. Use of geostatistical information on aquifer properties and analysis...
The recently developed entransy theory is introduced in this paper to tackle the heat transfer processes in building central chilled water systems so as to improve their energy efficiency. We first divide the irreversible heat transfer processes into four categories: (1) air mixing processes; (2) heat transfer processes between chilled water and air; (3) chilled water mixing processes; and (4) heat...
Vortex tubes are used in many industrial fields as parts for refrigerating machines due to their many intrinsic benefits. Although the use of these types of tubes has become common, the characteristics of energy separation associated with these tubes have yet to be vigorously researched. In this study, a counter-flow type of vortex tube is employed to investigate the energy separation characteristics...
This paper illustrates the benefits of two energy optimization strategies to improve the overall process efficiency of a food defrosting system. First, an off-line energy analysis, including both the effects of the refrigeration cycle and the fan used to control the cooling air temperature and speed, is carried-out. This first approach puts on display an optimal running point of the process for a...
The specific thermal energy consumed by steam driven thermal desalination systems can be decreased significantly by reducing the total entropy rate of steam used per unit mass of distilled water produced in the system. This specific entropy rate can be reduced by using a high pressure, saturated steam at a low specific entropy and high specific enthalpy. However, the temperature of steam that can...
Improvements in the effectiveness of solid phase heat recovery and in the thermodynamic properties of metal oxides are the most important paths to achieving unprecedented thermal efficiencies of 10% and higher in non-stoichiometric solar redox reactors. In this paper, the impact of solid and gas phase heat recovery on the efficiency of a non-stoichiometric cerium dioxide-based H 2 O/CO ...
One can measure “energy quantities” – e.g. joules, BTU, quads – but only at a given scale and within a specific narrative about energy conversions at the time. Therefore, at the moment of generating aggregate indicators, the arithmetic summing of assessments of energy quantities referring to different scales and narratives is meaningless. This paper addresses epistemological problems typical of energy...
The “smart grid” represents one of the greatest potential advances in electricity delivery infrastructure in the past century. While the technologies that collectively comprise the smart grid have existed for decades, the potential for changing the way that electricity is generated, delivered, utilized and priced is revolutionary. Not surprisingly, many countries have undertaken initiatives to rollout...
Black liquor gasification (BLG) is being developed as an alternative technology for energy and chemical recovery in kraft pulp mills. This study compares BLG – with downstream production of DME (dimethyl ether) or electricity – with recovery boiler-based pulping biorefinery concepts for different types of mills. The comparison is based on profitability as well as CO 2 emissions, using different...
The main purpose of this paper is to examine to what extent the widely used energy accounting schemes are useful for dealing with sustainability issues in view of Georgescu-Roegen’s production process and its implications for the evolutionary aspects of the economic process. The first part critically examines the concept of “net energy” in relation to material elements produced and consumed in the...
Bioenergy is one of the most dynamic and rapidly changing sectors of the global energy economy. The use of food crops for conversion to biofuel has been criticized for several reasons, among which its competition with the global food chain. Instead, lignocellulosic substrates are claimed to provide a bioenergy alternative without competing with food demand. This is particularly true when dealing with...
In this paper, the most important energy and exergy characteristics of wind energy were examined. Atmospheric variables as air temperature, humidity and pressure and their effects on the wind turbine output were investigated toward wind energy exploitation. It was shown that these usually disregarded meteorological parameters while planning new WFs (Wind Farms), in fact, do play an important role...
This paper presents the application of a new approach for taking into consideration the variability of the wind resource at different temporal scales (hourly, daily, seasonal, annual) in generating scenarios for energy systems modelling. It is argued that Markov models and auto-regressive models, generally used for synthetic wind speed data generation, do not contain sufficient low-frequency information...
Kinetics of bituminous coal and palm shells were evaluated using thermo-gravimetric analysis under different environments (N 2 /CO 2 /O 2 ). The observed percent mass loss of biomass was higher than mass loss percentage of coal because biomass had higher reactivity and volatile matter content. Ignition temperatures of pure coal, biomass and their blends were also investigated...
Peak electric demand due to cooling load in the Desert Southwest region of the US has been an issue for the electrical energy suppliers. To address this issue, a consortium has been formed between the University of Nevada Las Vegas, Pulte Homes (home builder) and NV Energy (local utility) in order to reduce the peak load by more than 65%. The implemented strategies that were used to accomplish that...
Given concerns about the environmental impacts of fossil fuel use, there is a keen interest in developing a broad range of new energy sources and technologies. This in turn creates a need for metrics that can reliably quantify the costs, benefits, and potential trade-offs of different alternatives. In this paper, we present a definition of a full fuel-cycle metric that is flexibile enough to describe...
To investigate the aerodynamic field, cold airflow experiments were conducted under different boiler loads in a cold small-scale model of a down-fired pulverized-coal 300 MW e utility boiler. At 300 MW e and 250 MW e loads, a deflected flow field appeared in the lower furnace. In contrast, at a 150 MW e load, a U-shaped flow field appeared in regions near the left-...
With a view towards better efficiency in renewable energy utilisation, particularly solar energy, the authors study a long-term solar thermal energy storage based on water absorption by a lithium bromide aqueous solution. After a description of the process, the system dynamic simulation model is detailed and used to investigate the influence of certain parameters (heat exchanger size, solution flow...
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