1,721,047 research outputs found
LNG as vehicle fuel in Italy
No full textNatural gas is considered a clean fuel. It can be used as compressed gas (CNG) or in the liquid phase (LNG). For heavy duty vehicles, particularly fleet vehicles, LNG becomes attractive because of reduced on-board weight and space requirements, thanks to its high energy density. LNG as vehicle fuel is already used both in the US and in Europe. The case of Italy is presented in this paper. An analysis showing strengths, weaknesses, threats and opportunities for the introduction of LNG as vehicle fuel in the Italian market is outlined. The analysis puts in evidence that the main issues to be addressed in order to introduce this new fuel concern the request of necessary authorizations to install any LNG facility and the problem of LNG supply, that can be purchased at regasification terminals or liquefied on site
Experimental evaluation and dynamic simulation of a ground coupled heat pump system
No full textGround coupled heat pump (GCHP) systems are a good alternative to traditional systems for heating and cooling of buildings. A large number of ground coupled heat pump systems have been used in residential and commercial buildings throughout the world due to the attractive advantages of high efficiency and environmental friendliness and a wide range of system configurations is available today. In this paper a real application for an office building is presented. The schematic and main features of the GHCP system under study are outlined. The system was monitored during its operation and experimental data are shown. Moreover a dynamic simulation of the plant was performed by means of TRNSYS and theoretical and experimental results are compared. The main purpose of the paper is to put in evidence the performance of such a system and to compare it with traditional heating/cooling systems. Energy and economic savings with GCHP operation were obtained
Design and energy performance of a ground plate heat exchanger coupled with an heat pump system
No full textGround coupled heat pump systems (GCHP) are a good alternative to traditional systems for heating and cooling buildings. A large number of ground coupled heat pump systems have been used in residential and commercial buildings throughout the world due to the attractive advantages of high efficiency and environmental friendliness and a wide range of system configuration is available today. One of the main aspects that affect GCHP performance is due to the effectiveness of the heat transfer process between the heat exchanger and the surrounding ground.
The aim of this paper is to design and assess the energy performance of a particular horizontal ground heat exchanger characterized by a plate shape. Through a software simulation its influence on the ground is studied and its application to a real case study is evaluated. Finally, hints about technical and economic advantages and drawbacks of this technology are put on evidence
Greenhouse Gas emissions of heavy-duty vehicles fuelled by natural gas
No full textThe aim of the present study is to compare the life cycle, in terms of greenhouse gas (GHG) emissions, of diesel, compressed natural gas (CNG) and liquefied natural gas (LNG) used as fuels for heavy-duty vehicles in the European market (EU-15). We concentrated on the European scenario and on heavy-duty road transport vehicles, given their important incidence on the global emissions of GHG. It is shown that the substitution of diesel with natural gas for this type of vehicles leads to a reduction of GHG emissions of 14% and of 10% respectively for CNG and LNG
Characterization of a mini-channel heat exchanger for a heat pump system
No full textIn this paper a mini-channel aluminum heat exchanger used in a reversible heat
pump is presented. Mini-channel finned heat exchangers are getting more and more interest for
refrigeration systems, especially when compactness and low refrigerant charge are desired.
Purpose of this paper was to characterize the mini-channel heat exchanger used as evaporator
in terms of heat transfer performance and to study the refrigerant distribution in the manifold.
The heat exchanger characterization was performed experimentally by means of a test rig built
up for this purpose. It is composed of an air-to-air heat pump, air channels for the external and
internal air circulation arranged in a closed loop, measurement sensors and an acquisition
system. The overall heat transfer capacity was assessed. Moreover, in order to characterize the
flow field of the refrigerant in the manifold of the heat exchanger, a numerical investigation of
the fluid flow by means of CFD was performed. It was meant to evaluate the goodness of the
present design and to identify possible solutions for the future improvement of the manifold
design
Micro-scale LNG liquefaction plants
No full textThis paper deals with the liquefaction of natural gas by micro-scale plants. The aim of the paper is to describe the possible applications of such plants, focusing on the exploitation of stranded wells. A technical and economic analysis of different liquefaction technologies is performed and the liquefaction cycles considered are Linde cycle, Claude cycle and reverse-Brayton cycle. Additional considerations on Mixed Refrigerant Cycles and liquefaction by liquid nitrogen vaporization are reported. Moreover an overview on the competitors technologies (Gas-To-Liquid, Gas-To-Hydrate, Compressed Natural Gas and power generation) is presented in order to understand the most suitable for each given application. Final results of the analysis show the guidelines for economic feasibility of micro-scale liquefaction
State of the art of thermal storage for demand side management
No full textThermal energy storage (TES) is widely recognized as a means to integrate renewable energies into the
electricity production mix on the generation side, but its applicability to the demand side is also possible.
In recent decades, TES systems have demonstrated a capability to shift electrical loads from high-peak to
off-peak hours, so they have the potential to become a powerful instrument in demand-side management
programs (DSM). Thermal storage is a technology that ensures energy security, efficiency and environmental
quality. Of particular interest are applications where TES systems help manage the mismatch
between availability of renewable electricity and the demand for electricity in buildings where hot water,
heating and cooling are delivered by heat pumps and air conditioning for example. Thus this paper demonstrates
the state of the art of present applications of thermal storage for demand-side management. A
particular focus of this work is the attention paid to the characteristics of DSM and their relationship to
different thermal storage systems. If TES effectiveness for the abovementioned applications is demonstrated,
TES devices have a small percentage of the potential market. Therefore challenges and guidelines
for a development plan are suggested
Domestic Demand-Side Management (DSM): Role of Heat Pumps and Thermal Energy Storage (TES) systems
No full textHeat pumps are seen as a promising technology for load management in the built environment, in combination with the smart grid concept. They can be coupled with thermal energy storage (TES) systems to shift electrical loads from high-peak to off-peak hours, thus serving as a powerful tool in demand-side management (DSM). This paper analyzes heat pumps with radiators or underfloor heating distribution systems coupled with TES with a view to showing how a heat pump system behaves and how it influences the building occupants’ thermal comfort under a DSM strategy designed to flatten the shape of the electricity load curve by switching off the heat pump during peak hours (16:00-19:00). The reference scenario for the analysis was Northern Ireland (UK). The results showed that the heat pump is a good tool for the purposes of DSM, also thanks to the use of TES systems, in particular with heating distribution systems that have a low thermal inertia, e.g. radiators. It proved possible to achieve a good control of the indoor temperature, even if the heat pump was turned off for 3 hours, and to reduce the electricity bill if a “time of use” tariff structure was adopted
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