Search results for " EFFICIENCY"

Energy efficient optimisation for large-scale multiple-antenna system with WPT

2018

In this study, an energy-efficient optimisation scheme for a large-scale multiple-antenna system with wireless power transfer (WPT) is presented. In the considered system, the user is charged by a base station with a large number of antennas via downlink WPT and then utilises the received power to carry out uplink data transmission. Novel antenna selection, time allocation and power allocation schemes are presented to optimise the energy efficiency of the overall system. In addition, the authors also consider channel state information cannot be perfectly obtained when designing the resource allocation schemes. The non-linear fractional programming-based algorithm is utilised to address the …

Boosting Long-Term Stability of Pure Formamidinium Perovskite Solar Cells by Ambient Air Additive Assisted Fabrication

2021

Due to the high industrial interest for perovskite-based photovoltaic devices, there is an urgent need to fabricate them under ambient atmosphere, not limited to low relative humidity (RH) conditions. The formamidinium lead iodide (FAPI) perovskite α-black phase is not stable at room temperature and is challenging to stabilize in an ambient environment. In this work, we show that pure FAPI perovskite solar cells (PSCs) have a dramatic increase of device long-term stability when prepared under ambient air compared to FAPI PSCs made under nitrogen, both fabricated with N-methylpyrrolidone (NMP). The T80 parameter, the time in which the efficiency drops to 80% of the initial value, increases f…

The effect of balconies on energy efficiency of multi-unit residential buildings: A state of art review

2019

Multi-unit residential buildings (MURBs) has become common in urban areas in order to accommodate the demands of the increasing urban population and make use of limited urban land. These buildings are high consumers of energy and natural resources with significant carbon footprints. Efforts are hence needed to make new and existing MURBs more energy efficient and environmentally. Balconies in MURBs can help decrease operational energy in addition to providing a connection to the outdoor environment for the residents. If properly designed, MURBs balconies in cold climates can help in enhancing solar gains while in warm climates, they can be useful in providing a sub-space capable of cooling …

Design of Reliable and Efficient Banki-Type Turbines

2020

A new shape for the external surface of the Crossflow turbine blades is proposed, which allows for the preservation of hydraulic efficiency in spite of a significant maximum blade thickness providing mechanic robustness and reliability. The final shape of the blades is assessed using an iterative solution for two uncoupled models: a 2D computational fluid dynamic (CFD) and a structural 3D finite element method (FEM) analysis of a single blade. Application of the proposed methodology to the design of a power recovery system (PRS) turbine, a new backpressure Crossflow-type inline turbine for pressure regulation, and energy production in a real Sicilian site follows.

Energy conversion efficiency in betavoltaic cells based on the diamond Schottky diode with a thin drift layer

2020

The HPHT diamond Schottky diode was assembled as a Metal/Intrinsic/p-doped structure betavoltaic cell (BC) with a very thin (1 μm) drift layer and tested under 5–30 keV electron beam irradiation using a scanning electron microscope (SEM). The effect of the β-radiation energy and the backscattering of electrons on the energy conversion was studied. From the results obtained, it is shown that, the efficiency of the investigated BC increases from 1.01 to 3.75% with the decrease of β-particle energy from 30 to 5 keV due to an increase of the electron beam absorption in a thin drift layer. Maximum efficiency is achieved when the electron beam energy is close to the average β-decay energy of 3H. …

Wireless Charging Systems for Electric Vehicle Batteries

Interspecific extrinsic and intrinsic competitive interactions in egg parasitoids

2012

Interspecific competitive interactions can occur either between adult parasitoids searching/exploiting hosts (extrinsic competition) or between parasitoid larvae developing within the same host (intrinsic competition). Understanding how interspecific competition between parasitoids can affect pest suppression is important for improving biological pest control. The purpose of this work was to review both extrinsic and intrinsic competition between egg parasitoid species. These are organisms that are often candidates for biological control programs due to their ability to kill the pest before the crop feeding stage. We first reviewed the literature about interspecific competitive abilities of…

Measurement of Photosynthesis and Transpiration in Spruce Trees with Various Degrees of Damage

1987

Summary In the context of a project on physiological and biochemical characterization of spruce with different degrees of damage, the C02 and H2O gas exchange of 22-year-old spruce from a location in the Hunsru.ck (West Germany) were measured in summer 1985. The measurements were carried out on shoots from 1984 and were set up as a pair comparison, i.e. the measurement data of a tree with symptoms of damage were always compared with a tree in the immediate vicinity which phenotypically showed less damage. Diurnal course measurements in the open air revealed a marked reduction of photosynthesis depending on the degree of damage of the trees. If one plots photosynthetic rate against light int…

Solar radiation for buildings and energy applications: the feasibility of the reduced data set for Mediterranean sites

2007

In the last years several computer programs for thermal simulation of buildings have been quickly spread; they allow to describe the thermal behavior of buildings and to verify their energy efficiency, in order to suggest eventual improvements as from the design stage. Most of these simulation tools generally need a complete input data set and, in particular, information referring to the climatic conditions of the site where buildings will be built-up. As it is well known, among climatic issues, particularly important for the thermal energy balance is the solar radiation. In this paper authors present a short reference year of the solar radiation, more precisely the Monthly Average Day (MAD…

Current characterisation for ultra low power wireless body area networks

2010

The emerging area of body area networks (BAN) imposes challenging requirements on hardware and software to achieve the desired lifetimes for certain devices such as long term medical implants. In this paper, we propose a novel approach to the measurement and characterisation of the energy consumption of BAN devices. The approach uses a low cost energy auditing circuit and addresses the problem of accurately measuring low-level current consumption. This new technique will allow precise and analytical measurements of systems and components in terms of energy. This will help circuit designers minimise power consumption in BAN devices. Software engineers might use this approach to validate and …