Renewable energy applications in desalination: state of the art

Millions of people have no access to a secure source of fresh water. Nevertheless, since many arid regions are coastal areas, seawater desalination is a reasonable alternative. On the other hand, the energy requirements of desalination processes are high. Then, the energy supply in low development countries or isolated areas may be a problem, especially if electricity is required. Since most arid regions have high renewable energy resources, the use of renewable energies in seawater desalination exhibits an interesting chance, or even the only way to offer a secure source of fresh water. The status and perspectives of development of coupling renewable energy systems with desalination units are reviewed. It is pointed out that there are place of development even for such technologies that seem to be the most mature ones.     

Energy conservation in the greenhouse system: A steady state analysis

We have evaluated the five typical shape of the greenhouse for energy conservation in winter months for a composite climate. An expression for the plant temperature has been used for steady state analysis. Numerical computation has been carried out for the climatic condition of Delhi, India. The evaluation of the shape of the greenhouse has been done for a given floor area. Additional energy required from other fuels to maintain the necessary temperature has also been considered. It has been observed that a standard peak uneven span is suitable for minimum use of liquefied petroleum gas for a given favourable plant temperature. Experimental validation of the thermal model has also been carried out.     

Effect of spectral quality on horticultural plant propagation in a greenhouse

A greenhouse of semi-circular shape was employed to study the effect of spectral light response on the stem-cutting propagation of horticultural plants. The number of days taken for the root formation were noted and it was observed that the stem cuttings showed earlier root formation under a red-tinged greenhouse followed by a blue-tinged greenhouse. The UV-stabilised sheet prolonged the formation of well-formed roots by an additional three days over that for the control system. The study shows that the temperature gradient is not only a minimum at canopy level but also negative throughout in blue cladded greenhouse and a maximum vertical heat flux of zero is noticed.     

Computation of surface radiation and natural convection in a heated horticultural greenhouse

This study analyses the effects of the radiation exchange inside a horticultural greenhouse, under winter climatic conditions, according to the number of squared heating tubes used. These ones, hot and isothermal, are equidistant inside the greenhouse volume. The governing differential equations are discretized using a finite volume method and the coupling pressure–velocity problem is carried out by the SIMPLER algorithm. The algebraic systems obtained are solved by a conjugate gradient method. Results are reported in terms of isotherms, streamlines and average Nusselt number for Rayleigh number of 10³–10⁶. The contour lines show that the radiative effects are noted near the solid surfaces, and become increasingly important when the Rayleigh number increases. As a result, the rise in the value of Rayleigh number leads to an increase of the overall heat transfer within the greenhouse.     

On the study of an energy-efficient greenhouse for heating, cooling and dehumidification applications

An analytical model, based on basic heat-transfer processes within a greenhouse, was used to study the performance of heat pump to meet the heating and dehumidification requirements in a greenhouse. Performance parameters of the heat pump, namely the Coefficient of Performance (COP) and the Specific Energy Consumption (SEC) of the heat pump were determined, along with the condenser and evaporator capacity ratings required to provide the necessary thermal conditioning to a model-sized greenhouse. Based on a typical weather pattern in Bangkok, the performance of the heat pump to maintain the greenhouse air at a day temperature of 27 °C and night temperature of 18 °C with a relative humidity of 40% spans 1.2–4.0 and 1000–16,000 kJ/kg for COP and SEC, respectively.     

Offshore wind in Europe : The current state of the art

After several decades of theoretical developments, desk studies, experimental wind turbines and prototype windfarms, the first large-scale commercial developments of offshore windfarms are now being built. To support and accelerate this development, the European Commission funded a project, ‘Concerted Action on Offshore Wind Energy in Europe’ (CA-OWEE), which aimed to gather and distribute knowledge on all aspects of offshore wind energy, including: offshore technology, electrical integration, economics, environmental impacts and political aspects. The partners are from a wide range of fields and include developers, utilities, consultants, research institutes and universities. Andrew R. Henderson, Section Wind Energy, Delft University of Technology, The Netherlands and other authors give an overview of the findings of the project.     

Assessing heating and cooling demands of closed greenhouse systems in a cold climate

Reducing greenhouse gas emissions by providing non‐fossil fuel energy sources is imminently necessary. The area of particular interest in this paper is the agricultural greenhouse industry. In these structures, significant heating demands are present, especially in cold climates, and are typically met by combusting fossil fuels. In an effort towards a sustainable energy supply, the potential of closed greenhouse systems in a cold climate is explored. In these systems, natural ventilation for cooling and dehumidification is replaced with active systems, and the thermal energy removed can be re‐used, reducing the overall heating demand. A transient greenhouse model is created using TRNSYS software and validated with natural gas usage data from a reference greenhouse. The annual heating and cooling demands, effect of varying cover materials and potential for heat recovery ventilation are explored for the most concentrated greenhouse areas in Canada. Copyright © 2017 John Wiley & Sons, Ltd.     

Energy and the state of nations

The mathematical conditions for the existence of macroeconomic production functions that are state functions of the economic system are pointed out. The output elasticities and the elasticities of substitution of energy-dependent Cobb-Douglas, CES and LinEx production functions are calculated. The output elasticities, which measure the productive powers of production factors and whose numerical values have been obtained for Germany, Japan, and the USA, are for energy much larger and for labor much smaller than the cost shares of these factors. Energy and its conversion into physical work accounts for most of the growth that mainstream economics attributes to “technological progress” and related concepts. It decisively determines the economic state of nations. Consequences for automation and globalization and perspectives on growth are discussed.     

Energy resources' utilization in organic and conventional vineyards: Energy flow, greenhouse gas emissions and biofuel production

An energy analysis, in conventional and organic vineyards, combined with ethanol production and greenhouse gas emissions, is useful in evaluating present situation and deciding best management strategies. The objective of this study was to evaluate the differences in the energy flow between organic and conventional vineyards in three locations, to calculate CO₂, CH₄ and N₂O-emissions based on the used fossil energy and to explore if wine industry wastes can be used to extract bioethanol. The data were collected through personal interviews with farmers during 2004–2005. Eighteen farmers, who owned vineyards about 1 ha each, were randomly selected to participate in this study [(3 conventional and 3 organic) × 3 locations]. The means averaged over all locations for fertilizer application, plant protection products application, transportation, harvesting, labor, machinery, fuels, plant protections products and tools energy inputs, total energy inputs, outputs (grapes), outputs (grapes + shoots), grape yield, man hour, pomace and ethanol from pomace were significantly higher in conventional than in organic vineyards, while the opposite occurred for the pruning. Means averaged over two farming systems for harvesting, tools energy inputs, energy outputs (grapes), grape yield, pomace and ethanol from pomace were significantly higher at location A, followed by location C and location B. Finally, for irrigation, the means averaged over the two farming systems were significantly lower at location C. Greenhouse gas emissions were significant lower in organic than in conventional vineyards. The results show a clear response of energy inputs to energy outputs that resulted from the farming system and location.     

Energy management as the management of innovation

It is often said that investments in energy conservation are in some way low risk. This paper shows that like all investments they must, by definition, have elements of risk. It is part of the Energy Manager's role to manage these investments, which because of their novelty, are innovations. Consequently Energy Managers should consider themselves to be innovators and draw lessons from theories of the management of innovation. This paper indicates what can be learnt from these theories and suggests a basic, systematic model for energy conservation innovation.     

The intelligent envelope: The current state of the art

Solar components integrated in the building envelope can provide an important contribution to the utilisation of renewable energy sources for the climatization of the building indoor space, when these components are designed for optimal efficiency and when they are equipped with an appropriate control of their operating parameters.The aim of the R & D in this field is to modify the characteristics of windows and curtain walls in order to improve the thermal and lightning performances and to develop facade-integrated components, performing active functions of indoor climatization and remote space daylighting. The utilisation of this components, operating under automatic control, reduce the energy consumption in winter, increase the reduction of overheating in summer and operate mechanical ventilation for indoor spaces. The main design objective of researchers and producers is to produce reliable, low cost, high efficient industrialised solar components which can be integrated in a wide range of building typologies. The introduction of automation into the operation of movable elements of the passive solar systems could solve several problems.     

Silicon ribbons and foils—state of the art

Research and development on crystal growth technologies for production of crystalline silicon ribbon have been under way now for three decades. I review here their progress toward establishment of manufacturing capabilities for silicon wafers for photovoltaic applications. I examine technology improvements which are currently being explored for a future generation of low cost solar products based on ribbon wafers, and discuss potential limits of the technology.     

PCM thermal storage in buildings: A state of art

A comprehensive review of various possible methods for heating and cooling in buildings are discussed in this paper. The thermal performance of various types of systems like PCM trombe wall, PCM wallboards, PCM shutters, PCM building blocks, air-based heating systems, floor heating, ceiling boards, etc., is presented in this paper. All systems have good potential for heating and cooling in building through phase change materials and also very beneficial to reduce the energy demand of the buildings.     

我国空气源热泵的技术进展

介绍了近年来我国空气源热泵方面的研究现状，并就结霜、化霜、系统节能、新工质替代、计算机模拟等方面进行了综述，分析了空气源热泵仍存在的一些问题并提出了相应的改进方向。     

Energy management strategy of Supercapacitor/Fuel Cell energy storage devices for vehicle applications

This paper addresses the management of a Fuel Cell (FC) – Supercapacitor (SC) hybrid power source for Electric Vehicle (EV) applications. The FC presents the main energy source and it is sustained with SCs energy storages in order to increase the FC source lifespan by mitigating harmful current transients. For this aim, the reported work proposes a Grey Wolf Optimizer (GWO) for an efficient power management of the studied hybrid power system. The key idea of the proposed approach is to incorporate the benefit of the GWO in terms of fast optimization and convergence accuracy, in order to achieve efficient energy sources exploitation and provide the desired driving performances. Simulations and experimental results verify the validity of the proposed management algorithm.     

Opportunities,challenges, and state of the art of flexible heat-pipe heat exchangers: A comprehensive review

Heat pipes (HPs) play a pivotal role in efficiently managing the thermal challenges posed by high heat flux devices. To facilitate their operation at extremely low temperatures, specialized working fluids with low-boiling points are a necessity. HPs serve as efficient heat exchanger (HEX) in diverse applications, such as heat pumps and heat-transfer components. In the realm of space applications, HP is indispensable for cooling electronic components within two-phase thermal control systems. Notably, the recent significant reduction in HP production costs has paved the way for synergizing HP with HEX, promising substantial energy savings. This comprehensive review centers its focus on the advancements in HEX-based flexible HP systems. It critically evaluates various performance models and investigates key findings from a multitude of literature papers that pertain to HEX applications. The review encompasses a wide spectrum of innovations, including conventional, pulsating, and thermosyphons (gravity-assisted) in HEX. It further explores studies on recuperative and regenerative HEX configurations. The surveyed literature underscores the critical role played by the choice of operating fluid and heat load in significantly influencing HP performance. This study offers a comprehensive understanding of key outcomes, strengths, limitations, and specific applications of HP and HEX. The review also highlights the significance of operating fluid selection and considerations related to heat load while outlining exciting opportunities for future research in this domain. Moreover, it introduces several novel concepts for future studies in pertinent domains, offering promising directions for further exploration within this field.     

Solar-thermal driven drying technologies for large-scale industrial applications: State of the art,gaps, and opportunities

Research and Innovation (R&I) on Large-scale Industrial Solar-thermal driven Drying technologies (LISDs) is one of the strategies required to transition to a low-carbon energy future. The objective for this work is to guide future R&I on LISDs by defining the state of the art, gaps, and opportunities. To provide a high-level perspective on the current state of solar drying research, results are presented from an analysis of the content relevant to LISDs found in 45 solar drying Review Articles published in journals over the past 25 years. A conclusion is that most of the existing solar drying research is not focused on LISDs. To build-on these existing 45 solar drying Review Articles, results are presented from an analysis of 30 Original Research Articles with significant content relevant to LISDs published over the past 5 years. A gap is identified in coupling existing or slightly modified solar thermal collectors with existing or slightly modified industrial drying technologies to create indirect LISDs. To facilitate formulating new coupling strategies, the drying characteristics most relevant to this coupling are described and four fundamental classes of industrial dryer technologies are defined based on the underlying heat transfer mechanism, which then impacts the appropriate collector choice. At their most fundamental level, many of the technologies needed to couple solar collectors and industrial dryers to create novel indirect LISDs are not unique to indirect LISDs, but rather can be generalized across a wide range of Solar Heat for Industrial Processes (SHIP) applications, and integration issues are discussed at a more fundamental SHIP level. The technical and economic characteristics of 19 existing LISDs installations throughout the world are presented, and potential and emerging areas discussed.     

Advanced tubular solar energy collector— A state of the art

In this article, the state of the art of the evacuated tubular solar energy collector has been discussed. Evacuated collectors are one of the most promising alternatives for industrial process heating, air-conditioning and refrigeration, pumping of water, production of electric energy, etc., because of its high efficiency at sufficiently high temperatures and no tracking requirements. Here, the various designs, and special features which have distinguished it from conventional flat plate collectors have been high-lighted. An attempt has also been made to analyse the optical and thermal behaviour of this evacuated collector.     

Energy policies and the greenhouse effect: A study of national differences

Country studies emphasize large national differences in underlying attitudes towards energy and the greenhouse effect. Technical opportunities for limiting CO₂ emissions exist in all countries, but the type of abatement policies that are feasible, the extent to which they can be effectively implemented and their likely impacts vary widely. The potential for curtailing emissions is determined by factors including: the stage of a country's development; the character of its economic system and philosophy; its political culture; and the nature of its energy infrastructure, institutions and attitudes, all of which are determined by the past and current availability of cheap domestic technology and costs, but about culture, about technology and costs, but about culture, institutions and politics in the broadest sense.