Showing papers in "International journal of ambient energy in 2011"

Performance and emission characteristics of a diesel engine fuelled by neem oil blended with alcohols

Abstract: Fuel crisis and environmental concerns have led researchers to look for alternative fuels of bio-origin sources such as vegetable oils, which can be produced from forests and oil-bearing biomass materials. Vegetable oils have energy content comparable to that of diesel fuel. Straight vegetable oils posed several operational problems and durability problems when subjected to long-term usage in compression ignition engine. These problems are attributed to higher viscosity and lower volatility. In this study, performance and emission parameters of a diesel engine operating on neem oil and its blends of 5, 10, 15 and 20 vol% with ethanol, 1-propanol, 1-butanol and 1-pentanol are evaluated and compared with diesel operation. The results indicate that the brake thermal efficiency is improved with the use of neem oil–alcohol blends with respect to those of neat neem oil. The smoke intensity, CO and HC emissions with neem oil–alcohol blends are observed to be lower with respect to those of neat neem oil at higher...

Ecological performance of an endoreversible Carnot refrigerator with complex heat transfer law

Abstract: The optimal ecological objective of an endoreversible Carnot refrigerator based on a new generalised heat transfer law , including generalised convective heat transfer law and generalised radiative heat transfer law, is derived. The ecological objective function representing the best compromise between the exergy output rate and exergy loss rate (entropy production rate) of the refrigerator. The results include the optimal ecological performance of the endoreversible Carnot refrigerator with various heat transfer laws, which obtained in many literatures.

Thermal performance improvement of solar air flat plate collector: a theoretical analysis and an experimental study in Biskra, Algeria

Abstract: This article presents the results of the first experimental investigation of the performance of solar air flat plate collector at Biskra (latitude 34°48′N and longitude 5°44′E), Algeria. The thermal efficiency between absorber plate and air in flat plate solar collector has been enhanced by introducing obstacle rows in the dynamic air vein of the collector. For this objective, a flat plate solar collector, of 1.73 m2 area and 25 mm air gap, has been designed and constructed. These obstacles formed with two parts: first part is perpendicular to fluid flow and the second part is inclined, they are mounted in a staggered pattern, oriented perpendicular to the fluid flow and soldered to the back plate. The solar air heater was mounted on a stand facing south at inclination angle, and it was tested under the environmental conditions. Moreover, a theoretical approach is employed for determination of the thermal performances of this collector where the temperatures of all components of the collector and outlet a...

Studies on biodiesel production and its effect on DI diesel engine performance, emission and combustion characteristics

Abstract: Production of biodiesel from waste cooking oil was studied by experimental investigation using response surface methodology, specifically D-optimal design consisting of two levels. Waste cooking oil methyl ester (WCO-ME) produced under optimum transesterification process parameters was used in a direct injection diesel engine to evaluate the performance, emission and combustion characteristics at a constant speed of 1500 rpm. Results revealed that the biodiesel resulted in decreased brake thermal efficiency by 6% and higher brake-specific energy consumption of 25.9% when compared to diesel at 100% load condition. Carbon monoxide (CO), unburnt hydrocarbon, nitric oxide (NO) emission and smoke emission of WCO-ME decreased by 43.3%, 52.7%, 23% and 15.5%, respectively, compared to diesel. WCO-ME exhibited lower heat release rate, shorter ignition delay of 10.9°CA and slightly longer combustion duration of 54.4°CA when compared to diesel at same load condition.

Finite-time thermodynamic modelling and analysis for an irreversible Miller cycle

Abstract: The performance of an air-standard Miller cycle is analysed using finite-time thermodynamics. An irreversible Miller cycle model which is more close to practice is founded. In the model, the non-linear relation between the specific heats of working fluid and its temperature, the friction loss computed according to the mean velocity of the piston, the internal irreversibility described using the compression and expansion efficiencies, and heat transfer loss are considered. The relations between the power output and the compression ratio, between the thermal efficiency and the compression ratio, and the optimal relation between power output and the efficiency of the Miller cycle are derived by detailed numerical examples. Moreover, the effects of internal irreversibility, heat transfer loss, friction loss and pressure ratio on the cycle performance are analysed. The power output versus compression ratio and the efficiency versus compression ratio curves of Atkinson and Otto cycles will be maximum and minimu...

A proposed framework for dynamic modelling of photovoltaic systems for DG applications

Abstract: Dynamic modelling and simulation is essential to predict the overall electrical performance of photovoltaic (PV) systems PV simulation models in the literature are not suitable for dynamic analysis with decentralised generation (DG) applications This article proposes a framework for PV system dynamic modelling and simulation process This framework presents the steps required to model the process of solar power generation, reflecting the environmental variables affecting the generation process Based on the framework steps, a computer simulation model is developed in MATLAB-Simulink of the PV generator, and validated by comparing the developed PV electrical performance characteristic curves with those of the manufacturer's data sheet and the ones developed by commercial software The last step of the proposed framework is dedicated for testing the developed PV model for grid-connected operation The proposed framework resulted in a simulation photovoltaic decentralised generation model which constitutes

Performance and emission analysis of blends of karanja methyl ester with diesel in a compression ignition engine

Abstract: On the face of the upcoming energy crisis, vegetable oils have come up as a promising source of fuel. They are being studied widely because of their abundant availability, renewable nature and better performance when used in engines. An experimental investigation was made to evaluate the performance and emission characteristics of a diesel engine using different blends of methyl ester of karanja with diesel. Karanja methyl ester was blended with diesel in proportions of 5%, 10%, 15%, 20%, 30%, 40%, 50% and 100% by mass. The performance parameters were found to be very close to that of diesel. The brake thermal and mechanical efficiencies were better than diesel for some specific blending ratios under certain loads. The emission characteristics were also found to be better than diesel with levels of carbon dioxide, carbon monoxide, nitric oxide and hydrocarbons lower than pure diesel.

The ecology of building materials, 2nd edition, by Bjørn Berge, translated by Chris Butters and Filip Henley

Abstract: The ecology of building materials, 2nd edition, by Bjorn Berge, translated by Chris Butters and Filip Henley, Oxford, UK, Burlington, MA, USA, Elsevier – Architectural Press, 2009, 446pp., £41.99 €...

Exergetic performance optimisation of an endoreversible intercooled regenerated Brayton cogeneration plant. Part 1: thermodynamic model and parametric analysis

Abstract: An endoreversible intercooled regenerative Brayton cogeneration plant model coupled to constant-temperature heat reservoirs is established in Part 1 of this article. On the basis of the exergetic analysis, the performance of the plant is investigated using finite-time thermodynamics. Analytical formulae about dimensionless exergy output rate and exergy efficiency are deduced. The two cases with fixed and variable total pressure ratios are discussed, and the intercooling pressure ratio and the total pressure ratio are optimised. The effects of the effectiveness of intercooler and regenerator, and the ratio of the hot-side heat reservoir temperature to environment temperature on the general and optimal performances of the cycle are analysed by detailed numerical examples. The relations between dimensionless exergy output rate and exergy efficiency are discussed and the characteristics are loop-shaped. At last, it is found that there exist two different optimal consumer-side temperatures, respectively, which...

Behaviour of ORC low-temperature power generation with different refrigerants

Abstract: This article presents and discusses the behaviour of low-temperature Organic Rankine Cycle for power generation using waste heat. The performance has been compared at low- and medium waste heat temperatures to organic and non-organic fluids. In this article, energy and exergy analysis have also been presented and compared for the behaviour of the different refrigerants. Results showed that the use of refrigerant mixtures maximises the waste heat recovery and produces power from low- and medium waste heat with less exergy destruction compared to other working fluids.

Environmental evaluation of base-loaded CHP systems for different climate conditions in the US

Abstract: This article examines a methodology to illustrate the emissions reduction potential by a base-loaded combined heating and power (CHP) system in a given building across different US regions. In addition, the size of the prime mover that may potentially reduce the carbon dioxide emissions is determined. The potential carbon dioxide emission savings from a CHP system considers the ratio of emissions conversion factors applied to imported electricity to emissions conversion factors applied to fuel consumed Results indicate that to be able to achieve savings in carbon dioxide emissions, must be larger than a unique constant that only depends on the CHP components efficiencies. A hospital benchmark building developed by the Department of Energy in different climate conditions was used as an example to apply the methodology presented in this article. The effects of the CHP power generation unit (PGU) size and the CHP system efficiency on carbon dioxide emissions are also considered, and a range of possible value...

Desiccant honey dehydrator

Abstract: A desiccant honey dehydrator has been designed, developed and tested. It heats and dehumidifies air to dehydrate honey. Re-circulation has been employed to prolong use-period of the desiccant bed. The dehydration was done with dehumidified or ambient air at 35°C and 45°C. The honey was also dehydrated in open for reference purposes. The maximum moisture evaporation rates in the case of a desiccant honey dehydrator using dehumidified air, ambient air and open dehydrating at 45°C were 132, 78.7 and 52 g/h m2, respectively.

Study of the performance and emission characteristics of a diesel engine using cotton seed oil-based fuels

Abstract: In this research work, different parameters for the optimisation of biodiesel production were investigated and then experiments were conducted to study the performance and emission characteristics of a four-stroke, single-cylinder, direct-injection, naturally aspirated diesel engine using cotton seed oil (CSO)-based fuels. The blends were prepared with 20% CSO and 40% cotton seed oil methyl esters (CSOME) separately with neat diesel on volume basis as diesel fuels. A maximum of 77.5% biodiesel were achieved with 20% methanol in the presence of 0.5% sodium hydroxide. The experimental results showed that the reduction in smoke, hydrocarbon (HC) and carbon monoxide (CO) emissions were observed for CSOME and its diesel blends along with increased NO x . However, a reduction in NO x , increase in smoke, HC and CO emissions were observed for CSO 100 and its diesel blends compared to those of neat diesel.

Stand-alone solar electric systems, by Mark Hankins

Abstract: Stand-alone solar electric systems, by Mark Hankins, London, Washington, DC, Earthscan, 2010, 248 pp., £34.99 US$59.95 (Hard back), ISBN(13) 978-1-84407-713-7 This valuable book dives straight into...

Sustainable energy development by small hydropower with CDM benefits in India

Abstract: Small hydropower (SHP) is an environmental friendly technology and qualifies for Clean Development Mechanism (CDM) benefits. The CDM is a part of the global market, developing rapidly in response to global warming. It has two objectives to achieve, i.e. sustainable development in host countries and assist other countries in achieving the emission reduction targets. In this study, an attempt has been made to estimate the CDM potential from SHP projects in India. It has been found that there is a vast potential of CO2 abatement by developing SHP projects. The annual Certified Emissions Reductions (CERs) from SHP projects under implementation in India could reach up to 1.26 million tonnes. CDM benefits will help to develop remaining potential of SHP projects more effectively in sustainable manner. An analysis has also been carried out using logistic model to predict SHP development. It has been found that the remaining potential of SHP in India can be developed by the year 2040.

Energy analysis of single-stage LiBr–water vapour absorption refrigeration system using artificial neural network approach

Abstract: In this study, artificial neural network (ANN) has been used as a new approach for carrying out the energy analysis of a single-stage absorption refrigeration cycle with water–lithium bromide as the working fluid pair. Energy analysis of an absorption system is a very complicated process mainly because of the limited experimental data and analytical functions required for calculating the thermodynamic properties of fluid pairs, which usually involves the solution of complex differential equations. Instead of complex differential equation and limited experimental data, faster and simpler solutions were obtained by using equations derived from the ANN model. As seen from the results obtained, the calculated thermodynamic properties are within acceptable results. Thermodynamic properties of each point in the cycle are calculated using related equations of the state. Heat flow rate of each component in the cycle and some performance parameters are calculated from the first law analysis. The results show that ...

Heating load and COP optimisations for a universal steady flow endoreversible heat pump model

Abstract: The heating load and coefficient of performance (COP) of a class of universal steady flow endoreversible heat pump cycle model, which consists of one heating branch, two cooling branches and two adiabatic branches, are optimised using the theory of finite time thermodynamics. The analytical formulae for heating load and COP versus temperature ratio as well as COP versus heating load of the cycle model are derived. Effects of the total heat exchanger inventory on performances of heat pump cycles are shown by detailed numerical examples. The results obtained herein include the optimal performances of endoreversible Otto, Brayton, Atkinson, Diesel, Dual and Carnot heat pump cycles.

Optimal performance for a steady-flow endoreversible refrigerator model including five typical cycles

Abstract: The optimal performance of a universal endoreversible steady-flow refrigerator cycle consisting of a constant thermal-capacity heating branch, a constant thermal-capacity cooling branch and two adiabatic branches with heat transfer loss was analysed using finite-time thermodynamics. The analytical formulae about cooling load, coefficient of performance, exergy loss rate, exergy output rate and ecological criterion of the endoreversible steady-flow refrigerator cycle are derived. Moreover, analysis and optimisation of the model were carried out in order to investigate the effect of the cycle process on the performance of the cycles using numerical examples. The results obtained include the performance characteristics of endoreversible steady-flow Carnot, Diesel, Otto, Atkinson and Brayton refrigeration cycles. The results can provide some theoretical guidance for the design of practical refrigerators.

Exergoeconomic performance of an endoreversible Carnot refrigerator with complex heat transfer law

Abstract: The finite-time exergoeconomic performance of an endoreversible Carnot refrigeration with a complex heat transfer law, including generalised convective and radiative heat transfer laws, , is investigated in this article. The focus of this article is to obtain the compromised optimisation between economics (profit) and the energy utilisation factor (coefficient of performance, COP) for the endoreversible Carnot refrigerator, by searching the optimum COP at maximum profit, which is termed as the finite-time exergoeconomic performance bound. The obtained results include those obtained in many literatures and can provide some theoretical guidance for the design of practical refrigerators.

Prosperity without growth: economics for a finite planet, by Tim Jackson

Abstract: Prosperity without growth: economics for a finite planet, by Tim Jackson, London, UK, Washington, DC, USA, Earthscan, 2011, 293 pp., £9.99 US$16.95 (soft back), ISBN(13) 978-1-84971-323-8/288 pp., ...

Finite-time exergoeconomic performance analysis and optimisation for generalised irreversible combined heat pump cycles

Abstract: Finite-time exergoeconomic performance of a Newtonian heat transfer law system generalised irreversible combined heat pump cycle model with irreversibility of finite-rate heat transfer, heat leakage and internal irreversibility is studied in this article. The operation of the generalised irreversible combined heat pump cycle is viewed as a production process with exergy as its output. The performance optimisation of the cycle is performed by taking profit as the objective. The optimal profit rate, optimal coefficient of performance (COP), as well as the relation between the optimal profit rate and COP of the cycle are derived. The focus of this article is to obtain the compromise optimisation between economics (profit rate) and the energy utilisation factor (COP) for the cycle, by searching the optimum COP at maximum profit rate, which is termed as the finite-time exergoeconomic performance bound. Moreover, the effects of various factors, including heat leakage, internal irreversibility and the price rati...

Energy-efficient municipal heating: preliminary lessons from Beijing, Kathmandu and Edinburgh

Abstract: This study explores energy-efficiency efforts related to municipal heating in the metropolitan areas of Beijing, China; Kathmandu, Nepal; and Edinburgh, Scotland. This article begins by describing its research methodology consisting primarily of research interviews and in-country surveys. It then discusses respondents’ answers and preliminary findings to questions on energy-efficiency awareness, temperature preferences, heating arrangements in buildings and problems related to existing policies and procedures. The final section presents a number of recommendations for what city planners and national policymakers can do to promote energy-efficient heating. This study is unique from previous works as its focus is hospitals, administration buildings, schools and universities rather than (more commonly studied) households, countries and energy systems. Municipal heating was also chosen because it is much less popular as an area of scholastic enquiry than other areas of energy efficiency such as cars, homes or appliances, and the study is sensitive to the importance of social attitudes and values as they relate to energy consumption and heating norms.

Engaging the public with climate change: behaviour change and communication, edited by Lorraine Whitmarsh, Saffron O’Neill and Irene Lorenzoni

Abstract: Engaging the public with climate change: behaviour change and communication, edited by Lorraine Whitmarsh, Saffron O’Neill and Irene Lorenzoni, London, Washington, DC, Earthscan, 2011, 315pp., £49....

A prototype of a solar-tracking power-generating system

Abstract: This article describes a practical, low-cost closed-loop sun-tracking solar-panel power generator prototype which rotates on a single axis along the east–west direction of the sun's path. It uses photosensors to detect the incident angle of the sun's ray to the surface of the solar panel. The photosensor module consists of three phototransistors, which automatically adapts its sensitivity to the sun's brightness to enhance its function under all weather conditions. The system is controlled by a field programmable gate array (FPGA). The FPGA controls the movement of the motor in short 50 ms pulses every 3 s during tracking mode followed by 3 min of sleep mode. This method produces small angular step movement of the solar panel with little expense of battery power. At night, a photoresistor detector will enable the controller to switch off most parts of the system to further reduce power consumption.

Heat pumps – challenges for new build and retrofit in domestic applications

Abstract: Heat pumps are a proven high-efficiency heating systems with numerous European examples of best practice in both new build and retrofit. However in the UK, in particular, there is a growing body of evidence that suggests a lack of understanding in determining the advantages for a particular house (whether new build or retrofit), thus the system does not meet expectations, and poor installation and operation again lead to the unit not meeting the expectations. Heat pumps are tested according to EN14511 which is the European test standard. The data stated can be true at one particular point, e.g. for a brine to water heat pump, the coefficient of performance (the ratio of heat supplied to electricity used) is at brine of 0 C and water supplied at 35 C. Careful attention to performance is required to systems that operate outside these parameters. Heat pumps for domestic applications come in a number of types, namely ground source (brine to water), air source (air to water) and more rarely air-toair and therefore will be discounted. The ground source heat pump extracts heat from either, for example, the garden with horizontal coils of pipe at about 1.2m deep or vertically in a series of boreholes. In each case, plastic pipe is utilised and its advantages include the fact that the ground temperature is warmer that the winter air and thus the system operates efficienctly, especially when used with lower temperature underfloor heating systems. Thus, these systems are ideally installed in a new build or major refurbishment scenario where the significant disturbance can be accommodated as part of the build process. However, the challenges arise from underestimation of the ground area for horizontal systems, for example. The ground area for horizontal systems is important as it stores solar energy typically in the summer and allows the heat pump to draw upon this in winter. Area is important along with the pipe length and spacing calculations. However there is often an overestimation of the winter soil temperature. Average soil temperature is often used and can be stated as high as 12 C from limited publications based in the south of England. However winter soil temperature at 1.2m in the North can be 6 C colder, and thus sizing a ground source heat pump must always recognise this. The temperature at which the underfloor heating system is designed also takes its part with very few being at 35 C. Air-source and ground-source heat pumps are often quoted as requiring a secondary heating source. Given their low temperature of operation, the boost heaters designed to overcome legionella fears can act in this role in that the additional electric heating to bring domestic hot water to a temperature greater than 60 C once a week can act as additional heating in exceptionally cold weather or at times of heat pump failure. Such boost heaters are usually accommodated in a buffer tank which allows the heat pump to run for a sufficient period of time even in milder weather. Airsource units are deemed acceptable for retrofit applications where higher temperature cascade heat pumps, for example, coupled with more efficient household heating radiators can provide efficient heating with minimal retrofit disturbance. Sizing of heat pumps presents the greatest challenge. Sizing for a design point of, for example, 3 C would mean that for longer periods the heat pump would be oversized. This would lead to shortcycling operating periods and therefore reduce lifespan coupled with higher capital cost for a larger unit. Yet, the homeowners want a heating system that meets their demands. The buffer vessel is one solution and variable speed heat pumps are another (one whose compressor speed is reduced to meet demands), but the application of what were deemed European best practices must be in their entirety and not piecemeal to suite installation conditions and costs. Thus, please consider the installation most carefully!

Accounting for sustainability: practical insights, edited by Anthony Hopwood Jeffrey Unerman and Jessica Fries

Abstract: Accounting for sustainability: practical insights, edited by Anthony Hopwood Jeffrey Unerman and Jessica Fries, London, Washington, DC, Earthscan, 2010, 616pp., £85.00 US$ 140.00 (Hard back), ISBN(...

Renewable energy and the public: from NIMBY to participation, edited by Patrick Devine-Wright

Abstract: Renewable energy and the public: from NIMBY to participation, edited by Patrick Devine-Wright, London, Washington, DC, Earthscan, 2011, 356pp., £60.00 US$99.95 (Hard back), ISBN (13) 978-1-84407-86...

Climate change: the science, impacts and solutions, 2nd edition, by A. Barrie Pittock

Abstract: Climate change: the science, impacts and solutions, 2nd edition, by A. Barrie Pittock, Collingwood, VIC, Australia, CSIRO Publishing, 2009, (Soft Cover), ISBN (13) 978-0-64309-484-0 and London, Ste...