The focus of the present contribution is hydraulic energy recovery by means of hydropneumatic multi-chamber accumulators. A simulation study is presented comparing two different multi-chamber accumulator concepts for energy recovery in an exemplary load case involving a forklift mast. The first concept is based on the “Double Piston Accumulator” /1/. It is compared to the so-called “Digital Accumulator” /2/. Both similarities and differences of the two concepts are discussed in the presentation.

Controlling the thermo-elastic behavior of tooling machines can only be achieved by systematic analysis, characterization and design of their fluidic system. In the first stage of this project, fundamental work was done to develop simulation methods for the calculation of the thermodynamic behavior of a representative example of a milling machine and each of its components. With experimental and numerical data it was proven, that significant improvement can be achieved by a proper design of heat transfer conditions of the fluidic system. To correct and counterbalance thermo-energetic effects, it will be necessary to develop new structures of the tooling machines systems which ensure the temperature-control of local subsystems in dependence of the actual working process. The work which is documented in this paper deals with the thermodynamic behavior of the motor spindle.

Speed and displacement variable pumps offer a degree of freedom for process control. As a certain operation point can be supplied by different combinations of drive speed and pump displacement intelligent control strategies can address major issues like energy efficiency, process dynamics and noise level in industrial applications. This paper will provide an overview of recent research and development activities to evaluate the named potentials.

The paper shows standard circuits with load reactive and non load reactive counterbalance valves. A Matlab simulation based on a linear model for the circuit with load reactive counterbalance valves shows what parameters have a significant influence on the stability of the system. The most important parameters of the counterbalance valve that influence the stability are pilot gain and relief gain. The factors describe how pilot pressure and load pressure affect the flow across the counterbalance valve. A new counterbalance valve (patent pending) has the pilot gain and relief gain required for stability only in operating ranges that require the parameters for stability. When the load is not moving or the counterbalance valve is not required for positive (non overrunning) loads, the new valve has a higher pilot ratio, which means that the valve opens further at lower inlet pressures. The new counterbalance valves saves about 30% power compared with a standard counterbalance valve that has the same parameters for stability when it is lowering an overrunning load. The standard counterbalance can be replaced with the new load adaptive valve in the same cavity. The paper shows test results and the design of the valve.

This paper is presenting the application of Power Regenerative Boom(PRB) system to excavator. In order to increase the fuel efficiency of the excavator, potential energy of the front structure is recuperated by the hydraulic hybrid system with electric-hydraulic control, during boom down motion. Charged energy into accumulator is reused after boom down motion, the pressurized oil goes to hydraulic motor. The hydraulic motor is mounted on the engine PTO(Power Take-Off), therefore output torque of the hydraulic motor assists the diesel engine directy, it leads to decrease fuel consumption of diesel engine. After the system design and simulation investigation, the presented system was installed into Doosan’s 38ton excavator, DX380LC-3 model, and the energy saving result was verified by a digging and dumping repetition test. The test result shows that fuel consumption was dramatically decreased by 5.0 L/hr compared to the standard DX380LC-3.

The stagnant performance of single core processors, increasing size of data sets, and variety of structure in information has made the domain of parallel and high-performance computing especially crucial. Graphics Processing Units (GPUs) have recently become an exciting alternative to traditional CPU architectures for applications in this domain. Although GPUs are designed for rendering graphics, research has found that the GPU architecture is well-suited to algorithms that search and analyze unstructured, graph-based data, offering up to an order of magnitude greater memory bandwidth over their CPU counterparts. This thesis focuses on GPU graph analysis from the perspective that algorithms should be efficient on as many classes of graphs as possible, rather than being specialized to a specific class, such as social networks or road networks. Using betweenness centrality, a popular analytic used to find prominent entities of a network, as a motivating example, we show how parallelism, distributed computing, hybrid and on-line algorithms, and dynamic algorithms can all contribute to substantial improvements in the performance and energy-efficiency of these computations. We further generalize this approach and provide an abstraction that can be applied to a whole class of graph algorithms that require many simultaneous breadth-first searches. Finally, to show that our findings can be applied in real-world scenarios, we apply these techniques to the problem of verifying that a multiprocessor complies with its memory consistency model.

Thesis (MBA (Business Management))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: It has been established worldwide that energy efficiency undertakings are the fastest, most cost-effective and cleanest way to extend energy supplies. When the energy supply made available through energy efficiency projects are compared with increasing primary supply through building new conventional generation facilities, the former is in most cases also safer, more reliable and a more secure form of investment. Energy service companies (ESCOs) are the recognised implementation vehicles of energy efficiency projects and have been in use internationally for many years for this purpose. Globally, however, ESCOs do not have a good history of being viable business enterprises. The most important barriers identified internationally hindering ESCOs’ growth and sustainability were the potential customers’ lack of awareness, information and understanding regarding energy efficiency projects, the financing of these projects, as well as the support of government on energy efficiency policies and regulations. The urgency of implementing energy efficiency measures in South Africa is critical based on the precarious situation of the national electrical suppliers’ ability to provide electricity unfailingly to all its current and future customers. The South African electrical energy situation should therefore provide tremendous opportunities to the local ESCO industry. The aim of this study was therefore to reiterate the importance of energy efficiency projects and to describe the barriers to growth and sustainability experienced by ESCOs in South Africa against the international backdrop. This was done by way of a survey sent out to all registered ESCOs in South Africa. Based on the responses to the survey, the South African industry is in dire straits and is hindered by various barriers to their growth and sustainability. The study identified eight major barriers in the South African ESCO industry which are similar to those experienced by ESCOs internationally. The uniqueness of the local barriers however, is that the industry operates in a highly regulated environment and that these regulators, being the government and Eskom, are recognised as the main perpetrators responsible for most of these barriers, largely due to a lack of dedicated action. Furthermore, the study shows that it is critical for all role players in the South African energy efficiency industry, and specifically the South African government and Eskom, to recognise these barriers and to assist in solving them to improve the growth opportunities in the ESCO industry. Removal of these barriers will not only improve the electricity situation, but will also have a number of positive effects on the micro and macro-economic levels of South Africa, as well as the environment. Finally, the study makes suggestions about the way forward through a number of actions to be taken to lower or remove the most important of these barriers. / AFRIKAANSE OPSOMMING: Dit is reeds wêreldwyd bevestig dat energie-effektiwiteitsprojekte die vinnigste, kostedoeltreffendste en omgewingsvriendelikste manier is om energiebronne uit te brei. Wanneer die energieverskaffing wat beskikbaar gestel word deur energieeffektiwiteitsprojekte vergelyk word met die vermeerdering van primêre energie deur die bou van nuwe konvensionele opwekkingsfasiliteite, is eersgenoemde in die meeste gevalle ook veiliger en ’n meer betroubare en stabiele beleggingsvorm. Energie-diensmaatskappye (energy service companies (ESCOs)) is die erkende implementeringsmediums vir energie-effektiwiteitsprojekte en word reeds baie jare lank internasionaal vir hierdie doel aangewend. ESCOs het egter wêreldwyd nie ’n goeie rekord as lewensvatbare sake-ondernemings nie. Die vernaamste hindernisse wat ESCOs se groei en welvaart stuit is internasionaal geïdentifiseer as voornemende kliënte se gebrek aan bewustheid, inligting en begrip rakende energie-effektiwiteitsprojekte, die finansiering van sodanige projekte, asook die ondersteuning van die regering ten opsigte van energieeffektiewiteitsbeleide en -regulasies. Daar is groot dringendheid om energie-effektiewe projekte en maatreëls in Suid Afrika te implementeer, gebaseer op die huidige onsekerheid of die nasionale elektrisiteitsverskaffer wel in staat is om ’n betroubare bron van elektrisiteit aan sy huidige en voornemende kliënte te voorsien. Die Suid Afrikaanse elektriese energie situasie behoort daarom heelwat geleenthede te skep vir die plaaslike ESCO-industrie. Die doel van hierdie studie was dus om die belangrikheid van energie-effektiwiteitsprojekte te beklemtoon en om die hindernisse te omskryf wat ESCOs in Suid Afrika se groei en welvaart stuit, gesien vanuit ‘n internasionale perspektief. Dit was gedoen deur ‘n vraelys aan alle geregistreerde ESCOs te stuur. Na aanleiding van die terugvoering op die vraelyste, sukkel hierdie industrie om kop bo water te hou weens verskeie hindernisse wat hulle groei en welvaart stuit. Hierdie studie identifiseer agt belangrike hindernisse in die Suid-Afrikaanse ESCO industrie wat ooreenstem met die wat deur internasionale ESCOs ondervind word. Die uniekheid van die plaaslike hindernisse is egter dat die industrie werksaam is in ‘n streng gereguleerde omgewing en dat die reguleerders, die regering en Eskom, ook uitgewys word as die vernaamste skuldiges wat verantwoordelik is vir meeste van die hindernisse, hoofsaaklik as gevolg van hulle gebrek aan toegewyde uitvoering van take. Die bevindinge van hierdie studie toon verder dat dit krities is vir al die rolspelers in die Suid-Afrikaanse energie-effektiwiteitsindustrie, spesifiek die Suid-Afrikaanse regering en Eskom, om hierdie hindernisse te erken en om saam te werk om hulle te oorkom en sodoende die groeigeleenthede in die ESCO-bedryf te verbeter. Die verwydering van hierdie hindernisse sal nie alleen die elektrisiteitsituasie verbeter nie, maar sal ook ’n aantal positiewe invloede hê op die mikro- en makro-ekonomiese vlak van Suid-Afrika, sowel as die omgewing. Die studie sluit af met voorstelle rakende die uitvoering van verskeie aksies wat die verwydering van die vernaamste hindernisse tot gevolg sal hê, of die hindernisse se impak op die industrie sal verminder.

The global energy usage have been growing and is expected to grow in the forthcoming years. The negative effects of increased energy use are greatly depending on the type of base raw materials required for converting the energy and the negative consequences those have on the environment. From the energy used, fossil fuels stands for the largest part. Excess use of fossil fuels have been shown to have considerable negative effects on the environment, including, but not limited to global warming. Renewable energy is today the world’s fastest growing energy source limiting the negative consequences of growing energy use. The commercial and residential buildings stands together for about 40 % of the total energy usage. Residential buildings alone stands for 20 % of the total world delivered energy consumption by end-use sector. In EU the average residential energy use amounts to 25 % and for individual countries like Sweden and Finland it is 21 %. The EU energy efficiency directive from year 2012 sets a target to save 20 % of the unions primary energy usage by year 2020 compared to the year 1990. The EU countries also agreed in October 2014 on a new energy efficiency target of at least 27 % by the year 2030. To reach this goal, improved energy efficiency are required in all sectors. Finland’s energy efficiency law for buildings from 2013 greatly reduces the minimum energy usage allowed for new buildings. Finland is also preparing for a new law that would by 2020 require all new buildings to be zero or close to zero energy buildings. This is defined by the Ministry of the Environment as buildings that have very high energy efficiency, where the already greatly reduced energy demand is satisfied extensively by renewable energy. As part of the goal to greatly increase buildings energy efficiency, this work focus on heat exchangers for showers. The purpose of this project is to investigate how two different heat exchangers works for shower cabins. This is done by testing a system where the heat exchangers are linked together. The system works by transferring heat from the drainage water and the moist air to the incoming colder drinking water before the cold water is heated in the mixerto desired shower temperature. The measurements are taken for different simulated shower situations. The Heat exchangers efficiency are calculated and the energy savings are examined with annual energy savings. The payback time shows that the system is not currently viable. The efficiency need to be improved, the main issue being the constituent materials heat transfer attributes between cold and hot water. The results are discussed and it is concluded that the system would be viable with improved heat exchanger efficiency and adequate shower use, which depends on the user and the amount of people using the shower. The main issue with increased heat transfer efficiency is the greater risk of contamination between the incoming cold drinking water and the outgoing dirty drainage water.

Sensor nodes are deployed over sensing fields for the purpose of monitoring certain phenomena of interest. The sensor nodes perform specific measurements, process the sensed data, and send the data to a base station over a wireless channel. The base station collects data from the sensor nodes, analyses this data, and reports it to the users. Wireless sensor networks are different from traditional networks, because of the following constraints. Typically, a large number of sensor nodes need to be randomly deployed and, in most cases, they are deployed in unreachable environments; however, the sensor nodes may fail, and they are subject to power constraints. Energy is one of the most important design constraints of wireless sensor networks. Energy consumption, in a sensor node, occurs due to many factors, such as: sensing the environment, transmitting and receiving data, processing data, and communication overheads. Since the sensor nodes behave as router nodes for data propagation, of the other sensor nodes to the base station, network connectivity decreases gradually. This may result in disconnected sub networks of sensor nodes. In order to prolong the network's lifetime, energy efficient protocols should be designed for the characteristics of the wireless sensor network. Sensor nodes in different regions of the sensing field can collaborate to aggregate the data that they gathered. Data aggregation is defined as the process of aggregating the data from sensor nodes to reduce redundant transmissions. It reduces a large amount of the data traffic on the network, it requires less energy, and it avoids information overheads by not sending all of the unprocessed data throughout the sensor network. Grouping sensor nodes into clusters is useful because it reduces the energy consumption. The clustering technique can be used to perform data aggregation. The clustering procedure involves the selection of cluster heads in each of the cluster, in order to coordinate the member nodes. The cluster head is responsible for: gathering the sensed data from its cluster's nodes, aggregating the data, and then sending the aggregated data to the base station. An adaptive clustering protocol was introduced to select the heads in the wireless sensor network. The proposed clustering protocol will dynamically change the cluster heads to obtain the best possible performance, based on the remaining energy level of sensor nodes and the average energy of clusters. The OMNET simulator will be used to present the design and implementation of the adaptive clustering protocol and then to evaluate it. This research has conducted extensive simulation experiments, in order to fully study and analyse the proposed energy efficient clustering protocol. It is necessary for all of the sensor nodes to remain alive for as long as possible, since network quality decreases as soon as a set of sensor nodes die. The goal of the energy efficient clustering protocol is to increase the lifetime and stability period of the sensor network. This research also introduces a new bidirectional data gathering protocol. This protocol aims to form a bidirectional ring structure among the sensor nodes, within the cluster, in order to reduce the overall energy consumption and enhance the network's lifetime. A bidirectional data gathering protocol uses a source node to transmit data to the base station, via one or more multiple intermediate cluster heads. It sends data through energy efficient paths to ensure the total energy, needed to route the data, is kept to a minimum. Performance results reveal that the proposed protocol is better in terms of: its network lifetime, energy dissipation, and communication overheads.

As part of the UK’s effort to combat climate change, deep reductions in carbon emissions will be required from existing social housing. This thesis explores the viability of achieving such a goal through a case-study approach, focusing on Peabody, a large housing association operating in London. A model was developed for Peabody’s existing housing stock that quantifies the impacts of technical carbon reduction interventions on stock carbon emissions, Peabody’s expenditure and residents’ fuel bills for the period up to 2030. A participant observation study, conducted from 2006 to 2009, explored the impact of contextual factors influencing the viability of Peabody carrying out the considered technical interventions. The model study found that the Greater London Authority’s target of achieving 60% emission cuts by 2025 could be achieved, but only through extensive stock refurbishment, including a widespread use of solid wall insulation. An external context of substantial reductions in the carbon intensity of the national grid and constrained resident demand for energy is also required. Even where considerable financial support for refurbishment from Government was assumed, the model provided evidence of a funding gap of tens of millions of pounds which would need to be bridged if the required measures were to be carried out. The participant observation study found that the prohibitive cost of carrying out carbon reduction measures is the key barrier currently holding back progress. Other significant issues are related to Government policy, including the inability to raise income from residents to offset refurbishment spending, and the lack of a long term framework to drive action to reduce emissions from existing UK housing. By coupling an analysis of technical interventions with analysis of their financial and political viability, this thesis demonstrates that the achievement of deep emission cuts from Peabody’s existing stock is certainly possible, but requires changes in Government policy and increased efforts from all stakeholders concerned if it is to come to pass.