3 research outputs found
An Efficiency-Focused Design of Direct-DC Loads in Buildings
Despite the recent interest in direct current (DC) power distribution in buildings, the market for DC-ready loads remains small. The existing DC loads in various products or research test beds are not always designed to efficiently leverage the benefits of DC. This work addresses a pressing need for a study into the development of efficient DC loads. In particular, it focuses on documenting and demonstrating how to best leverage a DC input to eliminate or improve conversion stages in a loadās power converter. This work identifies how typical building loads can benefit from DC input, including bath fans, refrigerators, task lights, and zone lighting. It then details the development of several prototypes that demonstrate efficiency savings with DC. The most efficient direct-DC loads are explicitly designed for DC from the ground up, rather than from an AC modification
DC power vs AC power for mobile mining equipment
This paper proposes the use of DC distribution systems in mining applications. In mining a considerable attention is paid to cost optimization per ton of material moved. Therefore, there is a continuous push to use more efficient machines and systems. Electric dragline is the largest excavating machine used in mining, with the least cost per ton and the highest productivity. Any improvement of their electrical system would result in a significant energy saving. On the other hand, DC distribution is an effective method of power delivery which offers a number of advantages including lower electric losses, integration of small distributed generation, better power quality and stability. In this paper, draglines are considered as a case study to verify feasibility of DC distribution systems, in both delivery to a dragline across the mine site and power distribution inside the dragline. Several scenarios are considered, showing the advantages of DC power distribution for DC-based draglines, AC-based draglines, and for effective transition from DC- to AC-based. It will be shown that 12-15% efficiency improvement can be achieved by using the DC distribution system. Moreover, there exist a clear potential for integration of renewable energy sources and energy storage devices, to further improve stability and energy efficiency
Towards Energy-Efficient Electrified Mobile Hydraulics : Considering Varying Application Conditions
In the face of global warming, companies in all kinds of industries need to take measures to reduce the use of fossil fuels, which is explicitly enforced by more and more upcoming emission legislation in many countries. In the case of heavy-duty mobile machines (HDMMs), a currently high-emitting sector, the most feasible method of reducing harmful emissions during operation is battery-based electriļ¬cation. However, the relatively low capacities and high costs of available battery packs are restricting the operation times as well as upper power limits of battery-electric HD-MMsāat least under economically feasible conditions. In this scenario, the typically low energy-eļ¬ciencies of conventional hydraulic systems, which are essential for realizing linear actuation on HDMMs, are becoming more critical than ever before, and more eļ¬cient alternative concepts are required.
As an answer to this demand, this thesis and the six publications on which it is based analyze how alternative hydraulic concepts for electriļ¬ed HDMMs should look like, and two speciļ¬c concepts are proposed as well as evaluated. In this scope, the focus is not only on improving the eļ¬ciency but also on other aspects that can prevent or accelerate the success of alternative hydraulic concepts on the market, such as costs and feasibility. Since those aspects cannot be analyzed in isolation from the application conditions, the essential characteristics of HDMMs and the diļ¬erences of those characteristics between HDMM types are elaborated systematically. Furthermore, the implications of the transition from internal combustion engines (ICEs) to electric machines (EMs) as the prime movers for hydraulic pumps are identiļ¬ed by means of a literature review. Considering the insights from the analyses of those aspects, already existing hydraulic conceptsāi.e., conventional as well as proposed alternatives for improved eļ¬ciencyāare reevaluated, and beneļ¬cial elements of those concepts are ļ¬ltered out for constructing two new concepts.
Those two proposed concepts are characterized by a modular approach in which actuators can be valve-controlled, which might be less eļ¬cient but more cost-eļ¬ective, or pump-controlled, as an alternative for more eļ¬cient yet costly actuation of selected functions on the HDMM. Simulation studies are used to demonstrate the eļ¬ciency of both concepts under varying conļ¬gurations that are enabled through the modular nature of the concepts, and the diļ¬erences in applying them on a telehandler, wheel loader, or excavator are analyzed. For the second concept, which is based on displacement-control and performed best in the simulations, a cost analysis is used to prove additionally that reasonably short payback times of the increased investment costs can be reached in diļ¬erent scenarios. Furthermore, the eļ¬ciency performance as well as feasibilityāin terms of using commercially available components only and achieving good controllabilityāare experimentally validated on a telehandler