A Queueing Theoretic Approach to Decoupling Inventory

This paper investigates the performance of different hybrid push-pull systems with a decoupling inventory at the semi-finished products and reordering thresholds. Raw materials are ‘pushed’ into the semi-finished product inventory and customers ‘pull’ products by placing orders. Furthermore, production of semi-finished products starts when the inventory goes below a certain level, referred to as the threshold value and stops when the inventory attains stock capacity. As performance of the decoupling stock is critical to the overall cost and performance of manufacturing systems, this paper introduces a Markovian model for hybrid push-pull systems. In particular, we focus on a queueing model with two buffers, thereby accounting for both the decoupling stock as well as for possible backlog of orders. By means of numerical examples, we assess the impact of different reordering policies, irregular order arrivals, the set-up time distribution and the order processing time distribution on the performance of hybrid push-pull systems

Technology assessment of solar energy systems: residential use of fuelwood in the Pacific Northwest

The evidence of impacts associated with the use of fuelwood for residential space heating in the region including the states of Washington, Oregon, and Idaho is identified and evaluated. The use of fuelwood for space heating was projected into the future, and then the potential size of the impacts that had been identified and estimated was evaluated. These projections are provided in five year increments beginning in 1980 and proceeding to the year 2000. Policy options are suggested which may mitigate the adverse impacts identified, while preserving the positive effect of reducing residential demand for energy derived from nonrenewable sources

Impact of recent energy legislation on the aluminum industry

This report examines the aluminum industry's technology in energy use and emissions control. Data on consumption and pollution levels are presented. A history of the aluminum industry in the Pacific Northwest, its role in providing power reserves, and how that role fits into the present power situation are given. The Northwest Power Act, the rates the industry will probably pay as a result of the Act, the implications of those rates to the industry, as well as the availability of federal power to the industry are discussed. Finally, the Act's effects on the relative competitiveness of the industry in both domestic and world markets are examined

Identification of energy conservation research opportunities: a review and synthesis of the literature

Thirty-eight studies of energy conservation research opportunities are reviewed. The 38 studies chosen for review include many of the major efforts in the identification of energy conservation research and development (R and D) opportunities and provide a representative sample of the types of studies that have been performed. The sample includes studies that focus on specific energy use (e.g., auto transport), as well as studies that focus on specific types of research (e.g., materials science). The sample also includes studies that can be further contrasted in terms of long-term vs. short-term projects, evolutionary vs. revolutionary ideas, generic vs. process-specific activities, and technology base research vs. hardware development. Each of these perspectives contributes toward assuring coverage of the breadth of energy conservation R and D opportunities. In each review the technical or end-use focus is described, the research ideas identified in the study are listed, and a critical summary is given. The reviews also indicate whether the studies present end-use consumption data, estimate potential energy savings, estimate times to commercialization, summarize existing research programs, or describe the identification methodology. In Section 2.0 the various research studies are compared. In Section 3.0 the characteristics of an aggregate list of research ideas are discussed. The characteristics were collected from the research opportunities studies, which are included in Appendix A. Appendix A contains a compilation of energy conservation R and D opportunities arranged by energy end-use applications. Appendix B contains an outline of the format followed in writing the critical reviews of the studies, the individual study reviews, and the extended bibliography of 88 studies that describe energy conservation research opportunities