Present Worth Cost Research Articles

Economic justification of laboratory automation

Economic justification of laboratory automation

Risk-Based Life-Cycle Cost Analysis for Project-Level Pavement Management

Life-cycle cost analysis (LCCA) is a decision-making tool that highway agencies may use in selecting an optimal pavement preservation strategy. Traditionally, LCCA models for pavement management use discrete input values that represent a conservative best guess of each parameter. Thus, inherent uncertainty associated with each input parameter is not considered. The model developed for this research is probabilistic and derives flexible pavement designs, generates preservation strategies, and evaluates the life-cycle costs of each alternative. Risk analysis is incorporated into the LCCA model so that the inherent uncertainty of each input parameter is considered. Other features of the model include the incorporation of functional aspects (structural capacity and pavement condition) and safety (skid resistance) into the design, the inclusion of rehabilitation and preventive maintenance as preservation strategy alternatives, and the consideration of both agency and user costs in the present-worth cost analysis. The LCCA model output consists of probability distributions that describe the total present-worth cost, the agency present-worth cost, and the user present-worth cost for each preservation strategy over a specified analysis period. The probabilistic nature of this LCCA model exposes areas of uncertainty that may be hidden in a deterministic LCCA model and allows the decision maker to assess the risk associated with each preservation strategy. Finally, a sensitivity analysis was performed to assess the effects of various input parameters on model output. The highway agency can enhance the model output by focusing more detailed data collection and parameter estimation on the model components that were identified as having a statistically significant effect on the model results.

Chemical and Biological Destruction of Cyanide: Comparative Costs in a Cold Climate

Tests were conducted at the Ryan Lode Mine near Fairbanks, Alaska, to determine the comparative costs of chemical and biological destruction of cyanide in mine wastewater. The main body of pond and rinse water was treated by the patented, INCO Air-SO2 process. A 250 ton test heap was built and inoculated with a cyanide-reducing bacterium Pseudomonas pseudoalcaligenes (UA7). The capital and operating costs for both processes were carefully recorded during the treatment. These costs were used as the basis for an analysis of the comparative costs of rinsing and detoxifying a hypothetical, two-million ton heap using each method. Four scenarios were analyzed. The biological method had a higher capital cost, but a significantly lower operating cost, so that the present-worth cost was significantly lower for the biological method.

Optimal planning of rural medium voltage distribution networks

A model is suggested for selection of main initial parameters and timing of the reconstructions of rural distribution networks in long-term planning to meet the increasing load demands with minimum total present worth cost. The model incorporates capital and exploitation costs as well as the costs due to undelivered energy and load curtailments. The optimal investment policy is determined using a constrained dynamic programming technique which indicates the best choice among possible options while taking into account all relevant technical criteria and common-sense rules.

Pilot testing of reverse osmosis for salinity and organics control in a coastal supply source

The results of pilot testing demonstrate that RO can be used successfully on conventionally treated Northwest River water to control seasonal salinity increases and reduce disinfection by-products in the finished water to the more stringent levels anticipated under the forthcoming disinfectants/disinfection by-products (D/DBP) rule. Both cellulose acetate (CA) and thin-film composite (TFC) membranes can be operated satisfactorily on alumtreated river water. As anticipated, the CA membranes demonstrate lower levels of fouling; however, the TFC membrane provide greater organics removals. The membranes most appropriate for the future full-scale plant will be determined from a present-worth cost evaluation of CA and TFC membrane capital and operating costs.

FINANCIAL EVALUATION OF SOCIAL FORESTRY IN TANZANIA AS AN AID TO FOREST EXTENSION: THE MAGADU VILLAGE CASE STUDY

SUMMARY A rapid appraisal survey was carried out in Magadu village to identify possible intervention strategies for village forestry. To assist in species choice for planting, land expectation value, present net worth and benefit cost ratio were tested. These different decision criteria give different rankings. In the final deliberation, people's needs are important determinants. Possible strategies for village forestry in Magadu are identified. The methodology adopted in this study can be useful in assisting forest extensionists in planning village forestry in TAnzania and elsewhere.

Life cycle and present worth cost concepts, applicable for large desalting plants?

As the degree of sophistication and complexity, and the size of dual purpose power — desalting plants increases, several economic methodologies, by which these plants are evaluated, are emerging. The evaluation methodology selected for a project is important to those involved with the plant's technical aspects. Unfortunately some economic methodologies are not well understood within the desalination profession. It is the purpose of this paper to outline several methodologies being used today, and to illustrate, with examples, the different costs that result.

Selection, design, and procurement of a demineralization system for a surface water treatment plant

Reverse osmosis (RO) and electrodialysis reversal (EDR) were pilot tested in conjunction with the design of a surface water treatment plant for the City of Sherman, Texas. The supply was water from Lake Texoma, a brackish source having a high scaling potential for calcium and barium sulfate. Test results showed both to be suitable for demineralizing the lake water; however, RO was found to be more susceptible to scaling by sulfate salts. Design and contract documents were prepared around the use of either technology to provide a cost-competitive procurement. Twenty-year present worth cost was used as the basis of contract award. The demineralization system equipment specifications incorporated requirements that reflected the inherent process advantage of EDR for this application, based on EDR's ability to operate at greater recovery without the need for continuous chemical addition for scale control (based on side-by-side pilot testing with RO). The initial 7.5-mgd plant capacity, currently under construction, will include three 1.5-mgd EDR trains, for a total EDR capacity of 4.5 mgd. Each train will contain two hydraulic stages for approximately 75 percent TDS removal.

Reduced neutral XLPE cable design

The authors describe the theoretical, laboratory, and economic analyses undertaken by B.C. Hydro to determine the optimum metallic concentric neutral design for its single-conductor 750 and 500 kcmil aluminum XLPE (cross-linked polyethylene) 15 kV and 25 kV insulated concentric-neutral-type feeder cables. The results suggest that reducing the cross-section area of this concentric neutral from the currently recognized industry standard of 20% of the central conductor to 7% results in an overall present-worth system cost saving of approximately $3 per conductor meter or approximately 22% of the cable first cost. The neutral configuration ultimately chosen to replace the previous standard 37 Hash 14 AWG wires was two 1-in*5 mil tinned copper tapes overlapped by 25%. Line voltage fault tests were run in the high-power laboratory on samples with various neutral configurations to confirm that they would successfully pass the worst-case fault duty of 10 kA for 20 cycles (i.e. .33 s) with no reclosing. >

The calculation of the present worth single payment factors for reliability systems when life cycle is arbitrary

Life cycle costs are the total costs of a system over its lifetime. The present worth of these costs may be used to compare and select economic alternatives—especially at the design stage. For a system with uncertain lifetime, the present worth cost is a function of the system lifetime distribution and the compound interest rate. In this paper, the present worth single payment factors for a stochastically operating and continuously commissioned system are developed. The factors represent reality by taking into consideration the arbitraries in the system life cycle as determined by the user.

Computer‐Assisted Procedure for Subdivision Cost Analysis

The Residential Area Cost Analysis Model (RACAM)—a computer model designed to calculate the construction, operation and maintenance costs of alternative residential subdivision designs—is presented. A procedure for preliminary design is described which calculates the present worth and annual cost for domestic sewer, storm sewer, and water distribution systems; gas, power and telephone systems; road, sidewalk and street lighting systems; and park and buffer systems. Results of applying the model to subdivisions proposed in Hamilton, Ontario and Regina, Saskatchewan are presented. The paper concludes that RACAM, in addition to other new modeling procedures, can provide development cost information which can assist in the assessment of proposed residential subdivisions.

Development and Application of Linear Programming Planning Methods for Pumped Storage Hydro

A linear programming model for electric generation planning has been extended to provide the options required for pumped storage hydro planning. Pumped storage hydro is defined by installed capacity and capacity factor. The corresponding four options desirable planning purposes are the capability to 1) specify capacity factor and solve for optimal installed capacity or 2) solve for both optimal installed capacity and capacity factor. The model calculates the total electric planning strategy that minimizes present worth cost, or any other objective specified by the planner subject to the input option and data base. The planner can also perform the primary and secondary objective analysis via a sequential objective feature.

Sequential Objective Linear Programming for Generation Planning

Generation planning usually involves finding a generation expansion and operating policy that minimizes present worth cost while meeting projected demands and other imposed constraints. However, the planning process is becoming increasingly complex with a number of objectives becoming increasingly desirable. In addition to minimum revenue requirements, other possible objectives include minization of new power plant construction, maximization of reliability, minimization of public health hazard (e.g. via emitted pollutants), and minimization of environmental hazards (e.g. via heat rejected to bodies of water).

CONJUNCTIVE USE OF SEA AND FRESH WATER RESOURCES: AN INTEGER PROGRAMMING APPROACH1

ABSTRACTMathematical models are formulated for selection of water resources projects to meet the future additional water requirements of a given region at the minimum present worth cost. The projects available are surface water reservoirs and desalination plants. The modles are used for selecting both the development sequence of projects and their optimum sizes. Decisions with regard to planning time horizon and discount rates are made outside of the mathematical model.The algorithm used for solving these models is an integer programming routine using the implicit enumeration technique. Some computational results are presented for a hypothetical case.

Planning of Systems

The methodology of planning systems to meet stated goals in an optimum manner while recognizing all pertinent constraints is being given increasing attention by systems engineers. In the electric utility industry the greatly increased complexity of the systems required to meet anticipated load growth, the advent of large-scale interconnection of systems, increasing investment costs and the pressure for continued economy of service have necessitated continuing efforts to achieve more comprehensive and exacting approaches to system planning. Significant progress in system planning has been achieved to date in the electric utility industry. Integrated digital computer programs have been devised which permit the modeling of the technical and economic performance of future system design alternatives and aid the system planner in obtaining an optimum total system beginning with the sources of fuel and ending with the final delivery of power to the customer. By the methods presented in this paper the total present worth cost of various alternative system designs may be readily obtained. Limited work has been undertaken concerning the direct optimum synthesis of a system plan. The major difficulty in direct synthesis arises from the complex interrelationships of the variables and the high dimensionality of the problem.