The objective of this paper is to develop a methodology to determine how many houses could be fueled from the solar energy captured by a number of solar Stirling modules (with a fixed dish area per module) and also to determine the minimum necessary area of the fuel cell to ensure the amount of power needed to meet daily energy use requirements. The detailed method includes the effect of the fuel cell efficiency function on the power consumption of the user. Experimental data from our laboratory are used to determine the fuel cell efficiency as a function of the electric current density for a specific power demand. As an illustrative example, the analysis is applied to a residential area having a specific electrical demand. Using the developed method, the number of houses that could be fueled directly by the stored hydrogen is determined, and also the minim fuel cell area required.

Entropy generation calculation for the reversed cycle Carnot machine is presented. It is based on recent developments using the Direct Method and the Finite Speed Thermodynamics. The Direct Method consists in analyzing any irreversible cycle, step by step, on each process, by writing the corresponding equation of the First Law of Thermodynamics for Finite Speed Processes and integrating it on the whole cycle. The First Law expression for Finite Speed Processes includes principal sources of internal irreversibility and it is used here to develop equations that relate properties for each irreversible process that may occur with finite speed in the reversed cycle Carnot machine. This paper includes expressions for calculating the internal entropy generation as a function of the finite speed of the process and also as a function of other parameters such as the temperature of the gas, compression/expansion ratio, and mass flow rate and gas properties for the adiabatic finite speed processes of reversed Carnot cycle machines. An example is presented to illustrate how these expressions can be used to validate the internal entropy generation rate evaluation based on proposed equations in the literature for a real operating refrigeration machine for which experimental data are available. For this purpose an equivalent reversed Carnot cycle is considered instead of the real cycle. It results from experimental data using appropriate approximations for evaporator and condenser processes.

The paper by Harwell and Gentile (2006) published in this issue of Integrated Environmental Assessment and Management (IEAM) reviews the ecological significance and persistence of impacts associated with the 1989 Exxon Valdez oil spill in Prince William Sound, Alaska. Reviewing the considerable body of ecological, ecotoxicological, and biological studies conducted in the years preceding the oil spill and during the 17 years after the oil spill, the authors attempt to address the question often asked following environmental catastrophes similar to this one: In the years following the Exxon Valdez oil spill, are there any remaining and continuing ecologically significant exposures or effects on the Prince William Sound ecosystem directly attributable to the oil spill? We are proud to provide the peer-reviewed forum for these authors to ask and answer this important scientific question. The mission of a scientific journal is to publish manuscripts that are consistent with the scope of the journal and that have undergone a rigorous peer-review process. In the case of IEAM, the mission involves integrating scientific research with environmental management in an open forum that encourages hypothesis-testing, fosters technical discussion (including debate), and promotes new ideas and approaches to resolve difficult and complex environmental challenges. IEAM challenges scientists and environmental managers to ask and answer the ‘‘so what’’ and ‘‘what if ’’ questions. The nature and extent of residual impacts from the Exxon Valdez oil spill is the subject of significant on-going scientific, regulatory, and public debate and controversy, as demonstrated by the recent newsmagazine article appearing in Time (Caplan 2006) in recognition of the anniversary of the oil spill. Consistent with the high standards of peer-review required by the Society of Environmental Toxicology and Chemistry (SETAC) and its members and recognizing the varied and strongly-held viewpoints surrounding this anniversary, the manuscript submitted by Harwell and Gentile was reviewed by 16 anonymous reviewers, including several members of the IEAM Founding Editorial Board. The authors are commended for their patience and their careful attention to comments and criticisms raised by reviewers during the preparation of their final manuscript. The final acceptance and publication of the Harwell and Gentile paper reflects a determination by the Editor-in-Chief and the Founding Editorial Board that the paper is substantive and worthy of publication. The publication of this paper does not, however, imply that IEAM endorses the authors’ findings as scientific truth. The paper reflects the authors’ interpretations of the extraordinarily comprehensive set of ecological studies performed following the oil spill. The Founding Editorial Board is aware that others may have different interpretations of the same studies, and that others may be able to point to different studies supporting contrary interpretations and conclusions. It is our hope and expectation that publication of the Harwell and Gentile paper will stimulate a productive, scientific debate concerning the nature of the residual impacts remaining nearly 2 decades after the Exxon Valdez oil spill and about the prognosis for continued recovery of the Prince William Sound ecosystem. The Founding Editorial Board of IEAM invites reaction to this paper and additional analysis that contributes to assessment of the ecological status of Prince William Sound; we will consider them in future issues of the journal, in accordance with our peer-review process. It is only by examination of the successes and weaknesses of our collective responses to the oil spill that we might learn from the event, avoid mistakes (if any), and improve our ability to respond to similar catastrophes in the future.

A Carnot engine operating on a closed cycle and having both external and internal irreversibilities is analyzed. The internal irreversibilities are caused by losses generate by finite piston speed and the external irreversibilities are caused by heat transfer through a temperature difference. The irreversible Carnot cycle is displayed on a original T-S property coordinates in a manner that accurately illustrates the lost work (Exergy losses) due to the irreversibilities (internal and external). A method for calculating the effect of the piston speed on the internal irreversibilities of Carnot cycle is developed and an example of the results is shown for a range of values of cycle high temperature (2000 K). Using the results of this example, the optimal Carnot engine efficiency is determined as a function of piston speed. The example is extended to include the determination of the optimal system temperature for Maximum Carnot engine power over a range of piston speeds.