Asfaw Beyene

California Wave Energy Resource Evaluation

Abstract In this article, a collection of deep water (>100 m) wave records was assessed to create a long-term, statistically reliable data set. These wave data were derived from buoy data of the Coastal Information Data Program (CDIP) at the University of California, San Diego (UCSD), Scripps Institute of Oceanography; the National Data Buoy Center (NDBC) at the National Oceanic and Atmospheric Administration (NOAA); and other sources. From this data set, long-term annual averages and monthly wave probability distributions were analyzed for 10 one-degree-latitude bins, bounded by the 100-m and 1000-m depth contours seaward of the California coast. The probability distributions were used to quantify the potential for useful energy extraction from the coastal waves of California. Optimal locations for developing wave energy installations are specified. South of Point Conception, California, the wave energy arriving from North Pacific storms is efficiently blocked by the significant change in the California coast orientation south of Point Conception and the Channel Islands. The near-coastal Southern California (SOCAL) region has a significantly reduced wave resource compared with the California coast north of Point Conception.

A comparison of the field performance of thermal energy storage (TES) and conventional chiller systems

The field performance of thermal energy storage (TES) systems was compared to the “simulated field performance” of conventional systems. Field data for several TES sites, provided by the Electric Power Research Institute (EPRI), were analysed using a “mean-day” and “peak-day” approach. Parameters were developed that allow a meaningful and comprehensive performance comparison of TES and conventional systems. Energy use (kW/ton), as well as the direct power costs of ice, chilled water and eutectic salt systems were compared to that for conventional systems. This showed that the field performance of TES systems is better than expected.

Recent Advances in Rotor Design of Vertical Axis Wind Turbines

The following work represents the most recent advances in design and testing of vertical axis wind turbines (VAWT) rotors. VAWTs have received much attention as of late due to proposed advantages in small scale and off grid wind power generation. Thus, many recent works have surfaced involving analysis, design and optimization of VAWT rotors in order to more efficiently convert wind energy to electricity or other readily usable means. This paper is a collection of most of the recent literature works involving VAWT rotor design and testing, the majority of which published after 2005. We discuss research in the designing of various lift based rotors as well as some drag based rotors, hybrids, and various others. The recent work in this area suggests VAWT capacity could dramatically increase in the near future, and play a vital role in obtaining cleaner, more sustainable energy when global energy demand is increasing at an unprecedented rate. HIGHLIGHTS A review of various works involving rotor design and testing of both lift and drag Vertical Axis Wind Turbines (VAWTs) is presented; Benefits of vertical axis wind turbines in small scale and off grid wind power generation is summarized; Much of the recent work, published after 2005, has been directed towards analyzing, designing, and optimizing rotor shapes. The body of this recent work suggests that research on VAWT rotor design continues to flourish and could make VAWTs a viable competitor to more traditional Horizontal Axis Wind Turbines (HAWTs) worldwide.

Design, Analysis and Optimization of a Micro-CHP System Based on Organic Rankine Cycle for Ultralow Grade Thermal Energy Recovery

This paper presents the results of the application of an advanced thermodynamic model developed by the authors for the simulation of Organic Rankine Cycles (ORCs). The model allows ORC simulation both for steady and transient analysis. The expander, selected to be a scroll expander, is modeled in detail by decomposing the behavior of the fluid stream into several steps. The energy source is coupled with the system through a plate heat exchanger (PHE), which is modeled using an iterative sub-heat exchanger modeling approach. The considered ORC system uses solar thermal energy for ultralow grade thermal energy recovery. The simulation model is used to investigate the influence of ORC characteristic parameters related to the working medium, hot reservoir and component efficiencies for the purpose of optimizing the ORC system efficiency and power output. Moreover, dynamic response of the ORC is also evaluated for two scenarios, i.e. (i) supplying electricity for a typical residential user and (ii) being driven by a hot reservoir. Finally, the simulation model is used to evaluate ORC capability to meet electric, thermal and cooling loads of a single residential building, for typical temperatures of the hot water exiting from a solar collector.

Experimental Implementation of a Micro-Scale ORC-Based CHP Energy System for Domestic Applications

Because of the renewed interest in renewable energy as well as increased emphasis on alternative technologies, micropower-generating systems have attracted considerable research interest over the last decade. However, micro-scale power generation for low grade heat recovery applications, i.e. as low as 1–3 kW - for domestic use, are characterized by very low efficiencies and relatively high specific cost. For economic viability, these factors make it imperative that the heat source remains “free”, such as solar or geothermal energy. In this paper, a small-scale Organic Rankine Cycle (ORC) is presented. The small-scale ORC module was built and tested at San Diego State University lab, aimed at producing electricity and hot water from ultra-low grade heat source that can be tapped from solar collectors and low temperature exhaust heat. The system was built for economic viability and flexibility, tailored for a domestic use. The tests demonstrated that the system offered CHP capability, with electric and thermal power output suitable for a domestic application. It also offered high operational flexibility, since the scroll expander could work with a high temperature range, accommodating an even-significant drop of the heat source temperature. Therefore, it can be conveniently used to capture solar and low-temperature energy sources. The system could be produced at an overall cost of less than

Energy Efficiency and Industrial Classification

3,000 (USD 2010).Copyright

Sizing CCHP Systems for Variable and Non-coincident Loads

In this article, energy consumption data for 300 manufacturing plants in Southern California are collected and analyzed by standard industrial classification (SIC) code. The results show that in order of magnitude, combined heat and power (CHP), variable speed drive (VSD), and compressed air systems offer the largest opportunities to reduce energy use in small and medium sized manufacturing plants. It also follows that the SIC is not a convenient tool to classify energy use, and in fact, to date there is no such convenient code to sort manufacturing plants by their energy intensity. The energy use profile cannot be systematically fitted to existing industry classification for the group of targeted plants. Opportunities and challenges related to capturing the potential energy savings in small and medium sized plants are also summarized.

Combined Heat and Power Sizing Methodology

ABSTRACT Because of its superior efficiency and peak load mitigation capabilities, considerable attention has been given recently to combined cooling, heating and power(CCHP). The technology enjoys tax benefits, incentives, accelerated permit processes, etc., at the local, state, and federal levels. One serious challenge to the implementation of CCHP systems is matching and sizing the system to strongly and frequently varying load conditions. Load variation is a serious design matter because the system efficiency drops significantly at part-load. This article presents matching and sizing related challenges of CCHP systems with emphasis on operation-related and weather-driven load factors. Regional data were used to evaluate the success of recent incentive-driven CCHP implementations and evaluate the significance of part-load operation on system performance. Load profiling strategies are developed for equipment sizing and selection to mitigate part-load issues and address system flexibilities.

Feasibility Study of Low Grade Heat Recovery Rankine Cycle Using Ozone-Neutral Refrigerant

As deregulation of the electric market finds legitimate global acceptance, more efficient alternatives to centralized power production, such as the Combined Heat and Power (CHP), also known as cogeneration, are finding growing reception. Advances in sizing methodologies, selection criteria, and control technologies, as well as development of associated regulatory issues, must accompany this favorable disposition. This paper presents an overview of some important applications of a heat recovery system and discusses a simplified method of sizing a CHP as a part of an early feasibility decision.Copyright

Sizing CCHP Systems for Variable and Non-coincident Loads, Part 2: Operating Strategies

The paper addresses the feasibility of ozone-neutral low grade heat recovery to produce power. The low grade heat source can either be industrial exhaust or solar radiation. Using a scroll expander as a basis for testing, theoretical models yielded a thermal efficiency of 11%, utilizing a non-toxic and non-hazardous working fluid. This project spanned research and development of a system from the comparison of several working fluids, modeling of a theoretical 10 kW unit, the sizing and selection of appropriate system components, and the development of project management tools, in support of its real world development. A cost benefit analysis of the theoretical system shows that solar heat recovery with ozone-neutral refrigerant is a viable option for power generation, at about 1/3 the cost of a comparable photovoltaic system.Copyright