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The design of the latent heat thermal storage system (LHTESS) was developed with a thermal capacity of about 100 kW h as a part of small solar plant based on the organic Rankine cycle (ORC). The phase change material (PCM) used is solar salt with the melting/solidification temperature of about 220 °C. Thermophysical properties of the PCM were measured, including its phase transition temperature, heat of fusion, specific heat, and thermal conductivity. The design of the thermal storage was finalized by means of the 3D computational fluid dynamics analysis. The thermal storage system is modular, and the thermal energy is delivered with the use of thermal oil, heated by Fresnel mirrors. The heat is transferred into and from the PCM in the casing using bidirectional heat pipes, filled with water. A set of metallic screens are installed in the box with the pitch of 8–10 mm to enhance the heat transfer from heat pipes to the PCM and vice-versa during the charging and discharging processes, which take about 4 h. This work presents a numerical study on the use of metallic fins without thermal bonding as a heat transfer enhancement method for the solar salt LHTESS. The results show that the absence of the thermal bonding between fins and heat pipes (there was a gap of 0.5 mm between them) did not result in a significant reduction of charging or discharging periods. As expected, aluminum fins provide better performance in comparison with steel ones due to the difference in the material conductivity. The main advantage observed for the case of using aluminum fins was the lower temperature gradient across the LHTESS.

The small solar thermal power plant is being developed with funding from EU Horizon 2020 Program. The plant is configured around a 2-kWel Organic Rankine Cycle turbine and solar field, made of Fresnel mirrors. The solar field is used to heat thermal oil to the temperature of about 240 oC. This thermal energy is used to run the Organic Rankine Cycle turbine and the heat rejected in its condenser (about 18-kWth) is utilized for hot water production and living space heating. The plant is equipped with a latent heat thermal storage to extend its operation by about 4 hours during the evening building occupancy period. The phase change material used is Solar salt with the melting/solidification point at about 220 oC. The total mass of the PCM is about 3,800 kg and the thermal storage capacity is about 100 kWh. The operation of the plant is monitored by a central controller unit. The main components of the plant are being manufactured and laboratory tested with the aim to assemble the plant at the demonstration site, located in Catalonia, Spain. At the first stage of investigations the ORC turbine will be directly integrated with the solar filed to evaluate their joint performance. During the second stage of tests, the Latent Heat Thermal Storage will be incorporated into the plant and its performance during the charging and discharging processes will be investigated. It is planned that the continuous filed tests of the whole plant will be performed during the 2018- 2019 period. This study was funded by European Union’s Horizon 2020 Research and Innovation Program under Project Grant Agreement 723596 (Innova MicroSolar).

The design of the Latent Heat Thermal Storage System (LHTESS) was developed with thermal capacity of about 100 kWh as a part of small solar plant, based on the Organic Rankine Cycle (ORC). The phase change material (PCM) used is Solar salt with the melting/solidification temperature of about 220°C. Thermo-physical properties of the PCM were measured, including its phase transition temperature, heat of fusion, specific heat and thermal conductivity. The design of the thermal storage was finalized by means of the 3-D CFD analysis. The thermal storage system is made of six rectangular boxes with dimensions of 1 m (width) × 0.66 m (height) × 0.47 m (depth). The thermal energy is delivered to each of the thermal storage boxes with the use of thermal oil, heated by Fresnel mirrors. The heat is transferred into and from the PCM in the box using 40 bi-directional heat pipes with the external diameter of about 12 mm. The length of the heat pipe in the PCM box is 430 mm and it is placed in the cylindrical metallic protection cartridge, installed in the thermal storage vessel. The working fluid in the heat pipe is water. A set of metallic screens are installed in the box with the pitch of 8–10 mm to enhance the heat transfer from heat pipes to the PCM and vice-versa during the charging and discharging processes, which take about 4 hours. The one unit of the described thermal storage system is undergoing the laboratory tests. Preliminary results demonstrate that the performance of the thermal storage is in a good agreement with numerical predictions. After completion of final design modifications, all units will be assembled at the plant’s demonstration site and tested with the ORC turbine.

The articles in this special issue focus on solar power generation, including new technologies, services, and applications.

Aims The aim of this study was to evaluate the safety, technical feasibility and performance of a new trans-catheter tricuspid repair system. Methods and results Thirty-one adult swine underwent implantation of a transcatheter tricuspid remodelling system under general anaesthesia. The steerable transcatheter device was introduced through a 24 Fr femoral sheath into the right femoral vein and delivered to the tricuspid annulus on the beating heart. A fixation element was implanted into the tricuspid annulus. Following implantation, a second delivery system was used to couple the fixation element with a self-expanding nitinol stent. The device was tensioned to reshape the tricuspid valve and increase the coaptation length of the valve leaflets under echo guidance. Finally, the stent was deployed in the inferior vena cava (IVC) to maintain the tension applied. The transcatheter device was successfully implanted in all animals (n=31). Doppler echocardiography prior to sacrifice showed that tricuspid valve function was stable and normal tricuspid leaflet motion was observed. Cinching of the tricuspid annulus resulted in an increase of leaflet coaptation length of 70% (4.5±0.7 mm to 7.78±1.3 mm), an increase in trans-tricuspid peak velocity of 79% (0.38±0.1 m/s to 0.68±0.1 m/s), and a reduction in septolateral tricuspid valve dimension of 30% (35.2±5 mm to 24.8±5 mm). At necropsy, the fixation element was firmly attached to the annulus within a fibrotic tissue, with no coronary lesions observed and no abnormality visible. The stent was fully deployed in the IVC, without displacement or change in the stent shape. Conclusions Percutaneous beating heart remodelling of the tricuspid annulus with a cinching device is safe and feasible.

Although higher education understands the need to develop critical thinkers, it has not lived up to the task consistently. Students are graduating deficient in these skills, unprepared to think critically once in the workforce. Limited development of cognitive processing skills leads to less effective leaders. Various definitions of critical thinking are examined to develop a general construct to guide the discussion as critical thinking is linked to constructivism, leadership, and education. Most pedagogy is content‐based built on deep knowledge. Successful critical thinking pedagogy is moving away from this paradigm, teaching students to think complexly. Some of the challenges faced by higher education moving to a critical thinking curricula are discussed, and recommendations are offered for improving outcomes.

This article examines how wind and solar integration studies have evolved, what analysis techniques work, what common mistakes are still made, and what and why calculating integration costs is such a difficult problem that should be undertaken carefully, if at all. Examples of integration costs for other generation technologies are examined to help illuminate underlying cost causation principles.

The last two years have seen a tremendous increase in the number of installed solar energy systems. In 2010, annual grid-connected photovoltaic (PV) installations in the United States and worldwide were expected to be about 0.8 GW and 16–18 GW, respectively. At the end of 2010, the cumulative installed base of grid-connected PVs in the United States and worldwide was about 2 GW and about 40 GW, respectively. One of the areas that has been receiving much attention recently is large utility-scale solar systems.

Future decision makers in natural resource fields will be required to make judgments on issues that lack clear solutions and with information complicated by ethical challenges. Therefore, natural resource, environmental, and agricultural professionals must possess the ability to think critically about the consequences of policy, economic systems, and individual human behaviors on the environment. To ensure that future professionals can examine competing claims, university students must develop critical thinking skills that allow them to examine ethical issues surrounding the environment. We review literature on critical thinking specifically in regard to necessary components to creating critical thinking opportunities in the classroom. We then discuss special considerations for teaching critical thinking in the context of natural resource and agriculture ethics education.

Healthcare organizations suffer from a disparate distribution of racial and ethnic minority employees in professional positions. Although the percentage of racial and ethnic minorities in the workforce continues to grow, the percentage of racial and ethnic minorities who compose the professional ranks, nursing and managerial positions, lags far behind the percentage of White individuals in similar positions. This gap has implications for organizational performance as research indicates organizations with more diverse workforces enjoy better outcomes. A more diverse workforce also has broader societal consequences directly tied to healthcare such as positively impacting health disparities. The authors posit that recruitment is critical to developing a diverse workforce.

The SunShot Vision Study defines a scenario for solar energy technologies to significantly contribute to meeting U.S. electricity demand. To achieve this, work is in progress to identify, quantify, and address the impacts of high levels of distributed PV generation on electric distribution systems. The Department of Energy (DOE) Solar Energy Technologies Program (SETP) initiated a project to gain experience and to identify and quantify these potential impacts, develop and verify models of these systems, evaluate methods for mitigating any impacts, and develop potential solutions. This paper summarizes the current progress of the six competitively selected projects.

Solar photovoltaics (PV) is the dominant type of distributed generation (DG) technology interconnected to electric distribution systems in the United States, and deployment of PV systems continues to increase rapidly. Considering the rapid growth and widespread deployment of PV systems in United States electric distribution grids, it is important that interconnection procedures be as streamlined as possible to avoid unnecessary interconnection studies, costs, and delays. Because many PV interconnection applications involve high penetration scenarios, the process needs to allow for a sufficiently rigorous technical evaluation to identify and address possible system impacts. Existing interconnection procedures are designed to balance the need for efficiency and technical rigor for all DG. However, there is an implicit expectation that those procedures will be updated over time in order to remain relevant with respect to evolving standards, technology, and practical experience. Modifications to interconnection screens and procedures must focus on maintaining or improving safety and reliability, as well as accurately allocating costs and improving expediency of the interconnection process. This paper evaluates the origins and usefulness of the capacity penetration screen, offers potential short-term solutions which could effectively allow fast-track interconnection to many PV system applications, and considers longer-term solutions for increasing PV deployment levels in a safe and reliable manner while reducing or eliminating the emphasis on the penetration screen.

This white paper evaluates the origins and usefulness of the capacity penetration screen, offer short-term solutions which could effectively allow fast-track interconnection to many PV system applications, and considers longer-term solutions for increasing PV deployment levels in a safe and reliable manner while reducing or eliminating the emphasis on the penetration screen. Short-term and longer-term alternatives approaches are offered as examples; however, specific modifications to screening procedures should be discussed with stakeholders and must ultimately be adopted by state and federal regulatory bodies.

While the number of PV systems interconnected to the electric grid has increased significantly over the last decade, only recently have PV systems been installed in major metropolitan areas and tied to electric distribution secondary network systems (networks). This paper examines six cases studies of photovoltaic (PV) systems integrated into secondary network systems. The six PV systems were chosen for evaluation because they are interconnected successfully to secondary network systems located in four major U.S. Cities.

In January of 2003, the Florida Department of Environmental Protection/Florida Energy Office (DEP/FEO) allocated $600,000 in hardware funds toward the installation of photovoltaic (PV) solar systems on Florida schools. As a result of this program, grid-connected PV systems less than six kilowatts in size were installed on 29 schools in the State of Florida. The Florida Solar Energy Center (FSEC) has monitored these systems for approximately one year of operation. The performance of 28 of these systems was analyzed using standard performance parameters such as the performance ratio, PV array efficiency, inverter efficiency, and PV system efficiency. In addition, a life-cycle cost analysis was conducted using new cost data values and updated market assumptions. These data will serve as a benchmark to compare against future systems with respect to performance vs. installed system cost.Copyright © 2006 by ASME

The Florida Solar Energy Center (FSEC) has partnered with Sandia National Laboratories (SNL), the Southwest Technical Development Institute (SWTDI), and the California Energy Commissions Public Interest Energy Research (CEC PIER) in an effort to characterize the performance of PV inverters operating over extended periods of time. As part of this characterization, SNL executed an initial performance characterization in the laboratory to be repeated at one or two year intervals. These inverters were then sent distributed to the above test facilities for installation and long-term testing. To perform this long-term testing, FSEC built an inverter test facility made up of a configurable 10.1 kW PV array and four test beds. Each test bed was set up to monitor the following parameters: DC voltage, DC current, AC Voltage, AC Power and inverter temperature. Solar irradiance, ambient temperature, and several PV array temperatures were recorded by a separate, synchronized datalogger. Three inverters are currently being tested: the Fronius IG 3000, the Xantrex GT 3.0, and the SMA Sunny Boy 2500U. The three inverters were loaded with a PV array close to the maximum power limit allowed by the inverter, and the array power supplied to each inverter was within 100 W of one another. Since the PV array for each inverter used identical PV modules mounted in the same orientation, it was easier to develop a model to compare inverter performance based on energy output. In addition to energy output, other parameters were obtained such as inverter efficiency. An attempt was made to compare the results obtained at FSEC to those results compiled by the California Energy Commission.Copyright © 2006 by ASME

This analysis expands the photovoltaic (PV) life cycle cost (LCC) results presented at ASES 2004. That paper presented the model and concept used to develop PV LCC, and it showed the results of the analysis of over one hundred systems monitored by the Florida Solar Energy Center (FSEC). FSEC began tracking cost, performance and reliability data for systems installed in Florida in 1998, with data now available through a web-accessible database. For the majority of the 124 systems, installed cost information was collected as part of the state’s PV rebate and PV for schools programs. Results presented previously [1] indicated that over an assumed 20–30 system life time a PV system will have a positive life cycle cost. That is, a negative total return on investment. These results were based on actual cost, performance, maintenance, and reliability data. In the baseline case, average total system costs over the lifetime were 32.4¢/kWh while electricity savings totaled 3.7¢/kWh netting a life cycle cost of 28.7¢/kWh. While based on actual data from over 100 installed systems — some installed for over 6 years — a number of conservative assumptions also drove the analysis, such as the exclusion of the state’s rebate programs (varying from $2 to $5 per DC Watt) which impacted nearly all of the systems in the analysis. Since the first presentation of these results the PV LCC model has been further developed to incorporate additional performance information and expands the sample of systems incorporated. This paper will thus provide further insight into the relative importance of various up-front and on-going costs to the overall lifetime economics of a system. The paper will also address additional sensitivity analysis performed. Particular attention is paid to inverter mean time between failure (MTBF), the impact of incentives, and basic financial assumptions used in the model such as the discount rate and electricity rates. Various scenarios are considered in asking the question of what is necessary for the system LCC to break-even.Copyright © 2005 by ASME

Between April 2001 and September 2002, the Florida Solar Energy Center conducted research to evaluate the performance of several utility-interactive inverters. The major issues to be identified were the efficiency of the inverters and their ability to follow the maximum power point of the photovoltaic (PV) array. Existing PV testing facilities at FSEC were modified to carry out this analysis. This facility, called the Photovoltaic Inverter Test Facility, is capable of providing approximately four kWp of array power to the inverter. Data on inverter performance were collected using a Campbell 10X datalogger. The parameters collected included the following: irradiance, PV array temperature, inverter temperature, PV voltage, PV current, AC voltage, AC current, and AC Power. Because of the voltage windows and power requirements of the different inverters, the array was designed to be easily reconfigured to meet those requirements. Each of the inverters was installed and allowed to run for several weeks under both clear and cloudy conditions. At the end of the test period, inverter efficiencies were calculated from the collected data. The ability of the inverter to follow the maximum power point of the array was evaluated in two ways. In the first method, DC voltage and current were measured while the inverter was operating, then the array was disconnected from the inverter and the maximum power point of the array was immediately taken. By comparing the measured DC voltage and current to the maximum power point of the array, one could determine the effectiveness of the inverter algorithm. Unfortunately this method requires steady-state conditions and does not show the effectiveness of the algorithm in cloudy conditions. To determine its effectiveness in cloudy conditions, DC voltage and current were compared to the expected maximum power. The expected array maximum power point was calculated from IV curves of the array, irradiance measurements, and array temperature measurements. DC to AC efficiency curves were derived from the data as well. Results from the inverters were mixed, but several showed room for improvement.

The Florida Solar Energy Center has been accredited by both the American Association for Laboratory Accreditation and PowerMark Corporation to certify grid-tied photovoltaic systems. The certification process involves both the testing of photovoltaic modules for performance ratings and the review and approval of system designs to provide photovoltaic system design certification. This paper focuses on the design review and approval process, which consists of a documentation review and focuses on the completeness and accuracy of instructions, schematics, and accompanying materials. System designers have received substantive critiques and assistance through the third-party technical reviews used in this process. As a result, photovoltaic system manuals that accompany reviewed systems lead to a greater likelihood of code-compliant and high-performing installations.

The lack of consistently high performance from inverters has created numerous issues in the widespread application and confidence in grid-tied photovoltaic systems. Additionally, the lack of a metric by which inverter manufacturers can evaluate their products presents a challenge to manufacturers by not allowing them to distinguish their products from those of their competitor, and to users since there is no way of comparing seemingly-similar models. This problem is further compounded by the dearth of inverters that have high performance and reliability [1]. This document is the first draft of a test protocol under development at the Florida Solar Energy Center to assist in this area. A need for such a test protocol has been recognized nationally, and it is hoped that this document may provide a foundation for future test procedures while providing significant and reasonable findings in the interim.Copyright © 2002 by ASME

One of the goals of the Florida PV Buildings Program is to ensure that only quality utility-interactive PV systems are installed in the state. One important component of the Program is the site survey. The purpose of the site survey is to inspect the potential location for PV system before beginning construction, ensuring it is a sensible place to install it. The purpose of this paper is to introduce the method used by this Program and to present some examples that will demonstrate why it is important.

The field of photovoltaics has undergone dramatic growth over the past few years. This growth has been accompanied by two significant changes in the commercial photovoltaic (PV) market. 1.The major PV market has shifted from the residential and commercial building markets to central station utility power markets. With this switch has come a new focus on the long-term reliability and durability of PV modules and systems. If you are installing tens or even hundreds of megawatts of PV modules, it is absolutely necessary to ensure that they will continue to perform adequately throughout their expected lifetime of at least 25 years. 2.Selling prices for PV modules have decreased from more than $4 per watt to less than $1 per watt in the last 5 years. This reduction in selling process has been driven by low-cost production in the developing world. This means that most of today's PV modules are being manufactured by companies that did not exist 10 or, in many cases, even 5 years ago. Yet the modules must carry 25-year warranties and are expected to survive at least that long without having the benefit of long-term field experience.

A new biomass fueled electricity generation plant is now under construction in Gainesville, Florida and serves as an excellent subject as it demonstrates the surprising ways the credit ratings agencies influence ecological modernization. Through content analysis, participant observation, and document analysis I will illustrate how credit ratings agencies have influenced the ecological modernization of one of the United States' approximately 2000 municipal electricity utilities.