Development and Field Testing of an Inclined Flanged Compact Diffuser for a Micro Wind Turbine

Micro wind turbines installed in various applications, experience average wind speed for most of the time during operations. Power produced by the wind turbine is proportional to the cubic power of the wind velocity and a small increase in wind velocity results increases power output significantly. The approach wind velocity can be increased by covering traditional wind turbine with a diffuser. Researchers are continuously working to develop a compact, lightweight, cost effective and feasible diffuser for wind turbines. The present work carried out to develop a diffuser with these stated objectives. A compact, lightweight inclined flanged diffuser developed for a micro wind turbine. Bare micro wind turbine and wind turbine covered with developed efficient inclined flanged diffuser tested in the field as per International Electrotechnical Commission (IEC) standards and results presented in the form of power curves. The prediction of annual energy production for both wind turbines determined as per IEC standards.

Designing and Installing a Retrofit Heated Green Roof Using Either Co-Gen Waste Hot Water or Municipal Waste Steam Heat as Energy Source

Municipal District Heating Services and Combined Heat and Power (CHP) systems can produce waste heat in the form of steam condensate and hot water. The authors have developed a system to use this thermal pollution to heat the soil and growth medium of green roofs and outdoor gardens. The system enables plant life to survive colder climates and increases growth often in excess of 20% (Power2013-98172). In New York City test heated green roofs, the system can save vast amounts of normally required cooling water that is tapped from the overburdened municipal supply (IMECE2013-65200). Existing small scale green roofs in New York City and larger scale heated green roof retrofit in New York City is presented to indicate additional construction details, thermal considerations, and potential code compliance considerations.

Study of Performance of Attic Air Source Heat Pump in Maine

Heat pumps are a popular heating source in many parts of the United States. They are not widely used in State of Maine due to an assumption that they are marginally useful in cold climates. An attic source heat pump is a variation on a conventional heat pump. In summer, the temperature in the attic is much higher than outside as it absorbs the heat from sunlight. In winter or evening, the attic captures the heat released from the house. Therefore, the attic makes a good candidate for the heat source of a heat pump. For this ongoing study, a laboratory scale heat pump was constructed and experimental tests were performed to establish its operating performance. A temperature controlled testing chamber was built to simulate the attic environment. Attic heat was used to heat up a water tank. COP value was measured for different attic temperatures. Experimental data were favorable to the use of an attic air source heat pump in Maine.

Evaluation of Passive Anti-Fouling Technology Applied to CO2 Heat Pump Water Heaters

Heat pump water heaters are increasing in popularity due to their increased energy efficiency and low environmental impact. This paper describes the experimental testing of a transcritical CO2 heat pump water heater at Queen’s University. A modified 4.5 kW Eco-Cute unit was studied. It sourced heat from a constant temperature water supply and rejected the heat to a 273 litre hot water tank through a gas-cooler. The high temperatures that occur in the gas-cooler of this unit make it ideally suited for natural convection, (i.e., thermosyphon) circulation on the potable water side. This has the potential to reduce pumping power, simplify system operation and design, and increase thermal stratification in the hot water storage tank. This configuration, however, is susceptible to the accumulation of sediments, scale and mineral deposits (i.e., fouling) in geographic regions where high mineral deposits may be present in the water supply. To counteract fouling in these cases, a passive back-flushing system was proposed to prevent the accumulation of deposits on the heat transfer surfaces of the gas-cooler. As hot water is drawn from the system, the cold “mains” supply water is directed through the gas-cooler in the reverse direction of normal operation, scouring the heat transfer surfaces and dissolving deposits of inverse-soluble salts which are a major contributor to fouling on hot heat transfer surfaces. The gas-cooler used was a specially designed unit that, although offering high performance in a compact unit, may be susceptible to the fouling and blockage of the heat transfer passages when used at thermosyphon flow rates. Experiments were conducted to evaluate the effects of the back-flush operation on heat pump performance (i.e., COP) and operation. These were conducted under controlled laboratory conditions, at a range of draw flow rates and temperatures, and are summarized in this paper.

Design and Real Time Simulation of Artificial Intelligent Based MPP Tracker for Photo-Voltaic System

This paper presents an Artificial Intelligent based Maximum Power Point Tracking (MPPT) of a photo-voltaic system implementation using dSPACE 1104. The paper also proposes a novel Adaptive Neuro-Fuzzy Inference System (ANFIS) / Constant Voltage Tracker (CVT) for a photovoltaic (PV) powered multilevel inverter which requires a fixed constant dc voltage at its input. The MPPT algorithms viz. perturb and observe, incremental conductance, neural network, ANFIS and ANFIS/CVT have been designed and implemented on laboratory prototype. The modeling of various MPPT algorithms have been done on MATLAB/SIMULINK platform. Real time simulations have been carried out using dSPACE R&D controller board and CONTROLDESK software. The performance comparisons of various MPPT techniques applied to stand-alone PV system with resistive load have been presented for varying solar radiation conditions. The authors hope that the comparative analysis presented in this work will be helpful for further research.

A Copper Microchannel Heat Exchanger for MEMS-Based Waste Heat Thermal Scavenging

The growing necessity for increased efficiency and sustainability in energy systems such as MEMS devices has driven research in waste heat scavenging. This approach uses thermal energy, which is typically rejected to the surrounding environment, transferred to a secondary device to produce useful power output. This paper investigates a MEMS-based micro-channel heat exchanger (MHE) designed to operate as part of a micro-scale thermal energy scavenging system. Fabrication and operation of the MHE is presented. MHE operation relies on capillary action which drives working fluid from surrounding reservoirs via micro-channels above a heated surface. Energy absorption by the MHE is increased through the use of a working fluid which undergoes phase change as a result of thermal input. In a real-world implementation, the efficiency at which the MHE operates contributes to the thermal efficiency of connected small-scale devices, such as those powered by thermoelectrics which require continual heat transfer. This full system can then more efficiently power MEMS-based sensors or other devices in diverse applications. In this work, the MHE and micro-channels are fabricated entirely of copper with 300μm width channels. Copper electro-deposition onto a copper substrate provides enhanced thermal conductivity when compared to other materials such as silicon or aluminum. The deposition process also increases the surface area of the channels due to porosity. Fabrication with copper produces a robust device, which is not limited to environments where fragility is a concern. The MHE operation has been designed for widespread use in varied environments. The exchanger working fluid is also non-specific, allowing for fluid flexibility for a range of temperatures, depending on the thermal source potential. In these tests, the exchanger shows approximately 8.7 kW/m2 of thermal absorption and 7.6 kW/m2 of thermal transfer for a dry MHE while the wetted MHE had an energy throughput of 8.3 kW/m2. The temperature gradient maintained across the MHE bottom plate and lid is approximately 30 °C for both the dry and wetted MHE tests though overall temperatures were lower for the wetted MHE.

Numerical and Experimental Analysis of a PCM Thermal Storage System

Phase-change materials (PCM) are particularly promising for thermal storage in energy systems where the working fluid is either characterized by small specific heat or small temperature difference. In these cases, sensible heat storage would involve small energy densities (i.e. energy per unit volume). Latent heat storage would allow one to reduce the volume of storage tanks, but also reduce problems related with thermal stratification. On the other hand, heat transfer in PCMs needs to be enhanced in order to complete the charging and discharging processes in reasonable time. This paper reports the numerical and experimental activity performed by the authors related with the design of latent heat storage systems for district heating applications. Among the various enhancement methods, fins present some technical advantages related with manufacturing and management, which make them suitable for the application in district heating systems. The following aspects are considered in this paper: 1) melting and solidification; 2) modeling approaches and validation; 3) thermal enhancement with circular, radial or Y-shaped fins.

Enhancing the Storage Capacity of Supercapacitors Using PVA/CNT Nanocomposite Electrolytes

The ability to achieve high surface areas with nanomaterials brought several advancements in energy storage devices and their applications in different industries. Supercapacitors, a new generation of energy storage devises, have quick charge and discharge abilities, and hold as much energy as batteries and other chemical storage devices. The present study focuses on the effects of carbon nanotubes (CNTs) inclusions in polyvinyl alcohol (PVA) electrolytes for the improved capacitance values, which may affect the lifetime, charge holding, and charging and discharging rates of the graphene nanoflake-based supercapacitors. In this research, various supercapacitors were constructed using the reduced graphene oxide nanoflakes, PVA and PVA incorporated with CNTs, and the best candidates were selected for the future considerations. The test results showed that the CNT concentrations of 0.1–1.0wt% in PVA enhanced the capacitance (charge holding capacity) and reduced the internal resistance of the electrolytes significantly. This study may open up new possibilities for the supercapacitors and other energy storage devices currently under developments.

Development of Conservative Form of RELAP5 Thermal Hydraulic Equations: Part I — Theory

The design and analysis of the thermal/hydraulic systems of nuclear power plants necessitates system codes that can be used in the analysis of steady state and transient conditions. RELAP5 is one of the most commonly used system codes in nuclear organizations. RELAP5 is based on a two-fluid, non-equilibrium, non-homogeneous, hydrodynamic model for the transient simulation of the two-phase system behavior. This model includes six governing equations to describe the mass, energy, and momentum of the two fluids. The “non-conservative” numerical approximation form (which is the current form of RELAP5 code versions) is obtained through the manipulation of selected derivative terms in the equations including the linearization of the product terms in the time derivatives of the equations. For non-conservative technique, the truncation errors introduced in the linearization process can produce mass and energy errors for some classes of transients during time advancements, either resulting in (a) automatic reduction of time steps used in the advancement of the equations and increased run times or (b) the growth of unacceptably large errors in the transient results. To eliminate these difficulties, a new, optional numerical approach has been introduced in RELAP/SCDAPSIM/MOD4.0. This new option uses a more consistent set of the “conservative” numerical approximation to solve non-linearized mass and energy governing equations. The RELAP/SCDAPSIM/MOD4.0 code, being developed as part of the international SCDAP (Severe Core Damage Analysis Package) Development and Training Program (SDTP), is the first version of RELAP5 completely rewritten to FORTRAN 90/95/2000 standards. This paper provides an overview of the original RELAP5 numerical approximations and describes the new theoretical approach. Then the second article introduces the solution strategy of conservative approach and presents some examples of transient problems that have been run using this new approach.