Numerical Analysis of Time Required for De-stratification in Warehouses

A significant source of energy consumption comes from maintaining desired indoor environment conditions in warehouses and other industrial facilities. To combat the raising energy costs, studies into more efficient heating and cooling strategies has been a topic of consideration for a number of years. One of the areas of investigation is the implications of a thermally stratified environment. In heating, removing the stratification phenomena has been linked to savings in the cost of fuel to heat an environment. Whereas in cooling a highly stratified environment is desired. The primary method of de-stratification is the utilization of ceiling fans. The use of fans reduces the overall savings of de-stratification for heating purposes. A solution to offset the reliance on grid power is the use of solar powered ceiling fans. The challenge with utilizing solar power during heating seasons is a reduction in the time the sun is available to charge and store energy to run the fans. While there are studies on the impact of thermal stratification, with air as a medium in an indoor environment, there is a lack of information on the frequency at which the ceiling fans need to operate to maintain a de-stratified environment. The determination of a fan operation frequency, to maintain a de-stratified environment, informs potential designers on the viability of installing solar powered fans as an alternative to grid powered fans. In the event that solar powered fans were not a viable option, it also provides information on the frequency that a grid powered fan would need to run to maintain de-stratification. To determine a fan operating frequency, a numerical analysis will be performed. This numerical analysis will assess the time required to de-stratify an environment based on inputs such as flow rate and spatial considerations. In order to establish the quality of the numerical analysis, two experiments have been conducted to observe the impact of de-stratification. One experiment is located at a large retail warehouse distribution center, the other is a small classroom. The data collected from these experiments will be compared to the models developed to predict the change in stratification with time

Investigation of Destratification in Warehouses

A significant source of energy consumption comes from maintaining desired indoor environment conditions in warehouses and other industrial facilities. In efforts to combat the raising energy costs, studies into more efficient heating and cooling strategies has been a topic of consideration for a number of years. One of the areas of investigation is the implications of a thermally stratified environment. In heating, removing the stratification phenomena has been linked to savings in the cost of fuel to heat an environment. Whereas in cooling a highly stratified environment is desired. The primary method of destratification is the utilization of ceiling fans. However, the required parasitic fan power reduces the overall savings of destratification. A solution to offset the reliance on grid power is the use of solar powered ceiling fans. The challenge with utilizing solar power during heating seasons is a reduction in the time the sun is available to charge and store energy to run the fans. While there are studies into the impact of thermal stratification, with air as a medium in an indoor environment, there is a lack of information on the frequency at which the ceiling fans need to operate to maintain a destratified environment. The determination of a fan operation frequency, to maintain a destratified environment, informs potential designers on the viability of installing solar powered fans as an alternative to grid powered fans. In the event that solar powered fans were not a viable option, it also provides information on the frequency that a grid powered fan would need to run to maintain destratification. To determine a fan operating frequency, a numerical analysis was performed. This numerical analysis assessed the time required to maintain a destratified environment based on inputs such as flow rate and spatial considerations. In order to establish the quality of the numerical analysis, two experiments were conducted to observe the impact of destratification. One experiment was located at a large distribution center, the other was a small classroom. The data collected from these experiments was be compared to the models developed to validate the findings. It was found that a destratification fan could maintain a destratified environment by operating at a 35% fan duty cycle

Influence of hole transport material ionization energy on the performance of perovskite solar cells

Halide perovskites have shown excellent photophysical properties for solar cell applications which led to a rapid increase of the device efficiency. Understanding the charge carrier dynamics within the active perovskite absorber and at its interfaces will be key to further progress in their development. Here we present a series of fully evaporated devices employing hole transport materials with different ionization energies. The open circuit voltage of the devices, along with their ideality factors, confirm that the former is mainly determined by the bulk and surface recombination in the perovskite, rather than by the energetic offset between the valence band of the perovskite and the highest occupied molecular orbital of the organic transport layers. These results help to further understand the origin of the open circuit potential in perovskite solar cells, which is an important parameter that needs to be improved to further boost power conversion efficiencies

Efficient Benzodithiophene/Benzothiadiazole-Based n-Channel Charge Transporters

A series of donor–acceptor small molecules based on electrondeficient benzothiadiazole (BTD) and electron-rich benzodithiophene (BDT) featuring an A-D-A structure is presented. Exhaustive spectroscopic, electrochemical, and computational studies evidence their electroactive nature and their ability to form well-ordered thin films with broad visible absorptions and low band gaps (ca. 2 eV). Time-resolved microwave conductivity (TRMC) studies unveil unexpected n-type charge transport displaying high electron mobilities around 0.1 cm2V1 s 1 . Efficient electron transport properties are consistent with the low electron reorganization energies (0.11–0.17 eV) theoretically predicted

Conjugated polyelectrolyte hole transport layer for inverted-type perovskite solar cells

Organic-inorganic hybrid perovskite materials offer the potential for realization of low-cost and flexible next-generation solar cells fabricated by low-temperature solution processing. Although efficiencies of perovskite solar cells have dramatically improved up to 19% within the past 5 years, there is still considerable room for further improvement in device efficiency and stability through development of novel materials and device architectures. Here we demonstrate that inverted-type perovskite solar cells with pH-neutral and low-temperature solution-processable conjugated polyelectrolyte as the hole transport layer (instead of acidic PEDOT:PSS) exhibit a device efficiency of over 12% and improved device stability in air. As an alternative to PEDOT: PSS, this work is the first report on the use of an organic hole transport material that enables the formation of uniform perovskite films with complete surface coverage and the demonstration of efficient, stable perovskite/fullerene planar heterojunction solar cellsopen4