Enhancing Energy Use Research Articles

SU‐E‐T‐886: Exploration of SBRT Lung Treatment Using the First Non‐Commercial VMAT

Purpose: The beamlet‐based IMRT‐SBRT has two widely‐recognized deficiencies: an elevated MU and a reduced MU‐to‐cGy coefficient. To address these issues, we developed our own version of VMAT. A thorough literature search indicates that this is the first non‐commercial VMAT in the United States. Our objectives are 1) to minimize MU; 2) to maximize delivery efficiency and 3) to provide IMRT‐SBRT‐comparable plans. Methods: All VMAT‐SBRT plans consisted of a single arc of 180 equally spaced beams. Our VMAT was designed to simultaneously optimize both MLC apertures and aperture MU weights. A novel feature of our VMAT planning system was the inclusion of a normal tissue objective (NTO) function into the total dose‐volume based quadratic objective function. Five VMAT‐SBRT plans were computed and compared with corresponding IMRT‐SBRT plans. Our VMAT‐SBRT plans were delivered in RapidArc mode on a RapidArc‐enabled Varian Trilogy machine. Results: We found that the mean MU for the VMAT‐SBRT plans was 2052±108, while that for the IMRT‐SBRT plans was 3790±63. The MU‐to‐cGy ratio was 1.15±0.06 for the VMAT‐SBRT plans, while the MU‐to‐cGy ratio was 2.11±0.04 for the IMRT‐SBRT plans. The mean delivery time for the IMRT‐SBRT plans was 6.32±1.06 min (600 MU/min), while that for the VMAT‐SBRT plans was only 1.25 min. The mean target dose homogeneity index HI for the IMRT‐SBRT plans was 0.0535±0.0001, while that for the VMAT‐SBRT plans was 0.0366±0.0028. The mean PTV dose conformity PIPTV for the VMAT‐SBRT plans was 1.421±0.0311, while that for the IMRT‐SBRT plans was 1.466 ±0.0028. Conclusions: Based on our preliminary results, we conclude that our own version of VMAT‐SBRT can significantly increase plan delivery efficiency, enhance energy use efficiency, and improve target dose homogeneity and conformity. It is a viable and safe substitute for IMRT‐SBRT.

Ambient temperature and pregnancy influence cortisol levels in female guinea pigs and entail long-term effects on the stress response of their offspring

Mammals generally respond to the important metabolic requirements imposed by thermoregulation and pregnancy by increasing plasma concentrations of glucocorticoid that promote the mobilization of body reserves and enhance energy use by tissues. This study examined the impact of distinct ambient temperatures and reproductive status on cortisol plasma levels in female guinea pigs ( Cavia aperea f. porcellus). We also examined cortisol profiles of their offspring. Forty adult females were placed in individual boxes, 20 were exposed to a neutral thermal regime (mean ambient temperature 22.1 ± 1.5 °C) and 20 were maintained under a cool thermal regime (15.1 ± 1.5 °C). Within each treatment, 12 females were pregnant and 8 were non-pregnant. Pregnancy generated a marked elevation of baseline cortisol. Ambient temperature also affected cortisol concentrations. Compared to the pregnant females from the neutral thermal regime, pregnant females maintained under cool conditions exhibited lower baseline levels of cortisol, were less active, but they displayed a greater stress response (i.e. rapid increase of plasma cortisol) following handling. Thermal treatment did not influence reproductive output, reproductive effort, or offspring characteristics. This suggests that pregnant female guinea pigs cope with cool (but not extreme) thermal conditions by reducing activity and baseline cortisol levels, possibly to save energy via an adaptive response. Interestingly, the greater amplitude of the stress response of the cool regime females was also observed in their offspring 2 months after parturition, suggesting that hormonal ambience experienced by the individuals in utero shaped their stress response long after birth.

Effects of input management and crop diversity on non-renewable energy use efficiency of cropping systems in the Canadian Prairie

Although producers’ prime objective may be to increase net returns, many are also interested in conserving and enhancing the quality the soil, water and air resources through adopting more environmentally friendly production practices. This study compared non-renewable energy inputs, energy output, and energy use efficiency of nine dryland cropping systems comprised of a factorial combination of three methods of input management [high (HIGH), i.e., conventional tillage plus full recommended rates of fertilizer and pesticides; reduced (RED), i.e., conservation tillage plus reduced rates of fertilizer and pesticides; and organic (ORG), i.e., conventional tillage plus N-fixing legumes and non-chemical means of weed and pest control]; and three crop rotation systems with varying levels of cropping diversity [a fallow-based rotation with low crop diversity (LOW); a diversified rotation using annual cereal, oilseed and pulse grains (DAG); and a diversified rotation using annual grains and perennial forages (DAP)]. The study was conducted over the 1996–2007 period on a Dark Brown Chernozemic soil (Typic Boroll) in the Canadian Prairies. As expected, total direct plus indirect energy input was the highest for the HIGH and RED input treatments (3773 MJ ha −1 year −1), and 50% less for ORG management. Most of the energy savings came from the non-use of inorganic fertilizers and pesticides in the ORG management treatments. Further, total energy use was the highest for the DAG treatments (3572 MJ ha −1 year −1), and similar but about 18% lower for the DAP and LOW crop diversity treatments compared to DAG. Thus, overall, the HIGH/DAG and RED/DAG systems had the highest energy requirements (4409 MJ ha −1 year −1) and ORG/DAP had the lowest (1806 MJ ha −1 year −1). Energy output (calorimetric energy content) was typically the highest for the HIGH input treatments (26,541 MJ ha −1 year −1), was about 4% less with RED, and 37% less with ORG management. The latter reflected the lower crop yields obtained with organic management. Similarly, energy output was the highest for the DAP treatments (25,008 MJ ha −1 year −1), about 5% less for DAG, and 20% less for the LOW crop diversity treatments. The higher energy output with the DAP treatments largely reflected that the entire harvested biomass of the forage crops was included in energy output, while for grain crops only the seed was included. The straw and crop residues from annual crops were returned to the land to protect the soil from erosion and to maintain soil organic matter as this is the recommended practice in this semi-arid region. In contrast to energy output and to net energy produced, energy use efficiency (measured as yield of grain plus forage produced per unit of energy input or as energy output/energy input ratio) was the highest for the ORG input treatments (497 kg of harvested production GJ −1 of energy input, and an energy output/energy input ratio of 8.8). We obtained lower, but generally similar energy use efficiency for the HIGH and RED input treatments (392 kg GJ −1 and ratio of 7.1). Thus, overall, ORG/DAP was the most energy efficient cropping system, while RED/LOW and RED/DAG generally ranked the lowest in energy use efficiency. Our findings support the current movement of producers toward ORG management as a means of reducing the reliance on non-renewable energy inputs and improving overall energy use efficiency of their cropping systems. Our results also suggest that moving away from traditional monoculture cereal rotations that employ frequent summer fallowing, toward extended and diversified crop rotations that use reduced tillage methods, although resulting in an increase in energy output, will not significantly reduce the overall reliance on non-renewable energy inputs, nor enhance energy use efficiency, unless perennial legume forages and/or legume grain crops are included in the cropping mix.

Conceptual design and simulation analysis of thermal behaviors of TGR blast furnace and oxygen blast furnace

Extensive use of carbon based fuel is the main inducement for global warming and more extreme weather. Reducing carbon dioxide emission and enhancing energy use is a common subject in steel industry. In the integrated steel plant, decreasing carbon dioxide emission must consider energy balance in the whole iron and steel works, and secondary energy must be actively utilized. As promising blast-furnaces, top gas recovery blast furnace (TGR-BF) and oxygen blast furnace have been investigated. In this paper, conceptual TGR blast furnace and oxygen blast furnace are proposed. Base on the idea of blast furnace gas de-CO2 circulating as reducing agent and the idea of pure oxygen blast decreasing the thermal reserve zone temperature, process modeling is conducted with ASPEN Plus. It is shown that the developed model reasonably describes the energy balance and mass balance feature of the furnace, and provides basic thermodynamic condition for furnaces. The effects of changes in different operation conditions are studied by sensitivity analysis and reference data from simulation.