730 research outputs found
Decreasing the Computing Time of Bayesian Optimization using Generalizable Memory Pruning
Bayesian optimization (BO) suffers from long computing times when processing
highly-dimensional or large data sets. These long computing times are a result
of the Gaussian process surrogate model having a polynomial time complexity
with the number of experiments. Running BO on high-dimensional or massive data
sets becomes intractable due to this time complexity scaling, in turn,
hindering experimentation. Alternative surrogate models have been developed to
reduce the computing utilization of the BO procedure, however, these methods
require mathematical alteration of the inherit surrogate function, pigeonholing
use into only that function. In this paper, we demonstrate a generalizable BO
wrapper of memory pruning and bounded optimization, capable of being used with
any surrogate model and acquisition function. Using this memory pruning
approach, we show a decrease in wall-clock computing times per experiment of BO
from a polynomially increasing pattern to a sawtooth pattern that has a
non-increasing trend without sacrificing convergence performance. Furthermore,
we illustrate the generalizability of the approach across two unique data sets,
two unique surrogate models, and four unique acquisition functions. All model
implementations are run on the MIT Supercloud state-of-the-art computing
hardware.Comment: Accepted as a paper in IEEE HPEC 202
Stress effects on the Raman spectrum of an amorphous material: theory and experiment on a-Si:H
Strain in a material induces shifts in vibrational frequencies, which is a
probe of the nature of the vibrations and interatomic potentials, and can be
used to map local stress/strain distributions via Raman microscopy. This method
is standard for crystalline silicon devices, but due to lack of calibration
relations, it has not been applied to amorphous materials such as hydrogenated
amorphous silicon (a-Si:H), a widely studied material for thin-film
photovoltaic and electronic devices. We calculated the Raman spectrum of a-Si:H
\ab initio under different strains and found peak shifts . This
proportionality to the trace of the strain is the general form for isotropic
amorphous vibrational modes, as we show by symmetry analysis and explicit
computation. We also performed Raman measurements under strain and found a
consistent coefficient of . These results
demonstrate that a reliable calibration for the Raman/strain relation can be
achieved even for the broad peaks of an amorphous material, with similar
accuracy and precision as for crystalline materials.Comment: 12 pages, 3 figures + supplementary 8 pages, 4 figure
Meeting Global Cooling Demand with Photovoltaics during the 21st Century
Space conditioning, and cooling in particular, is a key factor in human
productivity and well-being across the globe. During the 21st century, global
cooling demand is expected to grow significantly due to the increase in wealth
and population in sunny nations across the globe and the advance of global
warming. The same locations that see high demand for cooling are also ideal for
electricity generation via photovoltaics (PV). Despite the apparent synergy
between cooling demand and PV generation, the potential of the cooling sector
to sustain PV generation has not been assessed on a global scale. Here, we
perform a global assessment of increased PV electricity adoption enabled by the
residential cooling sector during the 21st century. Already today, utilizing PV
production for cooling could facilitate an additional installed PV capacity of
approximately 540 GW, more than the global PV capacity of today. Using
established scenarios of population and income growth, as well as accounting
for future global warming, we further project that the global residential
cooling sector could sustain an added PV capacity between 20-200 GW each year
for most of the 21st century, on par with the current global manufacturing
capacity of 100 GW. Furthermore, we find that without storage, PV could
directly power approximately 50% of cooling demand, and that this fraction is
set to increase from 49% to 56% during the 21st century, as cooling demand
grows in locations where PV and cooling have a higher synergy. With this
geographic shift in demand, the potential of distributed storage also grows. We
simulate that with a 1 m water-based latent thermal storage per household,
the fraction of cooling demand met with PV would increase from 55% to 70%
during the century. These results show that the synergy between cooling and PV
is notable and could significantly accelerate the growth of the global PV
industry
Meeting Global Cooling Demand with Photovoltaics during the 21st Century
Space conditioning, and cooling in particular, is a key factor in human
productivity and well-being across the globe. During the 21st century, global
cooling demand is expected to grow significantly due to the increase in wealth
and population in sunny nations across the globe and the advance of global
warming. The same locations that see high demand for cooling are also ideal for
electricity generation via photovoltaics (PV). Despite the apparent synergy
between cooling demand and PV generation, the potential of the cooling sector
to sustain PV generation has not been assessed on a global scale. Here, we
perform a global assessment of increased PV electricity adoption enabled by the
residential cooling sector during the 21st century. Already today, utilizing PV
production for cooling could facilitate an additional installed PV capacity of
approximately 540 GW, more than the global PV capacity of today. Using
established scenarios of population and income growth, as well as accounting
for future global warming, we further project that the global residential
cooling sector could sustain an added PV capacity between 20-200 GW each year
for most of the 21st century, on par with the current global manufacturing
capacity of 100 GW. Furthermore, we find that without storage, PV could
directly power approximately 50% of cooling demand, and that this fraction is
set to increase from 49% to 56% during the 21st century, as cooling demand
grows in locations where PV and cooling have a higher synergy. With this
geographic shift in demand, the potential of distributed storage also grows. We
simulate that with a 1 m water-based latent thermal storage per household,
the fraction of cooling demand met with PV would increase from 55% to 70%
during the century. These results show that the synergy between cooling and PV
is notable and could significantly accelerate the growth of the global PV
industry
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Design of domestic photovoltaics manufacturing systems under global constraints and uncertainty
As global political discourse is taking place where the need for a cleaner energy mix is constantly highlighted, manufacturing strategies are becoming more relevant. Thus, the photovoltaics system design is a crucial aspect related with the overall sustainability. In fact, various countries are considering the potential to locally manufacture different elements of the photovoltaics (PV) value chain and the strategies to incentivize a local manufacturing base. This paper develops a mathematical programming approach for the optimal design of a PV manufacturing value chain considering diverse criteria linked to economic and environmental performance such as minimum sustainable price, transportation capacity, among others, and considering uncertainty. In addition, the proposed methodology involves the dependence over time of supply chain variables and economic parameters such as inflation, electricity cost, and weighted average cost of capital, to determine the manufacturing system topology under uncertain conditions. Our results highlight the importance of planning models to develop markets policies related to supply chains, production level changes and imposed tariffs all while involving uncertainty in economic parameters, which is an improvement compared to planning models that use deterministic formulations. Finally, the proposed methodology and results can encourage decision-making considering probable variations in different parameters
Impurity-to-efficiency simulator: Predictive simulation of solar cell efficiencies based on measured metal distribution and cell processing conditions
We present a fast and simple 1D simulation tool to predict solar cell performance as a function of the initial iron content and distribution in the as-grown silicon wafer, the time-temperature profiles applied during the fabrication process, and several parameters related to cell architecture. The applied model consists of three parts that are validated by comparison to experimental results from literature. Assuming a time-temperature profile of a standard solar cell fabrication process, we calculate the redistribution of iron and the evolution of minority carrier lifetime for different as-grown Fe distributions. The solar cell performance as a function of the total iron concentration and the final lifetime distribution is also simulated and compared to experimental results for multicrystalline Si. Keywords: simulation, crystalline silicon solar cell, getterin
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