Back Surface Recombination Velocity Dependent of Absorption Coefficient as Applied to Determine Base Optimum Thickness of an n+/p/p+ Silicon Solar Cell

The monochromatic absorption coefficient of silicon, inducing the light penetration depth into the base of the solar cell, is used to determine the optimum thickness necessary for the production of a large photocurrent. The absorption-generation-diffusion and recombination (bulk and surface) phenomena are taken into account in the excess minority carrier continuity equation. The solution of this equation gives the photocurrent according to absorption and electronic parameters. Then from the obtained short circuit photocurrent expression, excess minority carrier back surface recombination velocity is determined, function of the monochromatic absorption coefficient at a given wavelength. This latter plotted versus base thickness yields the optimum thickness of an n+-p-p+ solar cell, for each wavelength, which is in the range close to the energy band gap of the silicon material. This study provides a tool for improvement solar cell manufacture processes, through the mathematical relationship obtained from the thickness limit according to the absorption coefficient that allows base width optimization.

AC Back Surface Recombination Velocity as Applied to Optimize the Base Thickness under Temperature of an (n+-p-p+) Bifacial Silicon Solar Cell, Back Illuminated by a Light with Long Wavelength

The bifacial silicon solar cell, placed at temperature (T) and illuminated from the back side by monochromatic light in frequency modulation (ω), is studied from the frequency dynamic diffusion equation, relative to the density of excess minority carriers in the base. The expressions of the dynamic recombination velocities of the minority carriers on the rear side of the base Sb1(D(ω, T);H) and Sb2(α, D(ω, T);H), are analyzed as a function of the dynamic diffusion coefficient (D(ω, T)), the absorption coefficient (α(λ)) and the thickness of the base (H). Thus their graphic representation makes it possible to go up, to the base optimum thickness (Hopt(ω, T)), for different temperature values and frequency ranges of modulation of monochromatic light, of strong penetration. The base optimum thickness (Hopt(ω, T)) decreases with temperature, regardless of the frequency range and allows the realization of the solar cell with few material (Si).

The Impact of Optimum Insulation Thickness of External Walls to Energy Saving and Emissions of CO2 and SO2 for Turkey Different Climate Regions

In this study, the optimum insulation thickness of the external walls of the housing and it’s energy saving and environmental impact in the provinces—Ardahan, Aydin, Eskisehir and Samsun—located in four different climate regions of Turkey was calculated for the expanded polystyrene and polyurethane insulation materials. Natural gas and coal were selected as fuels. Ardahan in the coldest climate region and Aydin in the hottest climate region, for the coal and optimum thickness of expanded polystyrene and polyurethane insulation materials, the reduction of CO2 and SO2 emissions. In the study, the relations between annual energy cost saving and insulation thickness are given. The value of energy cost saving increases up to optimum insulation thickness and beyond this level, the energy cost saving is decreased. For coal and optimum thickness of expanded polystyrene and polyurethane insulation materials, the energy cost savings was higher for the cold climate regions when it was compared with the hot climate regions.

Optimum insulation thickness for the sandwich structure livestock buildings external envelopes in different climate regions of China

Determining the optimum insulation thicknesses of external envelopes for livestock buildings are one of the most effective metrics to decrease energy requirements.This study was carried out to determine the optimum insulation thicknesses for livestock buildings in different climate zones,to examine the effects of insulation thickness and material(foam glass,mineral wool,expanded polystyrene,foamed polyurethane,foamed polyvinyl chloride,and expanded polyethylene)on life cycle total cost,life cycle savings,and payback period.The finishing pig houses and laying hen buildings with sandwich wall structures(color steel laminboard)in five typical cities were studied using the degree-days method with economic models.Optimal insulation thicknesses ranged from 0.05 m to 0.25 m and 0.02 m to 0.24 m in finishing pig houses and poultry buildings,respectively;the life cycle total costs ranged from 16.49 to 37.98$/m2 and 13.37 to 36.84$/m2;the life cycle savings ranged from 29.13 to 220.60$/m2 and 0 to 202.13$/m2;and the payback period ranged from 1.11 to 5.81 years and 1.19 to 20.76 years,respectively.Foamed polyurethane provided the highest life cycle savings,while foam glass had the lowest.In this research,the insulation thicknesses for the sandwich structure livestock buildings external envelopes are optimized,and the energy saving can be obtained by using proper insulation thickness in different regions.Furthermore,it can increase the knowledge about energy consumption in the livestock buildings and the results can be also a useful tool for farmers.

Determining the optimum economic insulation thickness of double pipes buried in the soil for district heating systems

The insulation thickness(IT)of double pipes buried in the soil(DPBIS)for district heating(DH)systems was optimized to minimize the annual total cost of DPBIS for DH systems.An optimization model to obtain the optimum insulation thickness(OIT)and minimum annual total cost(MATC)of DPBIS for DH systems was established.The zero point theorem and fsolve function were used to solve the optimization model.Three types of heat sources,four operating strategies,three kinds of insulation materials,seven nominal pipe size(NPS)values,and three buried depth(BD)values were considered in the calculation of the OIT and MATC of DPBIS for DH systems,respectively.The optimization results for the above factors were compared.The results show that the OIT and MATC of DPBIS for DH systems can be obtained by using the optimization model.Sensitivity analysis was conducted to investigate the impact of some economic parameters,i.e.,unit heating cost,insulation material price,interest rate,and insulation material lifetime,on optimization results.It is found out that the impact of sensitivity factors on the OIT and MATC of DPBIS for DH systems is different.

Suppression of multiple ion bunches and generation of monoenergetic ion beams in laser foil-plasma

In one-dimensional particle-in-cell simulations, this paper shows that the formation of multiple ion bunches is disadvantageous to the generation of monoenergetic ion beams and can be suppressed by choosing an optimum target thickness in the radiation pressure acceleration mechanism by a circularly polarised laser pulse. As the laser pulse becomes intense, the optimum target thickness obtained by a non-relativistic treatment is no longer adequate. Considering the relativistic Doppler-shifted pressure, it proposes a relativistic formulation to determine the optimum target thickness. The theoretical predictions agree with the simulation results well. The model is also valid for two-dimensional cases. The accelerated ion beams can be compelled to be more stable by choosing the optimum target thickness when they exhibit some unstable behaviours.

Energy and Emission Reduction Potential for Bank ATM Units in India

With the growing economy of India, banking sector growth has led to installation of thousands of Automatic Teller Machines (ATMs) throughout the country. ATMs provide 24 × 7 services as well as operate at low-temperature ranges of cooling, hence have high operating energy costs. Insulating an ATM’s envelope is not a prevalent technique in India. In the present study, an effort has been made to determine the optimum insulation thickness for three different insulation materials for the typical ATM envelope in four different climatic zones of India. Life cycle savings and payback periods for various insulation materials are also evaluated. Further, these optimally insulated ATM envelopes can be integrated with grid connected rooftop solar PV systems. The energy saving and emissions reduction potential due to these two interventions have been estimated on the national basis. Altogether in the four selected climate zones, energy saving of 17% - 30% provides the annual economic benefit of Indian National Rupees (Rs.) 3570 million with annual carbon reduction potential of about 0.60 million tCO2. From this study, it is observed that properly insulated ATMs integrated with rooftop solar PV systems, can significantly reduce the energy costs as well as carbon emissions in India’s context.

Optimizing environmental insulation thickness of buildings with CHP-based district heating system based on amount of energy and energy grade

The increase of insulation thickness(IT)results in the decrease of the heat demand and heat medium temperature.A mathematical model on the optimum environmental insulation thickness(OEIT)for minimizing the annual total environmental impact was established based on the amount of energy and energy grade reduction.Besides,a case study was conducted based on a residential community with a combined heat and power(CHP)-based district heating system(DHS)in Tianjin,China.Moreover,the effect of IT on heat demand,heat medium temperature,exhaust heat,extracted heat,coal consumption,carbon dioxide(CO_(2))emissions and sulfur dioxide(SO_(2))emissions as well as the effect of three types of insulation materials(i.e.,expanded polystyrene,rock wool and glass wool)on the OEIT and minimum annual total environmental impact were studied.The results reveal that the optimization model can be used to determine the OEIT.When the OEIT of expanded polystyrene,rock wool and glass wool is used,the annual total environmental impact can be reduced by 84.563%,83.211%,and 86.104%,respectively.It can be found that glass wool is more beneficial to the environment compared with expanded polystyrene and rock wool.