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El A.,ERI | Aly M.M.,Qassim University
International Journal of Renewable Energy Research

In this paper, Quantum dots intermediate band solar cell (QDIBSC) is used to the enhancement of the power conversion efficiency of solar cell. The main advantage of this type is that it preserves large open-circuit voltage with increasing the produced photocurrent in the solar cell. For a best efficiency of one-intermediate band solar cell (one-IBSC), the induced detailed balance efficiency is determined as a function of changing locations of intermediate-band (IB) by using the blackbody. The QDs have the ability to confirm the chosen higher efficiency by assigning the appropriate values of quantum dot width size (QDW) and barrier thickness (BT). It means that the best location of IB in solar cell is realized. The results show that to obtain the maximum power conversion efficiency of QDIBSC, the QDWs and BTs for nanostructured model (Al0.4Ga0.6As/In0.42Ga0.58As) are limited by a surface contour. The highest power efficiencies in this located contour are 45.32% and 62.81% for QDWs = (1.60 nm, 1.64 nm) and BTs = (1.98 nm, 1.94 nm) for 1 sun and maximum light concentrations; respectively. Source

Aly A.E.-M.M.,ERI | Aly A.E.-M.M.,Qassim University
Journal of Renewable and Sustainable Energy

To make the solar cell technology more competitive as a source of alternative energy, the study of how to improve its efficiency is essential. The detailed balance efficiency of traditional and one-intermediate band solar cell (one-IBSC) is analyzed by using realistic spectra at AM0 and AM1.5 under various light concentrations. Theoretically, the optimum location for one-IB is investigated to determine the maximum efficiency of one-IBSC. The quantum dot (QD) intermediate band solar cell is studied with the effect of some parameters for QD such as width size (QDW) and barrier thickness (BT) to determine the optimum location of one-IB. The main results conclude that the one-IBSC under AM0 spectrum has maximum balanced efficiencies reached to 45.70% and 63.56% for 1 Sun and maximum light concentration, respectively. While for AM1.5 spectrum these efficiencies are 49.35% and 67.60% with the same conditions of AM0 spectrum. The results also show that the maximum balanced efficiencies for one-IBSC nearly achieved when they are processed by QDs which have the main parameters, QDW and BT. © 2014 AIP Publishing LLC. Source

Aly A.E.-M.M.,ERI | Aly A.E.-M.M.,Qassim University | Nasr A.,Egypt Atomic Energy Authority | Nasr A.,Qassim University
Journal of Semiconductors

A mathematical model of quantum dot intermediate band solar cells (QDIBSCs) is investigated using two intermediate bands (IBs). These two IBs arise from the quantum dot (QD) semiconductor material within the bandgap energy. Some parameters such as the width of the QD (WQD) and the barrier thickness or the inter-dot distances between the QDs (BT) are studied to show their influence on the performance of the QDIBSC. The time-independent Schrüdinger equation, which is solved using the Kronig-Penney model, is used to determine the position and bandwidth energies of the two IBs. In our proposed model, the cubic shape of the QDs from InAs0.9N0.1 and the barrier or host semiconductor material from GaAs0.98Sb0.02 are utilized. It is shown from the results obtained that changing the parameters WQD and BT has more influence on the bandwidth energy for the first IB, Δ1, than in the case of the second IB, Δ2. The optimum power conversion efficiencies (PCEs) of the QDIBSCs with two IBs for the model under study are 58.01% and 73.55% at 1 sun and maximum solar concentration, respectively. One can observe that, in the case of the two IBs, an improvement of the PCE is achieved. © 2015 Chinese Institute of Electronics. Source

Smyth B.M.,University College Cork | Smyth H.,Bord Gais Eireann | Murphy J.D.,ERI
Biofuels, Bioproducts and Biorefining

Farm incomes in Ireland are in decline and many farmers would operate at a loss in the absence of subsidies. Agriculture is responsible for 27% of Ireland's greenhouse gas emissions and is the largest contributing sector. Penetration of renewable energy in the heat and transport sectors is falling short of targets, and there is no clear plan for achieving them. The anaerobic digestion of grass to produce biogas or biomethane is put forward as a multifaceted solution, which could help meet energy and emissions targets, reduce dependence on imported energy, and provide additional farm income. This paper addresses the economic viability of such a system. Grass biogas/biomethane fares poorly under the current combined heat and power tariff structure, which is geared toward feedstock that attracts a gate fee. Tariff structures similar to those used in other countries are necessary for the industry to develop. Equally, regulation should be implemented to allow injection of biomethane into the gas grid in Ireland. Blends of natural gas and biomethane can be sold, offering a cost-competitive green fuel. Sale as a renewable transport fuel could allow profitability for the farmer and savings for the consumer, but suffers due to the lack of a market. Under current conditions, the most economically viable outlet for grass biomethane is sale as a renewable heating fuel. The key to competitiveness is the existing natural gas infrastructure that enables distribution of grass biomethane, and the renewable energy targets that allow renewable fuels to compete against each other. © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd. Source

Aly A.E.-M.M.,ERI | Aly A.E.-M.M.,Qassim University | Nasr A.,Qassim University | Nasr A.,Egypt Atomic Energy Authority
Journal of Applied Physics

The tremendous amount of research in solar energy is directed toward intermediate band solar cell for its advantages compared with the conventional solar cell. The latter has lower efficiency because the photons have lower energy than the bandgap energy and cannot excite mobile carriers from the valence band to the conduction band. On the other hand, if mini intermediate band is introduced between the valence and conduction bands, then the smaller energy photons can be used to promote charge carriers transfer to the conduction band and thereby the total current increases while maintaining a large open circuit voltage. In this article, the influence of the new band on the power conversion efficiency for structure of quantum dots intermediate band solar cell is theoretically investigated and studied. The time-independent Schrödinger equation is used to determine the optimum width and location of the intermediate band. Accordingly, achievement of a maximum efficiency by changing the width of quantum dots and barrier distances is studied. Theoretical determination of the power conversion efficiency under the two different ranges of QD width is presented. From the obtained results, the maximum power conversion efficiency is about 70.42%. It is carried out for simple cubic quantum dot crystal under fully concentrated light. It is strongly dependent on the width of quantum dots and barrier distances. © 2014 AIP Publishing LLC. Source

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