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An organic Schottky barrier cell, consisting of a thin layer of the organic semiconductor, GaPc-Cl, in contact with gold on one side and an electrolyte containing a redox couple on the other, was developed as a solar energy conversion device. Schottky barriers were formed at both interfaces. Film morphology, as determined by the sublimation rate, was the major determinant of the photoelectrochemical behavior. An optimum film consisted of a single layer of crystallites about 1.0 micron in thickness, tightly packed together to give a non-porous film. Thinner films did not develop the full theoretical photopotential, and pores acted as recombination sites, decreasing the efficiency. Both negative and positive photopotentials could be developed, depending on the redox couple used. The photopotential, was found to be proportional to the differences between the Fermi level of the Au and the formal potential of the redox couple. Hydrogen evolution was possible with up to 0.1% solar efficiency on a platinized version of the optimum electrode. Results from photocurrent action spectra and pulsed laser photocoulostatics, showed the potential drop across the film was not linear, but formed a potential well about 0.1 eV deep, which captured charge carriers and decreased the efficiency. From scanning electron microscope studies, phthalocyanines, such as AlPc-Cl, GaPc-Cl, and InPc-Cl, with bulky anions were found to form block-like crystal structures favorable for use in Schottky barrier cells. Phthalocyanines with transition metals in the +2 oxidation state, such as FePc and MgPc, were found to form long needles, which were not favorable for use in Schottky barrier cells.

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Air-conditioning systems driven by solar energy have can save primary energy and reduce peak power consumption, which is particularly important for utility providers in the summer months. Additionally solar cooling is a promising application of solar thermal technology since the cooling load is well correlated to the overall solar availability. Liquid desiccant air-conditioning, which uses a salt solution to dehumidify air, can be used in a thermally driven air-conditioning system and offers many benefits for solar applications including the ability to store solar energy in the form of concentrated liquid desiccant. The current work focuses on the Queen’s University Solar Liquid Desiccant Cooling Demonstration Project. In previous work, a pre-commercial Liquid Desiccant Air Conditioner (LDAC) was installed and experimentally characterized using a gas-fired boiler to provide heat. As part of the current study a 95m2 solar array was added as a heat source. The Solar LDAC was tested for 20 days in the summer of 2012 to evaluate performance. The solar LDAC was found to provide between 9.2kW and 17.2kW of cooling power with an overall thermal Coefficient of Performance (COP) of 0.40 and electrical COP of 2.43. The collector efficiency was 53%, and 40% of the required thermal energy was provided by the solar array. A model was developed in TRNSYS to predict the performance of the solar LDAC and simulation results were compared to the experimental results with reasonable accuracy. The validated model was then used to simulate the annual performance of the solar LDAC in Toronto, Ontario; Vancouver, British Columbia; and Miami, Florida. The highest performance was achieved in Miami, where an overall thermal COP of 0.48 was predicted. It is proposed that additional improvements be made to the system by replacing inefficient pumps and fans, adding desiccant storage, and improving the control scheme. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2012-10-29 16:34:02.906

PV/Thermal technology is the combination of solar thermal and photovoltaics - two mature and widely understood technologies. Combining the two technologies complicates existing standardized rating procedures and performance modeling methods. Currently a standardized performance test method does not exist for PV/Thermal (PV/T) panels. Existing and developing PV/T panels are commonly tested using separate standardized solar thermal and photovoltaic test procedures. Solar thermal performance is rated in terms of temperature difference whereas photovoltaic performance is dependent on absolute temperature level. The thermal and electrical performance of a PV/T panel is, however, coupled so performance equations derived using traditional test methods may not accurately reflect the performance of a combined PV/T panel over a wide range of conditions. The purpose of this work was to develop an efficiency equation for a PV/T panel which can be derived from a minimal amount of empirical test data and still accurately predict its thermal and electrical performance over a wide range of conditions. To accomplish this, a quasi- 3-dimensional steady-state model of a sheet-and-tube PV/T collector was developed and used to generate a broad data set from which a simplified PV/T performance equation was developed. Using this numerically generated data set, and introducing additional coefficients into the traditional solar thermal performance characteristic, a modified PV/T efficiency equation was derived which expressed the electrical and thermal efficiency in terms of ambient temperature, incident solar irradiation and the temperature difference between the inlet fluid and the ambient. It was also shown, for the case studied, that the efficiency equation can be produced from as few as 6 data points and still accurately predicts the performance at a wide range of operating conditions. A TRNSYS [1] model was developed to demonstrate how the performance equation can be used to simulate the annual performance of a PV/T collector in a domestic hot water system. It was shown that a performance equation, derived from 6 data points, performed as well as a performance map which used over 1000 data points. The annual thermal and electrical production predicted by both models was within 1.5% of each other. The PV/T efficiency equations were also shown to perform well for a range of electrical parameters, thermal properties and substrate thermal conductivity values. Future work is recommended to validate the PV/T performance equation using real empirically derived data for a range of collector designs. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2013-01-22 15:40:03.337

This investigation forms part of an attempt to provide an alternative to conventional power generation technologies that use fossil fuels which have impact on global warming. The field of this investigation covers the development of a latent heat thermal storage system which has a potential of conserving available solar energy. The advantages of using thermal energy storage that have been found previously include reduced energy cost, energy consumption, equipment size and pollutant emissions, also increased flexibility of operation, efficiency and effectiveness of equipment utilization. Traditionally, available heat has been stored in the form of sensible heat (typically by raising the temperature of the energy storage medium) for later use. Latent heat storage on the other hand, is a young and developing technology which has found considerable interest in recent times due to its advantages over sensible heat storage which include smaller temperature swing, smaller size and lower weight per unit of storage capacity. It has been demonstrated that, for the development of a latent heat thermal energy storage system, the choice of the phase change material (PCM) as well as the heat transfer mechanism in the PCM play important roles. In this study, a suitable phase change material and an appropriate heat transfer enhancement technique are identified for utilization in a proposed latent heat thermal energy storage system. Also included, is the design of the proposed heat storage system. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

The purpose of this thesis is to consider PhotoVoltaic Power Converter (PVPC) technology, developed by Atira Technologiesʼ, and its prospects for military and space applications. This research will validate the hypothesis that PVPC technology enables a solar power system to produce usable power during low- and no-light conditions which standard solar power systems fail to provide. Solar cell panels are exposed to sunlight at different angles and with variable intensity, therefore the resulting output power varies depending on the illumination angle as well as the light intensity of each panel. Atira Technologiesʼ devised a novel buck-boost converter that is specifically designed to track the maximum power point of each solar panel. This would provide a significant increase in the overall available power by utilizing a switching topology in a subdued lighting condition. Although a small amount of power is generated, given enough time, a battery will reach its full charge, compared to no additional charging if the battery is using a panel without the circuit. In addition, this research will also show the vital sustaining information to substantiate PVPC's claim of usefulness and effectiveness to allow for longer time on station both in the field and in space so it can extend its missions.

This paper presents a segmented parabolic concentrator employing holographic spectral filters that provide focusing and spectral bandwidth separation capability to the system. Strips of low band gap silicon photovoltaic (PV) cells are formed into a parabolic surface as shown by Holman et. al. [1]. The surface of the PV segments is covered with holographic elements formed in dichromated gelatin. The holographic elements are designed to transmit longer wavelengths to silicon cells, and to reflect short wavelength light towards a secondary collector where high-bandgap PV cells are mounted. The system can be optimized for different combinations of diffuse and direct solar illumination conditions for particular geographical locations by controlling the concentration ratio and filtering properties of the holographic elements. In addition, the reflectivity of the back contact of the silicon cells is used to increase the optical path length and light trapping. This potentially allows the use of thin film silicon for the low bandgap PV cell material. The optical design combines the focusing properties of the parabolic concentrator and the holographic element to control the concentration ratio and uniformity of the spectral distribution at the high bandgap cell location. The presentation concludes with a comparison of different spectrum splitting holographic filter materials for this application.

Spectrum splitting is an approach to increasing the conversion efficiency of a photovoltaic (PV) system. Several methods can be used to perform this function which requires efficient spatial separation of different spectral bands of the incident solar radiation. In this paper several of holographic methods for implementing spectrum splitting are reviewed along with the benefits and disadvantages associated with each approach. The review indicates that a volume holographic lens has many advantages for spectrum splitting in terms of both power conversion efficiency and energy yield. A specific design for a volume holographic spectrum splitting lens is discussed for use with high bandgap InGaP and low bandgap silicon PV cells. The holographic lenses are modeled using rigorous coupled wave analysis, and the optical efficiency is evaluated using non-sequential raytracing. A proof-of-concept off-axis holographic lens is also recorded in dichromated gelatin film and the spectral diffraction efficiency of the hologram is measured with multiple laser sources across the diffracted spectral band. The experimental volume holographic lens (VHL) characteristics are compared to an ideal spectrum splitting filter in terms of power conversion efficiency and energy yield in environments with high direct normal incidence (DNI) illumination and high levels of diffuse illumination. The results show that the experimental VHL can achieve 62.5% of the ideal filter power conversion efficiency, 64.8% of the ideal filter DNI environment energy yield, and 57.7% of the ideal diffuse environment energy yield performance.

Thesis advisor: Dunwei Wang / Due to the increasing energy demand from human activities, efficient utilization of renewable energy, such as wind, solar and geothermal energies, becomes necessary and urgent. Photoelectrochemical water splitting offers a great example to convert solar energy and storage it in the term of chemical bond. Seeking suitable photoanode materials becomes the research focus of my study, because the development of photoanode materials significantly lags that of robust photocathode (such as Si). The main challenge is to fabricate an efficient and stable photoanode material which can deliver high photocurrent and sufficient photovoltage which can match well with those of photocathode when made into tandem cell configuration. Hematite (α-Fe2O3) represents a promising metal oxide photoanode material, with a suitable band gap (2.1 eV), low cost and toxicity. Applying nanostructures and appropriate surface modification layers help address existing research challenges. As a result, a much lower turn on potential and greater photocurrent density is achieved. Another photoanode material attracts our attention is tantalum nitride (Ta3N5), with a similar band gap to hematite but much better light absorption properties, shows a poor stability in aqueous electrolyte. For both photoanode materials, thermodynamic and kinetic aspects are studied in details when tested in water splitting devices. These works provide new ideas and insights on the future studies. / Thesis (PhD) — Boston College, 2015. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.