493 research outputs found
Solar Engineering Magazine
No full textMonthly magazine discussing various topics related to research, development, and deployment of solar energy technologies, as well as applications and marketing for the industry
Solar Engineering Magazine
No full textMonthly magazine discussing various topics related to research, development, and deployment of solar energy technologies, as well as applications and marketing for the industry
Solar Engineering Magazine
No full textMonthly magazine discussing various topics related to research, development, and deployment of solar energy technologies, as well as applications and marketing for the industry
Designing photovolaic/thermal solar collectors for building integration
No full textWith concern growing over the environment and resource use, there has been greater emphasis placed on sustainability, particularly in the built environment. One of the key points of sustainable urban environments is the need for an increase in the densification of the population. A by-product of increased densification however, is a reduction in the area per person that can be used for on-site renewable energy generation from the solar resource. Where previously it would have been possible to have a photovoltaic array and solar water heater side-by-side for a free-standing household, this may not be achievable in a high-density living situation.
As a counterpoint to this issue, the design of a novel combined photovoltaic/thermal for building integration (BIPVT) solar collector is analysed and discussed. The panel has a higher efficiency per unit area, than an array of photovoltaic panels in combination with solar thermal panels. In addition, by integrating electricity generation, water heating and facade elements it is possible to reduce the complexity associated with traditional solar installations while also achieving an architecturally sensitive appearance. As such the BIPVT is ideally suited to environments where facade space with suitable solar access is limited, or where large numbers of people share a single building.
In this study, the influence of key design parameters on the performance of a BIPVT collector are presented and discussed. Finally, a transient systems analysis is used to illustrate the performance benefits of BIPVT style collectors over traditional technologies
Investigation of renewable, coupled solar-hydrogen fuel generation with thermal management systems suitable for equatorial regions
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Solar Energy and Hydrogen (energy carrier) are possible replacement options for fossil fuel and its associated problems of availability and high prices which are devastating small, developing, oil-importing economies. But a major drawback to the full implementation of solar energy, in particular photovoltaic (PV), is the lowering of conversion efficiency of PV cells due to elevated cell temperatures while in operation. Also, hydrogen as an energy carrier must be produced in gaseous or liquid form before it can be used as fuel; but its‟ present major conversion process produces an abundance of carbon dioxide which is harming the environment through global warming. In search of resolutions to these issues, this research investigated the application of Thermal Management to Photovoltaic (PV) modules in an attempt to reverse the effects of elevated cell temperature. The investigation also examined the effects of coupling the thermally managed PV modules to a proton exchange membrane (PEM) Hydrogen Generator for the production of hydrogen gas in an environmentally friendly and renewable way. The research took place in Kingston, Jamaica.
The thermal management involved the application of two cooling systems which are Gravity-Fed Cooling (GFC) and Solar-Powered Adsorption Cooling (SPAC) systems. In both systems Mathematical Models were developed as predictive tools for critical aspects of the systems. The models were validated by the results of experiments. The results of the investigation showed that both cooling systems stopped the cells temperatures from rising, reversed the negative effects on conversion efficiency, and increased the power output of the module by as much as 39%. The results also showed that the thermally managed PV module when coupled to the hydrogen generator impacted positively with an appreciably increase of up to 32% in hydrogen gas production.
The results of this work can be applied to the equatorial belt but also to other regions with suitable solar irradiation. The research has contributed to the wider community by the development of practical, environmentally friendly, cost effective Thermal Management Systems that guarantee improvement in photovoltaic power output, by introducing a novel way to use renewable energy that has potential to be used by individual household and/or as cottage industry, and by the development of Mathematical Tools to aid in photovoltaic power systems designs
Development of a solar assisted heat pump desalination system
No full textSolar Energy: Research, Technology and Applications427-45
Multi-Scale Modelling of a Solar Reactor for the High-Temperature Step of a Sulphur-Iodine-Based Water Splitting Cycle
No full textThe 3-step sulphur-iodine-based thermochemical cycle for splitting water is considered. The high temperature step of the closed-material cycle consists of evaporation, decomposition, and reduction of sulphuric acid to SO2 using concentrated solar process heat. This step is followed by the Bunsen reaction and HI decomposition. The solar reactor concepts proposed are based on a shell-and-tube heat exchanger filled with catalytic packed beds and on a porous ceramic foam to directly absorb solar radiation and act as reaction site. The design, modelling and optimisation of the solar reactor using complex porous structures relies on the accurate determination of their effective heat and mass transport properties. Accordingly, a multi-scale approach is applied. Ceramic foam samples are imaged using high-resolution X-ray tomography to obtain their exact 3D geometrical configuration, which in turn is used in direct pore-level simulations for the determination of the morphological and effective transport properties. These are incorporated in a volume-averaged (continuum) model of the solar reactor. Model validation is accomplished by comparing numerically simulated and experimentally measured temperatures in a 1 kW reactor prototype tested in a solar furnace. The model is further applied to analyze the influence of foam properties, reactor geometry, and operational conditions on the reactor performance
Novel pole-sitter mission concepts for continuous polar remote sensing
No full textThe pole-sitter concept is a solution to the poor temporal resolution of polar observations from highly inclined, low Earth orbits and the poor high latitude coverage from geostationary orbit. It considers a spacecraft that is continuously above either the North or South Pole and, as such, can provide real-time, continuous and hemispheric coverage of the polar regions. Despite the significant distance from the Earth, the utility of this platform for Earth observation and telecommunications is clear, and applications include polar weather forecasting and atmospheric science, glaciology and ice pack monitoring, ultraviolet imaging for aurora studies, continuous telecommunication links with polar regions, arctic ship routing and support for future high latitude oil and gas exploration. The paper presents a full mission design, including launch (Ariane 5 and Soyuz vehicles), for two propulsion options (a near-term solar electric propulsion (SEP) system and a more advanced combination of a solar sail with an SEP system). An optional transfer from the North Pole to South Pole and vice-versa allows viewing of both poles in summer. The paper furthermore focuses on payloads that could be used in such a mission concept. In particular, by using instruments designed for past deep space missions (DSCOVR), it is estimated that resolutions up to about 20 km/pixel in the visible wavelengths can be obtained. The mass of these instruments is well within the capabilities of the pole-sitter design, allowing an SEP-only mission lifetime of about 4 years, while the SEP/sail propulsion technology enables missions of up to 7 years
Passive solar-energy air-heating wall panels
No full textThe development of products which enable passive solar-energy
air-heating to be integrated into the heating strategies of public,
commercial and industrial buildings is described. These buildings
are, in general, only occupied significantly during the day;
consequently the bulk of heating demand coincides with the period of
solar gain. In these circumstances collected solar heat should be
delivered with the minimum of delay.
The design and operation of units which are capable of supplying solar
heated air in this manner is outlined. These are passive, naturalcirculation
air-heating collectors, also known as natural-convection
air-heaters, or thermosyphoning air panels.
Four methods of retrofitting such solar collectors to non-domestic
buildings have been identified, one of which, the overcladding
collector, has not been proposed previously. Problems associated with
the successful installation and operation of these units have also
been considered.
The relative merits of a number of methods of testing passive solarenergy
air-heating collectors have been investigated. A method of
determining instantaneous collector efficiency based on the
measurement of glazing temperature, inlet and outlet air temperature,
ambient temperature and insolation has been developed.
Three novel design proposals have been presented: i) a collector
constructed with the insulation fitted outside, rather than inside, so
that the metal body of the collector may provide more symmetrical
heating of the air flow than the conventional arrangement, ii) an
absorber which consisted of parallel ducts to increase the rate of
heat transfer to the air, heating it symmetrically, (iii) a hinged
air-deflector for conversion from the heating to the ventilation mode
Static highly elliptical orbits using hybrid low-thrust propulsion
No full textThe use of extended static-highly elliptical orbits, termed Taranis orbits, is considered for continuous observation of high latitude regions. Low-thrust propulsion is used to alter the critical inclination of Molniya-like orbits to any inclination required to optimally fulfill the mission objectives. This paper investigates a constellation of spacecraft at 90deg inclination for observation of latitudes beyond 55deg and 50deg, considering: spatial resolution, radiation environment, number of spacecraft and End of Life debris mitigation measures. A constellation of four spacecraft on a 16-hr Taranis orbit is identified to enable continuous observation 55deg latitude. Neglecting constraints to minimize the radiation allows the number of spacecraft in the constellation to be reduced to three on a 12-hr orbit. Similarly to view continuously to 50deg, seven spacecraft on a 16-hr orbit are required; this is reduced to five neglecting radiation constraints. It is anticipated that it is significantly more cost effective to reduce the number of required launches and employ radiation hardened components. Thus, a constellation of three or five spacecraft on the 12-hr Taranis orbit is considered the most beneficial when observing to latitudes of 55deg and 50deg respectively. Hybrid solar sail / Solar Electric Propulsion systems are considered to enable the Taranis orbits, where the acceleration required is made up partly by the acceleration produced by the solar sail and the remainder supplied by the electric thruster. Order of magnitude mission lifetimes are determined, a strawman mass budget is also developed for two system constraints, firstly spacecraft launch mass is fixed, and secondly the maximum thrust of the thruster is constrained. Fixing mass results in negligible increases in mission lifetimes for all hybrid cases considered, solar sails also require significant technology development. Fixing maximum thrust of the electric thruster increases mission lifetime and solar sails are considered near to mid-term technologies. This distinction highlights an important contribution to the field, illustrating that the addition of a solar sail to an electric propulsion craft can have negligible benefit when mass is the primary system constraint. Technology requirements are also outlined, including sizing of solar arrays, electric thruters, propellant tanks and solar sails
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