262,949 research outputs found
Gossamer roadmap technology reference study for a solar polar mission
No full textA technology reference study for a solar polar mission is presented. The study uses novel analytical methods to quantify the mission design space including the required sail performance to achieve a given solar polar observation angle within a given timeframe and thus to derive mass allocations for the remaining spacecraft sub-systems, that is excluding the solar sail sub-system. A parametric, bottom-up, system mass budget analysis is then used to establish the required sail technology to deliver a range of science payloads, and to establish where such payloads can be delivered to within a given timeframe. It is found that a solar polar mission requires a solar sail of side-length 100 – 125 m to deliver a ‘sufficient value’ minimum science payload, and that a 2. 5μm sail film substrate is typically required, however the design is much less sensitive to the boom specific mass
Can PV or solar thermal systems be cost effective ways of reducing CO 2 emissions for residential buildings?
No full textThis paper compares two solar systems, an actual building integrated, photovoltaic roof (BIPV) and a notional solar thermal system for a residential block in London, UK. The carbon payback for the solar thermal system is 2 years, the BIPV system has a carbon payback of 6 years. Simple economic payback times for both systems are more than 50 years. Calculations considering the current UK energy price increase (10%/yr), reduce the economic payback time for the PV roof to under 30 years.The costs to reduce overall carbon dioxide emissions using a BIPV roof are £196/tonne CO2, solar thermal individual systems at £65/tonne CO2 and community solar thermal at £38/tonne CO2. The current spot market price for CO2 is £15/tonne CO2 (20). Capital costs for PV systems in particular must be significantly reduced for them to be a cost-effective way to reduce CO2. This paper compares two solar systems, an actual building integrated, photovoltaic roof (BIPV) and a notional solar thermal system for a residential block in London, UK. The carbon payback for the solar thermal system is 2 years, the BIPV system has a carbon payback of 6 years. Simple economic payback times for both systems are more than 50 years. Calculations considering the current UK energy price increase (10%/yr), reduce the economic payback time for the PV roof to under 30 years.The costs to reduce overall carbon dioxide emissions using a BIPV roof are £196/tonne CO2, solar thermal individual systems at £65/tonne CO2 and community solar thermal at £38/tonne CO2. The current spot market price for CO2 is £15/tonne CO2 (20). Capital costs for PV systems in particular must be significantly reduced for them to be a cost-effective way to reduce CO2
Implementation of a new bi-directional solar modelling method for complex facades within the ESP-r building simulation program
No full textThis paper provides an overview of a new method for modelling the total solar energy transmittance. It is implemented in the ESP-r building simulation program to model complex façades such as double glazed façades with external, internal or integrated shading devices. This new model has been validated and tested for several cases. The new model required changes to the solar control simulation algorithm and the user interface, so a new “Advanced optics menu” was also introduced into ESP-r. The paper presents the interface development and application of the new technique to different simulation configurations (especially different complex façades with shading devices) in a standard office building
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
Performance of a building integrated photovoltaic/thermal (BIPVT) solar collector
No full textThe idea of combining photovoltaic and solar thermal collectors (PVT collectors) to provide electrical and heat energy is an area that has, until recently, received only limited attention. Although PVTs are not as prevalent as solar thermal systems, the integration of photovoltaic and solar thermal collectors into the walls or roofing structure of a building could provide greater opportunity for the use of renewable solar energy technologies. In this study, the design of a novel building integrated photovoltaic/thermal (BIPVT) solar collector was theoretically analysed through the use of a modified Hottel–Whillier model and was validated with experimental data from testing on a prototype BIPVT collector.
The results showed that key design parameters such as the fin efficiency, the thermal conductivity between the PV cells and their supporting structure, and the lamination method had a significant influence on both the electrical and thermal efficiency of the BIPVT. Furthermore, it was shown that the BIPVT could be made of lower cost materials, such as pre-coated colour steel, without significant decreases in efficiency.
Finally, it was shown that by integrating the BIPVT into the building rather than onto the building could result in a lower cost system. This was illustrated by the finding that insulating the rear of the BIPVT may be unnecessary when it is integrated into a roof above an enclosed air filled attic, as this air space acts as a passive insulating barrier
Solar Sailing: applications and technology advancement
No full textHarnessing the power of the Sun to propel a spacecraft may appear somewhat ambitious and the observation that light exerts a force contradicts everyday experiences. However, it is an accepted phenomenon that the quantum packets of energy which compose Sunlight, that is to say photons, perturb the orbit attitude of spacecraft through conservation of momentum; this perturbation is known as solar radiation pressure (SRP). To be exact, the momentum of the electromagnetic energy from the Sun pushes the spacecraft and from Newton’s second law momentum is transferred when the energy strikes and when it is reflected. The concept of solar sailing is thus the use of these quantum packets of energy, i.e. SRP, to propel a spacecraft, potentially providing a continuous acceleration limited only by the lifetime of the sail materials in the space environment. The momentum carried by individual photons is extremely small; at best a solar sail will experience 9 N of force per square kilometre of sail located in Earth orbit (McInnes, 1999), thus to provide a suitably large momentum transfer the sail is required to have a large surface area while maintaining as low a mass as possible. Adding the impulse due to incident and reflected photons it is found that the idealised thrust vector is directed normal to the surface of the sail, hence by controlling the orientation of the sail relative to the Sun orbital angular momentum can be gained or reduced. Using momentum change through reflecting such quantum packets of energy the sail slowly but continuously accelerates to accomplish a wide-range of potential missions
Solar sail formation flying for deep-space remote sensing
No full textIn this paper we consider how 'near' term solar sails can be used in formation above the ecliptic plane to provide platforms for accurate and continuous remote sensing of the polar regions of the Earth. The dynamics of the solar sail elliptical restricted three-body problem (ERTBP) are exploited for formation flying by identifying a family of periodic orbits above the ecliptic plane. Moreover, we find a family of 1 year periodic orbits where each orbit corresponds to a unique solar sail orientation using a numerical continuation method. It is found through a number of example numerical simulations that this family of orbits can be used for solar sail formation flying. Furthermore, it is illustrated numerically that Solar Sails can provide stable formation keeping platforms that are robust to injection errors. In addition practical trajectories that pass close to the Earth and wind onto these periodic orbits above the ecliptic are identified
Towards optimal solar tracking: a dynamic programming approach
No full textThe power output of photovoltaic systems (PVS) increases with the use of effective and efficient solar tracking techniques. However, current techniques suffer from several drawbacks in their tracking policy: (i) they usually do not consider the forecasted or prevailing weather conditions; even when they do, they (ii) rely on complex closed-loop controllers and sophisticated instruments; and (iii) typically, they do not take the energy consumption of the trackers into account. In this paper, we propose a policy iteration method (along with specialized variants), which is able to calculate near-optimal trajectories for effective and efficient day-ahead solar tracking, based on weather forecasts coming from online providers. To account for the energy needs of the tracking system, the technique employs a novel and generic consumption model. Our simulations show that the proposed methods can increase the power output of a PVS considerably, when compared to standard solar tracking techniques
Design of a GaInP/GaAs tandem solar cell for maximum daily, monthly, and yearly energy output
No full textSolar concentrator cells are typically designed for maximum efficiency under the AM1.5d standard spectrum. While this methodology does allow for a direct comparison of cells produced by various laboratories, it does not guarantee maximum daily, monthly, or yearly energy production, as the relative distribution of spectral energy changes throughout the day and year. It has been suggested that achieving this goal requires designing under a nonstandard spectrum. In this work, a GaInP/GaAs tandem solar cell is designed for maximum energy production by optimizing for a set of geographically-dependent solar spectra using detailed numerical models. The optimization procedure focuses on finding the best combination of GaInP bandgap and GaInP and GaAs sub-cell absorber layer thicknesses. It is shown that optimizing for the AM1.5d standard spectrum produces nearly maximum yearly energy. This result simplifies the design of a dual-junction device considerably, is independent of the optical concentration up to at least 500 suns, and holds for a wide range of geographic locations. The simulation results are compared to those obtained using a more traditional, ideal-diode model. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI:10.1117/1.3633244
Harnessing high altitude solar power
No full textAs an intermediate solution between Glaser's satellite solar power (SSP) and ground-based photovoltaic (PV) panels, this paper examines the collection of solar energy using a high-altitude aerostatic platform. A procedure to calculate the irradiance in the medium/high troposphere, based on experimental data, is described. The results show that here a PV system could collect about four to six times the energy collected by a typical U.K.-based ground installation, and between one-third and half of the total energy the same system would collect if supported by a geostationary satellite (SSP). The concept of the aerostat for solar power generation is then briefly described together with the equations that link its main engineering parameters/variables. A preliminary sizing of a facility stationed at 6 km altitude and its costing, based on realistic values of the input engineering parameters, is then presented
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