Optical spectrum splitting systems that divide light between independent solar cells of different band gaps have received increasing attention in recent years as an alternative to expensive multijunction cells for high-efficiency PV. Most research, however, has focused on dichroic filters and other photonic structures that are expensive to manufacture. This has the effect of transferring the cost of the system from the PV cells to the optics. As a low-cost spectrum splitting approach we designed a prismatic lens that simultaneously splits and concentrates light and can be fabricated by injection molding. We present experimental results of a two-cell demonstration system, and calculations for low-cost configurations of commercial solar cells, enabled by the removal of lattice-matching requirements.
High efficiency concentrator photovoltaic systems are currently based on costly III/V cells and, to offset the high cell capital cost, elevated optical concentrations are used, with consequent reduction in acceptance angles and tight tolerance optics. While this allows for spectacular conversion efficiencies, it does not provide cost effectiveness in a market dominated by low efficiency/low cost technologies. An alternative approach, well known in literature, is based on the combined use of an optical concentrator and a spectral splitting element allowing for the use of separate cells with different spectral responses and, thus, opening the way to a much wider range of possible materials and technologies. While many configurations have been presented during the years, optical efficiency has often been an issue due to the separate action of the concentrating and splitting element. We propose here, as substantial evolution of a previous design , a single injection molded plastic non-imaging optical element embodying both two axes concentration and spectral splitting functions. Based on the specific dispersion characteristics of polycarbonate and on a constructive analytical design procedure, this element allows for optical efficiencies exceeding 80%. Theory, simulations and preliminary experimental results will be presented.
In this article we discuss an emerging concept for non-mechanical solar tracking that can have a significant impact for the design of next generation concentrator photovoltaics systems. Based on the modification of the optical properties of the concentrator elements instead of their mechanical rearrangement, self-tracking concentrators, with recently demonstrated prototypes, could make the mechanical trackers redundant expanding the scope of application of CPV systems. We propose here a new approach to a reactive-tracking system, analyze its underlying physics and discuss initial experimental and simulation results towards the development of a prototype.
High Concentration photovoltaics systems (HCPV) allow for improved efficiency but, due to Etandue conservation, have low optical acceptance. Mechanical tracking is normally employed to maintain the necessary alignment of the system axis with the sun. This, however, prevents HCPV from integration in urban and residential environments. We propose here optofluidic based approaches to achieve a stationary tracking optical concentrator by internal modifications of the system optics based on the manipulation of liquid interfaces or multiphase systems. Transparency induced by phase transitions and electrophoretic driven mechanisms will be discussed. Theoretical framework, multiphysics modeling and preliminary experimental results will be presented.
The combination of optical concentration, spatial spectral splitting and the use of multiple cells of suitable bandgap, could provide a path for high PV conversion efficiency without requiring the use of monolithically integrated multi junction solar cells. We propose a dispersive point focus single element concentrator and spectral splitting optics coupled with multiple cells employing Cu(InxGa1-x)Se2 cells for the mid wavelengths region. The optical element is designed, taking advantage of the dispersion characteristics of the employed material, to concentrate and provide spatial spectral splitting. The component can be realized injection molding and be mass produced at low cost.