In this paper we explore the use of non-imaging optics for rooftop solar concentrators. Specifically, we focus on
compound parabolic concentrators (CPCs), which form an ideal shape for cylindrical thermal absorbers, and for linear
PV cells (allowing the use of more expensive but more efficient cells). Rooftops are ideal surfaces for solar collectors as
they face the sky and are generally free, unused space. Concentrating solar radiation adds thermodynamic value to
thermal collectors (allowing the attainment of higher temperature) and can add efficiency to PV electricity generation.
CPCs allow that concentration over the day without the need for tracking. Hence they have become ubiquitous in
applications requiring low concentration.
A new dielectric totally internally reflecting concentrator (DTIRC) design has been developed for use with bifacial photovoltaic cells. The structure incorporates the bifacial cell standing vertically at the base of the structure, immersed in dielectric. DTIRC structures with single-sided photovoltaic receivers, like CPC structures, are designed using the paths of the edge rays to calculate the sidewalls. If these rays successfully hit the receiver then all rays at lower angles will also hit the receiver. In a vertical DTIRC structure, it is not just the edge rays that need to be taken into account in designing the structure. Around the bifacial receiver, rays at normal and close to normal incidence are the hardest to totally internally reflect onto the receiver. Once outside the area closest to the receiver, a modification of the maximum concentration method is used to design the remainder of the sidewalls. Ray tracing has been performed to confirm that the vertical DTIRC structure concentrates light as expected. The structure gives a lower concentration than a CPC with vertical bifacial receiver, however it is also a shorter structure with more uniform flux distribution over the receiver (leading to lower losses in the photovoltaic receiver).
Sliver solar cells are thin, mono-crystalline silicon solar cells, fabricated using micro-machining techniques combined
with standard solar cell fabrication technology. Sliver solar modules can be efficient, low cost, bifacial, transparent,
flexible, shadow-tolerant, and lightweight. Sliver modules require only 5 to 10% of the pure silicon and less than 5% of
the wafer starts per MWp of factory output when compared with conventional photovoltaic modules. At ANU, we have
produced 20% efficient Sliver solar cells using a robust, optimised cell fabrication process described in this paper. We
have devised a rapid, reliable and simple method for extracting Sliver cells from a Sliver wafer, and methods for
assembling modularised Sliver cell sub-modules. The method for forming these Sliver sub-modules, along with a low-cost
method for rapidly forming reliable electrical interconnections, are presented. Using the sub-module approach, we
describe low-cost methods for assembling and encapsulating Sliver cells into a range of module designs.