T. Ratcliff

A 20-sun hybrid PV-Thermal linear micro-concentrator system for urban rooftop applications

A unique, linear, low-concentration, hybrid ‘micro-concentrator’ (MCT) system concept has been developed specifically for urban rooftop environments. The light-weight, low-profile form factor satisfies aesthetic demands for general rooftop solar technologies, and is a marked departure from conventional linear concentrator systems. Valuable thermal energy, normally of nuisance value only, and usually wasted by conventional CPV, is extracted via a heat transfer fluid. The recovered thermal energy can be used for applications ranging from domestic hot water through to space heating, ventilation, and air conditioning (HVAC), and process heat. The system can be modularly configured for hybrid concentrating PV-Thermal (CPV-T) or thermal-only operation to meet specific customer demands. At a 20x concentration ratio, system output of 500 Wpe and 2 kWpt is expected, for a combined system efficiency of up to 75%. The MCT is constructed from mature, proven technologies and industry-standard processes. An installed system cost of less than US

Rounded rear pyramidal texture for high efficiency silicon solar cells

2/Wpe is targeted, and commercial availability is expected to commence in 2011.

Flexible sliver modules

Interdigitated back-contact (IBC) solar cells developed in the past two years have efficiencies in the range 24.4%-25.6% As high as these efficiencies are, there are opportunities to increase them further by improving on the light trapping. Silicon solar cells incorporating double-sided pyramidal texture are capable of superior light trapping than cells with texture on just the front. One of the principle losses of double-sided pyramidal texture is the light that escapes after a second pass through the cell when the facet angles are the same on the front and rear. This contribution investigates how this loss might be reduced by changing the facet angle of the rear pyramids. A textured pyramid rounding is introduced to improve the light trapping. The reduction in surface recombination that rounding the facets introduces is also evaluated. With confocal microscopy, spectrophotometry and ray tracing, the rounding etch time required to yield the best light trapping is investigated. With photoconductance lifetime measurements, the surface recombination is found to continue to decrease as the rounding time increases. The spectrophotometry and ray tracing suggests that the double sided textured samples featuring rounded rear pyramids have superior light trapping to the sample with a planar rear surface. The high-efficiency potential of rounded textured pyramids in silicon solar cells is demonstrated by the fabrication of 24% efficient back-contact silicon solar cells.

Materials and manufacturing processes for high-efficiency flexible photovoltaic modules

This paper presents the design, fabrication, testing, and integration with equipment of a flexible photovoltaic module. The modules are based on mono-crystalline silicon Sliver cells. Tests have been developed to specifically test flexible modules, including their flexibility, abrasion resistance, power to weight ratio, and partial shading. The results of a 0.1 m2 module with 13 W power output and 178 W/kg are presented.

The rise of non-imaging optics for rooftop solar collectors

An overview of the materials, processing techniques, and characterisation procedures for flexible solar modules is presented. Flexible modules are lightweight, roll-able, and/or foldable for storage and transport. The design approach selected by the Australian National University incorporates very thin, high-efficiency crystalline silicon solar cells embedded between flexible coversheets, and supported by silicone encapsulant and flexible electrical contacts. The modules can be fabricated using a number of approaches including constructing the circuitry separately to the packaging, or using the packaging as both a protective layer and a base for circuitry.

An Examination of Three Common Assumptions Used to Simulate Recombination in Heavily Doped Silicon

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.