Novel tandem solar cells that are fabricated with each layer processed from solution using bulk heterojunction materials comprising semiconducting polymers and fullerene derivatives.   (more...)

Titanium dioxide (TiO2) has been extensively investigated as a photoanode for photoelectrochemical (PEC) water splitting, because of its favorable band-edge positions, strong absorption, superior chemical stability, photo-corrosion resistance, and associated low cost; however, reported photocurrent densities and photoconversion efficiencies of TiO2 photoanodes are substantially lower than projected.  UC Santa Cruz researchers have developed a strategy which demonstrates that hydrogen treatment can significantly enhanced the photoconversion efficiency of TiO2 materials by improving their donor density and electrical conductivity. (more...)

A novel invention which allows the fabrication of heterojuctions consisting of relaxed layers of crystals with the same lattice structure but different lattice constants.  (more...)

University researchers have developed a miniature relay switch, with an overall volume of less than 100 mm3 that can handle up to 40 W of DC or 60 Hz line power. This invention also relates to methods of manufacturing these relay devices directly within or on any of the following using standard electronic manufacturing techniques: lead frames, substrates, microelectronic packages, printed circuit boards, flex circuits, and rigid-flex materials. (more...)

Photoelectrochemical (PEC) cells use photons to split water into hydrogen and oxygen gases and offer a promising method for hydrogen production that is directly driven by solar energy. Silicon (Si) is an attractive candidate for PEC cell application because of its moderate energy band-gap and low-cost. However, an insulating oxide film rapidly forms on the surface of Si in aqueous solution under light radiation and becomes passivated. Research on using n-type Si photoanode focuses on altering charge transfer kinetics at the semiconductor/liquid interface to improve the current efficiency for the net water oxidation while limiting the anodic decomposition current. (more...)

Solar trackers have been an effective solution to generate solar energy.  In the past to reach 200 degree Celsius temperature, devices with tracking requirement have been used. The problem with these devices is that they are costly to install and maintain. In addition, solar trackers require repairs and are likely to get damaged in extreme weather conditions like a storm. The solar industry now needs a technology that will be simple, inexpensive and self-contained (more...)

Developing a feasible method for renewable energy generation has become a focus due to concerns over global warming and increased demand for energy. Among renewable energy sources, solar energy has attracted the most attention but production scaling and rising costs are hurdles for photovoltaic technologies to compete with traditionally generated power. In so called "second generation" solar cells, CIGS and its related materials are utilized for the fabrication of low-cost and high-efficiency solar cells. However, the continued supply of the rare metal indium in the mass production stage has created major concerns. (more...)

An Alternative to solar thermal electricity generation and solar photovoltaic electricity generation is the direct conversion of solar energy into electricity by a solar thermoelectric system. Thermoelectric generators convert thermal energy directly into electricity, relying on the Seebeck effect in solid materials. The Seebeck effect is a process whereby a temperature difference across a material generates electricity. In a solar thermoelectric generator, solar radiation is absorbed and the heat generated from the solar radiation is transferred to the hot side of the thermoelectric device, thereby creating a temperature difference across the thermoelectric device which produces electricity via the Seebeck effect. Also solar thermoelectric generators are scalable and relatively cost effective for residential applications. Regardless of what solar electricity generation system is used, the main problem associated with solar energy is that it is an inherently intermittent energy source. Solar radiation output varies throughout the day and is often affected by cloud cover. Thus an important aspect of solar electricity generation is being able to store and being able to use the solar energy to generate electricity generation is that the conversion efficiency between solar energy to electricity is low and the substantial amount of solar energy is wasted in the form of heat. To counteract this, the wasted heat from the solar electricity generation could be recovered and used for a solar fluid heating system or for another thermoelectric generation system and therefore increase energy conversion efficiency.  (more...)

A method for synthesizing iron pyrite (FeS2) semiconductor films on solid substrates to serve as the active layer of a solar energy conversion device (e.g. solar cell). (more...)

A method for fabricating low cost, large scale, thin film substrates in the III-nitride materials family. (more...)

Through an effort to better predict the solar energy conversion of PV cells in regions of occasional cloudiness, the subject software was developed to process optically captured whole-sky images, differentiate clouds from clear sky, and correlate said cloud coverage with the productivity of nearby PV installations. Mapping the frequency and density of local cloud coverage can have valuable implications in planning a new solar collection installation, and/or for load balancing with other sources of power when the system identifies an impending reduction in solar efficiency due to passing clouds.This technology can be more fully explored at the following link, which features a roll-out of this system at UC San Diego. See http://maeresearch.ucsd.edu/kleissl/SolarPowerForecasting.pdf (more...)

Using only the measure of output power from a solar installation, this method allows for the determination of azimuth and tilt-angle at which a panel is installed and calculation of the solar radiation received by the panel in generating the measured output power. Presently, if one wishes to ascertain the installation parameters of a solar panel, or series of panels, a manual field measurement is required using an inclinometer and compass. This is a burdensome manual process, which along with the alternative approach of airborne remote sensing for azimuth and tilt-angle, is cost prohibitive. By simply analyzing the output power from the PV system, the azimuth and tilt-angle for any panel installation can be assessed, providing validation that the system is installed and operating per design. This capability should find ready application in validating solar installations for managing rebate programs (e.g. California’s rebate payments are partially based on tilt and azimuth angle) and ensuring optimal alignment of panels by system operators. (more...)

Solar thermal concentrators are used by concentrating solar radiation and converting it to high-temperature steam or gas to drive a turbine or motor engine for power generation. A wide range of concentrating technologies has been developed. However, it remains challenge and demand to optimize the overall thermodynamically efficient solar thermal systems in achieving the engineering optimum. Evacuated solar thermal tubes are widely used as solar collectors and come in a variety forms. An innovative design methodology based on the combination of optimal nonimaging optics and heat transfer techniques produces a remarkable effective non tracking solar collector for high temperature. It is promising to be well applied in balancing the competing engineering constrains in constructing the collector. (more...)

Solar collectors have been designed differently with various desired performances for application in solar energy generation. Solar thermal collector is designed to collect heat by absorbing sunlight. Solar electric generation system is designed to generate electricity directly from sunlight using photovoltaic (PV) materials. Solar collectors may employ light concentrators to concentrate solar light onto the energy transducer for effective energy conversion, and many forms of concentrators have been developed in reaching higher concentration. Concentrators may be imaging or nonimaging. To reduce cost and increase the overall efficiency of a solar system, one promising technology is to combine heat and electric power generation. (more...)

Operation of axial or radial turbines under wet conditions is generally avoided because of three performance disadvantages: (1) droplets are unlikely to strike the turbine blades in a way that efficiently converts their momentum to rotor torque; (2) the liquid film that forms on the turbine blades alters the aerodynamics of the flow and makes it challenging to optimize the design for performance; and (3) droplet impingement in conventional turbines can cause the rotor blades to erode, and thereby shorten the life of the turbine. To address this problem, UC Berkeley researchers have developed a turbine design that is optimized for wet operation (i.e. operation with internal flow of liquid and vapor fluid phases). As the replacement for the expansion valve in vapor compression refrigeration and air-conditioning systems, this innovation can significantly enhance the energy efficiency of vapor compression systems by extracting additional power output and increasing the heat absorbing capacity of the refrigerant in the evaporator. Another version of the innovation can be used as the work output turbine in a Rankine cycle power generation system designed for wet turbine operation. This wet expansion cycle design has significantly higher heat input heat exchanger effectiveness, and higher energy efficiency than conventional Rankine cycles with superheat.  (more...)

Compared to conventional semiconductor devices, polymer semiconductor devices are particularly attractive for applications in which flexibility, light weight, large-area thin film, low-cost, and/or environmentally safe characteristics are important. However, despite these potential advantages, devices made from neutral conjugated polymers have found limited applications due to their low carrier mobility and charge injection barrier at the polymer/electrode interfaces. Polymer devices that could overcome these limitations and offer the advantages listed above would be of great benefit. The p-i-n junction diodes disclosed here do exactly that: they overcome the noted limitations while exhibiting many of the benefits associated with polymer devices. (more...)

For many solar energy applications, it is desirable to increase the light flux incident upon a light absorbing element such as a photovoltaic (PV) cell or a tube used for heating a working fluid. The use of a light-concentrating collector can be a significant factor in lowering overall system costs, particularly by increasing the energy conversion efficiency of the light absorbing element and by decreasing the size of the light absorbing element (a particularly important cost consideration for expensive PV cells). However, concentrators also have a serious drawback—excessive heating of a light-absorbing element can cause serious decreases in light conversion efficiency. In a typical PV cell, for example, each 1°C increase in temperature reduces its light-to-electricity conversion efficiency by ~0.5%. Thus, a significant on-going challenge in solar collector design is to optimize the overall thermodynamic efficiency of the system, not merely to facilitate high light concentrations on the light absorbing surfaces. (more...)

Solar concentrators used for heating a working gas or fluid have serious trade-offs in terms of the concentration factor attainable (high light concentrations being desirable for achieving high temperatures and, in power generation applications, high thermodynamic efficiencies) versus the cost of mounting and moving relatively large reflective or refractive surfaces and their associated light-absorbing elements in order to track the Sun's movements across the sky. (more...)

While the Sun offers the most abundant source of renewable energy, the generation of electricity from sunlight is currently not cost-effective in many situations because of the inherent limitations of photovoltic (PV) cells and typical lighting conditions. The production of commonly-used silicon PV cells demands expensive semiconductor fabrication methods and consumption of limited high-grade silicon feedstocks. Newer thin-film cell technologies, while using cheaper fabrication methods, consume even scarcer exotic materials. Moreover, at typical sunlight intensities, silicon PV cells are relatively inefficient (usually converting 15%-19% of the incident sunlight to electricity), requiring large panels for a given peak power output. More exotic PV materials can achieve higher efficiencies, but only at a prohibitively higher cost. To reduce costs, it is desirable to increase PV cell efficiencies while minimizing the use of costly materials and fabrication techniques. One promising way to accomplish this is with concentrator PV (CPV) systems, where an inexpensive optical element (usually made of glass) covering a large sun-lit area is used to greatly concentrate the light onto a small high efficiency PV cell. Higher light intensities enable higher efficiencies in converting sunlight to electricity while greatly reducing the size of the PV cell required. Practical CPV designs seek to minimize weight per unit area of the optical element while maintaining a high concentration ratio and high optical efficiency. (more...)

Evacuated-tube solar collectors, in conjunction with non-tracking, non-imaging parabolic concentrators, can heat working fluids to 200°C at efficiencies near 50%, providing a relatively economical means for capturing and transferring solar energy for use in cooling, heating, and power generation applications. However, the transfer of heat from the solar energy-absorbing element to the working fluid within such collectors poses a significant challenge to the feasibility of these systems. It is a critical limitation of existing evacuated-tube collector designs because of trade-offs between resistance to heat transfer, cost, and safety. (more...)

  As the quest for clean, renewable energy intensifies, the proposition of extracting energy from ocean waves sounds increasingly more attractive. The wave energy resource is recognized to contain the highest energy density among renewables and is virtually inexhaustible. Moreover, unlike wind, the wave climate is more predictable and is generally less intermittent. The primary waves of interest are those generated by the blowing of the winds, which in turn are a product of differential heating of the earth. Therefore, the wave energy may be considered as a concentrated form of solar energy. The size (and associated energy) of the resulting waves are a function of wind speed, wind duration, and distance over which the wind blows, referred to as fetch. Original solar power levels of 100 W/m2 can be transformed into waves of power levels of over 1000 kW/m of wave crest length. Researchers at UC Berkeley have developed a new device that applies the principle of parametric excitation to ocean wave energy converters. The proposed mechanism operates fully autonomously when the buoy is heaving. The application leads to greater energy in the oscillatory motion, resulting in increased motion amplitude or, in situations where amplitude limit is reached, the possibility of using higher damping values in the power takeoff system to keep the oscillations bounded. In either case, when power take off is achieved with hydraulic damping, it would be possible to harness significantly more power from the device, compared to a unit simply excited by the waves.   (more...)

  In the manufacture of very large scale integrated circuits, polycrystalline-silicon (poly-Si) films are typically formed directly by low- pressure chemical vapor deposition (LPCVD) at temperatures above 600C, using silane as the precursor gas. Use of such a high process temperature renders this approach unsuitable for formation of poly-Si films on low-cost glass and plastic substrates and on substrates with completed CMOS integrated circuits. Various other techniques have been attempted, with less than ideal results, toward crystallizing amorphous silicon films without subjecting the material to excessive temperatures for the given application. Accordingly, a need exists for a method of readily forming polycrystalline films without subjecting the substrate to high temperatures, or requiring the use of complex processing steps. Researchers at UC Berkeley have developed a technology that enables the forming of polycrystalline semiconductor at low temperatures and without the use of complex processing steps. The technology allows for production of a continuous polycrystalline silicon film with excellent physical and electrical properties.  The result is a low-temperature, low-cost substrates such as glass and plastic, which is extremely important for the development and commercialization of solar cells, thin film transistors, and micro-electromechanical systems (MEMS).   (more...)