Energy harvesting with a photovoltaic cell requires an efficient dc-dc converter that operates with very low voltage inputs and whose output can charge an external battery. The newly introduced LTC3105 meets these requirements.
Sam Davis writes:
ENERGY HARVESTING CAN EMPLOY SURPLUS OR AMBIENT energy to trickle charge a battery that supplies system power. This eliminates the need to for an ac power line-based recharging circuit, which may be impractical in a remote application. Typically, these applications require very low average power, but can require periodic pulses of higher load current. The Linear Technology LTC3105 is intended for these types of energy harvesting applications.
The LTC3105 is a high efficiency dc-dc boost converter (Fig. 1) that has a 250mVstart-up capability. A resistor divider connected between the VOUT and FB pins adjusts the converter output from 1.5V to 5.25V. An integrated maximum power point controller (MPPC) optimizes performance from photovoltaic (PV) cell inputs. The LT3105’s 3mm × 3mm DFN package (or MSOP-12) and very small external components offer a compact solution for energy harvesting.
LTC3105 DC-DC Boost Converter Harvests Photovoltaic Energy - [Link]
When you expose the silicon die of a transistor to a light source a charge is produced. CircuitsDIY opened up a 2N3055 transistor and did some experimenting. With the help of a magnifying glass he was able to built up a charge of 0.65V and produce 42.2mA of current. [via]
Most photovoltaic cells are made of silicon chip above which there resides a very thin layer of noble metal through which around 1% of photon particles enter the material and activates electron flow. Here I’m showing how to make one simple solar panel using transistor.
Testing the photovoltaic effect with a transistor - [Link]
Researchers at Notre Dame have developed a solar cell that is remarkably easy to assemble because the middle layer can be painted onto a clear electrode. First, they mix t-butanol, water, cadmium sulfide and titanium dioxide for 30 minutes. Next, they mask off a clear electrode with office tape. Once the tape is in place, they spread the mixture onto the electrode and then anneal it with a heat gun. Finally, they sandwich an electrolyte solution between the new electrode and a graphene composite electrode. And then, it’s time for testing under a beam of artificial light.
Painting Solar Cells with Nanoparticle Paste - [Link]
High brightness LEDs and special optics allow street lamps to be spaced up to 50 meters apart — much wider than is possible with other solutions. By charging these street lamps efficiently during daylight hours using solar energy, the capacity of the conventional electricity grid can be supplemented, saving money and reducing CO2 emissions. This solution dubbed Solar Gen2 and developed by NXP Semiconductors in collaboration with Philips Lighting has resulted in the most cost-effective solution per km of road lighting and provides a serious alternative to grid-connected AC systems.
NXP’s MPT61x range of intelligent charge controllers for maximum power point tracking (MPPT) make it possible to transfer the maximum amount of power from the solar panels to the batteries, achieving up to 98% power conversion efficiency with solar photovoltaic (PV) cells. The controller that includes an ARM7TDMI-S MCU core running at 70 MHz features intelligent algorithms for battery charging and discharging to maximize battery life and it is also capable of dimming light levels as needed based on self-learning and a history log. [via]
Self-learning solar-powered LED street lights save energy - [Link]
Solar PV Monitoring System / OpenEnergyMonitor. Glyn writes – [via]
Here is the documentation for a solar PV monitoring system that’s been developed as part of the OpenEnergyMonitor project. It’s based on Arduino and is fully open-source; hardware, firmware and web application.
The system monitors both generation and consumption and gives the user a clear indication of when their household electricity demands are being met by their solar PV array (green light) or when their not (red light). The wireless display also shows how much electricity is currently being exported or imported. Monitoring data is also posted on-line by a wireless web-connected base-station to our powerful open-source web-application emoncms.
This development is part of the actively on-going OpenEnergyMonitor project to design and build open-source tools for the monitoring, visualization and control of energy.
Open-source solar PV monitoring system - [Link]
Jon Gabay writes:
Renewable energy can be an expensive endeavor and photovoltaic systems are no exception. Ground and roof-mount frames have to be tough enough to handle weather extremes and conditions, and can be very costly even without tracking.
If you use storage batteries, there are large initial expense and the replacement costs every so many years to be considered. On the positive side, 90 percent of the materials in a lead acid battery are completely recyclable. Chargers and inverters are not cheap either.
The panels are the biggest expense. Fortunately, with higher manufacturing capacities coming on line, photovoltaic panel pricing is starting to come down, but not yet to the level of mass deployment.
In 2008, the price of $1000/kg of silicon kept panels at process of three to four dollars per watt. Combining the increase in silicon production capacity with the global slowdown has dropped the price to the $40/kg level meaning we may soon really be at the coveted one dollar per watt price point that many say will make photovoltaic solar on a level playing field with non-renewable energy technologies. We are presently around $1.50 per watt.
To get to that level of high deployment, payback has to be quicker. The lower cost promise of solar panels is one factor for quicker return on investment. The other is the changed architecture of photovoltaic systems stemming from the use of micro inverters.
Either way, the market for the electronics that make use of the solar energy more efficiently is about to explode.
Squeezing Energy from Photovoltaic Panels - [Link]
Research at Lawrence Berkeley National Laboratory (Berkeley Lab) has led to solar cells with record-breaking efficiency. Contrary to conventional scientific wisdom, it turns out that efficient solar cell materials are characterised by high photon emission instead of high photon absorption.
According to the researchers, external fluorescence is the key to approaching the theoretical maximum efficiency for conversion of sunlight into electricity. The maximum efficiency, called the Shockley-Queisser (S-Q) efficiency limit, is approximately 33.5% for a single p-n junction. An analysis by a member of the research team indicated that gallium arsenide is capable of approaching the SQ limit. Based on this work, Alta Devices Inc., a private company spun off by the researchers, has fabricate gallium arsenide solar cells that achieved a record conversion efficiency of 28.4%. [via]
Researchers find key to better solar cell efficiency - [Link]
As renewable energy is becoming integrated into our everyday lives, new terms such as solar panel, photovoltaic and solar cell are more common and new devices, such as outdoor LED lighting are using this technology. The sun emits many forms of radiation. The best way to describe this is that there are ‘waves’ of energy that radiate from the sun at different frequencies.
This is only partially the truth as there is both a wave and particle nature to light.
The light spectrum is divided into different sections. It begins with the highest, gamma rays and ends with the lowest, long wave radio. Only a small portion of this is visible, called the visible spectrum and this occurs towards the middle of the range which lies between Ultraviolet and Infrared frequencies. Ultraviolet radiation is what burns the skin and can cause skin cancer. It is blocked by most types of glass and is partially reduced by the atmosphere especially the ozone layer. Infrared radiation is what provides the earth with heat and it is that which is trapped by green house gasses, carbon dioxide mainly and is causing global warming.
Infrared radiation is targeted by solar panels. This basically uses the energy generated by the radiation to heat water in pipes that flows and generates electricity. This can be used to charge a battery which could then power said LED lighting. As mentioned previously there is a dual nature to light. It consists of both a particle and a wave. It might help to think of the particles moving in a wave like pattern but the reality is more complex than that. The important thing to remember is that the light particle, the photon, is what is targeted by a solar cell. Read the rest of this entry »
Daniel F. Butay & Michael T. Miller writes:
The design and implementation of a Maximum Peak Power Tracking system for a photovoltaic array using boost DC-DC converter topology is proposed. Using a closed-loop microprocessor control system, voltage and current are continuously monitored to determine the instantaneous power. Based on the power level calculated, an output pulse width modulation signal is used to continuously adjust the duty cycle of the converter to extract maximum power. Using a Thevenin power source as well as a solar panel simulator, system design testing confirms simulation of expected results and theoretical operation is obtained.
Maximum Peak Power Tracker - [Link]
For the last year I’ve been working on a prototype for a Solar Inverter that can be Grid Intertied. A solar inverter takes the 12V DC (or other voltages) from the solar panels and converts it to 120V AC which is the power that most of your household appliances use. A Grid-Intertied inverter allows you to feed that power back into power grid (your house power) to help power your household appliances.
My goal was to design a small inverter, about 100W, that could be used with one solar panel and could be grid intertied. My second prototype (pictured above) has achieved these design goals. So on these web pages I’m going to document the design of the hardware and the software of my solar inverter. I’m releasing these designs to public without restrictions. All I ask is that if you use any of my design that you credit me and add a link back to this website. I hope these designs will help further the work of other people in this area.
Solar Grid-Intertie Inverter - [Link]