Electrical engineers of the University of Princeton are working on a cheap solar-powered charging system that can be printed on plastic and that transfers the produced electricity wirelessly. The solar cells are made from amorphous silicon (a-Si), a non-crystalline form of silicon. Crystalline silicon (c-Si) is much more efficient when it comes to converting sunlight into electricity but a-Si has the advantage that it can be processed at much lower temperatures (75 °C against 300 °C for c-Si), allowing it to be printed on plastic sheets.
The electric circuit is made out of the same material as the solar cells. And although a-Si has a lower electrical performance than c-Si, when it comes to producing cheap electricity-generating plastic sheet which can be put up anywhere, a-Si is best. By making the charging system available at a large scale, the Princeton engineers aim to have wireless electricity everywhere. [via]
Omnipresent Sun-Powered Wireless Charging Stations - [Link]
SolarCharge 200ds230 rev 2 – An unconventional, scalable high efficiency 12V solar power system, a battery charge controller with low voltage cutout to protect the battery. [via]
An unconventional, scalable high efficiency 12V solar power system and battery charge controller with low voltage cutout to protect the battery. (ideal for systems of 50W or less).
The most common solar charger consists of a Schottky diode to prevent the battery from draining into the PV panel and a shunt regulator that effectively short circuits the panel once the battery is fully charged.
One problem with this approach is diode losses and the resulting heat. If a 50W 12V panel supplies 4A to the battery, the Schottky diode will drop about 0,4V across it dissipating about 1,6W of heat. This requires a heat sink and loses power to heat. The problem is that there is no way of reducing the volt drop, paralleling diodes may share current, but the 0,4V will still be there. The circuit uses a MOSFET in stead of the usual diode and the primary power loss is resistive.
Scalable 12V solar power system and battery charge controller - [Link]
Arup Basak writes: [via]
O.S.S.D.A.S v1 stands for Open Source Solar Data Acquisition System. I have been working on this project since last few months. The picture above is the not the first prototype, but the first working prototype that looks like quite complete. There will be further revisions to the hardware and software for best efficiency and accurate results. Moreover, the recorded digital data should be rich enough to reflect the real world data’s mirror.
- Logs everything into attached SD card for data analysis in PC. A typical 1GB SD card can store years of data. Data is recorded in frequency of few seconds. Enough to plot a graph to analyze performance of short periods of ten minutes too.
- Keep track of the solar panel voltage, battery voltage, charge current and other parameters
- Keeps track of other data such as temperature, etc
- Can work without the LCD and still record information to the SD card and vice versa.
Open Source Solar Data Acquisition System - [Link]
Steve Taranovich writes:
Home energy systems based on renewable sources, such as solar and wind power, are becoming more popular among consumers and will gain increasing support from governmental bodies.
In this article, the power inverter will be discussed in the context of solar energy, especially as it relates to the latest, low power microinverter architectures that make the most sense in converting a photovoltaic (PV) panel’s DC output to an AC signal for residential use.
Microinverters are installed on each individual PV panel and typically handle 300 W. Microinverters provide the benefit of scalability for those who want to start small, yet have full DC/AC conversion with maximum power point tracking (MPPT). Many people want to put their excess power back onto the power grid, which will speed up the return on investment (ROI) time and ultimately could lead to freedom from grid reliance. The technology that will enable ubiquitous architectures like this on our roof is getting closer.
An Engineer’s Guide to Power Inverters for Solar Energy Harvesting - [Link]
The internet community quite enjoying the destabilizing effects of global connectivity on the status quo, fights any attempt at restriction tooth and nail. Organizing themselves both on- and offline they managed to stop anti-piracy laws like the Stop Online Piracy Act (SOPA) or the Protect IP Act (PIPA) from passing. But it wouldn’t be the internet community if people weren’t working on technological solutions as well. Hackers, engineers and freedom-loving folk are working to create a decentralized, independent network where you can’t stop the signal. [via]
Build a Solar Powered Wikipedia Server - [Link]
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]
Sergei Bezrukov writes:
This project does not directly involve a microcontroller. However, it is designed with a goal to power a PIC-based device. I used electronics from a garden light unit. This device has a solar cell mounted on the top if the light, an LED, a board with a circuit that turns LED on in the dark, and a battery. The battery block is a set of two AA Nickel Metal Hydride Batteries, the reverse engineered schematics of the control board is shown below. The photo cell has a high resistance in the dark (more that 1Mohm), while its light resistance is only about 150Ohm. This way the transistor, which serves as a key, is closed during the day time and the LED is not powered, allowing the solar cells to charge the battery.
Solar charger for three AAA batteries - [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]