Tag Archives: solar

Powering the Pacemaker from Solar Energy

Those suffering from certain ailments of the heart, have to have a pacemaker installed. Surgeons place this tiny medical device in the chest or abdomen of the patient and it helps to control abnormal heart rhythms. The device generates electrical pulses and prompts the heart to beat at a normal rate. Power comes from implanted Lithium-iodide or Lithium anode cells, with Titanium as the encasing metal. The downside to this arrangement is the cells need replacement once they are discharged, and that means periodic surgeries.

To avoid repeated surgeries, scientists prefer using solar cells placed under the skin for continuously recharging the implanted electronic medical devices. According to Swiss researchers, a 3.6 square centimeter solar cell generates enough power necessary to keep a typical pacemaker running through the year.

Lukas Bereuter of Bern University Hospital and his team from the University of Bern in Switzerland have presented a study that provides real-life data on the potential of using solar cells to power implanted devices such as deep brain stimulators and pacemakers. Lukas is confident it will become commonplace to wear power generating solar cells under the skin. This will save patients the discomfort of undergoing repeated surgeries to change batteries of such life-saving devices. Lukas has reported the findings in Springer’s journal Annals of Biomedical Engineering.

Electronic implants are invariably battery powered, with their size depending on the volume of the battery necessary for an extended lifespan. When the battery exhausts is power, it must either be charged or changed. This necessitates expensive and stressful medical procedures involving implant replacements, along with the risk of medical complications for the patient. The implantable solar cell is attractive as it converts the light from the sun penetrating the skin surface to generate enough energy for recharging the medical devices.

Lukas and his colleagues have developed devices specially designed for solar measurement to investigate the feasibility of rechargeable energy generators in real-life situations. The devices measure the output power generated. According to the team, 3.6 square centimeter cells generated enough power and were small enough for the intended implantation.

The team tested ten cells by covering them with optical filters for simulating the properties of human skin. This influenced the amount of sunlight penetrating the skin. A test group of 32 volunteers wore the cells on their arm for one week during summer, autumn, and winter months.

According to the team, the tiny cells were able to generate power more than the 5-10 microwatts required by a regular cardiac pacemaker, irrespective of the season. The lowest power output the team recorded on average was 12 microwatts. The overall mean power obtained from the cells was enough to power a pacemaker completely, or at least extend the lifespan of an active implant. Furthermore, the use of solar cells or energy-harvesting devices for powering an implant dramatically reduces the size of the device, while at the same time, helps to avoid device replacements.

According to Lukas, the results of the study may be suitably scaled up and applied to other mobile applications, especially solar powered applications on the human body. The only aspect that requires attention is the efficiency and catchment area of the solar cell, and the thickness of the skin covering it.

Monitor Your Solar System with a Raspberry Pi

Most photovoltaic systems contain parts such as the solar modules (panels) to provide the electrical power, a battery charger for converting the panel output to the battery voltage, a battery pack to store energy during the day and provide it during the night time, an inverter to transform the battery voltage to the proper line voltage for operating home appliances and an line source selector to switch between the solar and grid power.

When the sun is shining during the daytime, the solar photovoltaic cells convert the sunlight falling on them into electricity. Although the efficiency of the conversion may be only about 17%, solar power can easily reach 1KW/m2 and suitable panels can produce 5000 Watts in these conditions.

Solar panels typically produce a high voltage, 120V DC being a common figure. The battery charger has to convert this to match the battery voltage, generally 48V DC. Solar light power charges the batteries continuously during the daytime; therefore, the charger has to keep tracking the maximum power point to optimize the yield of the system. As the charger has to charge the battery also, this device forms the most elaborate part of the system.

With the above arrangement, the solar panels charge the battery during the daytime and the battery discharges during the night. The size of the battery depends on one day of consumption plus some extra to tide over an overcast day. That also decides the size of the solar panel. Batteries are essentially heavy and the lead-acid types generally have a lifespan of about 7 years.

The batteries feed the inverter, which converts the 48V DC into the line voltage – usually 230V AC or 110V AC. With a 5KW continuous rating, inverters can essentially run almost all household appliances such as the clothes dryer, the washing machine, the dishwasher and the electric kitchen oven. When the inverter is supplying a large load, the battery current may climb up to 200A.

Multiple sensors measure the solar field power from and temperature of the solar modules divided into arrays. The information comes to a PV panel via a CAN bus, which unites all the sensors. The PV panel also acts like a gateway between the CAN bus and a single board computer.

The tiny, versatile single board computer, the Raspberry Pi or RBPi is suitable for gathering data from the PV panel and storing them in a database. On the RBPi is a web server connected to the home Ethernet network.

Another set of sensors monitor the battery voltage, current and temperature. These are also on CAN bus and the information collects on a PV battery monitor board. A Wi-Fi module on the board acts as a gateway between the CAN bus and the Ethernet.

The boards and modules of the monitoring subsystem do not provide any interface with the user, except for a few activity modules. The system is meant for being supervised and controlled remotely. This is possible with a Web User Interface or an Android application.

Long Lasting Solar Aqueous Flow Battery

Yiying Wu, Professor of chemistry and biochemistry at the Ohio State University, Ohio State, and his team has combined a solar cell and a battery to form a single device. A novel solar panel on top of the battery captures energy from sunlight. The battery is able to source 20% of its energy from sunlight. Although the design is pending a patent, the researchers have published their findings in the Journal of the American Chemical Society.

Tests conducted by the researchers show that their solar flow battery produces the same output as a lithium-iodine battery does, even when the solar flow battery had a lower charge. They charged and discharged both batteries 25 times. Each time, they discharged the batteries until the terminal voltage fell to 3.3 volts. Conventional lithium-iodine batteries have high energy densities, approximately twice that of lithium-ion batteries. Hence, lithium-iodine batteries have the potential to fulfill the needs of long-driving-ranged electric vehicles.

In the experiments, lithium-iodine batteries had to be charged up to 3.6 volts, before they could be discharged down to 3.3 volts. Comparatively, solar flow batteries produced the same energy output with a charge of only up to 2.9 volts, as the solar panel made up the difference in their terminal voltage. That represents an energy saving of nearly 20 percent.

The team has made two changes to their earlier design from 2014. The solar panel, which was a mesh earlier, is now a solid sheet. Additionally, they now use a water-based electrolyte within their battery. With water circulating within the battery, the team has assigned the new design to an emerging class called the aqueous flow batteries. Yiying Wu claims their solar battery with aqueous flow is the first of its kind.

The water-based solar battery is compatible with the current battery technology and is easy to maintain. The environmentally friendly technology can be very easily integrated with existing technology.

According to Wu, the design of the solar flow battery is adaptable and can be applied to grid-scale solar energy conversion and storage. In the future, electric vehicles might also benefit from the electrolytic fuels used in the solar flow batteries.

In the earlier design, Wu and his team had designed the solar panel with a titanium mesh, which passed air to the battery. The new design using water based electrolyte does not require air to function, and hence, the solar panel is now a solid sheet.

The solar panel has a red dye so that it can tune in to a specific range of wavelengths of solar light to capture and convert to electrons. The team calls their solar panel dye-sensitized and the electrons it produces serve to supplement the energy stored within the lithium-iodine battery.

The electrolyte within the battery helps to absorb the electrons produced by the solar panel. A typical electrolyte is actually part solvent and part salt. Earlier, the researchers had used the organic solvent dimethyl sulphoxide to dissolve the salt lithium perchlorate. They have now changed over to lithium iodide salt dissolved in water, as this is more eco-friendly and offers higher energy storage capacity at lower cost.

Is Your Solar Panel Installed the Right Way?

Although few people would have noticed, the costs of solar photovoltaic cells have been dropping over the years. As the technology took off, costs plummeted in the first 12 years. However, between 2005 and 2009, global market demand surged, making it difficult for supply to keep up. As manufacturing picked up post 2009, solar PV cell prices have continued their downward trend steadily. Now, it makes sense for companies to switch to PV cells purely based on economics.

As solar grows to become a more attractive option, we see a clear preference in its adoption over adding new wind capacity. Navigant Research has predicted in their recent report that declining prices will result in the global solar PV market exceed $134 billion by 2020 – a phenomenal increase of 50% from this year. That means a solar capacity addition of nearly 435 Gigawatts.

However, getting the maximum benefit from solar PV cells requires mounting them the right way. As the sun traverses the sky in the daytime, the PV cells must either follow the trajectory of the sun or be mounted in the most optimum way for them to catch most of the sunlight. Automatically turning the PV cells to face the sun requires elaborate sensing and expensive movement mechanisms. Therefore, most people prefer fixed installations that are simple to put up and maintain.

Another thing to consider is the latitude tilt of the location where you intend to install the solar cells. If your location is below the 25 degrees latitude, tilt the solar panel towards the sun the same amount as the latitude number. At 25 degrees latitude, your panel must tilt by 25 degrees. Above 25 degrees, you will need to add five degrees for each additional five degrees of latitude up to 40 degrees. At and beyond 40 degrees latitude, add 20 degrees of tilt to the latitude number. The above is the general thumb rule people follow for solar PV panel installation. Consequently, most installations have the solar panels facing south to catch the maximum amount of sunlight.

Researchers at the Pecan Street Research Institute have discovered ways to additionally fine-tune the positioning and tilt of the solar panels to extract somewhat more power. During their research on impact of residential solar power on the power grid, they discovered that if the solar panels faced west rather than the customary south, they could generate about 2% more power.

So long, homeowners, utilities and architects believed that in the northern hemisphere, solar panels directed south would receive the maximum exposure from the sun. However, when studying home installations in Austin, Texas, Pecan Street researchers found that this was not true. In fact, they noticed south-facing panels generating less energy. They found west-facing panels generated more power in the afternoon, when the energy demand peaked.

As energy demand peaks, a typical home in Austin using solar panels reduces its reliance on the power grid by as much as 54%. However, for homes with west-facing panels, this number shot up to 65% – a significant power saving. Therefore, by merely shifting the angle, you may be able to achieve significant gain in solar power generation.

High Efficiency Hybrid Solar Cells

Normally, a modern silicon solar cell exhibits a maximum theoretical efficiency of about 33.7 percent. A majority of the sunlight falling on the solar cell – more than 66 percent – is not converted to electricity and is simply wasted in heating up the cell. Now, a new type of solar cells may be able to boost this efficiency to 95 percent or more.

The University of Cambridge Cavendish Laboratories is researching on a new type of high-efficiency hybrid solar cell. The UK researchers are using an organic formulation to put in as a layer on top of a standard silicon solar cell. This layer will help the solar cell to reach its target of the hard-to-believe 100 percent efficiency.

The top layer of special organic formulation coating on the solar cell helps to absorb high-energy light and produce pairs of triplets. Inorganic solar cells underneath can efficiently absorb these triplets. Generally, the cells cannot convert the high-energy radiation into electricity and these radiations only serve to heat up the solar cells. The organic film on top of the solar cells converts the wasted energy into a form that the underlying solar cell can turn into useful electricity.

With an increase in efficiency brought about by the Cavendish Laboratory hybrid approach, solar energy harvesting farms can be reduced in size significantly, while still producing the same amount of electricity.

According to Maxim Tabachnyk, Scholar, and Akshay Rao, research fellow at Gates Cambridge, and other members of the Cavendish Laboratory at the University, they have developed a film to convert wasted energy into useful form. The traditional solar cell is unable to convert high-energy light and wastes it as heat because of the fundamental limit of the solar cell’s power conversion efficiency.

The researchers coated the silicon solar cells with a special organic layer. This layer functions to distribute the energy of the incoming high-energy photons into two triplet excitons that in turn transfer their electrons on to the silicon cells.

The researchers had to first characterize the ultra-fast processes occurring at the organic/inorganic interface. For this, they directed ultra-short laser pulses into organic pentacene and studied the effect with laser spectroscopy. By following the transfer of energy taking place within a femtosecond (a billionth of a billionth of a second), they confirmed the presence of two electrons for each high-energy photon. Normally, only one electron is generated per photon.

After proving the concept that each high-energy photon can generate two electrons, the researchers had to find an alternative candidate to replace pentacene, which is not a suitable candidate to produce electrons suitable for silicon to absorb. They have now found a suitable organic material that can produce electrons with excitation higher than the band gap or the minimum absorption energy of silicon. The organic material is cheap and can be printed or even sprayed on as ink on top of traditional silicon solar cells.

According to Tabachnyk, normal solar cells harvest only the bright single-spin excitation electrons produced by the photons. The organic layer extends the ability of the cells by allowing them to harvest additional electrons from high-energy photons producing dark spin-triplet excitations.

Can a Solar Cell Store Its Own Power?

Can a Solar Cell Store Its Own Power?

Researchers at Ohio State University have invented a device that looks like a solar cell but has the ability to store the power it generates. The patent-pending device is the world’s first solar battery. On October 3, 2014, the researchers reported in the journal – Nature Communication – that they have succeeded in combining a solar cell and a battery into a single hybrid device.

The innovation is a special solar panel in the form of a mesh that allows entry of air into the battery. Another unique process allows electrons to be transferred between the solar panel and the electrodes of the battery. Light and oxygen entering the device enable chemical reactions to charge the battery.

According to Yiying Wu, Professor of chemistry and biochemistry at the Ohio State University, they will license the new solar battery to industry. Wu expects that the solar battery will tame the costs of renewable energy.

A solar panel is typically used to capture light for converting it to electricity, which is then stored in a cheap battery for later use. By integrating the two functions into a single device, installation becomes simpler and costs go down. The new solar battery may typically bring down the costs by about 25 percent.

The invention also has another advantage. The long interconnections between solar panels and its battery introduce ohmic resistance that reduces the solar energy efficiency because of heat generation when charging. Typically, about 20 percent of the electricity generated by the solar cells is wasted as heat when charging the battery. With the new design, nearly all the electricity generated reaches the battery.

Wu and his students have also developed a high-efficiency battery for use with their solar cells. An earlier designed battery, invented by Wu and his research team, won them the 2014 clean energy prize of $100,000 from the US Department of Energy. The researchers have created a technology spinoff – KAir Energy Systems, LLC – to develop the battery.

The high-efficiency battery is air-powered, meaning it breathes in air when discharging and breathes out when charging. The battery discharges by the chemical reaction of potassium and oxygen. The researchers faced a formidable challenge when trying to combine a solar panel with the KAir type of battery. Typical solar cells are solid panels of semiconductor material and this would prevent air from entering the battery.

Wu and his research team had to redesign the solar panel to make it permeable. They did this by using titanium gauze, a flexible fabric. They grew vertical rods of titanium dioxide on the fabric, similar to blades of grass growing on soil. The rods capture sunlight, while air passes freely through them and the gauze.

Normally, interconnecting a solar cell and a battery requires four electrodes – two on the solar panel and two on the battery. The hybrid design of the researchers has reduced the number of electrodes required to three.

The mesh in the solar panel forms the first electrode. Under this, a thin sheet of porous carbon forms the second electrode, while a lithium plate forms the third. Layers of electrolyte sandwiched between the electrodes forms the battery to store electricity.

Solar Energy in China: Here Comes the Sun

Growing demand for renewable energy sources has skyrocketed all over the world, but no where is this more evident than in China.

Take a look at the city of Rizhao where miles of dark tubing cover the roofs of apartment buildings and private homes. The reason? Using solar powered hot water heaters is mandatory in Rizhao. In fact, due to requirements such as this one, China has become the largest producer (and consumer of) solar hot-water heaters. Rizhao’s commitment to solar energy is deep: it has pledged to become the very first city in China to become carbon-neutral.

The good news for all of us is that the surge in solar panel requirements has created more supply, and thus lower pricing for all of us. The lower prices help make solar energy more affordable even here in the US.

As new panels are shipped to us, we will be passing on the new lowered prices to our customers. West Florida Components has just lowered our prices on all new solar panels by an average of 16%. Good news for all of us!