Tag Archives: Alternative Energy

Five New Advancements in Solar Cells

The earth receives a huge amount of sunlight every hour. Converted to electricity, this would amount to 52 PW/hr. This is more than ten times the entire amount of electricity produced per hour by China in 2013. In the same year, top countries of the world together produced only 16 PW/hr. of electricity. As this is much less than the actual potential of generation of electricity from the solar energy falling on the planet earth, several countries are actively engaged on research and development on photovoltaic cells.

There have been several breakthroughs in photovoltaic cell technology. For instance, early cells were very expensive and inefficient—almost $1800/watt and 4% respectively. Costs have now come down to $0.75/watt, while the efficiency has increased to 40%. Since, then, there have been several other breakthroughs in the solar cell domain.

Printable Solar Cells

At the New Jersey Institute of Technology (NJIT), researchers have developed a printable solar cell, and they can print or paint this on a surface. According to the lead researcher Dr. Mitra, they are aiming for printable sheets of solar cells that any home-based inkjet printer will be able to print and place on the wall, roof, or billboard to generate power. The printable cells are made of carbon nanotubes 50,000 times smaller than a human hair.

All-Carbon Flexible Solar Cells

Scientists at the Stanford University have made these flexible solar cells from a special form of carbon called graphene. According to Zhenan Bao, one of the team and a professor of chemical engineering at Stanford, the flexible carbon solar cells can be coated on to the surface of cars, windows, or buildings for generating electricity.
By replacing expensive materials when manufacturing conventional solar cells, the all-carbon solar cell is expected to make the cells much cheaper.

Transparent Solar Cells

At the Michigan State University, a team of researchers has made solar cells that appear transparent to the visible spectrum of sunlight. Rather, these non-intrusive solar cells convert light beyond the visible spectrum to electricity. Therefore, these can be used on smartphones, on windowpanes of buildings, or in windshields of vehicles without impeding their performance.

According to MSU assistant professor Richard Lunt, their aim is to produce solar harvesting surfaces that are invisible. However, the present efficiency of these cells is a mere 1%, as they are in their initial stages.

Wearable Ultra-Thin Solar Cells

In South Korea, at the Gwangju Institute of Science and Technology, scientists have used gallium arsenide to develop solar cells with a thickness of just one micrometer, more than 100 times thinner than human hair. According to Jongho Lee, an engineer at the institute, such thin cells can be integrated into fabric or glass frames to power the next wave of wearable electronics.

To create such thin cells, the scientists removed extra adhesives from the traditional cells, and cold-welded them on flexible substrates at 170°C.

Solar Cells with 100% Efficiency

By extracting all the energy from excitons, researchers at the University of Cambridge have found methods of making solar cells that are more efficient. Such a hybrid cell combines organic material and inorganic material into high conversion efficiency.

How Do Wind Turbines Work?

Wind turbines generate electricity from moving winds. You can see them in large numbers on wind farms both onshore and offshore. The blowing wind turns their blades, and rotates the shaft on which the blades are mounted. The shaft in turn, operates an electric generator and the resulting electric output is sometimes stored in a battery. A swarm of wind turbines can generate a substantial amount of energy. Wind turbines are often called a renewable source of energy, as they generate power from natural renewable sources, and do not consume fossil fuel, a source that cannot be replenished.

Inside the wind turbine, there are several control systems at work. These include its ability to turn the face of the turbine into the wind, called yawing, and its ability to control the angle of its blades, called pitch. Yawing and pitch extract the maximum amount of power from the blades rotating in the wind and require motors and controls. However, the yawing of a wind tower may actually twist the cables inside. The wind turbine usually has electronic intelligence built inside to untwist the cables.

The wind actually propels the blades, which are designed using the laws of physics and vectors to extract the maximum from the wind driving them. Speed analysis shows the maximum efficiency the wind turbine can achieve is about 59%. The laws of physics, especially Betz’s limit prevents the wind turbine from achieving efficiencies any higher.

As mentioned earlier, the main parts of a wind turbine are the blades mounted on a shaft. As the blades turn with the wind, the shaft rotates and spins a generator to make electricity. Most designs of wind turbines use electronic controls to generate the 60 Hz AC sine wave, although there are wind turbines that generate DC as well.

Typically, a doubly-fed induction generator is used to generate three-phase power. As this requires capacitors and a DC link, workers need to monitor the systems periodically to prevent failure of capacitors. Most of the control is similar to that used for controlling bidirectional motors, using IGBTs, and rectifier diodes in a full bridge arrangement. These components are rather large, considering the voltage generated is nearly 690 volts, and the power is in megawatts. Transformers step up the voltage from the generator to the grid power line, and there is built-in protection to limit the spikes as the speed of the wind increases.

The rotation speeds for wind turbine blades are 5-20 rpm, while a generator needs to rotate at speeds between 750 and 3600 rpm to generate power. Therefore, a gearbox in between translates the speeds. When maintenance time comes around, a combination of yawing and proper pitch is used to stop the rotation. Workers then insert pins into the shaft, locking the blades to prevent them from spinning.

Workers servicing and maintaining the blades have to dangle from ropes hundreds of feet above the ground in the air. Other parts, being within the tower, can be maintained more easily. In general, the maintenance and servicing for a wind turbine is similar to that required by any other turbine in a power generating station.

Metamaterial Cools Buildings without Using Energy

Engineers at the University of Colorado Boulder have built a metamaterial that can be used to cool structures without drawing on any energy. The material can also cool objects placed in direct sunlight without using water.

A metamaterial is an artificial substance with remarkable properties not possessed by natural substances.

According to Xiabo Yin, an assistant professor at Colorado Boulder and a director of the research, the new metamaterial could be a game changer in the field of radiative cooling technology. Since the technology does not make use of water and electricity, it presents a huge opportunity in the fields of power generation, agriculture, space research, and several other areas.

The metamaterial, which could make for an environmentally friendly and cost-effective technique for cooling homes and industrial applications, has been discussed in the journal Science. Thermoelectric power installations, which need a large amount of water for maintaining the low temperatures of the cold junction could instead make use of this material for cooling purposes. The hybrid material can be fabricated in the form of glass-polymer sheets in thickness of 50 micrometers. It is only marginally thicker than the kitchen aluminum foil and can be manufactured on rolls, making it economically viable for large-scale production.

When placed over an object, the film cools the surface beneath it by reflecting the incident solar energy radiations back. At the same time, the film helps the object lose the heat contained by emitting low frequency infrared radiations. Field demonstrations were conducted at Cave Creek in Arizona and Boulder in Colorado. The tests showed that at both places, the metamaterial had an average radiative cooling power of 110 W/square meters for 72 hours at a stretch. During direct sunlight at noon, the radiative power recorded was 90 W/square meters.

Gang Tan, an associate professor in the Department of Architectural and Civil Engineering of Wyoming University, explains the test results imply that about 20 square meters of the material installed on the roof of a single family home could achieve reasonably good cooling in summer.

Apart from cooling buildings and power plants, the new polymer-glass hybrid material can serve to enhance the efficiency and life of solar panels put up for electricity generation. Intense sunlight tends to damage solar panels. Yin explains that a layer of the material applied to a panel can boost the efficiency by almost 2%.

The cooling power of the material is approximately equal to the electricity produced by a solar panel of the same area. However, while solar cells can operate only during the hours of sunshine, the new material provides radiative cooling at all hours.

The researchers are now waiting for a patent for the new material and the technology. They are also working with the Technology Transfer Office at CU Boulder to look at prospective commercial applications. A potential project in the offing involves the creation of a model cooling-farm in Boulder sometime this year.

The team has been awarded a grant of $3 million for the invention of the metamaterial and the related research projects by the Advanced Research Projects Energy Agency connected with the DOE.

Energy Harvesting – How & Why

What Is Energy Harvesting – Why Is It Needed?

The process of extracting small quantities of energy from one or more natural, inexhaustible sources, accumulation and storage for subsequent use at an affordable cost is called Energy Harvesting. Specially developed electronic devices that enable this task are termed Energy Harvesting Devices.

The world is facing acute energy crisis and global warming, stemming from rapid depletion of the traditional sources of energy such as oil, coal, fossil fuels, etc., which are on the verge of exhaustion. Not only is the global economy nose-diving, but the damage to the environment is also threatening our very existence. Natural calamities like earthquakes, tsunamis, droughts, floods, storms, etc., have become the order of the day. Economic growth is generating a spiraling demand for energy, goading us to tap alternative sources of energy on a war footing. Our very existence on the planet Earth is at stake, and we must find immediate solutions to meet the energy needs for survival.

Alternative Energy Sources Available

There are many, almost inexhaustible, sources of energy in nature. In addition, these energy forms are available almost free, if available close to the place where required. Sources include: Solar Energy, Wind Energy, Tidal Energy, Energy from the waves of the ocean, Bio Energy, Electromagnetic Energy, Chemical Energy, and so on.

Recent Advances in Technology

The sources listed above provide miniscule quantities of energy. The challenge before us is to gather the miniscule amounts and generate meaningful quantities of energy at affordable cost. Until very recently, this has remained an unfulfilled challenge.

Today, research and innovation has resulted in creation of more efficient devices to capture minute amounts of energy from these sources and convert them into electrical energy. Besides, better technology has led to lower power consumption, and hence higher power efficiency. These have been the major propelling factors for better, more efficient energy harvesting techniques, making it a viable solution. These solutions are considered to be more reliable and relatively maintenance free compared to traditional wall sockets, expensive batteries, etc.

Basic Building Blocks of an Energy Harvesting System

An Energy Harvesting System essentially consists of:

a) One or more sources of renewable energy (solar, wind, ocean or other type of energy)
b) An appropriate transducer to capture the energy and to convert it into electrical energy (such as solar cells for use in conjunction with solar power, a windmill for wind power, a turbine for hydro power, etc.)
c) An energy harvesting module to accumulate, store and control electrical power
d) A means of conveying the power to the user application (such as a transmission line)
e) The user application that consumes the power

With advancement in technology, various interface modules are commercially available at affordable prices. Combined with the enhanced awareness of the efficacy of Energy Harvesting, more and more applications and utilities are progressively using alternative sources of energy, which is a definite sign of progress to effectively deal with the global energy crisis.

Optional addition of power conditioning systems like voltage boosters, etc., can enhance the applications, but one must remember that such devices also consume power, which again brings down the efficiency and adds to cost.

Generating Energy: The future of clothing

We think of clothing as something to keep us warm, or as a way to show our individuality and fashion sense. But have you ever thought about your clothing as a source of energy?

Researchers at the University of California at Berkeley are working on a way to embed nanotechnology into clothing to harness energy as we perform our routine daily tasks such as walking and exercising. The nano-electric fibers are so small, they are invisible to the naked eye. One day, researchers believe that clothing embedded with these fibers might generate enough energy to power our mobile devices and keep them fully charged.

That is only one study underway. At Stanford University, researchers there are working on making the actual cloth into conductive material. Their current project involves dipping cotton cloth into conductive ink, baking the coated fabric and then measuring the energy generated and harnessed by the fabric. Researchers believe that future iterations of their work might function as an energy storage device, again probably generating enough energy to power mobile devices.