Upping the solar efficiency

Solar cells are inefficient because they are picky! If an incoming photon has too little energy, the cell won’t absorb it. If a photon has too much, the excess is wasted as heat. No matter what, a silicon solar cell can never generate more than one electron from a single photon. Now, researchers at the Massachusetts Institute of Technology’s Center for Excitonics have published a compelling case that the key to greater solar efficiency might be an organic dye called pentacene.

A photovoltaic cell based on pentacene can generate two electrons from a single photon—more electricity from the same amount of sun. Previous research had accomplished similar tricks using quantum dots (tiny pieces of matter that behave like atoms) and deep-ultraviolet light. In addition to using visible light, the present work has shown that [this process] works very, very effectively in organic materials.

Yes, for now, the pentacene cell works only with an extremely narrow band of visible light. But the team hopes it should be possible to create a pentacene coating for silicon solar cells that boosts the total conversion efficiency from today’s 25 percent to a shade over 30 percent—a significant jump. Of course, it is all theory now. But science debvelops from theory to experiment and we can hope!

A gimmick or more?

Recently when athletes took part at the 37th Paris Marathon, they were doing more than running. They were generating electricity thanks to some innovation from a London based company. As the athletes thumped their feet on 176 special tiles laid on a 25-meter stretch, they generated 4.7 kilowatt-hours of energy, enough to power a five-watt LED bulb for 940 hours, or 40 days electricity!

These special “energy harvesting tiles” work on a hybrid black box technology to convert the energy of a footstep into electricity, which is either stored in a battery or fed directly to devices. A typical tile is made of recycled polymer, with the top surface made from recycled truck tires. A foot stomp that depresses a single tile by five millimeters produces between one and seven watts. These tiles generate electricity with a hybrid solution of mechanisms that include the piezoelectric effect (an electric charge produced when pressure is exerted on crystals such as quartz) and induction, which uses copper coils and magnets.

Using piezolelectrics to generate power has been in since some time, at various places. These come with some challenges. Installing the tiles in the ground is one of the hardest things to do as they have to be very durable, weather resistant and should have high fatigue resistance as well. Also, these tiles could get vandalized. While the technology application need be lauded, we need to ask some critical questions too. Beyond demonstrating the technology, can such innovations help improve the overall energy situation? What is the EROI? Can we compare the cost of materials that go into the making of these tiles to the amount of energy generated? Should we be focussing on such ideas or go for more scalable ones?

Designer atoms and super magnets!

The future of manufacturing depends on a number of technological breakthroughs in robotics, sensors and high-performance computing, to name a few. But nothing will impact how things are made, and what they are capable of, more than the materials manufacturers use to make those things. New materials change both the manufacturing process and the end result. Scientific American has come up with a line up of exciting inventions. Many of them are relevant to the field of energy.

Carmakers, for example, are developing porous polymers and new steel alloys that are stronger and lighter than steel, ostensibly making vehicles both safer and more fuel efficient. And environmentally savvy entrepreneurs are growing fungi-based packing materials to provide a biodegradable alternative to Styrofoam. The Mushroom Packaging from agricultural crop waste—plant stalks and rice and wheat husks—bonded together with mushroom roots (called mycelium) is a biodegradable alternative to petroleum-based plastic foams used in automotive bumpers, doors, roofs, engine bays, trunk liners, dashboards and seats.

Northwestern University and Michigan State University scientists have demonstrated a thermoelectric material that is highly efficient at converting waste heat to electricity. The inefficiency of existing thermoelectric materials has limited their commercial use. The record-setting, environmentally stable formulation is expected to convert 15 to 20 percent of waste heat to useful electricity, enabling greater industrial adoption. Waste-heat recovery systems could be attached, for example, to vehicle tailpipes or could process the exhaust streams from glass- and brick-making factories, refineries, fossil-fuel power plants as well as large transport ships and tankers.

Three University of Chicago chemists have created a new way to assemble what they call “designer atoms” into novel materials with a broad array of potentially useful properties and functions. These designer atoms are nano crystals—tiny crystalline arrays small enough that new quantum phenomena begin to emerge but large enough to provide building blocks for new functional materials and substances that could be useful in harvesting solar energy and delivering quantum computing. Whereas electric motors use magnets to transform electrical energy into mechanical energy, sintered rare earth magnets produce incredibly strong magnetic fields at small sizes, allowing manufacturers to build smaller, lighter motors, according to Electron Energy Corp. The firm has teamed up with University of Delaware researchers to develop a manufacturing process that increases sintered rare earth magnets’ electrical resistivity by at least 30 percent. Their goal is to make magnets with increased electrical resistivity that can reduce motor efficiency losses even when motors operate at high speeds.
Hydrogen fuel cell vehicles could provide clean transportation in the future, but they remain expensive in part because they use the precious metal platinum to facilitate the chemical reactions that produce electricity within the cell. A new method for quickly and cheaply depositing ultrathin layers of platinum might make it practical to reduce the amount of the metal used in fuel-cell catalysts, thereby lowering their cost significantly.

New LED on the block

On Thursday, Philips announced that it has developed the world’s most efficient “warm white” LED lamp. Designed to replace the fluorescent tube lighting that is ubiquitous in offices and industrial facilities, the new TLED (tube-style light emitting diode) has the potential to reduce worldwide energy consumption by more than 7%.

According to a Philips spokesperson, their new prototype tube lighting produces 200 lumens per watt (200 lm/W). And it is expected to cost only slightly more than the equivalent strip lighting set-up (at 100 lm/W). Traditional bulbs only produce 15 lm/W.

But, the arguably more significant accomplishment with Philip’s new TLED is that it produces warm white (~2700K) light, the type of light prehat most people prefer for indoor lighting. An easy way to increase the efficiency of a bulb design is to increase the color temperature. So, the fact that Phillips managed to keep the temperature in this lower range, while still hitting the 200 lm/W rating, is even more impressive.

Globally, building lighting represents 15-19% of total energy consumption and florescent tube lighting accounts for more than half of the lighting market. In the context of Thursday’s announcement – if Philips’s new bulb makes it to market by the summer of 2015, it will have the potential to reduce worldwide energy use by more than 7%.

Can do, but will do??

Mark Jacobson of Stanford University has been a strong proponent of renewable energy. In 2009 he showed how the world could get all its energy from wind, solar and water. He calculated just how many hydroelectric dams, wave-energy systems, wind turbines, solar power plants and rooftop photovoltaic installations the world would need to run itself completely on renewable energy.

This time Jacobson has showed in much finer detail how New York State’s residential, transportation, industrial, and heating and cooling sectors could all be powered by wind, water and sun, or “WWS,” as he calls it. His mix: 40 percent offshore wind (12,700 turbines), 10 percent onshore wind (4,020 turbines), 10 percent concentrated solar panels (387 power plants), 10 percent photovoltaic cells (828 facilities), 6 percent residential solar (five million rooftops), 12 percent government and commercial solar (500,000 rooftops), 5 percent geothermal (36 plants), 5.5 percent hydroelectric (6.6 large facilities), 1 percent tidal energy (2,600 turbines) and 0.5 percent wave energy (1,910 devices).

In the process, New York would reduce power demand by 37 percent, largely because the new energy sources are more efficient than the old ones. To the old doubts about intermittency of renewables, he believes that if you get the [power] transmission grid right you don’t need a whole lot of storage. By combining wind and solar and geothermal and hydroelectric, you can match the power demand. And if you oversize the grid, when you’re producing extra electricity you use it to produce hydrogen [for fuel-cell vehicles and ships as well as some district heating and industrial processes]. You can also spread the peak demand by giving financial incentives!

There may be any number of possibilities, but does that mean there are takers? Especially in a world comfortable with burning fossil fuels!

Data availability the crux to tracking progress: IEA

The International Energy Agency released two reports – “Tracking Clean Energy Progress 2013” and the “Global EV Outlook.” According to these two reports, despite significant gains in renewable power generation, coal technologies still dominate and nuclear power continues to struggle. But, a window of opportunity is opening in the transportation sector. The tracking report reveals analysis shows that the world is not moving quickly enough to meet environmental targets. Key technologies are not being developed. Global research and development investments need to be dramatically increased. The clean-energy transition appears to have stalled.

One of the key findings in the IEA’s Clean Energy Tracking report was that poor quality and availability of data consistently constrains their ability to track and assess progress.  For example, the smart grids category has seen significant movement over the last few years. According to the IEA, demonstration and deployment of smart grid technologies are accelerating. But, data collection efforts on national and international levels are too limited to give a solid picture of the progress made.

In order to meet the energy-related emissions goals, the IEA’s 2^°C Scenario shows renewable power generation growing from 20% to 57% of total generation between 2010 and 2050. Hydropower is the largest contributor, followed by wind, biomass, waste, and solar technologies. This scenario also shows renewables growing to 28% of total generation by 2020. And, these technologies appear to be on track to hit this midterm goal.

According to the IEA, renewables have shows steady market growth over the last decade. Renewable deployment is continuing to spread geographically, with countries including China, India, and Brazil increasing their use of renewables from 45% of total generation in 2010 to 53% in 2011.

Black carbon flows

Black carbon rears its head again! This time it breaks earlier notions of creating a carbon reserve in soil.

A smaller proportion of black carbon created during combustion will remain in soil than have been estimated before. Contrary to previous understanding, burying black carbon in the ground in order to restrain climate change will not create a permanent carbon reserve. Instead, a part of black carbon will dissolve from soil to rivers.

The burning of organic matter creates 40-250 million tons of black carbon every year. Black carbon is formed through the incomplete combustion of organic matter, e.g. in forest fires, slash-and-burn and controlled burning of fields. In the light of new research results, much discussed "bio-carbon" may not be that beneficial in terms of mitigating climate change. In any case, the stability of carbon in soil has been a central factor of bio-carbon applications.

By sampling rivers all around the world, the researchers estimated that the annual amount of black carbon flowing via rivers to the ocean is 27 million tons per year. For this project, water samples were collected from the ten largest rivers in the world. These rivers carry one third of fresh water running to oceans, and their catchment area covers 28% of the whole land area in the world. In addition to the samples used in the river project, the research published in Science was supplemented with samples from many other rivers all over the world. The total number of researched samples was 174.