Exploring Renewable Energy Technology, November 2017

By Vernon Trollinger, November 9, 2017, Energy Efficiency, Green, Home Improvement, News

Welcome to Exploring Renewable Energy Technology from Bounce Energy! Because the ERCOT portion of Texas can be thought of as a “walled garden,” renewable energy sources in Texas now make up a significant portion of the energy supply mix. It’s also a dynamic technology with new innovations, discoveries, and issues arising every week. Each month, we will examine the latest news in the industry to better understand what (if any) changes might come to the Texas energy supply.

Exploring Renewable Energy Technology, November 2017 | Bounce Energy Blog

Solar Windows —Better Performance from More Transparency

It’s not surprising that the last thing you want on a solar panel is glass that’s prone to glare after it’s been out in the elements for a few years. Even with anti-reflective coatings, the problem of glare reduces the solar panel’s efficiency because the glass reflects light away instead of trapping it. Glare can also become a real problem for neighbors, and when solar arrays are installed at airports, glare hazards from solar panels can blind pilots flying incoming planes.

However, what if you could make solar panels with glass that was designed to be highly transparent — if not practically invisible? Researchers at Brookhaven National Laboratory discovered a method for reducing the reflection of light (and therefore, glare) when it enters a piece of glass.

When light enters glass, it must bend (refract) to pass through. When there’s too much refraction a portion of the light gets reflected out. To even out the path, researchers created a polymer template and used it to etch a pattern of nanoscale “cones” into the glass. The result was that the pattern reduced reflections from the front to the back of the glass to less than 0.2% for the whole visible and near-infrared spectrum (450-2,500 nm). When applied to solar cells, this nanotexture glass generated the same amount of electricity as if they didn’t have any glass on them at all.

Because only small 10 cm circles of the glass can be made, the technology is still in its infancy. But it’s hoped that commercial investors might help finance its development.

Currently under development in Michigan, researchers at Michigan State University have been hard at work on the transparent solar cell. According to their estimates, there’s around 5 to 7 billion square meters of glass surface in the U.S. and covering that with transparent solar could generate about 40% of the U.S. electricity demand.

Regular solar cells absorb mainly the visible spectrum of sunlight. Transparent solar cells use organic molecules to harvest invisible wavelengths of sunlight, ultra violet and near-infrared. Since the visible light isn’t being captured, the cell is transparent and perfect for being placed on a window. Made of thin plastic, it can be used on all sorts of window-application and might even be used for retrofitting existing windows. Though efficiency is still only 5% (compared to regular solar which averages 18%), work in transparent solar is only five years old.

Exploring Renewable Energy Technology, November 2017 | Bounce Energy Blog

Generating Electricity Via Evaporation

Biophysicist Ozgur Sahin found a way to turn the process of evaporation into a renewable source of energy—all powered by changes in humidity levels in the air. The technology uses water-absorbing spores from the soil, harmless bacterium B. subtilis. The spores expand and contract as the humidity rises and falls. Sahin built an “engine” by placing the spores on plastic strips. When the spores do their expanding and contracting, they cause the strips to move by lengthening or shortening. The amount of movement is actually quite startling and is used to open and close shutters that control the flow of humidity around the strips. This movement can also be mechanically connected to a generator.

Sahin calculates that by using lakes and rivers as sites for evaporation energy harvesting, there is the potential to generate up to 325 GW of electrical power.

The added benefit is that these evaporation harvesters slow down evaporation of the water — which is great if the harvester is situated in a modest-sized reservoir used to collect water for irrigation. Slowing down evaporation in bodies of water, however, could change regional climate by affecting the air circulation.

One possible application site could be municipal water treatment plants which often use large settlement ponds or lagoons in the sewage treatment process.

Exploring Renewable Energy Technology, November 2017 | Bounce Energy Blog

Hot Pavements Pave the Way to Clean Power

A thermoelectric generator (TEG) generates an electric current directly by converting the difference between a cold side and hot side into electrical energy. That is, a thermoelectric module is made of a positively charged semiconductor on one side and a negative semiconductor on the other. An electric current will flow when there is a thermal difference between two sides —the hot side and the cold side. TEGS are used in all sorts situations where there is plenty of waste heat, such as vehicles or in steam generating plants.

In Texas, there are plenty of folks that consider summer’s high temperatures as “waste heat”, particularly while walking across broiling parking lots on scorching, sunny days. University of Texas at San Antonio professor Samer Dessouky recently received a $298,000 grant to try an put some of Texas’s summer waste heat to work. Professor Dessouky and his team are developing a technology that will enable them to convert electricity using TEGs by embedding them in paved surfaces. That means freeways, airport runways, and parking lots could become valuable sources for renewable energy.

The TEGs will work by using the temperature differential between the pavement surface and the temperature in the soil at the pavement shoulder. Obviously, larger paved areas stand the chance to generate the most electricity. However, because heating can be uneven, Dessouky’s team is interested primarily in paved areas that concentrate the most heat. It’s estimated that a single 64mm × 64-mm TEG can generate .01 watt continuously over an 8 hour period. Because TEGs can be wired in parallel like solar cells so that their outputs add together, it’s likely that multiple TEGs can put out higher voltage for an equally sustained period.

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