Monday, January 4, 2016

Solar power-New approach to improve efficiency of trapping solar energy

Search for alternate energy to fossil fuels has been going on since last 5 decades and solar energy became most promising during the last few years because of the encouraging trend seen vis-a-vis the cost of the solar panels which form the core of the technology. To day the panel cost is relatively low compared to the cost of the frame structure needed to mount these panels. Other sources like wind, ocean waves, geothermal etc are also viable candidates for a significant slice of the emerging market for alternate energy generating systems but the cost of generation and investment in creating the necessary infrastructure to install them are relatively high. The cost of energy produced by non-conventional sources was never comparable to traditional power generated by thermal, hydro electrical or nuclear reactors. It is here that solar energy is making enormous strides and the recent break through achieved by researchers in the US offers a real chance to make the solar energy affordable to all. Here is a take on this new development. 

"Solar panels placed flat on a rooftop are most effective at harnessing solar energy when the sun is close to directly overhead, but quickly lose their efficiency as the angle of the sun's rays hitting the panel increases – during the mornings, evenings, in the cooler months and in locations far from the equator. It is exactly in these situations that the researcher's vertical solar modules provided the biggest boosts in power output. After exploring a variety of possible 3D configurations using a computer algorithm and testing them under a range of latitudes, seasons and weather with specially developed analytic software, the team built three different individual 3D modules and tested them on the MIT lab building roof for several weeks. The results showed a boost in power output ranging from double to more than 20 times that of fixed flat solar panels with the same base area. By going vertical and collecting more sunlight when the sun is closer to the horizon, the team's 3D modules were able to generate a more uniform output over time. This uniformity extended over the course of each day, the seasons of a year, and even when accounting for blockage from clouds and shadows. The researchers say this increase in uniformity could overcome one of the biggest hurdles facing solar energy – predictability of electricity supply that currently makes it difficult to integrate solar power sources into the grid. They add that this uniformity, as well as the much higher energy output for a given area, would help offset the increased cost of the 3D modules, which are higher per the amount of energy generated when compared to conventional flat solar panels. While the team's computer modeling showed complex shapes – such as a cube with each face dimpled inward – would offer a 10 to 15 percent improvement in power output when compared to a simpler cube, these would be difficult to manufacture. In their rooftop tests, the team studied both simpler cube modules as well as more complex accordion-like shapes that could be shipped flat for unfolding on site. This accordion-like tower was the tallest structure the team tested and such a design could be installed in a parking lot to provide a charging station for electric vehicles, according to Jeffrey Grossman, the senior author of the study and the Carl Richard Soderberg Career Development Associate Professor of Power Engineering at MIT. Grossman and his colleagues believe that with the fall in the cost of solar cells in recent years - to the point where they have become less expensive than their supporting structures and the outlay for the land upon which they are placed - makes it an ideal time to examine the benefits of different solar cell configurations. "Even 10 years ago, this idea wouldn't have been economically justified because the modules cost so much," Grossman says. But now, he adds, "the cost for silicon cells is a fraction of the total cost, a trend that will continue downward in the near future." Buoyed by the success of the tests on the individual 3D modules, the team now plans to study a collection of solar towers that will enable them to examine the effects that one tower's shadow will have on another as the sun moves across the sky over the course of a day. While the team believes its 3D solar cells could offer big advantages in flat-rooftop installations or urban environments where space is limited, they say they could also be used in larger-scale applications, such as solar farms, once a configuration that minimizes the shading effects between towers has been developed."

One of the severe limitations for exploiting the solar light is the vast land area required to install the panels and the nonuniform generation pattern during the course of a day or through out the life of the plant. This is sought to be addressed by the new findings that by altering the configuration of the panels facing the sun into a 3D structure, efficiency of absorption of solar rays can be boosted very significantly, thus promising a further slide down in the cost of power generated. Though this is an exciting development, its commercial feasibility will have to be worked out by building large scale plants and the assessing the cost of power so produced. The researchers have a point when they say that the supporting structure on which the 3D panels are to be arranged will determine the economic feasibility of adopting these modified designs in future. Still it has to be conceded that 3D system may become the only option in many countries where open lands for installing conventional solar plants are not easily available. With India undertaking a stupendous program for expanding the solar energy system in the country for phasing out its highly polluting coal based power plants and uncertain rain falls that drive the hydroelectric power sector, the new 3D solar plants may be a big boon.   


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