The power of the sun is immense compared to the global energy demand today. Estimates say that the energy consumption of the world in one year is less than energy provided by the sun in just one hour! With such immense potential, the growth of solar energy has been rather slow due to a few critical reasons. Solar is still not cost effective as the technology to capture, convert & store solar energy is still developing.
Theoretically 70 % of all the solar energy striking the solar panels can be converted to electricity. Although, the commercial panels available today have an efficiency of 15 %. The reason for this drop in performance is due to the losses that occur due to excessive heat, reflections falling on the panels or shading on the solar cells. A theoretical efficiency of 60 % can be achieved by converting the solar energy that heats up the panels into electricity instead .
Some important and recent developments in Solar technology are discussed here.
Concentrating Solar Photovoltaic
Maximizing solar energy to produce more power from solar cells is the principle of concentrating solar photovoltaics (CPV). Using mirrors arranged in the form of a parabolic trough or using Fresnel lenses, sunlight can be focused on a smaller area of solar cells to maximize power generation. Such a solar panel technology improves the conversion efficiency of solar energy into electricity. The technology has the potential to generate power 100 times more than the conventional cells generate today. These panels however require a tracking mechanism to capture the direct radiation of the sun at a low angle of incidence. As these solar panels require lesser number of cells, high efficiency multi-junction solar cells (mostly used in space applications) can be used to maximize power generation per unit area. Using such cells with a dual tracking system, a cell efficiency of upto 40 % can be achieved.
The concentrating solar photovoltaic industry is rapidly gaining momentum in the market. A 200 % growth is expected per annum globally, infusing 1 GigaWatt of power generation every year by 2015 .
Diamond Film Based Solar Cells
Diamond films made up of tiny microscopic diamond crystals can behave as solar cells reaching an efficiency of up to 50 %. These films absorb heat instead of visible light to produce electricity. This phenomenon is known as thermionic emissions & no other material other than diamond is better at it. A reflective dish would be required to focus sunlight onto a combination of two diamond films separated by a very thin layer of vacuum to produce high energy electrons which contribute to generating electricity. Unlike silicon solar cells that degrade after 10 years, diamond film based cells can withstand high levels of radiation & have a very slow degradation rate. Also, the diamond film cells can withstand high temperature without any loss in efficiency, which affects the performance of conventional solar cells. Although the technology sounds expensive, at a bulk manufacturing level, the material could be made at $1 per square centimetre. The technology is at a Research & Development phase, but holds great promise to greatly improvise solar panel technology .
Solar Cells That Work at Night
It is a well known fact that solar technology is based on the energy provided by the sun in the visible spectrum, but with recent developments in nano scale light sensitive antennae, solar panels could function even at night ! Solar arrays of many tiny antennae could bring up the solar panel efficiency up to 46 %. These solar cell antennae rely on infrared energy from the sun to generate power. More than half of the solar radiation striking the earth belongs to the infrared band & during the night time, the earth emits infrared energy absorbed during the day, which can be utilized by the antennae. To build this kind of a solar panel technology, which can absorb both the visible and infrared part of the spectrum; multiple layers of antennae are fabricated on a silicon wafer. The difficulty faced with this technology was converting the energy produced by the cells into usable electricity, but with improvements in modern day silicon diodes, these barriers have been broken down. With successful laboratory testing & a commercial rollout sometime soon, such a solar panel technology could definitely increase overall power efficiency of solar panels & adoption rates of solar energy along with it .
Light Splitting Solar Panels
Silicon cells embedded in the solar panels today can absorb only the long wave radiation emitted by the sun. This leaves the short wave radiation of the solar spectrum unused. Using dichromatic mirrors, the latest solar panel technology splits the white light of the sun into short wave and long wave radiation. As different semiconductor material respond to light of different wavelengths, the short wave radiation is routed to gallium or indium based solar cells for power generation. While the long wave radiation is utilized by silicon based solar cells. Using this solar panel technology, an efficiency of 40 % has been achieved during the research phase. The cost per watt of solar power generation can drop down to less than U.S $3, with the use of this technology .
Light splitting solar panels
Hybrid Solar Panel
The conventional solar panels today made of silicon cells have low conversion efficiency as most of the solar energy received by the panels is dissipated as heat. A hybrid solar panel consists of a solar panel to generate electricity and a thermo electric layer which convert the heat of the panels to electricity as well. The thermo electric layer consists of a thermo electric generator which runs on the principle of Seebeck effect (direct conversion of temperature difference into voltage) to produce electricity. The hybrid solar panel also consists of a hot water module which reduces the temperature of the solar panel for better efficiency & also provides a temperature gradient for the thermo electric generator to operate. The waste heat absorbed by the water layer heats up the water & can additionally be utilized for domestic or commercial usage. The payback time for conventional solar power is high, making it an unattractive investment today. Using hybrid solar panels, the payback for solar power will reduce as the overall energy utilization factor of the solar panels increases.