Researchers at National University of Singapore and Nanyang Technological University, Singapore, have demonstrated the use of nanodots to increase the efficiency of solar cells. In today's commercial solar cells between 17% to 19% of the photons hitting the cells get converted into electricity. With the advent of large giga scale solar projects an increase in efficiency of a few percentage points could lead to huge gains for the industry. The team from Singapore attacked the problem using an effect known as upconversion. Our sun generates an enormous amount of energy in the form of photons of light. Solar Cells absorb the energy from photons which have a certain threshold of energy and create electrons or electricity from them. However, not all photons coming from our sun have the same energy. The lower energy photons are not absorbed by the solar cells and are lost. Researchers were able to combine two low energy photons to produce a single high energy photons which could then be absorbed by the solar cell to generate electricity. The team used a structure made of titanium oxide called an inverse opal (see above). The inverse opal frame is filled with an arrangement of air pores roughly half a micrometer across. Nanospheres, about 30 nanometers in diameter converted lower energy photons (NIR - near infrared radiation) to higher energy photons of visible light. The opal frame is coated with light sensitive cadmium selenide quantum dots which absorb the photons to release electrons which are then transmitted through the titanium oxide frame. The researchers tested the device using laser light with a wavelength of 980 nanometers. This wavelength is not normally absorbed by cadmium selenide quantum dots. The experiment yielded much higher electric current as compare to devices not using the upconversion material. The researchers believe their upconversion based device could yield a significant competitive advantage over conventional silicon solar cells. More on this is available on the Lab's website. Visit our website at Ampericon.com to know more about solar and other renewable energy products and to check out a wide selection of white papers. You could also mail us at jon@ampericon.com.
The widely distributed nature of renewable energy sources has led to a burgeoning demand for grid scale energy storage technology. Such technology enables electricity to be fed easily and efficiently into centralized power grids. SolarReserve, a California based, private equity backed startup is planning to leap ahead of the competition with its molten salt storage technique.
SolarReserve's 110-megawatt concentrated solar power (CSP) project known as Crescent Dunes launches in mid 2014 in the Nevada desert. SolarReserve licensed its technology from the aerospace firm Rocketdyne. They use thousands of mirrors mounted on a tower to focus sunlight onto a single point creating enormous heat. This heat is used to generate steam that causes the electricity producing turbine to spin.
SolarReserve has a 25 year PPA (power purchase agreement) with the local utility company Nevada Energy. Even though competitor's like BrightSource use tower based designs, they don't have an energy storage component in their projects. The SolarReserve project will be the first commercial-scale CSP project with storage.
However, BrightSource Ivanpah CSP project in California will be the world's largest CSP plant, toppling the current title holder the Shams 1 CSP plant in Abu Dhabhi.
The race to commercialize grid scale energy storage technology is highly competitive with companies working out of Spain, Germany, China and Israel, but US technology is leading the race. The alternative to molten salt based storage is PV with battery storage. However, that technology is not very feasible for large scale storage. So far in the energy storage wars, molten salt and SolarReserve are leading the charge.
Visit our website at Ampericon.com to know more about solar and other renewable energy products and to check out a wide selection of white papers. You could also mail us at jon@ampericon.com.