After winning the Dutch Clean Tech Challenge, Willem Kesterloo, Koon Hooning (MSc students of LSC team) and Gijs van Vrede, all students from Delft University of Technology, have won the international CleanTech Challenge 2013 for their ‘Power Window’ concept. They scooped a £10,000 prize to develop their idea for coated windows that produce clean electricity. Judges were impressed by Power Window’s unique method of combining three technologies based on luminescence, fibre optics and photovoltaics. The CleanTech Challenge is a business plan competition co-run by London Business School and University College London. 151 student teams from around the world formed teams and developed their clean technology business ideas through a 3-stage competition with participants receiving guidance, feedback and mentorship from industry professionals. Apparently the power window concept plus our newly discovered luminescent materials are an unbeatable combination? And of course, Koen, Willem and Gijs acted most professionally. Well done!

For more on this visit www.cleantechnologychallenge.com

The Dutch CleanTech Challenge is a competition for entrepreneurial students throughout the country. The CleanTech Challenge (CTC) was firstly organized by the London Business School in 2009. The Dutch CTC is hosted by Yes!Delft Students, the Delft Energy Club and the Financial Study Association Rotterdam and encourages student teams with interdisciplinary backgrounds to develop and pitch their concepts for a sustainable start-up. Koen Hooning, Willem Kesteloo (MSc students of LSC team) en Gijs van Vrede won 3000 euro’s and travel to London to participate in the Global Cleantech Finals organized by the London Business School.

F.l.t.r.: Hans Hellendoorn (TU Delft), Hans van Happen (Cofely), Venugopal Prasanth, Lourens Meijer, Jan-Willem Wiegman, Klaas van der Werff (UfD), Han Blokland (Cofely).

Our former master student Jan-Willem Wiegman was elected today with the third price of the Cofely -TUDelft Energy Efficiency Award. In this award TUDelft master students compete for the brightest idea that can result in energy saving, CO2 reduction or increase the use of sustainable energy sources. He received the 2500 euro award for his master thesis work on Luminescent Solar Concentrators. Congratulations Jan-Willem!

A strong indication that subsurface information can be obtained using our trillion-frames-per-second camera, comes from the movie below, showing the inside of the applicant right arm as a function of time from 0 to 70 picoseconds after pulsed 100 femtosecond laser excitation with 750 nm light. While in the first 10 picosecond no veins can be seen, they show up clearly after about 20 ps. At later times more veins located deeper appear and broaden due to increased blurring as light scattering becomes more and more dominant.

Below are selected movie still frames at specific times 7 picoseconds apart. Click here for more.

Windows and glazed facades of office blocks and houses can be used to generate electricity if they are used as luminescent solar concentrators. This entails applying a thin layer (for example a foil or coating) of luminescent material to the windows, with narrow solar cells at the perimeters. The luminescent layer absorbs sunlight and guides it to the solar cells at the perimeter, where it is converted into electricity. This enables a large surface area of sunlight to be concentrated on a narrow strip of solar cells.

The new stained glass

Luminescent solar concentrators are capable of generating dozens of watts per square metre. The exact amount of power produced by the windows depends on the colour and quality of the light-emitting layer and the performance of the solar cells. Wiegman’s research shows for the first time the relationship between the colour of the film or coating and the maximum amount of power. A transparent film produces a maximum of 20 watts per square metre, which is an efficiency of 2%. To power your computer you would need a window measuring 4 square metres. The efficiency increases if the film is able to absorb more light particles. This can be achieved by using a foil that absorbs light particles from a certain part of the solar spectrum. A foil that mainly absorbs the blue, violet and green light particles will give the window a red colour. Another option is to use a foil that absorbs all the colours of the solar spectrum equally. This would give the window a grey tint. Both the red and the grey film have an efficiency of 9%, which is comparable to the efficiency of flexible solar cells.

Wiegman’s research has also shown the importance of a smooth film surface for the efficient transport of light particles to the perimeter of the window as they are then not impeded by scattering between the film and the window surface. The research into power-generating windows is in keeping with the European ambition to make buildings as energy neutral as possible. Luminescent solar concentrators are a good way of producing cheap solar energy.

More information:

Erik van der Kolk, researcher in Radiation Detection & Medical Imaging, Faculty of Applied Sciences, TU Delft. 015 278 3464, e.vanderkolk@tudelft.nl.

Ineke Boneschansker, science information officer at TU Delft. 015 278 8499, i.boneschansker@tudelft.nl.

Publication: “Building integrated thin film luminescent solar concentrators”, Solar Energy Materials and Solar Cells, Volume 103, August 2012, pages 41–47.

Nothing is faster than light, yet we managed to see light travel millimeter by millimeter with a one-trillion-frames-per-second ultra high speed video camera build from a femto second laser and a streak camera. The imaging technique, devised by MIT researcher Raskar, may be useful in medical imaging with light.

Cheap, fast and easy visualization of breast or brain tissue with light within the near infrared (NIR) transparency window (600-1000 nm), is a holy grail in medical imaging because it does not depend on harmful radiation, radioactive substances, or bulky instrumentation. The clinical value of NIR imaging has so far been limited due to the strong inelastic scattering of light in tissue that causes serious image blurring. A challenging solution to the scattering problem is the use of pulsed light sources and time resolved detection of transmitted light because in that case only unscattered photons that go straight can be selected. The bottleneck of this time-of-flight or time-gated approach has been a limited temporal resolution (>100 pico seconds) and a too poor sensitivity.

We have constructed a one-trillion-frames-per-second video camera based on a streak camera and a femto second laser, that combines a 100 times higher time resolution (~1 ps) and photon counting sensitivity. In the movie below it is explained that the time-of-flight camera can fruitfully be used to image objects in strongly scattering media, much better than can be done with continuous laser light. We are developing this time-of-flight camera further by optimizing it for NIR optical imaging in order to (i) better understand light transport in strongly scattering media and (ii) to perform 2D and 3D image reconstruction of realistic tissue equivalent phantoms.

Imaging the speed of light

Nothing is faster than light, yet we managed to see light travel millimeter by millimeter with a one-trillion-frames-per-second ultra high speed video camera build from a femto second laser and a streak camera. The imaging technique, devised by MIT researcher Raskar, can have impact in applications such as diffuse optical imaging or 3D surface imaging.

Below the camera films with a picosecond time resolution how a femto second laser pulse passes through a strongly scattering polyoxymethylene sample as function of time. It shows the principle of the time-of-flight imaging approach: light that arrives first has travelled straight through the phantom, while light that arrives later has scattered and therefore exits delayed and at different positions. The movie clearly shows that the position and size of the SS cylinders are seen much more clear in the first 10 or 100 ps compared to longer time slots or continuous wave illumination.

Picosecond time-of-flight camera: 3D surface imaging

Nothing is faster than light, yet we managed to see light travel millimeter by millimeter with a one-trillion-frames-per-second ultra high speed video camera build from a femto second laser and a streak camera. The imaging technique, devised by MIT researcher Raskar, can be applied as a time-of-flight camera to do 3D surface imaging. Below the camera films with a picosecond time resolution how a femto second laser pulse (in the form of a expanding spherical shell) passes over a my face. A z-coordinate can be added to the xy-data by making use of the time resolved data.