EXSS at the Royal Society

Dr Ned Ekins-Daukes led a team from Exss which exhibited in this year’s Royal Society Summer Science Exhibition in July

Quantum of Sol: the next generation of solar cells

Description

Quantum of Sol was an exhibit by the Quantum Photovoltaics group from the Department of Physics at Imperial College London. The exhibit was designed to explain to the public the science behind high-efficiency solar cells.

The display contained three hands-on demonstrations arranged sequentially to explain three different aspects of photovoltaics. There was also a backdrop and pull-down banners with graphics and description to explain our work. Furthermore, there was a glass cabinet containing various types of solar cells (including some world-record efficiency cells) so the public could see the different technologies first-hand.

Demo 1. Spectrum splitting

In the first demo, a white light was split by a prism into its broad spectrum, and three different solar cells on a motorised stage could be moved through the colours. A computer touch screen allowed the user to control the stage, and showed whether each cell was producing electricity. This was designed to convey that the solar spectrum is broad, and that different solar cells can absorb different parts of the spectrum.

Demo 2. Multi-junction puzzle

The second demo consisted of a box containing a fluorescent light source. There were slots cut into the box that allowed the public to insert sheets of fluorescent plastic according to the energy of light that the sheets absorbed. If the sheets were inserted in the correct order (high energy to low energy) then all the edges of the sheets lit up. This was used as an aid to explain how multi-junction solar cells are structured to absorb different energies of sunlight in different layers, such that more of the spectrum can be absorbed at an optimal efficiency.

To further help people to understand the more subtle concepts, a computer program allowed people to simulate changing the materials and structure of the solar cell and shows what efficiency this would give.

Demo 3. The concentrator challenge

The third demo involved a game to show how concentrating light onto a solar cell using mirrors and lenses can help to improve the power without much increasing the cost of the system. The participant was given various optical components which they used to focus a white light onto a small cell, and the cell's output current was shown on a computer screen. The best scores were then entered into a raffle to win an iPod Touch.

What worked and what didn't

Demos

The concentrator challenge worked really well! It especially helped to attract school children, but even Fellows of the Royal Society had a try. The opportunity to win an iPod Touch was an attractive selling point!
The multi-junction puzzle was quite a simple demo but was very useful for explaining some of the more tricky physics.

The spectral splitting demo was less successful as the cells could only move very slowly through the spectrum, so people had to stand around and wait for quite a while.

The display cabinet with world-record efficiency cells proved very popular with the more seasoned members of the public and with the Fellows.

Freebies

We had mini luminescent plastic sheets relating to our multi-junction demo to give away that were extremely popular freebies.

Unexpectedly, pens with "Imperial College London" on them proved to be very popular freebies. Badges did well too.

Balloons and bookmarks were not particularly popular with the public.

Scheduling

As well as 6 core team members, 10 other people with some connection to the Quantum Photovoltaics research group helped with the stand. We divided each day into 2-hour slots and had 4 or 5 people manning the stall at all times. This seemed to be just right so that no-one was overloaded but everyone had plenty of chance to interact with the public.

Success of exhibit

We feel the exhibit to have been very successful. In particular, a great variety of visitors came to our stand and we were able to give explanations of our research at several different levels. The concentrator challenge demo was great to get the attention of school kids, but the display cabinet of record-breaking cells inspired a lot of interest among the more scientific visitors and those in industry or research.
On a technical level the stand was also successful, in that none of our demos broke!

Number of people we interacted with

We estimate that we interacted with more than 1000 people over the course of the week. This is based on rough recordings at the end of each session of the number of people who visited our stand.

Value of mentor

Laura Grant gave us plenty of helpful input prior to the exhibition. She proof-read our backdrop to make sure we were targeting the right audience, and gave us ideas to improve the demos. The most valuable thing she did for us however, was to bring a team of sixth formers to visit a week before the exhibition. This gave us the impetus we needed to get our demos up and running, and gave us a great opportunity to try to explain our work and get feedback on our explanatory skills!
Impact on the team

The exhibition had a very positive impact on the team. It took a lot of time, hard work and dedication beforehand but when the week of the exhibition arrived, everyone was extremely geared up and enthusiastic about explaining our research to the outside world. It was also a valuable experience in that it really helped us to explain the context of our research and to learn what questions "normal" people may have about solar energy. We would be interested in doing more outreach work in the future, especially now that our exhibits have been constructed.

Information useful to EPSRC

The £5000 provided by EPSRC was absolutely critical to the success of our stand. It made up just over half of our budget in the end. It would have been very difficult to raise the entire amount via corporate sponsorship alone.