Harvesting Solar Energy - Artificial Leaves

Having had a quick look at solar energy already, one of the key issues is the efficient production of energy from solar cells using widely available materials. Scientists at Harvard University have been addressing this.

The Artificial Leaf 

This carries out the same processes as in nature but it allows for collection of oxygen and more importantly hydrogen which can be used as a fuel. The leaf is made of a silicon wafer: one side produces oxygen and the other produces hydrogen from photosynthesis. The the important break through with this research is that cheap and widely available metals have been used as catalysts in the reaction, instead of platinum which how it was originally achieved (Reece et al, 2011, Science). As it really highlights in the paper, the most important development is the cheap and widely available materials that are used in the process.

Harvard Professor and one of the main authors on the paper, Daniel, Nocera, explains the process in this Horizon clip. 

No external wires or controls are needed, the silicon chip just has to be placed in water. This is what it actually looks like, with some real leaves in the background in case you hadn't seen them before... More information can be found on the MIT News Site

The artificial lead - image from MIT news

'Here comes the sun'

Before university I spent a year working with a chemical engineering company making ink. I was a little disappointed to discover that this did not involve farming squid but instead mixing up various combinations of chemicals. I specialised in conductive inks and by far our the fasting growing demand was for solar cells. This hardly makes me an expert but means I have an interest in the area!

Firstly, some basics. Solar cells (or photovoltaic cells) generate energy by the photovoltaic effect. Light from the sun, made up of photons, hits the semiconductor in the solar cells. This excites electrons in the atoms which make up the semiconductor and releases them from the shell. There is a electrical gradient in the semi conductor which attracts the released electrons which then flow: generating electricity (physics online).

Potential energy - image from Solar Spark

The potential solar energy available is enormous: 120,000 TW per day compared to the global energy use of 15 TW per day (solar spark). However, this is the total sunlight hitting the earth so if we wanted to use it we would have cover the earth in solar cells and have them all work with 100% efficiency. This is not possible but it does demonstrate just how much we could utilise solar energy.

Now back to those squid...

Technology Idea of the Week

"All I've heard from you lot so far is a lot of hot air, so in the interests of climate change: you're fired!"

A classic Lord Sugar quote from the BBC series The Apprentice (top on liners blog). Nice to see a acknowledgement of environmental change as well! Business plan competitions have become quite a major event for entrepreneurs over the last few years and are a great way to get a head start in business, unless of course you make a fool of yourself on The Apprentice. The CleanTech Challenge is a competition run by University College London and London Business School which looks for ideas which provide a "sustainable environmental benefit". So for this weeks tech innovation I am going to look at the 2013 winners of the CleanTech Challenge. 

The Power Window - Delft University of Technology 

• A luminescent foil is placed over a glass window
• The foil absorbs photons of light and scatters them towards the edge of the window 
• Solar panels around the window frame absorb the light and generate electricity
• The students at Delft University of Technology developed a new material which helped improve the efficiency of this process by a factor of five
• For more information check out the Delft TU Website or CleanTech Challenge. There is also an interesting video on the subject, link is posted below. 

A Solar Concentrator developed by MIT, similar to the Delft Invention

Delft TU Power Window YouTube Clip

It is really interesting to see the variety of business plan competitions that are focused on finding technological solutions to environmental and energy challenges. What is also interesting is that often these competitions are organised and funded by large engineering or energy companies as well as by research institutions. I think this is a really positive move for the green movement: by making it a business opportunity you can guarantee peoples interest and investment to make real change. I look forward to see what ideas come out of the competition this year! 

Technology Idea of the Week

Technological developments help determine the future of energy sources so I have decided to introduce a new feature in my blog: Technological Idea of the Week! Some of the ideas maybe in the start up stage, some of them maybe more in the creative stage! This will help to examine some of the new players in the energy market alongside the giants such as oil and nuclear power.

The Solar Chimney 

For my first edition in this series I am going to look at a project that takes a new approach to solar and wind power. What is particularly unique about this project is the way it combines different renewable technologies to help improve reliability and maximise power production. 

Image Courtesy of Solar Innovations

The Solar Chimney has two key components: a array of solar cells and a chimney with a turbine at the top. Air is heated at the base by the solar cells and therefore decreases in density and rises up through the chimney. This creates an updraught of air which will propel the turbines at the top of the chimney generating electricity. This can be seen in the diagram below which also demonstrates how this could be attached to houses and utilise pre-existing chimneys.

Image Courtesy of Solar Innovations

This idea has been around since the beginning of the 20th century and an experimental one was constructed in 1982 but then taken down due to concerns over collapse (BBC News, 20th November 2013). However, this idea has suddenly been given life again due the backing of Per Lindstrand who aims to build a 1km (yes 1km) high tower! He is famous for being the first person to cross the Atlantic in a balloon and has funding for this project from the 1851 Royal Commission (The Engineer, 19th November 2013).

Over the last thirty years there has been a lot of research into modelling solar chimneys to try and estimate how effective they can be. The chimney height and turbine head design have the biggest impacts on the efficiency of the solar chimney (Hamdam, Renewable Energy, 2011). Comparison of existing solar chimneys in Spain and Australia have allowed testing of the models to access their validity but there is much more research needed to make sure we use the best design to maximise efficiency (Nizetic et al, Energy Journal, 2008).