Saturday, 14 March 2020

Framing The Power of Art Using Luminescent Solar Concentrators and UV Lighting

This project involves creating vibrant etching artwork using ultraviolet reactive perspex in a Luminescent Solar Concentrator (LSC) configuration with silicon thin film solar panels on the side to harvest light as energy, boosted using an energy harvester circuit designed for indoor solar energy harvesting.

This technology was developed over a few years and has been tested using many different designs. The concept of using solar concentrators in buildings (in windows, roofing, glasshouses etc) has been explored in many research scenarios however the development of indoor based light-energy harvesting for display use is something that is novel in the context of use in displaying artwork.

UV artwork is very interesting and the vibrancy in certain UV reactive materials adds a contrast on images within the environment they are placed that is not found in other display media. The UV light source does not need to be super-bright and often the display is more effective in an environment where lighting is kept at a minimum to bring out the sharper colors from the fluorescence.  Many museums are using this technique to create interesting and eye catching displays for unique visual experiences. In some situations it resembles Neon lighting however it is far more energy efficient and safer to install.


The installation of conventional photovoltaic (PV) solar cells have many advantages. The ease of installation, the ability to generate energy locally and with minimal investment and supervision makes them ideal to install on buildings and integrate within devices.They can be used on rooftops, most portable solar chargers and in other applications directly absorb sunlight and convert it into electricity. 

The major drawback is that amount of power, in watts, conventional solar cells can harvest is dependent on the amount of area the cells cover. So in areas where surface area is a premium, PV solar has clear limits in its energy harvesting capacity. High rise cities for example do not have the space for all but the most superficial of solar energy installations. This is a fundamental problem for genuinely running an energy hungry city on energy harvested directly from the environment.

Electricity is generally consumed first at the source where it is generated. So energy producing installations if positioned far from a cityscape will have their transmitted power drawn from other sources first, such as small towns and villages, and ultimately creates a situation where prioritization of power distribution is backwards - effectively powering the small municipalities before the larger ones.

Accounting for losses in transmission over large distances also means it makes sense to position a power plant as close to a city as possible. This is not so much a problem with stored fuels, such as fossil fuels, which can be stored and converted to electricity in power stations that require less space and are thus possible to install near large cities. With generic renewable energy however, large amounts of space is required, be it wind farms or solar arrays, so it is not really practical to position it near a city for the reason described and certainly not within it, only in a superficial sense such as on rooftops, as city high rises inevitable lead to shading of the surface. 

Conventional PV solar cells made of high quality materials, from Silicon to CIGS, will require refinement, purification, cleaning, doping and deposition and this will naturally increase their expense as the power they are expected to generate, and thus size, increases in demand. So even with conventional photo-voltaic solar cells we are trapped in the process in which the more power we want to harvest, the more money we will have to invest, making the transition to solar energy an expensive one.

This does not even go into mentioning that the most efficient photovoltaic absorption materials known, such as Gallium Arsenide (which has benefits of being a radiation-hard material) and  perovskite photovoltaic materials are extremely expensive.

Concentrating and Harvesting Solar Energy

Methods of concentrating solar energy, such as using reflective mirrors and/or lenses offers an obvious solution to the problem. However concentrating solar energy using conventional methods often means that we must have more supervision and infrastructure available in an area. For example, concentrating solar energy by mirrors and/or lenses is often done by heating water in a power plant infrastructure which may not always be available in a local area and will require yet more investment. 

Moreover, different technologies are required to harvest the concentrated solar energy - i.e. using Stirling engines, thus creating technology barriers along with the economic cost on transitioning to solar energy.

Therefore it would be nice if we were able to use combine the ability to harvest solar energy using conventional solar cells with new approaches to concentrating solar energy. One such approach is the idea to concentrate the solar energy by "pumping" a fluorescent medium with sunlight, akin to how a laser crystal can be pumped with a flashlamp, in which by clever design of the fluorescent medium and optics, the photon population in the flourescnt medium can be concentrated to a large level which can then be delivered to the PV cell.

This is the idea behind the operation of a Luminscent Solar Concentrators or LSC. A LSC absorbs the light on a plate embedded with highly efficient light-emitters called “lumophores” that then re-emit the absorbed light at longer wavelengths, a process known as the Stokes shift. For example, absorbing UV radiation to produce visible light. This re-emitted light is directed by total internal reflection (just like an optical fiber) to a micro-solar cell for conversion to electricity. Because the plate is much larger than the micro-solar cell, the solar energy hitting the cell is highly concentrated.

With a sufficient concentration factor, only small amounts of expensive photovoltaic materials are needed to collect light from a potentially inexpensive luminescent waveguide. The waveguides could be in principle made to be integrated into double-glazed glass windows, thus providing a possible solution to the integration of energy harvesting within high rise cities and across all available dimensions of a building.

Even within a building, in locations where sunlight reaches on walls the concentration of light to generate moderate amounts of energy can be achieved, at the very least for lighting.

Now why would this be important to consider? Well, LSCs have not only the potential to provide a means to Stokes-shift shorter wavelengths, such as UV, into longer ones such as red and blue, but also to provide a means to upconvert longer wavelengths of light, such as infrared, which is not converted to electricity by the PV material into shorter wavelengths such as red.

A large portion of radiation emitted by the Sun itself is in infrared and only generates waste heat in a PV cell, which undermines its overall performance. So developing materials that do demonstrate upconversion of infrared light, from IR lasers, is a reasonable step to developing devices that will work outside of the lab, perhaps using sunlight or alternatively as a way to provide wireless power distribution by means of lasers. Energy distribution by means of lasers, such as the common GaN UV Lasers, may also be possible to demonstrate with such a system..

This project, its images and design was developed by MuonRay Enterprises Ireland for educational purposes.

Artworks Depicted

In this project I created several etchings as a demonstration of how etching UV Perspex on different layers with contrasting colors can create very vivid and sharply colored images, not to mention the inclusion of a mirror which gives the images a sort of "floating pseudo-hologram effect". I will share the images depicted in the video and explain what they are from. All are cultural and historical symbols that I find interesting.

A mythical dragon, somewhat inspired by oriental dragons but I was thinking more along the lines of Lewis Carroll's Jabberwock when I was designing it - "with eyes of flame!"

The Winged Disk - The winged sun is a symbol associated with divinity, royalty and power in the Ancient Near East in particular the Old Kingdom of Ancient Egypt where it was used both to represent the Gods Ra and Horus.

A Celtic Knot Moon in conjunction with a Celtic Spiral Sun. The Celtic Knot is sometimes a depiction of a universe forever in flux but without clear beginning or end either in scale or direction. The Spiral Trigram is commonly associated with the connection between the changing seasons, death, life and rebirth. All are a common motif in Ancient Irish Culture.

The 4 Treasures of the Tuatha Dé Danann, a supernatural magical race in Irish mythology who bore these magical artifacts, crafted in faraway islands beyond Ireland. They are thought to be a pantheon of demigods or precursors to the main deities of pre-Christian Gaelic Ireland. In my depiction of the 4 Treasures, I symbolise each with one of the 4 classical elements of antiquity.

Claíomh Solais (The Sword of Light) - A Magical Sword that when swung no person could escape it. This sword is often associated with Nuada the King of the Tuatha Dé Danann, with him sometimes given the epithet Airgeadlámh, meaning "silver hand/arm". The element I have associated it with is fire.

Cauldron of Dagda - Dagda was one of the Tuatha De Dannan and later on the Irish All Father associated with fertility, agriculture, strength, as well as magic, druidry and wisdom. He is strongly associated with the culture at the Brú na Bóinne (Newgrange). From His cauldron it is said nourishment flows from which nobody is ever left hungry or weak. The element I have associated it with is water.

Lia Fáil (Stone of Destiny) - This is the ancient Coronation stone from which the High King's and Queens of Ireland would be deemed fit to rule the country by the stone itself vibrating. The an ancient stone still sits on the Hill of Tara to this day, however whether or not this is the true one remains unknown. The element I have depicted with this treasure is Earth with plant like roots boring into the ground from the stone to add to the effect and also the name of the stone itself etched in Ogham.

The Spear of Lugh - Lugh is a God of many talents in Irish mythology. He was a master craftsman but also a warrior and in some depictions both a messenger and a trickster. Lugh is linked with the harvest festival of Lughnasadh, which bears his name. He was also attributed to storms and so I have depicted his weapon of choice, a spear, with lighting and attribute it as the element of air. When Lugh uses his spear, it is said that it brings a decisive end to all conflict. 

This symbol is the Hamsa Hand, also known as The Hand of Miriam (Sister of Moses) in Jewish Tradition and also known as The Hand of Fatima in Islam and to a less common extent as the Hand of Mary in Christianity. There is also history of its use much earlier in Ancient India. In general it is used as a protective talisman. It is a symbol that people believe can protect them from harm against the evil eye and bring them goodness, abundance, fertility, luck and good health. In my travels I have seen it quite commonly used on ships in the Middle East as a charm to ward off storms.

With this one I used 3 layers of UV reactive perspex to reasonable effect at creating a vibrant display of color.

This project has been a fun way to share the concept of using perspex to create efficient illuminated artwork that can power itself and remain functional without external power sources. The technique in developing the art has been a learning experience for me and I hope to create more artwork using this technique in the future. 

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