solar tree as light pole and aesthetic pleasure in...

Copyright 2016 by Plovdiv University "Paisii Hilendarski" - Plovdiv, Bulgaria.

15th "International Scientific Conference" RE & IT - 2016, SMOLYAN - BULGARIA

SOLAR TREE AS LIGHT POLE AND AESTHETIC PLEASURE IN URBAN ENVIRONMENT

T. MUZIKANTS, M. VANAGS,A. VOLKOVS, A. GRUDULS, J. KLEPERIS

Abstract: Every hour the Earth reaches the amount of solar radiation that can provide mankind's energy needs for a year. Why should we not use the solar energy? It is only sensible decision to generate energy from the light received from the sun. The Solar Tree is a functional design object which picks up solar energy with solar cells, placed as leaves on its branches, and stores energy for a night in batteries. Solar cells are light sensors too and as soon as the Sun goes down, the control scheme switch on the LED lights, built in the tree. The Solar tree, depending on its size, can be used both in public and private sectors. The solar Tree as a lighting object in a city serves also to move forward the public opinion, especially of the new generation, towards the conservation of nature resources and various use of solar power. It shows us that solar power as the renewable energy resource can be used with aesthetic and fascinating design methods. World experience is reviewed and results analysed from first prototype built.

Keywords: Solar light pole, Solar energy, Alternative energy technologies, Aesthetic and practical application.

1. Introduction The Maxwell stress tensor method

(MSTM), the virtual work method (VWM) and the nodal force method (NFM) are among the most popular methods of electromagnetic force computation by the two-dimensional finite element method (FEM) with nodal elements [1, 2, 3]. Theoretically, these force

Solar tree is a revolutionary urban lighting concept that represents a perfect symbiosis between pioneering design and cutting-edge eco-compatible technology [1]. Solar tree opens up new prospects for urban lighting in that it satisfies today’s most pressing environmental, social, Cultural and aesthetic demands.

The tree's lights went on for the first time in Vienna on October 8, 2007 at 11:00 pm and are now on display outside the La Scala opera house in Milan [2] (Fig.1).

The tree was designed by Ross Lovegrove, a British designer, who said that they are not only efficient but also attractive and bring "nature into a gray city environment". Ross Lovegrove is a designer and visionary whose work is considered to

be at the very apex of stimulating a profound change in the physicality of our three dimensional world [3]. The idea came from Peter Noever, the Director of the Austrian Museum for Applied Arts in Vienna. This design was turned into reality by an Italian company specializing in designer lighting systems, Artemide, as well as the world's largest producer of photovoltaic (PV) cells, the German company Sharp Solar.

Fig. 1. Solar tree on display at the Piazza della Scala, Milan (Italy, photo by D. Zanardi [1])

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The combination of innovative design with advanced technology, along with an acute sensitivity to environmental concerns makes Solar tree the ideal prototype of “green thinking. Solar tree draws inspiration from the organic forms of nature, reinterpreting the morphology of the tree and introducing the sensuality of the natural world into the urban context, “it celebrates design, nature and art and represents the DNA of our time” [3]. A sinuously elegant tree with ecologically intelligent ‘fruits’-that is LED bubbles that light up at night powered by sunlight accumulated during the day by solar panels - the aesthetic refinement of the design - is thus integrated with an extremely high technological content [3].

Solar architecture and technologies are known already for more than 2500 years [4]. Our society abounds with people who believe that solar energy is exotic new source of energy requiring decades of further research and development before it can be proven practical. Butti and Perlin show that on the contrary, solar power, water heating and home heating technologies have been evolving through thousands of years [4].

The shape of Solar tree described in our article is an apple-tree - Latvians most intimate, the most common, and often mentioned in folklore the "Golden Apple Tree" (Fig. 2).

Fig. 2. Design of Latvian Solar tree – Golden Apple tree

For centuries, as is known a proper tree

must be with nine branches and nine flowers on each branch. Indeed, the nine branches most effectively fills allocated space of the tree canopy.

Design object through the use of solar energy gets not just functional and sustainable quality, but the additional value of solar semiotics. In olden times people adored and worshiped the Sun in different ways, so highlighting its particular importance in a human life. In mythology of many

nations, also Latvian writings can be found the sign of the Sun and the Sun tree as a symbol of the World tree. The Sun is associated with something good, beautiful, valuable. Sun as the preserver of all life is a strong semiotic sign, so the design of the product through the use solar energy takes on a special value added.

This article summarizes our first results about Sun tree as good-looking self-sustainable light pole in urban environment with some additional facilities like charging port for mobile smartphones.

2. Еxperimental details

Frame structure of built prototype tree is formed of metal tubes with different diameters and coated with polymer composite shell. The trunk holds three branches of the curved tubes which each diverges into three smallest branches with an overall height of construction 3 meters (Fig. 3). Each from the 9 smallest branches (ø 30 mm) has a leave at the end with photovoltaic (PV) solar panel with peak power 20 W, area 52x29 cm2, silicon single crystal cells with efficiency 13%, an open circuit voltage at optimal lighting 21 V, and short circuit current at peak power 1.22 A.

Fig. 3. Drawing of Solar tree skeleton with solar panels as leaves at the ends of branches

All 9 PV solar panels are connected in

parallel circuit, having total peak power 180 W, nominal voltage 12-15 V and current 9 A, what is directed through voltage stabilizer scheme to charge two 70 Ah, 12 V lead-acid batteries connected parallel. Averaged open circuit voltage measured from all PV solar panels connected parallel is used as light sensor for microcontroller managing switching on/of the lights in leaves (Fig. 4).

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Fig. 4. Principal electric scheme of Solar tree

Each leave has LED lights – 1.5 m long

LED tape along the edges with 35 white LEDs – total power 6 W, three individual LED floodlights, each with power 1 W. LEDs are powered with 12 V, and at maximal lighting intensity each leave consumes 9W/12V = 0.75 A; all tree consumes 0.75 A * 9 = 6.75 A. Three central leaves from each thickest branch has infrared motion sensors too, which are used by microcontroller to range an intensity of LED lights – 3 operating programs:

Program 0 (quiet) ensures an average illumination of 50 lux by an internal regulator that maintains the LED sources around edges of leaves at 15% of maximum power (consuming around 1 A altogether);

Program 1 (movement at a distance) provides the LED sources around leaves with 50% of maximum power (300 lux) and separate floodlight LEDs with 50% of maximum power (consumption 3.3 A altogether); reverts automatically to Program 0 after 10 seconds if motion stops;

Program 2 (movement close) provides all LED sources with 100% of maximum power (600 lux) which reverts to Program 1 after 10 seconds if motion stops.

3. Results and discussion

Prototype design has box-type base (Fig. 5) where all electronics and battery pack is arranged. Prototype solar tree is installed in an open area to record information about energy collected in the day and consumed at night in real conditions. In Latvian latitudes it is characterized by surpluses harvested from Sun electric energy in summer and shortfalls in winter; the challenge of scientists is to find “the golden mean”, how to use in summer accumulated energy during the winter time. Some calculations of energy balance can be made after results collected from October, 2015, when this prototype tree was finished and tested 4 days in in open air in November 17-20 (Fig. 5). The prototype

was equipped with sensors, which automatically switched on more LED lights on the Solar tree as well as switched on music recorder when people approached. Hundreds of People with families enjoyed the interactive Solar tree. Many of them left very positive remarks in social network Facebook.

Fig. 5. Solar tree prototype in Riga`s Old Town

Ordinary passer-by walks along the Solar tree within 30 seconds, from which 20 seconds the tree is giving light with 50% power and 10 seconds at maximum power. In the chosen site where the tree is placed in the dark hours it takes an average of 12 people passing it in 1 hour (in evenings and mornings more, overnight less). It means that from 1 hour the leaves of Solar tree consumes 0.3 A during 54 minutes, 4 minutes – 3.3 A and 2 minutes – 6.75 A, total power consumed is 0.716 A/h or 8.6 W in one hour. With fully charged batteries (140 Ah) in such regime the Solar tree is capable of functioning 195 hours or 8 consecutive days of cloudy or overcast weather. In day-time when battery charging is switch on, assumption can be made that 30% from installed power 180 W can be harvested every hour – 54 W. Latvia is situated at latitudes between 56-58 degrees – in Northern hemisphere, in winter minimum the light is 6 hours per day – 324 Wh (unless the Sun shines), which at the consumption 8.6 W/h the rest 18 hours (155 Wh) has a surplus of energy (169 Wh) for couple cloudy days. However, in the summer, when day length is 18 hours and at night the light is required only for 6 hours, the surplus energy remaining every sunny day is 861 Wh, what could

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be used to recharge mobile devices given back in grid.

Typical Solar tree as light pole in urban environment is planned with overall height 6 m without base box, where electronics is placed inside the trunk and batteries – under tree in the ground, but sockets to recharge portable electronic devices, mobile phones or electric cars – on the trunk (Fig. 6).

Fig. 6. The Sun tree in the streets - vision of the future

Now the data about available/consumed

solar energy in Solar tree is being still collected. In winter time if necessary it is possible to replace batteries once per week, but in summer the connection with electrical grid is option.

Prototype for the first time was exposed in Riga, October 15th, in the exhibition “Energy and Environment 2015”. There were positive review both in the press and social networks. One of the biggest Latvian daily newspapers wrote:

“One of the most impressive exhibits on the exhibition of power industry, energy efficiency, infrastructure, and environmental technology Environment and Energy 2015 promises to be a Solar tree, which converts solar energy in an appropriate light to human eyes. In principle, any tree is a solar tree, which accumulated solar energy and people them are using already for thousands of years since the moment they learned to get the fire. Now for the savages called people could do it without the knowledge about modification of matter in the level of molecules, atoms and quarks, during which a tree starts with growing into empty space, consumes water, gases, light and transforms in biomass, and only then the tree logs, bark, branches could be converted to light, heat and ashes. But they knew the role of the Sun in the maintenance of their lives and worshiped the Sun. Now the most civilized part of the world called Europe has going a crazy with wood burning. Misfortune only is that for the modern society needs the trees are cut down faster than they can grow back. This raises the

question of whether the tree cut for burning really qualifies as renewable energy resource. Solar tree is antithesis of natural wood, which do not need to be burned and gives back harvested energy in the form of light and electricity. In this work is being presented joint project of the researchers from Institute of Solid State Physics, University of Latvia, and Talivaldis Muzikants from Design Department of the Latvian Academy of Art (see his master's work [5]).

There is also a big interest from the private sector about Solar tree. The test in a country farmhouse shoved us that Solar tree can be displayed not only in urban, but also in rural environment (Fig. 7).

Fig.7. Solar tree exposed in rural area in March, 2016

There is a future vision of designer to make

a big scale Solar tree - Golden Apple tree in Riga, placed in front of the National Library as a symbol of use of solar power and green technologies (Fig. 8).

Fig. 8. Sketch with Solar Tree at the recently opened new Latvian National Library building

4. Conclusions

Article summarizes our first results about Sun tree as good-looking self-sustainable light pole

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in urban environment with some additional facilities like charging port for mobile smartphones.

The trunk of first prototype is built from metal tubes with different diameters and coated with polymer composite shell, and holds three branches which each diverges into three smallest branches holding 9 leaves - an overall height of construction is 3 meters. Each from 9 leaves has photovoltaic solar panel (20 W, area 52x29 cm2) on top side and LED lights –along the edges and bottom (maximal consumed current 0.75 A). As light sensor open circuit potential from all in parallel connected solar panels is used, but three infrared motion sensors are necessary to adjust LED light intensity accordingly situation – that is done by microcontroller having 3 operating programs. Two batteries each 70 Ah is used to store energy harvested in day-time and spent in night-time.

It is concluded that the design of the product to our perception works on several levels. We appreciate not only its functionality and appearance or visual message, but also the potential visual message- which is the Sun itself and the role of Sun as inexhaustible renewable energy in modern green technologies.

We can speak about the Sun as a sign contained in this product. We take not only the product itself but also symbol- Sun, what it represents.

And finally we can say that this design object solar tree represents the use of solar energy and promotes to use it in our life. Solar trees are at the same time sustainable design solution and interesting design object in the urban environment.

5. Acknowledgement

Authors acknowledge financial support from National Research Program LATENERGI (2014-2017). Acknowledge also financial support from Art Academy of Latvia for author’s participation in the conference.

References

1. S.MadhuPriya and K.Divya, SOLAR TREE – An artistic design to arrange Solar Panels. January 25, 2014, Yuva Engineers. http://www.yuvaengineers.com/solar-tree-an-artistic-design-to-arrange-solar-panels-s-madhupriya-k-divya/

2. J. Burgermeister, Ross Lovegrove`s Solar Tree, 2007 Available from: http://www.renewableenergyworld.com/articles/2007/12/introducing-the-solar-tree-50934.html

3. Ross Lovegrove - designer and visionary: http://www.rosslovegrove.com/index.php/about-us/#sthash.odhRbM6e.dpuf

4. K. Butti, J. Perlin. A Golden Thread (2500 Years of Solar Architecture and Technology). Cheshire Books, Palo Alto Van Nostrand Reinhold Company, New York Cincinnati, Toronto, London, Melbourne; 1979, 254 p.

5. Find out whether the solar tree can be planted in Latvia? Article from Newspaper Neatkariga Rita Avize (in Latvian): http://nra.lv/latvija/152951-uzzini-vai-saules-koku-var-iestadit-latvija.htm

T. Muzikants The Art Academy of Latvia, 13 Kalpaka boulevard, Riga, LV-1867, Latvia Janis Kleperis 1Institute of Solid State Physics University of Latvia, 8 Kengaraga str, Riga, LV-1063, Latvia [email protected]

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