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Solar Cars

M.R.Fiore, C.Piscitiello (*) - Linguistic Mediator: R.Triggiano (*) - G.Rizzo (**)
(*) Istituto Alfano I - (**) DIMEC, Università di Salerno
 

Summary

This is an introductory work looking into the possibilities of freeing the means of locomotion from dependence on fossil combustible. The solar powered car is the dream of all the environmentalists who dream about a car functioning through a renewable energy with a low or no environmental impact.
This work presents some historical references concerning the technological evolution of such vehicles also considering races on a world wide level, a summary description and the basic functioning of a car that utilizes solar energy; a simple analysis of costs and limits of this type of technology. It also gives hints on the present state of research and the possible perspectives.

Historical background

The first prototypes of solar cars appeared in the 80s. They were very light and single seated with no real practical value. When Worden got interested in the building of his first solar car Solectria, there wasn’t any bibliographical reference that could be helpful in the construction of such a vehicle.

Worden riding Solectria 1

http://web.mit.edu/6.933/www/Fall2000/solarEclipse.pdf

At the end of the 70s, after all the events of the world energy crisis, Hans Thostrup had the inspiration for a new kind of pollution free vehicle and developed the Quiet Achiever. Together with Larry Perkins he drove the first solar car for 4052 km between Sydney and Perth in 20 days.

Quiet Achiever

http://www.speedace.info/quiet_achiever_solar_car.htm

After this in 1987 there was the first world solar challenge and out of 23 competitors GM Sunraycer won finishing the journey with an average speed of 67 km/h.
This race, that still takes place today across the Australian desert over a distance of about 3000 km, was born in 1987 and since then it has represented a fundamental reference about the experience of solar cars, the main step in the applied research of the exploitation of sun also for covering great distances.
The World Solar Challenge started from Hans Thostrup’s initiative, the Danish pioneer born in 1944, the first to circumnavigate Australia on a 16 feet boat. In 1990 a higher number of means appeared to have more advanced technical characteristics if compared with those manufactured in 1987. The winner in 1990 was the team of the Swiss School of Engineering in Biel. In 2005 Nuna III that ran 3000 km in 29 h and 11min got the first place in WSC for the third time. This car had a futuristic design. It was built by Dutch students of Delf University (out of 11 students 3 were women). It kept an average speed of 95 km per hour.

Nuon Solar Team, Netherlands

http://www.wsc.org.au/2005/competition/our.teams/Nuna.3/

The World Solar Challenge shows that the alternative energy is not only an environmental utopia. Certainly the prototypes of the race have their own limits but they also represent a window open towards the future.

How is it built and how does a solar powered car work?

Generally prototypes of solar powered cars have been built using an aerodynamic shape in order to reduce the air resistance. For the building of the external body have been chosen special plastic materials, because light and resistant. The car surface is covered by highly efficient solar panels. These panels convert the solar energy into electric energy stored in different kind of batteries that supply power to the electric engine. The latter will change the electric energy into mechanic work transmitted to the wheels.

Model Solar Car System Block Diagram

http://www.elec.canterbury.ac.nz

In advanced prototypes a triple set of panels is displayed on the car in a way that the solar light and the energy after passing through the first layer of cells can be used by the second and even by the third one. The car is also equipped by small devices that give the best batteries and solar panels performance even when the car is parked in the shade or when it’s very cloudy. A special electronic device is connected to a PC in the car calculating either the solar cells power supply or the batteries one. Balancing it , the voltage through which the batteries are supplied by the solar cells is modified in order to obtain the best result. Such vehicles can reach a speed of about 150 km/h and their weight is about 300 kg.

Costs and limits

Sun can be considered free, oil not! Such statement can be a remarkable starting point concerning the study looking into freeing the means of locomotion from dependence on fossil combustible.
The solar powered car is still a dream, it depends on the sun and can’t work without it. Considering the average daily time of a car usage and the average daily energy provided by sun we can imagine a car capable to exploit the solar energy but there are some difficulties to be solved:

  1. Solar panels are bulky and have to be sun oriented, then they are expensive and subjected to be damaged.
  2. Can we always park a car in the sunshine?
  3. Where can we store the energy collected by the panels when the car is parked?

Mr. Murianni interviewed for the Newton magazine Prof. V. Naso, professor of energetic systems at the University “La Sapienza” of Rome and president of ISES Italia ( International Solar Energy Society), stated that there is a physical limit to the building of the solar powered cars for an ordinary use. Out of the earth atmosphere the sun supplies a quantity of energy less than 1.4 Kw for square mt. On the earth in favourable conditions we can have at our disposal on the solar panels 1 Kw for square mt. It is not possible to expose more than 10 square mt panels on a car, it means maximum 10 KW. To move our technological cars, today our engines need about 60 KW. Besides nobody doesn’t want to use his car when it rains or in the night. At the World Solar Challenge such a dream came true: a lot of famous researchers gathered there to compete with very expensive cars using advanced technologies to obtain high efficiency in the solar panels, aerodynamic shapes, and very light materials.

Now solar powered cars covered by photovoltaic panels charging lead, nikel-cadmio or lithium batteries have been built. A professor at the university of Alabama, A. Passerini is ideally far from the competition of such cars (usually cars of about 150.000 Euro).Passerini built some small solar powered cars, one of them called Canary II ZEV, built in 1996, cost 7000 dollars ( authonomy: 160 km, speed 65 Km/h, six 12 volts batteries, weight 408 kg two seats).
The real aim of such cars is not to be a symbol of competition, but to show that solar powered cars can be useful in our daily life. As all the WSC actual results, Europe is in the forefront as concerned this kind of research.

What about the research?

From the environmental point of view the best solution is given by the hybrid electric car with an optimized internal combustion engine reducing pollution and producing electric energy to charge the batteries used for moving the vehicle.

Mr. D. Sparisci wrote an article on “Repubblica” : “ Now the hybrid car is also solar” a photovoltaic kit will be commercialized by an American company to be installed on the Toyota Prius, the car symbol of the ecologists.

According to Solatec, cars equipped with solar panels, increase their authonomy of 10% ca. After testing it on a prototype driven with different weather conditions, the kit was sold at 2.195 dollars. The 30 watt panels are fixed on the top with sticky tape and recharge the batteries of the hybrid system by means of a special power supplier switching the sun rays while driving or simply parking.

According to the latest news the Canadian company “Solid Works” through the project “Power of One” is going to use the solar powered car technology for the common cars. This prototype succeeded speed, braking and stability tests necessary to circulate in USA.

 

A prototype of electric hybrid car with PV panels has been developed at Tokyo University of Agriculture and Technology. Further PV panels were installed on the top of a building to recharge batteries. Car weight increased of 350 Kg.

K. Sasaki et al./Solar Energy Materials and Solar Cells 47 (1997) 259-263

 

A very advanced prototype of HSV (Ultra Commuter) has been recently developed at the Queensland University, adopting a hybrid series structure – 2.5 square metres of solar panels with 375 Watts. In sunny weather the Ultra Commuter can travel up to 60 km a day on solar power alone. A 360V Li-Ion battery pack extends this to 200 km. A compressed natural gas powers a 10 kW generator to feed batteries, producing a total range of 500 km. The car is propelled by two 75 kW motors that sit inside the rear wheels.

A new kind of cells are now available and are able to supply electric energy if treated with hydrogen and oxygen or to produce hydrogen and oxygen from water if supplied with electric energy. Their ratio between weight and power is also very low. The problem is the fuel since it can't be liquefied and requires heavy and thick tanks to be stored in, with further waste of compression work.

Developing prospects can be:

  • improving the efficiency of the photovoltaic cells and reducing their cost,
  • developing reversible cells working with elements not gaseous, not polluting and easily storable in normal tanks,
  • building simple electric propulsors retrieving the wasted energy generated in the attrite while braking or driving downhills.

The solar powered car of the future will be probably an electric car without solar panels on board or partly equipped to satisfy the demands. It will work with cells supplied with not gaseous products or easily liquefiable and available along the roads at petrol stations and rechargeable from the current supplied by photovoltaic panels installed on house roofs and terraces.

References

Papers

http://www.repubblica.it/2005/l/motori/dicembre05/superprius/superprius.html
” La super Prius è fra noi Con i pannelli solari vola” (D. Sparisci)

http://www.repubblica.it/2005/l/motori/dicembre05/autosolare2005/autosolare2005.html
“Un'auto solare da usare in città Ecco la sfida della SolidWorks (V. Borgomeo)

http://www.repubblica.it/2005/i/motori/settembre05/solarchellenge05/solarchellenge05.html
“Al via la F 1 delle auto solari: Partita la Adelaide-Darwin ” (Repubblica)

http://www.repubblica.it/2004/j/motori/ottobre04/bibendumcina/bibendumcina.html
“Challenge Bibendum a Shanghai In Cina la corsa di auto ecologiche” ( S.Braccini)

http://www.repubblica.it/2004/g/motori/luglio04/corsasolari2/corsasolari2.html
“Auto solari in pista a Suzuka E' il Solarcar Race 2004” di (V.Borgomeo)

http://www.repubblica.it/2004/f/motori/giugno/nuna2initalia/nuna2initalia.html
“In Italia la Nuna 2 è l'auto solare più del veloce del mondo” (Repubblica)

http://www.repubblica.it/2003/l/motori/dicembre03/400kmfuelcell/400kmfuelcell.html
“Quattromila chilometri con un'auto a idrogeno” (Repubblica)

http://www.repubblica.it/2003/k/motori/novembre03/mgibrida/mgibrida.html
“L'auto ibrida diventa spider - Elettrico o a benzina, un computer sceglie autonomamente quale dei due propulsori usare” ( M. Caldera)

http://www.repubblica.it/online/cultura_scienze/macchina/macchina/macchina.html
“Settemila chilometri con auto a energia solare” (Repubblica)

http://www.repubblica.it/online/cultura_scienze/idrogeno/mondo/mondo.html
“E tra poco il mondo andrà a idrogeno” (Repubblica)

http://www.esa.int/esaCP/ESAHK2OED2D_Italy_0.html
“La nostra auto è spaziale” (ESA)

http://newton.corriere.it/Pregresso/2003/11/2003110100010.shtml
” Il veicolo del futuro che non guideremo mai ” M. Murianni

http://newton.corriere.it/PrimoPiano/News/2004/06_giugno/21/nuna.shtml
“Nuna2 in giro per l'Europa: 6500 km e neanche una goccia di benzina” (Newton)

http://newton.corriere.it/Pregresso/2002/03/2002030100002.shtml
“Idrogeno: è in arrivo l' energia pulita” M. Murianni

http://newton.corriere.it/PrimoPiano/News/2003/11_Novembre/19/numa2.shtml
“Nuna II batte tutti i record del World Solar Challenge” (Newton)

Books

Title: “The Leading Edge: Aerodynamic Design of Ultra-Streamlined Land Vehicles”
Author: Goro Tamai
Publisher: Bentley Publishers - Date of Publication: Aprile 2003
”The Leading Edge is the first book to summarize the design and construction issues of solar cars and ultralight land vehicles…”

Title: Cars (Transp)
Author: Julie Richards
Added author: June Loves
Publisher: Chelsea House Publications - Date of Publication: Aprile 2001
”This series presents information about six different forms of transportation in a database format, linking information literacy with computer literacy…”

Title: More with Less: Paul MacCready and the Dream of Efficient Flight
Author: Paul Ciotti
Publisher: Encounter Books - Date of Publication: Settembre 2003
”In the 1970s a small group of unknown southern California visionaries, working independently on their whims and hobbies, developed an interest in lightweight, low-powered machines…”

Title: The Solar Car Book with Other
Prodotto da Klutz Press
Publisher: Klutz - Date of Publication: Settembre 2001
”This book about solar power comes complete with a real solar-powered car to assemble…”

Link

http://www.ilsolea360gradi.it
Newsletter sull'energia solare e energie rinnovabili pubblicata da ISES Italia, sezione dell'International Solar Energy Society

http://www.futura2.it/cosae.htm
Associazione Futura

http://ing.univaq.it/energeti/research/Macchine/Scheda6.htm  
Dipartimento di Energetica dell'Università dell'Aquila

http://www.wsc.org.au/2005/
World Solar Challenge 2005

http://www.unisa.edu.au/solarcar/
University of South Australia

http://www.cdu.edu.au/solarcar/album.html
Fuji Xerox Desert Roses

http://web.mit.edu/solar-cars/www/noflash/index.html
”Solar electric vehicle team”

http://www.americansolarchallenge.org/
North American Solar Challenge

http://www.und.nodak.edu/org/sea/
Society for Energy Alternatives

http://www.prin.edu/solar/
The Principia Solar Car Team


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