Photovoltaics in transport

There are many applications of photovoltaics in transport either for motive power or as auxiliary power units, particularly where fuel, maintenance, emissions or noise requirements preclude internal combustion engines or fuel cells. Due to the limited area available on each vehicle either speed or range or both are limited when used for motive power.

pace

Solar energy is often used to supply power for satellites and spacecraft operating in the inner solar system due to its power/weight ratio. (In the outer solar system, where the sunlight is too weak, radioisotope thermal generators (RTGs) are used).

Air

There is considerable military interest in unmanned aerial vehicles (UAVs); solar power would enable these to stay aloft for months, becoming a much cheaper means of doing some tasks done today by satellites. In September 2007, the first successful flight for 48h under constant power of a UAV was reported [ [http://news.bbc.co.uk/2/hi/science/nature/6916309.stm] BBC News: Solar plane flies into the night "accessed 10 September 07"] .This is likely to be the first commercial use for photovoltaics in flight.

Many demonstration solar planes have been built, some of the best known by AeroVironment. [http://www.blazingwings.org/entry/top-12-solar-powered-aircrafts/]

* Manned solar planes
**Gossamer Penguin,
**Solar Challenger - This plane flew convert|163|mi|km|0 from Paris France to England on solar power.
*UAVs
**Pathfinder and Pathfinder-Plus - This unmanned plane demonstrated that an airplane could stay aloft for an extended period of time fueled purely by solar power.
**Helios - Derived from the Pathfinder-Plus, this solar cell & fuel cell powered UAV set a world record for flight at 96,863 feet (29,524 m).
** Zephyr [ [http://www.qinetiq.com/home/newsroom/news_releases_homepage/2008/3rd_quarter/qinetiq_s_zephyr_uav.html] "accessed 28 September 2008"] - built by Qinetiq, this UAV set the unofficial world record for longest duration unmanned flight at over 82 hours on 31 July 2008
*Future projects
** [http://sky-sailor.epfl.ch/ Sky sailor] (aimed at Martian flight)
**Solar Impulse (aimed at manned circumnavigation of the globe)
** various solar airship projects e.g. [http://www.lockheedmartin.com/products/HighAltitudeAirship/ Lockheed Martin's "High Altitude Airship"]

Road

Photovoltaic modules are used commercially as auxiliary power units on passenger cars [http://www.brightcove.com/title.jsp?title=447958743&channel=291706308] . The power is enough to ventilate the car in full sun, reducing the temperature of the passenger compartment while it is parked in the sun, improving driver comfort.

The area of photovoltaic modules required to power a car with design range and performance similar to an internal combustion car is too large to incorporate in a solar vehicle. A prototype car and trailer has been built [http://www.solartaxi.com/ Solar Taxi] . According to the website, it is capable of 100 km/day using 6m² of standard crystalline silicon cells, although it is not specified at what latitude. Electricity is stored using a nickel/salt battery. A stationary system such as a rooftop solar panel, however, can be used to power the car from rechargeable batteries.

It is also possible to use solar panels to extend the range of a hybrid or electric car. In May 2007 a partnership of Canadian companies led by Hymotion added PV cells to a Toyota Prius to extend the range. [ [http://www.newswire.ca/en/releases/archive/May2007/16/c9889.html Hymotion modified Prius using solar power] "accessed 14 September 2007"] . [http://www.solarelectricalvehicles.com/ SEV] claims 20 miles per day from their combined 215W module mounted on the car roof and an additional 3kWh battery.

On 9 June 2008, the German and French Presidents announced a plan to offer a cedit of 6-8g/km of CO₂ emissions for cars fitted with technologies "not yet taken into consideration during the standard measuring cycle of the emissions of a car" [http://www.elysee.fr/download/?mode=press&filename=09.06_emissions_from_cars_version_anglaise.pdf"accessed 28 September 2008] . This has given rise to speculation that photovoltaic panels might be widely adopted on autos in the near future [http://www.systaic.com/press/press-release/systaic-ag-demand-for-car-solar-roofs-skyrockets.html"accessed 28 September 2008]

Anecdotal reports suggest that the ' Zap Xebra' PV module option could extend the car's convert|40|mi|km|0|sing=on by convert|5|mi|km|0. [http://www.zapworld.com/files/zap-docs/xebra-xero.pdf ZAP website (electric cars)] [http://www.greencarcongress.com/2007/03/zap_adds_solar_.html Green Car Congress]

It is much more feasible to run an ultralight vehicle on solar energy than a standard car. Many prototypes have been built for challenges. The solar challenge cars can average 100 km/h for long distances. For 2007 a new Challenge class specified an upright seating position and smaller solar panels to create a class of vehicle which with little modification could be the basis for a practical proposition for sustainable transport. The winning car still achieved an average speed slightly in excess of convert|90|km/h|abbr=on. The [http://www.venturi.fr/electric-vehicules-astrolab-concept.html Venturi AstroLab] in 2006 was hailed as the world's first commercial electro-solar hybrid car due to be released in January 2008, with a solar range of 18 km/day and a total range of 110 km it can be charged either from the sun or from AC mains.

It is also technically possible to use photovoltaic technology, (specifically thermophotovoltaic (TPV) technology) to provide motive power for a car. Fuel is used to heat an emitter. The infrared radiation generated is converted to electricity by a low band gap PV cell (e.g. GaSb). A protoype TPV hybrid car was even built. The "Viking 29" [http://vri.etec.wwu.edu/pdf%20files/v29paper.pdf Use of a Thermophotovoltaic Generator in a Hybrid Electric Vehicle, Seal et al, Vehicle Research Institute, Western Washington University Bellingham, Washington 98225] was the World’s first thermophotovoltaic (TPV) powered automobile, designed and built by the Vehicle Research Institute (VRI) at Western Washington University. Efficiency would need to be increased and cost decreased to make TPV competitive with fuel cells or internal combustion engines.

Marine

Japanese shipping line Nippon Yusen KK and Nippon Oil Corporation announced a pilot trial said solar panels capable of generating 40 kilowatts of electricity would be placed on top of a 60,000 ton ship to be used by Toyota Motor Corporation [http://www.enn.com/energy/article/38019] [http://www.environmentalleader.com/2008/09/01/nippon-yusen-ships-going-solar/] . The solar panels would help reduce energy consumption and reduce carbon dioxide emissions by 0.2%. The article adds that photovoltaic systems with capacities of several kW_p have been used on large vessels before but only to power the crew's living quarters. Damage to the panels from salt and vibration remain issues to be resolved. The ship is planned to be completed in December.

Today many electric or hybrid electric boats are in service around the world [http://www.sunboat.com/history/history.html] . Solar power is used to extend the range. The flat orientation of the panels is not optimum for power generation at most latitudes. The Australian project [ [http://www.solarsailor.com Solar Sailor] ] optimizes the position of the modules to for energy capture and aerodynamic performance simultaneously.

The 100% solar-powered "Solarshuttle" 42-passenger boat is currently in service as a passenger ferry across the Serpentine lake in central London.

On 8 May 2007, the solar powered "sun21" catamaran [ [http://www.transatlantic21.org/ transatlantic 21 website] ] became the first solar powered boat to cross the Atlantic. It covered about 7000 between Seville and New York [ [http://www.sail-world.com/usa/index.cfm?nid=34656&rid=4 Green Boating - first bio-diesel now solar] "accessed 14 September 2007]

Solar powered house boats provide low speed operation. [ [http://www.concordmonitor.com/apps/pbcs.dll/article?AID=/20070813/REPOSITORY/708130320 Solar boat rides current] ]

Solar power offers the possibility to operate unmanned autonomous boats, which, as for UAVs is of interest to the military.

Rail

PV panels were tested as APUs on Italian rolling stock under EU project. [http://www.trenitalia.com/en/trenitalia/pvtrain/pvtrain_6/Newsletter1.html PVTRAIN]

PVTrain concluded that the most interest for PV in rail transport was on freight cars where on board electrical power would allow new functionality:

* GPS or other positioning devices, so as to improve its use in fleet management and efficiency.
* Electric locks, a video monitor and remote control system for cars with sliding doors, so as to reduce the risk of robbery for valuable goods.
* ABS brakes, which would raise the maximum velocity of freight cars to 160 km/h, improving productivity.

Personal Rapid Transit

Several Personal Rapid Transit (PRT) concepts incorporate photovoltaic panels.

References

External links

* [http://www.aerovironment.com/ AeroVironment website]