Solar Transportation

(www.aurorasolarcar.com)

 Perhaps you’ve heard of, or even seen, the odd flat looking cars being raced by various groups around the world. Maybe you’ve heard names like PrISUm, or Aurora (above). These cars are part of a fleet of futuristic looking cars powered entirely by solar energy, and are capable of long distance travel at moderate speeds (200miles at 30-40mph), or short bursts at highway speeds (70mph). Solar cars produce no pollutants of any kind, operating off of electric engines fueled solely by electricity generated through the Photovoltaic effect. The products of several revolutions in the energy industry, these cars provide a glimpse into the changing face of energy and transportation.

Siemens crystalline solar cellPhotovoltaic effect:

In 1839 a scientist named Edmond Becquerel described the phenomena known as the photovoltaic (PV) effect. His research showed that certain types of solid matter produce small amounts of electricity when exposed to light. In the mid-20th century further research found that the PV effect is a conversion of light energy into electricity at the atomic level. In the 1950s new materials were advanced, and the PV effect made it debut in the industrial scene with the introduction of commercially viable solar arrays. Today solar arrays power everything from private homes to government satellites.

Solar Panels:
                                                                                         Solar panels are made up of many individual components known as PV cells. Modern commercial PV cells typically produce between one and two Watts of power, and operate at about 15% efficiency. In contrast, the PV cells produced during the 50s only operated at an efficiency of 4 percent. PV cells are connected into groups of 40 to form modules, groups of 10 modules are called arrays. A solar array can produce 800W of electricity. 10 or 20 arrays can power a modern home.
(www.wisconsun.org)

Batteries:

One of the major obstacles to Solar powered vehicles has been storing energy: what do you do on a rainy day? Recent innovations within the battery industry have the potential to finally provide a solution to this problem. Currently car batteries are lead-based, and are far too heavy and inefficient for use in light-weight solar cars. However Nickel-metal-hydride and Lithium-ion batteries have recently made a big splash in powering handheld devices such as cameras. While not fully developed, these batteries are approx. 3 times as efficient as lead-based of the same weight. Nickel-metal-hydride battery are particularly interesting because they are capable of handling heavy electric loads, and have a 500 recharge lifespan. They do lose 50% of their charge over a span of a year; an issue of only secondary importance to an auto application.

Other Obstacles:

Major issues that remain unresolved include weight, and space. Solar cars lack the engine power to move a heavy-framed vehicle such as an suv or luxury sedan, and no viable solar car has been designed that can hold more than two people. These are serious limitations to producing solar cars for a commercial market. The key to these problems lies in increasing the efficiency of PV cells. Greater efficiency would increase the power generated, allowing the installation of heavier components. It would also decrease the amount of surface area needed for arrays, allowing more interior room. Several new ideas include organic solar cells, and nanotech cells. Detractors of solar cars have stated that the necessary technological developments are decades away, but a new government program might mean that the radical increase in efficiency needed to make solar cars viable may be closer than many think.

VHESC (Very High Efficiency Solar Cell)

The Defense Advanced Research Projects Agency’s (DARPA) Advances Technology and Defense Sciences Offices are currently offering grants in a new project: development of a PV cell with a minimal efficiency 3 times the commercial average. According to the Agency, recent developments in engineered biomolecules, and a new method for fabricating structures on a nanoscale, have the potential to be combined in an effort to develop an economically feasible PV cell for use on satellites and other government equipment.
The program is slotted to run for one year, at the end of which participating teams will be required to submit a minimum of 1000 units each of which are 10cm². The each devise will be required to produce at least .5W, and operate at a minimal efficiency of 50% when exposed to a solar fluence of 1 Kw/m².
Grant proposal are due by May 17, 2005.

Secondary Applications of Solar Energy to the Transportation Industry:

Even if cars powered entirely by the sun’s rays never become viable, solar power could still become a key component in the transportation industry. One groundbreaking new technology, hydrogen power, could receive a huge boost from solar power. One of the barriers to use of hydrogen is the lack of free hydrogen atoms in the lower reaches of earth’s atmosphere. Very soon solar power could be the best option for the clean and low-cost production of hydrogen.