specs

In order to evaluate the viability of solar vehicles, one must first understand the governing elements. Solar vehicles rely on solar cells. These cells date all the way back to the 1950's. Before this time, people could only rely on mirrors to concentrate the sun beams into one area. Below is an incredible solar powered steam engine that was built in the early 1890's in Pasadena California by a farmer to pump water for his ostrich farm! The boiler held about 100 gallons of water, which was fed automatically. It was capable of pumping 1,400 gallons of water per minute.

The first type, n-type, is formed when an element such as silicon from group IVA in the periodic table is doped with an element such as phosphorus from group VA. Phosphorus, like other elements from group VA, has five valence electrons. When introduced in silicon, it forms a negatively charged semiconductor with an extra electron that can easily be dislodged.

The second type, p-type, is formed by doping an element from group IVA with an element from group IIIA such as aluminum or boron. Aluminum, unlike phosphorus, has only three valence electrons in its outer shell. Thus when silicon is doped with aluminum a positively charged semiconductor is created with missing electrons or "holes". These holes behave like electrons, but have a positive charge.

Joining a p-type and n-type semiconductor creates a solar cell or photovoltaic cell. When they are brought together, electron carriers are free to move around. Since they have opposite charges, carriers move toward each other. In the process they form an electric field called a gradient, similarly to the electric field formed within a parallel plate capacitor. This electric field is also responsible for the direction of the electric current.

Concerning the kind of crystal there are three different types of cells: monocrystalline, polycrystalline and amorphous. Production of monocrystalline silicon cells is quite expensive but these cells are more efficient than polycrystalline ones. If a thin layer of silicon is evaporated on e.g. a glass you get amorphous cells. The layer is less than one 1 µm (human hair: 50-100 µm), so that production cost decrease since little material is needed. Unfortunately amorphous cells are not very efficient yet. For this reason there are only used for small applications such as watches and calculators.

Material	Efficiency in % Laboratory	Efficiency in % Production
Monocrystalline Silicon	About 24	14 to 17
Polycrystalline Silicon	About 18	13 to 15
Amorphous Silicon	About 13	5 to 7

The study of superconductivity began early in the 20th century when Dutch physicist Heike Kamerlingh Onnes observed that mercury displayed no electrical resistance when cooled to very low temperatures. Superconductors remained a scientific enigma with few practical applications until a superconducting metal wire made of niobium and tin was developed in 1960. Later made of a niobium and titanium alloy, it was this discovery that represented the first practical application of superconductors. Still used today, the nobium and titanium alloy compounds are called low-temperature superconductors. They are now prevalent in magnetic resonance imaging (MRI) machines, high-energy physics, and nuclear fusion. Commercial use has been limited because of the high refrigeration costs needed to cool the materials to such low temperatures.

Two significant discoveries in the1980’s launched the search for low-cost, high temperature superconductivity. In 1986, two scientists at IBM, Alex Müller and Georg Bednorz, discovered a new type of superconducting material. Unlike the low-temperature superconductors, which were metallic or semi-metallic, these new compounds were ceramic and were superconducting at much higher temperatures. Müller and Bednorz won a Nobel Prize for their discovery. In 1987, Paul Chu at the University of Houston discovered a compound that became superconducting at even higher temperatures. Dr. Chu’s discovery was particularly significant because the compound he used was cooled with affordable, accessible liquid nitrogen.

TIMELINE OF SUPERCONDUCTIVITY (http://tqd.advanced.org/20872/timeline.html):

NOTE: Because of the impossibility of having a complete timeline because of the number of advances in this field and how rapidly they occur, we chose only to note the most significant ones and a few others to show the progression of the Tc barrier.

1987: (February) Ceramic found to have Tc=98 K at University of Houston with Paul Chu

1988: Allen Hermann of the University of Arkansas makes a superconducting ceramic containing calcium and thallium that superconducts at 120 K. ; IBM and AT&T Bell Labs scientists produce a ceramic that superconducts at 125 K.

1993: Schilling, Cantoni, Guo, and Ott from Zurich, Switzerland, produce a superconductor from mercury, barium and copper with maximum Tc=133K.

Superconductivity is the ability of certain materials to conduct electrical current with no resistance and virtually no losses. This ability to carry large amounts of current can be applied to motors, generators, and to electricity transmission in power lines.

Superconductors, as opposed to most conductors used today, can conduct electricity without losing energy to electrical resistance. Certain materials become superconductors when they are cooled to very low temperatures. Low-temperature superconductors exhibit superconductivity at temperatures near Absolute Zero (0 Kelvin [K] or –273 degrees Celsius [C]).

Recently discovered high-temperature superconductors (HTS) can function at temperatures as high as 140 K (-133oC). This is crucial because high-temperature superconductors can be cooled more economically and efficiently than low-temperature superconductors. Thus, real world applications of HTS are much more feasible. Superconductors also repel surrounding magnetic fields. This phenomenon is demonstrated when we levitate a magnet above a cooled superconductor, and it is the force at work in Japan's famous Maglev train.

Much of the research and development of high-temperature superconductivity (HTS) is focused on wire and system development. HTS wire must have the strength and flexibility capable of carrying large currents in a magnetic field. The three areas vital to making HTS wire systems commercially feasible are 1.) optimizing critical current, 2.) operating temperature and field, and 3.) cost.

Critical current: Critical current is the amount of current a given wire can carry without losing superconductivity. It is measured as critical current (Ic) or critical current density (Jc). Critical current density is simply the total amount of current a wire can carry (Ic) divided by the cross sectional area of the superconductor. Goals for critical current are 100-1000 amperes. Goals for critical current density are 10,000-100,000 amperes/square centimeter.

Operating temperature and field: Additionally, HTS wires must be able to carry current at relatively high temperatures to decrease the difficulties associated with cooling. The anticipated range for a feasible HTS operating temperature (depending on the application) is 4.2 Kelvin (K) (-269oC) to 77 K (-96.2oC). Superconducting devices also require tolerance to surrounding magnetic fields. They must be able to operate in fields of 2-5 teslas.

Costs: Improvements to critical current, operating temperature, and magnetic field tolerance will result in cost-effective HTS wire. The goal is to being down HTS wire costs to $0.01/ampere-meter.

Transmission cables that carry current without energy losses will increase the capacity of the transmission system, saving money, space, and energy. Prototype transmission cables are currently being developed by teams led by Pirelli Cable Company and Southwire Company.

Motors made with superconducting wire will be smaller and more efficient. A 400-horsepower motor is being developed by an SPI team led by Reliance Electric Company.

Generators will use superconducting wire in place of iron magnets, making them smaller and lighter. New generators also may get more power from less fuel. An SPI team led by General Electric is developing a 100-megavolt-ampere generator.

Fault-current limiters help utilities deliver reliable power to their customers. HTS fault-current limiters detect abnormally high current in the utility grid (caused by lightning strikes or downed utility poles, for example). They then reduce the fault current so the system equipment can handle it. An SPI team led by Lockheed Martin recently produced a successful HTS fault-current limiter that will soon be ready to market.

Energy storage in both flywheels and superconducting magnetic energy storage systems will ensure the quality and reliability of the power transmitted to utility customers. In addition, energy storage provides utilities with cost savings by allowing them to store energy when the demand for electricity is low and generating the power is cheap. This stored energy is then dispensed when demand is high and power production is more expensive.

Cellular phone base stations will use HTS filters. Some people predict that this will be one of the most significant early markets for HTS.

Magnetic resonance imaging (MRI) machines enhance medical diagnostics by imaging internal organs—often eliminating the need for invasive surgeries. MRIs, which currently are made with low-temperature superconductors, will be smaller and less expensive when made with HTS.

Maglev trains seem to float on air as a result of using superconducting magnets. These trains have been under development in Japan for two decades; the newest prototype may exceed 547 kilometers (340 miles) per hour.