Solar Powered Transportation

Solar powered transportation is a huge variable in the future energy budget of humanity. Presently, liquid chemical fuels like gasoline or diesel are the only viable sources of energy for long distance driving. Electrical based systems are feasible for shorter distances like 40 miles or less between recharges. Even if electric only and hybrid vehicles are wildly successful, longer range trips and heavy commercial vehicles will keep chemical fuel usage at levels above 50% of current levels.

Thus electric vehicles represent a huge possibility for reducing carbon fuel consumption, but they will definitely not eliminate them. Also, it is important to realize that electricity generation relies heavily on carbon based fuels as well. Electric power generation is remarkably efficient, using modern multistage steam turbines a modern coal fired plant can expect to get almost 70% of the energy of the fuel into the power grid. Compare this with 15% or less for the efficiency of an automobile and it is easy to see how a conversion to grid supplied electrical energy will dramatically reduce carbon based fuel usage. The electrical grid is not particularly efficient with losses up to 20% on average, but tanker trucks driving fuel around to service stations wastes a tremendous amount of fuel as well. So, even given the inefficiency of the power grid, electrical powered cars are a huge net increase in efficiency.

In terms of solar power, however, residential solar electricity generation presents a very big relationship. Assume an average sized electric car has a battery capacity of 30Kwh and needs a full recharge every day. Simple math suggests an annual electricity requirement of 10,800Kwh. If the price of electricity is $0.08 per Kwh, the electrical cost for your car is $864 per year. This figure already represents a huge savings when compared to gasoline (full electric charge gets 50miles with a 30mpg car at $3.00 per gallon comes to $1800 per year). However, if your electricity is generated with a solar system, or your electricity is offset by a grid tie solar system, you are paying off your system much faster. This faster payoff rate could make the difference between a PV system being a net loss over 10 years or a net gain over 10 years. For those considering their carbon footprint as a major reason for solar conversion. The benefits in carbon reduction are 4 times greater when eliminating a 15% efficient system (cars) vs. a 60% efficient system (utility power plants).

If higher capacity battery systems or storage systems become available or practical, then the savings can theoretically be greater. Promising storage technologies include:

1. More exotic battery chemistry: Lithium, liquid sodium, Hydrogen fuel cells, Aluminum etc.

2. Rechargeable chemicals: Some are experimenting with electric only production of hydrogen peroxide which could then be used as a fuel both for reaction engines as well as types of fuel cells. There is even a technology that "charges" an aluminum electrolyte. This can allow a quick charging technology that lets a drive charge his battery in few minutes instead of hours.

3. Super capacitors: This electrical device is still hugely expensive per capacity of storage but offers the potential to replace batteries by being lighter, more robust, and being able to be charged very quickly in high current charging stations. These devices are sometimes called, "double layer capacitors", or even, "hybrid capacitors". Hybrid capacitors are really lithium batteries where the anode is fabricated in the same way as a double layer capacitor. These have storage capacity similar to lithium batteries but high current performance similar to super capacitors.

4. Kinetic storage systems: This has already be experimented with in working vehicles. A spinning weight is suspended in a near frictionless container. The weight is spun up to incredible rotational speeds through the use of electro- magnets. Then, the same electro-magnets are used to slow the weight down which supplied energy to the vehicle.

Occasionally someone asks if an electric car can be run with solar panels on it. Assuming the sun gives you 1Kw in full sun light per m² and a typical car has possibly of 4 m² of top profile, then the most power at optimum conditions the motor can put is 4Kw. This is about 1/8 of what most cars would need for reasonable performance. So, it is probably safe to say we will never see a useable car powered by solar panels alone.