The sun accounts for roughly 99.86% of the mass in the Solar System. It is about 1.3 billion kilometers across and reaches surface temperatures of over 5000 degrees Celsius. Through a process called nuclear fusion, it combines up to 600 million tons of hydrogen atoms together every second. The energy released from this process then travels 150 billion kilometers to the Earth, which absorbs 3,850,000,000,000,000,000,000 Joules of energy from the sun every year, all of which is just begging to be used by humankind. Put into perspective, in one hour, the Earth receives more energy from the sun than the entire human race collectively used in 2002.
Now that's all well and good, but a person logically might be wondering how exactly can this energy be harnessed by humans in order to get things done? Energy from the sun essentially fuels everything on the planet in some fashion. It is absorbed by plants to create food, chemical energy, biomass materials, and eventually even fossil fuels. Buildings can be specially engineered to absorb sunlight as heat and distribute it throughout the entire structure, essentially creating free and clean heating. Yet, primarily, solar energy is harnessed through what is referred to as "Solar Power," which is essentially just using sunlight to create electricity. There are two ways to do this, either directly through photovoltaics (PV), or indirectly through concentrated solar power (CSP).
Photovoltaic cells, from the single-cell units in calculators to the massive panel arrays in power plants, have the capacity to directly convert the photons in sunlight into direct current electricity. Essentially, a photovoltaic cell functions by absorbing photon particles in sunlight, which then collide with electrons within the cell, causing the electrons to be knocked into a higher energy state, thus creating a flow of electrons, otherwise known as "electricity." PV cells are highly effective and have many uses, from running a pocket calculator, to recharging batteries, to powering orbiting satellites. One of the fastest-growing applications for PVs are massive photovoltaic power plants, such as the Olmedilla plant in Spain, which can crank out 60 MegaWatts of power. However, a massive project in California is expected to begin sometime this year in the Northwest California valley. The Topaz Solar Farm is expected to be fully operation by 2013 and produce a whopping 550 MegaWatts of power, and roughly 1100 GigaWatt-hours of perfectly renewable energy. Clearly, the photovoltaic industry is growing at a rapid rate, and is likely to become the dominant source of electricity at some point in this century.
Concentrating Solar Power takes a slightly different angle from the photovoltaic cells. CSP essentially uses large arrays of mirrors to focus sunlight onto a single point. Sometimes this concentrated sunlight is directed onto photovoltaic module, but the vast majority of the time, it is simply used for its thermal energy. The mirrors all focus sunlight onto a single reservoir of a working fluid, oftentimes simply water. the water is then heated, creating steam, which can then activate massive turbines, creating electricity. This process is called solar thermoelectricity. Currently, the Solar Energy Generating Systems (SEGS), a cluster of nine plants in the Mojave Desert of California, spanning 1600 acres, is the largest solar power plant in the world. It is capable of cranking out 354 MegaWatts of power and powers 232,500 homes. Furthermore, as the technology of CSP improves, it is clear that solar power will soon dominate the electricity needs of mankind.
Solar power looks pretty darn impressive, to be blunt. It is virtually completely renewable, and very efficient. However, it does have some drawbacks. For one thing, it is an intermittent energy source, meaning that it is not available 24/7. Obviously, the sun is only available half the time, as only one half of the earth can face it at a time. Furthermore, it is significantly less effective when it is cloudy, or direct sunlight is otherwise obstructed. However, methods are being developed to predict periods of highest efficiency, thus preventing time and energy from being wasted. Also, other methods are being devised to store energy during times of ample sunlight to be saved for a rainy day, to use a truly atrocious pun, if I may. Another drawback is the sheer cost. PV cells are downright expensive to install. However, after the initial installation, maintenance is fairly minimal. Also, many governments are creating incentives to create "green energy" sources in various communities, making solar power more readily accessible to regular suburbanites. A third drawback is the fact that all photovoltaic cells, the kind that can be most easily used by the aforementioned suburbanites, can only create direct current electricity. Naturally, this DC electricity must be converted to alternating current electricity through a power inverter, which leads to lowered efficiency, more complex machinery, and unfortunately a loss of energy, simply to make it usable in homes, as everything from microwaves to curling irons run off alternating current. However, I personally feel that solar power rises high above its few drawbacks, and certainly has the potentially to become the leading source of energy in the world of the future.
