Excuse me, are you going to use all that Sun in one place? Given present-day concerns about energy independence, pollution control, and energy price stability, solar energy is often touted as one of the (at least partial) solutions to that problem. Solar energy involves making electricity or other useable energy out of light from the Sun. And while humans have been using solar energy on some level since before history, most applications including solar cells (photovoltaics) and other efficient conversion systems have only been in use since the late 1940s. As of 2005, the total share of domestically produced electricity from solar energy was very small at 0.065%, or a total of about 19 billion kilowatt-hours, but growing rapidly.
Solar energy is a seductive technology. Every other option we have for harnessing energy involves consuming a resource that will one day be gone, or could be if not properly managed. Solar energy is ubiquitous--immediately impacting the lives of everyone, whether or not we use it for electricity. Everyone around the world is as familiar with sunlight as an energy source as we are with burning wood.
I believe it is valuable here to reiterate how solar energy works for the perspective of this analysis. Solar energy can be generally divided into two groups: thermal and photovoltaic. Thermal solar energy at the small scale includes things like residential solar water heaters or the greenhouse effect helpfully warming your automobile in the winter. These things work because radiation from the sun in the form of light (ultraviolet, visible, and infrared) is absorbed by various materials causing them to increase in temperature. The examples used that heating effect as their end goal, but other systems including solar concentrator power plants use that heating effect to drive turbines and generate electricity.
Photovoltaics operate on another principle. Photons of light from the sun excite individual atoms in a semiconductor resulting in the flow of electrons therefore the generation of electricity. Depending on the base and doping materials utilized, the solar cells are tuned to particular wavelengths of light. Research is ongoing to broaden the spectrum of light that will activate solar cells and thus increase their efficiency.
The general drawbacks to capturing solar energy are predominately related to cost. The materials used to construct solar power equipment are expensive. Some like to comment here on the relatively low efficiency of solar power being that commercial photovoltaics are only about 9% to 14% efficient. Thermal solar power can be a little more efficient, about 20%. That is typically compared to a combined cycle natural gas turbine, which will have an efficiency of up to 60%. The thermodynamic efficiency of an internal combustion engine in an automobile would be around 26%. The values between solar and fossil fuels are not comparable, however. The reason doesn't come down to pollution, although that is a very important factor to be discussed later. The reason comes down to the nature of the energy input. Sunlight being free to everyone is a part of the environment that will be present whether we utilize it for electricity or not. Fossil fuels on the other hand are consumable resources that have a production cost as well as a market cost, and will eventually be eliminated, which is another factor
Distributed solar power includes devices installed on homes and smaller commercial buildings. Typically these are all photovoltaic devices placed on the roof or other flat structures. We could also include solar water heaters in this category. Homes and buildings that use solar power sources still need other power sources and therefore the overall power grid and generation systems, since solar is not 100% available. So, we do not save much in overall infrastructure costs, by going to this method, although overall fewer centralized power plants would have to be built in the long run. Distributed power systems also typically face more severe price pressures on initial costs versus life cycle costs: the average homeowner would usually settle for less capacity or less efficiency when building a home as compared to the systems employed by a commercial operation in a concentrated approach. Additionally, maintenance over the long run, which would help sustain a certain level of efficiency from a system, would not be as attentive overall with the whole population of small power producers including homeowners and office managers as it would be with a centralized system.
Centralized solar power (large scale solar power plants) seems to be making a popular comeback. This type of generation system is managed by public or private utility companies who construct large power plants made of photovoltaics or solar radiator concentrators in sunny, dry places like Arizona and the California desert. As large corporations, these enterprises can invest in the best technology and implement it on a large scale and keep up the necessary maintenance to gain maximum efficiency from their investment. Centralized solar power therefore, is more efficient per dollar invested than distributed solar power. That level of efficiency requires large investments in land and construction costs, and the efficiency may be affected by the distance of the power plant from the populated area it serves. Also, concentrated solar power requires a large amount of land, much more than other power sources, since sunlight is not very concentrated in individual areas like coal. The more land you have, the more power you can generate.
So, how do we decide between centralized and distributed solar energy? How do we decide between solar and other forms of energy? For one, we need to appropriately price (convert to some meaningful dollar figure based on our demand for other things) our desire to maintain open, undeveloped spaces in the areas richest in sunlight. As the value we place on those spaces increases, the efficiency of concentrated solar power stations diminishes. Secondly, we need to appropriately price pollution from manufacturing, installation, operations, and decommissioning into the cost estimates of all forms of energy. Pollution affects the health of people and ecosystems and arises from producing solar cells, growing biomass, burning coal, and dismantling nuclear power plants. Lastly, we should reconsider how we place a value on the consumable resources themselves beyond short term supply and demand. Petroleum may be viable as a general energy source for the next 40 years, but then what will be do without it? Plastics, building materials, lubricants, and other useful things can be made from that same petroleum. When there are alternative sources of energy, is it wise to consume such a multiple use substance for primarily that single objective? Long term benefits to society should be taken into account when analyzing the relative benefits of solar and other sources of energy.