The world will be facing energy shortages and increased pricing within the next few decades. Currently, the United States relies on coal, natural gas, petroleum and other non-renewable resources for over 75% of its electrical generation.
Solar power– The New Energy Resource
With decreasing stores of fossil fuels and increasing demand for electricity, it is obvious that a new energy source is needed. Solar power is that energy source. Although solar power has been emerging on the market since the 1800s when factories used the sun to heat water to create steam that turned turbines, it was not until the discovery of the photovoltaic effect in 1839 that the potential for solar development opened up. In 1883, Charles Fritz manufactured the first solar cells out of selenium. However, our current solar photovoltaic (PV) cells are made from silicon, a technology that was developed in 1954. It was then that the possibilities for large scale PV solar power became possible.
Solar Energy – Lowering CO2 Emissions
It is important to note that in the short term, solar energy is not going to displace our dominant energy source of fossil fuels in the next few decades. All our current infrastructure and modus operandi are too deeply ingrained in fossil fuels to make an abrupt separation. But it can contribute significantly to our needed energy mix to lower CO2 emissions and address climate change solutions. However, in the long term, solar energy is the one proven source that can safely and sustainably keep up with our progressing world.
Commercial Solar Energy
Commercial solar energy generation relies on solar thermal power systems which require concentrating sunlight to achieve high temperatures (think using a magnifying glass to light paper on fire). Some examples of this are parabolic dish systems, power towers, solar chimneys, and trough concentrators. There are advantages and disadvantages to each depending on the intended output desired and the amount of land area needed to maintain said system.
Residential solar energy
Residential solar energy is a different animal entirely and uses mainly photovoltaic (PV) systems, passive solar, and solar domestic hot water. This blog’s intended audience is residential so we will be focusing our attention there.
Solar Hot-Water Systems
Hot water heating accounts for some 20% of the energy used in a typical American home. The ease that existing hot water systems can be retrofitted to solar heating puts it at an exceptionally good advantage for residential use. Solar hot-water systems are feasible in any climate through various storage systems, flat-plate collectors, and heat exchangers. Systems can be as simple as a storage tank with glass on one side to more complex piping that runs in ceilings and flooring providing not only hot water but also active solar heating for your home. In the U.S., the receptivity for this form of solar energy replacement is very low. However, it is thirty times more prevalent in Australia and is now required in all new construction and renovation in Barcelona.
Passive Solar Building Designs
There are many forms of passive solar building designs all of which begin with building orientation. In the northern hemisphere, building your home with most of the windows on the south-facing aspect can provide considerable solar gain on sunny winter days. The north-facing wall should have little or no windows because of the glass’s low insular value. Having high R-value insulation is the next component. An R-value is a rating system designed to describe how well insulation performs at keeping heat from entering or leaving your home. After the sun warms up the interior of your home the insulation should keep it in. Some sort of thermal mass is required to store the excess energy and allow for slow release during the nighttime hours. Generally, this is in the form of a dark concrete floor inside the glass on the south-facing windows. The concrete takes considerable time to heat and cool and so provides an even temperature throughout the day. A roof overhang is necessary to block the more intense rays of the summer sun.
Photovoltaic (PV) Solar Panels
Photovoltaic (PV) solar panels have come a long way since 1954. The efficiency of those first panels was about 2% with an energy cost of roughly $1785/ watt. Solar panel efficiency is the measurement of irradiation, or the amount of solar energy that falls on a panel, that can be converted into electricity. The PV panels that are in production now are between 16% and 23% efficient. In laboratory settings, efficiency as high as 44% has been achieved but this has not been transferred into production level. PV solar panels are allowing homeowners to supplement electrical energy from the main power grid. All over the world, typical homes can rely on PV power to supply most of their electrical needs. Although some grid power may be needed on cloudy days, it is more prevalent to make excess power that can be sold back to the grid or stored in batteries.
One of the most commonly stated issues with PV power is the amount of energy lost during conversion. PV cells produce direct current (DC), and grid power is run by alternating current (AC). This means that for you to use the energy your PV cells generate it must be converted with an additional loss inefficiency. However, inverters are now available to convert DC to AC at about 95% efficiency. Also, no energy source comes without some environmental impact; PV’s are no exception. However, despite the waste that is inevitable during manufacturing and again with eventual disposal, the production energy required to produce PV’s does not exceed the amount of energy the PV itself will generate. This is known as the energy payback time. A typical PV system has a payback time of about two years. Meaning that the total energy budget for a PV system with a 30-year life span is around 93% pollution-free.
Solar energy is so abundant and environmentally friendly it would stand to reason that it should be more widely available. Unfortunately, the problem is one of economics. With today’s fossil fuel technologies being backed by government subsidies, “dirty” energy can be sold at a much lower capital cost. Value judgements are the controlling factor in this equation. Individuals must decide: do I value cheap energy or clean energy and what are the long-term effects of that decision? It is clear one way or the other that humans have a long history of harnessing the heat and power of the sun. From the ancient Romans and their burning mirrors to the Anasazi’s south facing cliff dwellings it is obvious that human civilization would not be what it is today without progressing solar technologies.