Energy

Solar Energy - Upload Knowledge

Solar energy is energy directly from the sun and it’s one of the cleanest renewable energy sources we have because using it generates no direct greenhouse gases or other pollutants! Solar energy technologies can take many forms and produce electricity, heat, light or a combination of these. And despite what some may claim, solar energy could meet demand on any scale even though it wouldn’t have to fulfill all our needs if we had a diverse mix of renewable energy technologies working together. According to the National Renewable Energy Laboratory, an area covered by solar photovoltaic modules 110 by 110 miles in dimension could supply all the electricity we use in the United States.

The good news is that solar energy technology is not the isolated industry that it once was. It’s here, it’s viable, and there is a growing market for it. According to the DOE, the photovoltaic market alone has grown more than 35% per year over the past two years, and the industry as a whole has undergone a fundamental shift from isolated, off-grid applications to nearly 60% grid-connected and distributed power. Even concentrating solar power is becoming increasingly more available and cheaper. The DOE reports that it will become competitive with traditional power plants within a decade.

Solar energy is becoming more cost effective every year, and with federal and state investment incentives, it’s a great time to consider installing some form of solar technology at your school! According to DSIRE, 48 states have financial incentives for installing solar or another renewable energy. Some of the attractive incentives for solar include rebates, sales tax or property tax waivers, and investment credits.

Did you ever wonder how energy comes from the sun in the first place? Learn more about the sun’s energy from APS Project Sol.

You can also learn about the history of humans using the sun’s energy by checking out this cool site by the U.S. Department of Energy. They outline the history of solar technology from when it was probably first applied in the 7th Century B.C. with glass concentrating sunlight to make fire.

One of the most exciting aspects of solar technology is that it can take many forms. As we explain these below and you click on various links, you might find this Solar Glossary of Terms by DOE helpful.

The one most people usually think of when they think of solar power is solar panels on houses and buildings that produce electricity. This is called Photovoltaic Technology or PV, and it converts sunlight directly to electricity by means of PV cells made of semiconductor materials. PV is a popular type of solar technology because it’s modular, meaning that it produces electricity by a number of small panels all put together. These panels which can be added to or moved around, make it easy to meet specific size needs for specific applications. This link to PV Technology by the DOE offers explanations of how it works, why it’s important, why it’s used, and how you can learn even more about PV if you can’t find what you’re looking for on their website. Another cool site from the DOE offers an easy-to-understand explanation of how exactly PV works to produce electricity.

Another form of solar technology used to produce electricity is Concentrating Solar Power, also called CSP systems. They produce electricity usually on a greater scale than PV technology. Concentrating Solar Power is used more like a power plant. Instead of producing electricity directly like PV, it first concentrates the sun’s energy using troughs or mirror panels to produce heat Then, in a second step, that heat is used to produce electricity by producing steam similar to the way traditional power plants operate. Because of the large scale of Concentrating Solar Power compared to other solar technology applications, CSP requires a more reliable supply of sun. Many people think that all solar technologies have to be used in the South Western United States to be worthwhile. However, this is simply not true except when talking about massive CSP facilities, which do require a widespread and dependable sun source. To see which areas of the United States receive various amounts of usable sunlight, check out the Solar Maps supplied by the National Renewable Energy Laboratory.

Besides producing electricity, solar technology also has more passive applications. One of these is Solar Heating, which can take many forms, including water heating for a building space heating, and even space cooling. Check out the DOE’s site on Solar Heating, and also the NREL’s site on Solar Process Heat, which explains some of the special solar heating technologies large buildings like schools can take advantage of that are not practical in smaller applications.

Another passive solar technology is Solar Lighting, which includes simply using daylight for indoor lighting needs through special fixtures, and includes more developed technologies such as hybrid solar lighting that combines the power sunlight with electricity in meeting lighting needs. Solar Lighting Technology has a huge impact on our environment because right now a third of the electricity used by U.S. consumers is used for lighting.

For more about each of these different technologies, check out How Solar Energy Works from the Union of Concerned Scientists. Also check out the DOE’s Solar FAQs, which explains questions you may have about solar power and helps you to sort out confusion about the different technologies. For a great list of solar organizations providing educational resources, check out this page of links from NOVA. Don’t forget to use the Solar Glossary of Terms as you go about your research. And finally, if you want to ask an expert a question about solar energy technology from any of the Department of Energy links, check out the their Ask the Expert Function.

Pros—

The best aspect of solar energy technology is that as it produces electricity, provides direct heat, or lights your building, it doesn’t directly release any greenhouse gases or other atmospheric emissions. The DOE reports that in a year’s time, each kilowatt of PV electricity offsets 9 kilograms of sulfur oxides, 16 kilograms of nitrogen oxides, and 2,300 kilograms of carbon dioxide!

Of course, with any of the renewable energy technologies there are some greenhouse gas emissions at some point in the process of manufacturing the equipment or developing the infrastructure. Solar energy is no exception. A good way to measure how much environmental impact and economic cost goes into creating the equipment for a renewable energy source is by measuring the energy it takes to create it, and then measuring how long it takes for the resulting clean energy to offset the energy it took to create the equipment. This is called the energy payback period and according to the DOE, solar energy’s payback period is dropping rapidly. Today’s crystalline silicon module PV technologies take only four years to produce more energy than went into making them. And upcoming silicon module technology will have an energy payback after only two years. Since PV systems last an average of 30 years, they result in at least 26 to 28 years of completely clean energy! The DOE reports that even a solar water heater system, which has a less productive payback than other solar technologies, produces two times as much hot water per unit of fossil fuel energy invested as a natural gas water heater, and four times as much hot water as an electric water heater.

Solar energy systems are also convenient. Solar power has so many diverse applications that it can be used in varying areas across the United States with varying amounts of available sunlight. PV technology, in particular, is also flexible in how it can be applied to various building styles and sizes, or really using any available area because it’s modular. The DOE explains that vacant land, parking lots, and rooftops could all be used. If they were built in all 5 million acres of the "brownfields,” which are abandoned industrial sites in U.S. cities, they could supply 90% of our current electricity needs. PV systems are also convenient in that they produce the most power during the day at peak daylight hours, which is when utilities need to provide the most power. Photovoltaics are also more dependable than traditional electricity generating systems because when there is a failure in one piece of the modular system, it usually doesn’t affect other modules, which can continue to produce electricity.

Another huge positive for solar energy is that it’s economically viable. The DOE reports that the U.S.-based industry of PV modules is now a $2.5 to $3 billion market, providing 25,000 jobs. But, it’s expected to grow even more to a $10-$15 billion market, providing 300,000 jobs by 2025. As the industry grows and produces more American jobs, prices will also continue to drop. The DOE reports that the price per peak watt has dropped from $50 in 1980 to $3 now. And according to the U.S. PV Industry Roadmap, it will continue this trend until it becomes competitive for most domestic markets by 2010.

Cons—

One of the predominant criticisms of solar energy is of the manufacturing process of the parts. Some people are concerned with how much and what kind of raw materials are used to make solar panels, how safe or unsafe the manufacturing process is, as well as how they are installed, and eventually disposed of. The DOE explains how producing the semiconductors for PVs involves using chemicals and some toxic materials. The Union of Concerned Scientists explains that these materials, especially arsenic and cadmium used for photovoltaic cells, can create health and safety hazards for manufacturing employees. Silicon is the major ingredient for PV cells, and it too can be hazardous if it’s breathed in as dust. Besides the dangers of manufacturing, there is also a small environmental health threat from these materials creating hazardous fumes if they are burned with a house or building. However, the Union of Concerned Scientists explains that none of these hazards are much different from other common dangers in our industrial world. Furthermore, they are regulated heavily by strong safety measures, and the DOE adds that production of PV cells is essentially the same process as the traditional semiconductor industry. The EPA has conducted safety tests and found no problems with the process.

Another concern with solar power technology is that it takes a significant amount of space to produce power on a large-scale. According to the Union of Concerned Scientists, it takes about one square kilometer to generate every 20-60 megawatts (MW) of energy. Issues arise with how this land use affects natural territory and native wildlife. However, the Union of Concerned Scientists is quick to point out that this problem is not unique to solar energy production. And in fact, traditional power sources, such as coal, actually require significantly more land per unit of energy delivered when strip mining land is factored into the equation. Land use issues also arise with solar-thermal plants because they require cooling water to operate their systems and this may be scarce in desert areas. However, traditional power plants also require cooling water. Also keep in mind that large scale power plants are usually not the preferred method of solar electricity generation anyway. The industry is much more strongly focused on small PV applications, which are more promising as they take better advantage of the dispersed, intermittent quality of sunlight as a resource. They also can fit on existing structures and therefore don’t have to use undeveloped land.

Similar to geothermal, the solar industry is in a sensitive state right now. There is a lot of potential for solar energy systems to break through and be an even greater energy force in our economy. However, the Union of Concerned Scientists explains that there are relatively few units of solar energy systems being produced and as long as this continues to happen, prices will stay high. High prices mean low demand and low production volumes. Even though DOE reports that prices are getting lower all the time, they still need to drop more. The DOE explains that the industry also needs more investments for these technologies to make potential improvements and push forward. Now is the time to invest, and if we delay, the DOE says there will be a loss of ownership and leadership over the new technologies. The industry needs help now from the government and private investors if we want to enjoy all the environmental benefits of solar technology in the future.