Also known as alternative energy, renewables utilize energy that renews itself inexhaustibly and can be harnessed to generate power that uses very little environmental impact. However, unlike non-renewable energy, like fossil fuels, renewable energy is not consistent (sometimes the wind blows, sometimes the wind doesn't blow) and relies on batteries to store the energy for off-periods,
Wind turbines are much like the old windmills, except that they are designed to generate electricity and not grind grain. Wind turbines are usually around 280 feet in height to take advantage of stronger winds by using longer blades and each can generate between 4-6 megawatts of energy, with some even hitting the 10 megawatt range. Texas holds the highest amount of wind turbines than any other state with a current total of 10,700! Wind turbines work when the wind turns their two or three-equipped blades that then spins a rotor. This rotor, connected along the main shaft within, spins a generator that generates electricity.
The downside to wind turbines is that if there is not enough consistent wind, the product may end up being costlier than the benefits. Wind turbines also disrupt migratory birds; with the blades killing them as they fly by. Go to any wind farm and you will see a scattered boneyard of birds because 140,000-328,000 die by wind turbines in North America every year. Furthermore, wind turbines are disliked by many people because they feel it disrupts the natural beauty of the landscape.
Tidal energy is the newborn in the renewables family and there are two main types of it: barrages and turbines, including turbine fencing. There are currently no tidal plants in the United States and few areas in the country could benefit from it, but not nearly as much as other parts of the world.
Barrages: The first tidal barrage was built in La Rance, France and the largest barrage to date being in South Korea- generating 254 megawatts. Tidal barrages can look much like a dam because it is a structure built across an ocean inlet or lagoon that forms a basin. As high tide comes, the basin fills and when the outgoing ebb tide occurs, the water is released through a channel that houses an electricity turbine system. Some barrages have this on both the incoming and outgoing tides. Barrages can, however, disrupt the surrounding ecosystem with migratory fish or disrupt species in estuaries getting caught in the basins. They also disrupt the natural landscape and recreational activities.
Turbines: Tidal turbines are like underwater wind turbines, with blades just as long. Because water currents are much stronger than wind, however, tidal turbines cost much more in materials because they have to withstand these current by being stronger and heavier. Tidal turbine fencing is simply a long fence row underwater with turbines attached in intervals along it.
There are two kinds of solar energy: passive and active. Passive solar energy is the ability to harness the sun's energy and use it as it comes with surrounding materials. So, think of a greenhouse or skylight window. Active solar energy, however, is the ability to harness the sun's energy, store it, and convert it into electricity. The best way to do this is by using photovoltaic cells (solar cells) built together within a module, which are usually then added to other modules on an array or panel. Solar cells are built with a semiconductor material like silicon that has been treated with a positive charge on one side, and a negative charge on the other. When light energy penetrates these cells, electrons are released from their atoms in the silicon; attaching themselves to the electrical conductors. This then generates the electricity that can be used directly or stored in batteries.
These were first used in the 1960's for space exploration and then became a domestic product in the 1970's. As technology has advanced over the decades, this product has become cheaper and cheaper. It has also allowed for more varied types of solar energy like photovoltaic cells that are so thin, 1/100th the width of a human hair, that they can rest on a soap bubble. These will be integrated into wearable electronics, aerospace, and architecture.
The downside to solar cells is that you still cannot simply slap a panel or two on your roof and power your whole home; it takes many of them to get the job done. An average solar panel creates 250 watts of energy, and if the average household consumes 11,000 kWh of electricity per year, then that house would need 28-34 solar panels to do the job. Many times, households and businesses will supplement a percentage of their non-renewable energy with solar energy to mitigate it a little. The other downside is that it's not always sunny, especially in cloudier regions like the pacific northwest in the United States or parts of northern Europe. The batteries connected can store this energy for nighttime and the occasional rainy day, but unfortunately these are best used in sunnier regions like Hawai'i, the southwest United States, or Africa.
This is one of the oldest form of renewable energy that we have been using for thousands of years, ranging from water wheels to dams, and is currently the most used form of alternative energy in the world. Second to fossil fuels, it provided 16% of the world's electricity with 950 gigawatts; 24% of this came from China, eight percent from the United States, and nine percent in Brazil. Hydroelectric energy has globally doubled since 1970. Since natural water sources differ in different regions, so too does the effect of hydroelectric energy. For example, over two-thirds of the energy generated in Oregon and Washington comes from hydroelectric dams, whereas it's much less in places that don't contain as many sources.
Hydroelectric energy works by the volume and force of water hitting a turbine that powers a generator. The more the drop, the more energy generated from the turbine. Generally, one gallon of water per second that falls 100 feet will generate one kilowatt of electricity. Dams are built to control and raise the amount of water hitting the turbine by collecting it and then releasing it through a pipe to create the drop. The three main types of turbines used at hydropower stations are: Kaplan, Francis, and Pelton, each with their unique difference for different effects. The downside to hydroelectric energy is that they require a lot of construction that can damage surroundings, they can flood the area, mitigate the flow downstream which harms plants and animals, and they can disrupt the migration of fish like salmon whose migration has reduced by 90% because of dams. In South America, 80% of hydroelectric potential is in rain forests where some of the most diverse ecosystems exist; threatening the natural habitats for many of these beings. However, more fish-friendly turbines are being created and implemented as fish passage technologies are advancing.
Geothermal (geo = of the Earth, thermal = heat) is energy utilized by the natural heat from below the Earth's surface. This is another ancient form of energy in some areas of the world that has been used for heating and cooking (try eating buried bread in Iceland that was baked using geothermal heat under the Earth. It's really good n' smoky!). The concept with geothermal power plants is that the steam and hot water is tapped by drilling holes to access it. This steam is what turns the turbine and thus, the generator for electricity. Now, there are three types of power plants: binary, dry steam, and flash. In binary, the hot water is transferred into a secondary source of water that is below boiling point. This secondary water instantly turns into vapor at contact and this vapor turns the turbine. Dry steam utilizes steam emitted from fractures in the earth to spin the turbines. Flash is similar to binary, except that the secondary water is much colder and with less pressure. Binary is the most popular form and emits nearly no emissions, however, it does release hydrogen sulfide which gives off a rotten egg smell.
A homeowner could power their house more directly with their own geothermal heat pump. There are two main types of heat pumps: closed-loop and open-loop, depending on climate, soil conditions, and installation costs at that location. The most commonly used kind is the closed-loop which pumps a refrigerant through copper tubing buried under the ground, to drive the Earth's temperature. These can be installed underground vertically or horizontally, depending on the size of the yard.
The oldest known renewable resource is biomass or, more commonly known as, firewood. Pagans have been using biomass for thousands of years to generate energy for our homes and our rituals. Biomass consists of plant material and animal waste that is then burned. When plants are used as biomass, they release the carbon dioxide that they had stored during photosynthesis and had turned into carbohydrates. When animal waste is used as a biomass, it releases methane gas. The benefit of using biomass as a form of alternative energy is that the plants can regrow quickly and the animal waste can be collected from livestock pens that are already operating for the meat and dairy industries.
Unfortunately, biomass, though a renewable resource, does not compare in cost to other forms of renewables today. It also takes up agricultural land that could otherwise be used for food, requires water, contributes to deforestation to provide the land, and still releases carbon dioxide and methane into the atmosphere. So though it is renewable, it is not the cleanest option for alternative energy.
Like a cousin to tidal energy, wave energy is also new to the family of renewables. A lot of its testing is done off the coasts of Scotland with its Atlantic waves and the North Sea's. However there are implemented sites such as the one off the coast of Northern Portugal and Australia's Carnegie Wave near Perth. Oregon just received some funds from the government in early 2018 to boost their wave testing project, but all in all, wave energy today is like what wind energy was 25 years ago; still trying to achieve enough funding for research from backed companies and still trying to decide on the best designed structure. Some designs for harnessing wave energy comes in the form of snake-like attenuators, bobbing buoys, devices mounted on the ocean floor that exploit differences in pressure as a wave passes by, and so on. However, if this renewable can be perfected, it is estimated to supply the U.S. one-fourth of its total needed energy, just from the west coast alone!
The downside to wave energy is that it can be disruptive to marine animals, might cause pollution depending on the stability of the material in seawater, disturbs private and commercial vessels, and alters the view of the sea.