The Canada Tar sands, the Keystone XL pipeline are something I’ve been hearing something about, but I haven’t known what they were talking about. Now I do. Large groups of people have been protesting this and for good reason.
Biogas, also known as biomenthane, swamp gas, landfill gas, or digester gas, is produced through the anaerobic digestion (fermentation) of decaying plant or animal matter. It is the naturally occurring emission of bacteria that thrive without oxygen, and occurs in three steps. First is the decomposition, or hydrolysis, of the biodegradable material into molecules such as sugars. Next, these molecules are converted into acids. Lastly, the acids are converted into biogas. Anaerobic digesters harness the bacteria’s natural processes to capture and utilize the biogas, all in a safe, controlled environment.
Biogas can be produced from a wide variety of available organic materials and wastes, including sewage sludge, animal manure, municipal/industrial organic waste, stillage from ethanol production, crop residues, and specially grown energy crops.
Normally, they take these products and make fertilizer and the gas is just byproduct that is released. But if we obtain the fuel first, we can prevent runoff and methane emissions. Then the residue created by the burning of biogas can be dried and used as fertilizer.
Landfills are the third-largest source of human-related methane emissions in the United States. Methane can be captured from landfills and used to produce biogas. Methane gas collection is practical for landfills at least 40 feet deep with at least 1 million tons of waste.
The U.S. Environmental Protection Agency (EPA) estimates 8,200 U.S. dairy and swine operations could support biogas recovery systems with the potential to generate more than 13 million megawatt-hours and displace about 1,670 megawatts of fossil fuel-fired generation collectively per year. Biogas recovery systems are also feasible at some poultry operations.
I love this idea. As gross and unsanitary as it sounds, biogas would be our solution to both our problem of needing a renewable energy and it helps solve our huge waste problem. Before I get too excited, let’s look at the specifics.
Biogas is usually 50% to 80% methane and 20% to 50% carbon dioxide with traces of gases such as hydrogen, carbon monoxide, and nitrogen. In contrast, natural gas is usually more than 70% methane with most of the rest being other hydrocarbons (such as propane and butane) and traces of carbon dioxide and other contaminants.
Carbon is also a problem. When it burns, it turns into lots of carbon dioxide gas. Gasoline is mostly carbon by weight, so a gallon of gas might release 5 to 6 pounds (2.5 kg) of carbon into the atmosphere. The U.S. is releasing roughly 2 billion pounds of carbon into the atmosphere each day.
Compressed biogas (CBG) is the most climate friendly of more than 70 different fuels and is considered to be CO2 neutral.
And since the conversion process in the digester is anaerobic (it occurs in the absence of oxygen), it destroys most of the pathogens present in dung and waste, thereby reducing the potential for infections like dysentery and enteritis.
The burning of traditional fuels like dung cakes or wood (this article was written about India. That is why they say dung is a traditional fuel) releases high levels of carbon monoxide, suspended particulates, hydrocarbons, and often, contaminants like sulfur oxides. Because it is a gas, biogas burns much more efficiently than these solid fuels. It leaves very few contaminants, although it is true that biogas releases small quantities of sulfur oxides. Biogas offers perhaps the most environmentally benign method for tapping the solar energy stored in bio-mass. It’s a renewable and decentralized alternative to the other methane-based fuel, natural gas, which is commonly used in cities.
Methane, which I talked about in my landfill effects post, is explosive if it isn’t burned. (I saw this when I was working on my summer class project. My video was already way too long, so I didn’t add the stuff about methane and leachate, but here is a picture).
This stuff could be used, but usually it is just burned, so it’s just wasted.
Biogas reduces emissions by preventing methane release in the atmosphere. Methane is 21 times stronger than carbon dioxide as a greenhouse gas. It also saves money because it means that landfills don’t have to worry about complying with EPA combustion requirements. Producing biogas through anaerobic digestion reduces landfill waste and odors, produces nutrient-rich liquid fertilizer, and requires less land than aerobic composting.
As far as cons go, when it is compared to gas, it doesn’t seem like a bad solution. I didn’t find any talk about animals or habitats being affected, so that’s always good. But there wasn’t a whole of information on this subject, in general, so it may not be popular enough to have a whole lot of research. If not monitored responsibly, some problems could arise though.
Biogas can accumulate under roofs and ceilings. Carbon Monoxide gas can gather in engine exhaust and poorly operating boilers. And hydrogen Sulfide gas, which can collect in the bottom of tanks and pump sumps, can kill almost instantly.
Biofuels. The term invokes a life-giving image of renewability and abundance—a clean, green, sustainable assurance in technology and the power of progress. This image allows industry, politicians, the World Bank, the United Nations, and even the Intergovernmental Panel on Climate Change to present fuels made from corn, sugarcane, soy and other crops as the next step in a smooth transition from peak oil to a yet-to-be-defined renewable fuel economy. Drawing its power from a cluster of simple cornucopian myths, “biofuels” directs our attention away from the powerful economic interests that benefit from this transition. It avoids discussion of the growing North-South food and energy imbalance. More fundamentally, it obscures the political-economic relationships between land, people, resources and food. By showing us only one side, “biofuels” fails to help us understand the profound consequences of the industrial transformation of our food and fuel systems—The Agro-fuels Transition.
Because photosynthesis from fuel crops removes green house gases from atmosphere and can reduce fossil fuel consumption, we are told fuel crops are green. But when the full “life cycle” of agro-fuels is considered—from land clearing to automotive consumption—the moderate emission savings are undone by far greater emissions from deforestation, burning, peat drainage, cultivation, and soil carbon losses. Every ton of palm oil produced results in 33 tons of carbon dioxide emissions—10 times more than petroleum. Tropical forests cleared for sugar cane ethanol emit 50 percent more greenhouse gasses than the production and use of the same amount of gasoline. Commenting on the global carbon balance, Doug Parr, chief UK scientist at Greenpeace states flatly, “If even five percent of biofuels are sourced from wiping out existing ancient forests, you’ve lost all your carbon gain.”
Fertilizers are another problem. We now use globally over 45 million tons per year through agro-fuel industry. They’re petroleum based and has more than doubled the biologically available nitrogen in the world, contributing heavily to the emission of nitrous oxide, a greenhouse gas 300 times more potent than CO². In the tropics, where more and more of our food being grown, fertilizer has 10-100 times the impact on global warming compared to temperate soil applications. To produce a liter of ethanol takes three to five liters of irrigation water and produces up to 13 liters of waste water. It takes the energy equivalent of 113 liters of natural gas to treat this waste and increases the likelihood that it will simply be released into the environment to pollute streams, rivers and groundwater. Intensive cultivation of fuel crops also leads to high rates of erosion, particularly in soy production—from 6.5 tons/hectare in the U.S. to up to 12 tons/hectare in Brazil and Argentina.
According to the FAO, there is enough food in the world to supply everyone with a daily 3,200-calorie diet of fresh fruit, nuts, vegetables, dairy and meat.
And actually, something else that I learned, although it’s not completely related to biofuels is that industrialized and developing countries actually waste about the same amount of food which around 670 and 630 million tons. The difference is at what level in the food supply chain the waste occurs. For industrialized countries, a lot of waste is at the retail and consumer level. Translation: people and stores throwing it away because it’s not pretty enough. It’s still perfectly edible, but not perfect enough. In developing countries it’s mostly at the postharvest and processing level. Translation: Stores and people are tossing perfectly edible food, versus food spoiling before it even gets to the store due to limitations in transit/storage/processing.
Nonetheless, because they are poor, 824 million people continue to go hungry because food and fuel crops are competing over land and resources, high food prices may actually push up fuel prices. Both increase the prices of land and water.
They’re discussing replacing present agro-fuels made from food crops with ‘environmentally-friendly’ crops like fast-growing trees and switchgrass.
The agro-fuel transition transforms land use on massive scales, pitting food production against fuel production for land, water and resources. The issue of which crops are converted to fuel is irrelevant. Wild plants cultivated as fuel crops won’t have a smaller “environmental footprint” because commercialization will transform their ecology. They will rapidly migrate from hedgerows and woodlots onto arable lands to be intensively cultivated like any other industrial crop—with all the associated environmental externalities.
By genetically engineering plants with less lignin and cellulose, the industry aims to produce cellulosic agro-fuel crops that break down easily to liberate sugars, especially fast-growing trees. Trees are perennial and spread pollen father than food crops. Cellulosic candidates miscanthus, switch grass, and canary grass, are invasive species. Given the demonstrated promiscuity of genetically-engineered crops, we can expect massive genetic contamination. Monsanto and Syngenta will be quite pleased. Agro-fuels will serve as their genetic Trojan horse, allowing them to fully colonize both our fuel and food systems.
The relation between agriculture and industry that began with the Industrial Revolution. The industry’s take-off lagged until governments privatized common lands, driving the poorest peasants out of agriculture and into urban factories. Peasant agriculture effectively subsidized industry with both cheap food and cheap labor. Over the next 100 years, as industry grew, so did the urban percentage of the world’s population: from 3% to 13%. Cheap oil and petroleum-based fertilizers opened up agriculture itself to industrial capital which lead to mechanization intensified production, keeping food prices low and industry booming. The next hundred years saw a three-fold global shift to urban living. The massive transfer of wealth from agriculture to industry, the industrialization of agriculture, and the rural-urban shift are all part of the “Agrarian Transition,” the lesser-known twin of the Industrial Revolution. The Agrarian/Industrial twins transformed most of the world’s fuel and food systems and established non-renewable petroleum as the foundation of today’s multi-trillion dollar agri-foods complex.
Agro-fuels lead us to overdraw. “Renewable” does not mean “limitless.” Even if crops can be replanted, land, water, and nutrients are limiting. Pretending otherwise serves the interests of those monopolizing those resources.
At first glance, like many alternative fuels, it may seem like a pretty reasonable answer for instance that it is an alternative for an insecure and exhaustible supply of fossil fuel. This may be true, but it replaces and insecure and exhaustible source for another.
Agrofuel production can reduce the dependency of developing countries on expensive import of fossil fuels, and improve their trade balance. This may be true, but at what cost. Most of these are raised in what used to be forests. Trees are much better for the land and the environment than just regular plants.
The feedstock used to make agrofuels is renewable – fresh supplies can be produced as needed. In theory, therefore, there is an unlimited and secure supply. In theory, yes, but eventually the nutrients will be gone, the water will harder to get, so on and so forth.
I could go on and on, but I think we’re getting the picture.
Back in 2008, Africa started a ‘sustainable’ biofuel crop growing program. “Agrofuels Africa ensures that its production of biofuel will have a positive effect on the greenhouse gas reduction, that the production will not affect protected or vulnerable areas, that no excessive use of water resources will be made, that the quality of soil, surface, ground water, and air will be retained, and that the food security situation of the local communities will improve.” This site is pretty simple. It doesn’t have any records or ways that they’re making sure nothing damaging happens. http://agrofuelsafrica.com/index.htm
Yesterday I talked about some background and the basics of geothermal energy. Today, it’s time to talk about the pros and cons.
Geothermal power plants do not burn fuel to generate electricity, so their emission levels are very low. They release less than 1% of the carbon dioxide emissions of a fossil fuel plant. They don’t have radioactive or ash wastes, particulates or other combustion byproduct, so there is no waste management involved or needed. Geothermal plants use scrubber systems to clean the air of hydrogen sulfide that is naturally found in the steam and hot water.
A few sites do produce some silica and sulfur dioxide, both of which are largely removed from the vapors and either returned to the hydrothermal well or processed and sold for industrial uses.
Almost 100% of the visible, airborne effluent seen rising from geothermal plants is water vapor.
Geothermal plants don’t have to transport fuel, like most power plants. Geothermal plants sit on top of their fuel source. Geothermal power plants have been built in deserts, in the middle of crops, and in mountain forests.
Geothermal plants emit 97% less acid rain-causing sulfur compounds than are emitted by fossil fuel plants. After the steam and water from a geothermal reservoir have been used, they are injected back into the Earth.
Geothermal reservoirs come from natural resources that are naturally replenished. Geothermal energy is therefore a renewable and reliable energy source. There are little to no fluctuations in the flow of energy. Geothermal power plants have a high capacity factor, so geothermal is an excellent candidate for supplying the base load energy.
Beneath our feet we have more usable geothermal energy resources than oil, coal, gas, and mineable nuclear fuels combined.
Geothermal Resource Council Data shown below compares global continental (not including deep ocean resources) geothermal energy resources to global oil reserves.
Units: Billions of barrels of oil equivalent
*Annual Global Energy Consumption—-70
*A Stanford University Wind Power Studyshows total annual global Btu consumption from all sources of about 50 to 70 billion barrels of oil equivalent.
Thermal aquifers are the primary source of geothermal electrical power using current technology. Those 130 billion barrels of oil equivalent masks the fact that geothermal resources are a form of nuclear power and can continue to provide those energy supplies year after year, decade after decade, century after century.
Once in operation, geothermal plants may be the most reliable of all energy production methods. Every plant that was built in the last 100 years ago is still running. Since they are fundamentally simpler than most other power systems, there is less to go wrong.
This article also says that scientists believe our geothermal resources will outlast the Sun. How they decided that and why it matters, I don’t know. Everything living depends on the sun, so geothermal energy will not help us on that point.
Geothermal energy has the smallest land use of any major power generation technology. A typical geothermal facility occupies about the same space as a gas fired plant of the same capacity. But the geothermal facility does not require miles of buried pipeline to carry fuel to keep it running.
The burning of this electricity doesn’t create pollution, but the collection part of it seems to create some problems. There is an abundance of greenhouse gases below the surface of the Earth, which may mitigate towards the surface and be released into the atmosphere. There can also be traces of heavy metals such as mercury, arsenic and boron. If waste is released into rivers or lakes instead of being injected into the geothermal field, these pollutants can damage aquatic life and make the water unsafe for drinking or irrigation. http://www.teara.govt.nz/en/geothermal-energy/5
Construction of geothermal power plants can affect the stability of the land. In fact, both in Germany and New Zealand, geothermal power plants have led to earthquakes. In January 1997, the construction of a geothermal power plant in Switzerland triggered an earthquake with a magnitude of 3.4 on the Richter scale. I read a comment on an article about this that said the reason that these plants are causing earthquakes is because the supply of energy isn’t replenished as quickly as it’s being collected. To back that up I found Earthquakes typically occur around unstable areas such as volcanoes, fault lines and geothermal regions. So, any area ripe for enhanced geothermal tinkering is already prone to get the shakes. On top of that, pumping water down to subteranian regions of heated bedrock causes the rock to expand and contract, fracturing the rock. As such, seismic activity isn’t just a side effect of the process, it’s a part of the process. The deeper the shaft, the greater the chance that increased levels of seismic activity could reach nearby fault lines, generating an even more powerful earthquake. http://science.howstuffworks.com/environmental/earth/geophysics/geothermal-energy-cause-earthquakes1.htm I also found that at the rate of current removal of power for production, they typically remove heat from natural reservoirs at over 10 times their rate of replenishment. This imbalance may be partially improved by injecting waste fluids back into the geothermal system, but they never say that this causes earthquakes.
Earthquakes can be triggered due to hydraulic fracturing, which is an important aspect of constructing enhanced geothermal system (EGS) power plants.
Also, I think places like Yellowstone with geothermal type features would be destroyed by the drilling. When the Wairākei geothermal field was tapped for power generation in 1958, the withdrawal of hot fluids from the underground reservoir began to cause long-term changes to the famous Geyser Valley, the nearby Waiora Valley, and the mighty Karapiti blowhole. The ground sagged 3 meters in some places, and hot springs and geysers began to decline and die as the supply of steaming water from below was depleted.
A commercial geothermal power project is expensive. Exploration and drilling for new resources carries a steep price tag. The costs usually end up somewhere around $2-7 million for a capacity of 1 MW. This is included drilling, which is accountable for over half of the expenses. The big key to universal use of geothermal resources is the development of deep, hot dry rock resources. The key to that is drilling technology. Due to the hot, often corrosive, environment of geothermal resource areas, drilling for geothermal resources is far more expensive than any other kind of drilling. Drilling technology is improving. Drilling costs, on average, have dropped by a fourth in the last two decades. As drilling technology improves, geothermal power plants could become universally available.
According to some sites, geothermal power costs are currently competitive with coal power plants, making them among the cheapest power providers around and getting cheaper with every project, but current cost figures are based on projects that are located at the best geothermal sites. The key to economically exploiting geothermal resources using current technologies is finding the best producing hydrothermal wells.
Initial cost of residential geothermal heating and cooling systems are also expensive and for individual homes it often more expensive than solar power. To be both usable and economical a site must have an adequate volume of hot water or steam that is not too impure to use, a surface water source to cool generating equipment, and close proximity to power transmission lines. So, even in promising areas, economically usable sites are few and they are difficult to locate. The U.S. Geological Survey Circular 790 estimates a hydrothermal resource base in the U.S. of between 95,000 and 150,000 MW (Megawatts), of which 25,000 MW are known resources.
While that is a significant amount, it’s roughly one fourth of our current electrical need, less if we start plugging our cars into the electric grid. And most of that geothermal resource is way out west. That’s good for the West Coast, Hawaii, and the few people who live in Alaska, but it falls far short of being able to serve our Nation or the world.
For those it’s available to, it can save them money years down the line, and should be looked upon as long-term investments.
Geothermal power plants have less aesthetics problems than other power plants.
Since they occupy the smallest space per kilowatt generated, it follows that they have the least visual impact of any power generation technology available.
If river water is used as a cooling medium, the entire power plant could be built underground or within structures already built for other uses.
Today, I’ll go over the basics of geothermal energy and tomorrow I will talk about the pros and cons.
There are four types of alternative energy that I remember learning about in school. I remember hearing about them as far back as fourth grade or so. Wind, solar, hydro, and geothermal. The first three I hear about quite a bit if not all the time and they seem to have evolved by leaps and bounds. But I don’t often hear about geothermal energy, so I was curious about how it has changed and whether it seems like reasonable alternative.
Geothermal energy was used by ancient people for heating and bathing. Even today, hot springs are used worldwide for bathing, and many people believe hot mineral waters have natural healing powers. I don’t know how many people have actually smelled one of those springs, but it doesn’t smell as pleasant as bowl full of roses. I am not totally sure if I am up for smelling that all the time, but I haven’t found any evidence that it is actually a side effect of collecting or burning geothermal energy, but honestly I don’t see how it couldn’t be.
Geothermal energy is the heat from the Earth. Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth’s surface, and down even deeper to the extremely high temperatures of molten rock called magma.
It turns out that the largest contributor to the heat below our feet is the decay of radioactive particles. We stand on nothing less than a planet-sized nuclear reactor that promises to continue generating heat for billions of years in the future. Now, that is a scary thought.
Almost everywhere, the shallow ground or upper 10 feet of the Earth’s surface maintains a nearly constant temperature between 50° and 60°F (10° and 16°C). Geothermal heat pumps can tap into this resource to heat and cool buildings. A geothermal heat pump system consists of a heat pump, an air delivery system (ductwork), and a heat exchanger-a system of pipes buried in the shallow ground near the building. In the winter, the heat pump removes heat from the heat exchanger and pumps it into the indoor air delivery system. In the summer, the process is reversed, and the heat pump moves heat from the indoor air into the heat exchanger. The heat removed from the indoor air during the summer can also be used to provide a free source of hot water.
Some geothermal power plants use the steam from a reservoir to power a turbine/generator, while others use the hot water to boil a working fluid that vaporizes and then turns a turbine. Hot water near the surface of Earth can be used directly for heat. Direct-use applications include heating buildings, growing plants in greenhouses, drying crops, heating water at fish farms, and several industrial processes such as pasteurizing milk.
The most common current way of capturing the energy from geothermal sources is to tap into naturally occurring “hydrothermal convection” systems where cooler water seeps into Earth’s crust, is heated up, and then rises to the surface. When heated water is forced to the surface, it is a relatively simple matter to capture that steam and use it to drive electric generators. Geothermal power plants drill their own holes into the rock to more effectively capture the steam.
There are three designs for geothermal power plants, all of which pull hot water and steam from the ground, use it, and then return it as warm water to prolong the life of the heat source. In the simplest design, the steam goes directly through the turbine, then into a condenser where the steam is condensed into water.
In a second approach, very hot water is depressurized or “flashed” into steam which can then be used to drive the turbine.
In the third approach, called a binary system, the hot water is passed through a heat exchanger, where it heats a second liquid—such as isobutane—in a closed loop. The isobutane boils at a lower temperature than water, so it is more easily converted into steam to run the turbine.
Enhanced Geothermal Systems. Geothermal heat occurs everywhere under the surface of the earth, but the conditions that make water circulate to the surface are found only in less than 10 percent of Earth’s land area. An approach to capturing the heat in dry areas is known as enhanced geothermal systems (EGS) or “hot dry rock”. The hot rock reservoirs, typically at greater depths below the earth’s surface than conventional sources, are first broken up by pumping high-pressure water through them. The plants then pump more water through the broken hot rocks, where it heats up, returns to the surface as steam, and powers turbines to generate electricity. Finally, the water is returned to the reservoir through injection wells to complete the circulation loop. Plants that use a closed-loop binary cycle release no fluids or heat-trapping emissions other than water vapor, which may be used for cooling.
It is one of the few renewable energy technologies that can supply continuous, baseload power. The costs for electricity from geothermal facilities are declining to as little as 50 percent in the last thirty years. A considerable portion of potential geothermal resources will be able produce electricity for as little as 8 cents per kilowatt-hour (including a production tax credit), a cost level competitive with new conventional fossil fuel-fired power plants. It is also becoming available directly for homes and businesses everywhere.
Today I’ll be talking about the history, the current system, and future ideas for hydroelectricity. Tomorrow I’ll talk about it’s pros and cons.
Hydropower is electricity generated using the energy of moving water. Rain or melted snow, usually originating in hills and mountains, create streams and rivers that eventually run to the ocean. The energy of that moving water can be substantial, as anyone who has been whitewater rafting knows.
This energy has been proving itself for centuries. Farmers since the ancient Greeks have used water wheels to grind wheat into flour. Placed in a river, a water wheel picks up flowing water in buckets located around the wheel. The kinetic energy of the flowing river turns the wheel and is converted into mechanical energy that runs the mill.
Hydroelectric power provides almost one-fifth of the world’s electricity. China, Canada, Brazil, the United States, and Russia were the five largest producers of hydropower in 2004.
The biggest hydro plant in the United States is located at the Grand Coulee Dam on the Columbia River in northern Washington. More than 70 percent of the electricity made in Washington State is produced by hydroelectric facilities.
Hydropower is the cheapest way to generate electricity today. That’s because once a dam has been built and the equipment installed, the energy source—flowing water—is free. It’s a clean fuel source that is renewable yearly by snow and rainfall.
Hydropower is also readily available; engineers can control the flow of water through the turbines to produce electricity on demand. In addition, reservoirs may offer recreational opportunities, such as swimming and boating.
Hydropower plants consist of these major components:
- Dam – Most hydropower plants rely on a dam that holds back water, creating a large reservoir. Often, this reservoir is used as a recreational lake, such as Lake Roosevelt at the Grand Coulee Dam in Washington State.
- Intake – Gates on the dam open and gravity pulls the water through the penstock, a pipeline that leads to the turbine. Water builds up pressure as it flows through this pipe.
- Turbine – The water strikes and turns the large blades of a turbine, which is attached to a generator above it by way of a shaft. The most common type of turbine for hydropower plants is the Francis Turbine, which looks like a big disc with curved blades. A turbine can weigh as much as 172 tons and turn at a rate of 90 revolutions per minute (rpm), according to the Foundation for Water & Energy Education (FWEE).
- Generators – The heart of the hydroelectric power plant is the generator. Most hydropower plants have several of these generators. The generator, as you might have guessed, generates the electricity. The basic process of generating electricity in this manner is to rotate a series of magnets inside coils of wire. This process moves electrons, which produces electrical current.
- Transformer – The transformer inside the powerhouse takes the AC and converts it to higher-voltage current.
- Power lines – Out of every power plant come four wires: the three phases of power being produced simultaneously plus a neutral or ground common to all three.
- Outflow – Used water is carried through pipelines, called tailraces, and re-enters the river downstream.
The water in the reservoir is considered stored energy. When the gates open, the water flowing through the penstock becomes kinetic energy because it’s in motion. The amount of electricity that is generated is determined by several factors. Two of those factors are the volume of water flow and the amount of hydraulic head. The head refers to the distance between the water surface and the turbines. As the head and flow increase, so does the electricity generated. The head is usually dependent upon the amount of water in the reservoir.
There’s another type of hydropower plant, called the pumped-storage plant. In a conventional hydropower plant, the water from the reservoir flows through the plant, exits and is carried downstream. A pumped-storage plant has two reservoirs:
- Upper reservoir – Like a conventional hydropower plant, a dam creates a reservoir. The water in this reservoir flows through the hydropower plant to create electricity.
- Lower reservoir – Water exiting the hydropower plant flows into a lower reservoir rather than re-entering the river and flowing downstream.
Using a reversible turbine, the plant can pump water back to the upper reservoir. This is done in off-peak hours. Essentially, the second reservoir refills the upper reservoir. By pumping water back to the upper reservoir, the plant has more water to generate electricity during periods of peak consumption.
The problem with the large scale projects is that there aren’t many viable sites left that don’t already have power generation facilities. With no room for expansion, we are forced to look at less than optimum sites and install smaller facilities. Continued advances in technology may reduce development costs over time, however.
The environmental and aquatic impact of these smaller projects is usually minor when compared to large scale dams. These projects usually have very limited or no storage capacity, cause little or no upstream flooding, and generate power by diverting some of the water from a stream or river to the turbine and generator and releasing it back into the stream or river.
Hydroelectric power generation may also find its future in the largest body of water – the ocean. Wave and current generation technology is making rapid strides and may soon be the standard. This technology, when used properly, can have a very limited impact on the environment, and projects are not as limited to specific locations like land based projects through the use of tidal currents, ocean currents and wave power.
Yesterday, I talked about the very basics of how solar energy works and how it’s made.
CSP vs PV – Energy Storage and efficiency
CSP (Consentrated Solar Thermal) systems are capable of storing energy by use of Thermal Energy Storage technologies (TES) and using it at times of low or no sunlight, e.g. on cloudy days or overnight, to generate electric power. This capability increases the penetration of solar thermal technology in the power generation industry as it helps overcome intermittency problems; usually due to environmental fluctuations.
PV (Photovoltaic) systems, on the other hand, do not produce or store thermal energy as they directly generate electricity – and electricity cannot be easily stored (e.g. in batteries) especially at large power levels.
CSP systems are far more attractive for large scale power generation as thermal energy storage technologies are far more efficient than electricity storage technologies; CSP systems can produce excess energy during the day and store it for usage over the night, so energy storage capabilities can not only improve financial performance but also dispatchability of solar power and flexibility in the power network.
On a much larger scale, solar thermal power plants employ various techniques to concentrate the sun’s energy as a heat source. The heat is then used to boil water to drive a steam turbine that generates electricity in much the same fashion as coal and nuclear power plants, supplying electricity for thousands of people.
In one technique, long troughs of U-shaped mirrors focus sunlight on a pipe of oil that runs through the middle. The hot oil then boils water for electricity generation. Another technique uses moveable mirrors to focus the sun’s rays on a collector tower, where a receiver sits. Molten salt flowing through the receiver is heated to run a generator.
Other solar technologies are passive. For example, big windows placed on the sunny side of a building allow sunlight to heat-absorbent materials on the floor and walls. These surfaces then release the heat at night to keep the building warm. Similarly, absorbent plates on a roof can heat liquid in tubes that supply a house with hot water.
But solar energy doesn’t work at night without a storage device such as a battery, and cloudy weather can make the technology unreliable during the day. Solar technologies are also very expensive and require a lot of land area to collect the sun’s energy at rates useful to lots of people.
Despite the drawbacks, solar energy use has surged at about 20 percent a year over the past 15 years, thanks to rapidly falling prices and gains in efficiency. Japan, Germany, and the United States are major markets for solar cells. With tax incentives, solar electricity can often pay for itself in five to ten years.
The hope for a “solar revolution” has been floating around for decades — the idea that one day we’ll all use free electricity from the sun. This is a seductive promise, because on a bright, sunny day, the sun’s rays give off approximately 1,000 watts of energy per square meter of the planet’s surface, but we all like saving things for a rainy day and we simply can’t do that quite yet with solar energy.
How much sunlight energy does our PV cell absorb? Not as much as one might think. In 2006, for example, most solar panels only reached efficiency levels of about 12 to 18 percent. The most cutting-edge solar panel system that year finally muscled its way over the industry’s long-standing 40 percent barrier in solar efficiency — achieving 40.7 percent. So why is it such a challenge to make the most of a sunny day?
Visible light is only part of the electromagnetic spectrum. Electromagnetic radiation is not monochromatic — it’s made up of a range of different wavelengths, and therefore energy levels.
Light can be separated into different wavelengths, which we can see in the form of a rainbow. Since the light that hits our cell has photons of a wide range of energies, it turns out that some of them won’t have enough energy to alter an electron-hole pair. They’ll simply pass through the cell as if it were transparent. Still other photons have too much energy. Only a certain amount of energy, measured in electron volts and defined by our cell material is required to knock an electron loose. We call this the band gap energy of a material. If a photon has more energy than the required amount, then the extra energy is lost. (That is, unless a photon has twice the required energy, and can create more than one electron-hole pair, but this effect is not significant.) These two effects alone can account for the loss of about 70 percent of the radiation energy incident on our cell.
We have other losses as well. Our electrons have to flow from one side of the cell to the other through an external circuit. We can cover the bottom with a metal, allowing for good conduction, but if we completely cover the top, then photons can’t get through the opaque conductor and we lose all of our current (in some cells, transparent conductors are used on the top surface, but not in all). If we put our contacts only at the sides of our cell, then the electrons have to travel an extremely long distance to reach the contacts. Its internal resistance is fairly high, and high resistance means high losses. To minimize these losses, cells are typically covered by a metallic contact grid that shortens the distance that electrons have to travel while covering only a small part of the cell surface. Even so, some photons are blocked by the grid, which can’t be too small or else its own resistance will be too high.
The only question that occurred to me was if some that mass amounts of asphalt, metal, concrete, things like that are contributing to global warming, or at least warming around the area. My question was, wouldn’t solar panels do the same?
When I went out to try and answer the question, I had to keep in mind that local warming is not the same as global warming. While that may be true, I’m still wondering if any of the local heat would happen to spill into other areas. While I have no idea, I did find out that solar panels do not supposedly contribute to global warming or local warming. http://www.treehugger.com/clean-technology/ask-pablo-do-solar-panels-actually-contribute-to-climate-change.html This article lays it out quite nicely. And it even says that if roofs were replaced or were covered with these solar panels then that would reduce global warming some. I like that idea. Roof are supposed to be heat absorbent, so even if solar panels did contribute to that problem, it would only be replacing the roof and no more would be added. But the article says that it doesn’t
Then there is this article. http://voices.yahoo.com/solar-power-collectors-may-cause-more-global-warming-3176283.html?cat=9 . I’m not quite sure I follow or understand this guy’s logic. While some of it makes sense, most of it doesn’t and it doesn’t seem to be causing any problems that fossil fuel energy doesn’t cause. And at least with solar power, our air wouldn’t be toxic.
And now there is this article http://www.lowtechmagazine.com/2008/03/the-ugly-side-o.html . This isn’t the only article I found on this aspect, but the comments point out the things that are incorrect or miscalculated in the article. The article talks about how the production of solar panels contribute to global warming. The problem is that it takes extreme amounts of heat, fossil fuels, etc. to make these panels. The question is does the amount of emissions being let into the atmosphere outnumber the amount of electricity emissions you will save? If there is one thing that everyone is disagreeing about it’s the math. They all have different numbers. Who is right? I don’t know. I’ll never know. But they all seem to agree that solar energy is better than gas. They’re just trying to decide if the benefits are large enough to be worth it.
I’m giving you several production CO2 emission articles, so you check them all out. I don’t know whose math is right, but it’s there for you to decide for yourself. http://www.mnn.com/green-tech/research-innovations/blogs/how-much-co2-does-one-solar-panel-create
One thing I’d like to point out is that the numbers might be different because they come from different places. Not all factories are made the same so they don’t use the same amount of energy. Also, where people live is different. The sunnier a place is or the longer the sun is out, the more energy you’ll have and the pay off will be bigger.
The last and definitely least argument is that they’re ugly, but I’m not even going to get into this.
So that’s that. I’m sure that’s not all the finer details, but it’s the gist. Solar power isn’t perfect, but its evolving and it’s better than coal, fossil fuels, nuclear energy could ever hope to be.