Category: energy

What Geothermal Electricity is:

Geothermal electricity is produced by tapping into the natural heat produced below the crust of the earth and converting it into electricity.

How Geothermal Electricity is made:

Like in a coal burning power plant, a nuclear plant, or a hydroelectric plant, geothermal electricity uses moving water to turn a magnet. In this case, wells are dug deep into the earths crust. Cold water goes down one well where it is heated by the earth’s core. Hot water comes up a second well. The movement of water sinking when cold and rising when hot moves the turbine. This movement of water occurs naturally (without the magnet) in a geyser or hot springs.

How much of our current electricity is Geothermal Electricity:

Geothermal electricity generation currently makes up less than 1% of the electricity produced in the United States. However, the US produces the most geothermal electricity by MW (over 3000 MW in 2010). The fraction of our total is so small because of electricity use, population, and expansiveness of the country. On the other hand, small well-located nations such as Iceland and the Philippines produce around a quarter of their total electricity through geothermal electricity.

Potential energy supply:

Regions surrounding tectonic plate boundaries (like Iceland and the Philippines) can access Earth’s heat easily. In the US, these areas are mostly in the western states. The US Geological Survey estimates that by tapping into sites in these states up to 73000 MW could be produced per year. That’s about 7% of current electricity production.

Materials and how we get them:

A geothermal plant has wells in place of a coal plant’s furnace, but is otherwise the same. Besides drilling equipment (which is hopefully reusable), geothermal electricity doesn’t require any special materials. It also requires no fuel once it’s up and running.

Waste produced and how we deal with it:

Drilling deep into the earth can release toxic gases. Carbon dioxide, hydrogen sulfide, methane, and ammonia are greenhouse gases and contribute to rain acidifictation. Trace toxic elements such as mercury and arsenic can also be brought to the earth’s surface. These gases and elements need to be filtered out and either contained, or put back into the earth for safety.

Cost:

The majority of the capital cost comes from drilling the wells for the power plant. This depends on the depth of the well and the hardness of the rock to be drilled through. This makes geothermal energy cheaper in places like the western U.S., Iceland, and the Philippines. In the western U.S., it costs between $2-4 million per megawatt to drill and build the associated power plant.

Challenges:

The heat of the earth is steady and consistent, but can be far away from the surface. Hot spots can be reached relatively easily at the edges of tectonic plates. Elsewhere, the difficulty of drilling deeper to reach the heat is prohibitive. More complicated power (and expensive) plants can harvest the lower grade heat and turn it into electricity. As with all responsible drilling activity, the location is important. Locations for geothermal plants need to be scouted and surveyed carefully. This reduces the risk of drilling into toxic substances. Careful scouting also determines that the well can be drilled to the desired depth without damaging the equipment. Drilling into the heat also has its challenges. The temperature affects the materials – causing steel to become brittle and plastics to melt. Additionally, locations that are good for geothermal electricity are also earthquake prone. Earthquakes can destroy wells and put a geothermal plant out of commission.

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For an introduction on sources of electricity, look here.
For an explanation of how we make electricity, look here.
Clean Coal
Nuclear Energy
Hydroelectricity
Wind Power 

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What Wind Power is:

Wind power is the energy or electricity produced by using the wind to turn a turbine.

How Wind Power is made:

Wind power is wonderfully simple! In fact if you’ve ever blown a pinwheel you’ve essentially made wind power, you just haven’t turned it into electricity. For producing electricity, a turbine is positioned so that it’s blades catch the wind. The wind spins the turbine, and the turbine spins the magnet in the generator. In the case of wind power, bigger is better, which is why the turbine blades of industrial trubines are usually over 50 meters long. It’s also all about location, location, location because electricity is only produced when the wind is able to spin those giant blades. Wind turbines are best positioned on high ground or off-shore, and are often made so that the head where the blades are connected can spin to be positioned in the direction of the wind.

How much of our current electricity is produced by Wind Power:

Wind power generation currently is responsible for about 4.1% of the total electricity generated in the U.S. (up from 3.46% in 2012!). The good news is that the U.S. is one of the largest and fastest growing wind markets. In 2012, 43% of all new electricity generation were wind turbines.

Potential energy supply:

The Department of Energy envisions that 20% of all electricity used in the U.S. could be produced from wind power by the year 2030. This estimate includes 4% generated off-shore. If we took full advantage of off-shore wind, more than 17 TW of electricity could be generated by wind power, which is 4 times as much electricity as the U.S. uses in a year.

Materials and how we get them:

The wind tower is made of steel built on a cement foundation. The casing for the tower and the gear box (or nacelle) is made of fiberglass which is a type of reinforced plastic made in a factory out of silica sand, limestone, and soda ash. The rotor blades are also made of fiberglass.

Waste produced and how we deal with it:

While producing electricity, wind turbines don’t make any sort of waste. The only waste associated with wind turbines is what comes from the manufacturing and construction of the turbines.

Cost:

The average price of wind power in 2012 was about $0.04 per kWh. An industrial sized turbine costs $1-2 million per MW of capacity. Wind power has significant economy of scale. Small turbines are much more expensive per watt than large turbines.

Challenges:

Wind power requires wind, of course. And wind can be unpredictable. With our current grid and battery technology, it is difficult to store wind power for use when the wind dies down. Off-shore wind harvesting would provide a more steady source, but requires greater infrastructure and is often poo-pooed by NIMBY’s (Not In My Back Yard folk) who don’t want turbines showing up in their water view.

The best location for wind turbines is usually in rural areas, which means the power must be transported to urban areas where it will be used, requiring transmission lines to be built.

There has been some problems with birds getting caught by the blades of wind turbines and noise pollution, but this can usually be solved by better siting and technological advances.

It’s also worth mentioning that there have been complaints of health issues associated with the vibrations caused by the spinning rotors. If you’d like more information on why some people oppose wind power – at least on the industrial production level, you can check out Wind Watch.

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For an introduction on sources of electricity, look here.
For an explanation of how we make electricity, look here. 
Clean Coal,
Nuclear Energy,
Hydroelectricity

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What hydroelectricity is:

Hydroelectricity is electricity that is produced by moving water.

How hydroelectricity is made:

If you’ve been following along on this series, you’re probably familiar with the goal: turning a magnet inside a coil of wire. To produce hydroelectricity, the moving water spins the turbine (and thus the magnet) directly. No need to heat and pump water around because it’s already moving.

The moving water can come in a variety of forms. The most conventional form is a dam. The weight of the water in the reservoir is the source of energy. At the bottom of the reservoir there is a drainpipe. The gravity pulls the water from the reservoir through the drainpipe, and spins the turbines as it flows past.

Another possible source of hydroelectricity is a river. The turbine is submerged in the river, spinning as the water flows past (think a modern day water mill). These “run-of-the-river” generators are small scale and the electricity must be used as it is produced. But no damming is needed, so the environmental impacts are much lower.

How much of our current electricity is hydroelectricity:

Hydroelectricity is currently the largest source of renewable energy. World wide, hydroelectricity accounts for 16% of electricity production. However, in the U.S. only 7% of our electricity is hydroelectricity.

Potential energy supply: 

According to the US Department of Energy, building generators on currently non-powered dams in the U.S. could meet 16% of the US electricity demands. This would more than double our current supply.

Materials and how we get them:

Moving water! As explained above, this can either be naturally occurring – such a a river or waterfall for small scale production, or through man-made dams. In the case of the dam, massive amounts of concrete are needed, but the power plants actually require less materials than coal power. Remember, hydroelectricity doesn’t need pumps, furnaces, or fuel.

Waste produced and how we deal with it:

Once the dam and plant are built, hydroelectricity produces essentially no waste. However, constructing dams uses tons of cement, a huge source of CO2 emissions.

Cost:

The cost of electricity from a large scale hydroelectric plant is about $0.03-0.05/Kwh

Challenges:

Hydroelectricity sounds pretty great so far! Simple to produce, and pretty low impact.  Sure there is the issue of making all of that cement, but dams last for 50-100 years easily without requiring much maintenance. The CO2 emissions from building a dam are actually the least of any of the renewable energy sources.

However, damming rivers can cause great distress to the environment and to the ecosystems and communities that rely on the river. The reservoir that is produced by damming floods and submerges the land around it, destroying habitats. Dams disrupt the natural aquatic ecosystems in the river, too (e.g. blocking salmon and other migratory animals). The change in current also has dramatic effects downstream, for example not being strong enough for irrigation or to flush out salt water in deltas.

The far less impacting run-of-the-river production is not scaleable. It’s great for local needs where it’s available, but can’t meet greater demands.

 

 

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For an introduction on sources of electricity, look here.

For an explanation of how we make electricity, look here.

Clean Coal

Nuclear Energy

 

Oh, hey, Building Earth has a facebook page now.  Keep up to date on posts and other interesting green news by liking us!

What Nuclear Energy is:

Nuclear energy is the energy that is produced when one atom splits into two. This process is known as fission, and occurs naturally in radioactive elements.

How electricity is made from Nuclear Energy:

While fission happens naturally, the process is slow and unpredictable. In order to use nuclear energy to make electricity, we want more control over the process. We induce fission by shooting neutrons at Uranium-235 (U-235). When the nucleus of U-235 absorbs the neutron it becomes unstable and splits, releasing huge amounts heat.

A nuclear reactor contains rods of U-235, control rods, and a fluid. Neutrons are shot at the rods. If they hit a U-235 rod, induced fission occurs.  If they it a control rod, they don’t release energy.  Changing the number of control rods in the reactor controls the temperature of the reactor. If the reactor is too hot, more control rods are put in to reduce fission. The fluid collects the heat from fission and transfers it to water. The water flows through a pipe and turns a turbine to produce electricity.

There’s a lot more great information about how nuclear power plants work here.

How much of our current electricity is produced by Nuclear Energy:

There are about 100 nuclear energy plants in the U.S., which produce about 20% of our electricity.

Potential energy supply:

The US has about 4% of the worlds known uranium, which is over 220,000 short tons. The U.S. has uranium mines in Utah, Texas, Nebraska, and Wyoming. 1 pound of enriched U-235 will produce as much energy as about 1 million gallons of gasoline.

At the current rate of nuclear energy production, there is enough uranium in the world to last 230 years (if the estimates of accessible uranium are correct). However, new technologies are being developed to produce energy more efficiently. They could extend the energy supply for 30,000 years!

The big challenge with nuclear energy supply is building nuclear power plants. It takes 5-7 years to build each plant.

Materials and how we get them:

The uranium used in a nuclear reactor needs to be mined and then enriched so that at least 3% of it is U-235. To enrich uranium, it is reacted with fluorine gas and then put into a centrifuge to pull out the heavier U-235.

Another material concern is concrete. Building a safe nuclear power plant uses 400,000 cubic yards of concrete. Concrete production releases huge amounts of CO2. This means that nuclear power plants are not a carbon neutral source of energy.

Waste produced and how we deal with it:

The waste from nuclear energy is obviously of great concern. Radioactive material will eventually decay into safe material. The concern is the length of time it takes to become safe, and how we contain it until it then.

Radioactive waste is separated into two categories, high-level radioactive waste and low-level radioactive waste. Low-level waste includes radiated things that were in contact with the U-235.  These materials need to be stored -for hundreds of years. The used fuel is high-level waste and needs to be stored for tens of thousands of years.

A typical nuclear power plant produces 22 short tons of radioactive waste per year. This waste cools for years, and then is mixed with glass and put into a large concrete containment tower in order to continue cooling.

Cost:

Nuclear plants are quite expensive compared to coal, typically costing $5-6 billion dollars. The production of nuclear energy costs slightly less than $0.03 per kWh, making it cheaper than coal.

Challenges:

Mining, enriching, and transporting the uranium needed for nuclear energy is messy. Plus, it is important to prevent radiation contact during these steps.

Containment is the biggest challenge with nuclear energy.  The reactor is surrounded by a concrete liner which serves as a radiation shield. The concrete is then contained in a steel vessel to prevent radioactive leaks. Finally, there is an outer concrete building which is designed to be strong enough to withstand earthquakes or impacts (like that of an crashing jet).  (The nuclear power plant in Chernobyl lacked this outer concrete building.)

Cooling is also a big challenge with nuclear energy. U-235 produces so much heat when it splits, that even spontaneous decomposition can cause a melt-down (literally, the container it is in melts). So there needs to be constant cooling of the reactor and waste containers. This was the issue with the Fukushima plant. The nuclear reactor shut down when the earthquake struck, but the tsunami knocked out the generators that were cooling the reactor.

All of these factors are to prevent contact with radiation. Radiation poisoning causes illness and death for living things. Nuclear power plants generally do an excellent job of managing the risks and containing the waste. With high-level waste taking tens of thousands of years to decay, there is no way for us to know if our current containment measures are enough to keep living things safe. To ensure safety, we must build structurally sound plants with plenty of back-ups for cooling systems and constantly maintain, monitor and guard the containment of materials.

For an introduction on sources of electricity, look here.

For an explanation of how we make electricity, look here. 

Clean Coal

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What clean coal is:

Historically, “clean coal” referred to any method of reducing the environmental impact of coal-based electricity. Today, clean coal refers specifically to containing the carbon dioxide (CO2) emissions in tanks underground, also known as carbon sequestration. Separating out the carbon dioxide from other waste is not simple! Carbon dioxide sequestration is not simple! The carbon dioxide needs to be separated out from other waste before it can be sequestered. Carbon can be separated out before or after burning.* Pre-combustion separation is basically cleaning the coal. Before burning, the coal is cooled to separate out nitrogen and sulfur. Cooling the coal is very energy intensive. (Ha! we need to burn more coal in order for us to clean the coal we’re burning!) When this clean coal burns, it only gives off CO2 and water.  Post-combustion separation is basically cleaning the emissions. The smoke is dissovled in a solvent and then different parts are separated out of the solution one at a time. Currently the chemicals needed for the dissolving and separating are very expensive. This method is also pretty energy intensive. The separated out CO2 is then pumped to underground storage tanks. This stored CO2 would be kept underground indefinitely.

How clean coal makes electricity:

As I explained last week, coal is burned to heat water into steam which spins a turbine. Clean coal works the same way, but the coal (pre-combustion) or emissions (post-combustion) are cleaned.

How much of our current electricity is produced by clean coal:

Coal power currently accounts for half of the U.S. electricity production. Essentially none of it is “clean coal”.

Potential energy supply:

According the the EIA, the US currently has 19.2 billion short tons of easily accessible coal. The EIA estimates that these reserves will last about 200 years. It is difficult to say how much total coal there is since it is underground and some of it has yet to be discovered. Total coal estimates in the US are 4 trillion short tons.

With carbon sequestration technology, all of this coal could be burned as clean coal.

Materials and how we get them:

We mine coal, which provides jobs (yeah!)  and environmental problems (boo!). For clean coal, we need massive amounts of pipeline and pumps to move the CO2 through from power plants to in-ground tanks. Additionally, we need tanks for storage and the space for the tanks underground. And those tanks would need to be fitted with leak detection to ensure that the CO2 wasn’t getting out.

Waste produced and how we deal with it:

The stuff that we clean out of the coal or emissions (sulfur, nitrogen, and particulates) can be used in industrial processes. The used solvents and the waste from their production and the production of pipes and tanks would be a new kind of waste we would need to deal with.

Cost:

Estimates vary for how much carbon sequestration costs, but the short answer is tens of billions of dollars per year in the U.S..  A coal power plant in Mississippi is being built to showcase clean coal technology, and the cost of building the plant equipped to sequester CO2 is nearing $5 billion. For comparison, the cost of a regular coal burning power plant is around $1 billion. According to the EPA, first generation carbon capture technology used in coal-powered electricity production would increase the cost of electricity by 70-80%.

Challenges: 

The biggest challenge of clean coal aside from the cost to convert our power plants, is that there is so much unknown about long term storage of CO2. Can we make tanks that don’t leak? Will storing it below ground have negative impacts on structural integrity of the ground? What happens if there is an earthquake? However, clean coal is an opportunity for America to lead the world in green tech. Many developing countries – notably China and India – use coal power. If we worked with them towards clean coal, there would be a huge impact on carbon emissions. Whew. I know this is a complicated one. You’re a champ if you made it through. Goes to show, solving our energy needs is not going to be easy. *Alternatively, the coal can be gasified. Burning gas is much more efficient than burning straight coal, but the process of gasifying coal is complicated, expensive, and currently only being accomplished in small scale amounts.

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For an introduction on sources of electricity, look here.

For an explanation of how we make electricity, look here. 

Oh, hey, Building Earth has a facebook page now.  Keep up to date on posts and other interesting green news by liking us!

Before delving into the details of different electricity sources I’m going to give a basic overview of how the electricity that comes to your home is made. Despite the fact that I’d been studying physics, before I toured a hydroelectric plant in Tanzania I only had a theoretical understanding of how we actually make electricity at a power plant. I was fascinated on the plant tour, and count that among the defining moments in inspiring me to want to study and work with renewable energy.

So to start: what is electricity? It’s moving electrons. Typically we move the electrons in metal wires because metals tend to have plenty of free electrons just hanging around ready to move, and also plenty of spaces for the electrons to move into.

How do we convince these electrons to move? Electrons will start moving in the wires when there is a moving magnetic field nearby. In a typical coal or natural gas fueled power plant, the fuel is used to move big magnets in order to produce a moving magnetic field.

The coal or natural gas (or sometimes petroleum, but not much in the U.S.) is burned in order to heat up water in pipes. As the water heats to a boil it changes into steam. The steam rises through the pipes until it gets to a condensation tank. Here it cools down and changes back into liquid water. The liquid water is heavy, so it falls to the bottom of the tank, and as it does this it turns a turbine. The liquid water is then pumped back to the furnace where it can be heated up again.

The turbine is connected to a big magnet inside of a large coil of wire. When the turbine spins from the condensing water, it turns the magnet which produces a moving magnetic field, and the moving magnetic field causes all those free electrons in the wire coil to move throughout the wire.

For each source of electricity (except solar, we’ll get to that later), the objective is to spin that magnet inside the coil of wires.

It’s 10 am and I have already used a light,  a toaster, a stove, and the internet. I also plugged in my computer and took food out of the refrigerator. All of this without a thought as to where my electricity comes from besides “the wall”. This is my privilege living in a country with a reliable grid. I don’t think about the time of day, the season, or the weather; I just plug in and use.

Unfortunately, being so disconnected from the sources of electricity makes people careless. We don’t think about how much we use or where it is coming from except when we pay our electricity company.

So how much are we using?  According to the U.S. Energy Information Administration, in 2012 Americans used nearly 11,000 kilowatt hours of electricity. For perspective, that much electricity can light a standard 60 watt bulb continuously for 21 years!

Most of that electricity (68%) is produced by burning fossil fuels such as coal, natural gas, and petroleum. There are two big problems with using these materials. The first is that they are in limited supply so we have to expend more and more energy to get them. And the methods we use (mining and fracking) are damaging to the environment. The second big problem is that they release large amounts of carbon dioxide when burned. In fact, electricity and heat generation are the largest producers of man made carbon dioxide emissions.

Luckily, these two problems have the same solution – switch to renewable energy sources. We’re slowly moving in the right direction by investing in nuclear, hydroelectric, geothermal, wind, biomass, and solar electricity. We can’t put all our eggs in one basket; we need to diversify electricity production. We need to pursue all of these options to have the hope of making our electricity production carbon neutral.

In the coming weeks I’m going to explore how we make electricity from each of these sources (plus clean coal/carbon sequestration). I’ll also explain the science behind the sources and the pros and cons of each.  Let me know if you have any questions you want me to answer.