The problem is the huge costs of building dams and the long time it takes to build them. Itaip? Dam, for example, cost $20 billion and took 18 years to build. Actual costs for hydropower dams are also almost always far higher than estimated costs - on average around 30 per cent higher.
The best fossil fuel plants are only about 50% efficient. In the U.S., hydropower is produced for an average of 0.85 cents per kilowatt-hour (kwh). This is about 50% the cost of nuclear, 40% the cost of fossil fuel, and 25% the cost of using natural gas.
Hydro system costs can vary widely depending on the energy needed, the head, the flow, and the distances between intake, turbine, and wherever the energy is being used. It's easy to look at the cost of the turbine—home- to ranch-scale models range from perhaps $1,500 to $10,000.
A consortium called Six Companies Inc., which included Bechtel, won the right to build the concrete arch dam, at a cost of nearly $49 million—a staggering amount in the early 1930s (roughly equivalent to $860 million today).
Advantages of Hydroelectric Energy
- Renewable. Hydroelectric energy is renewable.
- Green. Generating electricity with hydro energy is not polluting itself.
- Reliable. Hydroelectricity is very reliable energy.
- Environmental Consequences.
Hydropower does not pollute the water or the air. However, hydropower facilities can have large environmental impacts by changing the environment and affecting land use, homes, and natural habitats in the dam area. Most hydroelectric power plants have a dam and a reservoir.
The government estimated that the Three Gorges Dam project would cost 180 billion yuan (US$22.5 billion).
The map above shows the amount of electricity produced by hydroelectric dams in each of the nations of the world. The United States leads the world in hydroelectric dams, mostly due to its high level of technology and plentiful supply of rivers. Canada, Brazil, and China also produce a large amount of hydroelectricity.
A 10 kW wind turbine costs approximately $48,000 – 65,000 to install. The equipment cost is about $40,000 (see 10 kW GridTek System ) and the rest is shipping and installation. Towers without guy wires are more expensive than guyed towers. That depends on your cost of electricity and average wind speed.
Hydroelectric power is also very efficient and inexpensive. "Modern hydro turbines can convert as much as 90% of the available energy into electricity. The best fossil fuel plants are only about 50% efficient. In the US , hydropower is produced for an average of 0.7 cents per kilowatt-hour (kWh).
Students learn that dams do not last forever. Similar to other human-made structures, such as roads and bridges, dams require regular maintenance and have a finite lifespan. Many dams built during the 1930-70s, an era of intensive dam construction, have an expected life of 50-100 years.
In fact, the estimated costs of building new coal plants have reached $3,500 per kW, without financing costs, and are still expected to increase further. This would mean a cost of well over $2 billion for a new 600 MW coal plant when financing costs are included.
A dam is built to control water through placement of a blockage of earth, rock and/or concrete across a stream or river. Dams are usually constructed to store water in a reservoir, which is then used for a variety of applications such as irrigation and municipal water supplies.
Between 2002 and 2008, for example, cost estimates for new nuclear plant construction rose from between $2 billion and $4 billion per unit to $9 billion per unit, according to a 2009 UCS report, while experience with new construction in Europe has seen costs continue to soar.
This is called hydroelectric power or hydropower. The most common type of hydroelectric power plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity.
Benefits of Dams
- Recreation. Dams provide prime recreational facilities throughout the United States.
- Flood Control. In addition to helping farmers, dams help prevent the loss of life and property caused by flooding.
- Water Storage (Fire & Farm Ponds)
- Mine Tailings.
- Electrical Generation.
- Debris Control.
The alteration of a river's flow and sediment transport downstream of a dam often causes the greatest sustained environmental impacts. Life in and around a river evolves and is conditioned on the timing and quantities of river flow. A dam also holds back sediments that would naturally replenish downstream ecosystems.
On average, in 2011, nuclear power had the lowest electricity production costs at 2.10 cents per kilowatt hour, and petroleum had the highest at 21.56 cents per kilowatt hour.
The following is a partial list of dams and reservoirs in the United States. There are an estimated 84,000 dams in the United States, impounding 600,000 mi (970,000 km) of river or about 17% of rivers in the nation.
Embankment dams are made from compacted earth, and have two main types, rock-fill and earth-fill dams. Embankment dams rely on their weight to hold back the force of water, like gravity dams made from concrete.
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