Hydro-power is generated by using water to make electricity. Water constantly moves through a vast global cycle, evaporating from lakes and oceans, forming clouds, precipitating as rain or snow, and then flowing back down to the ocean. The energy of this water cycle, which is driven by the sun, can be tapped to produce electricity or for mechanical tasks like grinding grain. Hydropower uses a fuel—water—that is not reduced or used up in the process. Because the water cycle is an endless, constantly recharging system, hydropower is considered a renewable energy.
Hydropower Contribution to Electricity
The total installed capacity of hydro-electric power is about 850 GW, and hydro sources produce about 3000 TWh of electricity annually (2008 data). Hydroelectric power supplies over 15% of total world’s electricity, and about 5% of its total commercial energy.
- It is clear that hydro is already a significant renewable energy source for global electricity production.
- In recent years, focus and discussions on renewable energy sources have been more towards wind, solar and geothermal. However, with the prime position that hydro holds among renewables for electricity generation worldwide, this sector possibly requires a lot more attention than it has been getting. This also implies that there could be more opportunities here than entrepreneurs might currently know.
The International Energy Agency (IEA) projects that hydro capacity growth to increase by 63% for the period 2002-2030. While the agency predicts that new hydro plants will continue to be built, it predicts that they will not be built at a rate high enough to maintain hydro’s current share of electricity generation; as a result, hydro’s share in electricity generation is projected to fall to 13% by 2030, from about 16% in 2009.
It is estimated that two-thirds of the world’s economically feasible potential is still to be exploited and is mainly concentrated in developing countries in Africa, Asia and South America. China has used only about one-quarter of its huge hydro potential of 450 GW. It is the main contributor to hydro development today and government figures suggest that it will add more than 12 GW of new capacity each year until 2020 to reach 300 GW.
Hydro Energy - How it works
Large-scale hydro-electricity generation works as follows. A dam is built on a large river that has a large drop in elevation. The dam stores large quantities of water behind it in the reservoir. Near the bottom of the dam wall there is the water intake. Gravity causes water to fall through a gate which controls water flow. At the end of the gate there is a turbine propeller, which is turned by the moving water. The shaft from the turbine goes up into the generator, which produces the power. Power lines are connected to the generator that carries electricity to consumers
Types of Hydropower Plants
Some hydropower plants use dams and some do not.
Many dams were built for other purposes and hydropower was added later. In the United States, there are about 80,000 dams of which only 2,400 produce power. The other dams are for recreation, stock/farm ponds, flood control, water supply, and irrigation.
Hydropower plants range in size from small systems for a home or village to large projects producing electricity for utilities.
There are three types of hydropower facilities: impoundment, diversion, and pumped storage.
The most common type of hydroelectric power plant is an impoundment facility. An impoundment facility, typically a large hydropower system, uses a dam to store river water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. The water may be released either to meet changing electricity needs or to maintain a constant reservoir level.
A diversion, sometimes called run-of-river, facility channels a portion of a river through a canal or penstock. It may not require the use of a dam The Tazimina project in Alaska is an example of a diversion hydropower plant. No dam was required.
When the demand for electricity is low, a pumped storage facility stores energy by pumping water from a lower reservoir to an upper reservoir. During periods of high electrical demand, the water is released back to the lower reservoir to generate electricity.
Sizes of Hydro Power Plants
Facilities range in size from large power plants that supply many consumers with electricity to small and micro plants that individuals operate for their own energy needs or to sell power to utilities.
Large hydropower facilities have large electricity generating capacities – usually more than 30 megawatts.
Small hydropower facilities have a small-medium electricity generating capacity - usually in the range of 100 kilowatts to 30 megawatts. The total installed capacity of small hydro power projects worldwide is about 50 GW, against potential estimates of over 200 GW (2008 data).
Small hydropower projects are normally run-of-the-river schemes with no storage of water.
The definition of small hydro varies slightly from country to country; however, a value of up to 10 MW total capacity is becoming generally accepted. Power projects above 25 MW are dubbed as large hydro projects. Many think that small hydropower is one of the most environmentally benign forms of energy generation available to us today.
For a small-hydro project to be economically viable, it is essential to know whether there will be sufficient discharge available or not. As a normal practice flow duration curves are used to determine the dependable flows. The flow duration curve is a plot that shows the percentage of time that flow in a stream is likely to equal or exceed some specified value - such as the volume of flow.
Small Hydro - Quick Facts
- Small hydropower systems capture the energy in flowing water and convert it to usable energy
- Small hydropower systems have capacities of up to 25 MW
- Setting up a 1 MW plant costs approximately $1.25-1.5 million
- The cost is broadly divided under four heads—land, machinery, construction and labor
A micro hydropower plant has a capacity of upto 100 kilowatts. Micro-hydroelectric power systems are suited for small-scale applications. For instance, a micro-hydroelectric power system can produce enough electricity for a home, farm, ranch, or village.
How are locations assessed for large hydro projects?
Some points that should be given importance while selecting a site for Hydro-electric power station are given below.
- Availability of Water
- Storage of Water
- Cost and Type of Land
- Transportation Facilities
Availability of Water
Since the primary requirement for a hydro electric power station is the availability of huge amount of water, such plants should be built at a place where adequate water is available at a good head, for example, near a river or canal.
Storage of Water
There are wide variations in water supplies from a river or canal during the year. This makes its necessary to store water by constructing a dam, in order to ensure the generation of power throughout the year. Such storage helps in equalising the flow of water so that any excess quantity of water at a certain period of the year can be made available during times of very low flow in the river. Thus, the site selected for hydro electric plant should provide adequate facilities for erecting a dam and storage of water.
Cost and Type of Land
The land for the construction of plant should be available at a reasonable price. Further, the bearing capacity of the soil should be adequate to withstand the installation of heavy equipment.
The site selected for the hydro-electric plant should be accessible by rail and road so that necessary equipment and machinery could be easily transported.
Types of Hydro Turbines
There are two main types of hydro turbines: impulse and reaction. The type of hydropower turbine selected for a project is based on the height of standing water— the flow, or volume of water, at the site. Other deciding factors include how deep the turbine must be set, efficiency, and cost.
The impulse turbine generally uses the velocity of the water to move the runner and discharges to atmospheric pressure. The water stream hits each bucket on the runner. There is no suction on the down side of the turbine, and the water flows out the bottom of the turbine housing after hitting the runner.
A reaction turbine develops power from the combined action of pressure and moving water. The runner is placed directly in the water stream flowing over the blades rather than striking each individually. Reaction turbines include the Propeller, Bulb, Straflo, Tube, Kaplan, Francis or Kenetic.
Hydrokinetic energy is a new application of the concept of using water to create electricity — in this case by harnessing the natural flow or current of water. Traditional hydropower, in contrast, relies upon dams, diversionary methods, or other manmade impounding structure behind which potential energy in the water is stored.
Hydrokinetic power is quite new. As of early 2009, the only source of commercial hydrokinetic power in the U.S. is the new 200-kW nameplate-rated hydrokinetic project (expected to deliver a peak 70 kW) located in Hastings, Minnesota.
In some cases companies are experimenting with locating the hydrokinetic turbine behind an existing conventional facility’s turbine on a one-to-one ratio to generate additional power from the energy remaining in the water current exiting the dam and flowing downstream.
In terms of hydrokinetic power’s potential, a 2007 study by the Electric Power Research Institute found that the U.S. could develop at a minimum 13,000 MW of river (in-stream) and ocean-based (wave, current, and tidal) hydrokinetic power by 2025. The industry has great growth potential and is just starting to emerge from its infancy.
Applications of Hydro Energy
The hydro power can be used in different ways. It can be used for a standalone solution with a battery bank. Similarly, it can be grid connected to both supply our premise and sell the excess back to the ESB. It can also be used for heating purposes. The applications are the same as for Wind and Solar PV.
Data and Statistics
Hydro Energy Status and Trends
Hydro Power Industry - Status and Trends
Regional Scenario - Hydro-energy Capacities Countrywise
Annual Hydroelectric Power Generation
% of All Electricity Produced
Most data pertains to 2006 and beyond, collected from multiple sources
Highlights of the Above Table
- It is interesting to see that for Norway, almost all the electricity is from hydro. Brazil follows close with 90% from hydro.
- Countries such as Venezuela and Canada also generate large percentages of their electricity from hydro. For these two countries, one of the reasons is possibly their relatively low coal reserves. Venezuela has about 500 Million T of recoverable coal deposites while Canada has about 10 billion T. Contrast this with the coal reserves of USA (over 200 billion T), Russia (about 200 billion T), China (over 100 billionT) and India (over 100 billion T). It is pertinent to note here that Brazil has relatively low recoverable coal deposits as well (about 10 billion T).
Hydro Energy Projects & Companies
Prominent Ongoing Projects for Hydro Energy
Three Gorges Dam
Jinping Hydropower Station
Jinping Hydropower Station
Novermber 11 2007
Tocoma Dam Bolívar State
Lower Subansiri Dam
- Total capacity (maximum) of ongoing projects is 107820 MW (108 GW)
- Close to 95000 MW of capacity in ongoing projects are in China, almost 90% of the total
- A review of China’s hydro-projects show that some of their projects are of very large-scale (Three Gorges Dam (22.5 GW), Xiluodu Dam (12.6 GW))
Upcoming Large Hydro Projects
Democratic Republic of the Congo
Siang Upper HE Project
Santo Antônio Dam
Subansiri Upper HE Project
Banduo 1 Dam
- The total capacity of planned hydro-projects is 112400 MW
- The hydro project in Congo is of a mega-size, almost double the largest onoing project size in China.
- China is a leader in the number of planned projects too – it has 8 out of 17 planned hydro-electric projects
Hydro Energy - Research Efforts
There is a great divide when it comes to opinions on the importance of hydrogen to our future energy economy.
On the one side of the divide, hydrogen gas is seen as a future energy carrier with phenomenal potential by virtue of the fact that it is renewable, does not emit the "greenhouse gas" CO2 in combustion, liberates large amounts of energy per unit weight in combustion, and is easily converted to electricity by fuel cells.
On the other side of the divide are those who point out that there are fundamental problems with hydrogen that will ensure that it will forever remain just a great green hope and nothing more than that.
These divided opinions however have not stopped considerable research being conducted to producing and storing hydrogen.
Attempts to produce hydrogen from renewable sources have been going on for over three decades, though it has picked up momentum of late. The oil crisis in 1973, for instance, prompted research into biological hydrogen production, including photosynthetic production, as part of the search for alternative energy technologies.
For instance, several companies are attempting biological hydrogen production. Biological hydrogen production has several advantages over hydrogen production by traditional processes. Biological hydrogen production by photosynthetic microorganisms for example, requires the use of a simple solar reactor such as a transparent closed box, with low energy requirements. If such processes could be made to work on a large-scale, we have a renewable source of hydrogen.
The following are some of the research projects on hydro energy:
‘Fish-friendly’ Hydro Energy Turbines
In 1996, DOE, EPRI (Electric Power Research Institute) began a multi-year effort to develop ‘fish-friendly’ turbines for hydroelectric projects that are greater than 90% efficient and reduce fish mortality to 5% or less. By 2001, the research produced two turbine designs. The first, designed for large rivers, is currently being tested in the Columbia River. The second, designed for smaller rivers, is called the Alden/Concepts NREC turbine and features a helical-shaped runner with only three blades. The Alden turbine has no gaps and by virtue of its larger size, turns slower, which means less impact on fish. Up to 98 per cent of fish survive passing through the Alden turbine.
It is extremely expensive to protect fish. As a testament to the resources and money devoted to fish safety by the energy industry:
- Removable weirs costing $50 million to $70 million each are in use to channel fish away from turbines
- The $52 million Puget Sound Energy floating surface collector or "Gulper" captures juvenile salmon out of dam's way and transports them in a half-hour tanker-truck ride downstream for release into the Skagit River
- Better turbine designs like the Alden turbine mean much better fish survival and eliminate the need for weirs and busing fish to less dangerous neighborhoods.
550-Kw Hinubasan Minihydro Project in Loreto, Dinagat Island
This project is a typical case of remote island electrification. It is located in Loreto municipality, in Dinagat Island. Hinubasan project is envisioned to provide 24-hour power supply to 1,686 households of the municipality. The Development Bank of the Philippines has earmarked P48.5 million funding for the project.
The project involves the installation of two 275-kW Turgo impulse turbines at 162 m. net head and flow of 0.228 cu.m per sec per unit. The turbines, generators, governors, control panels and transformers will be sourced from China. It is expected that the costs of generating power from the facility is P2.96 per kWh. This rate compares favorably against the basic power charge in the area of P3.97 per kWh. The proponents expect to recoup their investments within few years.
Bubunawan Hydro Project
This 7-MW mini-hydro project, located in Baungon, Bukidnon, has the potential to generate 37.6 MWh of electricity annually. The project proponent is the Bubunawan Power Company. The system was commissioned in the later part of 2000.
Steady Flow Hydro Power Plant
A promising innovation in the hydro energy system has been recently developed. Although still at R&D stage, “Steady Flow Hydro System,” received a special citation for innovation in the Nationwide Contest for New and Renewable Energy Systems sponsored by the Philippine National Oil Company last year. The innovation ensures constant flow rate, rotative speed, frequency and voltage for all operating conditions of head and electrical load, while eliminating problems involving water hammer, surging and silting-up. The need for a speed governor is eliminated since a synchronous speed is assured by a metering pump at the forebay.
The pump delivers fixed water flow rate at negligible head from the forebay through the penstock and to the hydro engine. This set up allows the latter to run at synchronous speed with the generator. Since the head of the metering pump is negligible, the pipeworks connecting the forebay and tailrace exert siphoning effect. Consequently, the electric motor is used only to surmount mechanical friction; its power consumption is a small fraction of the total hydropower output.
The metering pump and its driver can be conveniently controlled and monitored for performance at the control panel of the generator. There are other notable innovations in local small hydro facilities that were developed out of necessity to adapt the system to the specificities of local conditions.
Hydro energy – Barriers
Hydrogen storage, the high reactivity of hydrogen, the cost and methods of hydrogen fuel production, consumer demand and the cost of changing the infrastructure to accommodate hydrogen vehicles are key bottlenecks to transition to a hydrogen economy.
- Currently, the only way that hydrogen production even approaches practicality is through the use of nuclear plants. Even hydrogen fuel derived from nuclear power would be expensive.
- Current production of hydrogen takes a lot of energy, and uses fossil fuels as the base. All free hydrogen generated today is derived from natural gas. So right off, we have not managed to escape our dependency on nonrenewable hydrocarbons. If we have to burn fossil fuels to make hydrogen, what have we really gained?
- Hydrogen is extremely reactive, is combustible and flammable. It must be stored at extremely low temperatures and high pressure. A container capable of withstanding these specifications is larger than a standard gas tank.
- Compressed and liquefied hydrogen present problems of their own. Both techniques require energy and so further reduce the net energy ratio of the hydrogen. Liquid hydrogen is cold enough to freeze air, leading to problems with pressure build-ups due to clogged valves
- Both compressed and liquefied hydrogen storage are prone to leaks. In fact, all forms of pure hydrogen are difficult to store.
- Another problem for hydrogen fuel is consumer demand and the cost to change all gasoline filling stations and vehicle production lines into hydrogen. Oil companies will not build filling stations until the hydrogen cars are on the market, and hydrogen cars might not become mainstream unless oil companies build the infrastructure!
Micro-hydro Powered Home (Australia)
A home powered by micro-hydro energy is situated on the Jack River, high in the Eastern Strzelecki Ranges, up from Yarram in Gippsland, Victoria (Australia). The river provides the home with power all year round via two micro-hydro turbines. The house was designed using passive solar principles, thus reducing heating and cooling requirements.
Water is taken from the Jack River via a 2 metre by 1 metre capture pond, and flows downhill through a 250mm diameter pipe to the turbines. A trash rack, or wire mesh screen in the capture pond prevents leaves, sticks and other debrid from entering the turbine feed pipe and blocking up the system.
The micro-hydro generators are 4-nozzle Turgo turbine units, generating around 450 watts each of DC electricity which is fed into a 24 volt, 850 amp-hour battery bank. There are two inverters in the system. One inverter has been converted to act as a regulator for the battery bank, diverting excess power into the hot water system element. The second inverter provides power for all the appliances in the home.
These appliances include a 240 volt AC refrigerator, computer, microwave oven, electric jug, washing machine, vacuum cleaner, TV and VCR. There are also four large woodworking machines in the workshop that all run from the micro-hydro power system.
Houston Firm Turning on Turbines to Generate Hydrokinetic Power (USA)
Houston-based Hydro Green Energy LLC received approval from the Federal Energy Regulatory Commission in December and completed the installation of the “Hydro+” turbine on Jan. 5, 2009.
All hydropower facilities in the country currently use enclosures or water-diversion methods and structures to generate power. Hydrokinetic turbines operate in open waters, though the installation in Hastings is actually just below a dam and power plant.
“There’s a dam clearing out any debris coming down the river,” he notes. “We can tap into an existing power-purchase agreement, and it’s a significantly shorter and less expensive licensing process than if we used an open river.”
Once a second turbine comes online in April, the two should provide more than 5 percent of the city’s electricity.
“Hydro is the most predictable of all the renewables - way more than solar or wind,” says Wayne Krouse, Hydro Green chairman and CEO. “You can have a higher value that’s produced because you can forecast it for the people who operate the grids.”According to Krouse, the capacity factor of solar ranges from 25 percent to 40 percent, depending on cloud cover and the latitude of the installation. Wind is a more modest 20 percent to 25 percent. Water is another story.
“Rivers are always flowing in the same direction,” says Krouse. “Theoretically, there’s a 100 percent capacity factor,” he says. (Jan 2009)