Types of Incidents in Hydropower Plants
Hydropower plant incidents usually cause by three main factors: poor planning, unpredictable natural events, or equipment failure. Sometimes developers of new dams do not take all geological factors into account, which was the case in the 1963 Vajont dam disaster in Italy. It was caused by a tidal wave overtopping the dam and flooding the valley below, killing around 2,500 people. The wave was caused by a the water in the dam eroding the rock, causing a landslide, and this created a massive wave, which did not destroy the dam, but swept down the valley completely destroying several towns on its way.
Another hydropower incident was in the Banqiao dam caused by a typhoon, reaching into affected areas a yearly precipitation level in a few hours, which no one would have predicted happening, and a dam failure caused by unpredictable natural causes in the Kyzyl-Agash dam in Kazakhstan in 2010.
Uses of Hydropower Energy
Like wind energy, hydropower energy is mostly used for electricity generation and accounts for almost 17 % of the total global electricity production. Another major, but mostly unknown use of hydropower, is for storing energy. Using the existing dam infrastructure, utilities use hydropower to store energy, which is known as “pumped hydro storage.” Some of the uses of hydropower energy are as follows:
• Electricity: Hydroelectricity is one of the most important sources of energy in the world. Hydroelectricity is one of the cheapest and non-polluting sources of power. Though it can cause ecological damage initially, it has better climate compatibility than other major forms of energy such as nuclear, coal, gas, and others. Many countries in the Nordic region and South America are almost completely dependent on hydropower for their energy needs. For some countries, such as China and India with massive energy needs, hydroelectricity is one of the options currently among non-global warming energy choices to build in large capacities;
• Energy Storage: There is 90 GW of global pumped hydro storage already exist-
ing in the world, and with increasing solar and wind energy, this capacity is only going to grow. The main use of pumped hydro storage is for grid energy storage. Electric utilities are the main customers of this technology for (a) load balancing, this means storing power during low usage periods and generating power at high usage periods; (b) accommodation of intermittent sources of energy. Solar energy and wind energy are growing at a scorching fast rate between 50 and 30 % over the last several years. The larger share of these forms of renewable energy in the electricity mix is driving the growth grid storage; and (c) reducing capital invest- ments as peak power plants such as natural gas combined cycle plants are much more expensive to run than normal thermal and nuclear energy plants;
• Agriculture: Hydropower was used in ancient times for producing flour from grain and was also used for sawing timber and stone, raised water into irrigation canals;
• Industry: Hydropower was used earlier for some industrial applications such as
driving the bellows in small blast furnaces and for extraction of metal ores in a method known as hushing.
3.7.1 Hydroelectric Energy Advantages
The use of hydropower plants for the generation of electricity has some advan- tages over other energy sources. Some of these advantages are the following:
• No Fuel Cost: The use of hydropower plants for the generation of electric- ity does not require any fuel like most other sources of energy. This is a huge advantage over other fossil fuels whose costs are increasing at a drastic rate every year. Electricity prices are increasingly rapidly in most parts of the world much faster than general inflation;
• Low Operating and Maintenance Costs: Operating labor cost is also usu-
ally low, as plants are automated and have few personnel on site during normal operation;
• Lower Electricity Cost: The cost of the electricity produced from hydropower
is quite low, making it very attractive to construct hydropower plants. The pay- back period is estimated to be between five and eight years for a normal hydro- power plant. Hydropower plants also have long life between 40 and 100 years, which means that they are extremely profitable;
• No Greenhouse Gas Emissions: Hydroelectricity does not produce any green-
house gas emissions or cause air pollution from the combustion of fossil fuels unlike coal and oil. This makes them very attractive as a source of cheap, non- carbon dioxide producing electricity;
• Energy Storage: Pumped hydro storage is possible with some type of hydro- power plants. This makes them ideal storage for wind and solar power, which are intermittent in nature. Hydro dams can be modified at low costs to allow pumped storage;
• Small Size Possible: Hydroelectricity can be produced in almost any size from 1 to 10,000 MW, which makes it very versatile. Small hydropower plants are being encouraged by the governments in several countries, particularly in Europe, as they cause less ecological affects than large-scale hydropower plants. Even micro-hydropower plants are possible;
• Reliability: Hydropower is much more reliable than wind and solar
power, though less than coal and nuclear as a base-load source of power. Hydroelectricity is more or less predictable much in advance though it can decrease in summer months when the water is low in the catchment areas;
• High Load Factor: The load factor for solar and wind energy ranges from 15 to 40 %, which is quite low compared to fossil fuel energy. Hydroelectricity, on the other hand, has a load factor of almost 40–60 %;
• Long Life: Hydropower plants have a very long life of around 40–100 years,
which is much longer than that of even nuclear power plants. The long life implies that the life cycle cost of a hydropower plant becomes very low in the long term.
3.7.2 Hydroelectric Energy Disadvantages
The main disadvantages of the hydropower systems are the following:
• Ecosystem damage and loss of land. Hydropower plants that use dams would submerge large areas of land due to the requirement of a reservoir. Large res- ervoirs required for the operation of hydropower plants result in the submersion of extensive areas upstream of the dams, destroying biologically rich and productive lowland and riverine valley forests, marshland, and grasslands. The loss of land is often exacerbated by habitat fragmentation of surrounding areas caused by the reservoir (Robbins 2007);
• Hydroelectric projects can be disruptive to surrounding aquatic eco- systems, both upstream and downstream of the plant site. Generation of hydroelectric power changes the downstream river environment. Water exiting a turbine usually contains very little suspended sediment, which can lead to scouring of riverbeds and loss of riverbanks. Since turbine gates are often opened intermittently, rapid or even daily fluctuations in river flow are observed;
• Siltation and flow shortage. When water flows, it has the ability to transport particles heavier than itself downstream. This has a negative effect on dams and subsequently their power plants, particularly those on rivers or within catchment areas with high siltation. Siltation can fill a reservoir and reduce its capacity to control floods along with causing additional horizontal pressure on the upstream portion of the dam. Eventually, some reservoirs can become full of sediment and useless or overtop during a flood and fail (Patrick 1998; Șentürk 1994);
• Changes in the amount of river flow will correlate with the amount of
energy produced by a dam. Lower river flows will reduce the amount of live storage in a reservoir, therefore, reducing the amount of water that can be used for hydroelectricity. The result of diminished river flow can be power shortages in areas that depend heavily on hydroelectric power. The risk of flow short- age may increase as a result of climate change. One study from the Colorado River in the USA suggests that modest climate changes, such as an increase in temperature in 2 °C resulting in a 10 % decline in precipitation, might reduce river runoff by up to 40 %. Brazil in particular is vulnerable due to its heaving reliance on hydroelectricity, as increasing temperatures, lower water flow, and alterations in the rainfall regime could reduce total energy production by 7 % annually by the end of the century (Urban 2011);
• Methane emissions (from reservoirs). The Hoover dam in the USA is a large conventional dammed-hydro facility, with an installed capacity of 2‚080 MW. Lower positive impacts are found in the tropical regions, as it has been noted that the reservoirs of power plants in tropical regions produce substantial amounts of methane. This is due to plant material in flooded areas decaying in an anaerobic environment and forming methane, a greenhouse gas. According to the World Commission on Dams report, where the reservoir is large com- pared to the generating capacity (less than 100 W/m2 of surface area) and no clearing of the forests in the area was undertaken prior to impoundment of the reservoir, greenhouse gas emissions from the reservoir may be higher than those of a conventional oil-fired thermal generation plant;
• Relocation. Another disadvantage of hydroelectric dams is the need to relo- cate the people living where the reservoirs are planned. In 2000, the World Commission on Dams estimated that the dams had physically displaced 40–80 million people worldwide (World Commission on Dams 2008).
• Failure risks. Because large conventional dammed-hydropower plants hold back large volumes of water, a failure due to poor construction, natural dis- asters, or sabotage can be catastrophic to downriver settlements and infra- structure. Dam failures have been some of the largest man-made disasters in history. The Banqiao dam failure in Southern China directly resulted in the deaths of 26,000 people and another 145,000 from epidemics. Millions were left homeless. Also, the creation of a dam in a geologically inappropriate location may cause disasters such as 1963 disaster at Vajont dam in Italy, where almost 2,500 people died. Smaller dams and micro-hydropower plants create less risk, but can form continuing hazards even after being decommissioned.