Misplaced Pages

#434565

109-607: The Glendoe Hydro Scheme for the generation of hydro-electric power is located in the Monadhliath Mountains near Fort Augustus , above Loch Ness in the Highlands of Scotland . The change in financial incentives following the publication of the Renewables Obligation in 2001 caused Scottish and Southern Energy (SSE) to reconsider a number of schemes that had been mothballed in the 1960s by

218-484: A gigawatt each. They generate about a third of the world's electricity , but cause many illnesses and the most early deaths per unit of energy produced, mainly from air pollution . World installed capacity doubled from 2000 to 2023 and increased 2% in 2023. A coal-fired power station is a type of fossil fuel power station . The coal is usually pulverized and then burned in a pulverized coal-fired boiler . The furnace heat converts boiler water to steam , which

327-545: A magnet . Central power stations became economically practical with the development of alternating current (AC) power transmission, using power transformers to transmit power at high voltage and with low loss. Commercial electricity production started with the coupling of the dynamo to the hydraulic turbine. The mechanical production of electric power began the Second Industrial Revolution and made possible several inventions using electricity, with

436-407: A "mole" or a "worm", is a machine used to excavate tunnels . Tunnels are excavated through hard rock, wet or dry soil, or sand , each of which requires specialized technology. Tunnel boring machines are an alternative to drilling and blasting (D&B) methods and "hand mining". TBMs limit the disturbance to the surrounding ground and produce a smooth tunnel wall. This reduces the cost of lining

545-616: A boring diameter of 6.67 m (21.9 ft). The medium was water saturated sandy mudstone, schistose mudstone, highly weathered mudstone as well as alluvium. It achieved a maximum advance rate of more than 345 m (1,132 ft) per month. The world's largest hard rock TBM, known as Martina , was built by Herrenknecht AG . Its excavation diameter was 15.62 m (51.2 ft), total length 130 m (430 ft); excavation area of 192 m (2,070 sq ft), thrust value 39,485 t, total weight 4,500 tons, total installed capacity 18 MW. Its yearly energy consumption

654-472: A competition by local schoolchildren. There is a drop of 1,970 feet (600 m) from the reservoir to the turbine house, and most of the headrace tunnel slopes uphill at a gradient of 12 per cent. The hard rock tunnel boring machine started at the bottom end in September 2006 and worked continuously for 16 months to reach the top on 7 January 2008, having cut through 4.675 miles (7.524 km) of rock. There

763-451: A formal opening of the scheme took place on 29 June 2009, at which Queen Elizabeth accompanied by Prince Philip, Duke of Edinburgh officiated. The power station is operated remotely from SSE's control centre in Perth . In August 2009 the station was shut down and the headrace tunnel drained because of internal rock falls near the upper end of it. Although the equipment in the power station

872-451: A generator are photovoltaic solar and fuel cells . Almost all commercial electrical power on Earth is generated with a turbine , driven by wind, water, steam or burning gas. The turbine drives a generator, thus transforming its mechanical energy into electrical energy by electromagnetic induction. There are many different methods of developing mechanical energy, including heat engines , hydro, wind and tidal power. Most electric generation

981-645: A generator to rotate. Electrochemistry is the direct transformation of chemical energy into electricity, as in a battery . Electrochemical electricity generation is important in portable and mobile applications. Currently, most electrochemical power comes from batteries. Primary cells , such as the common zinc–carbon batteries , act as power sources directly, but secondary cells (i.e. rechargeable batteries) are used for storage systems rather than primary generation systems. Open electrochemical systems, known as fuel cells , can be used to extract power either from natural fuels or from synthesized fuels. Osmotic power

1090-461: A high amenity value, but the exception was Glendoe. Various configurations were then considered, from a small run-of-the-river scheme generating under 10 MW, to a huge pumped storage scheme. The smaller schemes were discarded because of the cost of transferring the water from the Glendoe plateau down to Loch Ness, while the pumped storage option was discarded because it would not qualify under

1199-408: A huge amount of power from a single unit. However, nuclear disasters have raised concerns over the safety of nuclear power, and the capital cost of nuclear plants is very high. Hydroelectric power plants are located in areas where the potential energy from falling water can be harnessed for moving turbines and the generation of power. It may not be an economically viable single source of production where

SECTION 10

#1732794363435

1308-542: A large number of consumers. Most power plants used in centralised generation are thermal power plants meaning that they use a fuel to heat steam to produce a pressurised gas which in turn spins a turbine and generates electricity. This is the traditional way of producing energy. This process relies on several forms of technology to produce widespread electricity, these being natural coal, gas and nuclear forms of thermal generation. More recently solar and wind have become large scale. A photovoltaic power station , also known as

1417-460: A leading shield that advances with the cutting head and a trailing shield that acts as a gripper. The two shields can move axially relative to each other (i.e., telescopically) over a limited distance. The gripper shield anchors the TBM so that pressure can be applied to the cutter head while simultaneously the concrete lining is being constructed. In hard rock with minimal ground water, the area around

1526-435: A plug to form in the screw. The cutter head is filled with pressurised slurry, typically made of bentonite clay that applies hydrostatic pressure to the face. The slurry mixes with the muck before it is pumped to a slurry separation plant, usually outside the tunnel. Slurry separation plants use multi-stage filtration systems that separate spoil from slurry to allow reuse. The degree to which slurry can be 'cleaned' depends on

1635-536: A prime source of power within isolated villages. Total world generation in 2021 was 28,003 TWh, including coal (36%), gas (23%), hydro (15%), nuclear (10%), wind (6.6%), solar (3.7%), oil and other fossil fuels (3.1%), biomass (2.4%) and geothermal and other renewables (0.33%). China produced a third of the world's electricity in 2021, largely from coal. The United States produces half as much as China but uses far more natural gas and nuclear. Variations between countries generating electrical power affect concerns about

1744-484: A rotating drum with metal tines on its outer surface, or a rotating circular plate covered with teeth, or revolving belts covered with metal teeth. However, these TBMs proved expensive, cumbersome, and unable to excavate hard rock; interest in TBMs therefore declined. Nevertheless, TBM development continued in potash and coal mines, where the rock was softer. A TBM with a bore diameter of 14.4 m (47 ft 3 in)

1853-441: A scale of at least 1 MW p . As of 2018, the world's largest operating photovoltaic power stations surpassed 1 gigawatt . At the end of 2019, about 9,000 solar farms were larger than 4 MW AC (utility scale), with a combined capacity of over 220 GW AC . A wind farm or wind park, or wind power plant, is a group of wind turbines in the same location used to produce electricity . Wind farms vary in size from

1962-402: A single cylindrical shield after the cutting head. A permanent concrete lining is constructed immediately after the shield, and the TBM pushes off the lining to apply force to the cutter head. Because this pushing cannot be done while a next ring of lining is being constructed, the single-shield TBM operates in alternating cutting and lining modes. Double Shield (or telescopic shield) TBMs have

2071-544: A small number of turbines to several hundred wind turbines covering an extensive area. Wind farms can be either onshore or offshore . Many of the largest operational onshore wind farms are located in China, India, and the United States. For example, the largest wind farm in the world , Gansu Wind Farm in China had a capacity of over 6,000  MW by 2012, with a goal of 20,000 MW by 2020. As of December 2020,

2180-465: A solar park, solar farm, or solar power plant, is a large-scale grid-connected photovoltaic power system (PV system) designed for the supply of merchant power . They are different from most building-mounted and other decentralized solar power because they supply power at the utility level, rather than to a local user or users. Utility-scale solar is sometimes used to describe this type of project. This approach differs from concentrated solar power ,

2289-818: A speed and safety not previously possible. The Channel Tunnel , the Thames Water Ring Main , sections of the London Underground , and most new metro tunnels completed in the last 20 years worldwide were excavated using this method. EPB has historically competed with the slurry shield method (see below), where the slurry is used to stabilize the tunnel face and transport spoil to the surface. EPB TBMs are mostly used in finer ground (such as clay) while slurry TBMs are mostly used for coarser ground (such as gravel). Slurry shield machines can be used in soft ground with high water pressure or where granular ground conditions (sands and gravels) do not allow

SECTION 20

#1732794363435

2398-461: A surge shaft, and so the engineering needed to cope with pressure changes would have been complex. A Pelton turbine takes longer to bring online or offline, but deflectors can be used so that the turbine stops before the water flow does, which significantly reduces pressure surges. SSE decided that they could cope with the slower response time, as the benefits of the Pelton system's simplicity outweighed

2507-471: A tunnel boring machine should be used to excavate the tunnel. This would give a much smoother finish to the walls of the tunnel, and only around 40 per cent would need to be lined. Decisions as to how much lining to apply were taken once the rock could be seen, and less than one percent was actually lined. The completed tunnel was carefully inspected by Hochtief, Pöyry, Jacobs and SSE before being signed off. After about 8 months of use, some 233 feet (71 m) of

2616-420: Is 820 feet (250 m) below the surface, at a level where the tailrace to Loch Ness is almost horizontal. A 5.3-mile (8.5 km) tunnel connects the reservoir to Loch Ness, with the turbines about 1.2 miles (2 km) from the loch. Some of it was cut by drill-and-blast, but the majority was created by a 16-foot (5 m) diameter tunnel boring machine, 720 feet (220 m) long and named " Eliza Jane " after

2725-462: Is a possibility at places where salt and fresh water merge. The photovoltaic effect is the transformation of light into electrical energy, as in solar cells . Photovoltaic panels convert sunlight directly to DC electricity. Power inverters can then convert that to AC electricity if needed. Although sunlight is free and abundant, solar power electricity is still usually more expensive to produce than large-scale mechanically generated power due to

2834-457: Is a second smaller cavern which houses the transformers next to the turbine house cavern, and the complex is accessed by a tunnel 0.8 miles (1.3 km) long, running from near the B862 road from Fort Augustus. For schemes between 50 MW and 100 MW, the tunnels would need to be a similar size, as making them smaller also makes building them more difficult. The cost of building either scheme

2943-546: Is a smaller equivalent to a general tunnelling shield and generally bore tunnels of 1 to 1.5 meters (3.3 to 4.9 ft), too small for operators to walk in. Behind all types of tunnel boring machines, in the finished part of the tunnel, are trailing support decks known as the backup system, whose mechanisms can include conveyors or other systems for muck removal; slurry pipelines (if applicable); control rooms; electrical, dust-removal and ventilation systems; and mechanisms for transport of pre-cast segments. Urban tunnelling has

3052-468: Is based upon the local power requirement and the fluctuations in demand. All power grids have varying loads on them. The daily minimum is the base load , often supplied by plants which run continuously. Nuclear, coal, oil, gas and some hydro plants can supply base load. If well construction costs for natural gas are below $ 10 per MWh, generating electricity from natural gas is cheaper than generating power by burning coal. Nuclear power plants can produce

3161-975: Is driven by heat engines. The combustion of fossil fuels supplies most of the energy to these engines, with a significant fraction from nuclear fission and some from renewable sources . The modern steam turbine , invented by Sir Charles Parsons in 1884, currently generates about 80% of the electric power in the world using a variety of heat sources. Turbine types include: Turbines can also use other heat-transfer liquids than steam. Supercritical carbon dioxide based cycles can provide higher conversion efficiency due to faster heat exchange, higher energy density and simpler power cycle infrastructure. Supercritical carbon dioxide blends , that are currently in development, can further increase efficiency by optimizing its critical pressure and temperature points. Although turbines are most common in commercial power generation, smaller generators can be powered by gasoline or diesel engines . These may used for backup generation or as

3270-579: Is faced with concrete, while the downstream side is exposed rock. The dam cannot be seen from any of the houses and public roads in the area. The catchment for the reservoir is around 5.8 square miles (15 km) as it is fed by the upper reaches of the River Tarff, the Caochan Uilleim, and runoff from the A' Chraidhleag bog. Water is collected from another 23 square miles (60 km) by intakes constructed on numerous streams, and transporting

3379-511: Is fundamentally the opposite of distributed generation . Distributed generation is the small-scale generation of electricity to smaller groups of consumers. This can also include independently producing electricity by either solar or wind power. In recent years distributed generation as has seen a spark in popularity due to its propensity to use renewable energy generation methods such as rooftop solar . Centralised energy sources are large power plants that produce huge amounts of electricity to

Glendoe Hydro Scheme - Misplaced Pages Continue

3488-735: Is not freely available in nature, so it must be "produced", transforming other forms of energy to electricity. Production is carried out in power stations , also called "power plants". Electricity is most often generated at a power plant by electromechanical generators , primarily driven by heat engines fueled by combustion or nuclear fission , but also by other means such as the kinetic energy of flowing water and wind. Other energy sources include solar photovoltaics and geothermal power . There are exotic and speculative methods to recover energy, such as proposed fusion reactor designs which aim to directly extract energy from intense magnetic fields generated by fast-moving charged particles generated by

3597-577: Is provided by batteries. Other forms of electricity generation used in niche applications include the triboelectric effect , the piezoelectric effect , the thermoelectric effect , and betavoltaics . Electric generators transform kinetic energy into electricity. This is the most used form for generating electricity based on Faraday's law . It can be seen experimentally by rotating a magnet within closed loops of conducting material, e.g. copper wire. Almost all commercial electrical generation uses electromagnetic induction, in which mechanical energy forces

3706-472: Is rated in megawatt-peak (MW p ), which refers to the solar array's theoretical maximum DC power output. In other countries, the manufacturer states the surface and the efficiency. However, Canada, Japan, Spain, and the United States often specify using the converted lower nominal power output in MW AC , a measure more directly comparable to other forms of power generation. Most solar parks are developed at

3815-429: Is then used to spin turbines that turn generators . Thus chemical energy stored in coal is converted successively into thermal energy , mechanical energy and, finally, electrical energy . Natural gas is ignited to create pressurised gas which is used to spin turbines to generate electricity. Natural gas plants use a gas turbine where natural gas is added along with oxygen which in turn combusts and expands through

3924-417: Is therefore similar, and SSE took the decision to go with the larger size, as it also has significant operational benefits. Consideration was given to using a fully-pressurised Francis turbine or a multi-jet Pelton turbine . While a Francis turbine can be brought online and offline more quickly, the slope of the ground between the reservoir and the turbine house meant that there were no suitable sites to build

4033-468: The Alps , Maus had it built in 1846 in an arms factory near Turin . It consisted of more than 100 percussion drills mounted in the front of a locomotive-sized machine, mechanically power-driven from the entrance of the tunnel. The Revolutions of 1848 affected the funding, and the tunnel was not completed until 10 years later, by using less innovative and less expensive methods such as pneumatic drills . In

4142-634: The Mersey River . The Hudson River Tunnel was constructed from 1889 to 1904 using a Greathead shield TBM. The project used air compressed to 2.4 bar (35 psi) to reduce cave-ins. However, many workers died via cave-in or decompression sickness. During the late 19th and early 20th century, inventors continued to design, build, and test TBMs for tunnels for railroads, subways, sewers, water supplies, etc. TBMs employing rotating arrays of drills or hammers were patented. TBMs that resembled giant hole saws were proposed. Other TBMs consisted of

4251-675: The North of Scotland Hydro-Electric Board , and plans for the Glendoe scheme were resurrected. Construction started in 2006, and Hochtief completed the scheme in 2009. It is operated by SSE and was opened on 29 June 2009 by Queen Elizabeth, accompanied by the Duke of Edinburgh. Part of the main headrace tunnel collapsed in August 2009, and remedial work was not completed until 2012, with generation restarting in April. SSE and Hochtief failed to agree on who

4360-676: The Three Mile Island accident , Chernobyl disaster and the Fukushima nuclear disaster illustrate this problem. The table lists 45 countries with their total electricity capacities. The data is from 2022. According to the Energy Information Administration , the total global electricity capacity in 2022 was nearly 8.9 terawatt (TW), more than four times the total global electricity capacity in 1981. The global average per-capita electricity capacity

4469-429: The steam turbine had a massive impact on the efficiency of electrical generation but also the economics of generation as well. This conversion of heat energy into mechanical work was similar to that of steam engines , however at a significantly larger scale and far more productively. The improvements of these large-scale generation plants were critical to the process of centralised generation as they would become vital to

Glendoe Hydro Scheme - Misplaced Pages Continue

4578-499: The 1218 MW Hornsea Wind Farm in the UK is the largest offshore wind farm in the world . Individual wind turbine designs continue to increase in power , resulting in fewer turbines being needed for the same total output. A coal-fired power station or coal power plant is a thermal power station which burns coal to generate electricity . Worldwide there are about 2,500 coal-fired power stations, on average capable of generating

4687-481: The 1880s the popularity of electricity grew massively with the introduction of the Incandescent light bulb . Although there are 22 recognised inventors of the light bulb prior to Joseph Swan and Thomas Edison , Edison and Swan's invention became by far the most successful and popular of all. During the early years of the 19th century, massive jumps in electrical sciences were made. And by the later 19th century

4796-476: The Conagleann Fault Zone, around 1.2 miles (2 km) from the top end of the tunnel. The fault was known from its appearance at surface level, but during tunnelling, the tunnel boring machine had passed through it, and SSE recorded that its existence was imperceptible. A contract for repair work was awarded to BAM Nuttall , who built a diversion tunnel around the rockfall by drill-and-blast. This

4905-487: The Fréjus Rail Tunnel, by using less ambitious methods). Wilson's machine anticipated modern TBMs in the sense that it employed cutting discs, like those of a disc harrow , which were attached to the rotating head of the machine. In contrast to traditional chiseling or drilling and blasting, this innovative method of removing rock relied on simple metal wheels to apply a transient high pressure that fractured

5014-588: The Highlands of Scotland. Subsequently, Cruachan was commissioned in 1968, and Foyers in 1974, but both of these were pumped storage schemes . In 2001, the Scottish Parliament set an objective of increasing the proportion of electricity generated from renewable sources to 18 per cent by 2010, as part of their Scottish Climate Change Programme. The publication of the Renewables Obligation in 2001 made any new hydro-electric scheme eligible under

5123-580: The Northern America in the 1920s in large cities and urban areas. It was not until the 1930s that rural areas saw the large-scale establishment of electrification. 2021 world electricity generation by source. Total generation was 28 petawatt-hours . Several fundamental methods exist to convert other forms of energy into electrical energy. Utility-scale generation is achieved by rotating electric generators or by photovoltaic systems. A small proportion of electric power distributed by utilities

5232-622: The Renewable Obligation scheme, and because the difference in levels between the top reservoir and Loch Ness was sufficient that it would be extremely costly to overcome the issues this would introduce. Once the choice of Glendoe was made in October 2001, an environmental statement was produced and the design was refined by May 2003. SSE then applied for planning consent under section 36 of the Electricity Act 1989 , and this

5341-535: The Tuen Mun Chek Lap Kok link in Hong Kong. TBMs typically consist of a rotating cutting wheel in front, called a cutter head, followed by a main bearing, a thrust system, a system to remove excavated material (muck), and support mechanisms. Machines vary with site geology, amount of ground water present, and other factors. Rock boring machines differ from earth boring machines in the way they cut

5450-597: The United States, fossil fuel combustion for electric power generation is responsible for 65% of all emissions of sulfur dioxide , the main component of acid rain. Electricity generation is the fourth highest combined source of NO x , carbon monoxide , and particulate matter in the US. According to the International Energy Agency (IEA), low-carbon electricity generation needs to account for 85% of global electrical output by 2040 in order to ward off

5559-470: The United States, the first boring machine to have been built was used in 1853 during the construction of the Hoosac Tunnel in northwest Massachusetts. Made of cast iron, it was known as Wilson's Patented Stone-Cutting Machine , after inventor Charles Wilson. It drilled 3 meters (10 ft) into the rock before breaking down (the tunnel was eventually completed more than 20 years later, and as with

SECTION 50

#1732794363435

5668-508: The ability to store the flow of water is limited and the load varies too much during the annual production cycle. Electric generators were known in simple forms from the discovery of electromagnetic induction in the 1830s. In general, some form of prime mover such as an engine or the turbines described above, drives a rotating magnetic field past stationary coils of wire thereby turning mechanical energy into electricity. The only commercial scale forms of electricity production that do not employ

5777-411: The advancement of electrical technology and engineering led to electricity being part of everyday life. With the introduction of many electrical inventions and their implementation into everyday life, the demand for electricity within homes grew dramatically. With this increase in demand, the potential for profit was seen by many entrepreneurs who began investing into electrical systems to eventually create

5886-487: The atmosphere. Nuclear power plants can also create district heating and desalination projects, limiting carbon emissions and the need for expanded electrical output. A fundamental issue regarding centralised generation and the current electrical generation methods in use today is the significant negative environmental effects that many of the generation processes have. Processes such as coal and gas not only release carbon dioxide as they combust, but their extraction from

5995-472: The caisson, requiring workers to be medically cleared as "fit to dive" and able to operate pressure locks. Open face soft ground TBMs rely on the excavated ground to briefly stand without support. They are suitable for use in ground with a strength of up to about 10 MPa (1,500 psi) with low water inflows. They can bore tunnels with cross-section in excess of 10 m (30 ft). A backactor arm or cutter head bore to within 150 mm (6 in) of

6104-510: The complexity of the Francis system. They therefore chose to install an Andritz six-jet vertical-axis Pelton turbine which can generate up to 100 MW, from a peak flow of 660 cubic feet per second (18.6 m/s). Alex Salmond in his role as First Minister of Scotland initiated the filling of the reservoir on 1 September 2008. Hochtief completed the contract two months early, and the station had been generating power since January 2009 when

6213-543: The construction of a tunnel under the English Channel and the British Parliament supported a trial run using English's TBM. Its cutting head consisted of a conical drill bit behind which were a pair of opposing arms on which were mounted cutting discs. From June 1882 to March 1883, the machine tunneled, through chalk, a total of 1,840 m (6,036 ft). A French engineer, Alexandre Lavalley , who

6322-616: The cost of the panels. Low-efficiency silicon solar cells have been decreasing in cost and multijunction cells with close to 30% conversion efficiency are now commercially available. Over 40% efficiency has been demonstrated in experimental systems. Until recently, photovoltaics were most commonly used in remote sites where there is no access to a commercial power grid, or as a supplemental electricity source for individual homes and businesses. Recent advances in manufacturing efficiency and photovoltaic technology, combined with subsidies driven by environmental concerns, have dramatically accelerated

6431-439: The cutter head and extraction screw to ensure that the muck is sufficiently cohesive to maintain pressure and restrict water flow. Like some other TBM types, EPB's use thrust cylinders to advance by pushing against concrete segments. The cutter head uses a combination of tungsten carbide cutting bits, carbide disc cutters, drag picks and/or hard rock disc cutters. EPB has allowed soft, wet, or unstable ground to be tunneled with

6540-437: The cutter head of a TBM can be unpressurized, as the exposed rock face can support itself. In weaker soil, or when there is significant ground water, pressure must be applied to the face of the tunnel to prevent collapse and/or the infiltration of ground water into the machine. Earth pressure balance (EPB) machines are used in soft ground with less than 7 bar (100 psi) of pressure. It uses muck to maintain pressure at

6649-434: The cutter head to support the walls until permanent tunnel support is constructed further along the machine. The stability of the walls also influences the method by which the TBM anchors itself in place so that it can apply force to the cutting head. This in turn determines whether the machine can bore and advance simultaneously, or whether these are done in alternating modes. Gripper TBMs are used in rock tunnels. They forgo

SECTION 60

#1732794363435

6758-499: The cutting discs would travel over almost all of the rock face that was to be removed. The first TBM that tunneled a substantial distance was invented in 1863 and improved in 1875 by British Army officer Major Frederick Edward Blackett Beaumont (1833–1895); Beaumont's machine was further improved in 1880 by British Army officer Major Thomas English (1843–1935). In 1875, the French National Assembly approved

6867-572: The deployment of solar panels. Installed capacity is growing by around 20% per year led by increases in Germany, Japan, United States, China, and India. The selection of electricity production modes and their economic viability varies in accordance with demand and region. The economics vary considerably around the world, resulting in widespread residential selling prices. Hydroelectric plants , nuclear power plants , thermal power plants and renewable sources have their own pros and cons, and selection

6976-504: The design and build contractor. The scheme is predicted to produce about 180  GWh of electricity per year, and to operate at a load factor of approximately 20 percent. This is based on the amount of water falling on the catchment in an average year, and is enough to provide approximately 5% of the electricity consumption of the city of Glasgow . [REDACTED] Media related to Glendoe hydro-electric scheme at Wikimedia Commons Electricity generation Consumable electricity

7085-506: The edge of the shield. After a boring cycle, the shield is jacked forward to begin a new cycle. Ground support is provided by precast concrete, or occasionally spheroidal graphite iron (SGI) segments that are bolted or supported until a support ring has been added. The final segment, called the key, is wedge-shaped, and expands the ring until it is tight against the ground. TBMs range diameter from 1 to 17 meters (3 to 56 ft). Micro tunnel shield TBMs are used to construct small tunnels, and

7194-533: The electricity through high voltage transmission lines to a substation, where it is then distributed to consumers; the basic concept being that multi-megawatt or gigawatt scale large stations create electricity for a large number of people. The vast majority of electricity used is created from centralised generation. Most centralised power generation comes from large power plants run by fossil fuels such as coal or natural gas, though nuclear or large hydroelectricity plants are also commonly used. Centralised generation

7303-467: The end of the 19th century, speeds had reached over 30 meters per week. 21st century rock TBMs can excavate over 700 meters per week, while soil tunneling machines can exceed 200 meters per week. Speed generally declines as tunnel size increases. The first successful tunnelling shield was developed by Sir Marc Isambard Brunel to excavate the Thames Tunnel in 1825. However, this

7412-524: The entire power system that we now use today. Throughout the middle of the 20th century many utilities began merging their distribution networks due to economic and efficiency benefits. Along with the invention of long-distance power transmission , the coordination of power plants began to form. This system was then secured by regional system operators to ensure stability and reliability. The electrification of homes began in Northern Europe and in

7521-404: The environment. In France only 10% of electricity is generated from fossil fuels , the US is higher at 70% and China is at 80%. The cleanliness of electricity depends on its source. Methane leaks (from natural gas to fuel gas-fired power plants) and carbon dioxide emissions from fossil fuel-based electricity generation account for a significant portion of world greenhouse gas emissions . In

7630-428: The first electricity public utilities. This process in history is often described as electrification. The earliest distribution of electricity came from companies operating independently of one another. A consumer would purchase electricity from a producer, and the producer would distribute it through their own power grid. As technology improved so did the productivity and efficiency of its generation. Inventions such as

7739-495: The fusion reaction (see magnetohydrodynamics ). Phasing out coal-fired power stations and eventually gas-fired power stations , or, if practical, capturing their greenhouse gas emissions , is an important part of the energy transformation required to limit climate change . Vastly more solar power and wind power is forecast to be required, with electricity demand increasing strongly with further electrification of transport , homes and industry. However, in 2023, it

7848-420: The generators. Although there are several types of nuclear reactors, all fundamentally use this process. Normal emissions due to nuclear power plants are primarily waste heat and radioactive spent fuel. In a reactor accident, significant amounts of radioisotopes can be released to the environment, posing a long term hazard to life. This hazard has been a continuing concern of environmentalists. Accidents such as

7957-494: The ground also impacts the environment. Open pit coal mines use large areas of land to extract coal and limit the potential for productive land use after the excavation. Natural gas extraction releases large amounts of methane into the atmosphere when extracted from the ground greatly increase global greenhouse gases. Although nuclear power plants do not release carbon dioxide through electricity generation, there are risks associated with nuclear waste and safety concerns associated with

8066-458: The heat input is from the process of nuclear fission . Currently, nuclear power produces 11% of all electricity in the world. Most nuclear reactors use uranium as a source of fuel. In a process called nuclear fission , energy, in the form of heat, is released when nuclear atoms are split. Electricity is created through the use of a nuclear reactor where heat produced by nuclear fission is used to produce steam which in turn spins turbines and powers

8175-468: The highest of any hydro-electric scheme in the United Kingdom, and is thus ideally suited to generating large amounts of energy from the stored water in the reservoir, especially when combined with the relatively high annual rainfall in the area of around 2,000 mm (79 in). At the time of its construction, it was the largest of Scotland's recent civil engineering projects, with Hochtief as

8284-596: The incentive, whereas previously only those under 10  Megawatts  (MW) had qualified. This changed the financial incentives for building new hydro-electric plants, and SSE plc , who inherited most of the Hydro-Electric Board's assets when the electricity industry was privatised, reviewed all of the large schemes that the Board had considered, but which had not been built. Nearly all had been abandoned because of their environmental impact in areas which had

8393-414: The main scheme, various enabling works had to be done. The bridge that carries the B862 road over the River Tarff near Fort Augustus had to be strengthened to cope with the weight of construction vehicles, and this work was done in five weeks starting on 21 November 2005. A refurbished tunnel boring machine was ordered from Herrenknecht, a start was made on the 28 miles (45 km) of roads needed to access

8502-469: The major contributors being Thomas Alva Edison and Nikola Tesla . Previously the only way to produce electricity was by chemical reactions or using battery cells, and the only practical use of electricity was for the telegraph . Electricity generation at central power stations started in 1882, when a steam engine driving a dynamo at Pearl Street Station produced a DC current that powered public lighting on Pearl Street , New York . The new technology

8611-475: The network. When full, the reservoir covers around 0.58 square miles (1.5 km) and its surface is at 2,070 feet (630 m) above Ordnance datum . (AOD). Water is drawn down to a maximum of 20 feet (6 m) below this level when the power station is operating, on environmental grounds. The power station was constructed underground, in a cavern 125 by 59 feet (38 by 18 m) and 105 feet (32 m) high, excaved from solid rock by drill-and-blast. The cavern

8720-425: The other major large-scale solar generation technology, which uses heat to drive a variety of conventional generator systems. Both approaches have their own advantages and disadvantages, but to date, for a variety of reasons, photovoltaic technology has seen much wider use. As of 2019 , about 97% of utility-scale solar power capacity was PV. In some countries, the nameplate capacity of photovoltaic power stations

8829-455: The process. The turbine house might be above or below ground, the output of the scheme could be between 50 MW and 100 MW, while the dam could be constructed of rockfill or roller compacted concrete. A contract for the scheme was awarded to Hochtief in December 2005, and they began producing the detailed designs and starting construction from January 2006. Before work could start on

8938-407: The relative particle sizes of the muck. Slurry TBMs are not suitable for silts and clays as the particle sizes of the spoil are less than that of the bentonite. In this case, water is removed from the slurry leaving a clay cake, which may be polluted. A caisson system is sometimes placed at the cutting head to allow workers to operate the machine, although air pressure may reach elevated levels in

9047-464: The reshaping of the valley. A reservoir for the scheme was created by building a dam across the River Tarff . The dam is 3,150 feet (960 m) long, and some 115 feet (35 m) high where it crosses the original course of the river, but much lower at the sides. It is a rock fill dam, with most of the rock coming from a quarry which was flooded as the reservoir filled with water. The upstream side

9156-481: The rock. In 1853, the American Ebenezer Talbot also patented a TBM that employed Wilson's cutting discs, although they were mounted on rotating arms, which in turn were mounted on a rotating plate. In the 1870s, John D. Brunton of England built a machine employing cutting discs that were mounted eccentrically on rotating plates, which in turn were mounted eccentrically on a rotating plate, so that

9265-587: The special requirement that the surface remain undisturbed, and that ground subsidence be avoided. The normal method of doing this in soft ground is to maintain soil pressures during and after construction. TBMs with positive face control, such as earth pressure balance (EPB) and slurry shield (SS), are used in such situations. Both types (EPB and SS) are capable of reducing the risk of surface subsidence and voids if ground conditions are well documented. When tunnelling in urban environments, other tunnels, existing utility lines and deep foundations must be considered, and

9374-477: The tunnel collapsed and was blocked by the rock fall. Robert Galbraith QC was appointed by Hochtief and SSE to adjudicate in 2011, and decided that Hochtief were not to blame for the collapse. Rather than take the dispute to arbitration, where the issues would be judged by technically qualified, professional engineers, SSE chose to pursue the matter in court, where it would be decided on legal issues by judges who were not technically qualified. The collapse occurred in

9483-592: The tunnel face. Main Beam machines do not install concrete segments behind the cutter head. Instead, the rock is held up using ground support methods such as ring beams, rock bolts, shotcrete , steel straps, ring steel and wire mesh. Depending on the stability of the local geology, the newly formed walls of the tunnel often need to be supported immediately after being dug to avoid collapse, before any permanent support or lining has been constructed. Many TBMs are equipped with one or more cylindrical shields following behind

9592-401: The tunnel face. The muck (or spoil ) is admitted into the TBM via a screw conveyor . By adjusting the rate of extraction of muck and the advance rate of the TBM, the pressure at the face of the TBM can be controlled without the use of slurry . Additives such as bentonite , polymers and foam can be injected ahead of the face to stabilize the ground. Such additives can separately be injected in

9701-693: The tunnel, and is suitable for use in urban areas. TBMs are expensive to construct, and larger ones are challenging to transport. These fixed costs become less significant for longer tunnels. TBM-bored tunnel cross-sections range from 1 to 17.6 meters (3.3 to 57.7 ft) to date. Narrower tunnels are typically bored using trenchless construction methods or horizontal directional drilling rather than TBMs. TBM tunnels are typically circular in cross-section although they may be u-shaped, horseshoes, square or rectangular. Tunneling speeds increase over time. The first TBM peaked at 4 meters per week. This increased to 16 meters per week four decades later. By

9810-411: The tunnel, the way they provide traction to support the boring activity, and in the way they support the newly formed tunnels walls. Shielded TBMs are typically used to excavate tunnels in soil. They erect concrete segments behind the TBM to support the tunnel walls. The machine stabilizes itself in the tunnel with hydraulic cylinders that press against the shield, allowing the TBM to apply pressure at

9919-444: The turbine to force a generator to spin. Natural gas power plants are more efficient than coal power generation, they however contribute to climate change, but not as highly as coal generation. Not only do they produce carbon dioxide from the ignition of natural gas, the extraction of gas when mined releases a significant amount of methane into the atmosphere. Nuclear power plants create electricity through steam turbines where

10028-411: The use of a shield and instead push directly against the unreinforced sides of the tunnel. Machines such as a Wirth machine can be moved only while ungripped. Other machines can move continuously. At the end of a Wirth boring cycle, legs drop to the ground, the grippers are retracted, and the machine advances. The grippers then reengage and the rear legs lift for the next cycle. A single-shield TBM has

10137-413: The use of nuclear sources. Per unit of electricity generated coal and gas-fired power life-cycle greenhouse gas emissions are almost always at least ten times that of other generation methods. Centralised generation is electricity generation by large-scale centralised facilities, sent through transmission lines to consumers. These facilities are usually located far away from consumers and distribute

10246-578: The various sites where work was to be carried out, and a planning application was made to allow work camps to be constructed. These were built high up on the Glendoe plateau, and accommodated most of the 750 workers who were employed on the project. A ceremony attended by Tony Blair , the British prime minister , and Jack McConnell , the First Minister of Scotland , marked the formal start of construction. They detonated an explosive charge, to begin

10355-450: The water to the reservoir by a network of underground pipes and tunnels. The main tunnel is 5.3 miles (8.5 km) long, of which 4.3 miles (7 km) were constructed by the drill-and-blast method and lined with shotcrete . The rest was built using the cut-and-cover technique. There are a further 2.5 miles (4 km) of 6.6-foot (2 m) diameter pipe to complete the network. Water is collected from at least 14 intakes which feed into

10464-698: The worst effects of climate change. Like other organizations including the Energy Impact Center (EIC) and the United Nations Economic Commission for Europe (UNECE), the IEA has called for the expansion of nuclear and renewable energy to meet that objective. Some, like EIC founder Bret Kugelmass, believe that nuclear power is the primary method for decarbonizing electricity generation because it can also power direct air capture that removes existing carbon emissions from

10573-608: Was about 1,120 watts in 2022, nearly two and a half times the global average per-capita electricity capacity in 1981. Iceland has the highest installed capacity per capita in the world, at about 8,990 watts. All developed countries have an average per-capita electricity capacity above the global average per-capita electricity capacity, with the United Kingdom having the lowest average per-capita electricity capacity of all other developed countries. Tunnel boring machine A tunnel boring machine ( TBM ), also known as

10682-679: Was about 62 GWh. It is owned and operated by the Italian construction company Toto S.p.A. Costruzioni Generali (Toto Group) for the Sparvo gallery of the Italian Motorway Pass A1 ("Variante di Valico A1"), near Florence. The same company built the world's largest-diameter slurry TBM , excavation diameter of 17.6 meters (58 ft), owned and operated by the French construction company Dragages Hong Kong (Bouygues' subsidiary) for

10791-592: Was also a Suez Canal contractor , used a similar machine to drill 1,669 m (5,476 ft) from Sangatte on the French side. However, despite this success, the cross-Channel tunnel project was abandoned in 1883 after the British military raised fears that the tunnel might be used as an invasion route. Nevertheless, in 1883, this TBM was used to bore a railway ventilation tunnel — 2 m (7 ft) in diameter and 2.06 km (6,750 ft) long — between Birkenhead and Liverpool , England, through sandstone under

10900-461: Was eventually granted in June 2005. Although there were few objections to the scheme, and the local community was supportive, SSE did not know how long the planning consent process would take, and so began a design and build tendering process which ran concurrently. Because they could not undertake investigative work until deals with the landowners had been agreed, the design was kept flexible throughout

11009-480: Was full-lined with 20 inches (500 mm) of waterproof concrete, and they also applied a 4-inch (100 mm) concrete lining to almost half of the rest of the tunnel. A downstream access tunnel was also built as part of the repair contract. Energy generation at the scheme restarted in August 2012. SSE issued proceedings seeking to recover £130 million in repair and reinstatement costs and £65 million in alleged loss of profit from Hochtief, but in December 2016 Hochtief

11118-613: Was held by the Scottish Court of Session not to have been liable for the collapse, and that it was an operational risk to be borne by SSE. In an appeal decided in 2018, SSE were awarded more than £107 million in compensation. The judges hearing the appeal split 2-to-1 in SSE's favour. Hochtief subsequently appealed, and the case will be heard by the Supreme Court . Glendoe has a hydraulic head of 600 m (2,000 ft),

11227-480: Was manufactured by The Robbins Company for Canada's Niagara Tunnel Project . The machine was used to bore a hydroelectric tunnel beneath Niagara Falls . The machine was named "Big Becky" in reference to the Sir Adam Beck hydroelectric dams to which it tunnelled to provide an additional hydroelectric tunnel. An earth pressure balance TBM known as Bertha with a bore diameter of 17.45 meters (57.3 ft)

11336-437: Was not affected, Glendoe was unable to generate power until repairs were made. SSE reported that electricity generation was unlikely to proceed until at least April 2011. SSE employed Jacobs Gibb and Jacobs UK as their engineers, and the original designs were for a fully-lined tunnel constructed by drill-and-blast. However, during the tendering process, Pöyry Energy JV who were the design engineers for Hochtief recommended that

11445-585: Was only the invention of the shield concept and did not involve the construction of a complete tunnel boring machine, the digging still having to be accomplished by the then standard excavation methods. The first boring machine reported to have been built was Henri Maus 's Mountain Slicer . Commissioned by the King of Sardinia in 1845 to dig the Fréjus Rail Tunnel between France and Italy through

11554-481: Was produced by Hitachi Zosen Corporation in 2013. It was delivered to Seattle , Washington , for its Highway 99 tunnel project . The machine began operating in July 2013, but stalled in December 2013 and required substantial repairs that halted the machine until January 2016. Bertha completed boring the tunnel on April 4, 2017. Two TBMs supplied by CREG excavated two tunnels for Kuala Lumpur 's Rapid Transit with

11663-497: Was quickly adopted by many cities around the world, which adapted their gas-fueled street lights to electric power. Soon after electric lights would be used in public buildings, in businesses, and to power public transport, such as trams and trains. The first power plants used water power or coal. Today a variety of energy sources are used, such as coal , nuclear , natural gas , hydroelectric , wind , and oil , as well as solar energy , tidal power , and geothermal sources. In

11772-409: Was reported that the global electricity supply was approaching peak CO2 emissions thanks to the growth of solar and wind power. The fundamental principles of electricity generation were discovered in the 1820s and early 1830s by British scientist Michael Faraday . His method, still used today, is for electricity to be generated by the movement of a loop of wire, or Faraday disc , between the poles of

11881-409: Was responsible for the cost of the failure, but SSE were awarded damages in 2018 in the court of appeal, despite an adjudication and the first court case finding that the cost was an operational risk to be borne by SSE. The completion of several schemes by the North of Scotland Hydro-Electric Board in the early 1960s brought to an end over two decades of expansion of conventional hydro-electricity in

#434565