Electric Power Consumers and Power System

Electric Power Consumers and Power System

1. An electric power consumer is an enterprise utilizing electric power. Its operating characteristics vary during the hours of day, days and nights, days of week and seasons.

2. All electric power consumers are divided into groups with common load characteristics. To the first group belong municipal consumers with a predominant lighting load: dwelling houses, hospitals,

theatres, street lighting systems, mines, etc.

3. To the second group belong industrial consumers with a predominant power load (electric motors): industrial plants, mines, etc.

4. To the third group belongs transport, for example, electrified railways. The fourth consists of agricultural consumers, for example, electrotractors.

5. The operating load conditions of each group are determined by the load graph. The load graph shows the consumption of power during different periods of day, month, and year. On the load graph the time of

the maximum loads and minimum loads is given.

6. Large industrial areas with cities are supplied from electric networks fed by electric power plants. These plants are interconnected for operation in parallel and located in different parts of the given area.

They may include some large thermal and hydroelectric power plants.

7. The sum total of the electric power plants, the networks that interconnect them and the power utilizing devices of the consumers, is called a power system. All the components of a power system are inter-35

related by the common processes of protection, distribution, and consumption of both electric and heat power.

8. In a power system, all the parallelly operating plants take part in carrying the total load of all the consumers supplied  by the given system.

9. The building up of a power system is of great importance for the national economy. An economical utilization of the power plant installations and of the sources of power is achieved by interconnected operation of a series of power plants in a common power distribution system.

Electric Power Plants

1. Electric power is generated at electric power plants. The main unit of an electric power plant comprises a prime mover and the generator which it rotates. In order to actuate the prime mover energy is required. Many different sources of energy are in use nowadays. To these sources belong heat obtained by burning fuels, pressure due to the flow of air (wind), solar heat, etc.

2. According to the kind of energy used by the prime mover, power plants are divided into groups. Thermal, hydraulic (water-power) and wind plants form these groups.37

3. According to the kind of prime mover, electric power plants are classed as

a) Steam turbine plants, where steam turbines serve as prime

movers. The main generating units at steam turbine plants are the turbogenerators. Steam turbine plants belong to the modern, high-capacity class of power plants.

b) Steam engine plants, in which the prime mover is a pistontype steam engine. Nowadays no large generating plants of industrial importance are constructed with such prime movers. They are used only

for local power supply.

c) Diesel-engine plants in them diesel internal combustion engines are installed. These plants are also of small capacity, they are employed for local power supply.

d) Hydroelectric power plants employ water turbines as prime movers. Therefore they are called hydroturbine plants. Their main generating unit is the hydrogenerator.

4. Modern wind-electric power plants utilize various turbines; these plants as well as the small capacity hydroelectric power plants are widely used in agriculture.

Hydroelectric Power Plants

1. Hydroelectric power plants are built on rivers. Large-capacity hydroelectric power plants  are commonly located at considerable distances from the consumers of electric power.

2. The production process at these plants is rather simple: the water flows into the hydroturbine runner, acts upon the runner blades and rotates the runner and the turbine shaft.

3. The generator shaft is connected to the turbine runner shaft The difference in the water level influences the power capacity of a plant, i. e. the magnitude of the water head and the daily inflow of water fluctuates considerably according to the season.39

4.The production process is different at power plants of different constructions and of different kinds. In atomic power plants, for example, it is not so simple as in hydroelectric plants.

Atomic Electric Power Plant

1. Atomic power plants are modern installations. They consist of several main units and a great number of auxiliary ones.

2. In a nuclear reactor uranium is utilized as a fuel. During operation process powerful heat and radioactive radiation are produced. The nuclear reactor is cooled by water circulation. Cooling water circulates through a system of tubes, in which the water is heated to a temperature of 250–300 °C. In order to prevent boiling of water, it passes into the reactor at a pressure up to 150 atmospheres.

3. A steam generator includes a series of heat exchangers comprising tubes. The water heated in the reactor is delivered into the heat exchanger tubes. The water to be converted into steam flows outside thesetubes. The steam produced is fed into the turbogenerator.

4. Besides, an atomic power plant comprises a common turbogenerator, a steam condenser with circulating water and a switchboard.41

5. Atomic power plants have their advantages as well as disadvantages. The reactors and steam generators operate in them noiselessly; the atmosphere is not polluted by dust and smoke. As to the fuel consumption, it is of no special importance and there is no problem of fuel transportation.

6. The disadvantage of power plants utilizing nuclear fuel is their radiation. Radioactive radiation produced in the reactors is dangerous for attending personnel. Therefore, the reactors and steam generators are installed underground. They are also shielded by thick (up to 1.5 m)

concrete walls. All their controls are operated by means of automatic devices. These measures serve to protect people from radioactive radiation.

Thermal Power-Station

1. A modern thermal power-station is known to consist of four principal components namely, coal handling and storage, boiler house, turbine house, switchgear.

2. If you have not seen a power-station boiler it will be difficult for you to imagine its enormous size.43

3. Besides the principal components mentioned above there are many additional parts of the plant. The most important of them is the turbogenerator in which the current is actually generated.

4. A steam turbine requires boilers to provide steam. Boilers need a coal-handling plant on the one hand and an ash-disposal plant on the other. Large fans are quite necessary to provide air for the furnaces. Water for the boilers requires feed pumps. Steam must be condensed after it has passed through the turbines, and this requires large quantities of cooling water. The flue gases carry dust which must be removed by cleaning the gases before they go into the open air.

5. A modern thermal power-station is equipped with one or more turbine generator units which convert heat energy into electric energy. The steam to drive the turbine which, in its turn, turns the rotor or revolving part of the generator is generated in boilers heated by furnaces in which one of three fuels may be used–coal, oil and natural gas. Coal continues to be the most important and the most economical of these fuels.

6. Large installations with mighty turbogenerators are operating at a number of thermal power-stations in Russia. It is necessary to point out that the power machine building industry has started to manufacture

even greater capacity installations for thermal power-stations.

7. At present great attention is paid to combined generation of heat and electricity at heat-and-power plants and to centralized heat supply. One of the world's largest heat-and-power installations is operating at the Moskowskaya thermal power-station-25.

8. Thermal power-stations are considered to be the basis of power industry. More than 80% of the country's total power output comes from the above stations.It is necessary to say that separate power-stations in our country are integrated into power systems. Integration of power systems is a

higher stage in scientific and technical development of power engineering.

Solar Power Plant

1. This project has supported the construction of a PV power plant, which is the first of its type in the world. All the components of the plant were developed during the previous projects and now, in this latest

project, the size of the concentrators has been increased to full commercial dimensions. These new, modular units consist of two 75 metres long rows of PV cells. The new units use reflecting instead of refracting technology, have single-axis tracking and encapsulated modules.

2. The new plant, named EUCLIDES, has eight units, each with two rows of concentrators 72 metres long and 2.9 metres wide. The two rows in each unit share a single tracking carriage. Each unit is rated at

62 kWp, giving a total rating of 480 kWp. Each tracker has an output of 750 V. In the concentrator units themselves, the cells are interconnected and encapsulated, just like flat modules, and the concentration of optics are mirrors instead of the Fresnsel lenses used in all previous PV units.

3. The new design provides a more constant output than that from flat panels, and this means that a better price should be obtained for the electricity produced.

4. There is a growing interest in green electricity (generated from renewable sources) among consumers. In the Netherlands, increasingdemand from consumers for PV systems to supply electricity at their

own premises offers an opportunity to market centralised PV system, which have, until recently, gained little support. More development work needs to be done to improve the appropriate technology for grid

connected PV systems and this project will bring together Italian electricity company ENEL, with their expertise in the operation of centralised PV systems and the marketing expertise of Dutch energy company EDON. The technology will be demonstrated to the general public and

commercial end-users.

5. The new system, the first ground-based central PV system in the Netherlands, will be installed on top of a concrete storage tank for drinking water, and will consist of three units, each with a capacity of

60 kWp, giving a total capacity of 180 kWp. This project aims to de-46monstrate the role that sales of green electricity can play in driving the development of PV, and other renewable projects.

Lunar Solar Power System

1. Approximately 6 kWt/person or, eventually, 2 kWe/person can enable energy prosperity. Note that "t" refers to thermal energy and "c" to electric energy. For a population of 10 billion people, anticipated by

2050, this implies 60,000 GWt or 20,000 GWe. For purposes of discussion, assume that power usage continues to be high to 2070. From 2000 to 2070 the world would consume approximately 3,000,000 GWt Y or 1,000,000 GWe-Y of energy. It is highly unlikely that conventional fossil, nuclear, and terrestrial renewable power systems can provide the power needed by 2050 and the total energy consumed by 2070. They are restricted by limited supplies of fuels, pollution and wastes, irregular 48

supplies of renewable energy, costs of creating and operating the global systems, and other factors.

2. It is technically and economically feasible to provide at least 100,000 GWe of solar electric energy from facilities on the Moon. The Lunar Solar Power (LSP) System can supply to Earth power that is independent of the biosphere and does not introduce CO2,  ash, or other material wastes into the biosphere. Inexhaustible new net electrical energy provided by the LSP System enables the creation of new net material wealth on Earth that is decoupled from the biosphere. Given adequate clean electric power,  humanity's material needs can be acquired from common resources and recycled without the use of depletable fuels. LSP power increases the ability of tomorrow's generations to meet tomorrow's needs, and enables humanity to move beyond simply attempting to sustain itself within the biosphere to nurturing the biosphere.

3. The LSP System uses bases on opposing limbs of the Moon. Each base transmits multiple microwave power beams directly to Earth rectennas when the rectennas can view the Moon. Each base is augmented by fields of photoconverters just across the limb of the Moon. Thus, one of the two bases in the pair can beam power toward Earth over the entire cycle of the lunar day and night. This version of LSP supplies extra energy to a rectenna on Earth while the rectenna can view the Moon. The extra energy is stored and then released when the Moon is not in view.

4. The LSP System is an unconventional approach to supplying commercial power to Earth. Power beams are considered esoteric and a technology of the distant future. However, Earth-to-Moon power beams

of near-commercial intensity are an operational reality.

5. Load-following electrical power, without expensive storage, is highly desirable. Earth orbiting satellites can redirect beams to rectennasthat cannot view the Moon and thus enable load-following power to rectennas located anywhere on Earth. Rectennas on Earth and the lunar transmitters can be sized to permit the use of Earth orbiting redirectors that are 200 m to 1,000 m in diameter. Redirected satellites can be reflectors or retransmitters. The technology is much more mature than realized by the technical community at large.

Tidal Energy

1. Over the past three decades the feasibility of using ocean tides to generate electric power has been investigated at many sites.

2. By far the largest tidal plant in service is Rance (France), with a capacity of 240 MW and an annual output exceeding 500 GWh. Others include the 20 MW Annapolis plant in Canada, several small units in China with total capacity of about 5 MW and a 400 kW experimental unit near Murmansk in Russia.

3. Most designs, existing or proposed, have opted for a single tidal basin to create hydraulic heads and propeller turbines to extract energy therefrom. Linked and paired basins have also been considered. Innovative approaches have included extraction of energy directly from tide races using a variety of prime movers.

4. The main obstacle to development is economic. Capital costs are high in relation to output: a consequence of the low and variable heads available at even the best sites. Heads available at the turbine vary throughout each tidal cycle, averaging less than 70% of the maximum. 51As a result, installed capacity is underutilized, typical capacity factors lending to fall in the range 0.23 to 0.37. Low heads imply that civil as well as mechanical engineering components must be large in comparison to output. For such reasons, tidal plants are likely to be practicable only where energy is concentrated by large tides and where physical features permit construction of tidal basins at low cost.

5. Significant capital-cost reductions through improved design and construction techniques have been achieved over the past three decades. In China a somewhat different approach has been taken: tidal plants

have been built as part of broader schemes of resource utilization – typically land reclamation or aquaculture.

6. In a world increasingly sensitive to environmental factors, tidal plants must avoid unacceptable impacts. Tidal power is non-polluting and in this respect superior to thermal generation. Beyond that, it is difficult to generalize. No serious long-term impacts are known to have been caused by the Rance tidal power plant, but large developments in the Bay of Fundy would, it has been predicted, perturb the tidal regime, with impacts on New England shorelines.

7. In recent years, commercial acceptance of combined-cycle generation based on combustion turbines has reduced the potential economic and environmental costs of meeting future capacity and energy demands through thermal plants wherever natural gas is available at competitive prices. This has tended to increase the economic biasagainst tidal power.

8. Another development with adverse implications for tidal power is the trend in many countries to adopt market pricing of electric energy and dispense with regulatory pricing. This in almost every case entails

competition in the generation function. Under such conditions, competitors will be under strong compulsion to choose plant types having the shortest construction times and the lowest unit capital costs.

9. Such factors render construction of new tidal generation capacity unlikely during the near future, unless strong incentives such as emission caps or carbon taxes are imposed.

Geothermal Development

1. Geothermal heat pumps, or ground-source heat pumps, for heating and cooling buildings are a rapidly growing example of a geothermal direct use application. The technology has developed almost without publicity in recent years to become a significant new factor in the supply equation. This is an electrically-based technology that allows high efficiency, reversible, water-source heat pumps to be installed in

buildings in most geographical and geological locations (worldwide). The combination of increasing levels of electrical generation efficiency, with the  impressive energy  amplification of geothermal heat pumps means that space heating can be delivered with effective efficiencies that  exceed100%. The "additional" energy is supplied from the ground. In addition these systems also offer highly efficient cooling. The types of buildings that are using ground-source heating and cooling in this manner range from small utility or public housing, through to very large (MW-sized) institutional or commercial buildings. This technology can offer up to 40% reductions in CO2 emissions against competing technologies. If all of the electricity is supplied from non-fossil 54sources, there are no CO2 emissions associated with heating and cooling a building.

2. Recently, several large-scale arrays have been installed to feed larger systems where suitable supplies of deep geothermal water are not available. In the largest development to date, 4000 units –  each with its

own borehole – have been established on a US Army base in Louisiana to provide heating and cooling.

The concept was developed independently in the US and Europe and, although Sweden and Switzerland have installed many thousands of units to provide winter heating in houses, the pace of installation in

the USA and Canada during the last fifteen years  has overtaken the European rate. There are now believed to be well over a quarter of a million installations in place in North America.

3. While the main activity is currently in the USA, there are a growing number of installations in Canada, Sweden, Switzerland, Austria and Germany. Smaller numbers are being installed in other European countries, and in Australia. The Geothermal Heat Pump Consortium currently has over 750 institutional, corporate and commercial members, and 40 international members from countries including Australia, Canada, China, Croatia, Finland, Germany, India, Japan, the Netherlands, Poland, Russia, Sweden, Turkey, and the UK.

4. Ground-source heat pumps are perhaps the first indication of the seventh age of geothermal technology, breaking the final barrier of geographical availability.To sum up: geothermal technology offers many benefits - clean, indigenous, firm energy - but suffers from economic uncertainties and

geographical limitations. These problems are being actively addressed and future prospects seem bright.

Wind Energy

1. Wind turbines are now a relatively common sight across Europe, with countries such as Denmark, the Netherlands, Germany, UK, Spain and latterly France, all investing in wind farms. Offshore wind

development, although far less advanced, is the greatest prize in this field. However, relative costs of offshore compared to  onshore are higher.

2. This project is aimed to demonstrate the economic as well as technical viability of offshore wind energy. The former was achieved through the innovative use of a floating jack-upbarge which reduced

the time and costs of installation. The latter was achieved mainly through the incorporation of new electronic control systems which improved the compatibility with the grid network, and reduced the need

for expensive grid strengthening measures.

3. Five turbines were installed, about 4 km off the coast of Gotland. Each turbine is rated at 500 kW. The average annual output is some 8 GWh/y, from mean wind speeds of 8 m/s. Rock-socketed steel

mono-pile foundations, to water depths of 5 to 6.5 m were used to secure the turbines. Total construction time was only 35 days. Monitoring of impacts on local flora and fauna, such as the seal population, is also

being carried out.

4. Wind energy developments have, in the past, been concentrated in areas of the world which offer higher than average wind speeds. Often, this means that developments take place in remote and/or sensitive 57areas. A technology which can increase the economic attractiveness of

utilizing sites with lower wind speeds would be invaluable (бесценный). This project will design, manufacture, install, test and measure the impact of two 1 MW turbines which have been specially

adapted for use in low wind speed areas. The aim is to increase power production by up to 22%, compared to a standard turbine, mainly through the technological adaptations which allow for an enhanced rotor diameter, with a swept area of 2,830 m, and an increase in tower height from 50 to 70 m. The new turbine is installed at a site in Central Sweden.