Solar panels and inverters

A single modern silicon solar cell will produce between 2 and 3W of power depending on its size. This will equate to between 3 and 5 A at 0.6 V. In order to provide a usable current and voltage, groups of cells are connected both in series and in parallel. For example, 36 solar cells connected in series will provide an output of about 20 V, suitable for a battery charger designed to recharge a 12 V battery. For grid-connected applications, more cells are necessary. Typical units are designed to...

The cost of tidal power

A tidal power plant is perhaps the most capital-intensive type of power station yet envisaged. It involves building a low-head hydropower scheme in the tidal reaches of an estuary, an environment where construction is, at best, difficult. Construction schedules are long so lengthy up-front loans are required, with a considerable gap between granting of the loan and income from the plant. There is so little experience with this type of project that no useful conclusions can be drawn from...

Stirling engines

Whereas fuel combustion takes place within the cylinders of an internal combustion engine, the heat energy used to drive a Stirling engine is applied outside the cylinders which are completely sealed. The engine was designed by a Scottish Presbyterian minister, Robert Stirling, who received his first patent in 1816. The original engines used air within the cylinders and were called air engines but modern Stirling engines often use helium or hydrogen. A normal Stirling engine has two cylinders,...

Environmental considerations

Piston engine power units generally burn fossil fuels and the environmental considerations that need to be taken into account are exactly the same considerations that affect all coal-, oil- and gas-fired power plants the emissions resulting from fuel combustion. In the case of internal combustion engines the main emissions are nitrogen oxides, carbon monoxide and volatile organic compounds (VOCs). Diesel engines, particularly those burning heavy diesel fuel will also produce particulate matter...

Financial risks

The technology used in the construction of all types of piston engines is mature and the nature of the processes involved are well understood. Improvements are continually made but these are minor in nature. Overall the performance and reliability of a piston engine should fall within well-established boundaries. Performance, both in terms of overall efficiency of operation, reliability and lifetime, should be guaranteed by the manufacturer of a unit. Continuous operation of an engine...

Solar dish collectors

The third type of solar thermal power unit is the solar dish. A solar dish is more accurately a parabolic mirror, at the centre of which is placed a small heat collector and electricity generator. The reflector tracks the sun and focuses its energy onto the collector. Unlike the two preceding technologies which are being developed for utility scale generation, the solar disk will always be a relatively small-scale electricity plant. Those currently being tested have diameters of between 5 and...

CHP technology

Most types of power generation technology are capable of being integrated into a CHP system. There are obvious exceptions such as hydropower, wind power and solar photovoltaic. But solar thermal power plants can produce excess heat and geothermal energy is exploited for CHP applications. Fuel cells are probably one of the best CHP sources while conventional technologies such as steam turbines, gas turbines and piston engine plants can all be easily adapted. The type of heat required in a CHP...

Wind sites

The economics of wind power depend strongly on wind speed. The actual energy contained in the wind varies with the third power of the wind speed. Double the wind speed, and the energy it carries increases eightfold. A 1.5 MW wind turbine at a site with a wind speed of 5.5 m s will generate around 1000 MWh year. At a wind speed of 8.5 m s the output rises to 4500 MWh and at 10.5 m s the annual output will be 8000 MWh. This is close the theoretical limit. Other factors will come into play at very...

Solar power

Solar energy is the most important source of energy available to the earth and its inhabitants. Without it there would be no life. It is the energy source that drives the photosynthesis reaction. As such, it is responsible for all the biomass on the surface of the earth and is the origin of fossil fuels, the products of photosynthesis millions of years ago and now buried beneath the earth's surface. Solar energy creates the world's winds, it evaporates the water which is responsible for rain...

Wind power

Wind is the movement of air in response to pressure differences within the atmosphere. Pressure differences exert a force which cause air masses to move from a region of high pressure to one of low pressure. That movement is wind. Such pressure differences are caused primarily by differential heating effects of the sun on the surface of the earth. Thus wind energy can be considered to be a form of solar energy. Annually, over the earth's land masses, around 1.7 million TWh of energy is...

Piston engines

System Engine Block

There are two primary types of piston engine for power generation, the diesel engine and the spark-ignition gas engine. Of these the diesel engine is the most efficient, reaching close to 50 energy conversion efficiency. The spark-ignition engine burning natural gas can achieve perhaps 42 efficiency but it is much cleaner than the diesel. Indeed it is impossible to obtain authorisation to use a diesel engine for continuous power generation service in some parts of the world. There are four...

Costs

The capital cost of a piston engine power plant generally depends on unit size. Small engines are generally mass produced and cheaper than their larger relatives. However this is often offset by higher installation costs. Thus typical total plant costs for a 100 kW generator unit is 1515 kW while a 5000kW installation costs 919 kW.8 While plants in the 100-5000 kW capacity range are based on standard components, large piston engine power plants generally have a cost structure more like that of...

Binary power plants

Geothermal Binary Costs

Direct- and flash-steam geothermal power plants utilise geothermal fluid with a temperature of between 180 C and 350 C. If the fluid is cooler than this, conventional steam technology will normally prove too inefficient to be economically viable. However energy can still be extracted from the fluid to generate power using a binary power plant. In a binary power plant the geothermal fluid is extracted from the reservoir and immediately passed through a heat exchanger where the heat it contains...

Traditional combustion plants

Schematic Diagram Rotary Kiln

The traditional method of converting waste to energy is by burning it directly in a special combustion chamber and grate, a process which is often called mass burning. The dominant European technologies use this system. These involve specially developed moving grates, often inclined to control the transfer of the waste, and long combustion times to ensure that the waste is completely destroyed. Designs have evolved over 20-30 years and are generally conservative. More recently, fluidised-bed...

Solar photovoltaic technology

The solar cell is made from a thin layer of semiconducting material. The key feature of this semiconductor layer is that it will absorb photons of radiation in the visible region of the electromagnetic spectrum. Each photon of light energy is absorbed by an electron within the solid material. In absorbing the energy, the electron acquires an electrical potential. This potential can be made available as electrical energy, as an electric current. The current is produced at a specific fixed...

Gasification and pyrolysis

Pyrolysis Plant Block Diagram

In recent years a number of companies have attempted to develop new waste-to-energy technologies based on both gasification and pyrolysis. These technologies are derived from the power and the petrochemicals industries. Pyrolysis is a partial combustion process carried out at moderate temperatures in the absence of air, which usually produces a combustible gas and a combustible solid residue. Gasification uses higher temperatures and converts most of the solid material into a combustible gas....

Types of energy storage

Electricity normally has to be used as soon as it has been generated. This is why grid control and electricity dispatching systems are important they have to balance the demand for electricity with the supply. Once one fails to match the other, problems occur. It would seem obvious, given this situation, that some reservoir of saved electricity would be a major boon to grid operation. Yet storing electricity has proved difficult to master. Storing electricity in its dynamic form, amperes and...

Pistonenginebased power plants

Piston engines or reciprocating engines the two terms are often used interchangeably to describe these engines are used throughout the world in applications ranging from lawn mowers to cars, trucks, locomotives, ships, and for power and combined heat and power generation. The number in use is enormous the US alone produces 35 million each year. Engines vary in size from less than 1 kW to 65,000 kW. They can burn a wide range of fuels including natural gas, biogas, LPG, gasoline, diesel,...

Horizontal or vertical

Egg Beater Darrieus Dimensions Shape

As outlined above, the standard wind turbine has a vertical rotor attached to a horizontal shaft. This arrangement imposes certain restrictions on the wind turbine design. With a horizontal shaft, the rotor turns in a vertical plane and must be raised on a tower so that the blades are clear of the ground and of the turbulent layer of air next to it. Gearbox and generator are attached directly to the turbine shaft so these, too, must be placed on the tower, high above ground. This raises the...

Boiler technology

Once Through Supercritical Boiler

A power plant boiler is a device for converting the chemical energy in coal into heat energy and then transferring that heat energy to a fluid, steam. The efficiency of a coal-fired power plant increases as the pressure and temperature of the steam increases. This has led to a demand for higher temperatures and pressures as technology has developed and this has required, in turn, the development of materials with higher performance under increasingly stressful conditions. The most advanced...

Piston engine technology

In its most basic form, the piston engine comprises a cylinder sealed at one end and open at the other end. A disc or piston which fits closely within the cylinder is used to seal the open end and this piston can move backwards and forwards within the cylinder. This it does in response to the expansion and contraction of the gas contained within the cylinder. The outside of the piston is attached via a hinged lever to a crankshaft. Movement of the piston in and out of the cylinder causes the...

Advanced gas turbine design

Block Diagram Tidal Power Generation

A gas turbine aeroengine must remain light and compact so it is not possible to add to it significantly in order to improve its performance. The stationary turbine for power generation does not suffer this restriction. Taking advantage of this greater freedom, engineers have explored a number of strategies that can be applied to stationary gas turbines in order to provide significant performance enhancements. In large steam-turbine-based power plants it is traditional to split the turbine into...

Direct firing

Direct Fired Biomass Plant

The direct firing of biomass involves burning the fuel in an excess of air inside a furnace to generate heat. Aside from heat the primary products of the combustion reaction are carbon dioxide and a small quantity of ash. The heat is absorbed by a boiler placed above the main furnace chamber and water in tubes within the boiler is heated and eventually boiled, producing steam which is used to drive a steam turbine. The simplest type of direct-firing system has a fixed grate onto which the fuel...

Combined cycle power plants

Solar Power Plant Block Diagram

A single gas turbine connected to a generator can generate electricity with a fuel-to-electricity conversion efficiency of perhaps 38 using the best of today's technology. New developments, such as those falling under the auspices of the US DOE's ATS programme aim to push the simple cycle efficiency as high as 41 without cycle adaptation, 43 with adaptation such as recuperation. This is still marginally lower than a modern coal-fired power plant can hope to achieve. Part of the reason for this...

Flashsteam plants

Double Flash Steam Power Plants

Most high-temperature geothermal reservoirs yield a fluid which is a mixture of steam and liquid brine, both under high pressure typically up to 10 atmospheres . The steam content, by weight, is between 10 and 50 . The simplest method to exploit such a resource is to separate the steam from the liquid and use the steam alone to drive a steam turbine. However this throws away much of the available energy, particularly where the proportion of steam in the fluid is small. A more productive...

Open and closed cycle ocean thermal energy conversion

Closed Cycle Otec System

The siting of an OTEC plant, either onshore or offshore, represents one of the key decision for any proposed project. The other key decision is the type of cycle to use. There are two principle options, an open cycle plant or a closed cycle plant. Hybrids of the two have also been proposed. A closed cycle OTEC plant employs a thermodynamic fluid such as ammonia or a refrigerant like freon. This is contained in a completely closed system including the plant turbine. Hot surface seawater is used...

Liquid fuels

Biomass is already used extensively to produce liquid fuels. The most important of these are ethanol, made from the fermentation of grain or sugar cane and biodiesel produced from oil-rich crops such as sunflower and oil-seed rape. Biodiesel is produced extensively in Europe where the total production was over 850,000 tonnes in 2001. Production is now on target to reach 2 of the liquid fuel market by 2005 though 5.75 by 2010 may be harder to attain. Europe also produces ethanol but the largest...

Propeller and Kaplan turbines

The propeller turbine looks like the screw of a ship, but its mode of operation is the reverse of the ship's propulsion unit. In a ship a motor turns the propeller which pushes against the water, forcing the ship to move. In the hydropower plant, by contrast, moving water drives the propeller turbine to generate power. Propeller turbines are most useful for low-head applications such as slow running, lowland rivers. Their efficiency drops off rapidly when the water flow drops below 75 of the...

Shore and nearshore wave converters

Perhaps the most widely tested of shore and near-shore devices is the oscillating water column. If a tube, sealed at one end, is placed so that its open end is just beneath the surface of the sea, as waves pass the tube, the level of water inside the tube will rise and fall, alternately compressing and expanding the air column within the tube. If, instead of a seal, the upper end of this tube is open and houses a device that acts like a wind turbine, then the moving water will cause the air to...

Ocean thermal energy conversion

Otec Plant

OTEC relies on the principle exploited in most forms of electricity generation that a source of heat and a source of cold5 can be used to drive an engine. In the case of OTEC the source of heat is the surface of a tropical or subtropical sea while the source of cold is the deep sea. The possibility of extracting energy from the sea in this way was recognised in the latter half of the nineteenth century and the first practical system was proposed by the French inventor D'Arsonval in 1881....

Protonexchange membrane fuel cell

The PEM fuel cell uses a polymer membrane as its electrolyte. The cell was invented by US company General Electric and tested for US military use in the early 1960s. After development for the US Navy it was adopted by the British Navy in the early 1980s. Since then it has attracted most attention as a possible replacement for the internal combustion engine for automotive applications. However a number of companies are also developing stationary power applications. The membrane which forms the...

Offshore devices

The three types of device discussed above can all be exploited offshore provided they can be moored so that they remain stationary relative to the waves. However most offshore devices try to exploit the wave motion in different ways. The hosepump, developed in Sweden, is based on an elastic tube that changes its internal volume as it is stretched. One end of the tube is sealed and attached to a float while the other end is open and, is connected to a moored plate close to the bottom of the sea....

Integratedgasification combined cycle

Igcc Biomass

The second type of advanced coal-burning plant, the IGCC plant, is based around the gasification of coal. Coal gasification is an old technology. It was widely used to produce town gas for industrial and domestic use in the USA and Europe until natural gas became readily available. Modern gasifiers convert coal into a mixture of hydrogen and carbon monoxide, both of which are combustible. Gasification normally takes place by heating the coal with a mixture of steam and oxygen or, in some cases,...

Gas turbine technology

Block Diagram Gas Turbine Engine

A gas turbine is a machine which harnesses the energy contained within a fluid - either kinetic energy of motion or the potential energy of a gas under pressure - to generate rotary motion. In the case of a gas turbine this fluid is usually, though not necessarily, air. The earliest man-made device for harnessing the energy in moving air was the windmill, described by Hero of Alexandria in the first century ad. The early windmill was a near relative of today's wind turbine. Closer in concept to...

Engine size and speed

The speed at which a piston engine operates will depend on its size. In general small units will operate at high speed and large units at low speed. However since in most situations a piston-engine-based power unit will have to be synchronised to an electricity grid operating at 50 or 60 Hz, the engine speed must be a function of one or other of these rates. Thus a 50 Hz high-speed engine will operate at 1000, 1500 or 3000 rpm while a 60 Hz machine will operate at 1200, 1800 or 3600 rpm....

Biomass gasification

Layout Gas Power Plant

For dedicated biomass combustion to become a major source of electricity, higher-efficiency conversion is required. The best means of achieving this may well prove to be biomass gasification. Gasification involves the partial combustion of biomass in either air or oxygen to produce a gas that contains combustible organic compounds, carbon monoxide and hydrogen. The gasification process is well tested and the product gas will have a calorific value of between one-fifth and one-half that of...

Types of solar cell

Microchips and transistors are universally fabricated using slices cut from perfect crystals of silicon. These crystals are carefully grown under controlled conditions and are expensive to produce. Solar cells can be made with single crystal silicon too. Indeed, cells using this material have provided the best performance of any silicon solar cells, with solar-to-electrical conversion efficiencies of up to 24 . Long-term performance of single crystal silicon cells is good too, but the cost of...