The concept of battery electric vehicles is to charge batteries on board vehicles for propulsion using the electric grid.

& & & & Battery electric cars are becoming more and more attractive with the advancement of new battery technology (Lithium Ion) that have higher power and energy density (i.e. greater possible acceleration and more range with less batteries) and higher oil prices.

BEVs include automobiles, light trucks, and neighborhood electric vehicles.

Advantages

#No air pollutants are emitted directly by the vehicle. This potentially reduce urban pollution, and the vehicles may be used indoors. This does not take into account additional pollutants that are emitted if any fossil fuel power plant is used to create the electricity, though a centralized pollution source can be dealt with more easily.

#The engine is silent compared to all sorts of internal combustion engines (and road traffic is the most common source of noise pollution in at least the rich coutries) – even if they don’t reduce tire noise.

#No noise or air pollution because of idle running.

#Gasoline is indirectly replaced by whatever is being used to generate domestic electricity, reducing dependence on foreign commodities (some countries, like Japan, have virtualle no own petroleum resources). The electrical energy stored within the battery can be generated by any source, including renewable (hydroelectric, wind, etc.), nuclear, natural gas, coal and petroleum.

#The efficiency is higher than for internal combustion engines (the efficiency of small-scale ICEs don’t exceed 43 %) – especially if the vehicles do utilize e.g. hydroelectric power, but also compared to electricity from coal power plants.

Disadvantages

#The batteries, at least today,are very heavy (compared to their reach), so the vehicles are heavier than gasoline or diesel ones, trolleybuses etc., and don’t go as far.

#The batteries, at least today, are very expensive.

#Battery cars are marketed as ‘’environmental friendly’’ or ‘’green’’ but aren’t so if the substitute is bicycling or light rail.

#Battery cars may need as much space and make as much traffic jams as other cars at the same size. Some are tandem which makes them narrow.

#Battery cars are as unsafe as their gasoline, diesel or biofuel driven siblings at same speed.

#Production of battery cars and roads are as polluting and requires as muchas if not more resourses as ditto for any other cars at the same size.

Electric bus

Chattanooga, Tennessee operates nine zero-fare electric buses, which have been in operation since 1992 and have carried 11.3 million passengers and covered a distance of , They were made locally by Advanced Vehicle Systems. Two of these buses were used for the 1996 Atlanta Olympics.

Wrightbus has a new a hybrid-electric driveline for the StreetCar RTV which has been developed in conjunction with the ISE Corporation of California and incorporates Siemens ELFA traction components and a Cummins ISL engine. The chassis is built to Wright Group specifications by Swiss trolleybus specialists Carosserie Hess and is powered by Valence Technology lithium phosphate batteries .

Beginning in the summer of 2000, Hong Kong Airport began operating a 16-passenger Mitsubishi Rosa electric shuttle bus, and in the fall of 2000, New York City began testing a 66-passenger battery-powered school bus, an all electric version of the Blue-Bird TC2000. A similar bus was operated in Napa Valley, California for 14 months ending in April, 2004.

The 2008 Beijing Olympics used a fleet of 50 electric buses, which have a range of with the air conditioning on. They use Lithium-ion batteries, and consume about . The buses were designed by the Beijing Institute of Technology and built by the Jinghua Coach Co. Ltd. The batteries are replaced with fully charged ones at the recharging station to allow 24 hour operation of the buses.

Thunder Sky

Thunder Sky Energy Group of Shenzhen, China (near Hong Kong) builds lithium-ion batteries used in submarines and has four models of electric buses, the ten passenger EV-6700 with a range of , the TS-6100EV and TS-6110EV city buses, and the 43 passenger EV-2008 highway bus, which has a range of . The batteries can be recharged in 1 hour or replaced in 5 minutes. The buses are also to be built in the United States and Finland.

Valence

Valence Technology has entered into a contract with The Tanfield Group Plc to manufacture and supply Lithium Phosphate energy storage systems to power Tanfield’s all-electric commercial delivery vehicles. The Valence battery systems will be installed in vans and trucks produced by Tanfield’s UK-based trading division, Smith Electric Vehicles, the world’s largest manufacturer of electric vans and trucks.

Free Tindo

Tindo is an all-electric bus from Adelaide, Australia. The Tindo (aboriginal word for sun) is made by Designline International in New Zealand and gets its electricity from a solar PV system on Adelaide’s central bus station. Rides are zero-fare as part of Adelaide’s public transport system.

Trucks

Drive Star is a CalCars plan to cut our oil use in half by 2020. U.S. 100 million trucks, vans, and buses now gulp down one third of the oil. About half stay on the road a surprisingly long time: 15 to 35 years. That is long enough for CalCars to merit a makeover. Retrofitting these gas guzzlers will pay off. Mass conversions will cost under $10–$15,000. Retrofitters can partner with energy service companies to finance these costs, backed by federal loan guarantees. Since an electric mile is up to five times cheaper than a petroleum mile, retrofits will cost less to drive right away, benefitting vehicle fleets and individual drivers.

Semi-trailer trucks

The Port of Los Angeles and South Coast Air Quality Management District have demonstrated a short-range heavy-duty all electric truck capable of hauling a fully loaded cargo container. The current design is capable of pulling a cargo container at speeds up to and has a range of between . It uses , compared to for the hostler semi tractors it replaces.

Electric tractors

Electric tractors have been built since the 1990s.

Milk float

In early 2009, Phoenix Motorcars will be shipping a test fleet of their all-electric SUT (Sports Utility Truck) to Maui. One of the surviving electric vehicles from the late 1990s is the Chevy S-10 electric pickup truck. Many other vehicles from this era, such as the General Motors EV1 were recalled and destroyed. A newcomer is the Miles Electric Vehicles ZX40ST electric truck now available in the United States. Miles Electric Vehicles is based in Santa Monica, California.

The Big Bike Company Limited, in Gloucestershire, England, is now offering fully electric pick up trucks for sale. Powered by an impressive bank of batteries, these small utility vehicles are able to deliver a payload of approximately 500kgs, and have a range of up to 80 miles. Using a 3 wheel configuration, the rolling and aerodynamic drag is reduced. As a tricycle it can also be driven on a motorcycle licence. They are marketed on the internet, and can be viewed on a temporary web site at www.electrux.net.

Electric cars

Rail =

Locomotives

Electric Rail Trolley

Electrathon

Two wheels =

Electric motorcycles and scooters

Electric bicycles

Adapted from the Wikipedia article Battery electric vehicle, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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Artificial gravity could be created in several ways:

Rotation

Adapted from the Wikipedia article Artificial gravity, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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The method of magnetic surveying=

The Earth’s magnetic field

Magnetic field exists around us. We could not see and feel them, but we can measure them with sensitive instruments, called magnetometers. The Earth’s magnetic field is approximately the same as would be produced by a large bar magnet near earth’s centre oriented with the positive end towards the North Pole and inclined at an angle of 10˚ to the axes of rotation. The field or flux lines of the earth exhibit the usual pattern common to a small magnet. They are vertical on the pole areas and horizontal at the equator areas (Breiner, 1973).

The method of magnetic survey is a passive geophysical technique based on detection of contrasts in the magnetic properties of different materials. In the event that such contrasts do not exist, magnetic prospecting will not be useful. To do magnetic prospecting, one simply measures the Earth’s magnetic field with the small measurement spacing and very close to the surface.

Magnetic anomalies

If the earth were composed of uniform material, the magnetic lines of force would be evenly distributed between the poles and at the small area would be parallel. However, since various materials in the earth have different magnetic susceptibilities due to their composition, the earth’s magnetic lines of force are distorted. The local disturbances of the global magnetic field are called magnetic anomalies (Breiner, 1973).

The anomalies from archaeological objects or naturally occurring rocks and minerals are due chiefly to the presence of the most common magnetic mineral, magnetite, FeO·Fe2O3, or its related minerals. All rocks contain some magnetite from very small fractions of percent to several percent.

Field procedure of magnetic survey

In the initial stage of an investigation, so called ”free search” is carried out to determine the boundaries of the site and some single magnetized objects. At this stage, the operator measures the magnetic field with the help of a Proton or Overhauser magnetometer without using a regular grid. Instead, the operator meanders while measuring at spacings of about 1-1.5m, and marks with small flags the anomalies which seem to be magnetized objects. The method of“free search”is characterized by a high speed (covering typically 3-4 hectares per day).

The method of detail magnetic surveying of archaeological sites is to measure Earth’s magnetic field point by point with a small step (not more than half a meter), close to the surface, and present the measurements on the magnetic map. A coordinate system is set on the site for data collecting. Usually, if there are no obstacles, there are plots 40 m (or 20 m) wide and as long as is necessary to cover the area of the site. Small wooden sticks are put at every meter along two opposite sides of the plot and 40 m-strings (or 20-meters) with meter marks are used between the sticks.

Limitations

Since magnetic method, as other geophysical methods, is indirect by nature, the geophysicist can interpret data in the form of anomalies.

Causes of an anomaly can be suggested or speculated upon, however only excavations can clear verify a character of anomaly.

All geophysical techniques are subjected to noise. Noise is nothing more than false signals in the geophysical measurements. These false signals can be caused by cultural features (buildings, fences, electric power lines, small modern metal objects on a surface of a site, pipelines and natural features (magnetic (granite etc.) bedrock, solar storms, lightning). Sources of noise should be identified prior to any magnetic field work, as geophysical surveys can be planned to eliminate or diminish noise (Breiner, 1973).

Magnetometers

A special pattern of anomalies of the Earth’s magnetic field is created on the archaeological site, detectable with sensitive instruments – magnetometers. For the archaeological prospection we used:

- Two Overhauser gradiometers GSM-19WG of GEM systems Inc. (Canada, Ontario) as main instruments;

- Cesium magnetometers MM-60, M-33 and PKM-1 (Russia, St.Petersburg, “Geologorazvedka”);

- Proton magnetometer MMP-203 (Russia, St.Petersburg,“Geologorazvedka”).

Proton magnetometer of free precession is one of the most common types of portable magnetometers used today for archaeological purposes. It is so named because it utilizes the precession of the spinning protons or nuclei of the hydrogen atom in a sample of hydrocarbon fluid (water, kerosene, alcohol, etc.) to measure the total intensity of the field. The spinning protons, which behave as small magnetic dipoles, are temporarily polarized by application of a uniform strong magnetic field generated by a current in a coil of wire. When the current is removed, the spin of protons causes them to precess around the direction of the ambient or earth’s magnetic field. The precession protons then generate a small signal in the same coil used to polarize them, and the frequency of this signal is precisely proportional to the total intensity of the magnetic field, which can be measured with a precision of 1nT.

The principle upon which it is based is so elegant and simple that it retains its importance despite many decades of the development of other methods (Scollar, Tabagh, Hesse, Herzog, 1990, p.& 450-456). The proton magnetometers have two serious disadvantages. First, erroneous observations may occur where gradients of 300-1000 nT per m are encountered. Also, due to a finite measurement period of time, approximately three seconds, it is quite slow.

Overhauser magnetometer is a variation of the proton-precession magnetometer.

In the proton magnetometer, the polarization is raised by briefly applying a strong field. The Overhauser magnetometer uses free radicals dissolved in a liquid to raise its apparent susceptibility by pumping with a radio frequency. There is a dipole coupling between the proton spins of a liquid and the electron spins of a free radical dissolved in it. Because of the very great increase of polarization (by a factor of up to 4000 or 5000), very small amounts of fluid can be used, which makes the sensors quite small and therefore also highly resistant to gradients. Sensitivities of the order of 0.01 nT are readily obtained in practice (Scollar, Tabagh, Hesse, Herzog, 1990, p.& 450-456).

The main instrument, which we normally use for archaeological prospecting is an Overhauser of GEM systems Inc. (Canada, Ontario). It permits measuring magnetic fields at rates as high as 5 readings per second with a storage capacity of about 32 Mbytes. The sensitivity is from 0.02 nT to 0.015 nT/√Hz with 10,000 nT/m gradient tolerance. The spacing between two sensors in such a gradiometer can be changed and the sensor height can be set at any value. One sensor may be used as a base station to provide a correction for the temporal change in the earth’s field. It could be connected to the console by a long cable (we had a 50-meters long cable).

Cesium magnetometers are highly sensitive type of instrument, their high resolution is about 0.01 nT.

The principle is more complex than that of the proton magnetometer. It operates at the atomic rather than nuclear level. A lamp is used for polarization. When monochromatic light passes through a magnetic field in an appropriate material, there is interaction between the spins of the substance and electromagnetic properties of the light. In contemporary instruments caesium 133 is used. The sensor is glass cell containing metallic caesium. It is heated slightly to vaporize the material. Th e circular polarized pumping light excites electrons in the caesium atoms to a more energetic state. The electrons quickly fall back to their original energy level, but they are continuously re-excited. The magnetic vectors of the atoms precess around the external field, and their moment locks onto one of the rotating components of the field from the coil around a glass cell. This “depumps” the spins and increases the transparency of the cell with a maximum at resonance which occurs at the frequency, proportional to the total magnetic field intensity (Scollar, Tabagh, Hesse, Herzog, 1990, p.& 466-469). The sensitivity of the caesium magnetometers derives from its high precession frequencies, which is important for recording small signals. Another advantage of caesium magnetometer – high gradient tolerance makes it useful in measuring of strongly magnetized archaeological objects in a very shallow depth.

Fluxgate gradiometer. The sensor of it consists of two similar parallel strips of an alloy of high magnetic permeability called Mumetal.

They are driven in and out of magnetic saturation by the solenoid effect of an alternating “drive current” in the coils wound round them. Every time they come out of saturation, an external field can enter them, causing an electrical pulse in the detector coil proportional to the field strength. The drive coils of the two strips are switched in opposite directions – so that the drive current has no net magnetic effect (Scollar, Tabagh, Hesse, Herzog, 1990, p.& 456-466).

The Geoscan fluxgate instruments have a noise level of about 0.1 nT, that makes surveys in areas of weak magnetic contrasts readily achievable. There are additional advantages of compactness and relative cheapness. Therefore, fluxgate gradiometer with its closely-spaced direction-responsive detectors has become “the workhorse – and the racehorse” – of the British archaeological prospecting (Clark, 1996, p.& 69)

The use of magnetic prospecting in Denmark

A considerable part of our work is connected to the investigations of archaeological sites in Denmark. Magnetic methods were used in Danish archaeology in two different ways: first, for archaeomagnetic dating, and second for magnetic surveying. The first magnetic survey in Denmark was carried out in 1965 by Olfert Voss and Niels Abrahamsen on the Roman Age iron-smelting site Drengsted in Southern Jutland, which immediately showed the effectiveness of this method for searching for slagblocks (Abrahamsen, 1965).

Other archaeological feature which creates strong anomalies and therefore are prospective objects for magnetic survey, are pottery kilns. Several of them were investigated with magnetometers in the filed and were also archaeomagnetically dated (Abrahamsen et al., 1982; Abrahamsen et al., 1991). Good results were obtained by geomagnetic field measurements over a reconstructed Bidstrup brick kiln (Hansen et al., 1980). Many important investigations, which could clear up the nature of magnetism in diff erent kinds of archaeological material along with age determinations, have been carried out at the Geophysical laboratory of Aarhus University by Niels Abrahamsen, Niels Breiner and their colleagues and students. (Abrahamsen & Breiner, 1990, 1993; Abrahamsen, et al., 1998). Since 1992, systematic magnetic surveys have been carried out in south-west Jutland by the authors, mostly on Roman Age iron-smelting production centers. Several promising magnetic surveys have also been done on other archaeological sites.

For the conditions in Denmark, especially in south-west Jutland, where almost all the land is cultivated, the only parts of archaeological sites still preserved are those which were underground in ancient times: all kinds of pits (garbage pits, pit-houses, postholes), wells, ditches, and also slag-blocks, etc. The usefulness of magnetic surveys on archaeological sites in Denmark is mostly due to the combination of two conditions. First, that the contrast of the magnetic properties of the archaeological material and the surrounding matter (almost nonmagnetic sand) is large enough (see Table below), and, second, that the noise level is rather low.

Adapted from the Wikipedia article Magnetic Surveying in Archaeology (book), under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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Microcontroller

”Main article:” Microcontroller.

Microcontroller performs tasks, processes data and controls the functionality of other components in the sensor node. Other alternatives that can be used as a controller are: General purpose desktop microprocessor, Digital signal processors, Field Programmable Gate Array and Application-specific integrated circuit. Microcontrollers are the most suitable choice for a sensor node. Each of the four choices has their own advantages and disadvantages. A microcontroller is often the best choice for embedded systems because of its flexibility to connect to other devices, ease of programming, and low power consumption. Power can be conserved by programming these devices to go into a sleep state with only part of the controller active. In a general purpose microprocessor the power consumption is more than the microcontroller; therefore it is not a suitable choice for sensor node. Digital Signal Processors are appropriate for broadband wireless communication. But in Wireless Sensor Networks, the wireless communication should be modest i.e., simpler, easier to process modulation and signal processing tasks of actual sensing of data is less complicated. Therefore the advantages of DSP’s are not of much importance to wireless sensor nodes. Field Programmable Gate Arrays can be reprogrammed and reconfigured according to requirements, but this takes more time and energy than desired. Application Specific Integrated Circuits are specialized processors designed for a given application. ASIC’s provide the functionality in the form of hardware, but microcontrollers provide it through software.

Transceiver

”Main Article:” Transceiver.

Sensor nodes make use of ISM band which gives free radio, spectrum allocation and global availability. The various choices of wireless transmission media are Radio frequency, Optical communication (Laser) and Infrared. Lasers require less energy, but need line-of-sight for communication and are also sensitive to atmospheric conditions. Infrared like laser, needs no antenna but is limited in its broadcasting capacity. Radio Frequency (RF) based communication is the most relevant that fits to most of the WSN applications. WSN’s tend to use license free communication frequencies: 173, 433, 868, and 915 MHz, and 2.4 GHz. The functionality of both transmitter and receiver are combined into a single device know as transceivers are used in sensor nodes. Transceivers often lack unique identifiers. The operational states are Transmit, Receive, Idle and Sleep. Current generation transceivers have built-in state machines that perform some operations automatically.

Most transceivers operating in Idle mode have a power consumption almost equal to the power consumed in Receive mode . Thus it is better to completely shutdown the transceiver rather than leave it in the Idle mode when it is not Transmitting or Receiving. A significant amount of power is consumed when switching from Sleep mode to Transmit mode to transmit a packet.

External Memory

From an energy perspective, the most relevant kinds of memory are on-chip memory of a microcontroller and Flash memory – off-chip RAM is rarely if ever used. Flash memories are used due to its cost and storage capacity. Memory requirements are very much application dependent. Two categories of memory based on the purpose of storage a) User memory used for storing application related or personal data. b) Program memory used for programming the device. This memory also contains identification data of the device if any.

Power Source

Power consumption in the sensor node is for the Sensing, Communication and Data Processing. More energy is required for data communication in sensor node. Energy expenditure is less for sensing and data processing. The energy cost of transmitting 1 Kb a distance of 100 m is approximately the same as that for the executing 3 million instructions by 100 million instructions per second/W processor. Power is stored either in batteries or capacitors. Batteries, both rechargeable and non-rechargeable, are the main source of power supply for sensor nodes. They are also classified according to electrochemical material used for electrode such as NiCd (nickel-cadmium), NiZn (nickel-zinc), Nimh (nickel metal hydride), and Lithium-Ion.

Current sensors are developed which are able to renew their energy from solar, temperature, or vibration. Two major power saving policies used are Dynamic Power Management (DPM) and Dynamic Voltage Scaling (DVS). DPM takes care of shutting down parts of sensor node which are not currently used or active. DVS scheme varies the power levels depending on the non-deterministic workload. By varying the voltage along with the frequency, it is possible to obtain quadratic reduction in power consumption.

Sensors

”Main article:” Sensors.

Sensors are hardware devices that produce measurable response to a change in a physical condition like temperature and pressure. Sensors sense or measure physical data of the area to be monitored. The continual analog signal sensed by the sensors is digitized by an Analog-to-digital converter and sent to controllers for further processing. Characteristics and requirements of Sensor node should be small size, consume extremely low energy, operate in high volumetric densities, be autonomous and operate unattended, and be adaptive to the environment. As wireless sensor nodes are typically very small electronic devices, they can only be equipped with a limited power source of less than 0.5-2 Ah and 1.2-3.7 V.

Sensors are classified into three categories.

*Passive, Omni Directional Sensors: Passive sensors sense the data without actually manipulating the environment by active probing. They are self powered i.e. energy is needed only to amplify their analog signal. There is no notion of “direction” involved in these measurements.

*Passive, narrow-beam sensors: These sensors are passive but they have well-defined notion of direction of measurement. Typical example is ‘camera’.

*Active Sensors: These group of sensors actively probe the environment, for example, a sonar or radar sensor or some type of seismic sensor, which generate shock waves by small explosions.

The overall theoretical work on WSN’s considers Passive, Omni directional sensors. Each sensor node has a certain area of coverage for which it can reliably and accurately report the particular quantity that it is observing. Several sources of power consumption in sensors are a) Signal sampling and conversion of physical signals to electrical ones, b) signal conditioning, and c) analog-to-digital conversion. Spatial density of sensor nodes in the field may be as high as 20 nodes/ m3 .

Adapted from the Wikipedia article Sensor node, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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The book is divided into ten chapters which deal with a different technology (although there was some contention, as raised by the author, with the ‘Soils and Forests’ Chapter). Typically every chapter covers the advantages, disadvantages and viability (economically and technologically) of the technology.

With regards to wind power, Goodall argues that since the technology to utilise wind efficiently exists current and that there are sufficient sites to supply the world’s energy demands (’72 terrawatts – about thirty times the world’s electricity requirement’), the main obstacle is reliability.

Efficiency of current photovoltaic panels (typically 10%) and the cost (of silicon) are identified as the only remaining problems in rolling out large solar powerplants in places such as North Africa, the Sahara Desert and California, Goodall concludes in the solar energy chapter.

Goodall identifies the Pentland Firth as one of twenty global sites that promise ‘enormous potential’ with tidal-stream power. Cited as the main reason for continued failure to harness the Ocean’s ‘enormous untapped potential’ is a lack of funding, driven by competition in R&D and a lack of interest; although Goodall is optimistic and admits there have been improvements.

Efficient fuel cells applied to domestic homes, the author suggests, may be capable of simultaneously providing hot water, heating and profiting the owner with exports to the local grid. Also discussed are district heating plants, which are widespread in Denmark, able to provide heat to towns and produce electricity.

The Introduction explains how the author came to write about the subject. A section called ‘Putting it all Together’ looks at if the aforementioned ten technologies have the combined potential to ‘save the planet’. Finally the Epilogue reveals the reasoning behind why some technologies (e.g. nuclear energy) are not included and may not work.

Adapted from the Wikipedia article Ten Technologies to Fix Energy and Climate, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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Reflective insulation and radiant barriers reduce the radiation of heat to or from the surface of a material. Radiant barriers will reflect radiant energy. A radiant barrier by itself will not affect heat conducted through the material by direct contact or heat transferred by moist air rising or covection. For this reason, trying to associate R-values with radiant barriers is difficult and inappropriate. The R-value test measures heat transfer through the material, not to or from its surface. There is no standard test designed to measure the reflection of radiated heat energy alone. Radiated heat is a significant means of heat transfer; the sun’s heat arrives by radiating through space and not by conduction or convection. At night the absence of heat (i.e. cold) is the exact same phenomenon, with the heat radiating described mathematically as the linear opposite. Radiant barriers prevent radiant heat transfer equally in both directions. However, heat flow to and from surfaces also occurs via convection, which in some geometries is different in different directions.

Reflective aluminum foil is the most common material used as a radiant barrier. It has no significant mass to absorb and retain heat. It also has very low emittance values “E-values” (typically 0.03 compared to 0.90 for most bulk insulation) which significantly reduces heat transfer by radiation.

Types of radiant barriers

* Foil or foil laminates.

* Foil-faced polyurethane or foil-faced polyisocyanurate panels.

* Foil-faced polystyrene. This laminated, high density EPS is more flexible than rigid panels, works as a vapor barrier, and works as a thermal break. Uses include the underside of roof sheathing, ceilings, and on walls. For best results, this should not be used as a cavity fill type insulation.

* Foil-backed bubble pack. This is thin, more flexible than rigid panels, works as a vapor barrier, and resembles plastic bubble wrap with aluminum foil on both sides. Often used on cold pipes, cold ducts, and the underside of roof sheathing.

* Light-colored roof shingles and reflective paint. Often called cool roofs, these help to keep attics cooler in the summer and in hot climates. To maximize radiative cooling at night, they are often chosen to have high thermal emissivity, whereas their low emissivity for the solar spectrum reflects heat during the day.

* Metal roofs; e.g., aluminum or copper.

Radiant barriers can function as a vapor barriers and serve both purposes with one product.

Materials with one shiny side (such as foil-faced polystyrene) must be positioned with the shiny side facing an air space to be effective. An aluminum foil radiant barrier can be placed either way – the shiny side is created by the rolling mill during the manufacturing process and does not affect the reflectivity of the foil material. As radiant barriers work by reflecting infra-red energy, the aluminum foil would work just the same if both sides were dull.

Types of reflective insulation

Reflective insulation is commonly made of either aluminum foil attached to some sort of backing material or two layers of foil with foam or plastic bubbles in between creating an airspace to reduce convective heat transfer also. The aluminum foil component in reflective insulation will reduce radiant heat transfer by up to 97%. As reflective insulation incorporates an airspace to reduce convective heat flow, it carries a measurable R-Value.

Advantages

* Very effective in warmer climates

* No change thermal performance over time due to compaction, disintegration or moisture absorption

* Thin sheets takes up less room than bulk insulation

* Can act as a vapor barrier

* Non-toxic/non-carcinogenic

* Will not mold or mildew

* Radon retarder, will limit radon penetration through the floor

Disadvantages

* Must be combined with other types of insulation in very cold climates

* May result in an electrical safety hazard where the foil comes into contact with faulty electrical wiring

Adapted from the Wikipedia article Building insulation materials, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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Tankless water heaters, also called instantaneous, continuous flow, inline, flash, on-demand or instant-on water heaters, are also available and gaining in popularity. These water heaters instantly heat water as it flows through the device, and do not retain any water internally except for what is in the heat exchanger coil.

Tankless heaters are often installed throughout a household at more than one point-of-use (POU), far from the central water heater, or larger models may still be used to provide all the hot water requirements for an entire house. The main advantages of tankless water heaters are a continuous flow of hot water and energy savings (as compared to a limited flow of continuously heating hot water from conventional tank water heaters).

How tankless water heaters work

When there is a demand for hot water (e.g. a hot water tap is opened for a sink, shower, tub, or washing machine) the tankless water heater’s water flow turbine senses the flow and starts the heating process. The water flow turbine sends a signal to the control board which looks at multiple factors: incoming water temperature, desired water temperature as set on the temperature controller, and the calculated difference between the two temperatures. Depending on the calculated incoming and desired water temperatures, the gas or electric flow into the burner assembly is modulated and the electronic ignition sequence begins. Water is heated to the desired temperature as it circulates through the copper heat exchanger providing continuous hot water. When the hot water tap is turned off, the tankless water heater shuts down and is placed in a standby mode pending the next call for hot water.

Combination boilers

Combination or combi boilers, combine the central heating (CH) with the domestic hot water (DHW) in one box. They are not merely infinitely continuous water heaters having the ability to heat a hydronic heating system in a large house. When DHW is run off, the combi stops pumping water to the hydronic circuit and diverts all the boilers power to instantly heating DHW. Some combis have small internal water storage vessels combining the energy of the stored water and the gas or oil burner to give faster DHW at the taps or increase the DHW flowrate.

Combi boilers are rated by the DHW flowrate. The kW ratings for domestic units are 24& kW to 54& kW, giving approximate flowrates of per minute. There are larger commercial units available. The high flowrate models will simultaneously supply two showers.

A further advantage is that more than one combi unit may be used to supply separate heating zones, giving greater time and temperature control, and multiple bathrooms. An example is one combi supplying the downstairs heating system and another the upstairs. One unit may supply one bathroom and one another. Having two units gives backup in case one combi is down.

Great savings are to be had in installation costs as water tanks and associated pipes and controls are not required. This also saves space in a home that may be given over to living space.

Combi boilers are highly popular in Europe, where in some countries market share is 70%.

Electric shower head

In certain parts of South America as well as Costa Rica and Puerto Rico, a point of use style water heater commonly referred to as the “electric shower head” is used in many residential and some commercial installations. As the name implies, an electric heating element is incorporated into such shower heads to heat the water. However, many of these units are often poorly installed, often with exposed wiring in wet locations.

Various types and their advantages

Point-of-use tankless water heaters are located right where the water is being used, so the water is almost instantly hot, which saves water. They also save even more energy than centrally installed tankless water heaters because no hot water is left in the pipes after the water is shut off. However, point-of-use tankless water heaters are usually used in combination with a central water heater since they are usually limited to under 6 litres/minute (1.5 U.S. gallons/minute), as the expense of buying a heater for every kitchen, laundry room, bathroom, or sink can outweigh the money saved in water and energy bills. In addition, point of use water heaters until recently were almost always electrical, and electricity is often substantially more expensive than natural gas or propane.

Tankless heaters can ideally be somewhat more efficient than storage water heaters. In both kinds of installation (centralized and POU) the absence of a tank saves energy as conventional water heaters have to reheat the water in the tank as it cools off, called standby loss. There is a misconception that the energy lost by a tanked heater stored inside a home merely helps to heat the home. This is true of an electric unit, but for a gas unit some of this wasted energy leaves through the exhaust vent. However, if the building needs to be cooled to maintain normal temperatures this results in a loss in efficiency. With a central water heater of any type, water is wasted waiting for water to heat up because of the cold water in the pipes between the faucet and the water heater. This water waste can be avoided if a recirculating pump is installed, but at the cost of electricity to run the pump and wasted energy to heat the water circulation through the pipes.

Tankless water heaters can be divided into two categories: “full on/full off” and “modulated”. Full on/full off units do not have a variable power output level; the unit is either fully on or completely off. Modulated tankless water heaters base the heat output on the flow of water running through the unit. This is usually done through the use of a flow sensor, modulating gas valve, inlet water temperature sensor and an outlet water temperature sensor-choke valve and means that the occupants should receive the same output temperature of water at differing velocities, usually within a close range of ±2& °C.

The high-efficiency condensing combination boiler provides both space heating and water heating, an increasingly popular choice in UK houses. In fact, combination boilers now account for over half of all the new domestic boilers installed in Britain.

Under current North American conditions, the most cost effective configuration from an operating viewpoint is usually to use a central tankless water heater for most of the house, and install a point of use tankless water heater at any distant faucets or bathrooms. However, this may vary according to how much electricity, gas and water costs in the area, the layout of the house, and how much hot water is used. Only electric tankless water heaters were available at first and they are still used for almost all point of use heaters, but natural gas and propane heaters are now common. When consumers are considering a whole house gas tankless unit, they are advised to look at how the unit functions when raising the water temperature by about 42& °C (75–77& °F). Thus, if they live in a cold weather climate, they are advised to look at the unit’s capacity with 3-10& °C (38–50& °F) inlet water temperatures, and find a size that produces approximately 15 litres/minute (4 gpm) even in winter if they have a typical-sized house and desire what is called a 2-appliance heater. This same unit may produce 25-30 litres/minute (6.3–6.9 gpm) in summer with higher inlet temperatures, but there is greater interest in year round production and usability.

Advantages

There are certain advantages to tankless water heaters :

* Long term energy savings: Although a tankless water heater might cost more initially it may result in both energy and cost savings in the long term. As water is heated only when it is needed, there is no storage of hot water. With a tank, water is kept warm all day even if it never gets used and heat loss through the tank walls will result in a continual energy drain. Even in homes or buildings with a high demand for hot water, a tankless water heater may provide some level of savings. In a typical home these savings are quite substantial. If instant hot water at the taps at limited hours is a priority, a recirculation system similar to those in the tank-type systems can be accommodated by using an aquastat and timer in order to decrease the added heat loss from the recirculation system. It has to be said though that if the storage tank is highly-insulated—a few tanks are available with excellent levels such as 100& mm or more polyurethane foam—the savings become minimal. For one consumer-grade electric storage water heater, the surface temperature was less than 1& °C higher than the air temperature.

* Unlimited hot water: As water is heated while passing through the system an unlimited supply of hot water is available with a tankless water heater. Although flow rate will determine the amount of hot water that can be generated at one time it can be generated indefinitely. However, this can also be a disadvantage as running out of hot water self-limits use while a tankless heater has no such limit.

* Less physical space: Most tankless water heaters can be mounted on a wall or even internally in a building’s structure. This means less physical space has to be dedicated to heating water. Even systems that can’t be mounted on walls take up less space than a tank-type water heater.

* Reduced risk of water damage: No stored water means there is no risk of water damage from a tank failure or rupture, although the risk of water damage from a pipe or fitting failure remains. Improper piping in either the hot or cold water lines to the tankless water heater can result in water damage though.

* Temperature compensation A temperature compensating valve tends to eliminate the issue where the temperature and pressure from tankless heaters decrease during continuous use. Most new generation tankless water heaters, like the Takagi TK3, TK3 PRO, TM32, and the TM50 stabilize water pressure and temperature by a bypass valve and a mixing valve which is incorporated in the unit. Modern Tankless are not inversely proportional, because they will regulate the amount of water that is created and discharged, therefore stabilizing water temperature by utilizing a flow control valve. Flow speed is not the issue, but delta T is the important issue to address. The wider the temperature rise, the less flow you receive from the unit. The smaller the temperature rise, the more flow you receive. The flow control valve in conjunction with thermistors, maintains a stable temperature throughout the use of the unit.

Disadvantages

Tankless heaters also have several disadvantages:

* Start-up delay: There is a longer wait to obtain hot water. A tankless water heater only heats water upon demand, which is one of its chief advantages, so all idle water in the piping starts at room temperature. Thus there is a more apparent “flow delay” for hot water to reach a distant faucet (in non-point-of-use systems). Many models sold in the UK have introduced a small heat store within the combi. to address this issue. This “keep hot” facility considerably improves the standard of hot water service, which some people otherwise find unacceptably poor with a combi., but it uses considerably more fuel especially in summer.

* Intermittent-use: There is a short delay (1–3 seconds) between the time when the water begins flowing and when the heater’s flow detector activates the heating elements or gas burner. In the case of continuous-use applications (showers, baths, washing machine) this is not an issue. However, for intermittent-use applications (for example when a hot water faucet is turned on and off repeatedly at a sink) this can result in periods of hot water, followed by some small amount of cold water as the heater activates, followed quickly by hot water again. The period between hot/cold/hot is the amount of water which has flowed though the heater before becoming active. This cold section of water takes some amount of time to reach the faucet and is dependent on the length of piping.

* Installation cost: Installing a tankless system comes at an increased cost, particularly in retrofit applications. They tend to be particularly expensive in areas such as the US where they are not dominant, compared to the established tank design. If a storage water heater is being replaced with a tankless one, the size of the electrical wiring or gas pipeline may have to be increased to handle the load and the existing vent pipe may have to be replaced, possibly adding expense to the retrofit installation. Many tankless units have fully modulating gas valves that can range from as low as 10,000 to over 1,000,000 BTUs. For electrical installations (non-gas), AWG 10 or 8 wire, corresponding to 10 or 6& mm², is required for most POU (point of use) heaters at North American voltages. Larger whole house electric units may require up to AWG 2 wire. In gas appliances, both pressure and volume requirements must be met for optimum operation.

* Heat source flexibility Tankless heaters are ”sometimes” limited to a choice between CO2 problematic energy sources: gas and electricity. This ”sometimes” makes it difficult to include other heat sources, ”sometimes” including certain renewable energy options. One exception is solar water heating, which can be used in conjuncion with tankless water heaters. However, tank-type systems have a much wider choice of heat sources available, such as district heating, central heating, geothermal heating, micro CHP and ground-coupled heat exchangers.

* Recirculation systems: Since a tankless water heater is inactive when hot water is not being used, they are incompatible with passive (convection-based) hot water recirculation systems. They may be incompatible with active hot water recirculation systems and will certainly use more energy to constantly heat water within the piping, defeating one of a tankless water heater’s primary advantages. On-demand recirculating pumps are often used to minimize hot water wait times from tankless water heaters and save water being wasted down the drain. On-demand recirculating pumps are activated by push-button or other sensor. A water contacting temperature probe installed at the hot water usage point signals the pump to stop. Single-cycle pumping events only occur when hot water is needed thereby preventing the energy waste associated with constantly heating water within piping.

* Achieving cooler temperatures: Tankless water heaters often have minimum flow requirements before the heater is activated, and this can result in a gap between the cold water temperature, and the coolest warm water temperature that can be achieved with a hot and cold water mix.

* Maintaining constant shower temperature: Similarly, unlike with a tank heater, the hot water temperature from a non-modulated tankless heater is inversely proportional to the rate of the water flow—the faster the flow, the less time the water spends in the heating element being heated. Mixing hot and cold water to the “right” temperature from a single-lever faucet (say, when taking a shower) takes some practice. Also, when adjusting the mixture in mid-shower, the change in temperature will initially react as a tanked heater does, but this also will change the flow rate of hot water. Therefore some finite time later the temperature will change again very slightly and require readjustment. This is typically not noticeable in non-shower applications.

* Operation with low supply pressure: Tankless systems are reliant on the water pressure that is delivered to the property. In other words, if a tankless system is used to deliver water to a shower or water faucet, the pressure is the same as the pressure delivered to the property and cannot be increased, whereas in tanked systems the tanks can be positioned above the water outlets (in the loft/attic space for example) so the force of gravity can assist in delivering the water, and pumps can be added into the system to increase pressure. Power showers, for example, cannot be used with tankless systems because the tankless systems cannot deliver the hot water at a fast enough flow rate required by the pump.

* Time-of-use metering and peak electrical loads: Tankless electric heaters, if installed in a large percentage of homes within an area, can create demand management problems for electrical utilities. Because these are high-amperage devices, and hot water use tends to peak at certain times of the day, their use can cause short spikes in electricity demand, including during the daily peak electrical load periods, which increases utility operating costs. For households using time-of-use metering (where electricity costs more during peak periods such as daytime, and is cheaper at night), a tankless electric heater may actually increase operating costs if the hot water is used during peak times. Instantaneous-type heaters are also problematic if they are connected to district heating systems, as they raise peak demands, and most utilities prefer all buildings to have hot water storage.

Adapted from the Wikipedia article Water heating, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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The continued reliance on fossil fuels in the United States is having drastic consequences to the environment, and continued reliance on foreign oil threatens national security and economic well-being. Alternative energy technologies have a number of strengths and weaknesses. This book examines the various technologies from the standpoints of economics, environmental impact, domestic resource potential, public acceptability, and reliability to find a path forward.

The transportation alternatives to oil that are examined in the book include biofuels, hydrogen, and electric vehicles. The author concludes that only electric vehicles will achieve drastically reduced emissions in an efficient manner, and plug-in hybrids will be the first step that will lead to economical competitiveness.

Increased reliance on electricity will make it that much more important to develop clean power plants. Renewable energy will be part of the solution, but high costs are poor reliability continue to make renewable sources challenging to develop cost-effectively. The author concludes that wind energy has the greatest potential for near-term expansion. However, smaller-scale use of solar, geothermal, biomass, and ocean sources along with current hydroelectric sources could add up to make a significant contribution. The advantages and disadvantages of each renewable energy option are examined.

Nuclear energy is also supported by the author as the only way to produce large amounts of emission-free power. The author pays close attention to the safety of nuclear energy and provides a unique comparison of the safety of energy generation from a number of sources.

Fossil energy is then examined with a focus on the development of carbon sequestration technologies. Coal power plants will full carbon sequestration are shown to be competitive with existing natural gas plants due to the currently high natural gas prices. With abundant coal resources in the United States, the author concludes that coal will continue to be an important part of U.S. energy generation for many decades.

== Further Resources

Links

“Annual Energy Outlook 2008,” DOE/EIA-0383(2008) Energy Information Administration (June, 2008).

“Climate Change 2007,” Intergovernmental Panel on Climate Change (April, 2007).

T.W. Patzek, “Thermodynamics of the Corn-Ethanol Biofuel Cycle,” University of California-Berkeley (July 22, 2006).

Further Reading

Adapted from the Wikipedia article The Energy Construct, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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The main components of the drive system of any electrically powered boat are similar in all cases, and similar to the options available for any electric vehicle.

Charger

Electric energy has to be obtained for the battery bank from some source.

* Mains charger allows the boat to be charged from shore-side power when available. Shore-based power stations are subject to much stricter environmental controls than the average marine diesel or outboard motor. By purchasing green electricity it is possible to operate electric boats using sustainable or renewable energy.

* Solar panels can be built into the boat in reasonable areas in the deck, cabin roof or as awnings. Some solar panels, or photovoltaic arrays, can be flexible enough to fit to slightly curved surfaces and can be ordered in unusual shapes and sizes. Nonetheless, the heavier, rigid mono-crystalline types are more efficient in terms of energy output per square meter. The efficiency of solar panels rapidly decreases when they are not pointed directly at the sun, so some way of tilting the arrays while under way is very advantageous.

* Towed generators are common on long-distance cruising yachts and can generate a lot of power when travelling under sail. If an electric boat has sails as well, and will be used in deep water (deeper than about 15 m or 50 ft), then a towed generator can help build up battery charge while sailing (there is no point in trailing such a generator while under electric propulsion as the extra drag from the generator would waste more electricity than it generates). Some electric power systems use the free-wheeling drive propeller to generate charge through the drive motor when sailing, but this system, including the design of the propeller and any gearing, cannot be optimised for both functions. It may be better locked off or feathered while the towed generator’s more efficient turbine gathers energy.

* Wind turbines are common on cruising yachts and can be very well suited to electric boats. There are safety considerations regarding the spinning blades, especially in a strong wind. It is important that the boat is big enough that the turbine can be mounted out of the way of all passengers and crew under all circumstances, including when alongside and when coming alongside a dock, a bank or a pier. It is also important that the boat is big enough and stable enough that the ”top hamper” created by the turbine on its pole or mast does not compromise its stability in a strong wind or gale. Large enough wind generators could produce a completely wind-powered electric boat. No such boats are yet known although a few ”mechanical” wind turbine powered boats exist.

* If the boat has an internal combustion engine anyway, then its alternator will provide significant charge when it is running. Two schemes are in use: the combustion engine and the electric motor both coupled to the drive, or a separate generator with the combustion engine only charging the storage batteries.

In all cases, a charge regulator is needed. This ensures that the batteries are charged at the maximum rate that they safely can stand when the power is available. It also ensures that they are not overcharged when nearing full charge and not overheated when a large charge current becomes available.

Battery bank

There have been significant technical advances in battery technology in recent years, and more are to be expected in the future.

* Lead-acid batteries may still be the most viable option at the moment (2008). Deep-cycle, ‘traction’ batteries are the obvious choice. They are heavy and bulky, but not much more so than the diesel engine, tanks and fittings that they may replace. They need to be securely mounted, low down and centrally situated in the boat. It is essential that they ”cannot” move around under ”any” circumstances. Care must be taken that there is no risk of spilled, strong acid in the event of a capsize as this could be very dangerous. Venting of explosive hydrogen and oxygen gases is also necessary. Typical lead-acid batteries must be kept topped-up with distilled water.

* Valve-regulated lead-acid (VRLA) batteries, usually known as sealed lead-acid, Gel, or AGM batteries, minimize the risk of spillage, and gases are only vented when the batteries are overcharged. These batteries require minimal maintenance, as they cannot and usually do not need to be refilled with water.

* Nickel metal hydride, lithium-ion and other solid-state batteries are becoming available, but are still expensive. These are the kind of batteries currently common in rechargeable hand tools like drills and screwdrivers, but they are relatively new to this environment. They require different charge controllers to those that suit lead-acid types.

* Fuel cells may provide significant advantages in years to come. Today (2010) however they are still expensive and require specialist equipment and knowledge.

The size of the battery bank determines the ”range” of the boat under electric power alone. The speed that the boat is motored at also affects this – a lower speed can make a big difference to the energy required to move a hull. Other factors that affect range include sea-state, windage and any charge that can be reclaimed while under way, for example by solar panels in full sun. A wind tubine in a good following wind will help, and motor-sailing in any wind could do so even more.

Speed controller

To make the boat usable and maneuverable, a simple-to-operate forward/stop/backwards speed controller is needed. This must be efficient—i.e. it must not get hot and waste energy at any speed—and it must be able to stand the full current that could conceivably flow under any full-load condition. One of the most common types of speed controllers uses Pulse-width modulation (PWM). PWM controllers send high frequency pulses of power to the motor(s). As more power is needed the pulses become longer in duration.

Electric motor

A wide variety of electric motor technologies are in use. Traditional field-wound DC motors were and still are used. Today many boats use lightweight permanent magnet DC motors. The advantage of both types is that while the speed can be controlled electronically, this is not a requirement. Some boats use AC motors or permanent magnet brushless motors. The advantages of these are the lack of commutators which can wear out or fail and the often lower currents allowing thinner cables; the disadvantages are the total reliance on the required electronic controllers and the usually high voltages which require a high standard of insulation.

Drive train

Traditional boats use an inboard motor powering a propeller though a propeller shaft complete with bearings and seals. Often a gear reduction is incorporated in order to be able to use a larger more efficient propeller. This can be a traditional gear box, coaxial planetary gears or a transmission with belts or chains. Because of the inevitable loss associated with gearing, many drives eliminate it by using slow high-torque motors. The electric motor can be encapsulated into a pod with the propeller and fixed outside the hull (saildrive) or on an outboard fixture (outboard motor).

Adapted from the Wikipedia article Electric boat, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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As most of the organic solutions are water-free, they can be exposed to air, but all salt based PCM solutions must be encapsulated to prevent water evaporation or uptake. Both types offer certain advantages and disadvantages and if they are correctly applied some of the disadvantages becomes an advantage for certain applications.

They have been used since the late 1800s as a medium for the thermal storage applications. They have been used in such diverse applications as refrigerated transportation for rail and road applications and their physical properties are, therefore, well-known.

Unlike the ice storage system, however, the PCM systems can be used with any conventional water chiller both for a new or alternatively retrofit application. The positive temperature phase change allows centrifugal and absorption chillers as well as the conventional reciprocating and screw chiller systems or even lower ambient conditions utilizing a cooling tower or dry cooler for charging the TES system.

The temperature range offered by the PCM technology provides a new horizon for the building services and refrigeration engineers regarding medium and high temperature energy storage applications. The scope of this thermal energy application is wide ranging of solar heating, hot water, heating rejection, i.e. cooling tower and dry cooler circuitry thermal energy storage applications.

Since PCMs transform between solid-liquid in thermal cycling, encapsulation naturally become the obvious storage choice.

*Encapsulation of PCMs

**Macro-encapsulation: Early development of macro-encapsulation with large volume containment failed due to the poor thermal conductivity of most PCMs. PCMs tend to solidify at the edges of the containers preventing effective heat transfer.

**Micro-encapsulation: Micro-encapsulation on the other hand showed no such problem. It allows the PCMs to be incorporated into construction materials, such as concrete, easily and economically. Micro-encapsulated PCMs also provide a portable heat storage system. By coating a microscopic sized PCM with a protective coating, the particles can be suspended within a continuous phase such as water. This system can be considered a phase change slurry (PCS).

**Molecular-encapsulation is another technology, developed by [http://www.Energain.co.uk Dupont de Nemours] that allows a very high concentration of PCM within a polymer compound. It allows storage capacity up to 515& kJ/m2 for a 5& mm board (103& MJ/m3). Molecular-encapsulation allows drilling and cutting through the material without any PCM leakage.

As phase change materials perform best in small containers, therefore they are usually divided in cells. The cells are shallow to reduce static head – based on the principle of shallow container geometry. The packaging material should conduct heat well; and it should be durable enough to withstand frequent changes in the storage material’s volume as phase changes occur. It should also restrict the passage of water through the walls, so the materials will not dry out (or water-out, if the material is hygroscopic). Packaging must also resist leakage and corrosion. Common packaging materials showing chemical compatibility with room temperature PCMs include stainless steel, polypropylene and polyolefin.

Currently, phase change materials (PCMs) are very widely used in tropical regions in telecom shelters. They protect the high-value equipment in the shelter by keeping the indoor air temperature below the maximum permissible by absorbing heat generated by power-hungry equipment such as a Base Station Subsystem. In case of a power failure to conventional cooling systems, PCMs minimize use of diesel generators, and this can translate into enormous savings across thousands of telecom sites in tropics.

Adapted from the Wikipedia article Phase Change Material, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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