Telecommunication is the transmission of signs, messages, writings and sounds or information of any nature by wire, optical or other electromagnetic systems. Telecommunication occurs when the exchange of information between communication participants includes the use of technology, it is transmitted either electrically over physical media, such as cables, or via electromagnetic radiation. Such transmission paths are divided into communication channels which afford the advantages of multiplexing. Since the Latin term communicatio is considered the social process of information exchange, the term telecommunications is used in its plural form because it involves many different technologies. Early means of communicating over a distance included visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, optical heliographs. Other examples of pre-modern long-distance communication included audio messages such as coded drumbeats, lung-blown horns, loud whistles. 20th- and 21st-century technologies for long-distance communication involve electrical and electromagnetic technologies, such as telegraph and teleprinter, radio, microwave transmission, fiber optics, communications satellites.
A revolution in wireless communication began in the first decade of the 20th century with the pioneering developments in radio communications by Guglielmo Marconi, who won the Nobel Prize in Physics in 1909, other notable pioneering inventors and developers in the field of electrical and electronic telecommunications. These included Charles Wheatstone and Samuel Morse, Alexander Graham Bell, Edwin Armstrong and Lee de Forest, as well as Vladimir K. Zworykin, John Logie Baird and Philo Farnsworth; the word telecommunication is a compound of the Greek prefix tele, meaning distant, far off, or afar, the Latin communicare, meaning to share. Its modern use is adapted from the French, because its written use was recorded in 1904 by the French engineer and novelist Édouard Estaunié. Communication was first used as an English word in the late 14th century, it comes from Old French comunicacion, from Latin communicationem, noun of action from past participle stem of communicare "to share, divide out.
Homing pigeons have been used throughout history by different cultures. Pigeon post had Persian roots, was used by the Romans to aid their military. Frontinus said; the Greeks conveyed the names of the victors at the Olympic Games to various cities using homing pigeons. In the early 19th century, the Dutch government used the system in Sumatra, and in 1849, Paul Julius Reuter started a pigeon service to fly stock prices between Aachen and Brussels, a service that operated for a year until the gap in the telegraph link was closed. In the Middle Ages, chains of beacons were used on hilltops as a means of relaying a signal. Beacon chains suffered the drawback that they could only pass a single bit of information, so the meaning of the message such as "the enemy has been sighted" had to be agreed upon in advance. One notable instance of their use was during the Spanish Armada, when a beacon chain relayed a signal from Plymouth to London. In 1792, Claude Chappe, a French engineer, built the first fixed visual telegraphy system between Lille and Paris.
However semaphore suffered from the need for skilled operators and expensive towers at intervals of ten to thirty kilometres. As a result of competition from the electrical telegraph, the last commercial line was abandoned in 1880. On 25 July 1837 the first commercial electrical telegraph was demonstrated by English inventor Sir William Fothergill Cooke, English scientist Sir Charles Wheatstone. Both inventors viewed their device as "an improvement to the electromagnetic telegraph" not as a new device. Samuel Morse independently developed a version of the electrical telegraph that he unsuccessfully demonstrated on 2 September 1837, his code was an important advance over Wheatstone's signaling method. The first transatlantic telegraph cable was completed on 27 July 1866, allowing transatlantic telecommunication for the first time; the conventional telephone was invented independently by Alexander Bell and Elisha Gray in 1876. Antonio Meucci invented the first device that allowed the electrical transmission of voice over a line in 1849.
However Meucci's device was of little practical value because it relied upon the electrophonic effect and thus required users to place the receiver in their mouth to "hear" what was being said. The first commercial telephone services were set-up in 1878 and 1879 on both sides of the Atlantic in the cities of New Haven and London. Starting in 1894, Italian inventor Guglielmo Marconi began developing a wireless communication using the newly discovered phenomenon of radio waves, showing by 1901 that they could be transmitted across the Atlantic Ocean; this was the start of wireless telegraphy by radio. Voice and music had little early success. World War I accelerated the development of radio for military communications. After the war, commercial radio AM broadcasting began in the 1920s and became an important mass medium for entertainment and news. World War II again accelerated development of radio for the wartime purposes of aircraft and land communication, radio navigation and radar. Development of stereo FM broadcasting of radio
Active fire protection
Active fire protection is an integral part of fire protection. AFP is characterized by items and/or systems, which require a certain amount of motion and response in order to work, contrary to passive fire protection. Fire can be manually or automatically. Manual control includes the use of a standpipe system. Automatic control means can include a fire sprinkler system, a gaseous clean agent, or firefighting foam system. Automatic suppression systems would be found in large commercial kitchens or other high-risk areas. Fire sprinkler systems are installed in all types of buildings and residential, they are located at ceiling level and are connected to a reliable water source, most city water. A typical sprinkler system operates when heat at the site of a fire causes a glass component in the sprinkler head to fail, thereby releasing the water from the sprinkler head; this means that only the sprinkler head at the fire location operates – not all the sprinklers on a floor or in a building. Sprinkler systems help to reduce the growth of a fire, thereby increasing life safety and limiting structural damage.
Fire detection works using heat sensors. These systems are effective tool at alerting people in the immediate vicinity of where the fire is detected but building regulations require an integrated fire detection system; these system not only alerts people throughout the building by triggering the fire alarm but it can summon emergency services. There are two types of systems available -- conventional. Addressable systems monitor the specific location of each device, it means in the event of a fire or other emergency you know where the problem is. This saves precious time and helps the emergency services prevent the loss of life and serious damage. Conventional systems can only determine the problem is in a general area and thus are more suited for small sites; when the fire detection system is activated it can send an alert to the local fire department, broadcast a prerecorded warning message and unlock the buildings access control system. Fire can be prevented by hypoxic air. Hypoxic air fire prevention systems known as oxygen reduction systems are new automatic fire prevention systems that reduce permanently the oxygen concentration inside the protected volumes so that ignition or fire spreading cannot occur.
Unlike traditional fire suppression systems that extinguish fire after it is detected, hypoxic air is able to prevent fires. At lower altitudes hypoxic air is safe to breathe for healthy individuals. All AFP systems are required to be installed and maintained in accordance with strict guidelines in order to maintain compliance with the local building code and the fire code. AFP works alongside modern architectural designs and construction materials and fire safety education to prevent and suppress structural fires. Fire damper Fire hydrant Fire protection engineering Treatise on Active and Passive Fire Protection from UK Government When Fire Strikes, Drop and... Sing? – Article about acoustic fire suppression, Scientific American, January 24, 2008 Karlsruhe Institute of Technology - Forschungsstelle für Brandschutztechnik
Acoustics is the branch of physics that deals with the study of all mechanical waves in gases and solids including topics such as vibration, sound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics technology may be called an acoustical engineer; the application of acoustics is present in all aspects of modern society with the most obvious being the audio and noise control industries. Hearing is one of the most crucial means of survival in the animal world, speech is one of the most distinctive characteristics of human development and culture. Accordingly, the science of acoustics spreads across many facets of human society—music, architecture, industrial production and more. Animal species such as songbirds and frogs use sound and hearing as a key element of mating rituals or marking territories. Art, craft and technology have provoked one another to advance the whole, as in many other fields of knowledge. Robert Bruce Lindsay's'Wheel of Acoustics' is a well accepted overview of the various fields in acoustics.
The word "acoustic" is derived from the Greek word ἀκουστικός, meaning "of or for hearing, ready to hear" and that from ἀκουστός, "heard, audible", which in turn derives from the verb ἀκούω, "I hear". The Latin synonym is "sonic", after which the term sonics used to be a synonym for acoustics and a branch of acoustics. Frequencies above and below the audible range are called "ultrasonic" and "infrasonic", respectively. In the 6th century BC, the ancient Greek philosopher Pythagoras wanted to know why some combinations of musical sounds seemed more beautiful than others, he found answers in terms of numerical ratios representing the harmonic overtone series on a string, he is reputed to have observed that when the lengths of vibrating strings are expressible as ratios of integers, the tones produced will be harmonious, the smaller the integers the more harmonious the sounds. If, for example, a string of a certain length would sound harmonious with a string of twice the length. In modern parlance, if a string sounds the note C when plucked, a string twice as long will sound a C an octave lower.
In one system of musical tuning, the tones in between are given by 16:9 for D, 8:5 for E, 3:2 for F, 4:3 for G, 6:5 for A, 16:15 for B, in ascending order. Aristotle understood that sound consisted of compressions and rarefactions of air which "falls upon and strikes the air, next to it...", a good expression of the nature of wave motion. In about 20 BC, the Roman architect and engineer Vitruvius wrote a treatise on the acoustic properties of theaters including discussion of interference and reverberation—the beginnings of architectural acoustics. In Book V of his De architectura Vitruvius describes sound as a wave comparable to a water wave extended to three dimensions, when interrupted by obstructions, would flow back and break up following waves, he described the ascending seats in ancient theaters as designed to prevent this deterioration of sound and recommended bronze vessels of appropriate sizes be placed in theaters to resonate with the fourth, fifth and so on, up to the double octave, in order to resonate with the more desirable, harmonious notes.
During the Islamic golden age, Abū Rayhān al-Bīrūnī is believed to postulated that the speed of sound was much slower than the speed of light. The physical understanding of acoustical processes advanced during and after the Scientific Revolution. Galileo Galilei but Marin Mersenne, discovered the complete laws of vibrating strings. Galileo wrote "Waves are produced by the vibrations of a sonorous body, which spread through the air, bringing to the tympanum of the ear a stimulus which the mind interprets as sound", a remarkable statement that points to the beginnings of physiological and psychological acoustics. Experimental measurements of the speed of sound in air were carried out between 1630 and 1680 by a number of investigators, prominently Mersenne. Meanwhile, Newton derived the relationship for wave velocity in solids, a cornerstone of physical acoustics; the eighteenth century saw major advances in acoustics as mathematicians applied the new techniques of calculus to elaborate theories of sound wave propagation.
In the nineteenth century the major figures of mathematical acoustics were Helmholtz in Germany, who consolidated the field of physiological acoustics, Lord Rayleigh in England, who combined the previous knowledge with his own copious contributions to the field in his monumental work The Theory of Sound. In the 19th century, Wheatstone and Henry developed the analogy between electricity and acoustics; the twentieth century saw a burgeoning of technological applications of the large body of scientific knowledge, by in place. The first such application was Sabine’s groundbreaking work in architectural acoustics, many others followed. Underwater acoustics was used for detecting submarines in the first World War. Sound recording and the telephone played important roles in a global transformation of society. Sound measurement and analysis reached new levels of accuracy and sophistication through the use of electronics and computing; the ultrasonic frequency range enabled wholly new kinds of application in industry.
New kinds of transducers were put to use. Acoustics is defined by ANSI/
A control system manages, directs, or regulates the behavior of other devices or systems using control loops. It can range from a single home heating controller using a thermostat controlling a domestic boiler to large Industrial control systems which are used for controlling processes or machines. For continuously modulated control, a feedback controller is used to automatically control a process or operation; the control system compares the value or status of the process variable being controlled with the desired value or setpoint, applies the difference as a control signal to bring the process variable output of the plant to the same value as the setpoint. For sequential and combinational logic, software logic, such as in a programmable logic controller, is used. There are two common classes of control action: closed loop. In an open-loop control system, the control action from the controller is independent of the process variable. An example of this is a central heating boiler controlled only by a timer.
The control action is the switching on or off of the boiler. The process variable is the building temperature; this controller operates the heating system for a constant time regardless of the temperature of the building. In a closed-loop control system, the control action from the controller is dependent on the desired and actual process variable. In the case of the boiler analogy, this would utilise a thermostat to monitor the building temperature, feed back a signal to ensure the controller output maintains the building temperature close to that set on the thermostat. A closed loop controller has a feedback loop which ensures the controller exerts a control action to control a process variable at the same value as the setpoint. For this reason, closed-loop controllers are called feedback controllers. In the case of linear feedback systems, a control loop including sensors, control algorithms, actuators is arranged in an attempt to regulate a variable at a setpoint. An everyday example is the cruise control on a road vehicle.
The PID algorithm in the controller restores the actual speed to the desired speed in the optimum way, with minimal delay or overshoot, by controlling the power output of the vehicle's engine. Control systems that include some sensing of the results they are trying to achieve are making use of feedback and can adapt to varying circumstances to some extent. Open-loop control systems do not make use of feedback, run only in pre-arranged ways. Logic control systems for industrial and commercial machinery were implemented by interconnected electrical relays and cam timers using ladder logic. Today, most such systems are constructed with microcontrollers or more specialized programmable logic controllers; the notation of ladder logic is still in use as a programming method for PLCs. Logic controllers may respond to switches and sensors, can cause the machinery to start and stop various operations through the use of actuators. Logic controllers are used to sequence mechanical operations in many applications.
Examples include washing machines and other systems with interrelated operations. An automatic sequential control system may trigger a series of mechanical actuators in the correct sequence to perform a task. For example, various electric and pneumatic transducers may fold and glue a cardboard box, fill it with product and seal it in an automatic packaging machine. PLC software can be written in many different ways -- SFC or statement lists. On -- off control uses a feedback controller. A simple bi-metallic domestic thermostat can be described as an on-off controller; when the temperature in the room goes below the user setting, the heater is switched on. Another example is a pressure switch on an air compressor; when the pressure drops below the setpoint the compressor is powered. Refrigerators and vacuum pumps contain similar mechanisms. Simple on -- off control systems like these can be effective. Linear control systems use negative feedback to produce a control signal to maintain the controlled PV at the desired SP.
There are several types of linear control systems with different capabilities. Proportional control is a type of linear feedback control system in which a correction is applied to the controlled variable, proportional to the difference between the desired value and the measured value. Two classic mechanical examples are the toilet bowl float proportioning valve and the fly-ball governor; the proportional control system is more complex than an on–off control system, but simpler than a proportional-integral-derivative control system used, for instance, in an automobile cruise control. On–off control will work for systems that do not require high accuracy or responsiveness, but is not effective for rapid and timely corrections and responses. Proportional control overcomes this by modulating the manipulated variable, such as a control valve, at a gain level which avoids instability, but applies correction as fast as practicable by applying the optimum quantity of proportional correction. A drawback of proportional control is that it cannot eliminate the residual SP–PV error, as it requires an error to generate a proportional output.
A PI controller can be used to overcome this. The PI controller uses a proportional term to remove the gross error, an integral term to eliminate the residual offset error by integrating the error over time. In some systems there are practical limits to the range of the MV. For example, a heater has a limit to how much heat it can produce
Heating and air conditioning is the technology of indoor and vehicular environmental comfort. Its goal is to provide acceptable indoor air quality. HVAC system design is a subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics and heat transfer. "Refrigeration" is sometimes added to the field's abbreviation, as HVAC&R or HVACR or "ventilation" is dropped, as in HACR. HVAC is an important part of residential structures such as single family homes, apartment buildings and senior living facilities, medium to large industrial and office buildings such as skyscrapers and hospitals, vehicles such as cars, airplanes and submarines, in marine environments, where safe and healthy building conditions are regulated with respect to temperature and humidity, using fresh air from outdoors. Ventilating or ventilation is the process of exchanging or replacing air in any space to provide high indoor air quality which involves temperature control, oxygen replenishment, removal of moisture, smoke, dust, airborne bacteria, carbon dioxide, other gases.
Ventilation removes unpleasant smells and excessive moisture, introduces outside air, keeps interior building air circulating, prevents stagnation of the interior air. Ventilation includes both the exchange of air to the outside as well as circulation of air within the building, it is one of the most important factors for maintaining acceptable indoor air quality in buildings. Methods for ventilating a building may be divided into natural types; the three major functions of heating and air conditioning are interrelated with the need to provide thermal comfort and acceptable indoor air quality within reasonable installation and maintenance costs. HVAC systems can be used in both commercial environments. HVAC systems can provide ventilation, maintain pressure relationships between spaces; the means of air delivery and removal from spaces is known as room air distribution. In modern buildings, the design and control systems of these functions are integrated into one or more HVAC systems. For small buildings, contractors estimate the capacity and type of system needed and design the system, selecting the appropriate refrigerant and various components needed.
For larger buildings, building service designers, mechanical engineers, or building services engineers analyze and specify the HVAC systems. Specialty mechanical contractors fabricate and commission the systems. Building permits and code-compliance inspections of the installations are required for all sizes of building. Although HVAC is executed in individual buildings or other enclosed spaces, the equipment involved is in some cases an extension of a larger district heating or district cooling network, or a combined DHC network. In such cases, the operating and maintenance aspects are simplified and metering becomes necessary to bill for the energy, consumed, in some cases energy, returned to the larger system. For example, at a given time one building may be utilizing chilled water for air conditioning and the warm water it returns may be used in another building for heating, or for the overall heating-portion of the DHC network. Basing HVAC on a larger network helps provide an economy of scale, not possible for individual buildings, for utilizing renewable energy sources such as solar heat, winter's cold, the cooling potential in some places of lakes or seawater for free cooling, the enabling function of seasonal thermal energy storage.
HVAC is based on inventions and discoveries made by Nikolay Lvov, Michael Faraday, Willis Carrier, Edwin Ruud, Reuben Trane, James Joule, William Rankine, Sadi Carnot, many others. Multiple inventions within this time frame preceded the beginnings of first comfort air conditioning system, designed in 1902 by Alfred Wolff for the New York Stock Exchange, while Willis Carrier equipped the Sacketts-Wilhems Printing Company with the process AC unit the same year. Coyne College was the first school to offer HVAC training in 1899; the invention of the components of HVAC systems went hand-in-hand with the industrial revolution, new methods of modernization, higher efficiency, system control are being introduced by companies and inventors worldwide. Heaters are appliances; this can be done via central heating. Such a system contains a boiler, furnace, or heat pump to heat water, steam, or air in a central location such as a furnace room in a home, or a mechanical room in a large building; the heat can be transferred by conduction, or radiation.
Heaters exist for various types of fuel, including solid fuels and gases. Another type of heat source is electricity heating ribbons composed of high resistance wire; this principle is used for baseboard heaters and portable heaters. Electrical heaters are used as backup or supplemental heat for heat pump systems; the heat pump gained popularity in the 1950s in the United States. Heat pumps can extract heat from various sources, such as environmental air, exhaust air from a building, or from the ground. Heat pump HVAC systems were only used in moderate climates, but with improvements in low temperature operation and reduced loads due to more efficient homes, they are increasing in popularity in cooler climates. In the case of heated water or steam, piping is used to transport the heat
A greenhouse gas is a gas that absorbs and emits radiant energy within the thermal infrared range. Greenhouse gases cause the greenhouse effect; the primary greenhouse gases in Earth's atmosphere are water vapor, carbon dioxide, nitrous oxide and ozone. Without greenhouse gases, the average temperature of Earth's surface would be about −18 °C, rather than the present average of 15 °C; the atmospheres of Venus and Titan contain greenhouse gases. Human activities since the beginning of the Industrial Revolution have produced a 40% increase in the atmospheric concentration of carbon dioxide, from 280 ppm in 1750 to 406 ppm in early 2017; this increase has occurred despite the uptake of more than half of the emissions by various natural "sinks" involved in the carbon cycle. The vast majority of anthropogenic carbon dioxide emissions come from combustion of fossil fuels, principally coal and natural gas, with additional contributions coming from deforestation, changes in land use, soil erosion and agriculture.
Should greenhouse gas emissions continue at their rate in 2017, Earth's surface temperature could exceed historical values as early as 2047, with harmful effects on ecosystems and human livelihoods. At current emission rates temperatures could increase by 2 °C, which the United Nations' IPCC designated as the upper limit to avoid "dangerous" levels, by 2036; the main gases in Earth's atmosphere are: Nitrogen and Argon. The other gases are: carbon dioxide, nitrous oxides and ozone, they are trace gases that account for a tenth of 1% of Earth's atmosphere. Greenhouse gases are those that absorb and emit infrared radiation in the wavelength range emitted by Earth. In order, the most abundant greenhouse gases in Earth's atmosphere are: Water vapor Carbon dioxide Methane Nitrous oxide Ozone Chlorofluorocarbons Hydrofluorocarbons Atmospheric concentrations are determined by the balance between sources and sinks; the proportion of an emission remaining in the atmosphere after a specified time is the "airborne fraction".
The annual airborne fraction is the ratio of the atmospheric increase in a given year to that year's total emissions. As of 2006 the annual airborne fraction for CO2 was about 0.45. The annual airborne fraction increased at a rate of 0.25 ± 0.21% per year over the period 1959–2006. The major atmospheric constituents, nitrogen and argon, are not greenhouse gases because molecules containing two atoms of the same element such as N2 and O2 have no net change in the distribution of their electrical charges when they vibrate, monatomic gases such as Ar do not have vibrational modes. Hence they are totally unaffected by infrared radiation; some molecules containing just two atoms of different elements, such as carbon monoxide and hydrogen chloride, do absorb infrared radiation, but these molecules are short-lived in the atmosphere owing to their reactivity and solubility. Therefore they do not contribute to the greenhouse effect and are omitted when discussing greenhouse gases; some gases have indirect radiative effects.
This happens in two main ways. One way is. For example and carbon monoxide are oxidized to give carbon dioxide. Oxidation of CO to CO2 directly produces an unambiguous increase in radiative forcing although the reason is subtle; the peak of the thermal IR emission from Earth's surface is close to a strong vibrational absorption band of CO2. On the other hand, the single CO vibrational band only absorbs IR at much shorter wavelengths, where the emission of radiant energy from Earth's surface is at least a factor of ten lower. Oxidation of methane to CO2, which requires reactions with the OH radical, produces an instantaneous reduction in radiative absorption and emission since CO2 is a weaker greenhouse gas than methane. However, the oxidations of CO and CH4 are entwined. In any case, the calculation of the total radiative effect includes both direct and indirect forcing. A second type of indirect effect happens when chemical reactions in the atmosphere involving these gases change the concentrations of greenhouse gases.
For example, the destruction of non-methane volatile organic compounds in the atmosphere can produce ozone. The size of the indirect effect can depend on where and when the gas is emitted. Methane has indirect effects in addition to forming CO2; the main chemical that reacts with methane in the atmosphere is the hydroxyl radical, thus more methane means that the concentration of OH goes down. Methane increases its own atmospheric lifetime and therefore its overall radiative effect; the oxidation of methane can produce both water. CO and NMVOCs produce CO2, they remove OH from the atmosphere, this leads to higher concentrations of methane. The surprising effect of this is that the global warming potential of CO is three times that of CO2; the same process that converts NMVOCs to carbon dioxide can lead to the formation of tropospheric ozone. Halocarbons have an indirect effect because they destroy stratospheric
Energy conservation effort made to reduce the consumption of energy by using less of an energy service. This can be achieved either by using energy more efficiently or by reducing the amount of service used. Energy conservation is a part of the concept of eco-sufficiency. Energy conservation reduces the need for energy services and can result in increased environmental quality, national security, personal financial security and higher savings, it is at the top of the sustainable energy hierarchy. It lowers energy costs by preventing future resource depletion. Energy can be conserved by reducing wastage and losses, improving efficiency through technological upgrades and improved operation and maintenance. On a global level energy use can be reduced by the stabilisation of population growth. Energy can only be transformed from one form to other, such as heat energy to motive power in cars, or kinetic energy of water flow to electricity in hydroelectric power plants; however machines are required to transform energy from one form to other.
The wear and friction of the components of these machine while running cause loss of quadrillions of BTU and $500 billions in industries only in USA. It is possible to minimize these losses by adopting green engineering practices to improve life cycle of the components; some countries employ carbon taxes to motivate energy users to reduce their consumption. Carbon taxes can force consumption to shift to nuclear power and other energy sources that carry different sets of environmental side effects and limitations. On the other hand, taxes on all energy consumption can reduce energy use across the board while reducing a broader array of environmental consequences arising from energy production; the state of California employs a tiered energy tax whereby every consumer receives a baseline energy allowance that carries a low tax. As usage increases above that baseline, the tax increases drastically; such programs aim to protect poorer households while creating a larger tax burden for high energy consumers.
One of the primary ways to improve energy conservation in buildings is to perform an energy audit. An energy audit is an inspection and analysis of energy use and flows for energy conservation in a building, process or system with an eye toward reducing energy input without negatively affecting output; this is accomplished by trained professionals and can be part of some of the national programs discussed above. Recent development of smartphone apps enables homeowners to complete sophisticated energy audits themselves. Building technologies and smart meters can allow energy users, both commercial and residential, to visualize the impact their energy use can have in their workplace or homes. Advanced real-time energy metering can help people save energy by their actions. In passive solar building design, windows and floors are made to collect and distribute solar energy in the form of heat in the winter and reject solar heat in the summer; this is called passive solar design or climatic design because, unlike active solar heating systems, it does not involve the use of mechanical and electrical devices.
The key to designing a passive solar building is to best take advantage of the local climate. Elements to be considered include window placement and glazing type, thermal insulation, thermal mass, shading. Passive solar design techniques can be applied most to new buildings, but existing buildings can be retrofitted. In the United States, suburban infrastructure evolved during an age of easy access to fossil fuels, which has led to transportation-dependent systems of living. Zoning reforms that allow greater urban density as well as designs for walking and bicycling can reduce energy consumed for transportation; the use of telecommuting by major corporations is a significant opportunity to conserve energy, as many Americans now work in service jobs that enable them to work from home instead of commuting to work each day. Consumers are poorly informed of the savings of energy efficient products. A prominent example of this is the energy savings that can be made by replacing an incandescent light bulb with a more modern alternative.
When purchasing light bulbs, many consumers opt for cheap incandescent bulbs, failing to take into account their higher energy costs and lower lifespans when compared to modern compact fluorescent and LED bulbs. Although these energy-efficient alternatives have a higher upfront cost, their long lifespan and low energy use can save consumers a considerable amount of money; the price of LED bulbs has been decreasing in the past five years due to improvements in semiconductor technology. Many LED bulbs on the market qualify for utility rebates that further reduce the price of purchase to the consumer. Estimates by the U. S. Department of Energy state that widespread adoption of LED lighting over the next 20 years could result in about $265 billion worth of savings in United States energy costs; the research one must put into conserving energy is too time consuming and costly for the average consumer when there are cheaper products and technology available using today's fossil fuels. Some governments and NGOs are attempting to reduce this complexity with ecolabels that make differences in energy efficiency easy to research while shopping.
To provide the kind of information and support people need to invest money and effort in energy conservation, it is important to understand and link to people's topical concerns. For instance, some retailers argue. However, health studies have demonstrated that headache, blood pressure and worker error all increase with the common over-illuminat