Thanks

You might want to ground it just in case. Connect a copper wire from the panel to a grounding rod stuck in the ground.

You can check out some solar pool heating kits at http://www.altestore.com/store/Solar-Pool-Heaters-and-Pumps/Unglazed-Solar-Pool-Heating/AquathermSolar-Industries-Pool-Packages/c1175/

Here’s a great article on solar pool heating from the US Department of Energy; http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=13230

Thanks in advance.
Oh — well in this case I’m talking about solar panels that produce electricity.

Solar electric panels (photovoltaics) use the light of the sun to produce electricity. Heat actually lowers their efficiency and causes them to produce less electricity.

‘Get the insulation right and everything else follows’ is a good axiom to follow whether considering a garden office or designing a new house. After six months in my office, one of my few regrets is not using more than the 100mm of insulation which I have in the floor, roof and walls. Its not that I am cold it’s just that, when the temperature is in single figures outside, the heating is continually cycling on and off and I would prefer a more even temperature.

The way I look at it is this; most rooms in a house are surrounded by other rooms, at least on two sides, possibly three as well as having another room above or below. Sitting in a garden office with nothing but walls, roof and floor between me and the elements I reason I must need more insulation than I have in my house. So, how much is that? Without getting too technical, it depends on the thermal performance of the insulating material, usually represented by its u value.

New houses have to be built to meet minimum u values but frankly, compared with the standards demanded in mainland Europe, the UK ones are pretty pathetic so, you would be well advised to insist on u values which exceed those currently listed in the UK Building Regulations. If your supplier doesn’t know about u values he probably doesn’t understand insulation but, as a guide, you should look for at least 100mm (4”) of insulation, preferably more.

You could, of course, have a building with minimal insulation and simply keep the heating on more during the Winter. Aside from the expense and discomfort, this approach falls down in the Summer. As well as keeping heat in, the insulation also keeps heat out. So, when the sun is blazing down, it won’t take very long for a structure with just 40mm of insulation to heat up and stay hot.

As for insulating materials, some environmentalists insist on only ‘natural’ materials but the decision is not entirely clear cut. For example, a natural material which is not as dense as a manufactured material will require a thicker wall and, therefore, more material. Also, although the energy required to manufacture synthetic insulants is a concern this ‘embedded energy’ is usually a lot less than the energy saved during their lifetime.

Heating the space throws up a number of options. It would be very attractive to use renewable energy but, by and large these are simply not economically viable. A wood burning stove is probably the most feasible renewable option but there are few stoves small enough and there is the hassle of firing it up in the morning and feeding it with logs as well as dealing with the ash. Ground or air source heat pumps are another option but are usually designed for much larger spaces and require electricity.

Since most people will need mains electricity to power computers, music centres and the like, the simplest option is electric heating and, of the systems available, underfloor electric is one of the most effective and easiest to install and operate. It is not the cheapest but will give a much more even heat than other point sources. A wind turbine to generate electricity or even photovoltaic roof tiles sounds great but again economies of scale mean that these are really not feasible for a small structure of this type.

The only free source of heat you can take advantage of is the sun. By having at least some windows facing South, you will capture some solar gain when the sun is out, even during the Autumn and Winter months. Finally, body heat and the heat put out by computers, printers and music centres etc. all mounts up especially if the space is well insulated.

Neil Johnston
http://www.articlesbase.com/home-business-articles/insulating-and-heating-a-garden-office-or-summerhouse-252013.html

Background

Instrumentation for locating levels in tanks and silos is often unreliable. The need for precise information about levels remains necessary, or even critical, in many instances. For example, in one situation a thermographer was employed to verify a liquid level in a large storage tank along the Gulf Coast prior to the arrival of a tanker ship. In continuous processes the operator must know how much capacity is available in each tank. Without that knowledge production may be impeded or, if an overflow occurs, a potentially dangerous situation created. Sometimes traditional level indicating instruments simply cannot determine levels. Foams and waxes, for instance, are difficult to detect and measure accurately.

A paper mill experienced a situation in which a tank was believed to be sized improperly, when in fact it was simply full of foam rather than liquid. De-foaming the tank proved more cost effective than unnecessarily replacing it with a larger one! A petrochemical plant hired a contractor to clean out a large tank. When the manway door was opened, sludge, which had settled to a depth high above the door, oozed forth creating a dangerous and environmentally damaging situation. For industries needing to comply with the safety and process requirements of OSHA 1910, thermography may prove to be a particularly cost-effective tool to use. Each of these situations represents a real instance where infrared could have been used to provide or verify information about the condition inside the tank or silo. Level location as well as verification of other level indicating instruments continues to be an important need in industry.

Thermal Imaging as a Method for Determining Levels

Most of the time, the materials in a tank or silo, whether solids, liquids, or gases, behave differently when subjected to a thermal transition. The materials often have differing thermal capacitance characteristics. Gases typically change temperature much more easily than liquids. Water, for instance, has a thermal capacity that is 3500 times greater than air. One Btu of energy added to a cubic foot of water will raise its temperature 0.016°F while the same energy added to the same volume of air results in a 55°F increase!

While the thermal capacity of solids may be similar to liquids, the different way in which heat is transferred permits them to be distinguished with an infrared camera. Solids, such as sludge, are influenced primarily by conductive heat transfer. Fluids (non-solids), on the other hand, are strongly influenced by convective heat transfer. The result is that the layer of solids in close contact with the tank wall, despite its often high thermal capacitance, heat and cool more rapidly than the liquid portion because they do not mix in the same way the liquid does. One issue is whether the tank/silo is half-full or half-empty. This determination requires further research by the investigator of the materials, container housing and environmental circumstances.

Necessary Environmental Conditions

Key to determining levels is to observe the tank or silo during a thermal transition. If viewed with an infrared camera while at a thermal steady state with the surroundings, no differences will be seen. In fact, tanks and silos that are full or empty often appear identical with no indication of a level. Interestingly, it is difficult to find tanks or silos that are not in transition, although it may not always yield a detectable image. Outdoors, the day/night cycle often provides sufficient driving force to create detectable differences. Even indoors, variations in air temperature are often sufficient to make thermal transitions apparent. Environmental conditions can have a direct influence on the ability to detect levels by thermal imaging. Wind, precipitation, ambient air temperature, and solar loading can all, separately or together, create or negate differences on the surface. Other factors to be considered include the temperatures of the products being stored in or moved through the tanks and silos, as well as the rates at which they are moving. Many tanks are insulated, although rarely to the extent that they will always and entirely obliterate the thermal patterns caused by levels. When insulation is covered with unpainted metal cladding, care must be taken to increase emissivity, as discussed later.

Thermal Patterns of Materials in Different Forms

The most obvious pattern is a result of a liquid/gas interface. In a situation where the product is not heated, the gas typically responds quickly to the transient situation, while the liquid responds more slowly. During the day, the gas may be warmer than the liquid;at night it is cooler. Liquid/sludge relationships may be more difficult to discern. A larger transient may be required to create a detectable image. Thin layers of sludge may also be indistinguishable from the tank bottom. Sludge buildup in the center of the tank (i.e. not in contact with the wall) is simply not detectable, although product buildup on the sidewalls is often quite obvious. Foams are often not difficult to distinguish from liquids but may appear similar to gases. Care should be taken when pushing the tank through a rapid thermal transition to reveal the thermal differences. Locating levels associated with floating materials, such as waxes, will typically require more persistence, skill and a greater rate of transitional heat transfer, but the results can be startling.

Whether or not liquid/liquid interfaces, such as a mix of oil and water, can be seen depends entirely on their differing thermal capacities and, to a lesser extent, their viscosity. Simple experiments suggest it is fairly easy to locate the interface of oil and water, but further work needs to be done in the field to validate this technique. Some solids, such as coal ash, plastic pellets, powdered lime and wood chips, behave as fluids and are designated as "fluidized solids." While heat transfer in such materials is still primarily conductive, mass transfer of heat by the material’s movement can be significant. For instance, hot ash or lime blown into a silo carries its process heat to the silo. Fluidized solids tend to behave similarly to liquids in the way they respond to gravity, except for the fact that they can "bridge" across areas where liquids typically would not. In fact, locating bridging of fluidized materials is a valuable use for thermography.

Issues to be Considered

Some tanks are covered in cladding, often unpainted aluminum or stainless steel. Detecting the kind of fine temperature differences necessary to reveal levels on surfaces such as these-ones having low emissivity and high reflectivity-is nearly impossible. The radiant difference is simply not detectable. The problem, however, is most often easily rectified by applying a high emissivity target vertically. A painted stripe or a piece of tape on the tank, for instance, can work very well. For outdoors work, use light colors and/or the shady side of the equipment to avoid solar loading. Occasionally tanks are heated or cooled with a jacket. These often cause thermal imaging cameras to be ineffective for level determination . In some instances it may be possible to see the structural "stand offs" between the tank wall and the jacket.

Tanks that are insulated can also prove challenging. Thankfully, insulation levels are typically not great enough that they preclude seeing levels; rather the insulation changes the thermal dynamics to the point where a detectable level may not be obvious as often. Simple techniques, explained below, can help enhance thermal differences so that they can be detected. In some instances it may be possible to cut small "plugs" out of the insulation at various levels that would more clearly reveal the tank temperatures. Although solar loading can enhance a pattern, more often it can cause subtle thermal patterns in a tank or silo to be obliterated. It may be possible to view the container on the shady side, but sometimes it may be necessary to return when the sun’s affect is lessened. Spheroid tanks offer another type of challenge in that, when viewed from one point, their reflectance varies widely over their curved surface. It is not unusual to find the tops of such tanks appearing cooler while the bottom appearing warmer; all too often both patterns are related more to reflectance than emission. Tanks located inside of buildings are not subjected to diurnal heating cycles. Some thermal cycling usually does take place, but it may not be enough to make the radiant differences detectable. Again, simple techniques, explained below, can be used very effectively to enhance surface temperature differences.

Simple Techniques to Enhance Thermal Patterns

Often thermal patterns can be enhanced by using simple techniques to increase transient heat transfer. It may be possible to add heating or cooling directly into or to the surface of the tank/silo. The gas head in the tank responds more quickly than the liquid. As discussed above, solids may respond in a more complex manner. An industrial hot air gun can be used to heat the surface of small to medium sized tanks. Heating even a narrow area may dramatically reveal a level. Cooling can be provided simply by wetting the surface with water. As evaporation takes place, cooling drives transient heat flow and reveals or enhances the levels. While these techniques may not seem feasible for large tanks, such is not the case. Cooling in particular can easily be supplied with a stream of cold water hosed onto the tank surface. Add the element of time for the cooling to take effect and, in many cases, the image becomes readily apparent.

Conclusion

Many industries have a critical need to determine levels in tanks and silos and to validate the already existing level-indication instrumentation. Infrared thermal imaging provides a simple, cost-effective means of doing both. Conditions often allow for levels to be seen at almost any time of the night or day and throughout the year. While levels are not always immediately obvious, persistence, careful infrared imaging and simple enhancement techniques can often produce remarkable results.

Acknowledgments

The authors would like to thank the following individuals for their assistance in the work that went into this paper: Jeff Backer, Shane Brooker, Matt Clarke, Lee Colgrove, Jeff Cordova, Keith Dodderer, Patrick Lawrence, Greg McIntosh, Rob Spring, and Mark Soult.

Please visit us at  www.electrophysics.com/snellsiloab

For more comprehensive White Papers visit our online Knowledge Center.
www.electrophysics.com/thermal-imaging

Electrophysics – IR Cameras for Thermography Professionals
373 Route 46, Fairfield, NJ 07004 Phone: 973-882-0211 Fax: 973-882-0997

Josh White
http://www.articlesbase.com/electronics-articles/locating-levels-in-tanks-and-silos-using-infrared-thermal-imaging-680088.html

Available Information On Photovoltaic Power

 

There is an enormous supply of articles on the subject of photovoltaic power. Most articles are narrow in scope, perhaps announcing a recent breakthrough or discussing a particular project or application. The internet provides a great deal of information as well, with web sites sponsored by government agencies, industry groups, and manufacturers. We did have some difficulty finding an overview of the subject. Most books on photovoltaics are at least five years old and cover the technical aspect of photovoltaics without providing an assessment of the practicality of using photovoltaics for power generation.

 

Why Photovoltaic Power Requires Study

 

The high cost of generating electrical power using photovoltaic cells compared to conventional coal-, gas-, and nuclear-powered generators has kept PV power generation from being in widespread use. Less than 1% of electricity is generated by photovoltaics. However, there are a few applications in which PV power is economical. These applications include satellites, developing countries that lack a power distribution infrastructure, and remote or rugged areas where running distribution lines are not practical. As the cost of photovoltaic systems drops, more applications become economically feasible. The non-polluting aspect of PV power can make it an attractive choice even when conventional generating systems are more economical. The manufacture of photovoltaic systems has increased steadily for the last 25 years. It is inevitable that engineers will be called upon to develop photovoltaic technology or will be involved in projects using this technology. Many existing reports on photovoltaics cover only one facet of the technology and sometimes writers inflate their reports on behalf of the company involved. There is a need for an up-to-date, objective understanding of photovoltaic power generation. With this goal in mind we have created this report.

 

Photovoltaic Technology

 

Scientists have known of the photovoltaic effect for more than 150 years. Photovoltaic power generation was not considered practical until the arrival of the space program. Early satellites needed a source of electrical power and any solution was expensive. The development of solar cells for this purpose led to their eventual use in other applications.

 

Power Output and Efficiency Ratings

 

The figures given for power output and efficiency of photovoltaic cells, modules, and systems can be misleading. It is important to understand what these figures mean and how they relate to the power available from installed photovoltaic generating systems.

 

 

 

 

 

Power Ratings

 

Photovoltaic power generation systems are rated in peak kilowatts (kWp). This is the amount of electrical power that a new, clean system is expected to deliver when the sun is directly overhead on a clear day. We can safely assume that the actual output will never quite reach this value. System output will be compromised by the angle of the sun, atmospheric conditions, dust on the collectors, and deterioration of the components. When comparing photovoltaic systems to conventional power generation systems, one should bear in mind that the PV systems are only productive during the daytime. Therefore, a 100 kW photovoltaic system can produce only a fraction of the daily output of a conventional 100 kW generator.

 

Efficiency Ratings

 

The efficiency of a photovoltaic system is the percentage of sunlight energy converted to electrical energy. The efficiency figures most often reported are laboratory results using small cells. A small cell has a lower internal resistance and will yield a higher efficiency than the larger cells used in practical applications. Additionally, photovoltaic modules are made up of numerous cells connected in series to deliver a usable voltage. Due to the internal resistance of each cell, the total resistance increases and the efficiency drops to about 70% of the single-cell value. Efficiency is higher at lower temperatures. Temperatures used in laboratory measurements may be lower than those in a practical installation.

 

Converting Sunlight to Electricity

 

A typical photovoltaic cell consists of semiconductor material (usually silicon) having a pn junction as shown in Figure 1.

 

Figure 1.Implementation of  solar cells

 

Sunlight striking the cell raises the energy level of electrons and frees them from their atomic shells. The electric field at the pn junction drives the electrons into the n region while positive charges are driven to the p region. A metal grid on the surface of the cell collects the electrons while a metal back-plate collects the positive charges .

 

Light Generates

Electron and Hole

p-Type

n-Type

 

Thin Film Technology

 

Thin-film solar cells are manufactured by applying thin layers of semiconductor materials to a solid backing material. The composition of a typical thin-film cell is shown in Figure 2. Sunlight entering the intrinsic layer generates free electrons. The p-type and n-type layers create an electric field across the intrinsic layer. The electric field drives the free electrons into the ntype layer while positive charges collect in the p-type layer. The total thickness of the p-type, intrinsic, and n-type layers is about one micron. Although less efficient than single- and polycrystal silicon, thin-film solar cells offer greater promise for large-scale power generation because of ease of mass-production and lower materials cost. Thin-film is also suitable for building-integrated systems because the semiconductor films may be applied to building materials such as glass, roofing, and siding .

 

Fig.2.

 

Using thin films instead of silicon wafers greatly reduces the amount of semiconductor material required for each cell and therefore lowers the cost of reducing photovoltaic cells. Gallium arsenide (GaAs), copper indium diselenide (CuInSe2), cadmium telluride (CdTe) and titanium dioxide (TiO2) are materials that have been used for thin film PV cells. Titanium dioxide thin films have been recently developed and are interesting because the material is transparent and can be used for windows.

 

Tin Oxide Tin oxide is a conductive material that is transparent when in a thin layer. Tin oxide is used in place of a metallic grid for the top layer of thin film photovoltaic sheets .

 

Amorphous Silicon (a-Si) Amorphous (uncrystallized) silicon is the most popular thin-film technology. It is prone to degradation and produces cell efficiencies of 5-7%. Double- and triple-junction designs raise efficiency to 8-10%. The extra layers capture different wavelengths of light. The top cell captures blue light, the middle cell captures green light, and the bottom cell captures red light. Variations include amorphous silicon carbide (a-SiC), amorphous silicongermanium (a-SiGe), microcrystalline silicon (mc-Si), and amorphous silicon-nitride (a-SiN)

.

Cadmium Telluride (CdTe) and Cadmium Sulphide (CdS) Photovoltaic cells using these materials are under development by BP Solar and Solar Cells Inc .

 

Poly-crystalline Silicon Poly-crystalline silicon offers an efficiency improvement over amorphous silicon while still using only a small amount of material.

 

Concentrating Collectors

By using a lens or mirror to concentrate the sun’s rays on a small area, it is possible to reduce the amount of photovoltaic material required. A second advantage is that greater cell efficiency can be achieved at higher light concentrations. To accommodate the higher currents in the photocells, a larger metallic grid is used. For example, in a system with a 22X concentration ratio, the grid covers about 20% of the surface of the solar cell. To prevent this from blocking 20% of the sunlight, a prism is used to redirect sunlight onto the photovoltaic material, as shown in Figure 3. A second problem is the higher temperatures of a concentrating system. The cells may be cooled with a heat sink or the heat can be used to heat water .

Fig.3.

Only direct sunlight, not scattered by clouds or haze, can be concentrated. Therefore, the concentrating collectors are less effective in locations that are frequently cloudy or hazy, such as coastal areas .

 

How much power is available from the sun?

 

Sunlight reaches the Earth’s outer atmosphere at strength of 1367 watts per square meter, defined as AM0, or “air mass zero.” Atmospheric losses reduce the sun’s power to about 1000 W/m2 when the sun is directly overhead on a cloudless day . Figure 4 shows the average daily sunlight falling on a square meter surface which has been tilted toward the southern horizon at an angle equal to the latitude of the location. Note that diffused as well as direct sunlight is considered, making this map applicable to flat plate collectors.

 

 

Fig.4.Average daily sunlight in kWh/m2

 

Conversion Efficiency

 

The most efficient PV modules usually employ single-crystal silicon cells, with efficiencies up to 15%. Poly-crystalline cells are less expensive to manufacture but yield module efficiencies of about 11%. Thin-film cells are less expensive still, but give efficiencies to about 8% and suffer greater losses from deterioration.

 

Production Considerations

 

In the past, low-grade silicon was bought from semiconductor manufacturers for use in building solar cells. With improvements in the manufacturing process, silicon manufacturers are able to consistently produce the more profitable semiconductor-grade silicon. As a result, it is becoming difficult to buy low-grade silicon. There has been much discussion about building a production facility dedicated to the production of silicon for solar cells.

 

 

 

 

 

Photovoltaic Applications

 

Photovoltaic power generation has been most useful in remote applications with small power requirements where the cost of running distribution lines was prohibitive. As PV power becomes more affordable, the use of photovoltaics for grid-connected applications is increasing. However, the high cost of PV modules and the large area they require continue to be obstacles to using PV power to supplement existing electrical utilities. An interesting approach to both of these problems is the integration of photovoltaics into building materials.

 

Building-Integrated Systems

 

Building-integrated photovoltaic (BIPV) systems offer advantages in cost and appearance by incorporating photovoltaic properties into building materials such as roofing, siding, and glass. When BIPV materials are substituted for conventional materials in new construction, the savings involved in the purchase and installation of the conventional materials are applied to the cost of the photovoltaic system. BIPV installations are architecturally more attractive than roof mounted PV structures.

 

For example, United Solar Corporation produces photovoltaic shingles that replace normal asphalt shingles. Each PV shingle replaces a seven-foot long row of asphalt shingles, and any roofer can install them. Normally, only one-third of a roof needs to be covered with PV panels to produce sufficient power for the average home. Glass manufactured with photovoltaic properties is available for use in skylights and windows. The architect can select from several colors of transparent photovoltaic glass. The tint color and depth is controlled by the type and amount of semiconductor material used in the construction of the photovoltaic glass.

 

Off-Grid Applications

 

The majority of photovoltaic power generation applications are remote, off-grid applications. These include communication satellites, terrestrial communication sites, remote homes and villages, and water pumps. These are sometimes hybrid systems that include an engine-driven generator to charge batteries when solar power is insufficient.

 

Grid-Connected Applications

 

In grid-connected application, the DC power from solar cells runs through an inverter and feeds back into the distribution system. Grid-connected systems have demonstrated an advantage in natural disasters by providing emergency power capabilities when utility power was interrupted. Although PV power is generally more expensive than utility-provided power, the use of grid connected systems is increasing.

 

The Economics Of Photovoltaic Power Generation

 

Photovoltaic efficiency and manufacturing costs have not reached the point that photovoltaic power generation can compete with conventional coal-, gas-, and nuclear-powered facilities. The cost of photovoltaic power (when storage is not required) is two to four times that of conventionally produced power. It is difficult to define this relationship precisely due to wide variations in the cost of producing and distributing conventional electrical power and other variables. Due to the wide range of these variables, some applications of photovoltaic power are economically superior to conventional systems.

 

Conclusion

However, large variations in cost of conventional electrical power, and other factors, such as cost of distribution, create situations in which the use of PV power is economically sound. PV power is used in remote applications such as communications, homes and villages in developing countries, water pumping, camping, and boating. Grid connected applications such as electric utility generating facilities and residential rooftop installations make up a smaller but more rapidly expanding segment of PV use. Furthermore, as technological advances narrow the cost gap, more applications are becoming economically feasible at an accelerating rate.

 

s.sankar
http://www.articlesbase.com/electronics-articles/a-detailed-analysis-of-power-demand-compensation-by-using-photovoltaic-power-generation-591667.html

Replacement Window Ratings Definitions The following sections define in greater detail each of the window ratings that the NFRC uses to measure the performance of windows. U-factor The rate of heat loss is indicated in terms of the U-factor (U-value) of a window assembly. Because it is a measure of heat loss through the window, the lower the U-value, the better the window will perform. When you are shopping for replacement windows be sure to talk in terms of the U-Value and not the R- Value of the windows. R-Values are a measure of how well something insulates and is typically used to judge the performance of insulation in your walls. The insulating value is indicated by the R-value which is the inverse of the U-value. The lower the U-value, the greater a window’s resistance to heat flow and the better its insulating value. Solar Heat Gain Coefficient (SHGC) The official definition of the Solar Heat Gain Coefficient is as follows: The SHGC is the fraction of incident solar radiation admitted through a window, both admitted through a window, both directly transmitted, and absorbed and subsequently released inward. SHGC is expressed as a number between 0 and 1. The lower a window’s solar heat gain coefficient, the less solar heat it transmits. While that is a very detailed definition, you are probably sitting there wondering what the heck it means! In layman’s terms solar heat gain is the same feeling you get when you stand in the sun for an extended period of time. The suns radiant heat hits your body and begins to warm your skin. After time your body has absorbed the sun’s radiant heat and you have in essence "gained" the sun’s heat. This results in your body temperature rising and you get hot and want to get out of the sun. The same principle applies to the windows in your house. As the sun beats down on your windows, the windows will begin to absorb heat gain. If the SHGC is high on your window, the heat passes right on through and starts to raise the "body temperature" of your home. By having a window with a low SHGC, you prevent the radiant heat from being able to pass through the window keeping the inside of the house cooler in the warm summer months. SHGC is the more important in Southern climates than it is in Northern because of the sun’s brutal heat. Visible Transmittance (VT) The visible transmittance (VT) is an optical property that indicates the amount of visible light transmitted. The NFRC’s VT is a whole window rating and includes the impact of the frame which does not transmit any visible light. While VT theoretically varies between 0 and 1, most values are between 0.3 and 0.8. The higher the VT, the more light is transmitted. A high VT is desirable to maximize daylight. Select windows with a higher VT to maximize daylight and view. Air Leakage (AL) Heat loss and gain occur by infiltration through cracks in the window assembly. It is indicated by an air leakage rating (AL) expressed as the equivalent cubic feet of air passing through a square foot of window area. The lower the AL, the less air will pass through cracks in the window assembly. At this time, the AL is optional. It is good to choose replacement windows that have a very low air infiltration rating. Windows with a higher air leakage window rating will let the heating or cooling out of the house. This will result in a "drafty" window and less energy efficiency. Select windows with an AL of 0.30 or less (units are cfm/sq ft). Understanding replacement window ratings is just the beginning of your research. Where you live will depend will effect which rating you want to focus on to maximize the energy efficiency of your windows. For more information on what ratings you should select depending upon your climate, feel free to find out more at the window ratings page.

Justin M Howe
http://www.articlesbase.com/home-improvement-articles/understanding-window-ratings-will-help-you-choose-the-best-replacement-windows-739202.html

With the rising energy costs and effects of global warming so prevalent today, many people are wondering if there is truth to the concept of renewable energy technology. There also appears to be confusion between alternative energy technology and renewable energy technology. Alternative energy encompasses all renewable energy sources, but includes things like nuclear power and energy from municipal waste. These are carbonaceous examples. Renewable energy technology focuses on energy that is replaced as it is being used, such as solar energy and wind energy.

With that clear, are there truly benefits on a home or small business level to renewable solar technology? Absolutely. Truthfully, by utilizing renewable energy technology on a home level you can save yourself thousands of dollars each year. Renewable energy technology has gained popularity in recent years and it has become increasingly easy to meet your home’s energy needs with just a little handyman work. With the information available about renewable energy technology, it is possible to build renewable energy products, such as a windmill or solar panel, on your own. Do-it-yourselfers are saving huge amounts of pocket change by building and installing these systems themselves. If you have the money to invest in a commercial professionally installed system, in general these are more efficient, however, savings can still be realized, and at a much faster rate, by researching and building your own renewable energy systems.

Renewable energy technology is advancing with each day. Solar electrical systems have advanced from giant roof panels to thin layers of film that are twice as conductive and work with less sunlight. There are now solar powered charges for cell phones, batteries and other small household items. Windmills have been made more aerodynamic for greater action and electricity generation. Renewable energy technology can even be seen along today’s highways as small solar/wind operation stations powering signs and lights.

Many homeowners today are looking into integrating green energy sources for developing more energy efficient homes and businesses. A green energy source is power generated through renewable resources, such as the sun, wind and water. The other benefit of green energy sources is their low contribution to global warming, pollution and other environmental issues.

The most popular of green energy sources is the sun. Energy captured from the sun is called solar energy. Of the green energy sources, solar energy is the most popular because it offers multiple options for use. It is possible to harness electrical energy from the sun using solar panels consisting of photovoltaic cells that convert energy from the sun into electricity you can use in your home or business. There are also solar hot water collectors that use the heat of the sun to produce hot water. These solar green energy sources are readily available and increasing in popularity as most homes and businesses can have them mounted on their roof and they can take advantage of lowered utility costs.

The most efficient of green energy sources is wind. Wind has been used to power water pumps for centuries, but has grown in popularity as a way to supplement home and business electricity needs. Wind is the safest and cleanest of the green energy sources as it produces no pollutants and does not contribute to global warming. Wind energy is harnessed by erecting a turbine that spins in the breeze generating electricity. Unlike the sun, which can be found almost anywhere, in order to utilize wind as a green energy source, you must live in an area where wind is readily available.

Water is also a viable participant of green energy sources. Water is less widely used as a green energy source for homes, as not all homes have an available stream to produce the needed electricity. The Amish have used water to power entire shops using conveyer belt systems, so it is an old practice, but it is still being used successfully today. As with solar and wind energy, energy harnessed from moving water is almost completely pollutant free and is generated from a renewable resource.

Corrado Vinci
http://www.articlesbase.com/home-improvement-articles/is-renewable-energy-technology-really-available-to-homeowners-693684.html

Renewable energy

 

Renewable energy sources worldwide at the end of 2006.

Renewable energy is energy generated from natural resources—such as sunlight, wind, rain, tides, and geothermal heat — which are renewable (naturally replenished). In 2006, about 18% of global final energy consumption came from renewables, with 13% coming from traditional biomass, such as wood-burning.Hydroelectricity was the next largest renewable source, providing 3% (15% of global electricity generaiton), followed by solar hot water /heating, which contributed 1.3%. Modern technologies, such as geothermal energy, wind power, solar power and ocean energy together provided some 0.8% of final energy consumption.

Climate change concerns coupled with high oil prices, peak oil and increasing government support are driving increasing renewable energy legislation, incentives and commercialization.European Union leaders reached an agreement in principle in March 2007 that 20 percent of their nations’ energy should be produced from renewable fuels by 2020, as part of its drive to cut emissions of carbon dioxide, blamed in part for global warming. Investment capital flowing into renewable energy climbed from $80 billion in 2005 to a record $100 billion in 2006.

In responce to the G8’s call on the IEA for “guidance on how to achieve a clean, clever and competitive energy future”, the IEA reported that the replacement of current technology with renewable energy could help reduce CO2 emmisions by 50% by 2050, which they claim is of crucial importance because current policies are not sustainable.

Wind power is growing at the rate of 30 percent annually, with a worldwide installed capacity of over 100 GW, and is widely used in several European countries and the United States. The manufacturing output of the photovoltaics industry reached more than 2,000 MW in 2006, and photovoltaic (PV) power stations are particularly popular in Germany. Solar thermal power stations operate in the USA and Spain, and the largest of these is the 354 MW SEGS power plant in the Mojave Desert. The world’s largest geothermal power installation is The Gevsers in California, with a rated capacity of 750 MW. Brazil has one of the largest renewable energy programs in the world, involving production of ethanol fuel from sugar cane, and ethanol now provides 18 percent of the country’s automotive fuel. Ethanol fuel is also widely available in the USA.

While there are many large-scale renewable energy projects and production, renewable technologies are also suited to small off-grid applications, sometimes in rural and remote areas, where energy is often crucial in human development. Kenya has the world’s highest household solar ownership rate with roughly 30,000 small (20–100 watt) solar power systems sold per year.

Some renewable energy technologies are criticised for being intermittent or unsightly, yet the market is growing for many forms of renewable energy.

Main renewable energy technologies

Three energy sources

The majority of renewable energy technologies are directly or indirectly powered by the sun. The Earth-Atmosphere system is in equilibrium such that heat radiation into space is equal to incoming solar radiation, the resulting level of energy within the Earth-Atmosphere system can roughly be described as the Earth’s “climate.” The hydrosphere (water) absorbs a major fraction of the incoming radiation. Most radiation is absorbed at low latitudes around the equator, but this energy is dissipated around the globe in the form of winds and ocean currents. Wave motion may play a role in the process of transferring mechanical energy between the atmosphere and the ocean through wind stress. Solar energy is also responsible for the distribution of precipitation which is tapped by hydroelectric projects, and for the growth of plants used to create biofuels.

Renewable energy flows involve natural phenomena such as sunlight, wind, tides and geothermal heat, as the International Energy Agency explains:

“Renewable energy is derived from natural processes that are replenished constantly. In its various forms, it derives directly from the sun, or from heat generated deep within the earth. Included in the definition is electricity and heat generated from solar, wind, ocean, hydropower, biomass, geothermal resources, and biofuels and hydrogen derived from renewable resources.”

Each of these sources has unique characteristics which influence how and where they are used.

Wind power

 Vestas V80 wind turbines

Airflows can be used to run wind turbines. Modern wind turbines range from around 600 kW to 5 MW of rated power, although turbines with rated output of 1.5–3 MW have become the most common for commercial use; the power output of a turbine is a function of the cube of the wind speed, so as wind speed increases, power output increases dramatically. Areas where winds are stronger and more constant, such as offshore and high altitude sites, are preferred locations for wind farms.

Since wind speed is not constant, a wind farm’s annual energy production is never as much as the sum of the generator nameplate ratings multiplied by the total hours in a year. The ratio of actual productivity in a year to this theoretical maximum is called the capacity factor. Typical capacity factors are 20-40%, with values at the upper end of the range in particularly favourable sites. For example, a 1 megawatt turbine with a capacity factor of 35% will not produce 8,760 megawatt-hours in a year, but only 0.35×24x365 = 3,066 MWh, averaging to 0.35 MW. Online data is available for some locations and the capacity factor can be calculated from the yearly output.

Globally, the long-term technical potential of wind energy is believed to be five times total current global energy production, or 40 times current electricity demand. This could require large amounts of land to be used for wind turbines, particularly in areas of higher wind resources. Offshore resources experience mean wind speeds of ~90% greater than that of land, so offshore resources could contribute substantially more energy. This number could also increase with higher altitude ground-based or airborne wind turbines.

Wind power is renewable and produces no greenhouse gases during operation, such as carbon dioxdie and methane.

Water power

Energy in water (in the form of kinetic energy, temperature differences or salinity gradients) can be harnessed and used. Since water is about 800 times denser than air, even a slow flowing stream of water, or moderate sea swell, can yield considerable amounts of energy.

 

One of 3 PELAMIS P-750 Ocean Wave Power engines in the harbour of Peniche/ Portugal.

There are many forms of water energy:

·         Hydroelectric energy is a term usually reserved for large-scale hydroelectric dams. Examples are the Grand Coulee Dam in Washington State and the Akosombo Dam in Ghana.

·         Micro hydro systems are hydroelectric power installations that typically produce up to 100 kW of power. They are often used in water rich areas as a Remote Area Power Supply (RAPS). There are many of these installations around the world, including several delivering around 50 kW in the Solomon Islands.

·         Damless hydro systems derive kinetic energy from rivers and oceans without using a dam.

·         Ocean energy  describes all the technologies to harness energy from the ocean and the sea:

o   Marine current power. Similar to tidal stream power, uses the kinetic energy of marine currents

o   Ocean thermal energy  conversion (OTEC) uses the temperature difference between the warmer surface of the ocean and the colder lower recesses. To this end, it employs a cyclic heat engine. OTEC has not been field-tested on a large scale.

o   Tidal power captures energy from the tides. Two different principles for generating energy from the tides are used at the moment:

o   Tidal motion in the vertical direction — Tides come in, raise water levels in a basin, and tides roll out. Around low tide, the water in the basin is discharged through a turbine, exploiting the stored potential energy.

o   Tidal motion in the horizontal direction — Or tidal stream power. Using tidal stream generators, like wind turbines but then in a tidal stream. Due to the high density of water, about eight-hundred times the density of air, tidal currents can have a lot of kinetic energy. Several commercial prototypes have been build, and more are in development.

·         Wave power  uses the energy in waves. Wave power machines usually take the form of floating or neutrally buoyant structures which move relative to one another or to a fixed point. Wave power has now reached commercialization.

·         Saline gradient power,  or osmotic power, is the energy retrieved from the difference in the salt concentration between seawater and river water. Reverse electrodialysis (RED), and Pressure retarded osmosis (PRO) is in research and testing phase.

·         Deep lake water cooling,  although not technically an energy generation method, can save a lot of energy in summer. It uses submerged pipes as a heat sink for climate control systems. Lake-bottom water is a year-round local constant of about 4 °C.

Solar energy use

 

Monocrystalline solar cell

In this context, “solar energy” refers to energy that is collected from sunlight. Solar energy can be applied in many ways, including to:

•           Generate electricity by heating trapped air which rotates turbines in a Solar updraft tower.

•           Generate electricity in geosynchronous orbit using solar power satellites.

•           Generate electricity using photovoltaic solar cells.

•           Generate electricity using concentrated solar power.

•           Generate hydrogen using photoelectrochemical cells.

•           Heat and cool air through use of solar chimneys.

•           Heat buildings, directly, through passive solar building design.

•           Heat foodstuffs, through solar ovens.

•           Heat water or air for domestic hot water and space heating needs using solar-thermal panels.

•           Solar air conditioning

Biofuel

Plants use photosynthesis to grow and produce biomass. Also known as biomatter, biomass can be used directly as fuel or to produce liquid biofuel. Agriculturally produced biomass fuels, such as biodiesel, ethanol and bagasse (often a by-product of sugar cane cultivation) can be burned in internal combustion engines or boilers. Typically biofuel is burned to release its stored chemical energy. Research into more efficient methods of converting biofuels and other fuels into electricity utilizing fuel cells is an area of very active work.

Liquid biofuel

 

Information on pump, California.

Liquid biofuel is usually either a bioalcohol such as ethanol fuel or a bio-oil such as biodiesel and straight vegetable oil. Biodiesel can be used in modern diesel vehicles with little or no modification to the engine and can be made from waste and virgin vegetable and animal oil and fats (lipids). Virgin vegetable oils can be used in modified diesel engines. In fact the Diesel engine was originally designed to run on vegetable oil rather than fossil fuel. A major benefit of biodiesel is lower emissions. The use of biodiesel reduces emission of carbon monoxide and other hydrocarbons by 20 to 40%.

In some areas corn, cornstalks, sugarbeets, sugar cane, and switchgrasses are grown specifically to produce ethanol (also known as grain alcohol) a liquid which can be used in internal combustion engines and fuel cells. Ethanol is being phased into the current energy infrastructure. E85 is a fuel composed of 85% ethanol and 15% gasoline that is sold to consumers. Biobutanol is being developed as an alternative to bioethanol. There is growing international criticism about biofuels from food crops with respect to issues such as food security, environmental impacts (deforestation) and energy balance.

Solid biomass

 

Sugar cane  residue can be used as a biofuel

Solid biomass is mostly commonly usually used directly as a combustible fuel, producing 10-20 MJ/kg of heat.

Its forms and sources include wood fuel,  the biogenic portion of municipal solid waste, or the unused portion of field crops. Field crops may or may not be grown intentionally as an energy crop,  and the remaining plant byproduct used as a fuel. Most types of biomass contain energy. Even cow manure still contains two-thirds of the original energy consumed by the cow. Energy harvesting via a bioreactor is a cost-effective solution to the waste disposal issues faced by the dairy farmer, and can produce enough biogas to run a farm.

With current technology, it is not ideally suited for use as a transportation fuel. Most transportation vehicles require power sources with high power density, such as that provided by internal combustion engines. These engines generally require clean burning fuels, which are generally in liquid form, and to a lesser extent, compressed gaseous phase. Liquids are more portable because they have high energy density, and they can be pumped, which makes handling easier. This is why most transportation fuels are liquids.

Non-transportation applications can usually tolerate the low power-density of external combustion engines, that can run directly on less-expensive solid biomass fuel, for combined heat and power. One type of biomass is wood, which has been used for millennia in varying quantities, and more recently is finding increased use. Two billion people currently cook every day, and heat their homes in the winter by burning biomass, which is a major contributor to man-made climate change global warming. The black soot that is being carried from Asia to polar ice caps is causing them to melt faster in the summer. In the 19th century, wood-fired steam engines were common, contributing significantly to industrial revolution unhealthy air pollution. Coal is a form of biomass that has been compressed over millennia to produce a non-renewable, highly-polluting fossil fuel.

Wood and its byproducts can now be converted through process such as gasification into biofuels such as woodgas, biogas,  methanol or ethanol fuel; although further development may be required to make these methods affordable and practical. Sugar cane residue, wheat chaff, com cobs and other plant matter can be, and are, burned quite successfully. The net carbon dioxide emissions that are added to the atmosphere by this process are only from the fossil fuel that was consumed to plant, fertilize, harvest and transport the biomass.

Processes to harvest biomass from short-rotation poplars and willows, and perennial grasses such as switchgrass, phalaris, and miscanthus, require less frequent cultivation and less nitrogen than from typical annual crops. Pelletizing miscanthus and burning it to generate electricity is being studied and may be economically viable.

Biogas

Biogas can easily be produced from current waste streams, such as: paper production, sugar production, sewage, animal waste and so forth. These various waste streams have to be slurried together and allowed to naturally ferment, producing methane gas. This can be done by converting current sewage plants into biogas plants. When a biogas plant has extracted all the methane it can, the remains are sometimes better suitable as fertilizer than the original biomass.

Alternatively biogas can be produced via advanced waste processing systems such as mechanical biological treatment. These systems recover the recyclable elements of household waste and process the biodegradable fraction in anaerobic digesters.

Renewable natural gas is a biogas which has been upgraded to a quality similar to natural gas. By upgrading the quality to that of natural gas, it becomes possible to distribute the gas to the mass market via gas grid.

Geothermal energy

 

Krafla Geothermal Station in northeast Iceland

Geothermal energy is energy obtained by tapping the heat of the earth itself, usually from kilometers deep into the Earth’s crust. It is expensive to build a power station but operating costs are low resulting in low energy costs for suitable sites. Ultimately, this energy derives from heat in the Earth’s core. The government of Iceland states: “It should be stressed that the geothermal resource is not strictly renewable in the same sense as the hydro resource.” It estimates that Iceland’s geothermal energy could provide 1700 MW for over 100 years, compared to the current production of 140 MW. Radioactive elements in the earth’s crust continuously decay, replenishing the heat. The International Energy Agency classifies geothermal power as renewable.

Three types of power plants are used to generate power from geothermal energy: dry steam, flash, and binary. Dry steam plants take steam out of fractures in the ground and use it to directly drive a turbine that spins a generator. Flash plants take hot water, usually at temperatures over 200 °C, out of the ground, and allows it to boil as it rises to the surface then separates the steam phase in steam/water separators and then runs the steam through a turbine. In binary plants, the hot water flows through heat exchangers, boiling an organic fluid that spins the turbine. The condensed steam and remaining geothermal fluid from all three types of plants are injected back into the hot rock to pick up more heat.

The geothermal energy from the core of the Earth is closer to the surface in some areas than in others. Where hot underground steam or water can be tapped and brought to the surface it may be used to generate electricity. Such geothermal power sources exist in certain geologically unstable parts of the world such as Chile, Iceland, New Zealand, United States, the Philippines and Italy. The two most prominent areas for this in the United States are in the Yellowstone basin and in northern California. Iceland produced 170 MW geothermal power and heated 86% of all houses in the year 2000 through geothermal energy. Some 8000 MW of capacity is operational in total.

There is also the potential to generate geothermal energy from hot dry rocks. Holes at least 3 km deep are drilled into the earth. Some of these holes pump water into the earth, while other holes pump hot water out. The heat resource consists of hot underground radiogenic granite rocks, which heat up when there is enough sediment between the rock and the earths surface. Several companies in Australia are exploring this technology.

Renewable energy commercialization

Costs

Source                         2001 energy costs                              Potential future energy cost

Electricity

Wind                           4–8 ¢/kWh                                                      3–10 ¢/kWh

Solar photovoltaic       25–160 ¢/kWh                                                            5–25 ¢/kWh

Solar thermal               12–34 ¢/kWh                                                  4–20 ¢/kWh

Large hydropower      2–10 ¢/kWh                                                    2–10 ¢/kWh

Small hydropower       2–12 ¢/kWh                                                    2–10 ¢/kWh

Geothermal                 2–10 ¢/kWh                                                    1–8 ¢/kWh

Biomass                       3–12 ¢/kWh                                                    4–10 ¢/kWh

Coal (comparison)       4 ¢/kWh         

Heat

Geothermal Heat         0.5–5 ¢/kWh                                                   0.5–5 ¢/kWh

Biomass — heat          1–6 ¢/kWh                                                      1–5 ¢/kWh

Low Temp solar heat 2–25 ¢/kWh                                                    2–10 ¢/kWh

All costs are in 2001 US$-cent per kilowatt-hour.

New generation of solar thermal plants

The 11 megawatt PS10 solar power tower in Spain produces electricity from the sun using 624 large movable mirrors called heliostats.

Aerial view of one of the SEGS plants.

Since 2004 there has been renewed interest in solar thermal power stations and two plants were completed during 2006/2007: the 64 MW Nevada Solar One and the 11 MW PS10 solar power tower in Spain. Three 50 MW trough plants were under construction in Spain at the end of 2007 with 10 additional 50 MW plants planned. In the United States, utilities in California and Florida have announced plans (or contracted for) at least eight new projects totaling more than 2,000 MW.

In developing countries, three world bank projects for integrated CSP/combined-cycle gas-turbine power plants in Egypt, Mexico, and Morocco were approved during 2006/2007.

There are several solar thermal power plant in the Mojave Desert which supply power to the electricity grid. Solar Energy Generating Systems (SEGS) is the name given to nine solar power plants in the Mojave Desert which were built in the 1980s. These plants have a combined capacity of 354 MW making them the largest solar power installation in the world.

World’s largest photovoltaic power plants

Several large photovoltaic power plants have been completed in Spain in 2008: the Parque Fotovoltaico Olmedilla de Alarcon (60 MW), Parque Solar Merida/Don Alvaro (30 MW), Planta solar Fuente Alamo (26 MW), Planta fotovoltaica de Lucainena de las Torres (23.2 MW), Parque Fotovoltaico Abertura Solar (23.1 MW), Parque Solar Hoya de Los Vincentes (23 MW), the Solarpark Calveron (21 MW), and the Planta Solar La Magascona (20 MW).

First Solar 40 MW PV Array installed by JUWI Group in Waldpolenz, Germany

Waldpolenz Solar Park, which will be the world’s largest thin-flim photovoltaic (PV) power system, is being built at a former military air base to the east of Leipzig in Germany. The power plant will be a 40-megawatt solar power system using state-of-the-art thin film technology, and should be finished by the end of 2009. 550,000 First Solar thin-film modules will be used, which will supply 40,000 MWh of electricity per year.

Topaz Solar Farm is a proposed 550 MW solar photovoltaic power plant which is to be built northwest of California Valley in the USA at a cost of over $1 billion. Built on 9.5 square miles (25 km2) of ranchland, the project would utilize thin-film PV panels designed and manufactured by OptiSolar in Hayward and Sacramento. The project would deliver approximately 1,100 gigawatt-hours (GWh) annually of renewable energy. The project is expected to begin construction in 2010, begin power delivery in 2011, and be fully operational by 2013.

High Plains Ranch  is a proposed 250 MW solar photovoltaic power plant which is to be built by Sun Power in the Carrizo Plain, northwest of California Valley.

However, when it comes to renewable energy systems and PV, it is not just large systems that matter. Building-Integrated Photovoltaics or “onsite” PV systems have the advantage of being matched to end use energy needs in terms of scale. So the energy is supplied close to where it is needed.

Environmental and social considerations

While most renewable energy sources do not produce pollution directly, the materials, industrial processes, and construction equipment used to create them may generate waste and pollution. Some renewable energy systems actually create environmental problems. For instance, older wind turbines can be hazardous to flying birds.

Land area required

Another environmental issue, particularly with biomass and biofuels, is the large amount of land required to harvest energy, which otherwise could be used for other purposes or left as undeveloped land. However, it should be pointed out that these fuels may reduce the need for harvesting non-renewable energy sources, such as vast strip-mined areas and slag mountains for coal, safety zones around nuclear plants, and hundreds of square miles being strip-mined for oil sands. These responses, however, do not account for the extremely high biodiversity and endemism of land used for ethanol crops, particularly sugar cane.

In the U.S., crops grown for biofuels are the most land- and water-intensive of the renewable energy sources. In 2005, about 12% of the nation’s corn crop (covering 11 million acres (45,000 km²) of farmland) was used to produce four billion gallons of ethanol—which equates to about 2% of annual U.S. gasoline consumption. For biofuels to make a much larger contribution to the energy economy, the industry will have to accelerate the development of new feedstocks, agricultural practices, and technologies that are more land and water efficient. Already, the efficiency of biofuels production has increased significantly and there are new methods to boost biofuel production.

Hydroelectric dams

The major advantage of hydroelectric systems is the elimination of the cost of fuel. Other advantages include longer life than fuel-fired generation, low operating costs, and the provision of facilities for water sports. Operation of pumped-storage plants improves the daily load factor of the generation system. Overall, hydroelectric power can be far less expensive than electricity generated from fossil fuels or nuclear energy, and areas with abundant hydroelectric power attract industry.

However, there are several major disadvantages of hydroelectric systems. These include: dislocation of people living where the reservoirs are planned, release of significant amounts of carbon dioxide at construction and flooding of the reservoir, disruption of aquatic ecosystems and birdlife, adverse impacts on the river environment, potential risks of sabotage and terrorism, and in rare cases catastrophic failure of the dam wall.

Hydroelectric power is now more difficult to site in developed nations because most major sites within these nations are either already being exploited or may be unavailable for other reasons such as environmental considerations.

Wind farms

Wind power  is one of the most environmentally friendly sources of renewable energy

A wind farm, when installed on agricultural land, has one of the lowest environmental impacts of all energy sources:

•           It occupies less land area per kilowatt-hour (kWh) of electricity generated than any other energy conversion system, apart from rooftop solar energy, and is compatible with grazing and crops.

•           It generates the energy used in its construction in just 3 months of operation, yet its operational lifetime is 20–25 years.

•           Greenhouse gas emissions and air pollution produced by its construction are tiny and declining. There are no emissions or pollution produced by its operation.

•           In substituting for base-load coal power, wind power produces a net decrease in greenhouse gas emissions and air pollution, and a net increase in biodiversity.

•           Modern wind turbines are almost silent and rotate so slowly (in terms of revolutions per minute) that they are rarely a hazard to birds.

Studies of birds and offshore wind farms in Europe have found that there are very few bird collisions. Several offshore wind sites in Europe have been in areas heavily used by seabirds. Improvements in wind turbine design, including a much slower rate of rotation of the blades and a smooth tower base instead of perchable lattice towers, have helped reduce bird mortality at wind farms around the world. However older smaller wind turbines may be hazardous to flying birds. Birds are severely impacted by fossil fuel energy; examples include birds dying from exposure to oil spills, habitat loss from acid rain and mountaintop removal coal mining, and mercury poisoning.

Other issues

Sustainability

Renewable energy sources are generally sustainable in the sense that they cannot “run out” as well as in the sense that their environmental and social impacts are generally more benign than those of fossil. However, both biomass and geothermal energy require wise management if they are to be used in a sustainable manner. For all of the other renewables, almost any realistic rate of use would be unlikely to approach their rate of replenishment by nature.

Transmission

If renewable and distribution generation were to become widespread, electric power transmission and electricity distribution systems might no longer be the main distributors of electrical energy but would operate to balance the electricity needs of local communities. Those with surplus energy would sell to areas needing “top ups”. That is, network operation would require a shift from ‘passive management’ — where generators are hooked up and the system is operated to get electricity ‘downstream’ to the consumer — to ‘active management’, wherein generators are spread across a network and inputs and outputs need to be constantly monitored to ensure proper balancing occurs within the system. Some governments and regulators are moving to address this, though much remains to be done. One potential solution is the increased use of active management of electricity transmission and distribution networks. This will require significant changes in the way that such networks are operated.

However, on a smaller scale, use of renewable energy produced on site reduces burdens on electricity distribution systems. Current systems, while rarely economically efficient, have shown that an average household with an appropriately-sized solar panel array and energy storage system needs electricity from outside sources for only a few hours per week. By matching electricity supply to end-use needs, advocates of renewable energy and the soft energy path believe electricity systems will become smaller and easier to manage, rather than the opposite.

Controversy over nuclear power as a renewable energy source

In 1983, physicist Bernard Cohen proposed that uranium is effectively inexhaustible, and could therefore be considered a renewable source of energy. He claims that fast breeder reactors, fueled by uranium extracted from seawater, could supply energy at least as long as the sun’s expected remaining lifespan of five billion years. Nuclear energy has also been referred to as “renewable” by the politicians George W. Bush, Charlie Crist,  and David Sainsbury.

Inclusion under the “renewable energy” classification could render nuclear power projects eligible for development aid under various jurisdictions. However, it has not been established that nuclear energy is inexhaustible, and issues such as peak uranium and uranium depletion are ongoing debates. No legislative body has yet included nuclear energy under any legal definition of “renewable energy sources” for provision of development support. Similarly, statutory and scientific definitions of renewable energies usually exclude nuclear energy. Commonly sourced definitions of renewable energy sources often omit or explicitly exclude nuclear energy sources as examples.Nuclear fission is not regarded as renewable by the U.S. DOE on the website “What is Energy?”

There are also environmental concerns over nuclear power, including the dangerous environmental hazards of nuclear waste and concerns that development of new plants cannot happen quickly enough to reduce CO2 emissions, such that nuclear energy is neither efficient nor effective in cutting CO2 emissions.

ADVANTAGES AND DISADVANTAGES OF RENEWABLE ENERGY:

There are many energy sources today that are extremely limited in supply. Some of these sources include oil, natural gas, and coal. It is a matter of time before they will be exhausted.

Estimates are that they can only meet our energy demands for another fifty to seventy years. So in an effort to find alternative forms of energy, the world has turned to renewable energy sources as the solution. There are many advantages and disadvantages to this.

Renewable energy sources consist of solar, hydro, wind, geothermal, ocean and biomass. The most common advantage of each is that they are renewable and cannot be depleted. They are a clean energy, as they don’t pollute the air, and they don’t contribute to global warming or greenhouse effects. Since their sources are natural the cost of operations is reduced and they also require less maintenance on their plants. A common disadvantage to all is that it is difficult to produce the large quantities of electricity their counterpart the fossil fuels are able to. Since they are also new technologies, the cost of initiating them is high.

Solar energy makes use of the sun’s energy. It is advantageous because the systems can fit into existing buildings and it does not affect land use. But since the area of the collectors is large, more materials are required. Solar radiation is also controlled by geography. And it is limited to daytime hours and non-cloudy days.

Wind energy uses the power of the wind to produce electricity. Although it is the largest job producer, it is reliant on strong winds. Wind turbines are large and, although you can use the area under them for farming, many consider them unattractive looking. They are also very noisy to operate. In addition, they threaten the wild bird population.

Hydroelectric energy uses water to produce power. This is the most reliable of all the renewable energy sources. On the down side, it affects ecology and causes downstream problems. The decay of vegetation along the riverbed can cause the buildup of methane. Methane is a contributing gas to greenhouse effect. Dams can also alter the natural river flow and affect wildlife. Colder, oxygen poor water can be released into the river, killing fish. And the release of water from the dam can cause flooding.

Geothermal energy uses steam from the Earth’s ground to generate power. It uses smaller land areas than other power plants. They can run 24 hours per day, every day of the year. Disadvantages are that it is very site specific and, along with the heat from the Earth, it can also bring up toxic chemicals when obtaining the steam. Drilling geothermal reservoirs and finding them can be an expensive task.

Biomass electricity is produced through the energies from wood, agricultural and municipal waste. It helps save on landfill waste but transportation can be expensive and ecological diversity of land may be affected. In addition, its process needs to be made simpler.

Ocean energy is a clean and abundant energy form. It does, however, have high costs. Ocean thermal energy also requires close to a forty degree Fahrenheit difference in water temperature year round. In addition, construction and laying pipes can cause damage to the ecosystem.

There are many advantages to the use of renewable energy sources. There are also some disadvantages. The fact is energy demands will continue to increase. Through research and development, as well as, new technologies, the hope is many of the disadvantages of renewable sources of energy can be eliminated and we can successfully incorporate it into our power supplies.

                                                 

N.Sankari
http://www.articlesbase.com/electronics-articles/renewable-energy-707358.html

The increasing cost of organic fuel and its hazardous effect on environment are opening the door for the massive usage of alternative energy sources. Organic fuel is exhaustible in nature and the the whole globe is worried regarding what will happen when they are exhausted. The most viable solution for this situation is to use renewable energy sources like sun, wind and tide to reduce the dependence on organic fuel. With the help of solar panel, you can convert the sunlight into energy to meet your daily energy requirements like heating water and production of electricity.

Solar panels can be installed on the roof of your house and connected to the in-house heating system. Solar panels when designed to heat water only are known as thermal solar systems. The collector of this system is capable of absorbing solar radiation and converting it into heat. After it, the process of heat conduction is done to transfer the heat from the collector to the water tank.

Photovoltaic systems are the solar panels capable of producing electricity. In case of photovotaic solar systems, an electrical field is created by placing a positively charged layer of silicon against a negatively charged layer of silicon. When sunshine falls on this field, electric charge is created. Then with the help of conductors, this charge is conducted to power household appliances.

There are many advantages of installing solar panel. This offers you the access to free and clean source of energy. You can check the environment pollution and reduce your fuel and electricity bills. Now, some of the states in US are offering incentives on solar panel installation. Estimates show that solar panels, within five years of installation are capable of covering the investment on it. It is definitely a wise investment if you are planning to stay in your home for a longer period.

Roberto Luongo
http://www.articlesbase.com/technology-articles/solar-panel-installation-an-environment-friendly-access-to-energy-677641.html