Air Conditioning 2.0

Renewable Energy

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 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

Scope of Careers in Hvac – Ahead of 2009

We are living in a time of job cuts and hiring freezes. Breaking into a good career is becoming increasingly difficult all around. However, there are a few remaining secure careers that hold promise for a better tomorrow. Jobs in the HVAC field are expected to be abundant in the coming year. A career in the HVAC field is essentially risk free. These services will be needed for years to come - regardless of economic climate.

Statistics indicate that more than 163,000 people are already employed today in HVAC technologies. Better yet, employment opportunities in the HVAC field are expected to rise in 2009. The following are four sectors that are expected to produce more jobs for HVACR technicians in 2009.

1. The Blooming Commercial Aviation Sector – The commercial aviation sector is expected to regain its shape in 2009. Commercial aviation is a field that requires sophisticated climate control and air conditioning technologies. If commercial aviation grows as rapidly as projected in the coming year, there will be more career opportunities in aviation for trained HVAC technicians.

2. The Greatly Developing Marine Systems – There are many different Marine systems being developed these days. The air conditioning systems of these International and Domestic Marine vessels have to be regularly maintained. Not to mention the fact that Marine research aquariums being built today require effective climate controls. This brings about many career opportunities for HVAC technicians in the Marine sector.

3. Chemical And Food Processing Industry – The Chemical and food processing industry offers many career opportunities for air conditioning and refrigeration mechanics and installers. This trend is likely to continue through 2009.

4. Service And Installation Of Air Conditioning In Office Spaces And Skyscrapers – There is high demand right now for HVAC technicians that are capable of installing and servicing air conditioners for large commercial buildings and office spaces.

Anyone interested in working in the HVAC field should be well prepared for job challenges and familiar with all aspects of HVAC technologies. Job opportunities may be plentiful but proper HVAC training is needed to better your job prospects. HVAC technicians are also paid based on the quality of their work and their knowledge. When it comes to getting the best HVACR training, the very best campuses are located in Phoenix and Scottsdale. The Phoenix air conditioning colleges and Scottsdale refrigeration colleges offer great career assistance to any aspiring HVAC technician.

The career forecast for HVAC in 2009 will not be gloomy. The demand for HVAC mechanics and installers will be significant in 2009 with the introduction of sophisticated HVAC technologies in almost every walk of life. Good job prospects are waiting for highly skilled heating, air conditioning and refrigeration mechanics and installers - particularly those with the right technical HVAC training.

Abby Reid
http://www.articlesbase.com/college-and-university-articles/scope-of-careers-in-hvac-ahead-of-2009-701070.html

Which military division would you rather join? The Army, Air Force, Navy, Marines or National Guard?

I heard that in the Air Force, they always house you in a nice air-conditioned building. Anyway, I’m too old to enlist in the military.

Hey why didn’t you list the Coast Guard? Yeah that’s right, they are a branch of Military also.

Well I wanted to be in the Marines, but they said my High School wasn’t good enough. The Army would accept me so I went with them.

Is there a way I can switch over to the air force from army before basic training?

Hey everyone. When I was looking to join the military, there was only the marines and army nearby, so I thought. I finally found out there is a air force recruiting station near us. With that said, the more I read about the air force compared to the army, the more I want to switch over. Is there any way I can switch over to the air force from the army before I go to meps the second time and ship off to basic? I leave March 8th. Thanks.

I just hear the living conditions are much better when you’re in the air force, and I’m a technology kind of guy.

Go straight to the air force recruiter and ask them, things have changed, a lot in the past few years and the past few months, I doubt anyone except a recruiter can give you a straight answer

Is the U.S. Air Force or Marines right for a married woman?

I’m 27 years old, married for 3 years, no kids yet (but want one within the next year and a half), and am curious about joining a branch of the military. Mainly what sparks my interest in it is the confidence building and persona strengthening which joining the ranks can do for a person. I feel that strengthening as a person will help my relationships: marriage, social and parental (in the future), and I need some sort of conditioning as such. So I thought of the military.

I have already completed a 4 year college, so I am not in need of secondary education, unless it applied to flight school or something like that. I don’t know how it works with the Air Force or the Navy or Marines. I’m kind of naive and kiddish and I feel I need something to spark a reality for me, to help me become more responsible with adult realities in the world. Am I thinking the wrong thing here? Is the military out of my league? Does it required too many years’ commitment or would it interfere with my family plans in the near future?

Aim High

The Marines are not Mentally stable much less family friendly. From what i gather reading your post, I’d say You need to look in to the Air Force Reserves or Air National Guard maybe even Army National Guard. It all depends on what your hubby does for a living, rather you want to move, and what your degree is in.

Unless your hubby is a Ex-convict, who makes a living smuggling guns, drugs, or illegal aliens, has a drinking problem, and anger management issues. In that case you’d love the Marines.

Can’t decide Air Force or Marine Corps?

totally different branches i know.

I’m interest in the Air Force because right now i’m finishing up my associates degree in Computer Science and i think the Air Force can provide the best experience for such field. This will help me in the future if i decide to re-enter the civilian life. Besides that the living conditions are supposed to be the best compared to other branches and i could enlist as an E-3 opposed to an E-2 from the Marine Corps. One of the problems is that i’m a perm resident and that most of the jobs that i like require citizenship for security clearance. I would have to go in as something like paper pusher and "try" to switch out when i get my citizenship through the faster naturalization process of the military(war time: 1 day, peace time: 1 year).

The Marine Corps are the best of the best at what they do, they are Marines not soldiers. If i were to join the Marine Corps it would be a 03X(0311 - reserve and wait for an opening in rifleman). I’m the type of person who wants to physically be the best in hands to hands combat, weapons, etc. Being the best, excelling faster than anyone, and overcoming my opponent. Having the chance to be in the center of the action is something that not many people get to have and i would love to get that opportunity, going on missions and what not.

Anyways in short i really can’t decide what branch to join… another small factor that would decide where to go would be my wish list. If i could, based on the military’s need i would favor being stationed in Japan… so not sure which branch has the highest chance of that. I know both branch have a high amount of bases(huge base on okinawa for Marine Corps and okinawa + mainland for AF)

The Marines actually have relatively few bases.

Anyways… It seems like you’d rather have the AF job, but you can’t because of the citizenship issue.

If that is the case… then you could:
A. Do Marines for four years. Obtain your citizenship. Decide if you like it. If you do, then stay. If you don’t, then re-enlist in the Air Force in one of the jobs you want.
B. Do Air Force for the entire time. Retrain once you get your citizenship. Take the job you want.
C. Do Marines the entire time.

Personally, I know that my father did Marines for four years. He then went to the AF for 28. He really liked the AF after the Marines and said it was a huge change, because the AF was so relaxed. It probably wouldn’t be a good idea to go from AF to Marines. And you don’t seem to have a reason to.

That being said, the Marines are a really great thing. My dad has told me stories about how it made him a stronger person. [Both mentally and physically.] He was able to not back down from situations that once would have scared him.

Can’t decide Air Force or Marine Corps?

totally different branches i know.

I’m interest in the Air Force because right now i’m finishing up my associates degree in Computer Science and i think the Air Force can provide the best experience for such field. This will help me in the future if i decide to re-enter the civilian life. Besides that the living conditions are supposed to be the best compared to other branches and i could enlist as an E-3 opposed to an E-2 from the Marine Corps.

The Marine Corps are the best over the best, they are Marines not soldiers. If i were to join the Marine Corps it would be a 03X(0311 - reserve and wait for an opening in rifleman). I’m the type of person who wants to physically be the best in hands to hands combat, weapons, etc. Being the best, excelling faster than anyone, and overcoming my opponent. Having the chance to be in the center of the action is something that not many people get to have and i would love to get that opportunity, going on missions and what not.
typo i mean’t to say the best of* the best.
Anyways in short i really can’t decide what branch to join… another small factor that would decide where to go would be my wish list. If i could, based on the military’s need i would favor being stationed in Japan… so not sure which branch has the highest chance of that. I know both branch have a high amount of bases(huge base on okinawa for Marine Corps and okinawa + mainland for AF)
@Brandon i’m saying the are the best at what they do. Marines are not soldiers. The Army for example has a huge amount of troops and it’s more about vast vs the Marine which is smaller and more tactical.
take it as you will idc.

Personal advice. If you are torn between the Corps and the Air Force, join the Air Force. The Corps and the Air Force are so different, I don’t think anyone seriously considering the Air Force would be a good fit for the Corps.

How capable is the average Air Force Officer in ground combat?

Alright, I always hear stuff about the "Chair Force" and how they have air conditioned tents, etc. Now personally, that just sounds smart. If you have the option then heck, why not take it? I understand their superiority in the air but let’s say an Air Force pilot was grounded. How would they fare on the ground compared to say a marine?

The air force is not trained to fight on the ground, they are trained to achieve and maintain air superiority. It would be comparable to asking an infantryman to pilot a fighter plane, it just doesn’t work. Some airmen are trained in combat (combat controllers or para rescue) but the army and marines are riflemen from day one. If a pilot gets shot down, they are trained to escape and evade and let the combat forces fight their way to them. You can definitely tell when when the bullets start flying who is trained and who is not, and for this type of job, the air force is not.

safe jobs in the marines?

to everybody reading this i hope to get some solid imput from people who actually know what they r talking about preferably i would want anybody who has served overseas in this current war…so i wana go into the military and i am thinking either Marines or Air Force they both have their good points and bad points. the Marines the pride and stuff and the Air Force the living conditions and stuff but i wana know what r some of the safer marine jobs i know all about every Marine is a rifleman first and that stuff but like when u are on the bases in iraq and afghanistan idk how to spell that do like the aviation mechaincs or meteorologist go off the base and have to do patrols and shit. if anyone can help me out i would really appreciate it. thanks
holy shit u people gotta relax, idk really which answers to trust i got the recruiters telling me one thing actual marines telling me otherwise so can only actual marines answer.

Don’t take this the wrong way, but the USMC may not be for you.

If you are worried about living conditions and "stuff", as you put it, then perhaps the USMC is not for you.

You are aware those two branches are 100 percent opposites, right?

What Do you guys think of this short essay I wrote for English class?

The United States Military has been fighting for the freedom of the United States since the day this nation became an official country, the first fighting force of the U.S. was and is a Military branch called The United States Army. After that the U.S. Navy, and the U.S. Marines Corps were created. The original tough was that the Army would fight the front line battles against the British Force’s, the Navy would take care of the bay and defend the country from naval attacks; The Marines would be distributed between both the Army and the Navy because they acted as the first "sniper" soldiers on and off boats. Through history the branches of the armed forces have been called many names, raging from the famous "G.I." of the Army, the "Semen" of the Navy, and "Fly Boys" of the Air Force. Uniquely The Marine Corps soldier’s have earned different names, in almost every if not all battles the Marines have been called many names. Three are the most notable, "Jar Heads", "leathernecks", and "Devil Dogs", all three mean different things for different times and all have different meanings.

The term "Jar Head" comes from the late WWI and early/during WWII, some Marine Soldiers were called Jar Heads because other branches of the military when working along side the Marines, mostly the Army and the Navy though they had no brains because of the way that they fought there enemies. These Marines are known for face to face combat, trash talking and taking bullets to there helmets, and surviving. Also most importantly These Marines were and are willing to die for the freedom of there country, from the snowy mountains of North Korea and Germany, the swampy forests of South America, to the blazing hot temperatures of Iraq. Jar Heads are also known because there haircuts, the well known "Military Haircut" comes from the Marine nick name "Jar Heads" there haircuts are short almost shaved making there heads look like Jars. This is manly done in boot camp but many soldiers stay with the traditional haircut through there life on and off the battle field, when they come home, when they leave and when they retire. Once a Marine always a Marine, Semper Fidelis is what Leathernecks live and die by and they stick too it.

The Leatherneck Marine, Like no other will fight under the most challenging situations. If a Veteran Marine from the Vietnam war was asked what was the most difficult condition you had to fight in.? Most surely he will say the time that the Marines meet the Chines Empire, In the middle of a blizzard. The Leatherneck Marine will wait, walk, and live under the snow if they have too. Mostly known for combat on snow, the Leatherneck is patient. He will wait for his enemy, he will die of frostbite, his gun will jam frozen, and his food will not be eatable do to the freezing cold. This will all happen before the enemy even gets with in 20 miles of there platoon. But when they get there the Leatherneck will be holding his position waiting to greet his enemy as he moves in. Leathernecks were put into tanks that were made of steel, no cushions, they lived in the tanks sleeping, talking, and battling in a steel tank. Most died because of frostbite but true they stayed like true Devil Dogs they fought.

Devil Dogs are the most known out of all Marine Soldiers. They truly fought like dogs against Nazi soldiers, and that’s a good thing. They died by the hundreds in WWII, but they gave Adolf Hitler a fight that to this day he remembers. This type of Marine is ruthless, during war he cares for no one or nothing in his way but the soldier by his side. He fights with his fist, with guns, he bites, he kicks, and he gives his life to fly up the American Flag over what ever land they are fighting for. The devil dog has not been seen since WWII because now the UN has made "rules of combat" and this prevents them from fighting like this again. Do not sleep on this be sure that one day, that sleeping dog will be awaken and when this happens be sure that WWIII will follow. The Devil Dog like no other is the most respected on the battle field because he fights with his heart exposed on the tip of his rifle, as do all the other types of Marines.

Be sure that when a devil dog a Jar Head and a Leatherneck meet our enemy on the battle field, they will be reminded WHY the United states Military is the most powerful military in this world. There are no other tittles to classify next to the Marine Corps or the Marine Soldier, much respect is to be given to all our other boys and girls in other branches because they have seen there share as well but like an old saying goes " We stole the eagle from the Air Force, the anchor from the Navy and the rope from the army and on the seventh day when God said, let there be rest, we over ran his perimeter and took the globe and you can bet your ass we’ve been protecting our shores ever since." -( A very popular saying among Marines. dose not really have an Arthur.)

Do not EVER classify Marines as "Marine Soldiers" or "Marine Corps Soldiers."I would change that ASAP… The rest of the essay seems pretty good though. Jarhead came about from the regulation high and tight haircut. Leatherneck came from the leather neck piece Marines wore back in the day to keep their head erect. Devil Dogs came from the battle at Belleau Wood.