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Solar power is pollution free during use. Production end wastes and emissions are manageable using existing pollution controls.

In situations where connection to the electricity grid is difficult, costly, or impossible (such as island communities, areas not served by a power grid, illuminated roadside signs, and ocean-going vessels) harvesting solar power is often an economically competitive alternative to energy from traditional source

Intermittency: It is not available at night and is reduced when there is cloud cover, decreasing the reliability of peak output performance or requiring a means of energy storage.

Tidal energy is one of the oldest forms of energy used by humans. Indeed, tide mills, in use on the Spanish, French and British coasts, date back to 787 A.D.. Tide mills consisted of a storage pond, filled by the incoming (flood) tide through a sluice and emptied during the outgoing (ebb) tide through a water wheel. The tides turned waterwheels, producing mechanical power to mill grain. We even have one remaining in New York- which worked well into the 20th century.

Tidal power is non-polluting, reliable and predictable.Tidal barrages, undersea tidal turbines - like wind turbines but driven by the sea - and a variety of machines harnessing undersea currents are under development. Unlike wind and waves, tidal currents are entirely predictable.

A tidal range of at least 7 m is required for economical operation and for sufficient head of water for the turbines

"But if we could harness 0.1 percent of the energy in the ocean, we could support the energy needs of 15 billion people.

Like many renewable resources, geothermal resources need relatively high initial investments to access the heat, hot water and steam. But the geothermal "fuel" cost is predictable and stable. Fossil fuel supplies will increase in cost as reserves are exhausted. Fossil fuel supplies can be interrupted political disputes abroad. Renewable geothermal energy is a better long term investment.

Examples are the huge costs of global climate change; the health effects from ground level pollution of the air; future effects of pollution of water and land; military expenditures to protect petroleum sources and supply routes; and costs of safely storing radioactive waste for generations. Geothermal energy can already compete with the direct costs of conventional fuels in some locations and is a clean, indigenous, renewable resource without hidden external costs.

Estimates of the electricity generating potential of geothermal energy vary from 35 to 2,000 GW.[2] Current worldwide installed capacity is 10,715 megawatts (MW), with the largest capacity in the United States (3,086 MW),[3] Philippines, and Indonesia.

Enhanced geothermal systems (EGS), also sometimes called engineered geothermal systems, offer great potential for more than 100 GW of geothermal power which 40 times more than present geothermal power.

ultimately geothermal global resources amount to 50,000 times the energy of all oil and gas resources in the world.

Enhanced Geothermal Systems (EGS) – Often categorized under the antiquated term‘Hot Dry Rock,’ EGS is thought by several experts to refer to any resource that requires artificial stimulation. This includes resources that have to be fully engineered, or ones that produce hydrothermal fluid, but sub-commercially. Regarding the latter, one expert states that, ‘As we go further, there might be projects that require more and more stimulation.’ Although EGS technology is still young and many aspects remain unproven, several projects are currently underway. If EGS technology proves commercially successful, it is expected to allow significantly increased extension of and production from existing fields, as well as utilization of geothermal energy in previously implausible locations.

When water flows toward the shore with the incoming tide, it flows through a tidal energy system, turning a turbine that generates electricity. When the tide shifts and flows in the opposite direction, away from shore, the tidal energy system again captures the energy with a turbine and converts it into electricity.

An important source of alternative energy is hydropower: converting the flow of rivers and ocean waves and tides into electricity through dams and turbines. The best part about both of these water sources is that they’re 100 percent renewable.

The Brazilian government still awaits a reduction in solar prices to create a specific auction by the end of 2013 or the beginning of 2014. However, the Ministry of Mines and Energy (MME) does not demonstrate any signs of this happening.

In 2013, however, revenue and capacity installed are expected to double: projects will be delivered, the resolution 482/2012 will have a major impact, and X% of the National Association of Electric Energy’s (ANEEL’s) research and development (R&D) will conclude. Capacity installed expectations in 2013 will near X megawatts (MW); in 2014, X MW; in 2015, X MW; and beyond, faster expansion is expected. Currently, capacity installed for the solar market is X MW, but it is expected to reach X MW by 2017. The total possible capacity installed for Brazil is close to X gigawatts (GW). This market revenue will have a X% compound annual growth rate (CAGR) during the forecast period (2012–2017) due to ANEEL´s R&D, international events, and the resolution 482/2012 cost reductions. Now, market revenue is close to $X million and can reach $X million by 2017.

Distributed generation could grow faster with financial support, better service from energy concessionaries, and cost reductions; nonetheless, it will grow considerably.

Biofuels are liquid fuels which have been derived from other materials such as waste plant and animal matter. There are two main types of biofuels – bioethanol and biodiesel. Bioethanol is used as a replacement for gasoline and biodiesel is used as a replacement for diesel.

Organic matter is one such source. Materials like corn and soybeans have oil extracts that can be converted to ethanol or biodiesel

more sustainable than petroleum, meaning they can be regrown and remain productive with less negative impact on our ecosystem.

Some biofuels that provide more long-term benefits may prove too expensive to pursue

1) Individual silicon based (most commonly) cells called photovoltaics (PV) make up the modern day solar panel. These PV cell clusters perform the task of converting incoming sunlight directly into electricity. 2) Wires attached to the panels transport the converted electricity to a piece of equipment called an inverter. The job of the inverter is to convert the solar generated Direct Current (DC) electricity into the type of power your home can use, which is called Alternating Current (AC). 3) After the electricity travels through the inverter, the AC electricity is then transported via wire to your breaker panel to meet your home’s electric demands. 4) The process doesn’t end there, though. There are times when your panels will generate more power than you consume and times when you aren’t generating enough electricity (night times and periods of low light). When your panels are not generating enough solar electricity, you will continue to get power from your local utility. However, when you’re generating a surplus of solar electricity, that excess clean energy will be “net metered” to your local utility grid and you may earn a credit on your power bill for that net metered electricity.

Geothermal energy is essentially free heat that comes from under your feet,

Additionally, the generation of geothermal energy in the U.S. is enough to power over two million homes.

"The industry is growing now, because over the past decade both the federal and state government have put in place laws and policies to really promote clean energy".

It was used in the watermills along the shores of England during the Roman age and also used along the shores of France and Spain. This period was around 900 AD. The water rising from the tides was impounded in barrages and it was allowed to flow through waterwheels and other energy capturing devices thus capturing the energy and converting it into useful work used to grind grains and produce flour. The first tidal mill in the US was built in Salem, MA in 1635.

If hydrogen extraction is performed using electricity from a coal-driven power plant, it doesn't matter that the fuel cell doesn't pollute because the pollution occurred when the hydrogen was extracted. If hydrogen is to be a true nonpolluting power source, the electricity used to extract the hydrogen will need to be produced by a nonpolluting method such as solar power.

I recognize this may seem like fantasy, but if the proponents of solar energy and other clean energy alternatives really want it to succeed they must get off life support, be free from the addiction to unsustainable subsidies, and given a chance to grow and thrive on their own in a healthy, competitive market environment where innovation and hard work create sustainable market equilibrium.

The Pelamis is an offshore wave energy converter that uses the motion of waves to generate electricity.

The machine operates in water depths greater than 50m and is typically installed 2-10km from the coast. The machine is rated at 750kW with a target capacity factor of 25-40 per cent, depending on the conditions at the chosen project site. On average one machine will provide sufficient power to meet the annual electricity demand of approximately 500 homes.

The Pelamis machine is made up of five tube sections linked by universal joints which allow flexing in two directions. The machine floats semi-submerged on the surface of the water and inherently faces into the direction of the waves. As waves pass down the length of the machine and the sections bend in the water, the movement is converted into electricity via hydraulic power take-off systems housed inside each joint of the machine tubes, and power is transmitted to shore using standard subsea cables and equipment.

With this technology, sea water turbines do not come into contact with water

Instead, a column of air is set in motion which drives the machines. In detail, this works in the following manner: The waves spill into a hollow container which is open to the sea. This compresses and calms the air column in a so-called collector in a similar way to how an air pump works. The power plant "breathes" in and out. The pressure difference is then turned into rotary energy in a so-called Wells turbine (named after its inventor). This is in turn passed to a generator where electricity is produced. This means that the turbine has the air periodically flow through it from both sides, depending on whether the device is "breathing" in or out. Because of the special rotor geometry, there is no need to either periodically change the blade angles or the direction of rotation. If you consider the fact that an average of some 3 million waves break on to the coast every year, it is clear that only this simple turbine design can offer maximum reliability.

Since 1998, the Pelamis development programme has covered all aspects of the design from the fundamental concept refinement through to accelerated cycle testing of individual components for reliability.

During the first phase of Pelamis development prior to full-scale operations in 2004, extensive numerical modelling and analysis and a range of technology demonstration models at different scales were used to understand survival characteristics in extreme waves and verify the accuracy of our simulations