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Biofuels in the solid form has been in use ever since man discovered fire.

Wood was the first form of biofuel that was used even by the ancient people for cooking and heating

This form of fuel was discovered even before the discovery of the fossil fuels, but with the exploration of the fossil fuel like gas, coal, and oil the production and use of biofuel suffered a severe impact.

Advantages Once you've built it, tidal power is free. It produces no greenhouse gases or other waste. It needs no fuel. It produces electricity reliably. Not expensive to maintain. Tides are totally predictable. Offshore turbines and vertical-axis turbines are not ruinously expensive to build and do not have a large environmental impact. Disadvantages A barrage across an estuary is very expensive to build, and affects a very wide area - the environment is changed for many miles upstream and downstream. Many birds rely on the tide uncovering the mud flats so that they can feed. Fish can't migrate, unless "fish ladders" are installed. Only provides power for around 10 hours each day, when the tide is actually moving in or out. There are few suitable sites for tidal barrages Is it renewable? Tidal energy is renewable. The tides will continue to ebb and flow, and the energy is there for the taking.

Energy from the Sun The sun has produced energy for billions of years.  Solar energy is the sun’s rays (solar radiation) that reach the Earth. This energy can be converted into other forms of energy, such as heat and electricity.

Photovoltaic (PV devices) or “solar cells” change sunlight directly into electricity. Individual PV cells are grouped into panels and arrays of panels that can be used in a wide range of applications ranging from single small cells that charge calculator and watch batteries, to systems that power single homes, to large power plants covering many acres.

Solar energy systems do not produce air pollutants or carbon-dioxide

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

Tidal energy use harnesses the water flow created primarily by the moon orbiting the Earth. As water is pulled toward the gravity of the moon, currents are created that can turn generator turbines.

Tidal energy use involving dams creates many of the same environmental concerns as damming rivers. Tidal dams restrict fish migration and cause silt build up which affects tidal basin ecosystems in negative ways. Systems that take advantage of natural narrow channels with high tidal flow rates have less negative environmental impact than dammed systems. But they are not without environmental problems. Both systems use turbines that can cause fish kills. But these are being replaced by new, more fish friendly turbines. The art and science of environmentally friendly hydro engineering is well advanced and will certainly be applied to any tidal energy project.

Because of intermittency and variable flow problems of tidal energy, it is a very limited resource. The DOE Tidal Energy link, above, states that there are only about 40 really good sites on Earth with high enough flows to be considered economically practical

Method Cents/kW-h Limitations and Externalities WindCurrently supplies approximately 1.4% of the global electricity demand. Wind is considered to be about 30% reliable. 4.0 - 6.0 Cents/kW-h Wind is currently the only cost-effective alternative energy method, but has a number of problems. Wind farms are highly subject to lightning strikes, have high mechanical fatigue failure, are limited in size by hub stress, do not function well, if at all, under conditions of heavy rain, icing conditions or very cold climates, and are noisy and cannot be insulated for sound reduction due to their size and subsequent loss of wind velocity and power. GeothermalCurrently supplies approximately 0.23% of the global electricity demand. Geothermal is considered 90-95% reliable. 4.5 - 30 Cents/kW-h New low temperature conversion of heat to electricity is likely to make geothermal substantially more plausible (more shallow drilling possible) and less expensive. Generally, the bigger the plant, the less the cost and cost also depends upon the depth to be drilled and the temperature at the depth. The higher the temperature, the lower the cost per kwh. Cost may also be affect by where the drilling is to take place as concerns distance from the grid and another factor may be the permeability of the rock. HydroCurrently supplies around 19.9% of the global electricity demand. Hydro is considered to be 60% reliable. 5.1 - 11.3 Cents/kW-h Hydro is currently the only source of renewable energy making substantive contributions to global energy demand. Hydro plants, however, can (obviously) only be built in a limited number of places, and can significantly damage aquatic ecosystems. SolarCurrently supplies approximately 0.8% of the global electricity demand. 15 - 30 Cents/kW-h Solar power has been expensive, but soon is expected to drop to as low as 3.5 cents/kW-h. Once the silicon shortage is remedied through alternative materials, a solar energy revolution is expected.

Tide 2 - 5 Cents/kW-h Blue Energy's tidal fence, engineered and ready for implementation, would provide a land bridge (road) while also generating electricity. Environmental impact is low. Tides are highly predictable.

Method Cents/kW-h Limitations and Externalities GasCurrently supplies around 15% of the global electricity demand. 3.9 - 4.4 Cents/kW-h Gas-fired plants and generally quicker and less expensive to build than coal or nuclear, but a relatively high percentage of the cost/KWh is derived from the cost of the fuel. Due to the current (and projected future) upwards trend in gas prices, there is uncertainty around the cost / KWh over the lifetime of plants. Gas burns more cleanly than coal, but the gas itself (largely methane) is a potent greenhouse gas. Some energy conversions to calculate your cost of natural gas per kwh. 100 cubic feet (CCF)~ 1 Therm = 100,000 btu ~ 29.3 kwh. CoalCurrently supplies around 38% of the global electricity demand. 4.8 - 5.5 Cents/kW-h Increasingly difficult to build new coal plants in the developed world, due to environmental requirements governing the plants. Growing concern about coal fired plants in the developing world (China, for instance, imposes less environmental overhead, and has large supplies of high sulphur content coal). The supply of coal is plentiful, but the coal generation method is perceived to make a larger contribution to air pollution than the rest of the methods combined.

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.

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

Each day the ocean surface rises and falls because of tides. The highest point of the rise is called high tide. The lowest point is called low tide. Most places have two high tides and two low tides each day. Tides happen because of the gravitational pull of the Moon and Sun on ocean water. The Moon has a much greater impact on tides than the Sun because it is much closer. The Moon pulls water that is closest to it making a high tide on the side of the Earth closest to the Moon and there is a high tide on the opposite side of the Earth too. Low tides happen in places between the high tides. Because Earth is rotating, the tides change over time. The difference between high tide and low tide is called the tidal range. The tidal range can be as little as a few centimeters to as much as several meters depending on the shape of the ocean floor. In Canada's Bay of Fundy the tidal range is very large – 16 meters.

Burning fossil fuels creates carbon dioxide, the number one greenhouse gas contributing to global warming. Combustion of these fossil fuels is considered to be the largest contributing factor to the release of greenhouse gases into the atmosphere. In the 20th century, the average temperature of Earth rose 1 degree Fahrenheit (1°F). This was a period that saw the most prolific population growth and industrial development

Some estimates say our fossil fuel reserves will be depleted within 50 years, while others say it will be 100-120 years.

Solar technologies produce few negative environmental impacts during collector operation.

Hazardous chemicals are used in the manufacture of solar cells, creating environmental considerations in their manufacture and, in some cases, in their eventual disposal. Solar cell manufacturers minimize their use of these chemicals, recycle them when possible, and release a minimum of pollutants to the environment.

Solar power is different: although it too uses a lot of space, solar panels can be very well integrated into the urban environment, so they have virtually no impact on land use and cause very little visual pollution.