Renewable Energy In The World Today

In 2006, about 12.3% of world total primary energy consumption (TPES, includes all forms of energy) came from renewables, with the largest large fraction (10.1%) coming from traditional biomass sources, such as wood-burning. Hydroelectricity was the next largest renewable source, providing 2.2% of TPES in 2008, as well accounting for 16% of global electricity

Biomass power 52 GW

Small hydro 85 GW

Wind 121 GW

Large hydro 860 GW

Geothermal power 10 GW

Biomass power 52 GW

Geothermal power 10 GW

Large hydro 860 GW

Solar hot water 145 GWth

Geothermal heating 50 GWth

Biodiesel production 12 GL/yr

Ethanol production 67 GL/yr

Figure 1 World renewable energy supply capacity by the end of 2008, broken down in electricity generation (units: GW), thermal generation (GWth) and bio-fuel production (units: GL/year) [4].

Concentrating solar thermal power 0.5 GW

Solar hot water 145 GWth

Geothermal heating 50 GWth

Biodiesel production 12 GL/yr

Ethanol production 67 GL/yr

Figure 1 World renewable energy supply capacity by the end of 2008, broken down in electricity generation (units: GW), thermal generation (GWth) and bio-fuel production (units: GL/year) [4].

generation [3]. Fig. 1 below shows the world renewable energy supply capacity by the end of 2008 [4].

From Fig. 1, it can be seen that wind power has an installed capacity of 121 MW worldwide. The wind industry this is growing at annual rate of 30%, with widespread use in Europe and the USA [4]. The annual manufacturing output of the photovoltaics (PV) industry reached a record 6.9 GW in 2008, bringing the installed capacity to 13 MW with the largest "solar farms'' operating Germany, Spain, and Portugal. Several large solar thermal power plants operate in USA and Spain with the largest of these being the 354 MW SEGS power plant in the Mojave Desert. While being more geographically restricted than other renewable energy sources, the world's largest geothermal power installation is located in California, with a rated capacity of 750 MW [4]. Hydroelectricity is also, by its nature, more geographically limited and growth in this area has been less, about 8% for small-scale hydro projects and 3% in large-scale hydro projects. Brazil is leading the world in ethanol production from sugar cane, with ethanol now accounting for 18% of that country's automotive fuel consumption [4].

While many of the above renewable energy projects are designed for large-scale power generation for the electricity grid, several of these technologies are also very well-suited to small off-grid applications, especially in remote areas. For example, ''solar homes systems'' - consisting of a PV panel (20—100 W), battery, charge controller, and DC lights - are very popular in countries such as China, Sri Lanka, India, Bangladesh, and Kenya.

Therefore, in order to understand the potential for powering a water treatment system — whether water recycling or desalination — from renewable energy, it is important to have a good understanding of local resource availability. Fig. 2 shows the world average availability of solar irradiance, measured as the daily number of peak sunshine hours incident on a horizontal surface at an intensity of 1 kW/m2 [5].

It can be seen that the solar radiation resource is very good throughout the North America, South America, and much of Asia, while an excellent solar resource is found in Africa, the Middle East, and Australia. While this serves as a rough guide as to where solar-powered systems would be a good choice, a system designer would also need to consider seasonal variation in the solar resource and how well demand (in this case clean water) matches the supply of energy. For a critical application where, for example, the system would be the sole source of clean water for a community, solar energy systems are typically sized for the month with the least solar irradiance. This is often winter at greater latitudes, but in the tropics, this usually coincides with wet seasons.

Solar Energy Locations
Figure 2 World solar irradiance, plotted as the number the daily number of peak sunshine hours incident on a horizontal surface at an intensity of 1 kW/m2 (adapted from Ref. [5]) (see plate 6 in color plate section at the end of this book).

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0.0 1.3 2.7 3.5 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 > 12.0 Region average = 6.8084 (m/s) NASA/SSE 13 Sep 2004

Figure 3 World map of average annual wind speed at a height of 50 m based on 10 years of data (July 1983 to June 1993). Adapted from Ref. [6] (see plate 7 in color plate section at the end of this book).

Fig. 3 shows a world map of average annual wind resource, depicted as wind speed at a height of 50 m based on 10 years of data (July 1983 to June 1993) [6]. As mentioned previously, wind speeds are less near the equator and reach a maximum at latitudes in the range 40° to 60° south and north, leading to the expressions the ''roaring forties'' and the "furious fifties.'' It should be noted that often a synergy exists between the availability of wind and solar energy and, for this reason, hybrid systems, which rely on two sources renewable electricity to maximize water production over all four seasons.

Although marine energy is a much less mature technology than wind or PV, there are obvious synergies between marine energy availability and powering seawater desalination plants. Therefore, as an example of marine energy availability worldwide, Fig. 4 shows wave energy potential worldwide, determined from 15 years of satellite data [7]. The greatest opportunity for wave energy harvesting exists along those coastlines in the world that possess a western exposure to the Southern Ocean (Chile, parts of Australia and New Zealand) as well as parts of Europe (Ireland, Scotland, Iceland) and as well as western Canada and South Africa. Additional factors when selecting a site include how steady the resource is - both in strength and direction - and therefore the most promising areas are probably the

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Figure 4 Wave energy estimates (in units of kW/m) along global coastlines determined via satellite data. Adapted from Ref. [7] (see plate 8 in color plate section at the end of this book).

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Figure 4 Wave energy estimates (in units of kW/m) along global coastlines determined via satellite data. Adapted from Ref. [7] (see plate 8 in color plate section at the end of this book).

islands in the trade wind belt of the Pacific [7]. A further impetus for such development is that high cost of imported diesel that is used for power generation on these islands.

Fig. 5 compares the cost of electricity (CoE) generated from renewable energy sources (PV, wave, wind, tidal, biomass) compared to coal, gas, and nuclear. For some technologies, there is quite a spread in the CoE, which is influenced by the scale of the generation system and the quality of the renewable resource.

With the majority of renewable energy sources being variable in nature, the traditional design approach is that renewable energy powered systems will require some form of energy storage to accommodate variability in the resource availability. The only renewable energy resource that can sometimes be regarded as continuous is small-scale hydro projects, for streams and rivers that do not experience a dry season.

Energy storage can take many forms, including mechanical energy devices such as pressure accumulators and flywheels, and electrical energy storage devices such as batteries, supercapacitors, and fuel cells. Alternatively, if the water treatment system is connected to the electricity grid, electricity can be exported during times of excess generation and imported when the renewable resource provides insufficient power.

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PV Wave Tidal Wind Biomass Wind Gas Coal Nuclear Gas Coal (Offshore) BFBC (Onshore) OCGT IGCC CCGT CFBC

PV Wave Tidal Wind Biomass Wind Gas Coal Nuclear Gas Coal (Offshore) BFBC (Onshore) OCGT IGCC CCGT CFBC

Figure 5 Cost of electricity (in British pence per kWh) generated from both renewable and traditional energy sources for the UK. BFBC = bubbling fluidized bed combustion, OCGT = open cycle gas turbine, IGCC = integrated gasification combined cycle, CFBC = circulating fluidized bed combustion. Adapted from Ref. [8].

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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