Eco energy

Geothermal energy

posted 14 Feb 2010, 00:48 by Toby Roscoe   [ updated 14 Feb 2010, 00:54 ]

Geothermal energy is an energy source that has the potential to gather ample energy from the Earth’s hot interior for the millennia to come. At the moment it is only hotspots (focussed intrusions of magma) close to the surface that are economic to harvest energy from commercially. Huge capital investment is required, but economic payback is sure to be immense in the coming decades given the life-span of these projects. The other plus side is that geothermal plants have very few ongoing emissions or maintenance.

The first geothermal plant was conceived over a hundred years ago, the theory behind this source of energy is very simple.  Water is pumped into a shaft drilled in the ground, to a point where the rocks are super-heated,  the water filters through the fractured rocks, is heated, and eventually returns to the surface through a second shaft, re-emerging as steam. The steam is then used to drive a turbine as is a conventional power station.  

Two of the more modern types of geothermal power plants are explained below.

Flash Steam Power Plants

Hydrothermal fluids above 182°C (360°F) can be used in flash plants to make electricity. Fluid is sprayed into a tank held at a much lower pressure than the fluid, causing some of the fluid to rapidly vaporize, or "flash." The vapor then drives a turbine, which drives a generator. If any liquid remains in the tank, it can be flashed again in a second tank to extract even more energy. A contra-flow heat system is used so that the warmest production steam in the system is exposes to the strongest geothermal heat, and thus maximising the heat transfer (the rate of heat transfer is proportional to the difference in temperatures and the level ofresistance to the flow of heat). 

Most geothermal areas contain moderate-temperature water (below 210°C). Energy is extracted from these fluids in binary-cycle power plants. Hot geothermal fluid and a secondary (hence, "binary") fluid with a much lower boiling point than water pass through a heat exchanger. 

Heat from the geothermal fluid causes the secondary fluid to flash to vapor, which then drives the turbines. Because this is a closed-loop system, virtually nothing is emitted to the atmosphere. Moderate-temperature water is by far the more common geothermal resource, and most geothermal power plants in the future will be binary-cycle plants.

Fig.1. Binary cycle plant.

Micro hydro-electric

posted 14 Feb 2010, 00:39 by Toby Roscoe   [ updated 14 Feb 2010, 00:47 ]

Hydro electricity is actually another form of stored solar energy, with a little bit of geothermal energy thrown in from deep-sea geothermal vents at mid ocean ridges. They both combine to put enough energy into ocean water (and other sources of water) to evaporate it, the atmosphere then carries it to altitude, where it gains gravitational potential energy (GPE). Streams and rivers rarely stop flowing in the UK, mean that hydro is one of the most reliable sources of renewable energy.

Micro-hydro energy production has had some exciting commercial successes in the last couple of years, with units available off the shelf for almost any site. The rate at which you can harvest energy available from water at your site is directly linked with the head (the vertical distance that the water is able to fall before going through the turbine), but units are also available that can be used in the flow channel of the stream or small river.

See the YouTube videos to the right of this page or read more on micro hydro electricity from Wikipedia below

Micro hydro is a term used for hydroelectric power installations that typically produce up to 100 kW of power. These installations can provide power to an isolated home or small community, or are sometimes connected to electric power networks. There are many of these installations around the world, particularly in developing nations as they can provide an economical source of energy without purchase of fuel. [1]

Micro hydro systems complement photovoltaic solar energy systems because in many areas, water flow, and thus available hydro power, is highest in the winter when solar energy is at a minimum.

Micro hydro is frequently accomplished with a pelton wheel for high head, low flow water supply. The installation is often just a small dammed pool, at the top of a waterfall, with several hundred feet of pipe leading to a small generator housing.

Construction & characteristics

A penstock pipe used in an Afghanistan micro-hydro project

Construction details of a microhydro plant are site-specific, but the common elements of all hydroelectric plants are present. A supply of water is needed — this can be a mountain stream, or a river. Usually microhydro installations do not have a dam and reservoir, relying on a minimal flow of water to be available year-round. Sometimes an existing mill-pond or other artificial reservoir is available and can be adapted for power production. An intake structure is required to screen out floating debris and fish, using a screen or array of bars to keep out large objects. In temperate climates this structure must resist ice as well. The intake may have a gate to allow the system to be dewatered for inspection and maintenance.

Water withdrawn from the source must move along a power canal or a pipe (penstock) to the turbine. If the water source and turbine are far apart, the construction of the penstock may be the largest part of the costs of construction. In mountainous areas, access to the route of the penstock may provide considerable challenges.

At the turbine, a controlling valve is installed to regulate the flow and the speed of the turbine. The turbine converts the flow and pressure of the water to mechanical energy; the water emerging from the turbine returns to the natural watercourse along a tailrace channel.

The turbine turns a generator, which is then connected to electrical loads; this might be directly connected to the power system of a single building in very small installations, or may be connected to a community distribution system for several homes or buildings.

[edit]Regulation & operation

Typically, an automatic controller operates the turbine inlet valve to maintain constant speed (and frequency) when the load changes on the generator. In a system connected to a grid with multiple sources, the turbine control ensures that power always flows out from the generator to the system. The frequency of the alternating current generated needs to match the local standard utility frequency. In some systems, if the useful load on the generator is not high enough, a load bank may be automatically connected to the generator to dissipate energy not required by the load; while this wastes energy, it may be required if its not possible to stop the water flow through the turbine.

An induction generator always operates at the grid frequency irrespective of its rotation speed; all that is necessary is to ensure that it is driven by the turbine faster than the synchronous speed so that it generates power rather than consuming it. Other types of generator require a speed control systems for frequency matching.

With the availability of modern power electronics it is often easier to operate the generator at an arbitrary frequency and feed its output through an inverter which produces output at grid frequency. Power electronics now allow the use of permanent magnet alternators that produce wild AC to be stabilised. . This approach allows low speed / low head water turbines to be competitive; they can run at the best speed for extraction of energy, and the power frequency is controlled by the electronics instead of the generator.

Very small installations, a few kilowatts or smaller, may generate direct current and charge batteries for peak use times.

[edit]Turbine types

Several different types of water turbines can be used in micro hydro installations, selection depending on the head of water, the volume of flow, and such factors as availability of local maintenance and transport of equipment to the site. For mountainous regions where a waterfall of 50 meters or more may be available, a Pelton wheel can be used. For low head installations, Francis or propeller-type turbines are used. Very low head installations of only a few meters may use propeller-type turbines in a pit. The very smallest micro hydro installations may successfully use industrial centrifugal pumps, run in reverse as prime movers; while the efficiency may not be as high as a purpose-built runner, the relatively low cost makes the projects economically feasible.

In low-head installations, maintenance and mechanism costs often become important. A low-head system moves larger amounts of water, and is more likely to encounter surface debris. For this reason a Banki turbine, a pressurized self-cleaning crossflow waterwheel, is often preferred for low-head microhydropower systems. Though less efficient, its simpler structure is less expensive than other low-head turbines of the same capacity. Since the water flows in, then out of it, it cleans itself and is less prone to jam with debris.

Two low-head schemes in England, Settle Hydro and Torrs Hydro use a reverse Archimedes' screw which is another debris-tolerant design. Other options include Gorlov[2], Francis and propeller turbines[3].


posted 14 Feb 2010, 00:31 by Toby Roscoe   [ updated 14 Feb 2010, 00:36 ]

Photovoltaics, or PV for short, is a technology that converts light directly into electricity. Due to the growing need for solar energy, the manufacture of solar cells and solar photovoltaic array has expanded dramatically in recent years and grants of 50% of the cost of the equipment and installation are available due to the reduced impact of these systems on our climate. 

There are two configurations for your PV system, either grid-tied or stand-alone. Grid-tied PV has the advantage of being cheaper to install, as no battery system is required, instead electricity produced is sold to the grid when production is greater that required (during the day) and electricity is bought from the grid when demand is greater than production (at night or at other peak times). A synchronous grid-connected inverter is needed to step-up the voltage from the PV array, which is usually 12-24V to the 220-240V of the grid. This device also moderates the alternations in current to be in phase with the grid.  

Email us or visit the Energy Saving Trust for more details.

More from Wikipedia:

(PVs) are arrays of cells containing a Solar photovoltaic material that converts solar radiation into direct current electricity. Materials presently used for photovoltaics include monocrystalline siliconpolycrystalline siliconmicrocrystalline siliconcadmium telluride, and copper indium selenide/sulfide.[1] Due to the growing demand for renewable energy sources, the manufacture of solar cells and photovoltaic arrays has advanced dramatically in recent years.[2][3][4]

Photovoltaic production has been doubling every 2 years, increasing by an average of 48 percent each year since 2002, making it the world’s fastest-growing energy technology.[5] At the end of 2008, the cumulative global PV installations reached 15,200 megawatts.[6][7] Roughly 90% of this generating capacity consists of grid-tied electrical systems. Such installations may be ground-mounted (and sometimes integrated with farming and grazing) [8] or built into the roof or walls of a building, known as Building Integrated Photovoltaics or BIPV for short.[9] Solar PV power stations today have capacities ranging from 10-60 MW although proposed solar PV power stations will have a capacity of 150 MW or more.[1]

Driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaics has declined steadily since the first solar cells were manufactured.[10] Net metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity, have supported solar PV installations in many countries.

Photovoltaics are best known as a method for generating electric power by using solar cells to convert energy from the sun into electricity. Thephotovoltaic effect refers to photons of light knocking electrons into a higher state of energy to create electricity. The term photovoltaic denotes the unbiased operating mode of a photodiode in which current through the device is entirely due to the transduced light energy. Virtually all photovoltaic devices are some type of photodiode.

Solar cells produce direct current electricity from light, which can be used to power equipment or to recharge a battery. The first practical application of photovoltaics was to power orbiting satellites and other spacecraft, but today the majority of photovoltaic modules are used for grid connected power generation. In this case an inverter is required to convert the DC to AC. There is a smaller market for off-grid power for remote dwellings, boatsrecreational vehicles, electric cars, roadside emergency telephones, remote sensing, and cathodic protection of pipelines.

Average solar irradiance, watts per square metre. Note that this is for a horizontal surface, whereas solar panels are normally mounted at an angle and receive more energy per unit area. The small black dots show the area of solar panels needed to generate all of the world's energy using 8% efficient photovoltaics.

Cells require protection from the environment and are usually packaged tightly behind a glass sheet. When more power is required than a single cell can deliver, cells are electrically connected together to formphotovoltaic modules, or solar panels. A single module is enough to power an emergency telephone, but for a house or a power plant the modules must be arranged in multiples as arrays. Although the selling price of modules is still too high to compete with grid electricity in most places, significant financial incentives in Japan and then Germany, Italy and France triggered a huge growth in demand, followed quickly by production. In 2008, Spain installed 45% of all photovoltaics, but a change in law limiting the feed-in tariff is expected to cause a precipitous drop in the rate of new installations there, from an extra 2500 MW in 2008 to an expected additional 375 MW in 2009.[11]

Perhaps not unexpectedly, a significant market has emerged in off-grid locations for solar-power-charged storage-battery based solutions. These often provide the only electricity available.[12] The first commercial installation of this kind was in 1966 on Ogami Island in Japan to transitionOgami Lighthouse from gas torch to fully self-sufficient electrical power.

World solar photovoltaic (PV) installations were 2.826 gigawatts peak (GWp) in 2007, and 5.95 gigawatts in 2008, a 110% increase.[13][14] The three leading countries (Germany, Japan and the US) represent nearly 89% of the total worldwide PV installed capacity. According to Navigant Consulting and Electronic Trend Publications, the estimated PV worldwide installations outlooks of 2012 are 18.8GW and 12.3GW respectively. Notably, the manufacture of solar cells and modules had expanded in coming years.

Germany was the fastest growing major PV market in the world from 2006 to 2007. By 2008, 5.337 GWp of PV was installed, or 35% of the world total.[7] The German PV industry generates over 10,000 jobs in production, distribution and installation. By the end of 2006, nearly 88% of all solar PV installations in the EU were in grid-tied applications in Germany.[2] Photovoltaic power capacity is measured as maximum power output under standardized test conditions (STC) in "Wp" (Watts peak).[15] The actual power output at a particular point in time may be less than or greater than this standardized, or "rated," value, depending on geographical location, time of day, weather conditions, and other factors.[16] Solar photovoltaic array capacity factors are typically under 25%, which is lower than many other industrial sources of electricity.[17] Therefore the 2008 installed base peak output would have provided an average output of 3.04 GW (assuming 20% × 15,200 MWp). This represented 0.15 percent of global demand at the time.[18]

The EPIA/Greenpeace Advanced Scenario shows that by the year 2030, PV systems could be generating approximately 1,864 GW of electricity around the world. This means that, assuming a serious commitment is made to energy efficiency, enough solar power would be produced globally in twenty-five years’ time to satisfy the electricity needs of almost 14% of the world’s population.[19]

Solar hot water

posted 14 Feb 2010, 00:23 by Toby Roscoe   [ updated 14 Feb 2010, 00:31 ]

One of the simplest and most cost-efficient ways of using the Sun’s energy is to fit a high-efficiency evacuated tube solar water heater to your existing hot water system. It concentrates the Sun’s energy to preheat water before it is finally heated to the desired temperature by your boiler. The energy saving is considerable and in summer the solar water heater may provide all of your hot water needs. A solar hot water heating system should be designed by an energy efficiency expert and then installed by a licensed plumber, however, DIY options are available.

Solar water heating or solar hot water is water heated by the use of solar energy. Solar heating systems are generally composed of solar thermalcollectors, a water storage tank or another point of usage, interconnecting pipes and a fluid system to move the heat from the collector to the tank. This thermodynamic approach is distinct from semiconductor photovoltaic (PV) cells that generate electricity from light; solar water heating deals with the direct heating of liquids by the sun where no electricity is directly generated. A solar water heating system may use electricity for pumping the fluid, and have a reservoir or tank for heat storage and subsequent use. The water can be heated for a wide variety of uses, including home, business and industrial uses. Heating swimming pools, underfloor heating or energy input for space heating or cooling are common examples of solar water heating. A solar water heating system can form part of a solar thermal cooling system, promoting efficient temperature control of buildings or parts thereof. During cool conditions, the same system can provide hot water.

Wind energy

posted 14 Feb 2010, 00:11 by Toby Roscoe   [ updated 14 Feb 2010, 00:20 ]

In many areas of the UK energy captured from the wind has great potential to offer a sustainable supply of electricity, whether produced by a large wind farm or a smaller domestic turbine. As with other types of renewable energy, upfront costs are often seen as a disincentive, but there are now excellent schemes for interest-free loans and Government grants on the cost of equipment and installation.

In planning a wind generator the first thing to consider is whether your site is suitable and are you likely to be granted planning permission form your local council? The good news is that the national government’s obligations to the sustainable development objectives of the European Union mean that planning offices are finding it harder to refuse permission for micro-generation of renewable energy.

Unfortunately, refreshing changes to government policy cannot bring constantly gusting winds, so it is important to analyse the characteristics of the wind at your site to make sure that your wind turbine will create a viable amount of energy for your use. For information check out these links:

General enquiries: Energy Saving Trust

Private buildings: Low Carbon Buildings Phase One

Public buildings: Low Carbon Buildings Phase Two 

If you have grant scheme details for your country, state, province or territory please email us, we’d love to be able to make the information accessible to everyone by posting them here.

More info from Wikipedia:

The Earth is unevenly heated by the sun, such that the poles receive less energy from the sun than the equator; along with this, dry land heats up (and cools down) more quickly than the seas do. The differential heating drives a globalatmospheric convection system reaching from the Earth's surface to the stratosphere which acts as a virtual ceiling. Most of the energy stored in these wind movements can be found at high altitudes where continuous wind speeds of over 160 km/h (99 mph) occur. Eventually, the wind energy is converted through friction into diffuse heat throughout the Earth's surface and the atmosphere.

The total amount of economically extractable power available from the wind is considerably more than present human power use from all sources.[8] An estimated 72 terawatt (TW) of wind power on the Earth potentially can be commercially viable,[9] compared to about 15 TW average global power consumption from all sources in 2005. Not all the energy of the wind flowing past a given point can be recovered (see Betz' law).

There are now many thousands of wind turbines operating, with a total nameplate capacity of 157,899 MW of which wind power in Europe accounts for 48% (2009). World wind generation capacity more than quadrupled between 2000 and 2006, doubling about every three years. 81% of wind power installations are in the US and Europe. The share of the top five countries in terms of new installations fell from 71% in 2004 to 62% in 2006, but climbed to 73% by 2008 as those countries—the United States, Germany, Spain, China, and India—have seen substantial capacity growth in the past two years (see chart).

By 2010, the World Wind Energy Association expects 160 GW of capacity to be installed worldwide,[55]up from 73.9 GW at the end of 2006, implying an anticipated net growth rate of more than 21% per year.

Denmark generates nearly one-fifth of its electricity with wind turbines—the highest percentage of any country—and is ninth in the world in total wind power generation. Denmark is prominent in the manufacturing and use of wind turbines, with a commitment made in the 1970s to eventually produce half of the country's power by wind.

In recent years, the US has added more wind energy to its grid than any other country, with a growth in power capacity of 45% to 16.8 GW in 2007[56] and surpassing Germany's nameplate capacity in 2008.California was one of the incubators of the modern wind power industry, and led the U.S. in installed capacity for many years; however, by the end of 2006, Texas became the leading wind power state andcontinues to extend its lead. At the end of 2008, the state had 7,116 MW installed, which would have ranked it sixth in the world if Texas was a separate country. Iowa and Minnesota each grew to more than 1 GW installed by the end of 2007; in 2008 they were joined by Oregon, Washington, and Colorado.[57]Wind power generation in the U.S. was up 31.8% in February, 2007 from February, 2006.[58] The average output of one MW of wind power is equivalent to the average electricity consumption of about 250 American households. According to the American Wind Energy Association, wind will generate enough electricity in 2008 to power just over 1% (equivalent to 4.5 million households) of total electricity in U.S., up from less than 0.1% in 1999. U.S. Department of Energy studies have concluded wind harvested in the Great Plains states of Texas, Kansas, and North Dakota could provide enough electricity to power the entire nation, and that offshore wind farms could do the same job.[59][60] In addition, the wind resource over and around the Great Lakes, recoverable with currently available technology, could by itself provide 80% as much power as the U.S. and Canada currently generate from non-renewable resources,[61] with Michigan's share alone equating to one third of current U.S. electricity demand.[62]

China had originally set a generating target of 30,000 MW by 2020 from renewable energy sources, but reached 22,500 MW by end of 2009 and could easily surpass 30,000 MW by end of 2010. Indigenous wind power could generate up to 253,000 MW.[63] A Chinese renewable energy law was adopted in November 2004, following the World Wind Energy Conference organized by the Chinese and the World Wind Energy Association. By 2008, wind power was growing faster in China than the government had planned, and indeed faster in percentage terms than in any other large country, having more than doubled each year since 2005. Policymakers doubled their wind power prediction for 2010, after the wind industry reached the original goal of 5 GW three years ahead of schedule.[64] Current trends suggest an actual installed capacity near 20 GW by 2010, with China shortly thereafter pursuing the United States for the world wind power lead.[64]

India ranks 5th in the world with a total wind power capacity of 9,587 MW in 2008,[1] or 3% of all electricity produced in India. The World Wind Energy Conference in New Delhi in November 2006 has given additional impetus to the Indian wind industry.[55] Muppandal village in Tamil Nadu state, India, has several wind turbine farms in its vicinity, and is one of the major wind energy harnessing centres in India led by majors like SuzlonVestasMicon among others.[65][66]

Mexico recently opened La Venta II wind power project as an important step in reducing Mexico's consumption of fossil fuels. The 88 MW project is the first of its kind in Mexico, and will provide 13 percent of the electricity needs of the state of Oaxaca. By 2012 the project will have a capacity of 3500 MW.

Another growing market is Brazil, with a wind potential of 143 GW.[67] The federal government has created an incentive program, called Proinfa,[68] to build production capacity of 3300 MW of renewable energy for 2008, of which 1422 MW through wind energy. The program seeks to produce 10% of Brazilian electricity through renewable sources.

South Africa has a proposed station situated on the West Coast north of the Olifants River mouth near the town of Koekenaap, east of Vredendal in the Western Cape province. The station is proposed to have a total output of 100 MW although there are negotiations to double this capacity. The plant could be operational by 2010.

France has announced a target of 12,500 MW installed by 2010, though their installation trends over the past few years suggest they'll fall well short of their goal.

Canada experienced rapid growth of wind capacity between 2000 and 2006, with total installed capacity increasing from 137 MW to 1,451 MW, and showing an annual growth rate of 38%.[69] Particularly rapid growth was seen in 2006, with total capacity doubling from the 684 MW at end-2005.[70] This growth was fed by measures including installation targets, economic incentives and political support. For example, the Ontario government announced that it will introduce a feed-in tariff for wind power, referred to as 'Standard Offer Contracts', which may boost the wind industry across the province.[71] In Quebec, the provincially owned electric utility plans to purchase an additional 2000 MW by 2013.[72]. By 2025, Canada will reach its capacity of 55,000 MW of wind energy, or 20% of the country's energy needs.


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