Power Engineering Names Renewable Project of the Year

Best Renewable/Sustainable Projects

Tekeze Hydropower Project

The Tekeze Hydropower project in Ethiopia, located on the Tekeze River, a tributary of the Nile, is the Project of the Year for renewable/sustainable projects. The $350 million project, funded by the government of Ethiopia and owned by Ethiopian Electric Power Corp., adds 40 percent more electric capacity to the country and was the largest public works project in Ethiopia’s history at the time of construction. Due to the lack of natural resources and the cost of imported fuels, power generation in Ethiopia comes primarily from hydroelectric sources.

The Tekeze Hydropower project is the tallest arch dam in Africa at 188 meters. The 300 MW facility includes a double curvature concrete arch dam, a method of design that minimizes the amount of concrete used. It created a reservoir 70 kilometers in length. An underground powerhouse containing four 75 MW Francis Turbines sits 500 meters downstream of the dam and is fed by a 75-meter-high intake structure connected by a 500-meter-long concrete-lined power tunnel. A 230 kV double-circuit transmission line 105 kilometers long was constructed through mountainous terrain to connect to the Ethiopian national grid.

The project’s beginnings date back to 1995 when the Ethiopian Ministry of Water Resources conducted a study identifying the site as one of two preferred dam sites for hydropower development. MWH joined the project in 1998 and made modifications to an existing design for the dam, powerhouse and tunnel system, resulting in cost savings.

A multi-stage impoundment approach was implemented during construction, which allowed the river diversion to be closed in May 2007, nearly two years prior to dam completion. This allowed for more than 3 billion m3 of water to be retained, advancing generation by more than one full year. The value of the water captured via early impoundment was worth approximately $40 million. In addition to power generation, the Tekeze dam enables regulation of river flow, allowing downstream communities year-round access to the water supply.

A 10-year 2000m3/sec flood on Aug. 9, 2006 was an unexpected test for the dam. The dam proved its ability as a gravity structure and no damage was incurred to any of the permanent structures.

Local community infrastructure was improved as a result of the project, including construction of more than 40 kilometers of roads and installation of the first communications links from the area to the outside world. Also as a result of the project, education was improved in the area as the wife of the MWH chief design engineer spearheaded efforts to build a new school near the village of Seboko. The school was financed by contributions from engineers, contractors and staff working on the project, local residents and a supportive local government.

On-the-job training was also provided to locally-hired employees. Ethiopian Electric Power Corp. implemented programs to provide education and training to local workers. Programs included education to combat AIDS, malaria and other safety, health and welfare issues affecting the local community.

Honorable Mentions

Canoe Creek Hydroelectric Project

Canoe Creek Hydro is a 5.5 MW run-of-river hydroelectric facility on Vancouver Island that provides power to a remote community on the island and helping the island become less reliant on mainland power. The facility is owned and operated by the Tla-o-qui-aht First Nation and located in the heart of the Nation’s Tribal Parkland. The Barkley Project Group Ltd., along with Amnis Engineering and Hazelwood Construction One, worked with Vitaulic, a manufacturer of mechanical pipe joining solutions, to develop Canoe Creek. Construction started in May 2009 and ended in May 2010. The plant went into service in June.

Canoe Creek Hydro operates by diverting stream flow into a penstock at a high elevation – up to 84 percent grade – intake. This made construction a challenge, as did the facility’s location in the Pacific Rim Rainforest, where annual precipitation is amongst the heaviest in the world, particularly in the winter months when construction took place.

Constructing the 4-km-long penstock line in these conditions using welding techniques would have proven difficult. Instead of using mechanical welding on the penstock, the companies used mechanical couplings. In the field, the couplings proved advantageous in many ways. For example, couplings could be installed in any weather condition with no special requirements. Couplings also reduced the amount of excavation, bell holing and dewatering that would be common with welding.

Couplings also improved site safety. As the pipe was already on site, Hazelwood grooved and re-coated the pipe prior to sending it up the single-lane logging road for assembly. In addition, the replacement of welding with mechanical joints allowed for a reduction in the number of laborers required on the job site. Canoe Creek also employed local laborers.

Environmental benefits were also gained by replacing welded joints with mechanical joints. Welding one kilometer of straight-run 36-inch pipe produces about 40,338 kg of CO2 emissions using a diesel-powered machine and 9,463 kg of CO2 emissions using an electric-powered machine. Grooving and coupling that same run of pipe produces 62 kg of CO2 emissions. The use of couplings also reduced the amount of x-raying required on site, reducing radiation emission. PM, CO2 and radiation were reduced, as well as electrical energy use.

Biogas facility owned by PurposeEnergy, Inc.

This biogas facility project at the Magic Hat Brewery in South Burlington, Vt. allows the owner, PurposeEnergy Inc., to use organic waste streams and generate biogas. The biogas is then used by the brewery’s steam boilers and/or PurposeEnergy’s cogeneration plant. In mid-2008, Pizzagalli Construction Co. was selected as the design/build partner for this $3.4 million project at New England’s largest craft brewery. This brewery waste recovery system was developed by CEO and founder of Purpose Energy, Eric Fitch.

Underground process piping, stone aggregate piling for the digester, structural excavation and backfill and all of the concrete work began in December 2009. A 1,600 square foot mechanical building was built and a digester tank was installed. The piping process was completed by May 2010 and the facility began operations in June 2010.

PurposeEnergy’s Biphase Orbicular Biodigester was designed for brewery by-products and enables the conversion of high solids content brewery waste into carbon neutral, renewable biogas. This system is also designed to utilize the waste heat from the generator’s exhaust, coolant and engine oil to heat the digester and preheat the water used in the brewing process.

The PurposeEnergy project has brought many benefits to the facility and environment. By diverting the waste stream created during the brewing process, the brewery’s operating costs have been reduced as Magic Hat Brewery no longer needs to pay for waste treatment surcharges, thereby reducing traffic, noise and air pollution that would result from the transportation of the waste. In addition, the use of this technology creates a clean, carbon neutral energy source that decreases the effects of greenhouse gases on the environment.

To read which coal-fired, gas-fired and nuclear projects of the year Power Engineering named, read the full article here.

View the original article here

Fossil Fuel Power Plants: how Electricity is Generated.

Fossil fuel power plants produce the electricity which is the lifeblood of the developed nation, and we all rely heavily on it in our daily lives. The majority of current power stations run on fossil fuels. While solar energy power stations are being developed around the world on commercial scales, it is true to say that over 70% of every developed nation?s energy comes from fossil fuel electricity generation. In Australia, over 90% of our electricity is sourced in this way.

Power stations supply the main energy grid with electricity on-demand; that is, the greater the demand the more the power stations churn out.

That means that the greater the demand for electricity, the larger the amount of coal, oil or gas the fossil fuel power station will be consuming. A clear explanation of how the power stations turn fossils into electricity is in order.

An iron bar is made of lots of tiny iron crystals. When all these crystals are aligned, the iron bar will produce a magnetic field. Compasses are tiny magnets that align with the earth?s magnetic field. Have a look at this simple experiment in which you can make your own compass. Early compasses were simply lumps of magnetic iron-rich rock called lodestone.

Why iron does this and many other metals cannot is due to the arrangement of electrons in the d-subshell of each atom. Discussion of that topic is beyond the scope of this website.

It turns out that the magnetic field of a bar magnet looks something like this:

Those lines around the magnet are the FORCE LINES; they make up the magnetic field. Those field lines are able to push free electrons around so that they align with the field lines.

If we make a coil of copper wire and push a magnet through it quickly the electrons will move in one direction and you will have a current. Copper is used because it conducts really well, but any metal can be used for the wire. The reverse is also true; if we push electricity through a copper coil, it will generate a magnetic field. That is called an electromagnet. Electromagnets usually have an iron core to improve the magnetic field.

Now if we take one electromagnet and spin it inside another coil, the field from the electromagnet will create a current flow in the second coil. This is because the magnetic field pushes the electrons in the second wire coil.

Just like any other electrical device, the turbine needs to be connected to a circuit to allow electrons to flow in a loop. The electricity grid that the turbine is connected to is one enormous loop.

Now we have a spinning turbine causing electrons to be pushed out into the loop with some force, the force given to them by the magnetic field. The faster they are going the more energy they have and so the more work they can do for us in our homes.

This is where the fossil fuels come into the equation. Energy is needed to turn the turbine, and that energy needs to be harvested from somewhere. Possibilities include wind, falling water, waves, or steam. Traditional power stations use steam.

The coal (or oil or gas) is burned in a furnace. The furnace heats water in a boiler. This generates super heated steam that turns turbines. The steam is then cooled in cooling towers and condensed back into water to be returned to the boiler, reducing heat loss as much as possible. Some steam has to be released in the cooling process; that?s the source of those big white clouds coming out of the power station cooling towers. Here?s a picture of the process:

The exhaust gases are also used to heat the boiler chamber before being released via the chimney stack. This is where the environmental nasties such as CO2, NO, SO2 and ash, called fly ash, are released into the air.

The amount of coal going into the boiler, and therefore the amount of Carbon Dioxide and other gases being emitted from this fossil fuel power, is determined by our actions. We can reduce the amount of pollution from the power stations by using less electricity.

While we are still operating the majority of our power stations as fossil fuel power plants this is crucial; lower energy demands mean less pollution.

Return from Fossil Fuel Power Plants to Fossil Future or return to the Green Planet home page for more Solar Power Facts.

View the original article here