Microlight hydro turbine may challenge the conventional idea of big dams

Microlight hydro turbine may challenge the conventional idea of big dams

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micro-hydel power projects

Times have turned to micro-hydel power projects — ones that generate 5-100 KW electricity using the natural flow of water.

Big dams generate power when water is released from their reservoir and turns the blades of turbines (machines that transform rotational energy into electricity).

Whereas micro-hydel projects use the perennial flow of the river to run miniature turbines and generate electricity.

Construction

Construction details of a microhydro plant are site-specific. Sometimes an existing mill-pond or other artificial reservoir is available and can be adapted for power production.

In general, microhydro systems are made up of a number of components. The most important include the intake where water is diverted from the natural stream, river, or perhaps a waterfall.

An intake structure such as a catch box 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.

The intake then tunnels water through a pipeline (penstock) to the powerhouse building containing a turbine. In mountainous areas, access to the route of the penstock may provide considerable challenges.

If the water source and turbine are far apart, the construction of the penstock may be the largest part of the costs of construction. 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.

Usually microhydro installations do not have a dam and reservoir, like large hydroelectric plants have, relying on a minimal flow of water to be available year-round.

Head and flow characteristics

Microhydro systems are typically set up in areas capable of producing up to 100 kilowatts of electricity. This can be enough to power a home or small business facility. This production range is calculated in terms of “head” and “flow”.

The higher each of these are, the more power available. Hydraulic head is the pressure measurement of water falling in a pipe expressed as a function of the vertical distance the water falls. This change in elevation is usually measured in feet or meters.

A drop of at least 2 feet is required or the system may not be feasible. When quantifying head, both gross and net head must be considered. Gross head approximates power accessibility through the vertical distance measurement alone whereas net head subtracts pressure lost due to friction in piping from the gross head.

“Flow” is the actual quantity of water falling from a site and is usually measured in gallons per minute, cubic feet per second, or liters per second. Low flow/high head installations in steep terrain have significant pipe costs.

A long penstock starts with low pressure pipe at the top and progressively higher pressure pipe closer to the turbine in order to reduce pipe costs.

Kamal Chandra Saikia, the founder-managing director of the Assam Micro Hydel Power Project Ltd, is taking the technology a step further with his Microlight Propeller Hydro Turbine.

The retired senior engineer from the irrigation division of the Government of Assam has designed a turbine that works well in low-flowing rivers, characteristic of Assam.

The ones generally used in micro hydel projects work only in high-flowing rivers. But Saikia’s small turbine can generate 6-8 KW of power from low-flowing rivers as it has a static head of just one metre in height.

The innovation is not only suited to the rivers of Assam, it’s also cost-effective. Electricity produced using the turbine costs Rs 4-4.5 per unit as against Rs 8 per unit using traditional turbines.

Saikia’s innovation was first put to test in 2004. Today, the extremely lightweight prototype is ready for installation.

It will remove the region’s dependence on agencies like the National Thermal Power Corporation, the North-Eastern Electric Power Corporation Ltd, the National Hydroelectric Power Corporation and coal-based thermal units.

The Assam Power Distribution Company Limited (APDCL) has entered into an agreement with Saikia’s company under which the electricity his project generates will power a model village with over 50 houses.

Saikia’s hydro turbine was to be installed at Jankhona, the source of the river Bhogdoi (a tributary of the Brahmaputra) in Jorhat district, in the first week of June this year.

A survey was done and the location for the installation on the river was identified. However, it was delayed due to financial constraints.

The President of India had sanctioned Rs 10 lakh for the project in 2014. A further assistance of Rs 1.25 lakh was granted by the ministry of new and renewable energy in 2015 for the installation of the project.

Using these funds, Saikia developed a commercial model of the turbine, but is still Rs 80,000 short to see the project through.

Once the pilot project at Jankhona is carried out successfully, Saikia’s company plans to install 50 propeller turbines, each with 100 KW power generation capacity, on three rivers — Soraipani, Disoi and Jankhona (the name of a region as well as a river). Together, they will generate 5 MW power.

Manoj Goswami, a retired general manager of the APDCL (Jorhat circle), said Saikia’s turbine can challenge the very concept of big dams. He believes the power-generation capacity of Saikia’s project can be increased by making a few tweaks. “His success will not only be a boon for Jorhat, but for entire Assam and the country,” he said.

Powering through

The Microlight Hydro Propeller Turbine is 9% to 10% more efficient than conventional ones. Conventional dams block rivers and store excess water to time release the water through turbines for power generation.

The microlight turbine allows excess water to keep flowing overhead, enabling uninterrupted power generation. Its main feature is that it displaces overflowing water even during floods without the need to store excess water in a reservoir by blocking the river.

This reduces chances of the mini-dam collapsing due to sudden release of excess water, thereby protecting people living downstream.

Talking to FactorDaily at the proposed dam site at Nagajanka village in Jankhona area bordering Assam and Nagaland, Saikia said both sides of the river embankment must be consolidated to build a small dam of three meter height for installation of his turbine.

The prototype is expected to produce 100 KW with a three-metre head. With a five-metre static water head, the turbine can produce up to 300 KW of power.

“In the commercial model, I have used extremely lightweight aluminium instead of the preferred Teflon, which is both heavy and costly,” said Saikia.

“Commercial production of power using my turbine will pave the way for employment of village youth as turbine operators, technicians and chowkidars,” said Saikia.

“I have already signed an agreement with the Assam State Electricity Board (ASEB). Power from the turbine will be stored in ASEB’s Nagajanka power substation from where it will be distributed in Bongaon village,” he added.

Bongaon is located close to the river Soraikhati, the downstream name of river Jankhona.

Bongaon headman Moina Gogoi is thrilled about Saikia’s innovation. Loadshedding was a big problem in their village. Saikia’s microlight propeller hydro turbine will solve the problem, he said.

Image link: www.google.co.in

With inputs from : Factor Daily

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