India is ranked fifth in the world in terms of exploitable hydropower potential, but only 20 per cent of its potential has been developed. New Delhi aims to increase hydro’s share of national power output from 26 per cent to 40 per cent. Small hydro has a big role to play, writes Penny Hitchin.
Penny Hitchin, UK
Hydro is one of power-hungry India’s abundant and under-utilized resources. Only 20 per cent of its huge 150 GW of exploitable hydropower potential, fifth largest in the world, has so far been harnessed, although the government wants to see greater development of hydro generation. Its advantages include its technological maturity, ease of maintenance, reliability and low operating costs. Its main drawback is its high capital costs.
Befitting a country whose ‘Father of the Nation’ national icon Mahatma Gandhi was a devout advocate of economic self-reliance, small-scale hydro is going to play its part. This should notably improve both the energy and economic footprints of rural, remote and inaccessible areas.
Small hydro projects in India require specific equipment characterized by simplicity, reliability and easy maintenance Source: Andritz Hydro
In India, hydropower projects with a capacity up to 25 MW, categorized as small hydropower (SHP) projects, come under the auspices of the Ministry of New and Renewable Energy (MNRE).
MNRE’s database of potential sites for small hydro identifies 5718 sites, with a combined capacity of 15 384 MW, for SHP projects. The MNRE wants a combination of public, private, grid-connected and off-grid projects to double installed SHP capacity to 6000 MW by the end of 2017.
Hallmarks of SHP design: simplE, reliable, easy to maintain
Scaling down large hydropower installations does not, however, make a SHP project: specific equipment is needed, characterized by simplicity, reliability and easy maintenance by non-specialists. The focus of the MNRE programme is to lower the cost of equipment, increase its reliability and establish projects that give the maximum advantage in terms of capacity utilization.
India has varied topography including mountains, deserts, fertile plains, rainforests and temperate coasts. Summer monsoons between June and October provide most of its rainfall. Each hydro project must be purpose designed for the site where it will be constructed.
If a scheme is to generate throughout the year, sufficient flow must be available whatever the season. The ‘head’ is the vertical height that the water falls on the available section of the waterway. Hilly areas where water plunges across the contours down steep descents offer ‘high head’, while rivers and canals with small gradients need ‘low head’ designs.
In hills and mountains, streams rushing down narrow, steep-sided valleys are suitable for medium and high head projects using relatively small volumes of water. These are normally ‘run of river’ type with a small diversion constructed to divert a portion of the flow. The diversion takes water from the stream or river by diverting it through an intake at a weir.
The diverted water passes through a settling tank or ‘forebay’ where it slows down and suspended particles settle out. The forebay is usually protected by an arrangement of metal bars (trash rack) that filter out waterborne debris. A pressure pipe, or ‘penstock’, takes the water from the forebay to the turbine, which is enclosed in the powerhouse together with the generator and control equipment. The water discharges down a ‘tailrace’ back into the river
In the plains, irrigation canals with assured discharges often have shallow falls along their route suitable for installing small low head hydro projects (the water drives a turbine or waterwheel placed in the water course). SHP projects can be constructed just downstream of a dam or barrage, taking advantage of the difference in the water level between the reservoir and its downstream course.
Historically SHP installations have been expensive to build but cheap to run by trained members of the local community. The development of smaller, lighter and more efficient higher speed turbine equipment, the lower cost of electronic speed and load control systems, and inexpensive plastic penstock pipes are now bringing down the capital costs.
Harnessing SHP to micro-grids to transform life in remote mountain areas
Proximity (or capital investment) is required if the scheme is to connect to the transmission grid. Over half of India’s rural households are off-grid, something that the government’s ‘Power for All by 2012’ policy is intended to address.
In remote areas decentralized distributed generation (DDG) or smaller micro-grids may be able to facilitate this. A micro-grid is a collection of small generators for a group of users in close proximity. SHPs are particularly good for micro-grids: a number of streams can be harnessed to produce electricity that can be used to electrify areas away from the utility grid.
The SHP plants produce cheap and reliable power that can be distributed over the local area by a micro-grid or mini-grid. Examples of where this would be valuable can be found in the state of Uttarakhand, in the foothills of the Himalayas, where about 63 per cent of the population lives in rural areas, in small villages in dense, remote forest where laying grid power lines is rendered impossible by forest laws and high costs.
In the Bageshwar district of Uttarakhand, nine SHPs run in isolated operating mode for only eight hours per day (wasting 16 hours of energy daily) with a very low load factor. A recent case study (‘Design of Mini Grid for SHP Plants’ by S.N. Singh, M.P. Sharma & A.Singh) designed a mini-grid to improve the load factor of the SHPs and supply power locally.
The mini-grid connected the SHPs with each other and with the nearby 33 kV grid substation (9 km, 15 km and 17 km from the nearest SHPs). The electrical engineers analyzed various system layouts and transmission line routing and found that an optimization using the shortest line length gave a break even point (BEP) of 6.5 years (based on an annual interest rate of 11 per cent).
The model showed that implementing this mini-grid design would improve the load factor and enable local consumers to have electricity around the clock. The availability of power would also open up a range of activities such as grinding, wood carving, welding, carpentry, repair of electrical/electronic devices, as well as the use of computers that could transform residents’ economic prospects.
Measures to encourage SHP
‘Unleashing the Potential of Renewable Energy in India’, a World Bank report published in February of this year, identifies SHP as one of the least expensive and most attractive forms of renewable energy. It uses established and locally made technology, and has maximum power production in the summer months, matching seasonal demand for electricity.
However, development has been hampered by Indian bureaucracy, which has earned a reputation as ‘the most stifling in the world’. Long delays in getting clearances and acquiring access to infrastructure, lack of clear policy for private sector participation in some states, and issues associated with land acquisition are all holding back development of SHP and other renewable energy.
More than 60 per cent of project cycle time in SHP projects is spent getting a raft of government permissions including wildlife, fisheries, panchayat (local councils), irrigation, public health, revenue department, pollution control board, industrial licences, work permits, approval for interconnection and so on. It takes between four and eight years from conception to commissioning – at least double the time taken in neighbouring Sri Lanka. Such a long cycle commissioning timeline is routine practice even though the state agencies project an average time period of just six months for obtaining all clearances.
Based on discussions with stakeholders, PricewaterhouseCoopers compiled a project allocation and development cycle for a SHP project in the Himachal Pradesh showing areas where potential problems and issues come up in project development and commissioning. It shows that projects must negotiate as many as 20 stages, each raising the risk of significant delay.
The World Bank report says that SHP is India’s most economically viable form of renewable technology, with an average economic cost of 3.56 rupees/kWh ($0.08/kWh), which is comparable with the thermal generation that provides the majority of the country’s electricity supply. About 3 GW of SHP is economically feasible, when the avoided cost of coal-based generation of 3.08 rupees/kWh is considered.
Although the government, through MNRE, says that encouraging development of SHP is a key aim, Indian renewable energy development lacks an integrated national economic perspective and has been largely driven by uncoordinated state policies. Furthermore, the states with the richest renewable energy resources lag farthest in development.
The northern states of Himachal Pradesh, Jammu and Kashmir and Uttarakhand, all in the Himalayan foothills, possess two thirds of India’s SHP resources, combined with the lowest generation costs. Yet resource utilization is less than 20 per cent and their combined installed capacity is less than that of Andhra Pradesh and Karnataka combined.
As the World Bank Report advises, “raising the utilization rate requires immediate attention”. It advocates development of single window clearance for all renewable projects, promoting innovative approaches, a competitive bidding process, and providing long-term funding options for producers.
During the 1990s most SHP developments were public sector projects. In the last ten years, private projects have come to the fore. MNRE reports that 23 states have policies for setting up commercial SHP projects through private sector participation. If the bureaucracy can be streamlined, then perhaps private investment can rapidly fuel development of India’s SHP sector, bringing energy and economic opportunity to communities which currently lack both.
Power Engineering International Archives
View Power Generation Articles on PennEnergy.com