Keeping mature technology in top shape

Proper repair, maintenance and overhaul are essential to keep hydro installations running

By Morand Fachot

With the share of RE (renewable energy) sources in the global energy generation mix predicted to grow considerably in coming decades, hydropower will continue to make a major contribution to clean energy production. Cost estimates for hydropower installations still tend to focus on equipment and construction expenditure. However, long-term lifecycles and the need to improve efficiency require extensive MRO (maintenance, repair and operations/overhaul) work that carries additional significant cost implications.

High efficiency turbine generators replaced four 90-year-old Francis turbines in the Cheoah refurbishment project in North Carolina, USA
High efficiency turbine generators replaced four 90-year-old Francis turbines in the Cheoah refurbishment project in North Carolina, USA

Fountain of youth for old-timers

Fountain of youth for old-timers Hydropower, the oldest and most reliable source of RE, accounted for 16% of global electricity generation in 2012, more than three times that of all other renewables combined, according to the IEA's World Energy Outlook 2014. Hydropower requires significant initial investment. Major civil engineering work, powerful electricity generating equipment and extensive transmission and distribution infrastructure are very costly. This means that hydropower plants are designed and built to last decades, if not a full century, and to be upgraded over their lifetime.

Such specifications, coupled with typically harsh operating environments, mean that MRO (maintenance, repair and operations/overhaul) represents a significant share of overall expenditure on hydropower. However, the returns on investment are highly cost-effective for the following reasons:

  • If initial outlays are significant, subsequent running costs are low, resulting in low-cost rates for hydropower electricity compared to those produced from other sources, so keeping plants running over many decades makes sense
  • Hydropower installations are complex systems operating under challenging environmental conditions. To ensure peak plant performance and prevent catastrophic failures, which can result in casualties and bring installations to a standstill for lengthy periods, regular and proactive maintenance is required to assess wear and tear accurately and carry out necessary maintenance and repairs on time
  • The need to increase generation from RE sources means that gradually modernizing and upgrading existing hydropower installations to augment capacity and improve efficiency – even in relatively tiny amounts – through the incorporation of up-to-date technology and know-how can result in significant returns on investments, given the generating capacity of such installations.

Dam if you do, but dam if you don't!

The MRO of hydropower installations can be very costly and lengthy. In addition to work on hydraulic turbine parts such as shafts, bearings or blades it may include reinforcing / refurbishing / replacing civil engineering and mechanical elements including worn runners and intake structures and gates and providing improved hydrodynamic flows.

The duration and cost of hydropower refurbishing projects are clearly illustrated in a report on 19 North American rehabilitation projects on plants ranging from 5,45 MW to 2 457,3 MW, at a total cost of nearly USD 3,5 billion.

Work carried out included two facilities that went on line in 1898 and 1899…

The largest project, the overhaul of Hydro-Québec’s fifth-largest power station, Beauharnois (1 853 MW), the first units of which went on line 82 years ago, was started in 1994 to extend the generating station's service life. It is scheduled to run until 2020 and to cost some USD 1,3 billion. Jean-Paul Rigg, TC 4 Chairman and former General Manager of the Beauharnois hydropower station for seven years, outlined the extent of the station's refurbishment for e-tech: "Work involves overhauling the 36 generating units, their auxiliary services, constructing two new SF6 gas-insulated substations, changing the power transformers, rearranging the 120 kV switchyard and rehabilitating the power plant building. It also involves carrying out major civil engineering work on the dam which is subject to concrete expansion, the result of alkali-aggregate reaction and construction of a fish ladder for eels."

MRO work is being carried out in hydropower installations in many countries and on all continents, from Brazil to China, from the German-Swiss border to Norway.

If the cost of MRO work for hydropower installations may seem prohibitive it presents the major benefits of increasing capacity and reducing operating costs. Furthermore, delaying or neglecting to carry out necessary MRO work may have serious adverse consequences such as failure or a lengthy and costly plant closure being required for extensive and expensive repairs. The negative effects are compounded by loss of income during this period.

IEC central to hydropower

MRO Standards developed by IEC TC 4: Hydraulic turbines, have been central to MRO work on hydraulic installations for a long time. TC 4 MRO-related International Standards include:

IEC 60545:1976, Guide for commissioning, operation and maintenance of hydraulic turbines, that "establishes suitable procedures for commissioning, operating and maintaining hydraulic turbines and associated equipment". IEC 60545 "applies to impulse and reaction turbines of all types, and especially to large turbines directly coupled to electric generators".

IEC 60805:1985, Guide for commissioning, operation and maintenance of storage pumps and of pump-turbines operating as pumps. This Standard "applies to storage pumps and reversible pump-turbines of all types, especially to large units coupled to electrical motor-generators".

IEC 62256:2008, Hydraulic turbines, storage pumps and pump-turbines – Rehabilitation and performance improvement. IEC 62256 "provides assistance in identifying, evaluating and executing rehabilitation and performance improvement projects for hydraulic turbines, storage pumps and pump-turbines of all sizes and of the following types: Francis, Kaplan, Propeller, Pelton (turbines only) and Bulb".

IEC 62364:2013, Hydraulic machines – Guide for dealing with hydro-abrasive erosion in Kaplan, Francis and Pelton turbines. This Standard "serves to present data on particle abrasion rates on several combinations of water quality, operating conditions, component materials, and component properties collected from a variety of hydro sites; develop guidelines for the methods of minimizing particle abrasion by modifications to hydraulic design for clean water".

Work is ongoing on these Standards.

Keeping hydroelectric plants running over many decades in peak condition and improving their capacity through timely and comprehensive MRO will help meet the world's growing hunger for electricity and make a significant contribution to a reduction in harmful emissions. TC 4 work on MRO-related International Standards provides the necessary basis for this.

Gallery
High efficiency turbine generators replaced four 90-year-old Francis turbines in the Cheoah refurbishment project in North Carolina, USA High efficiency turbine generators replaced four 90-year-old Francis turbines in the Cheoah refurbishment project in North Carolina, USA
Kaplan turbine at Wanapum hydro power plant, USA (Photo: Voith) Kaplan turbine at Wanapum hydro power plant, USA (Photo: Voith)
Poor maintenance was a major factor in the 2009 accident at the Sayano Shushenkaya hydro plant in Siberia, in which 75 died Poor maintenance was a major factor in the 2009 accident at the Sayano Shushenkaya hydro plant in Siberia, in which 75 died