Electric Retrofitting of Existing Dams

Retrofitting describes the addition or expansion of an existing dam with hydroelectric power generation capabilities. According to ICOLD less than 20% of world’s large dams are used for hydroelectric generation. Compared to the construction of a new dam, and under certain conditions, retrofitting could pose a cost-effective way to increase electricity production. Impacts on the environment are less severe as most substantial impacts have already been caused. The mere addition of turbines and other electromechanical equipment usually requires little additional construction and limited degradation of an already disturbed waterway. Wide public support is thus more likely as well. But in the search for such potentials for additional power generation it always has to be asked why these uses have not been obvious before, in particular, taken during the construction of the plant.

Reasons for Retrofitting

Dams with their reservoirs are built for many primary purposes, particularly for irrigation, but also for drinking water supply or flood protection. Under certain conditions, it may make economic sense to use these plants to generate electricity.

Reasons that can favor retrofitting include:

New operation purpose: Dams could play a major role as storage for electricity generated from variable renewable energies (wind, solar, etc.). Economic benefits of this purpose were not considered adequately when assessing the viability in the first place.

• Mitigation: As climate change has become a major issue, electricity generated from hydropower can be a means to reach emission reduction goals. There are newly created direct financial incentives like the Clean Development Mechanism (CDM) specified in the Kyoto protocol that allow hydropower schemes to be credited as CO2-offset in carbon markets[1].
  
• Need for power generation: As some reservoirs are prone to sedimentation and contamination due to extensive use of fertilizers upstream, energy could also directly be used for the cleaning of the dam (see Hartbeespoort dam in R. South Africa[2]).
  

Changed political priorities: With respect to altered political constellations, economic development status or other factors the policy priorities might have changed.

When assessing the feasibility of Retrofitting - and given those benefits - the question arises, why the deployment of hydroelectric generation capabilities was not already considered at the time of dam construction. Hydropower technology has been technically mature and widely known for a long time. Possible reasons for exclusion of hydropower, but which are subjected to change over time and thus could not be accurate anymore, can include:

High investment costs: Cost-intensive technical equipment or lack of both public and private investors (and interests) impeded the installation of additional turbine generators. However, investment costs per unit of installed capacity have fallen over time, i.e. because of technological innovation. Also, energy demand and the willingness to pay might have risen over time. The deployment of hydroelectric generation capabilities could thereby have become economically viable.

Remote area: The dam was constructed in a remote area with little population or low grid infrastructure and thus no way of using the generated electricity in a reasonable way. Over time, however, more people could have settled in the vicinity of the dam site and thus create a sufficiently high electricity demand. Also, it is possible that the electricity grid got extended and is now within reach of the dam site.

Institutional reasons: Dams are normally planned by special-purpose institutions (i.e. the relevant authorities in charge of agriculture, irrigation, water management, river navigation, flood protection, etc.). Multipurpose schemes were not considered because of legislation, certain prioritizations or limited institutional capacity. Institutional changes and alterations of policy priorities could now favor retrofitting.

  

Challenges and Risks

Retrofitted dams technically are always multipurpose dams and share the same set of challenges (->WIKI-LINK: MULTIPURPOSE).  One main challenge can be the priority setting for water allocation, e.g. if there is a high energy demand and therefore claims are voiced for higher water releases. In case that previous water release patterns are retained, the main challenge will be the high capital costs of the turbines and the question how to unlock investment sources. Further key issues for retrofitting are the grid integration and the harmonisation with a given tarif system.

During operation a main challenge are the revenues, their allocation and the question who will benefit. Those economic aspects carefully need to be negotiated during the planning process already. A further big challenge during operation is, that there is an economic motivation to reallocate water resources towards the purpose with the highest marginal revenue. For a dam originally managed for agricultural irrigation, e.g., there might be moments where peak demand of electricity will encourage discharge of water although not scheduled for irrigation purposes in that exact moment.

 

To minimize risks in the context of a retrofitting project the general requirements of transparent and democratic processes need to be respected, involving all relevant public and private stakeholders. The diverse demands of various sectors at the water resources thoroughly have to be analysed and incorporated into the consideration and weighting process. Sound economic concepts need to be developed beforehand, including cost-benefit-analysis to allocate investment costs and returns, gains from power purchase, infrastructure maintenance costs etc. Responsibilities, accountability and the distribution of gains and duties have to be determined in detailed and binding contractual agreements. 

 

Technical Requirements and Available Technology

 The main technical conditions for the retrofitting of turbines are:

•  a sufficient slope
  
• a drain that is either regular or controlled by demand from electricity generation
  
• the possibility of a low cost connection to the network or in smaller plants a local demand for electricity, which can be operated with a local network.
  
  

In order to operate turbines to produce electricity, the usable head and available flow have to be sufficiently high. A flow duration diagram can be used to calculate additional hydropower potential. Good data on annual flows for a potential dam might be already available because the water level and discharge of a dam was recorded over the years.

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Example: Jebel Aulia dam, Sudan

Andritz Hydro, together with the Sudanese National Electricity Corporation (NEC), upgraded Jebel Aulia dam[1], located on the White Nile near Khartoum. The dam was originally built in the 1930s for irrigation and flood control. Andritz provided its Hydromatrix technology, a modular system with turbine generators with a capacity of around 0.5 MW each. Jebel Aulia features 50 discharge openings in total, 40 of which were retrofitted with Andritz turbines. The dam was thereby converted into a multi-purpose scheme that now allows hydroelectric generation of up to 30.4 MW.

To be suitable for retrofitting with Andritz technology it had to fulfil certain requirements, inter alia:

The dam had to withstand the changed hydrostatic loads

The minimum width of an existing discharge opening had to be at least 2.2m

The construction had to allow a crane to be installed in order to hoist the turbines to not hinder flow during flood release

 

Available technology:

Andritz Hydromatrix® and Andritz Straflomatrix®: Modular system for the retrofitting of various dam designs.

Turbine generators with ~0.2-1.0 MW per Unit.

e.g. Retrofit of Jebel Aulia Dam, Sudan: 80 units, totaling in 30.4 MW

Voith StreamDiver®: Modular system for the retrofitting of various dam designs

Turbine generators with ~0.5 MW per Unit.

• < >: In-pipe system that can be installed into drinking water pipes[2]. It generates <<0.1 MW per unit through extraction of head pressure from the pipe. Depending on the available pressure, a series of units can be deployed (see Installment in Portland[3]).

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Costs

 The retrofit of hydropower units at a dam not only requires the installation of turbines and generators, but also some more complex additions and modifications, e.g.:

Improved erosion control and if necessary pre-dams to reduce the introduction of solids.

For some watercourses well development and sand management are required, with rising investment and operating costs.

To feed the power into the grid transmission lines are essential.

Moreover, multi-purpose facility planning often is attached to difficult and extensive negotiations to find the right balance of interest between divergent uses like irrigation, flood control and energy generation. This is particularly difficult since not all services can be put on the bill like environmental minimum flows.

 

Retrofitting costs can include:

Transactional costs for multipurpose operation

Licensing; Water-use (Payment per Volume or per Volume*Pressure?)

Environmental and Social

Civil engineering: Construction of new buildings

Hydroelectric equipment: Generators, turbines etc.

Grid connection

Operation & Maintenance

 

Examples of German development cooperation

  

 

Literature and sources:

Potenzialstudie „Ausbaupotentiale Wasserkraft in Bayern“, Bericht aus Sicht der beiden großen Betreiber von Wasserkraftanlagen in Bayern E.ON Wasserkraft GmbH, Landshut Bayerische Elektrizitätswerke GmbH

Prioritizing Mini-Hydroelectric Development At Existing Dams in Massachusetts

Potential Hydroelectric Development at Existing Federal Facilities

Retrofitting Hydropower To South African Dams; Arno Ottermann and Bo Barta

„Wie können Möglichkeiten für Wasserkraftgewinnung auf der Grundlage bestehender Stauanlagen gefunden werden?“, J.H. Lottmann 2012 (DMS)

Retrofit-Ausschreibung in Indonesien (Zeitungsartikel): http://www.thejakartapost.com/news/2014/11/29/govt-offer-33-hydropower-project-investors.html