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Technical challenges in small hydropower in Africa

Hydropower challenges

Huge potential exists for hydropower development in Africa. However, developers face many challenges throughout the lifecycle of a hydropower project.


Typically, there is a lack of data, such as hydrological, topographical and geological. It is also difficult to source reliable data. In many countries flow data stopped during the 1970s and 80s due to political instability or war.

Other challenges include:

  • language
  • geotechnical and geology
  • interconnections facility
  • logistics and accessibility
  • licenses and PPAs
  • specialist engineering
  • funding at the various lifecycle stages

These challenges can be overcome with proper planning and a project team that has leading expertise and local experience.

Hydrology


One could assume, as for many developed countries, that the information is out there, and could easily be researched and downloaded from the internet. However, this is not the case in many African countries. Data is often old, dating back to colonial ages. Another typical challenge is the reliability of such data. Even when data is paid for, it needs to be verified. For example, the flow data made available from a gauging station would typically be derived from a station comprising of only gauge plates in a river section without any controlled structure (e.g. gauging weirs) and using a rating curve of more than 20 years old. Over such period, typically the river banks and river bed profile would have changed which would have affected the rating curve leading to inaccurate records being provided (figure 1).

Gauge station

Figure 1: Typical gauge station, where one can see the bank having been washed away, yet results are still being “estimated” by the gauge reader and recorded as true

In this case, it is important to carry out a few spot flow measurements in the river at the intake to confirm the flow and calibrate the rain-runoff model.

There is generally a lack of quality control and the data is often unverified. Going back to the earlier example, the rating curve at gauge stations is not usually verified or updated regularly. Also, typically, only average daily flow values are available, whilst the instantaneous daily peak values are not recorded. This is a challenge in steep rivers as the daily peak from an afternoon cloud burst would not be picked up. This can cause a risk mainly during construction as such could easily flood the works. In small hydropower projects, where a diversion weir of not more than 5 m is being constructed, the project cannot afford to have complicated and expensive river diversion strategies.

It is also rare to find concurrent rainfall and gauged flow data within a river catchment having a surface area of less than 500 km2. Furthermore, in many countries flow data stopped in the 1970s or 80s, due to political instability or war. Thus, engineers need to consider the data carefully before using it.

Mass plot curve

Figure 2: Typical mass plot curve showing periods of missing information

Where possible, engineers should use quality assured data from relevant local or national department, but this usually exists only for major rivers and in certain countries. Localised but reliable information, obtained from the local authorities, private companies and large establishments should also be sourced, such as rainfall data and other climatological aspects. Reconnaissance visits are required to better understand characteristics such as runoff coefficients and other catchment response characteristics, to improve the understanding of the site, and hence the accuracy of the hydrological model. It is highly recommended that only established ‘tried and tested’ modelling techniques be used and designers should abstain from using empirical models/formulas developed for other catchments or for other countries.

Hydrology is the most important component of any hydropower project. Long term flow sequences are hence required to minimise the risks and to be in a better position to determine the applicable flow rates to be used in the project options analysis. Hydrological analysis is also needed for the design and operation of plant and the prediction of the annual outputs with a certain level of assurance. For sites with multipurpose use or with storage capacity, yield modelling is also required using a multi-level reliability approach for each use. Flood hydrographs and flood levels are required for the design of the infrastructure. Often, information about flood levels is available from the local village elders, which should not be ignored.

Geotechnical and geological


Geological maps are often only available on a large scale, which does not provide sufficient details for the specific site. It is therefore important that an engineering geologist is part of the reconnaissance team to identify any significant geological features which may either affect the design or affect the construction or operation risks. Often, localised slope stability and difficult founding conditions for the various project infrastructure components are problematic (figure 3). Being small hydro, the costs of the associated infrastructure components, such as the access road to the power station, could easily have major costs implications and often requires innovative design solutions to keep the project within budget.

Slope stability issues

Figure 3: Typical slope stability issues which could become problematic as well as steep valleys with difficult access.

Geotechnical field investigations are also often challenging due to costs and unavailability of excavators for test pitting exercises. Often, one is required to dig test pits by hand, but this is then limited to no more than 2 m for safety reasons. Furthermore, the costs of drilling is often expensive due to difficulties with access, which can require up to 5 days just to get the drill rig on the site as it has to be carried by hand (> 300 kg for the smallest component).

Another challenge is finding the appropriate material for construction, including concrete aggregates. Commercial quarries are not often available and locals would typically break aggregate by hand for their own use. However, this is not possible when say 1 000 m3 of concrete aggregate of various sizes is required, hence requiring the contractor to provide for a mobile crusher which adds to the costs. The availability of reliable local laboratory for testing of the material is also challenging and often the material needs to be sent to laboratories in the main cities which are generally far away.

Interconnections


The typical challenges experienced with regards to interconnections include stability of the line, load shedding, high lightning intensity, poor quality equipment being used along the transmission lines and old infrastructure. Even with new infrastructure built, the lack of quality control during the implementation stage can cause problems which would impact on the plant availability and hence ability to generate. Not all countries offer “take or pay” power purchase agreements (PPA).

It can be difficult to obtain the relevant information/parameters for the determination of the electrical protection, and often the grading of such protection is inappropriate. Redundancies of protection equipment, even at substations, are often a luxury and all these aspects make the accurate sizing and specifying of the electrical equipment for the plant challenging.

A common challenge at existing substation where the plant would interconnect is when no provision has been made for expansion of the substation, and houses have been constructed right next door.

Logistics and accessibility


Road access is generally poor, requiring additional cost for creating access to get the construction plant and electro-mechanical equipment to the site.

Bridges along the way may not be able to take the size and load of the turbine or generator, hence requiring generating plant to be brought to site in smaller components to be erected on site, as opposed to pre-assembly in workshop conditions. This is generally critical for the generator due to dust on site and the lack of adequate tools and equipment requiring improvisations.

Sourcing pipes can also be a problem across Africa. In some countries, a ‘simple’ 1 metre diameter pipe needs to be imported as it is not commonly available. To ensure quality, it may be necessary to import all materials but this has a significant cost impact on the capital expenditure (capex) which cascades to lower returns.

A solution which a Nigerian contractor has been doing is to use old containers, open on both sides and reinforced, as culverts / bridges to facilitate the access over streams as well as for river diversion in some instances (figure 4).

Containers as culverts

Figure 4: Containers as culverts

The difficulty of access and the lack of readily available material for the works affects the overall costing of the project.

Licenses and PPAs


In most developed countries the industry is well regulated, however, in most African countries, the lack of regulation can be a problem. A typical challenge is the determination of the reserve / environmental flows which is not regulated in many African countries. Such IFR, to be compliant to the IFC performance standards, require proper ecological baseline studies, which need to be carried out at various seasons (dry, rainy, etc.) before a quantitative flowrate is determined.

Another challenge is that in some countries the developer is required to have completed a feasibility study before being given the right to a site. In other countries, a site can be assigned to a developer as long as they have paid the relevant applicable fee, irrespective of their technical or financial capability to develop the scheme. Hence, one may identify a good site, but the rights are being held by someone else who wants a significant, and unrealistic in most cases, payment to hand over their site.

Good examples include Uganda and Kenya which have gone a long way in incorporating small hydropower in their regulations and this has encouraged the development of the countries’ small hydropower potential.

Standard PPA is not common throughout the continent although great progress is being made in East Africa. In some instances, the PPAs are in the local currencies which discourage foreign investments often only interested in hard currencies. Government securities are also not common which is required to make the PPA bankable.

Specialist engineering


The development of hydropower requires specialist engineering with multidisciplinary expertise. Typical fields include project management, contract administration, hydrology, geotechnical and engineering geology, environmental and social, civil, hydraulics, structural, electrical, hydro-mechanical, mechanical, corrosion protection, commissioning and dam safety. Often, such expertise is not available under one roof and causes complications at this development stage. A good hydropower lead engineer should have a good understanding of all the above skills to be able to put the pieces together.

Another important aspect which should not be ignored is the country experience of the team participating in the project. In most instances, the clients/developers are certainly not willing to pay the “school fees”.

Funding


Funding has always been an issue in the development of hydropower. At development stages, the funding amount is generally between 2.5 % to 5 % of the capital value of the scheme, depending on the size and including the field investigations. And this is before one even knows that the scheme is financially viable to the expected returns.

The large capital investment required with high interest during construction costs leads to a long term repayment over a 12 ~ 15 year period. For the associated risks (technical, country hydrological, etc.) most developers are not interested if the Internal Rate of Return (IRR) is less than 18%. Similarly, lenders are often not willing to fund more than 70% of the project capital value and require the developers to provide substantial guarantees.

To minimise the project risks, lenders sometimes impose an Engineering Procure Construct (EPC) conditions for the implementation process or another complex process with many gateway reviews. Although this could be justified to a certain extent, often small hydropower projects cannot afford these expenses.

Another common challenge is that often developers do not have sufficient funds to do a proper feasibility study. This then leads to a reduced chance of being able to develop the scheme, or even sell the rights to the site as one cannot determine the viability of the scheme. Typically developers try to cut the development cost as much as possible (mainly at feasibility level) as this is considered “risk money”, but this generally has a significant impact on risks and construction price at eventual implementation. It also sometimes leads to large claims from the contractors and runaway costs during implementation.

Although grant funding is sometimes available for feasibility studies, it generally requires the developer to contribute an equal amount of the grant funding to the project. Grant funding sometimes comes with strings attached.

Conclusion


The development of small hydropower projects in Africa is possible with good returns. However, even an experienced developer will need to go through many hurdles and learning curves before getting there. Each project is specific and should not be generalised.

A good technical team and sufficient funds for the development stage can certainly go a long way in minimising the project risks and ensuring that a project is properly designed at development stage. This can have a cascade effect onto the implementation costs, leading to improved returns.

This article was published in Energize, June 2015, and is republished here with permission.

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