Island paradise17 January 2018
Andrew Bird from Stantec explains how the island of Samoa in the Pacific Ocean has proven itself as a leader in small hydro and the global fight against climate change
Half-way between Hawaii and New Zealand in the vast Pacific Ocean rests the nation of Samoa. This island paradise has found itself at forefront of climate change – the first to feel the impacts, and as a necessary result, a world leader in renewable energy generation.
Over the years the country has invested heavily in hydropower generation, and is on track to being 100% renewable. The quest to reach this goal has faced many elements from resource restriction to funding issues but the most challenging obstacle being Mother Nature herself.
In December of 2012 Cyclone Evan caused widespread destruction across the islands resulting in over US$200M of damage. This cyclone and the 100-year flooding it brought devastated Samoa’s infrastructure, population and properties, including seriously damaging three of the Electric Power Corporation’s (EPC’s) hydropower stations, reducing their renewable energy generation capacity by 10%.
With a GDP of just over US$800M, the damage caused by Cyclone Evan was a significant expense to the Government of Samoa (GoS), one they couldn’t afford. Two years after the initial cyclone the GoS and EPC secured grant funding from the Asian Development Bank (ADB), New Zealand Government and European Union (EU) for the Power Sector Development and Rehabilitation Project (PSDRP). This grant included the rehabilitation of the three damaged hydro stations and construction of four new hydro stations.
The influx of funding to build four new stations means Samoa is on track to greater energy independence and less reliance on costly diesel fuel oil. Samoa recognises that while the country may have little impact on climate change, it is greatly affected by its consequences. Samoa is therefore leading the way and taking a pro-active approach to increasing their renewable energy generation and reducing their greenhouse gas emissions.
Stantec, is currently providing Owners Engineer services to EPC for the PSDRP, and in partnership is looking to maximise the hydropower generation potential of the schemes whilst providing additional resilience to the impacts of climate change, in particular extreme weather events such as flooding.
Power Sector Development and Rehabilitation Project
The PSDRP is split in to three main packages of work:
- The rehabilitation of the three Small Hydropower Projects (SHPs) damaged by Cyclone Evan, producing a total installed capacity of 4.69MW—the 1.74 MW Fale ole Fee plant (Pelton), the 1.05MW Alaoa plant (Turgo), and the 1.9MW Samasoni plant (Turgo).
- New hydropower plants in Upolu and Savai’i. The projects will build and connect to the existing grid the three new SHPs with a combined capacity of 0.81 MW—the 0.19 MW Fausaga Tafitoala plant on Upolu (Pelton), the 0.46 MW Tafitoala plant on Upolu (Pelton), and the 0.16 MW Faleata plant on Savai’I (Pelton).
- New hydropower plant at Fuluasou (Francis).
All the projects are run of the river schemes with some minimal storage 10,000 – 20,000m3. As noted above a range of size and types of machines have been used specific to the site characteristics.
The three hydropower schemes, Samasoni, Fale ole Fee and Alaoa, damaged during Cyclone Evan contributed a significant share of the hydropower installed capacity of Samoa. All three schemes also have storage so are utilised as peaking plants. Construction of the rehabilitation of these schemes started in early 2016 and is scheduled to be completed by the end of 2018.
Of all the schemes Samasoni was damaged the greatest - the headpond filled with flood debris, 40% of the main penstock washed away and the powerhouse was completely flooded resulting in significant damage to the turbines and generators.
One of the key focus areas for the rehabilitation project was further securing the schemes against future damage. The main point of weakness, for both damage and failure due to lack of maintenance, was the main penstock which ran predominately above ground through villages. The solution - install a buried glass reinforced plastic (GRP) penstock, the first GRP to be installed in the Pacific Islands, excluding Solomon Islands and Papua New Guinea. This has proven to be a great success. The villagers now have the benefit of the security and safety of a below ground pipe, as well as, significantly better access to their homes and crops. Additionally, local villagers were employed (approx. 50) gaining skills in pipeline installation and construction in addition to monetary benefits.
Like many rehabilitation projects the projects has faced challenges. For example sections of the Fale Ole Fee pipeline when finally exposed were in a worse condition than originally assumed and leaked significantly when pressurized. Some attempts were made to patch repair but this ended up being a losing battle. In most countries this would not cause a significant delay as you could source replacements relatively easily. However in the Pacific shipping is both infrequent and often unreliable. Working collaboratively with the contractor as a team (credit must be given to the contractor Pernix/ MAP Projects) we were able to use pipes supplied for one of the new build projects for Fale Ole Fee and undertaken the necessary remediation.
At the time of writing the Faleaseela scheme has been delayed due to ongoing discussions with locals regarding water rights and the scheme’s effect on the local waterfall walk, an important tourist attraction.
Samoan law dictates that the government owns the water rights thus through granting consent for the scheme they have given EPC the license to build in this area. However the concerns of the local people need to be addressed, further demonstrating the importance of stakeholder management and the need to gain local buy in at the earliest possible opportunity.
Currently discussions are ongoing between the EPC and local villagers. They are working towards an arrangement to share the resource including allocating specific times of the day when the scheme may be switched off so tourists can visit the waterfall.
The largest of the three new schemes Fausaga Tafitoala has just commenced construction and will be completed in early 2018. As per the rehabilitation scheme GRP pipe will be used for the main pipeline (approximately 3km). Equally as important, the pipeline will be installed by the now highly skilled local labour force, who are now experienced in the laying and installation of GRP pipes.
To protect both the pipelines and turbines from sediment erosion, Coanda screens have been used for the intake, again a first in the Pacific (excluding PNG). This is a good example of taking a small piece of hydro technology from one part of the world and applying it to another.
The Faleata scheme is on the larger island of Savai’i (which is one of the largest islands in the South Pacific) which interestingly only accounts for 25% of the population of Samoa. The lower population density on Savai’i is mainly attributed to a lack of readily available fresh water as Savai’i has numerous volcanic lava tubes which sees large volumes of river flows disappearing underground and out to sea. Water security is therefore extremely important and as this scheme shares an intake and pipeline easement with the Samoa Water Authority it has been paramount to ensure that flows to the water treatment plant remain unaffected by any turbine outages.
Although small schemes, combined these projects will contribute up to 1.5GWh of additional renewable energy to the Samoan grid, significantly offsetting diesel costs and further decreasing Samoa’s dependence on imported energy sources.
Construction of the schemes has recently commenced with completion expected in early 2018.
Fuluasou Hydropower Scheme
The Fuluasou scheme involves the rehabilitation of an old pre-1940s thin arched dam, the construction of a new pipeline (generally along the same alignment as the original pipeline) from the dam to the powerhouse through existing properties and a golf course and the construction of a new powerhouse.
The main challenge of this scheme involves the construction of the main pipeline through a wealthy landowner’s garden which has encroached on the pipeline easement. As the project has been funded by the Asian Development Bank the landowner effectively has ‘squatters rights’ for disturbance of his property. Negotiations have been completed and the scheme is currently under construction and is expected to be completed in early 2018.
Why small hydro?
Samoa has experienced an explosion of renewables in recent years. Not only have new PV and wind projects been funded through various government grants and loans, there has also been a number of Independent Power Producers (IPPs) developing PV projects.
The increased penetration of utility sized PV systems directly into the national grid has proven to be problematic for EPC in the context of reliability. The variability of solar resources during diurnal peaks has often resulted in brown-outs and in the worst cases total system failure with system frequency going well below safety levels. As a countermeasure, EPC is currently forced to run its expensive medium speed diesel generator as spinning reserves during the diurnal peak hours.
The rehabilitation and building of the new hydropower schemes will allow EPC to manage their grid better. In addition the flexibility of storage on the rehabilitation projects will allow EPC to use PV during the day and hydropower at peak times (typically first thing in the morning and early evening) when PV is not available.
In addition to the hydropower schemes EPC is currently in the process of implementing two battery storage projects across the islands, a 6MW plant and a 2MW plant. These battery plants will further allow EPC to manage their renewable energy fleet efficiently further stabilizing the grid.
Samoa’s renewable energy success is the result of a strategy that includes numerous projects both at a government level (with aid funding) and through private developers. EPC continues to look for opportunities to further diversify their generation portfolio and identify new projects to further reduce their dependence on diesel power and solve the key issue of grid stability.
Even with the increase in PV, small hydropower has been seen as an essential ingredient in the renewable energy mix and will continue to serve EPC and Samoa providing clear reliable renewable energy.
Resilience is key to future projects. This will be important across the Pacific. Projects must be resilient to both natural disasters and climate change. Not addressing these issues can create legacies that could cripple a country should they become over dependent on them.
Samoa has proven itself as a leader in small hydro and the global fight against climate change.
Andrew Bird Meng is a Senior Hydropower Engineer, Asia Pacific Dams and Hydro Sector Leader for Stantec New Zealand. Email: Andrew.Bird@stantec.com