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Case Study: Digicel - Vanuatu
Introduction
Digicel was presented with a number of challenges in the roll-out of base station sites across Vanuatu, a volcanic archipelago of eighty-two islands in the South Pacific. Digicel Vanuatu is part of the Digicel Group and has a 900 and 1800MHz band licence which stipulates licence conditions of coverage for 85% of Vanuatu’s population.
At the heart of the network are three PowerOasis remote backbone sites that carry 60% of the network traffic. On these sites the transmission equipment typically carries 300 times more revenue than is generated by the cell served by the RF equipment as the base station is located within a small rural community whilst connecting major urban areas via the transmission links. A key requirement was to dynamically prioritise the transmission equipment over RF equipment during severe weather conditions in order to maximise revenue.
A further sixty remote sites have been completed by a number of vendors on the Vanuatu islands, seventeen are connected to the grid, twenty two are powered by diesel generator charged hybrid-battery systems, and twenty-four are powered using bespoke, first generation renewable energy solutions (green sites).
The Vanuatu Archipelago
Vanuatu’s population is 220,000 of which only 25% live in the four main urban areas. The population is mostly rural with the ten main islands spread approximately north to south over 700km. Urban infrastructure in terms of road and grid power within the four main towns is adequate. However, rural infrastructure is very limited, with poor quality roads which are severely impacted by adverse weather conditions, and no grid power.
With 75% of the population living in rural areas, the fulfilment of 85% population coverage under the licence mandates a major focus on off-grid remote sites. The north to south alignment of the islands over considerable distances requires these rural areas to support the transmission backbone, further exaggerating the importance of many rural sites.
The cost of delivering high volumes of diesel to remote off-grid locations was predicted to be exceptionally high. Furthermore, many mountainous locations can be inaccessible to large vehicles carrying heavy loads during the nine month long rainy season. Helicopter access is limited by availability, weather conditions and daylight, which is compounded by the need for long flights to cover the physical length of the system.
Finding the Best Solution
Digicel Vanuatu was able to deploy nineteen grid-connected sites in the urban locations where 25% of the population was located. These sites had good access and resilient power supply from the islands’ central generating grid. In the other rural locations however, off-grid solutions were necessary to provide coverage and to operate the transmission backbone.
The green powered solutions for the off-grid sites are based upon an initial evaluation of commercial viability, site logistics and the green power viability of each specific site. The overriding case for green power solutions for these sites was based on the commercial and operational advantage, with environmental benefits being a welcome secondary advantage. Although the capital cost of deploying the green power solutions was higher than the diesel generators, the operating costs are substantially lower without compromising the quality of power availability.
The PowerOasis green power solution used by Digicel is an integrated platform working with a combination of PV arrays, wind turbines, batteries and PowerOasis Controllers, supported by the PowerOasis Manager remote monitoring package. In deployments such as Vanuatu, with very large variances between individual sites, no one standard solution could be deployed on a volume scale. These variances included differing power load requirements as well as local micro-climatic variances on account of specific terrain.
Power Systems
The tables below show the specifications for each of Digicel’s three PowerOasis backbone sites serving the Vanuatu islands.
Digicel, PowerOasis Site 1 Specification
| Equipment |
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Dimensioning |
|
Model |
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Loads (Total = 576W)
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| BTS |
|
|
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Huawei DBS3900 |
| Transmission |
|
|
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Huawei Optix 720 |
| Auxiliary |
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None |
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| Aircon |
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None |
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Power Equipment
|
| Wind Turbine |
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1 kW |
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Whisper 200 |
| PV Arrays |
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3.96 kW |
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BP Solar 3165N |
| Batteries |
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3600 Ah |
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Exide Energystore 4RP1800 |
| Generator |
|
11 kVA |
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Wilson P11E2S-CAE |
| Rectifier |
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50 A |
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Victron Energy Titan 48/50 |
| Controller |
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PowerOasis Controller (R) |
Digicel, PowerOasis Site 2 Specification
| Equipment |
|
Dimensioning |
|
Model |
|
Loads (Total = 576W)
|
| BTS |
|
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|
Huawei DBS3900 |
| Transmission |
|
|
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Huawei Optix 720 |
| Auxiliary |
|
None |
|
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| Aircon |
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None |
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|
|
Power Equipment
|
| Wind Turbine |
|
1 kW |
|
Whisper 200 |
| PV Arrays |
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3.96 kW |
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BP Solar 3165N |
| Batteries |
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3600 Ah |
|
Exide Energystore 4RP1800 |
| Generator |
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11 kVA |
|
Wilson P11E2S-CAE |
| Rectifier |
|
50 A |
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Victron Energy Titan 48/50 |
| Controller |
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PowerOasis Controller (R) |
Digicel, PowerOasis Site 3 Specification
| Equipment |
|
Dimensioning |
|
Model |
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Loads (Total = 1400W)
|
| BTS |
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Huawei 3012AE |
| Transmission |
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Huawei Optix 720 |
| Auxiliary |
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None |
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| Aircon |
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None |
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Power Equipment
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| Wind Turbine |
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3 kW |
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Whisper 500 |
| PV Arrays |
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7.35 kW |
|
Sharp (42 x 175W) |
| Batteries |
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3990 Ah |
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Exide Energystore 4RP1330 |
| Generator |
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11 kVA |
|
Wilson P11E2S-CAE |
| Rectifier |
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50 A |
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Victron Energy Titan 48/50 |
| Controller |
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PowerOasis Controller (R) |
PowerOasis Controllers
For its mission critical backbone sites at Vanuatu Digicel has deployed a PowerOasis Controller (R) solution. The purpose designed telecoms-grade PowerOasis controller (R) features an integrated wind turbine power controller offering higher efficiency, 1+1 power and control system redundancy for high availability, and optimised battery conditioning algorithms. In addition it offers two independently controlled power supplies, allowing autonomy between the RF and transmission systems on site. By way of example, this might allow a backbone site to have one week’s battery autonomy on the transmission subsystem, but only twenty-four hours battery autonomy for the RF system (as the RF system has substantially less revenue at risk).
Information and Data Sources
Source 1: PowerOasis field reports
Source 2: GSMA Green Power for Mobile Programme, Digicel Vanuatu, Commercial Roll-out of Green Power Technical Case Study http://www.gsmworld.com/documents/digicel_vanuatu.pdf
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The cost of delivering high volumes of diesel to remote off-grid locations was predicted to be exceptionally high
Although the capital cost of deploying the green power solutions was higher than the diesel generators, the operating costs are substantially lower without compromising the quality of power availability
The purpose designed telecoms-grade PowerOasis controller features an integrated wind turbine power controller offering higher efficiency, 1+1 power and control system redundancy for high availability, and optimised battery conditioning algorithms
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