Just recently, the Cape Verde village of Monte Trigo experienced its first 24 hours of electricity. The 60-family community is only reachable by boat and is completely dependent on fishing and its trade with nearby villages. The need for ice to preserve fish is vital, and villagers must travel five-hour by boat to purchase it.
A reliable and clean source of energy was needed to enable sustainable and affordable electricity. It would not only provide basic needs like lighting, communication and community services, but also be useful for ice production.
With the support of the ACP-EU Energy Facility programme, local groups responded to help finance and develop an off-grid solar energy project. The installation includes a rural multi-user solar micro-grid with a photovoltaic generator mounted on a special wooden pergola. The pergola also provides shade to the village’s schoolyard.
The needs of the village are supplied with standard electricity of 230V, 50Hz AC delivered through an 800m aerial distribution line to 60 users including households, one school, a church, a kindergarten, a health centre, a satellite TV dish centre, three general stores and 22 street lights.
Studer Innotec contributed with technical know-how, supporting Trama TecnoAmbiental (TTA), the designers of the facility, in accomplishing this original solution where two micro-grids share excess energy. Their Xtender inverter-chargers allowed a flexible management of the system’s energy production and consumption.
The 214 A-130P modules (each containing 36 polycrystalline cells) were supplied byATERSA, that also designed the pergola to aid the installation of the modules and supplied the batteries, regulators, converters and all the structures required for installation of the system.
The PV micro power plant can produce an average of 74kWh per day. Part of this energy is consumed during the daytime and part is stored in batteries with a capacity of about 370 kWh for night-time consumption. The old 20kVA generator can be used as a backup burning expensive diesel fuel, so it is essential that users understand the implications of their behaviour on the electricity service and cost.
Batteries with 370 kWh capacity for energy storage
In the initial phase of the project, TTA interviewed users to assess their energy needs and their willingness to pay for the 24 hour service. Then the concept of Energy Daily Allowance (EDA) was introduced.
The EDA makes the demand-management more intelligent and flexible by capping the power and energy available to each user to an agreed maximum. This ensures the plant operates within its rated design and prevents black outs or unforeseen increases in operating costs because of higher back-up diesel fuel consumption. This limit is, nevertheless, flexible, depending on the plant’s condition. On very sunny days users may make use of the surplus generation at no extra cost. Each family chose their EDA from five possible options:
| Energy demand type | Energy Daily Allowance [Wh/day] | Power limit [kW] |
| Very Low | 825 | 0,55 |
| Low | 1100 | 0,55 |
| Medium | 1650 | 1,10 |
| High | 2200 | 1,10 |
| Very High | 3300 | 1,65 |
EDA tariff options
Tariff collection is based on fixed monthly fees related to the contracted EDA and sustains operation and maintenance activities and pays back part of the capital costs. Users are very happy with this scheme because it allows them to have an energy budget cost that they can count on.
The implementation is done through a special type of meter – called an electricity dispenser – that permanently shows the available energy allowance and provides a signal to encourage or prevent consumption, according to the plant’s condition.
Major changes are already shaping the life of this community: one user already has bought his first refrigerator. It is expected that with the two ice machines, capable of up to 500 kg/day production using peak-of-the-day, surplus generation will improve the commercial activity which sustains the village’s economy.
Written by Simon Rolland, Secretary General of the Alliance for Rural Electrification.
