A hybrid system can represent both an environmental and financial good to a small, isolated community. Fossil fuel generators are relatively inexpensive to buy, and expensive to operate (cost of diesel, maintenance, fuel & service delivery to remote sites) while renewable resources require a large initial capital investment, but then are inexpensive to operate. A draw back with renewable sources is that they are not always available, thus combining them with a fossil fuel source and an energy storage system allows for the best combination of cost effectiveness, source reliability and environmental consciousness.

The hybrid system at Gobabeb incorporates photovoltaic solar modules as renewable energy resource as well as fossil fuel sources through the use of two diesel generators. The overall energy system relies pre-dominantly on the renewable energy generated and only requires support from the diesel generators during times of high activity at Gobabeb or during spells of inclement weather. Combining an energy supply in this way allows for an optimization in terms of efficiency (RE portion is always utilized to its full extend and the diesel generators are always operated at full capacity factor) leading to the optimal financial performance of such a supply.

The design criteria for the hybrid supply system are based on the needs of the Gobabeb consumers and the technical specifications were drafted to meet these criteria.

The hybrid system consists of the following components:

Diesel generators: Two Deutz diesel generators 50kVA, installed in 1972 and overhauled six times to date;


Battery storage: 200kWh, tubular deep cycle batteries;


Power converter: 30kVA, inverter as well as charger, with integrated 30kW
solar charge controller;

Hybrid control system: Automatic mode, where the diesel generator can start during different pre-set times when reaching a particular state-of-charge – or
Manual mode, where the system operator start the diesel generator as required.

The system design is flexible in that it will be able to integrate other resources, such as wind power in the future.

The hybrid system generates energy for a mini grid - a small network of energy users in close proximity, which are connected to a central supply. The mini-grid supply, i.e. the hybrid system generates standard 230VAC/400VAC power, which is fully compatible to the electricity supply in the city. Hence mini-grids can be connected to the utility grid without changes in the infrastructure (this will not be the case for Gobabeb since the grid is unlikely to extend over the current 70km distance).

A mini-grid has the advantage of “pooling” its energy and making it available to any of the users. Any energy saving within the mini-grid is therefore of benefit to the remaining users. Since the hybrid system is designed to provide power to all its users in the mini-grid it is also able to produce relatively high power at selected points e.g. machinery, pumping, air-conditioners, if required. A decentralized Solar Home System supply in comparison is not able to make saved energy available to another user, i.e. this energy will be “lost” if not used, nor is it able to produce more power then its design power.

A mini-grid is usually only viable if users use in excess of 0.75kWh per day, else the infrastructure becomes too expensive and SHS’s are more viable.