What are solar nano-grids?

Micro-grids are distributed generation systems connected to end-users that are stand alone or connected to an electrical network. Solar nano-grids (SONG) are based on micro-grids but are smaller in size (1-5kW) and are typically off-grid.

They use the sun’s energy to generate electricity in photovoltaic (PV) modules. This contrasts with individual solar home systems (SHS) that only provide electricity for lighting and other basic household needs such as phone charging, a fan, radio or TV. SONG not only supply the homes in a community but also enables economic activities to take place to make use of spare electrical capacity, such as egg incubation or IT services.

The following figure shows one SONG concept.

Figure: Example of Solar Nano-Grid System Concept

This example shows one configuration with wires to individual homes.  This works for small distances where the PV modules are located close to the community e.g. a small village of say 50 households within about 100m. SONG can also work for more dispersed communities using a battery swap approach.

Rather than wiring up individual homes, with the added cost, householders bring their battery to a SONG hub (once or twice a week) and charge them during the day to collect in the evening.

Nano-grids ensure more efficient and effective use of the energy produced by solar modules. For example, In Bangladesh, PV modules produced at least 20% more energy during the sunniest period of the year (March-May), which is also the main irrigation season.

This excess energy could be used to run community services such as an irrigation pump or a rice-huller, which reduces energy cost, the usage of diesel pumps, and ensures better utilization of energy.Like SHS SONG operate by generating and making use of direct current (DC) power.  This avoids the cost of inverters and associated conversion efficiency losses. Different types of DC devices, such as TVs are now available.

SONG has advantages over small SHS by providing communities with the power for small-scale economic activities. SONG therefore focuses on both the individual and the community benefits which contributes to more sustainable opportunities.

Solar nano-grid