What are the key advances in mini-grid transmission and distribution?

Transformers are one of the highest-cost components of transmission and distribution systems. Newer energy grids are unable to reuse old transformers as grid systems are updated, because modern systems rely on automated switches and transformers that can be controlled remotely and that send real-time data back to system operators. Improving the reliability of transformers, introducing new transformer technology that makes the grid “smart” and reducing the cost of transformers improves the quality and dependability of power delivered to consumers. By aggressively reducing the cost of grid components, designers can reach economies of scale to help connect communities unable to support higher cost systems.

Emerging technologies for mini-grids are not always high-tech. The Microformer transmission and distribution system keeps costs low by using recycled or off-the-shelf materials, including a reused paint bucket, a transformer from a broken microwave and an automotive spark plug. The Microformer is a 1 kVA transformer that steps up low voltage (120 V or 230 V) to 1.5–2.5 kV for transmission over 5–10 km. A second, identical transformer then steps voltage down to household-level voltages. A low-cost solution, the Microformer also has low losses.

The rapid proliferation of mini-grid technologies has made it difficult for customers, financiers, governments, regulators and donors to compare and evaluate mini-grid components and systems against one another and against manufacturers’ claims. A common quality assurance framework (QAF) would help solve this problem. At the 2013 Fourth Clean Energy Ministerial in India, a key recommendation from a high-level, public-private roundtable on mini-grids was to “develop standards to set a level playing field, encourage investment and drive down prices.”

Many developers and mini-grid experts, however, worry that well-intentioned efforts to develop standards for mini-grid technology may discourage innovation. A voluntary QAF could balance the need for standards against the need for innovation by:

• Providing a formalized common standard for classifying mini-grids
• Establishing benchmarks for mini-grid power quality and reliability
• Describing procedures for measuring mini-grid performance against benchmarks

Voluntary QAFs help give customers confidence that they are receiving the services they pay for, encourage investors to take risks, help developers compare their product against others and give governments confidence that public resources are spent wisely on rural electrification services that meet customers’ needs.

A mini-grid QAF was developed under the Global Lighting and Energy Access Partnership initiative of the Clean Energy Ministerial and the U.S. Department of Energy, in collaboration with the U.S. National Renewable Energy Laboratory. The framework addresses both alternating current (AC) and DC mini-grids, and it will apply to renewable, fossil-fuel and hybrid systems.

Outlets—the receptacles where appliances plug in to receive electricity—are the last point in the distribution systems. Unfortunately, the outlets designed for DC use are poor fits for appliances. The de facto low-voltage DC standard for receptacles and plugs is based on cigarette lighter ports in cars. These ports are bulky, and they have low power ratings. Often, poor contact reliability interrupts the flow of power from the outlet to the appliance.

Anderson Powerpole connectors

Improved DC receptacles would increase the use of low-voltage DC mini-grids and solar home systems. Adopting a new standard is a more promising approach than incrementally improving the current standard based on automobile lighters. One emerging standard is Anderson Powerpole connectors, available as inline connectors and wall-mounted sockets. These connectors provide higher current and more reliable connections. Anderson Powerpole connectors are widely used in industrial applications and amateur radio.