PowerGen’s PowerBox in rural Tanzania. Credit — PowerGen Renewable Energy.

Scaling Micro-grid Deployment in Sub-Saharan Africa with Batteries

By: Sam Booth and Eric Lockhart, National Renewable Energy Laboratory (NREL)

Micro-grids stand to play a critical role in expanding electricity access in sub-Saharan Africa (SSA). The International Energy Agency estimates that nearly half of the investment in electrification globally in the coming decades will be on micro-grid expansion. Investment of this scale, however, is unlikely to be met by governments and donors alone, making successful mobilization of private investment a paramount criterion for success.

Batteries, which are often a core element of micro-grids, represent a substantial portion of the capital cost and are, therefore, an important component of the tariffs charged to customers and ultimately determine whether micro-grids can be financially sustainable. For example, a sample system designed to supply a representative off-grid community (100 households) with enough electricity to run lights, radios, and small-scale commercial activities could be powered by 25 kilowatts (kW) of solar panels that are paired with a 40 kilowatt hour (kWh) battery. In that example, the battery could be ~20% of upfront costs and ~35% of lifecycle capital expenditures. Those costs are normally passed on to customers, making batteries a key determinant of affordability and business model sustainability. As a result, understanding key considerations for selecting a battery type and operating it effectively are foundational to developing sustainable micro-grid business models and taking micro-grid growth to scale across SSA.

While batteries have been deployed in many micro-grids worldwide over the past few decades, unanswered questions remain on how best to apply them to the context of off-grid micro-grids in Africa. Micro-grid development for electricity access in developing countries is still a relatively nascent industry and lithium-ion batteries have only recently declined in price enough to make them potentially viable options for African micro-grids. Micro-grid projects are being built, but the industry has yet to coalesce around battery best practices.

The PowerGen integrated solar panel and battery. Credit — PowerGen Renewable Energy

Partnerships to support micro-grid market growth

Power Africa has been partnering with the National Renewable Energy Laboratory (NREL) to advance this conversation, as well as accelerate key elements of micro-grid standardization. Building on analytical work with developers in SSA and tools at NREL, we are producing a study of battery economics and optimal operation in micro-grids. This study will answer a key set of questions highlighted below to inform micro-grid developers’ choice of battery and how to optimize battery performance and economics.

Lithium-ion or lead acid?

Lead acid has long been the standard for stationary battery systems, but performance characteristics and declining costs are making lithium-ion batteries more cost-competitive over the life of a system. The study will assess lifecycle costs for each battery type across different regions (East, West, and Southern Africa) and community characteristics (residential-use focus vs. commercial-use focus). From this analysis, the study will investigate the relative trade-offs between upfront costs and replacement costs to offer guidance on what micro-grid characteristics might make a lead acid battery more or less attractive relative to a lithium-ion battery.

A lead-acid battery facility stores electricity at a 1.5 MW micro-grid on Bugala Island, Uganda. Credit — Jeremy Faber, Power Africa

How should you design the enclosure housing the batteries?

Another important determinant of battery performance and economics is the design of the enclosure or building that houses the batteries. For example, does it make more sense to house the batteries in a brick or cement building to manage operating temperatures? Or, is it economical to build shade structures or add insulation to the walls of the enclosure? The study will assess these issues to identify cost-optimal conditions for battery performance, while also discussing best practices in battery operation that are context-independent (such as separating the inverter from the battery or not combining used and new lead acid battery cells).

What level of cooling investment is optimal?

Effectively selecting a battery and enclosure still leaves decisions on conditioning the space and optimizing trade-offs of up-front system costs and battery degradation rates (and associated replacement costs and timing). Should you keep the space well vented and run small fans to circulate the air or does it make sense to invest in an air conditioning unit? At which temperature should the fans or unit be set to optimize the trade-offs between increased electricity consumption and increased battery life for a battery that stays at a cooler temperature?

The NREL and Power Africa teams welcome input into what would make this battery analysis and research most impactful and perspectives from developers or other stakeholders who have assessed which battery type and conditioning approach work best for them. Please contact Eric Lockhart and Sam Booth with ideas or experiences with batteries and enclosures to share.

The broader NREL and Power Africa partnership is intended to support standardization of micro-grid projects and the scale up of investment in collaboration with a wide range of stakeholders with an interest in micro-grid deployment, including developers, investors, policymakers, regulators, and the communities the systems serve. In support of these broad goals the analysis from two other technical support projects that were recently released, focusing on technical and business considerations for the productive use of energy in micro-grids and good practices for agreements between micro-grid developers and their customers.

The productive use and good practices for customer agreements documents can be found here: https://www.nrel.gov/docs/fy18osti/71663.pdf and here: https://www.nrel.gov/docs/fy18osti/70777.pdf.

For more information, visit www.cleanenergysolutions.org/qaf.