Mini-Grids vs. Mesh-Grids

By Nithya Menon
March 14, 2022

Off-grid communities vary in size, location and energy-demand, so choosing the right technology is key to ensuring long-term project success.

-- If you're short of time, you can skim through by reading the bolded text only - it will give you the general gist of this blog. Otherwise, read in full to get all the juicy details 😉

For the past decade, the dominant methods of delivering last-mile electrification have been:

  1. Solar home systems (SHS), and
  2. Mini-grids

Both of these technologies have their strengths, but they’ve struggled to deliver reliable, productive and affordable energy to the most remote areas of the world.

We present a third contender:

  1. Mesh-grids

But before diving into the details of mesh-grids, let’s review SHS and mini-grids →

SHS: Flexible & fast, but insufficient power

SHS are flexible, fast and simple. They have provided millions with basic access to electricity for essentials like lighting and phone charging. However they simply don’t provide enough energy or power for productive use – which is key for long term sustainability of last-mile electrification projects.

Solar home systems SHS
SHS supports lighting, phone charging and other low-power appliances

Although impactful, SHS are an incomplete solution, incomparable to grid-like solutions (mini-grids and mesh-grids) in terms of providing productive power for developing communities.

Mini-grids: High power, but expensive & rigid

Mini-grids are built with a centralised architecture where energy is generated and stored at a single point then distributed all the way to the farthest households. Mini-grids supply high levels of productive power which makes them suitable for densely populated areas that lack a reliable grid. However approximately 65% of unenergized people (500 million globally) reside in rural villages with dispersed households, low population density, and variable energy demands tied to the seasonal changes of subsistence farming. By the nature of their design, mini-grids are not engineered to effectively service this market.

The main drawback of deploying mini-grids at the last-mile comes from the high-cost of distribution assets (poles, cables, inverters). Safely distributing power over long distances, whilst also accounting for peak utilization, necessitates high-voltage and high-current cabling, heavy duty transmission poles and large inverters – all of which can only be serviced by licensed technicians who need to travel far and wide to reach the site. In the event of failures, it’s expensive and slow to perform maintenance and the quality of service suffers.

As a result, approximately 50% of capital expenses goes into distribution infrastructure whilst operational expenses can amount up to 40%* of total project costs. This is why mini-grids have an average payback period of 10 to 20 years, many failing to demonstrate financial viability when deployed in last-mile regions.

* based on anecdotal interviews with mini-grid developers placing average maintenace cost at $50/household/year
Solar home systems SHS

The centralized architecture of mini-grids does not efficiently service dispersed populations

mini-grid cost Minigrid

The World Bank estimates that annual mini-grid installations need to increase by 40x to meet 2030 electrification goals, but their high capital and operational costs are prohibiting them from scaling as a sustainable last-mile electrification solution.

Mesh-grids: Powerful, modular & scalable

Okra mesh-grids (OMGS) hybridize the speed and flexibility of SHS with the reliability and energy availability of mini-grids.

Solar home systems SHS

In contrast to centralized mini-grids, mesh-grids are decentralized and modular – generation and storage assets (solar panels and batteries), along with inverters, are installed at individual households.

This design ensures the majority of energy is generated and consumed at the same place (just like SHS), but additionally, neighbouring households can also interconnect and form power-sharing clusters, where smart algorithms redistribute excess power at 50V DC, which can be operated on safely by local community members who have basic training.

This power-sharing feature of mesh-grids supports load variability, increases reliability, and reduces upfront costs. Meanwhile, isolated households can remain standalone until there is a neighbouring household that’s ready to connect and share power. Mesh-grids expand freely over time as more households join a network and demand grows.

Solar home systems SHS

This decentralized architecture is fundamentally enabled and controlled by the Pod – Okra’s proprietary controller that simultaneously manages power distribution, remote monitoring, and mobile billing. Each Pod outputs 1.2kW (AC or DC) – enough to power productive appliances and drive network profitability. Excess power from commercial loads or nearby grids can be drawn into mesh-grids for lower cost distribution via Okra’s “Grid Gateway” (more on this to come soon).

A primary advantage of decentralizing generation and storage is that it significantly reduces the total amount of power moving throughout a network, as energy is mostly generated and consumed by the same household and any excess is optimally sent to nearby homes. This node-to-node distribution in mesh-grids requires 10x thinner cables, reducing distribution costs by 90% compared to centralised mini-grids.

Centralized mini-grids

    • 10× thicker conductors needed to disribute high voltage (230V to 33kV) and high current
    • Isolated households have a significantly higher cost per connection, or are left unconnected
    • High power output, support commercial/industrial anchor loads

Decentralized mesh-grids

    • Isolated households can be connected as standalone systems initially, then inter-connect into mesh-grid clusters later (once a neighbouring household is also ready to inter-connect)
    • Housholds >50m apart do not need to be connected, reducing cabling needs
    • Algorithms optimize power transfer to reduce waste
Another advantage of decentralization is that capacity can be added in a modular fashion, without having to replace existing assets. This enables steady load growth as energy demands increase over time, and enables rapid grid expansion as additional households join in the future.

Centralized mini-grids

    • Rigid, cannot be scaled incrementally

Battery capacity cannot be increased without being replaced, adding significant costs to replace and upsize all assets when demand grows.

Decentralized mesh-grids

  • Modular, assets can be added over time

Extra solar panels and batteries can be added to individual households to match load growth or staggered sign-ups, without replacing existing assets or massively oversizing.

The 50V DC distribution voltage in Okra mesh-grid networks is specced and designed to allow local community members to safely conduct maintenance with minimal training. This gives energy companies the option of hiring staff locally, building community trust and buy-in. Instead of sending qualified technicians on expensive trips to make long-awaited fixes, O&M in a mesh-grid is cheap, fast and easy.

Centralized mini-grids

    • Unsafe, for local community members to maintain
    • Technicians must travel to the last-mile to resolve issues
    • Majority of lifetime O&M costs is for staff & logistics.
    • Centralized asset  failures bring the entire grid down
    • Simple to locate problems with fewer points of failure 

Decentralized mesh-grids

    • Maintainable by local staff and issues can be resolved immediately
    • Builds community trust and empowerment
    • Reduces staff and logistics costs by ~50%
    • Issues occur on individual homes, isolating outages 

    • Distributed assets results in distributed issues across site
Finally, mesh-grids are faster to deploy because panels, batteries, and Pods are installed on individual houses, The design removes the need for land acquisition, accelerating the project delivery timeline.

Centralized mini-grids

  • Requires land acquisition

Land acquisition requires village-wide consensus, which takes >6 months on average. Once land is purchased, security needs to be paid for.

Decentralized mesh-grids

    • Don’t require land

Developers only need direct agreement from the household to install equipment.

Cost Comparisons

When it comes down to it, mesh-grids provide more utility per dollar for off-grid energy developers because the technology is specifically tailored to the unique traits of last-mile communities.

The comparison below is an apples-to-apples summary comparison between a mini-grid and mesh-grid, which are both specced to provide an average daily load of 600Wh/day, with Lithium LFP batteries, in a rural off-grid communitiy.

Mini-grids

Mesh-grids

Power output

>1.2kW AC

1.2kW AC & DC

Distribution specs

230V AC (single or 3-phase)

50V DC

National grid connect

Draw & supply

Draw only

$ per connection

~$1100

~$625

(~$350 with REA Nigeria subsidy)

CapEx for 10k households

$11M

$6.25M

 Simulations

To further validate this mini vs. mesh-grid cost comparison, this example from Okra’s Network Planner tool uses satellite data to detect households, automatically plan mesh and mini-grid networks, and produce a detailed cost comparison. Across various villages, we see variation in where mesh vs. mini grids are favorable, and the benefit of this analysis is to determine where each technology is most suited to provide the lowest cost electrification. The following example demonstrates a mesh-grid suited community in Haiti.

Solar home systems SHS

An example site simulation of a last-mile community in Haiti, from Okra’s Network Planner tool

Number of households = 2,636
Designed daily load = 400 Wh/day

Totals

Mini-grids

Mesh-grids

PV capacity

390 kWp

392 kWp

PV cost

$136,500

$137,400

Battery capacity

2,300 kWh

2,320 kWh

Battery cost

$639,000
$643,000

Inverter cost

$261,400

$197,700

Distribution cost
(cables, poles)

$1,420,000
$116,800

BOS & mounting cost

$144,500

$225,300

Metering cost

$92,200

$329,500

CapEx

$2,693,600

$1,649,700

$ per connection

$1,021

$625

We generate these simulations using averages from Okra project data, as well as research and other field data. Our models are continuously updated to give an accurate forecast, but we’re always eager to hear feedback or adjust assumptions based on other suppliers. Stay tuned for a much deeper dive into these simulations and the assumptions they’re built on, coming soon!

Advancements in battery and solar technologies make decentralized infrastructure affordable and practical. With mesh-grid technology we can leverage these benefits to provide robust and reliable electrification at the lowest cost. 

Mesh-grids are already being rolled out around the world, with particularly exciting scale-ups happening in Nigeria as we speak! Let us know if you’re an energy developer or otherwise interested in seeing mesh-grids help end energy poverty.

It’s time to bring #Powe​​rToThePeople

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Nithya Menon is an engineering graduate from Harvey Mudd College who has spent her career developing technology targeted towards empowering marginalized and developing communities worldwide. She has been pivotal in designing Okra's key power-sharing algorithms, IoT firmware, and grid management software - and now drives the direction and strategy of Okra's technology as Product Development Lead.

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