This sounds great, and could be very useful to those billion people that currently have no access to electricity.
“induction cooking [cooker], a refrigerator, and a washing machine” - it’s useful to help people conceptualise what the energy will be used for by providing such examples. In addition, it’s useful to make some typical assumptions about their usage and power requirements so that the challenge can explicitly set minimum requirements for power output (kW) and energy required (e.g. kWh per day).
“Highly efficient” - efficient systems are welcome, of course, but for some solutions this might not be as important. For example, solar power is derived from a “free” source of energy and so efficiency is harder to define and perhaps not as important in this context. Other criteria might indirectly influence the required efficiency though, such as the maximum area, volume, mass and device cost specified in the challenge.
The modular and scalability requirement is a great idea.
Rather than a target size of 100 people, it might be better to quantify how much a “typical” house uses (kW, and kWh/day) and then pick a number of houses to demonstrate it on, across a number of villages in different environments [bearing in mind some villages might be very small]. There might be small villages and larger villages in the challenge - to demonstrate how well a solution does actually scale (and the cost per user implications).
Different environments should, ideally, be used. For example, northern latitudes might not support typical solar powered solutions - unless it includes a very efficient seasonal storage technology to release power in the winter. So this might mean a test duration over an entire year - if such solutions are to be catered for. It’d also test the durability of the energy storage system over time and during harsh environmental conditions.
In terms of the specifications we might want to be mindful that the solution might contain two (or more) parts, e.g. energy collection / generation, and energy storage (and distribution). For example, solar panels on house roofs and a community battery.
Regarding “clean” we might want to expand this to include no pollution, e.g. no emissions to air and no pollution of land or water (surface and groundwater). Similarly, no production of long lived toxic waste in any part of the system (e.g. no dioxins, PCBs, PAH, or radioactive material).