Settlement power: budgets, microgrids and priorities
Size a settlement where generation, storage, distribution and load shedding must continue through dust, maintenance and source loss.
Mastery objectives
- identify the functions, interfaces and degraded scenarios specific to the subject
- repeat simple calculations and verify units, assumptions and margins
- turn a principle into a verifiable procedure or decision
- connect the subsystem to human, energy and logistics constraints
1. Peak power and daily energy answer different questions
A system can have enough energy over a day while being unable to supply a short peak. Budgets therefore track instantaneous kilowatts and accumulated kilowatt-hours. Pumps, furnaces, communications and vehicle charging cannot simply be added as if all loads operated with the same time profile.
2. Classify loads before calculating generation
Vital, critical, deferrable and discretionary loads do not have the same claim on power. Life support, minimum thermal control and safety communications remain high priority. Manufacturing, electrolysis or charging may sometimes be shifted. The hierarchy is written before the emergency so that shedding is not improvised under pressure.
3. Microgrid: multiple sources, multiple stores, one stability problem
A base may combine solar, fission, batteries and thermal storage. The microgrid shares power while maintaining voltage, frequency or DC-bus limits. Loss of one converter must not turn a local failure into a base-wide blackout.
4. Storage: reason in usable autonomy, not nameplate capacity
A 1 MWh battery does not necessarily provide 1 MWh to loads. Depth of discharge, temperature, aging, efficiency and safety reserve reduce usable energy. The budget states the energy that can actually be delivered in the critical scenario.
5. Dust, night and maintenance: nominal generation is not available 100% of the time
Solar production and nuclear availability both change with environment and maintenance. Energy architecture therefore uses time profiles and failure scenarios. Storage bridges mismatches between demand and generation; it does not excuse chronic undersizing.
6. Distribution and common-cause failures
Two sources feeding the same converter or running through the same cable are not truly independent. Redundancy separates common causes across location, conversion, protection, cooling and control.
7. Microgrid stability: balance power and energy
A positive 24-hour energy balance does not guarantee a stable grid. A base can produce enough total energy and still lack instantaneous power during compressor startup or immediately after loss of a source. Energy in kilowatt-hours must be distinguished from power in kilowatts. Storage has to absorb transients and give dispatchable sources time to take over. Control strategy also needs the priority and dynamics of every load: a greenhouse may be reduced briefly, while a medical pump may require uninterrupted supply.
8. Black start: rebuild the grid from almost nothing
After a total outage, many components required for restart themselves need electricity: controllers, pumps, heaters, communications and converters. Black-start capability means recreating supply without relying on an already energized grid. An autonomous source establishes the first bus, then branches reconnect in an order that avoids simultaneous inrush loads. The procedure should be tested with cold batteries, converters that are actually available, and explicit criteria for authorizing each reconnection step.
9. Energy growth: do not consume the entire margin
A growing settlement adds greenhouses, workshops, laboratories, communications and living areas. If each expansion consumes all available reserve, failure margin disappears. The budget should distinguish nominal demand, peak demand, operating reserve, contingency reserve and storage energy that remains usable after ageing and depth-of-discharge limits. Electricity must also be linked to heat: a machine rejecting several kilowatts can be useful in one condition and a cooling burden in another. Flexible loads should be scheduled rather than sizing every source for the worst simultaneous case.
10. Worked example: battery autonomy in refuge mode
Refuge vital loads consume 18 kW. A battery has 420 kWh nameplate capacity, but only 80% depth of discharge is allowed and end-to-end efficiency is 92%. Usable energy = 420×0.80×0.92 = 309.1 kWh. Autonomy = 309.1/18 ≈ 17.2 h. A 24 h requirement is therefore not met even though the battery is advertised as 420 kWh.
11. Exercise
Build a 24 h budget with 25 kW vital loads, 40 kW critical loads and three deferrable loads. Simulate loss of 50% of generation for 18 h and create a load-shedding order.
12. Reasoned solution
First classify loads as immediate survival, operational continuity or deferrable, then compare survival power with the remaining source. If it exceeds available capacity, priorities or independent supply must change; shedding only comfort loads cannot solve a structural deficit.
13. Validation mini-project
Design a Mars microgrid: sources, buses, protection, storage, load profiles, priority classes, failure scenarios, restart strategy and stability criteria.