Solar lighting in a heritage wharenui
A remote papa kāinga of six whare wants solar lighting in the 12 m × 8 m wharenui for evening wānanga. A volunteer has priced four 10 W LED lights, a 100 W panel, a 100 Ah battery, and a charge controller for $1,200. Winter sun at the site averages 2.5 peak sun hours. The wharenui is a heritage building with carved poupou and an unfinished ceiling; no electrician lives within 80 km. The rūnanga has a rule that no wiring may be fixed to carved surfaces. The volunteer says: 'We will run the cables along the floor and tape them down - it will be fine.' A kaumātua asks whether the lights will still work in July, when the wharenui is used four nights a week for 3 hours.
1. Estimate whether the system will meet July use and recommend any changes.
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Load: 4 lights × 10 W = 40 W; 3 h × 4 nights = 12 h per week; 40 W × 12 h = 480 Wh per week. Battery: 100 Ah × 12 V = 1,200 Wh; usable at 50% depth of discharge = 600 Wh. That covers one week's load with only 120 Wh margin, so a run of cloudy days is risky.
Generation: 100 W × 2.5 peak sun hours = 250 Wh per day gross; with 70% system efficiency, about 175 Wh per day, or 1,225 Wh per week. In theory generation exceeds load, but the margin is thin in winter and battery age, cable loss, and shade will reduce it. Recommendation: add a second 100 W panel (about $200) or reduce to three lights and use task lamps. Also use a controller with low-voltage disconnect and a battery monitor. Do not rely on the estimate alone; log voltage and usage for two weeks in June.
2. Explain the cultural and safety issues with the proposed cable route.
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Taping cables to the floor is unsafe and culturally unacceptable. Safety: taped cables create a trip hazard in a dark wharenui, they are damaged by chairs and feet, and tape fails with heat and age; damaged 12 V cables can short and start a fire. Cultural: the rūnanga rule protects carved poupou, and a taped cable crossing the floor also crosses the mana of the wharenui; it looks temporary and disrespectful.
The cable route must avoid carved surfaces and the main floor. Options: run cables in surface-mounted conduit along non-carved wall plates and rafters, or use freestanding solar lanterns with no fixed wiring. If any fixed wiring is used, it should be installed by a qualified person or at least inspected by one; 12 V is lower risk but not no risk, and the wharenui's heritage status means any fixing must be approved by the rūnanga. Consult before drilling.
3. Recommend a decision about installation and who must be involved.
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Do not install the taped-floor version. The rūnanga should decide between two options: (a) a fixed system with conduit on non-carved surfaces, installed or inspected by a qualified electrician and approved by the rūnanga; or (b) a portable solar lantern system, which avoids fixing to the heritage fabric and can be moved for wānanga.
Given the 80 km distance and $1,200 budget, option (b) plus one extra panel may be the better first step; it can be tested this winter and upgraded later. The people who must be involved are the rūnanga (heritage and protocol), the kaumātua (use and blessing), a qualified electrician or inspector (safety), the volunteer (maintenance), and the whānau who will use the lights. Record the decision, the reasons, and the maintenance plan. Revisit after two weeks of June logging, not after a single night.