Phase Change Materials for Passive Cooling of Sahelian Buildings: Integration Options and a Screening Assessment for Niger

Aims: The study aims to synthesise phase change material (PCM) classification and building-envelope integration techniques relevant to hot, arid climates, and to carry out a comparative techno-economic and environmental assessment of three candidate PCMs (a paraffin, a hydrated salt, and a water-urea eutectic) for passive thermal regulation of housing in Niger. Study Design: Structured literature synthesis combined with a multi-criteria scoring assessment adapted from established PCM-selection methodology. Methodology: Published thermophysical, economic and environmental data for the three PCMs were consolidated from the underlying laboratory/simulation study and cross-checked against the wider PCM building-envelope literature. Five techno-economic criteria (cost-effectiveness, durability, ease of maintenance, local availability, thermal stability) and five environmental criteria (embodied energy, carbon footprint, biodegradability, end-of-life recyclability, environmental risk) were each scored from 1 (least favourable) to 5 (most favourable) and combined into an unweighted composite index; an annualised areal cost was additionally computed from unit price, indicative areal loading and expected service life. Results: Niger's electricity access rate (about 20% in 2023) is far below the sub-Saharan African average (about 53%) and the global figure (about 92%), underlining the case for passive rather than mechanical cooling. The water-urea eutectic scored highest on the techno-economic index (3.9/5) and on the environmental index (4.6/5), driven by low cost and local sourceability, but had the shortest expected service life (5-10 years); paraffin scored lowest on cost-effectiveness and on the environmental index (1.9/5) despite the best durability and thermal stability scores; the hydrated salt occupied an intermediate position throughout. Annualised areal cost, however, favoured paraffin's long service life enough to narrow the gap with water-urea considerably. Conclusion: No single material dominates across all criteria, which argues against a one-size-fits-all recommendation. Paraffin suits applications where dynamic thermal performance and longevity are prioritised and where the budget allows; the water-urea eutectic suits cost- and carbon-constrained, shorter-horizon retrofits using locally available inputs; and the hydrated salt is a reasonable compromise where corrosion risk can be managed. These results give Nigerien designers and policymakers a first quantitative, climate-specific basis for PCM selection, ahead of the full life-cycle assessments that scaled deployment will eventually require.