23-CS-3 Sustainability, Engineering and the Environment · May 2018
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — May 2018 — 11-CS-3 Sustainability, Engineering and the Environment. Open book; non-communicating calculator permitted. Any four questions constitute a complete paper; all questions are of equal value (25 marks each).
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
| Technology | Land | Fuel cost | GHG emissions | Local health risk | Initial cost |
|---|---|---|---|---|---|
| Wind | H — turbines need wide spacing (tens of km² for 200 MW), though the ground between them stays farmable | L — wind is free; only O&M | L — only embodied emissions in steel, concrete and blades | L — no combustion; noise/shadow-flicker nuisance only | M — moderate capital per MW, but must build ~3× nameplate to offset a ~30–35% capacity factor |
| Nuclear | L — compact site; small upstream uranium-mining footprint plus exclusion zone | L — uranium is a small share of generating cost | L — near-zero at the plant; modest upstream (mining, enrichment, construction) | M — routine risk very low, but low-probability accident, spent-fuel and mine-tailings (radon) concerns | H — highest capital cost per MW, long licensing and build |
| Solar PV farm | H — panels cover the ground (several km² for 200 MW), largely excluding other uses | L — sunlight is free | L — embodied emissions from silicon refining and panel manufacture only | L — no emissions in operation; upstream manufacturing chemicals handled off-site | M — module prices have fallen sharply; a low capacity factor (~15–20% in Canada) still inflates cost per delivered MWh |
| Wood-pellet plant | H — needs a very large forest/fibre supply area harvested continuously | M — pellets must be harvested, dried, pelletized and trucked continuously | M — stack CO₂ is high, offset only over decades by regrowth; harvest/pelletizing/transport add emissions | M — combustion releases particulates, NOₓ and CO near the site | M — conventional boiler/turbine plant plus fuel handling and storage |
| Coal-fired | M — compact plant, but upstream mining, ash ponds and rail yards add land | M — continuous coal purchase and transport | H — the most carbon-intensive option (~0.9–1.0 t CO₂/MWh) plus mine methane | H — PM₂.₅, SO₂, NOₓ and mercury cause respiratory/cardiac illness; mining hazards upstream | M — mature technology, but scrubbers and emission controls add substantial capital |
Environmental: the combustion options (coal, and to a lesser degree wood pellets) dominate on greenhouse gases and air pollution once upstream mining, harvesting and transport are counted, while wind, solar and nuclear are low-carbon across the life cycle. The renewables pay instead in land: wind and solar are diffuse sources and need far more area per MW than a compact nuclear or coal station, and pellet supply needs a large forest area. Social: local health risk is highest for coal (chronic air pollution affecting everyone downwind) and medium for biomass combustion; nuclear's routine risk is very low but its accident and waste risks drive public concern; wind and solar raise mainly visual and land-use objections. Economic: wind and solar have essentially zero fuel cost but low capacity factors, so more nameplate capacity must be built; nuclear has the highest initial cost and the lowest fuel cost; coal and biomass carry a continuing fuel bill. Considering upstream processes, coal is worst on emissions and health; wind, solar and nuclear are genuinely low-carbon; biomass is only conditionally low-carbon and adds local air pollution. The ratings are relative to one another for a 200 MW facility, and would shift with site (wind/solar resource, forest supply) and with carbon pricing.
