23-CS-3 Sustainability, Engineering and the Environment · December 2018
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — December 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 requirement | Purchased fuel cost | GHG emissions (incl. upstream) | Health risk to local population | Capital cost |
|---|---|---|---|---|---|
| Wind turbines | H — roughly 100 turbines of ~3 MW need wide spacing (several rotor diameters) over tens of km², although farming can continue between the pads. | L — wind is free; only O&M is paid. | L — zero at the site; a small upstream share from steel, concrete foundations and blade manufacture. | L — no emissions; nuisance effects only (noise, shadow flicker, ice throw near the base). | M — moderate cost per installed kW, but the low capacity factor (~30–35%) means more capacity is needed per MWh delivered. |
| Nuclear plant | L — compact site (plus an exclusion zone); upstream uranium mining and tailings add some land. | L — uranium is a small share of generating cost; enrichment and fuel fabrication are the main fuel expense. | L — no combustion; small upstream emissions from mining, enrichment and construction. | M — very low routine releases, but a low-probability/high-consequence accident risk, long-term spent-fuel storage, and radon/tailings exposure near upstream mines. | H — the highest capital cost per kW, with long, overrun-prone construction schedules. |
| Solar PV array | H — about 2 ha per MW, i.e. several km² of land fully covered by panels. | L — sunlight is free. | L — zero at the site; upstream energy for silicon refining and panel manufacture is the main contribution. | L — no emissions in operation; minor upstream chemical exposure in panel manufacture. | M — module prices have fallen sharply, but a low Canadian capacity factor (~13–18%) needs a large installed capacity (and storage) for 300 MW of useful output. |
| Wood-pellet plant | H — the plant is compact, but the forest harvest area needed to supply pellets continuously is very large. | M — pellets must be bought, dried, densified and trucked; fuel is a major, recurring operating cost. | M — stack CO₂ per MWh exceeds coal's and is credited back only as the forest regrows over decades; harvesting, pelletizing and transport add fossil emissions. | M — combustion emits PM2.5, NOx and CO near the plant; truck traffic and pellet-dust fire/explosion risk. | M — a conventional steam plant plus fuel handling, storage and emission controls. |
| Natural-gas plant | L — compact plant; upstream wells, pipelines and compressor stations add a modest footprint. | H — gas is purchased continuously and is the largest share of generating cost, with volatile prices. | M — about half the CO₂ per MWh of coal at the stack, but still fossil, plus upstream methane leakage (GWP 25). | L — clean-burning; mainly NOx near the stack (upstream well-site impacts fall on other communities). | L — the lowest capital cost per kW and the quickest to build. |
Each cell's rating is explained in the table above. Reading across the three dimensions the question names: environmental — wind and solar trade large land areas for near-zero emissions, while biomass occupies large land and emits; social — only the combustion plants (biomass most, gas least) impose routine local air-quality burdens, while nuclear concentrates its social risk in rare accidents and in waste stewardship; economic — the capital-heavy options (nuclear, and renewables per MWh delivered) have almost no fuel exposure, while gas is cheap to build but carries the highest, most volatile fuel bill. Considering upstream processes and the triple bottom line: wind, solar, and nuclear are genuinely low-carbon; biomass is only conditionally so and adds local air pollution; gas is lowest-capital but a fossil source.
