23-CS-3 Sustainability, Engineering and the Environment · December 2015
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — December 2015 — 11-CS-3 Sustainability, Engineering and the Environment. Closed book; approved 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 | Air emissions | Safety & risk | Initial cost | Operating cost |
|---|---|---|---|---|---|
| Natural-gas turbine | L — compact plant; gas wells and pipelines add some upstream land | M — CO₂ about half of coal per kWh, some NOₓ; negligible SO₂ and particulates | L — fire/explosion of flammable gas is well controlled; upstream methane leaks | L — modular, quick to build (lowest $/kW) | M — fuel is the main cost and its price is volatile |
| High-head hydro | H — reservoir floods valleys, habitat and sometimes communities | L — none in operation; some methane from decaying flooded biomass | M — dam failure is rare but catastrophic downstream; fish passage | H — dam, tunnels, penstocks and long transmission lines | L — no fuel, long life, little staffing |
| Nuclear | L — compact site (plus exclusion zone and mining) | L — no combustion emissions in operation | H — low-probability/high-consequence accidents, long-lived radioactive waste | H — very high capital, long licensing and build | M — cheap fuel, but large staff, security and waste/decommissioning funds |
| Solar PV | H — low power density; large area for utility-scale arrays (rooftops avoid it) | L — none in operation; emissions only in panel manufacture | L — few hazards; end-of-life panel waste | M — module prices falling, still significant per kW of firm output | L — no fuel, minimal maintenance |
| Wind | M — turbines spread over a wide area, but land between them stays farmed | L — none in operation | L — rare blade/ice throw; bird and bat collisions | M — turbines, foundations and grid connection | L — no fuel; routine maintenance only |
Natural-gas turbine: compact; emits CO₂ (about half of coal) with low other pollutants; low, well-controlled fire/explosion risk; the lowest capital cost per kW but an ongoing, volatile fuel cost. High-head hydro: floods large reservoirs; negligible air emissions; dam-failure risk; high capital but very low operating cost. Nuclear: compact; near-zero air emissions; the highest safety concern (radioactive-waste storage and low-probability/high-consequence accidents); very high capital, moderate operating cost. Solar PV: needs significant area; negligible operating emissions; low risk; medium capital and very low operating cost. Wind: small footprint but wide spacing; negligible emissions; blade/ice-throw and wildlife risk; medium capital and very low operating cost. The pattern: fossil gas has low capital but fuel cost and CO₂; the low-carbon options (hydro, nuclear, solar, wind) have higher capital but low operating cost, differing mainly in land use and risk profile.
