Renewable and Low-Carbon Energy Technologies
Domain 3 tests technology selection and realistic yield, not enthusiasm. You should be able to estimate annual generation, compare capacity factor with efficiency, explain grid integration and place a project within Hong Kong’s decarbonisation policy.
Core rules
- PV is rated in kWp under standard test conditions. Annual yield ≈ kWp × specific yield (kWh/kWp), where specific yield already reflects irradiance, tilt, shading, temperature and inverter losses. In Hong Kong, a well-oriented rooftop system typically yields around 1,000–1,150 kWh/kWp per year; performance ratio is commonly 0.75–0.85.
- Wind power in the resource is 0.5ρAv³. Betz’s limit is 59.3%; real capacity factors are roughly 25–35% onshore and 35–50% offshore. Wind and solar are variable, so grid codes, forecasting, storage and curtailment rules matter.
- Waste-to-energy recovers energy from municipal solid waste but is not zero-carbon: plastics are fossil-derived, and emissions and residue must be managed. Biomass carbon neutrality depends on sustainable sourcing.
- Battery storage is rated in MW and MWh; round-trip efficiency is typically 85–90%, and degradation, cycling and fire safety affect the business case.
- Hong Kong’s Climate Action Plan 2050 targets carbon neutrality by 2050, coal phase-out by 2035 and renewable energy at 7.5–10% of electricity by 2035. The Feed-in Tariff scheme, launched in 2018, pays eligible renewable generators; Renewable Energy Certificates are a separate market instrument.
Worked example
A 10 kWp rooftop PV array has a specific yield of 1,100 kWh/kWp. Annual generation = 11,000 kWh. At a FiT rate of HK$5/kWh, revenue = HK$55,000/year. If installed cost is HK$150,000, simple payback = 150,000/55,000 = 2.7 years, before maintenance, inverter replacement and degradation. If the tariff were HK$3/kWh, payback would stretch to 4.5 years - a reminder that policy, not physics alone, drives the case.
Traps
Confusing kWp with kWh; multiplying rated power by 8,760 hours; treating capacity factor as efficiency; ignoring shading and soiling; assuming FiT eligibility without grid connection and registration; and describing WtE as carbon-neutral.