Key term
CCEA A-Level Environmental Technology 3930
Fossil Fuels
Global Action on Energy Conservation and Climate Change
Macrogeneration
Microgeneration
Energy From Wind
Topic overviewHorizontal and vertical axis wind turbinesKinetic energy, wind power and the Betz limitPower curves, rated output and energy lossesSwept area, blade length and turbine massAir density, hub height and turbine sitingPower control, yawing and survival speedChoosing a location for a commercial wind farm
Energy From the Sun
Topic overviewSolar radiation, tracking and concentrating solar powerFlat plate and evacuated tube collectorsSizing a domestic solar thermal systemPhotovoltaic cells and semiconductor wafersTypes of photovoltaic module comparedPlanning regulations and solar incentivesPassive solar design in new and existing buildings
Energy From Biomass
Energy Storage
Plastics for the Future
Topic overviewCrude oil as a fuel and a feedstockRefinery gases and the making of polymersPersistent plastic waste and the Great Pacific Garbage PatchToxic gases from incinerating plasticsBiodegradable, photodegradable and compostable plasticsTesting photodegradable plastic against polytheneBio-derived polyethylene and a sustainable plastics future
Renewable Energy Investigations
Sustainable Development
Waste Management
Waste to Energy Technologies
Land Contamination and Remediation
Topic overviewContaminated land, risk and traditional remediationBioremediation principles and bioreactor systemsMicro-organisms that degrade named pollutantsBioremediation benefits and genetically engineered microbesPhytoremediation of metals and other elementsPhytoextraction with Indian mustard and alpine pennycressBiohydrometallurgy and phytomining of ores
Hydrogen Fuel Cells
Transport System Challenges
Energy Performance of Buildings
Emerging Technologies
Sustainable Urban and Rural Communities
The Code for Sustainable Homes
Topic overviewPurpose, levels and assessment of the CodeEnergy, carbon dioxide and water categoriesMaterials, surface water run-off and waste categoriesPollution, health and wellbeing, management and ecology categoriesMeasuring the performance of an existing buildingPerformance profiles, improvements and evaluation
Macrogeneration
Combined heat and power
- 3 things to know
- AS 1
Overview
How CHP recovers waste heat, efficiency calculations against separate generation, district heating, suitable sites and fuels, heat-led operation, carbon savings, limitations and trigeneration.
What you need to know
Answer each one before you reveal it.
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Key term
How does combined heat and power improve on a traditional power station?
Key term
How do the efficiencies of CHP and conventional generation compare?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is combined heat and power (CHP)?
Model answer
Combined heat and power, or cogeneration, is the generation of electricity and useful heat from the same fuel in one plant. The heat a conventional station would waste is captured for use.
- 2
How does combined heat and power improve on a traditional power station?
Model answer
A traditional station discards most of its heat in cooling water and flue gases. A CHP plant uses that heat for buildings or industry, so far more of the fuel's energy is useful.
- 3
How do the efficiencies of CHP and conventional generation compare?
Model answer
A conventional fossil fuel power station is typically 35% to 50% efficient. A CHP plant can use 80% or more of its fuel's energy as electricity and heat together.
- 4
A CHP plant uses 10 MW of fuel to produce 3.5 MW of electricity and 4.5 MW of useful heat. Calculate its overall efficiency.
Model answer
The overall efficiency is 80%. The working is (3.5 + 4.5) ÷ 10 × 100 = 80%.
- 5
Producing 3.5 MW of electricity at a 35% efficient power station and 4.5 MW of heat from a 90% efficient boiler needs how much fuel, compared with 10 MW for CHP?
Model answer
Separate production needs 15 MW of fuel, so CHP saves a third. The working is 3.5 ÷ 0.35 = 10 MW plus 4.5 ÷ 0.9 = 5 MW.
- 6
Why must a CHP plant be located close to its heat users?
Model answer
Hot water and steam lose heat and cost a great deal to pipe over long distances. The plant must therefore be near a steady demand for heat.
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