2025 CCEA AS-Level Environmental Technology 3930 Practice Paper with Answers

Renewable sources can generate electricity either directly (wind, hydroelectric, wave and tidal, where the moving resource drives a turbine directly) or indirectly (solar photovoltaic and biomass, where sunlight or fuel must first be converted into another form of energy before a turbine or cell generates electricity). The two indirect sources are solar (photovoltaic) and biomass.

[1] mark for each correct indirect source named, up to [2]. Award: solar / solar PV [1]; biomass [1]. Reject wind, hydroelectric, wave or tidal (these are direct sources). All other valid indirect sources given credit.

Fast-growing energy crops are grown specifically for biomass fuel production. Examples include willow, poplar, elephant grass, maize and sugar cane. Any two of these crops is a correct answer.

[1] mark for each correctly named crop, up to [2]. Accept: willow; poplar; elephant grass; maize; sugar cane. All other valid biomass energy crops given credit.

Biomass is categorised into: organic materials, wood, agricultural crops, and agricultural and municipal wastes. Excluding wood, the remaining valid categories are organic materials, agricultural crops, and agricultural and municipal wastes.

[1] mark for each correct category, up to [2]. Accept: organic materials [1]; agricultural crops [1]; agricultural and municipal wastes [1] (any two). Reject wood (excluded by the question).

Solar collectors harness the Sun's energy using two main approaches: solar thermal collectors, which absorb radiation to heat a fluid, and photovoltaic (PV) collectors, which use a semiconductor wafer to convert sunlight directly into electricity.

[1] mark for solar thermal; [1] mark for photovoltaic / PV. Total [2].

The EU's 2020 climate and energy targets (the '20-20-20' targets) set three headline goals to be reached by 2020: (1) a 20% reduction in greenhouse gas emissions compared with 1990 levels; (2) raising the share of EU energy consumption produced from renewable sources to 20%; (3) a 20% improvement in energy efficiency. Any two of these three targets is a correct answer.

[1] mark for each correctly stated target, up to [2]. Accept: 20% reduction in greenhouse gas emissions (from 1990 levels); 20% of energy from renewables; 20% improvement in energy efficiency. Accept approximate figures if the correct focus (emissions / renewables / efficiency) is identified.

Microgeneration technologies are divided into microelectricity technologies (solar PV, wind) and microheat technologies (solar thermal, ground source heat pumps and biomass heating). Any two of solar thermal, ground source heat pumps or biomass is correct.

[1] mark for each correct microheat technology, up to [2]. Accept: solar thermal; ground source heat pumps; biomass (biomass boilers/stoves). Reject solar PV and wind (these are microelectricity, not microheat, technologies).

Anaerobic digestion is the biological breakdown of organic matter in the absence of oxygen. Step 1: Organic waste (for example food waste, animal slurry or crop residues) is fed into a sealed digester tank. Step 2: The sealed tank excludes oxygen, creating anaerobic conditions. Step 3: Micro-organisms (bacteria) within the digester break down the organic matter over several weeks. Step 4: This breakdown releases biogas, a mixture primarily of methane and carbon dioxide, which rises and is collected from the top of the digester. Step 5: The biogas is used as a fuel (for heating or electricity generation) and the remaining solid/liquid residue (digestate) can be used as a fertiliser. Final answer: anaerobic digestion converts organic waste into methane/carbon-dioxide-rich biogas via oxygen-free bacterial breakdown in a sealed digester.

1 mark per valid step, up to [4]: waste/organic matter loaded into a sealed digester [1]; absence of oxygen (anaerobic conditions) [1]; bacterial/microbial breakdown of organic matter [1]; biogas (methane and carbon dioxide) produced and collected [1]. Credit also given for mention of digestate as a by-product if a step mark is otherwise missing. All other valid points given credit.

Step 1: A sugar-rich biomass crop, such as sugar cane, is harvested and its sugars are fermented by micro-organisms to produce bioethanol (rather than using crude oil as the starting feedstock). Step 2: The bioethanol is dehydrated (water is removed) to produce bioethylene gas. Step 3: The bioethylene molecules are polymerised (joined together into long chains) to form bioderived polyethylene (BPE). Step 4: Because BPE has the same chemical structure as conventional, crude-oil-derived polyethylene, it can be processed, used and recycled using the same existing plastics infrastructure. Final answer: BPE is manufactured by fermenting biomass sugars to bioethanol, dehydrating this to bioethylene, then polymerising the bioethylene to form a fully recyclable polyethylene that is chemically identical to conventional polyethylene but derived from a renewable feedstock rather than crude oil.

1 mark per valid step, up to [5]: biomass/plant sugar (e.g. sugar cane) used as the renewable feedstock, not crude oil [1]; fermentation of sugars to produce bioethanol [1]; dehydration of bioethanol to produce bioethylene [1]; polymerisation of bioethylene to form polyethylene (BPE) [1]; resulting BPE is chemically identical to / as recyclable as conventional polyethylene, reducing crude oil dependency [1]. All other valid points given credit.

Point 1: Conventional plastics made from crude oil derivatives cannot be broken down by micro-organisms or easily recycled. Impact: this causes plastic waste to persist in the environment for centuries, accumulating in natural habitats such as the ocean (for example the Great Pacific Garbage Patch). Point 2: Plastic production is the largest single user of crude oil outside the energy and transport sectors, and global plastic production continues to increase each year. Impact: this accelerates the depletion of a finite crude oil resource and increases reliance on an unsustainable raw material. Point 3: Incinerating plastic waste releases toxic gases such as carbon monoxide, hydrogen cyanide and hydrochloric acid. Impact: these gases reduce air quality and pose a health hazard to humans and wildlife. Together, these three issues (persistence/non-biodegradability, resource depletion, and toxic incineration by-products) justify the case for developing biodegradable, photodegradable and bioderived plastics.

3 numbered slots, [2] marks each: [1] for identifying a valid issue + [1] for a correct linked impact/consequence. Slot 1: non-biodegradability/cannot be recycled easily [1] + persists in the environment / accumulates as waste e.g. ocean garbage patches [1]. Slot 2: plastic production is the largest non-energy/transport user of crude oil and is increasing [1] + depletes a finite resource [1]. Slot 3: incineration releases toxic gases (CO, HCN, HCl) [1] + harms air quality/health [1]. Maximum [6]. All other relevant, valid responses given credit.

Point 1: A smart grid can dynamically balance supply and demand in real time. Impact: this makes it easier to incorporate intermittent, weather-dependent renewable electricity (from wind and solar) into the network without destabilising the supply. Point 2: Interconnections allow electricity to be traded and shared between Ireland, the UK and mainland Europe. Impact: this improves the security of electricity supply, since a shortfall in one region can be met by surplus generation in another, reducing reliance on fossil-fuel back-up plants. Point 3: A smarter, better-connected grid can route electricity more efficiently over shorter or more optimal paths. Impact: this reduces transmission losses and long-term distribution costs, and lowers associated carbon emissions.

3 numbered slots, [2] marks each: [1] for a valid benefit + [1] for a correct explanation/impact. Slot 1: enables greater integration of intermittent renewable sources (wind/solar) [1] + balances variable supply with demand in real time [1]. Slot 2: electricity trading/sharing across interconnected countries [1] + improves security/reliability of supply [1]. Slot 3: more efficient distribution/reduced transmission losses [1] + lower long-term costs and carbon emissions [1]. Maximum [6]. All other relevant, valid responses given credit.

Point 1: Under a carbon trading (cap-and-trade) scheme, a company that reduces its emissions below its permitted allowance can sell its surplus allowances to other companies. Impact: this creates a direct financial incentive for companies to invest in cleaner technology and reduce emissions further than required. Point 2: A company that exceeds its allocated emissions cap must purchase additional allowances on the carbon market. Impact: this increases the company's operating costs, which should encourage it to reduce emissions to avoid future costs. Point 3: If regulators set the overall emissions cap too high, or allocate too many free allowances, the price of carbon on the market falls. Impact: a low carbon price provides little financial incentive to reduce emissions, which can undermine the overall effectiveness of the scheme in cutting global carbon output.

3 numbered slots, [2] marks each: [1] identification + [1] linked impact. Slot 1: surplus allowances can be sold [1] + financial incentive to cut emissions/invest in clean technology [1]. Slot 2: excess emissions require purchasing extra allowances [1] + raises costs, encouraging reduction [1]. Slot 3: over-allocation of allowances lowers carbon price [1] + weakens the incentive to reduce emissions, limiting scheme effectiveness [1]. Maximum [6]. All other relevant, valid responses given credit.

Point 1: Microgeneration technologies (such as solar PV or ground source heat pumps) allow a household to generate some or all of its own heat and electricity. Impact: this reduces the household's reliance on grid-supplied energy, lowering ongoing energy bills once installation costs are recovered. Point 2: Widespread adoption of microgeneration increases the overall proportion of energy produced from renewable, low-carbon sources. Impact: this helps homes and communities contribute towards national and international renewable energy and emissions-reduction targets. Point 3: Households that generate more electricity than they use can sell the surplus back to energy suppliers. Impact: this provides a financial incentive/income stream that improves the economic case for installing microgeneration technology.

3 numbered slots, [2] marks each: [1] identification + [1] explanation. Slot 1: reduced energy costs/bills [1] + less reliance on grid-supplied energy [1]. Slot 2: contribution to environmental/renewable energy targets [1] + reduces overall carbon emissions [1]. Slot 3: financial incentives (e.g. selling surplus electricity) [1] + improves economic viability of installation [1]. Maximum [6]. Enhanced security of supply also acceptable as a valid point. All other relevant, valid responses given credit.

(i) Evaporator: the low-pressure liquid refrigerant absorbs heat energy from the surrounding ground (via a ground loop) and evaporates, changing state from a liquid to a gas. (ii) Compressor: the low-pressure refrigerant gas is compressed, which increases both its pressure and its temperature. (iii) Condenser: the hot, high-pressure refrigerant gas passes through the condenser, where it releases its heat energy into the building's heating/hot water system and condenses back into a liquid. (iv) Expansion valve: the high-pressure liquid refrigerant passes through the expansion valve, which reduces its pressure (and therefore its temperature), preparing it to absorb heat again at the evaporator, completing the cycle.

[1] mark for each correctly described function, up to [4]. (i) absorbs heat from the ground, refrigerant evaporates to a gas [1]. (ii) compresses the gas, raising its pressure/temperature [1]. (iii) refrigerant condenses to a liquid, releasing heat to the building [1]. (iv) reduces the pressure/temperature of the liquid refrigerant before it re-enters the evaporator [1]. Accept equivalent correct descriptions referencing state change and heat transfer direction.

(i) Gasification converts biomass into a mixture of carbon monoxide and hydrogen, commonly known as syngas. (ii) Syngas can be used as a fuel source, for example burned to generate heat or electricity, or used as a chemical feedstock. (iii) The oxygen supply is deliberately limited so that the biomass does not fully combust to carbon dioxide and water (as in ordinary burning); instead, the restricted oxygen causes partial oxidation, converting the carbon and hydrogen in the biomass into the combustible gases carbon monoxide and hydrogen (syngas), which retain more of the original chemical energy in a usable gaseous fuel.

(i) [1] carbon monoxide + [1] hydrogen (both required for [2]). (ii) [1] for any valid use, e.g. fuel for heat/electricity generation, or chemical feedstock. (iii) [1] for identifying that limited oxygen prevents full combustion / causes partial oxidation, producing a combustible gas rather than being fully burned to carbon dioxide and water. Maximum [4].

(a) Method: total energy = sum of the power readings x the 3-hour interval. Substitution: Total energy = (0+0+20+140+220+180+40+0) W x 3 h = 600 W x 3 h = 1800 Wh. Converting to kWh: 1800 Wh / 1000 = 1.8 kWh. Final answer: the panel generates approximately 1.8 kWh over the summer day.

(b) Applying the same method to the winter data: Total energy = (0+0+5+40+70+50+10+0) W x 3 h = 175 W x 3 h = 525 Wh = 0.525 kWh. The summer total (1.8 kWh) is more than three times the winter total (0.525 kWh). Reason 1: the summer day has a longer period of daylight (non-zero readings persist from 06:00 to 18:00, compared with the same shorter window but far lower peak in winter), so the panel generates electricity for more hours. Reason 2: summer sunlight is more intense, because the Sun is higher in the sky (greater solar irradiance per unit panel area) and the overcast winter sky scatters and absorbs a large proportion of incoming radiation before it reaches the panel, reducing the light intensity available for conversion to electricity.

(a) [1] for correct method (sum of readings x time interval); [1] for correct substitution/working (600 W x 3 h = 1800 Wh); [1] for correct final answer with correct unit (1.8 kWh). Error carried forward applies if an arithmetic slip is made but the method is correct. (b) [1] mark for correctly identifying summer output is greater (with a supporting figure/comparison); up to [3] further marks for two valid, distinct explanatory reasons properly linked to intensity/duration of sunlight (e.g. longer daylight hours in summer [1]-[2]; higher sun angle/greater irradiance in summer [1]; cloud cover in winter scatters/absorbs sunlight, reducing intensity [1]). Maximum [4] for part (b). All other relevant, valid responses given credit.

A high-scoring answer addresses all three bullet points with accurate technical detail and reaches a justified overall conclusion.

Technical factors: the energy available to a turbine increases with the cube of wind speed (since kinetic energy = ½mv² and mass flow rate itself increases with wind speed), so site selection strongly favours locations with consistently high average wind speeds. Power output also increases with the swept area of the rotor (area = πr²), so larger rotor diameters capture more energy, though the Betz limit means no turbine can ever convert more than a theoretical maximum fraction of the wind's kinetic energy into electricity, and real turbines fall further short of this due to mechanical and electrical losses (the gap between 'rotor collected energy' and 'rated energy output'). Hub height must balance access to stronger, less turbulent wind higher above ground level against practical constraints such as terrain, turbine size and visual impact.

Environmental and social impacts: wind turbines produce no direct greenhouse gas emissions during operation, but their construction, the access roads required, and their presence can affect local habitats and biodiversity (for example bird and bat populations). Local communities may raise objections relating to visual impact on the landscape, noise from the rotating blades, and shadow flicker, although community-scale projects can also bring direct local benefit through community ownership schemes, lease payments to landowners, and local jobs.

Cost-effectiveness and reliability: wind turbines have relatively high upfront capital costs but low ongoing fuel costs (the wind itself is free), giving good long-term cost-effectiveness once installed, particularly at well-sited locations. However, wind is intermittent and unreliable on a short-term basis, meaning output varies significantly with weather conditions and cannot be guaranteed at any given moment, unlike biomass (which can be stored and burned on demand) though wind compares favourably with solar in Northern Ireland's often overcast, low-daylight climate for maximising annual output, particularly given the region's characteristically strong and consistent wind resource.

Conclusion: for a rural Northern Ireland community with access to a suitably windy, appropriately sited location, wind energy is a strong candidate for large-scale renewable electricity generation, particularly when its cost-effectiveness and lack of ongoing fuel costs are weighed against its intermittency, provided environmental and social concerns are properly assessed and mitigated during planning.

Levels of Response (15 marks total), assessing technical accuracy, breadth across all three bullet points, and quality of written communication (spelling, punctuation, grammar and specialist terminology).

Level 1 (Basic) [1]-[5]: Limited, undeveloped or one-sided response; may address only one bullet point; little or no accurate technical detail (e.g. no reference to wind speed, swept area or intermittency); weak use of specialist vocabulary; some errors in spelling/grammar that hinder meaning.

Level 2 (Adequate) [6]-[10]: Addresses at least two of the three bullet points with reasonable accuracy; some relevant technical detail (e.g. correct general link between wind speed and energy output, or a valid environmental/social impact); developing but not fully balanced argument; generally accurate specialist vocabulary with minor errors.

Level 3 (Excellent) [11]-[15]: Addresses all three bullet points in a well-balanced, developed discussion; accurate technical detail (e.g. correct reference to ½mv², πr², the Betz limit, or rotor-collected vs rated energy); clear evaluation of environmental/social trade-offs and of cost-effectiveness/reliability relative to other renewables; reaches a justified overall conclusion; wide range of accurate specialist vocabulary; clear coherence, spelling, punctuation and grammar throughout.