2023 CCEA AS-Level Environmental Technology 3930 Practice Paper with Answers

The three '20-20-20' targets were: a 20% reduction in EU greenhouse gas emissions from 1990 levels; 20% of EU energy consumption to come from renewable sources; and a 20% improvement in energy efficiency, all by 2020.

[1] mark for each correctly stated target, up to a maximum of [2]. Accept any two of: 20% cut in greenhouse gas emissions (from 1990 levels); 20% of energy from renewables; 20% improvement in energy efficiency.

The Intergovernmental Panel on Climate Change (IPCC).

[1] for correctly naming the IPCC (Intergovernmental Panel on Climate Change).

Carbon trading (an emissions trading scheme).

[1] for correctly stating 'carbon trading' (or 'emissions trading').

Horizontal Axis Wind Turbine (HAWT) and Vertical Axis Wind Turbine (VAWT).

[1] for Horizontal Axis Wind Turbine (HAWT); [1] for Vertical Axis Wind Turbine (VAWT). Abbreviation or full name accepted for each mark.

Solar photovoltaic (PV) and (small-scale/domestic) wind turbines.

[1] mark for each correctly named microelectricity technology, up to a maximum of [2]. Accept: solar PV; wind.

The condenser.

[1] for correctly naming the condenser.

Compressed Air Energy Storage (CAES) and pumped hydro (pumped hydroelectric storage).

[1] mark for each correctly named energy storage technology, up to a maximum of [2]. Accept: CAES (Compressed Air Energy Storage); pumped hydro.

Solar thermal and solar photovoltaic (PV).

[1] mark for each correctly named approach, up to a maximum of [2]. Accept: solar thermal; solar PV.

Any one of: monocrystalline, polycrystalline, thick-film, or thin-film.

[1] for correctly naming any one of: monocrystalline; polycrystalline; thick-film; thin-film.

Sustainable development, as defined by the Brundtland Commission, is development that meets the needs of the present without compromising the ability of future generations to meet their own needs. This concept is important when planning national energy policy because it encourages governments to prioritise renewable energy sources and reduce reliance on finite fossil fuels, ensuring that energy resources and a stable climate remain available for future generations, rather than being depleted or damaged to meet only current demand.

[1]-[2] for a correct definition of sustainable development (in line with the Brundtland Commission definition); [1]-[2] for a valid explanation of why the concept matters for energy policy (e.g. protecting resources/climate for future generations; driving the shift to renewables). Maximum [4].

Nuclear fuel (uranium) has a very high energy density compared with fossil fuels, meaning that a relatively small mass of fuel can release a very large amount of energy. This allows nuclear power stations to generate large, reliable quantities of electricity from a comparatively small amount of fuel and infrastructure, providing a stable 'baseload' supply that does not depend on weather conditions, unlike many renewable sources. Unlike fossil fuels, nuclear power generation produces no direct carbon dioxide emissions during operation, which supports efforts to meet climate change and energy conservation targets. However, nuclear power also raises significant concerns, including the safe long-term disposal of radioactive waste, plant safety, and very high construction and decommissioning costs, which is why opinions on its overall viability remain divided.

[1] for identifying that nuclear fuel has a high energy density; [1] for explaining what this means in practice (large energy output from small fuel mass); [1] for a valid benefit (e.g. reliable/baseload supply, or low direct CO2 emissions); [1] for a further valid benefit or point of comparison; [1] for a valid limitation/concern (e.g. waste disposal, safety, cost), showing balanced discussion. Maximum [5].

The Betz Limit is the theoretical maximum efficiency (approximately 59.3%) with which a wind turbine can extract kinetic energy from the wind passing through its rotor swept area; it is not possible to extract 100% of the wind's energy, as some kinetic energy must remain in the air for it to continue moving away from the turbine. In practice, real-world wind turbines always achieve a power efficiency below the Betz Limit, because of additional mechanical, electrical and aerodynamic losses (for example friction in the gearbox/bearings, generator inefficiency, and imperfect blade aerodynamics), so the actual electrical power output is always less than the Betz Limit alone would suggest is possible.

[1]-[2] for a correct definition of the Betz Limit, including the approximate value (~59.3%) and/or the idea of a theoretical maximum extractable proportion of wind energy; [1]-[2] for correctly explaining that real turbines fall short of this limit due to real-world losses (mechanical, electrical, aerodynamic). Maximum [4].

In the evaporator, a refrigerant fluid circulating through a buried ground loop absorbs low-grade heat from the ground and evaporates into a low-pressure gas. This gas passes to the compressor, which compresses it, raising both its pressure and temperature significantly. The hot, high-pressure gas then passes through the condenser, where it releases its heat into the building's heating system (for example, underfloor heating or radiators), and in doing so condenses back into a liquid. Finally, the expansion valve reduces the pressure of the liquid refrigerant, cooling it further, before it returns to the evaporator to repeat the cycle.

[1] for correctly describing the role of the evaporator (absorbing heat from the ground); [1] for the compressor (raising pressure/temperature of the refrigerant gas); [1] for the condenser (releasing heat into the building, refrigerant condenses); [1] for the expansion valve (reducing pressure/cooling refrigerant before the cycle repeats). Maximum [4].

1. Microgeneration reduces energy costs for the household or community, as some or all of their electricity or heat is generated on-site, lowering their reliance on, and bills from, energy suppliers.
2. Microgeneration enhances the security of energy supply, as the household or community becomes less dependent on the National Grid or centralised power generation, and may also benefit from government financial incentives while contributing towards national and international environmental targets.

For each of the two points: [1] basic identification of a benefit; [2] competent explanation of that benefit. Maximum [4] (2 x [2]). Accept other valid benefits (e.g. reduced carbon footprint; increased public awareness of energy use).

Renewable energy sources such as wind, wave, solar and tidal are not always reliable or available on demand; their output is intermittent, depending on factors such as weather conditions and time of day. Energy storage facilities allow surplus energy generated at times of high renewable output (for example, on a very windy or sunny day) to be stored, and then released at times when renewable output is low or when demand for electricity is high, helping to balance overall electricity supply and demand across the grid.

[1]-[2] for explaining the problem of intermittency/unreliability of renewable sources; [1]-[2] for explaining how storage addresses this (storing surplus, releasing when needed, balancing supply and demand). Maximum [4].

Pumped hydro energy storage uses two water reservoirs at different heights (an upper and a lower reservoir). At times when there is a surplus of (renewable) electricity available, this electricity is used to power pumps that move water from the lower reservoir up to the higher reservoir, storing the energy as gravitational potential energy. When electricity is needed, for example at times of high demand or low renewable output, the stored water is released from the upper reservoir and allowed to flow back downhill through a turbine, which is coupled to a generator, converting the potential energy back into electrical energy.

[1] for identifying two reservoirs at different heights; [1]-[2] for correctly explaining the pumping/storage phase (surplus electricity used to pump water uphill, storing energy as potential energy); [1]-[2] for correctly explaining the generation phase (water released downhill through a turbine/generator to produce electricity when needed). Maximum [5].

A photovoltaic (PV) cell is made from thin wafers of semiconductor material, typically silicon, arranged as two layers with different electrical properties (a p-type layer and an n-type layer), which together form a junction. When sunlight (photons) strikes the semiconductor wafer, it transfers energy to electrons within the material, exciting them and causing them to move across the junction. This movement of electrons creates a flow of direct current (DC) electricity, which is collected by metal contacts on the surface of the cell and can then be used or converted (via an inverter) for use in the home or exported to the grid.

[1]-[2] for correctly describing the composition/structure of a PV cell (semiconductor wafers, typically silicon, p-type and n-type layers/junction); [1]-[2] for correctly explaining the role of the semiconductor in generating electricity (sunlight excites electrons, creating a flow of current). Maximum [4].

R/P ratio = reserves ÷ annual consumption rate = 5.4 ÷ 0.36 = 15 years.

[1] for correctly identifying the calculation as reserves divided by annual consumption; [1] for correct substitution (5.4 ÷ 0.36); [1] for the correct final answer, 15 years.

\( E_k = \frac{1}{2}mv^2 = \frac{1}{2}(250)(12)^2 = \frac{1}{2}(250)(144) = 18\,000 \) J.

[1] for correct substitution into the formula; [1] for correctly squaring the velocity (12² = 144); [1] for the correct final answer, 18 000 J.

\( A = \pi r^2 = \pi (15)^2 = \pi (225) = 706.858\ldots \approx 707 \) m\(^2\) (3 s.f.).

[1] for correct substitution into the formula; [1] for correctly squaring the radius (15² = 225); [1] for the correct final answer, 707 m² (3 s.f.).

\( \text{COP} = \dfrac{\text{heat output}}{\text{work input}} = \dfrac{8}{2} = 4 \).

[1] for correctly identifying the values to substitute; [1] for correct substitution into the formula; [1] for the correct final answer, COP = 4.

Global reliance on plastics manufactured from crude oil raises serious environmental issues. Crude oil is used both as a fuel source and as an industrial feedstock, and plastic production is now the largest single user of crude oil outside the energy and transport sectors, with global plastic production continuing to increase year on year. During oil refining, the gases formed by fractional distillation are cooled, liquefied and stored to be used as feedstocks in plastics manufacture. The pollution problems associated with conventional plastics fall into two main areas. Firstly, most polymers and plastics made from crude oil derivatives cannot be broken down by micro-organisms and are not easily recycled; this has led to serious environmental problems such as the accumulation of plastic waste in the oceans, exemplified by the Great Pacific Garbage Patch. Secondly, when plastic waste is incinerated, toxic gases such as carbon monoxide, hydrogen cyanide and hydrochloric acid can be released, posing risks to air quality and human health.

In response to these issues, industrial approaches are being developed to manufacture more sustainable plastics. Additives can be incorporated into the polymer during manufacture specifically to enhance its biodegradability, causing the plastic to break down more readily once discarded. Manufacturing processes can also be modified to enhance thermal and photodegradation, so that plastics used for products such as agricultural films, packaging and labelling break down more quickly than conventional polythene when exposed to heat, light or the environment after use. Compostable plastics are also being developed, which can be broken down and used to improve soil composition, which is particularly useful in regions where soil structure is otherwise poor. Additionally, industry has developed bioderived polyethylene (BPE), a recyclable plastic manufactured using renewable, plant-based feedstocks rather than crude oil, reducing the dependence on finite fossil fuel resources for plastic production while still producing a fully recyclable material.

A range of experimental methods can be used to test and compare the properties of biodegradable/photodegradable plastics against conventional polythene. The degradability of samples of photodegradable plastic and ordinary polythene can be compared by placing samples in a propagator fitted with ultraviolet (UV) bulbs, which simulate the effect of prolonged sunlight exposure, and observing and recording the rate and extent to which each sample visibly breaks down over a set period of time. In addition, the tensile strength of the two types of plastic sample can be compared using a simple Newton meter, by measuring the force required to stretch or break each sample before and after UV exposure; a marked reduction in tensile strength after exposure provides evidence of the effectiveness of the photodegradation process. Taken together, these experimental comparisons allow manufacturers and researchers to evaluate how effectively a new plastic formulation degrades and how its mechanical properties change over time, supporting the assessment of the need for a global move towards more sustainable manufacture and use of plastics.

Level-of-response mark scheme (15 marks):
Level 1 [1]-[5]: Limited or partial grasp of the topic; minimal use of scientific/specialist terminology; addresses at most one bullet point in any detail; basic syntax and QWC.
Level 2 [6]-[10]: Competent understanding of two or three bullet points, though possibly uneven in depth; satisfactory use of technical vocabulary (e.g. feedstock, biodegradable, photodegradable, BPE); generally clear structure and QWC.
Level 3 [11]-[15]: Comprehensive coverage of all three bullet points (environmental issues of crude-oil plastics; industrial sustainable manufacturing approaches; experimental testing methods); strong, accurate use of specialist vocabulary; excellent structure, syntax and QWC throughout.