Environmental Technology Systems Awareness Practice Flashcards

Flashcards covering key principles, regulatory requirements, system components, and operational features of environmental technology systems based on the lecture material.

Before considering the installation of environmental technology systems, what two steps must be taken first to improve sustainability?

Approaches to reduce demand for energy and water, and approaches to improve efficiency of energy and water usage must be taken first.

What is the main operational difference between passive and active solar thermal hot water systems?

Passive systems circulate fluid via natural thermosiphon/convection and require the collector to be mounted below the cylinder, whereas active systems use a circulating pump to move the heat transfer fluid.

What is the primary function of a Differential Temperature Controller (DTC) in a solar thermal hot water system?

The DTC monitors high-level and low-level temperature sensors and allows the circulating pump to operate only when solar energy is available and there is a demand for water to be heated.

What are the two main types of solar collectors used in solar thermal hot water systems?

Flat Plate solar collectors and Evacuated Tube solar collectors.

Under Town and Country Planning Regulations in England and Wales, what are the criteria for a stand-alone solar hot water collector array to be classed as permitted development?

The array must be no higher than $4\,m$, sited at least $5\,m$ from boundaries, limited to $9\,m^2$ (or $3\,m$ wide by $3\,m$ deep), not inside a listed building boundary, not visible from the highway in conservation areas, and be the only stand-alone solar unit.

What is the optimum orientation and tilt angle for solar collectors in the UK?

South-facing orientation with a collector tilt of $35^\circ$ (or between $30^\circ$ and $40^\circ$ from horizontal).

How does the mechanical vapour compression cycle (refrigeration cycle) work in a heat pump?

1. Low-temperature heat enters the Evaporator, causing the refrigerant to evaporate. 2. The gaseous refrigerant enters the Compressor, increasing its temperature and pressure. 3. The refrigerant passes through the Condenser, transferring heat to the emitter circuit. 4. The refrigerant passes through the Expansion Valve, reducing its pressure and temperature to start the cycle again.

How is the Coefficient of Performance (COP) of a heat pump calculated?

$$\text{COP} = \frac{\text{Heating Output}}{\text{Electrical Power Input}}$$

How do the flow temperatures of a heat pump system compare to those of a traditional condensing boiler system?

A heat pump operates at a low flow temperature of $30^\circ\text{C}$ to $40^\circ\text{C}$, whereas a traditional condensing boiler operates at a flow temperature of $80^\circ\text{C}$.

Why are standard indirect domestic hot water cylinders unsuitable for heat pump systems, and what design is recommended instead?

Standard indirect cylinders have heat transfer coils that are too small for lower flow temperatures; a 'tank-in-tank' hot water cylinder is recommended because it provides a larger surface-to-surface heat transfer area.

What is the function of a buffer tank in a heat pump heating circuit?

It accumulates and stores heating circuit water to prevent heat pump compressor short-cycling during low heat demand periods and provides heat for defrost cycles in air source units.

Why are biomass fuelled systems considered carbon neutral?

The carbon dioxide released during biomass combustion is equal to the amount of carbon dioxide absorbed from the atmosphere by the plant/tree during its growth via photosynthesis.

What are the three main types of woody biomass fuels and their physical characteristics?

1. Logs: Original biomass fuel from felled timber. 2. Wood Chip: Produced from small round-wood or reclaimed timber. 3. Pellets: Compressed sawdust particles forming cylinders $6\,mm$ or $8\,mm$ in diameter and $15\text{--}30\,mm$ long.

Under the Clean Air Act, what requirement must a biomass appliance satisfy to be installed in a Smoke Control Area?

The appliance must be designated as an 'exempted appliance' by the Department for Environment, Food and Rural Affairs (DEFRA).

What is the function of an inverter in an 'on-grid' solar photovoltaic (PV) system?

It converts direct current (d.c.) electricity produced by the solar PV module array into alternating current (a.c.) electricity suitable for home usage and grid export.

What minimum roof/mounting area is typically required for every kilowatt peak ($1\,kWp$) of solar photovoltaic generation capacity?

A minimum of $8\,m^2$ of suitable array mounting area is required per $1\,kWp$.

What are the two main types of micro-wind turbines based on their rotational axis?

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

What are the minimum viable wind speed and the ideal wind speed range for a micro-wind turbine?

The minimum viable wind speed is $5\,m/s$, and the ideal average wind speed range is $10\text{--}14\,m/s$.

To minimize wind turbulence, at what distance from an obstruction should a micro-wind turbine ideally be mounted?

At a distance equal to at least $10 \times H$, where $H$ is the height of the nearest obstruction.

In a micro-hydropower system, what do the terms 'head' and 'penstock' refer to?

'Head' is the vertical distance between the intake water level and the turbine, while the 'penstock' is the pipe that conveys water from the inlet to the turbine.

What is the fundamental difference between impulse and reaction water turbines in micro-hydropower?

In an impulse turbine, the runner operates in air and is turned by high-velocity water jets; in a reaction turbine, the runner is fully immersed in water and turns due to pressure and flow differential.

What regulatory licence from the Environment Agency is required if water is diverted away from the main line of flow of a river for a hydropower scheme?

An Abstraction Licence.

What does the term 'heat-led' mean in a micro-combined heat and power (mCHP) system?

It means the unit generates electricity as a byproduct only when responding to a demand for space heating or hot water, with approximately $80\%$ of energy output as heat and $15\%$ as electricity.

Under the Water Supply (Water Fittings) Regulations 1999, what risk category is assigned to harvested rainwater and greywater, and what are its permitted uses?

It is classified as Class 5 Risk; permitted non-wholesome uses include WC flushing, clothes washing machines, garden irrigation, and car washing.

What backflow prevention device is required on the wholesome back-up water supply to an intermediate storage cistern in a rainwater harvesting system?

A Type AA air gap.

Why must untreated greywater never be stored for longer than a few hours?

Because greywater contains human bacteria, organic matter, soap residues, and nutrients at warm temperatures, which causes rapid bacterial growth and contamination if left untreated.