Module 4 Unit 1 Quiz

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Question 1 of 20

1. Question
Which statement best explains why district-heating networks are moving towards lower temperatures?
- Lower temperatures help reduce pump electricity consumption because water moves more easily at cooler temperatures.
- Lower temperatures can reduce distribution losses and make renewable, recovered and environmental heat easier to use.
- Lower temperatures are needed to prevent corrosion in steel pipes and extend the lifetime of district‑heating networks.
- Lower temperatures allow heat to be delivered to buildings more quickly because cooler water transfers heat faster.
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Question 2 of 20

2. Question
In a district-heating network, what is the return temperature?
- The temperature of the water entering the consumer’s heat exchanger before any heat is extracted.
- The temperature of the water in the network after it has been reheated at the plant and is ready for distribution.
- The temperature measured in the circulation loop inside the building before mixing valves adjust it for heating.
- The temperature of the network water after heat has been transferred and it flows back from consumers.
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Question 3 of 20

3. Question
Why is a very small temperature difference between supply and return (low Delta-T) usually a problem?
- A low Delta‑T indicates that the heat exchanger is transferring heat too efficiently, which can cause overheating in the building.
- A small temperature difference reduces thermal stress in pipes, which can lead to slower heat delivery to consumers.
- Low Delta‑T increases required flow, pumping demand and may limit network capacity.
- Low Delta‑T means the supply temperature is too low for modern radiators, so the network must increase boiler output to compensate.
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Question 4 of 20

4. Question
Which statement is the most accurate simplified description of 4GDH?
- A high‑temperature district‑heating concept designed to integrate large thermal power plants more efficiently into urban networks.
- A cooling‑based district‑energy system that distributes chilled water for building air‑conditioning instead of heat.
- A hybrid district‑heating model that raises supply temperatures above 100 °C to improve heat‑exchanger performance in old buildings.
- A lower-temperature hot-water district-heating concept, often classified with maximum forward-flow temperature at or below about 70 C.
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Question 5 of 20

5. Question
Which description best matches 5GDHC / thermal source network (TSN)?
- A shared near-ambient water or brine loop used as a heat source and heat sink for building-level reversible heat pumps.
- A high‑temperature loop that distributes centrally produced hot water to buildings without the need for heat pumps.
- A system where each building has its own boiler, but all boilers share a common flue gas recovery network to improve efficiency.
- A low‑temperature district‑cooling network that circulates chilled water for air‑conditioning and rejects heat to a central cooling tower.
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Question 6 of 20

6. Question
What is a typical difference between 4GDH and 5GDHC?
- 4GDH commonly uses building heat exchangers, while 5GDHC commonly uses building-level heat pumps.
- 4GDH typically uses decentralized heat pumps in each building, while 5GDHC relies on large central heat exchangers.
- 4GDH requires dual‑pipe building connections, whereas 5GDHC uses a single‑pipe loop for both heating and cooling.
- 4GDH is only for heating, while 5GDHC is only for cooling.
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Question 7 of 20

7. Question
Why can lower-temperature networks use more low-grade heat sources?
- Because cooler water circulates faster, improving heat extraction from any source.
- Because the network or heat pump can use heat available at lower temperatures, such as wastewater, shallow geothermal or rejected cooling heat.
- Because the pipes lose less heat, so even low-grade heat sources can raise the temperature significantly.
- Because buildings require less heat at lower supply temperatures, making low-grade heat sources sufficient.
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Question 8 of 20

8. Question
Which option is a realistic source of recovered or surplus heat for low-temperature DHC?
- Heat from rooftop solar thermal collectors installed on residential buildings.
- Heat generated by district‑heating circulation pumps during operation.
- Supermarket refrigeration heat.
- Heat from domestic hot‑water storage tanks inside individual apartments.
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Question 9 of 20

9. Question
Which group of factors is most important when assessing whether a heat source can be connected?
- Temperature, available capacity, stability, operating hours, distance, reliability and economics.
- The age of the equipment, the type of insulation used, and where the heat source is located.
- The chemical composition of the water, the manufacturer of the heat exchanger.
- The number of consumers already connected, the type of billing system used, and the historical energy consumption of the neighbourhood.
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Question 10 of 20

10. Question
What is the main role of a heat pump in low-temperature district-energy systems?
- To stabilize the network by keeping the circulating water at a constant temperature throughout the year.
- To reduce pipe heat losses by cooling the network water before it returns to the energy centre.
- To raise heat from a lower temperature to a useful heating or DHW temperature, or to move heat during cooling.
- To increase the flow rate in the distribution network by adding mechanical energy to the water.
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Question 11 of 20

11. Question
How does temperature lift usually affect heat-pump COP?
- A smaller temperature lift generally improves COP.
- A larger temperature lift always improves COP.
- Temperature lift has no effect on COP.
- COP is only affected by the colour of the heat pump casing.
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Question 12 of 20

12. Question
What can thermal energy storage do in a low-temperature DHC system?
- Increases the supply temperature of the network to meet the peak‑hour demand.
- Reduce pipe heat losses by keeping the network water at a constant temperature throughout the day.
- Allows the network to operate without any backup heat sources by providing all heating and cooling year‑round.
- Shift heat or cold between times, store renewable or recovered energy and help balance seasonal heating and cooling.
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Question 13 of 20

13. Question
What is a thermal prosumer?
- A user who can both consume thermal energy and supply useful heat or cold to the network.
- A consumer who can adjust their heating demand based on network signals but cannot supply any heat back.
- A building that stores heat in large tanks and releases it only inside the building without interacting with the network.
- A user who installs advanced metering equipment to monitor their thermal consumption in real time.
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Question 14 of 20

14. Question
What does simultaneous heating and cooling mean in a 5GDHC/TSN context?
- The network must operate two separate loops at different temperatures to serve heating and cooling independently.
- Some users need heating while others reject heat from cooling, allowing heat recovery through the shared loop.
- Buildings switch rapidly between heating and cooling modes during the day to maintain stable indoor temperatures.
- It refers to the network providing heating in winter and cooling in summer without needing to change operating strategy.
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Question 15 of 20

15. Question
Which requirement is most relevant for a building that wants to export heat to a network?
- Controlled export temperature/flow, suitable hydraulic connection, metering, communication and agreed operating/commercial rules.
- A building only needs a high‑efficiency boiler and a standard heating connection to export heat to the network.
- To have a large thermal storage tank so the building can send excess heat whenever the network needs it.
- A building must operate at higher temperatures than the district‑heating network so that heat naturally flows into the pipes without any control systems.
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Question 16 of 20

16. Question
Which is a common challenge when integrating thermal prosumers?
- Thermal prosumers often overload the network because exported heat is always much hotter than the supply temperature, forcing operators to constantly reduce flow.
- Integrating prosumers is difficult because their heat pumps typically require a completely separate pipe loop, making them incompatible with shared district‑energy infrastructure.
- Prosumers consume more heat than they export, which causes the network to lose pressure and become hydraulically unstable.
- Exported heat may not coincide with network demand or may be too low/unstable in temperature.
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Question 17 of 20

17. Question
Before lowering the network flow temperature, what should be checked at building level?
- Only the building’s circulation pump speed needs to be checked, because lower network temperatures mainly affect hydraulic performance rather than heat delivery.
- Envelope heat loss, emitter capacity, design temperatures, hydraulic balancing, controls and heat-exchanger performance.
- The key requirement is verifying that the building has modern thermostatic radiator valves, since these automatically compensate for any reduction in supply temperature.
- Operators should confirm that the building’s domestic hot‑water tank is large enough to store extra heat for peak periods.
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Question 18 of 20

18. Question
Which statement about domestic hot water (DHW) in low-temperature networks is correct?
- DHW hygiene risk concerns the potable DHW system, so approved temperature, residence-time and control strategies are still needed.
- Legionella risk is only a problem in the closed district-heating network water.
- Low‑temperature networks eliminate DHW hygiene concerns because the circulating water is not hot enough for Legionella to grow.
- DHW systems in low‑temperature networks can safely operate at any temperature as long as flow rates are high enough.
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Question 19 of 20

19. Question
Which activity is part of smart operation of low-temperature networks?
- Keeping pumps at maximum speed at all times.
- Installing larger pumps and pipes so the network can always meet peak demand without advanced control.
- Demand forecasting, variable-flow control, peak management, sector coupling and fault detection.
- Replacing all building substations with smart units to standardise network behaviour.
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Question 20 of 20

20. Question
A building connected to a low-temperature network cannot maintain comfort after supply temperature is reduced. What is the best response?
- Check heat loss, emitters, balancing, controls and heat-exchanger approach temperature; then consider envelope improvements, larger emitters or temporary boosting.
- Increase the network temperature back to previous levels and keep it permanently higher to avoid any future comfort issues.
- Install a larger circulation pump in the building substation so that more water flows through the emitters even at lower temperatures.
- Reduce the building’s thermostat setpoints so that comfort can be maintained without changing anything in the heating system.
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