Question 8 - Heat Networks Flashcards
Q8A) What is a heat network and explain the 5 different generations of a heat network ?
A heat network, also known as a district heating system, is a centralized system that produces and distributes heat to multiple buildings or customers for space heating, hot water, and other heating purposes. Instead of each building having its individual heating system, a heat network allows for the efficient sharing of heat resources, often through a network of pipes.
The concept of generations in heat networks is a way to categorize the evolution and advancements in these systems.
1G - First-generation heat networks are characterized by centralized heat generation using a central steam plant that contains some thermal steam storage.
Heat is distributed through a network of pipes to connected buildings.
Supplying heat around 200 Degrees
Typically, the network operates at a higher temperature, limiting the potential for using low-grade heat sources.
1880-1930
2G- These heat networks are characterized by centralized combined heat and power (CHP) plant.
Second-generation systems aim to reduce heat losses by using lower distribution temperatures.
Supplying heat at around 100 Degrees
These systems often incorporate advanced insulation and more efficient heat exchangers to improve overall efficiency.
1930-1980
3G - Third-generation systems focus on increasing overall energy efficiency by combining heat and power generation (CHP), biomass and industrial waste heat.
It supplies heat at around 60-90 degrees
1980-2020
4G - Produces lower temperature heat at around 45-55 degrees
Combines low grade waste heat, with a centralised heat pump and CHP, combined with industrial waste heat produces a high level of energy efficiency.
Incorporates some power by utilising renewables such as solar.
2018-2050
5G- The fifth generation explores the use of even lower distribution temperatures below 45 Degrees
It incorporates the use of advanced technologies for improved control, monitoring, and optimization such as digital solutions and smart meters/sensors
This incorporates different forms of heating through the use of low grade waste heat, inter seasonal energy stores, solar thermal, with the combination of decentralised heat pumps and thermal stores with industrial waste heat. It involves the use of PV, batteries and other renewable technologies with makes it a very efficient network
Q8B) How does heat networks contribute to decarbonisation ?
eg. waste heat etc..
It helps cope with the transition of reducing gas and oil use for heating. By using waste and renewable heat to replace the heating demand from fossil fuels.
Efficient Energy Distribution - More efficient than individual heating systems
Renewable energy integration
Low Carbon Heat Sources
Battery Storage
It helps increase energy flexibility and stability
Q8C) Heat network calc - delivering heat at 80 degrees via third generation, returning at 60 degrees, to supply an apartment block of 55 rooms.
Heat loss of apartments = 360 kW
Network = 880 Metres
Heat Loss = 6.1 watts / metre
What is the appropriate boiler size for this network
1- Calculate Heat Demand
Apartment Block Size x heat loss
=55 x 360 = 19800
The apartment may just be 360 kW for all/not per room
2- Calculate heat loss in the network
Temperature difference = 20 degrees
Loss Network = Length x heat loss /m x dT
880 m x 6.1 watts/meter x 20 degree = 107360 watts - 107.36 kW
3- Calculate Total Heat Supply Required
Heat Supply = Heat demand + heat loss network
360kW + 107.36 kW = 467.36 kW
If boiler efficiency is mentioned, that divide it into the heat heat supply.
Q8D) if the example operated at an ambient loop at 20 degrees, why would there be lower heat losses and what would need to be installed to ensure adequate heat in the apartments
Boiler, CHP etc..
Reduced Temperature Difference:
Heat transfer occurs between the distribution pipes and the surrounding environment. The rate of heat loss is directly proportional to the temperature difference between the system (20 degrees) and the external environment. By operating at a lower temperature, this temperature difference is reduced, resulting in lower heat losses.
Lower Transmission Losses:
The heat loss through the distribution pipes is influenced by the temperature of the fluid inside the pipes. Lowering the operating temperature reduces transmission losses, which occur as heat moves from the warmer fluid inside the pipes to the cooler surroundings.
Improved Insulation Efficiency:
Insulation materials are generally more effective at lower temperatures. By operating at 20 degrees, you can take advantage of the improved efficiency of insulation, further reducing heat losses through the distribution network.
To ensure there is still adequate heat being delivered to the apartment, a heat pump or condenser boiler can be installed that operate efficiently at lower return/operating temperatures.
