Week 2 - Types of Modelling Systems

Question 1

List 4 reasons (other than global warming) for taking action to reduce fossil fuel consumption

Answer 1

1. poor air quality associated with the various gaseous and particulate emissions;
2. price rise due to diminishing fossil fuels because of scarcity;
3. security of supply due to reliance on imports from politically volatile countries;
4. maintenance of sustainable growth as new energy supply systems are introduced.

Question 2

What are the three main categories of energy supply?

Answer 2

1. fossil (coal, oil, gas);
2. nuclear (fission and fusion);
3. renewable (solar, wind, wave, tidal, biofuel, hydro, geothermal).

Question 3

Why is the harnessing of renewable energy difficult? (4 reasons)

Answer 3

1. There are many policy and technology barriers to deployment.
2. The practical resource is not vast relative to total energy demand.
3. Matching a large portion of demand will require the industrialisation of the environment on a large scale.
4. High capture levels require: energy storage and/or standby capacity.

Question 4

Why is it hard to take action to reduce energy demand?

Answer 4

Reduction in demand will require lifestyle changes that are unlikely to be acceptable to citizens.

Question 5

List 5 energy efficiency measures that might be applied to the built environment

Answer 5

1. turn down the heating system thermostat;
2. replace gas boilers with electric heat pumps;
3. upgrade the fabric (e.g. apply phase change material etc.);
4. recover heat from ventilation air;
5. introduce passive solar features (e.g. phase change material, daylight utilisation etc.).

Question 6

What is embedded generation?

Answer 6

A scheme in which small scale generators are deployed locally and used alongside conventional energy supply connections (gas and electricity) to match the energy demands of a single building or community.

Question 7

Why do we need to model energy systems? What would they support?

Answer 7

To support design decisions relating to:

1. conformance with legislation;
2. levels of comfort;
3. indoor air quality standards;
4. renewable energy technologies;
5. incorporating energy efficiency and demand side management solutions;
6. to lessen environmental impact.

Question 8

Why are energy systems difficult to model?

Answer 8

1. dynamic effects (different flow-paths vary at different rates over time);
2. systemic effects (all flow-paths are connected and influence each other)
3. non-linear effects (the defining parameters depend on the variables of state that, in turn, cannot be determined without first knowing the parameters).
4. stochastic effects (weather-related boundary conditions and human interactions can vary randomly).

Question 9

What are the 2 main dynamic modelling methods? Explain a bit about them

Answer 9

1. The response function method which can be configured in either the time or frequency domain. The Admittance method can be formulated for the frequency domain.
2. Numerical methods whereby conservation equations are established for each of many small finite volumes that represent the discretised problem and then solved simultaneously to give the variables of state over time.