Lecture 5a - Renovation of South Kensington Campus Energy Centre

Question 1

What are the three main processes within a CHP plant?

Answer 1

1. Gas -> plant -> high grade exhaust heat (~400C) -> heat recovery boiler
2. Gas -> plant -> low grade exhaust heat (~90C) -: heat reovery system or rejected into the atmosphere
3. Gas -> plant -> electricity -> to site network of exported to the grid

Question 2

What percentage of gas in goes to each of the outputs?

Answer 2

• Electricity = 33-40%
• High grade exhaust heat (~400C) = 15-20%
• Low grade exhaust heat (~90C) = 15-20%

Question 3

What was in the previous SKC energy centre?

Answer 3

• 2 x 4.4 MW CHP plants (installed 1999)
• 3 x steam shell boilers (2 with CHP plant heat recovery)
• Steam to MTHW (medium temp hot water) plate heat exchanges.
• Annual heat demand of 75GWh
• Annual electricity demand of 81GWh

Question 4

What was the modelling methodology?

Answer 4

• Annual costs and CO2 emissions are the model output
• Climate levies considered (EU ETS, CRC, CCL) but future costs and prediction of government policy excluded to ensure results are meaningful
• Three plant options were analysed (existing CHP, smaller CHP, no CHP) against four future demand scenarios.

Question 5

What questions were asked to identify the need to change?

Answer 5

• Does the current outsourced arrangement provide value for money?
• Does the current contract reflect best practice?
• Areas of concern with current arrangement?
• What alternatives are available?
• What are the risks of changing the arrangement?
• Flexibility of operation of the CHP system?

Question 6

What is the problem with looking at CO2 emissions?

Answer 6

• The grid is decarbonising
• DECC (now DBEIS) predict rapid decarbonisation of electricity from the grid - is this correct?
• Annual grid electricity factor for a period is only known retrospectively.
• Vast majority of projects involve activities that release CO2.
• A project that is considering purely CO2e is difficult to assess.
• Demand reduction usually a much easier CO2 reduction project to justify to the board.

Question 7

What was the solution?

Answer 7

• Installed 2 x 4.5 MW CHP plants
• Heat connections to SAF - heat used all year round
• Lowered MTHW to make it LTHW (120C to 95C)
• New building heat exchangers
• Saving of £2m
• CO2 savings of >10,000 tonnes p.a.