Questions raised during revision period;

 

 

Questions from Steve Rademaker
 
As I'm going through the class notes I found what I think are the following errors:
 
Handout 2: 
 
1)   Section 11 - CCGT - bottom of page 34 - the isentropic figure in the calculation should read 0.7 and not 0.8. 
 
The isentropic efficiency of most turbines does vary,  but typically between 70% and 80%.   There is indeed a typographic error and it should be 0.8 – however,  the result of 23% is correct as this used 0.7.   The handout on the WEB has been updated accordingly and the change shown in RED 
 
2)   Section 12.8 - right hand side of page 40 - 
 
a)      Firstly, where does the 137/.7 number come from and what is it for?
 
There is actually an error in the first column of that page under 3) CCGT with CHP.  The heat load for Norwich was 137 not the 167 and this is where the 137 in the above comes from.   The 0.7 comes from the efficiency of typical gas boilers of 70%
 
b)      shouldn't the calculation that follows yield 13.4 GJ and not PJ? Then section B should be changed to GJ. The C02 calculation that follows is actually correct. 
 
No.  The average Primary Energy Requirement of 425 is equivalent to    425 * 8760 MWh in a year.  Converting this becomes 425 * 8760 *3.6 GJ = 13402800 GJ = 13.4 PJ.
 
In the calculation for CO2   it gives 13.4 but that is multiplied by 106 to bring it to GJ.    You may wonder where the 0.191 comes from rather than 191.  It is just because I wanted the answer in tonnes and not kg and if the emission factor is 151 kg/GJ it is equivalent to 0.191 tonne/GJ