PhD Thesis - Energy Systems Research Unit - University of Strathclyde

In the course of this chapter Scenario 5 High has been mentioned only sporadically incomparison to the other scenarios. As explained in Section 4.1.1, the reason for thisis that the only difference between this scenario and the 6 household building withefficient building fabric (Scenario 2 High ) was in the way the cogenerated electricitywas used. Contrary to the other scenarios, in Scenario 5 High the electricitycogenerated by the micro-trigeneration system was not used to satisfy the building’sown electrical demand with the excess being exported, but rather all the electricitycogenerated was exported to the grid. In terms of system operation, the system isunaffected. The system’s financial value is however considerably affected,particularly if the price differential between the imported electricity and the Feed inTariff is significant.For the assumed FIT, at the low end of the electricity tariffs range when the cost ofimporting electricity from the grid is low, the calculated PW for Scenario 5 High/Currentefficiency is about 2.7 times higher than the equivalent PW for Scenario 2 High/Currentefficiency. Similarly, the calculated PW for Scenario 5 High/High efficiency is 3.2 times higherthan the equivalent PW for Scenario 2 High/High efficiency . As the electricity tariff isincreased, both ratios first drop to 1.2 times at the current electricity tariff and then to1.1 times at the high end of the electricity tariffs range. For the assumed financialparameters therefore the results suggest that the projects would have a higherfinancial value if all the electricity is exported.5.5.1.2 Present worth assuming a variable LPG price scenarioHaving discussed the sensitivity of the PW of the proposed micro-trigenerationsystem to different operating conditions assuming varying electricity tariffs, thissection examines the sensitivity of the system to different operating conditionsassuming varying LPG prices. The electricity tariff in this case was assumed constantat the current tariff level. Figure 5.16 compares the PW plots for the cases in the 3and the 6 household building (Scenarios 1 and 2 respectively) for varying LPG prices.The first important consideration which arises from the plots is that contrary to itssensitivity to electricity tariffs which diminishes with lower electricity tariffs, the PW217