Example Study 1: Small Office Building
This example considers a small office building in Southern Alberta. Given the facility energy consumption data (shown right), the cost for grid electricity and natural gas, we computed the size of CHP that maximizes the ROI to be a 150kW solution.
The ROI is shown as a function of CHP size in the bottom right chart (red), demonstrating a maximum ROI at 150kW.
At 150kW, the CHP does not generate sufficient electricity nor heat to provide for all the facilities electricity needs as shown in the left charts (facility demand in red and CHP production in blue). Further cost reductions (top right chart) can be achieved with CHP’s up to 250kW which would provide almost all the facilities needs. However, the ROI would drop by 2%.
At 250kW, the CHP would provide for most of the electricity needs and would accommodate the base thermal load. However, the CHP would need to modulate down from 250kW to as much as 100kW for a total of 38% of the time. As this would decrease efficiencies and increase maintenance costs, a 250kW solution would be considered to be too large.
If the surplus electricity could be exported to the grid, a 250kW CHP could run at peak efficiency and improve the ROI.