KWhcoOL 7775


where the summation is taken over all devices that provide supplemental cooling, and the COP is the average over all cooling equipment in use. If the DG equipment includes any gas-fired devices, the incremental cost of natural gas consumption must also be taken into account:


where BtuBLDG is the building load and BtuGEN is the consumption of gas by the generators:

BtUGEN = X Wgen(PLR)

and where the summation is taken over all devices that convert gas to electricity. The work term must also be corrected by the part-load efficiency of any generators that are not at full load. The term BtuDG-EXHAUST represents any credit that can be applied due to exhaust heat recovery from the generators that precludes the use of conventional space or water heating sources. As with the cooling term, this credit is adjusted by the nominal efficiency of the conventional sources:



The total operating cost can now be calculated from the incremental rates, incentives, and maintenance costs. The result is:

+ Or kWhBLDG( 1 ) - kWhGEN( 1 ) kWhBLDG(2) - kWh,EN(2)

BtUBLDG( 1 ) + BtUGEN( 1 ) BtUBLDG( 2 ) + BtUGEN( 2 )


X kWh where OCRED represents a positive cash flow based on any utility incentives provided including transmission loss credits, wheeling charge credits, voltage support credits, etc. The term O0&M is used to account for any operation and maintenance costs that arise from operating the generation equipment. The two operation and maintenance (O&M) terms are those associated with regular maintenance independent of power production and that which depends on power production (i.e., number of hours operated), respectively.

Finally, an hourly cost matrix is compiled that represents all reasonable combinations of generation available to a building. The combination of equipment with the lowest cost is chosen and operated for that hour.

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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