Entering base case energy cost for Solar Water Heating Systems

When a solar water heating system reduces energy cost from a gas furnace or other type of energy sources, I do not see an obvious way to specify that base case energy source been displaced.

The only way I have figured to imput the cost of natural gas for example is to convert the price of natural gas from $/unit of energy ($/GJ or $/m3 for example) to $/MWh and input that as a negative cost (as this is avoided cost) under

SWH System Costs
Operation and Maintenance Costs
Variable Cost by Generation

There several problems with that approach. For one, it screws up the various ratios such as LCOE. LCOE should not be affected by the cost of the base case energy.

If there is still time to make any modification in the next version of SAM,I would suggest that under System cost, Utility Rate (or both), you allow the user to select the base case energy source so that they can select either Natural Gas, Propane, Oil...)

This is something that I like in the RETScreen solar heating model ( www.retscreen.net ) and which I find could be improved in SAM.

If that type of feature is there but I missed it, please let me know where it is. Thanks.

Frederic Pouyot
www.gpeks.com

Dear Frederic,

SAM's solar water heating model is limited in that it can only calculate savings for a system with an electric auxiliary heater. It cannot calculate savings for a natural gas or other fuel-based water heater.

The sample file that comes with SAM 2014.1.14 and earlier "SamUL Solar Water Heating with Auxiliary Gas.zsam" uses a SamUL script to estimate savings for a solar water heating system with auxiliary gas. You can find the file from SAM's File menu, under "Open sample file."

Best regards,
Paul.