Hi Steven,
I am not sure of the source of the default hot water draw data. It is appropriate for the Peoria, IL default location, so I don't think it would be appropriate for a representative Maine household. I would suggest that you import a different dataset.
The hot water draw equations are internal to the model and won't make much sense isolated here. The conversion involves the specific heat of water, and the difference in temperature of the mains water and delivered water.
SAM does not report the "water energy demand" in the hourly results. However, it does report the flow rate (Hot Water Draw) along with the tank and inlet temperatures, so you may be able to estimate the energy value using those variables.
Again, the equations for the hourly energy delivered to the tank are internal equations that depend on the conditions in a given time step, and involve the specific heat of water, and temperatures at the different nodes in the system.
SAM calculates the nameplate thermal capacity so that it has a value for capacity-based costs that you might specify on the System Costs page. The 30/1000 value converts the thermal loss coefficient (FRUL) from W/m2-degC to kW.
In SAM, the hourly delivered energy is the electrical energy delivered by the renewable energy system to the grid. For the solar hot water model, this value represents the electrical energy saved by the system. There is a list of the hourly output variables in SAM's Help system: Look under "Performance Model Results" in the table of contents.
The solar fraction is the ratio of solar energy to total energy delivered to the storage tank. You can find a description in Help under "Performance Metrics." For Maine, 0.93 does seem high -- I got a value around 0.76 for the default system (using the Peoria, IL demand data) with the Caribou, ME weather file. You can get high solar fractions if you use a large collector, but that should also cause the cost to be too high for a financially feasible project.
Best regards,
Paul.
