Commercial PV system with no export

Hi
I use Sam to model PV systems in Australia. I'm able to vary most inputs to suit Australian conditions in terms of taxation and subsidies, etc.

One area I'm having a problem with is due to the changes in Australia where with commercial systems it is no longer logical to export power, rather consume most or all in-house. This due to the recent reductions in FiT's. FiT's are typically 6-8c/kWh whereas power purchase for small to medium commercial companies costs 10-14c/kWh. These smaller commercial PV systems (30-200kW) are NET metered.

When I model a commercial system in SAM, it seems all the "revenue" from power produced is taxed (gross metering?). However if some or all of the power is consumed in-house, it is an internal cost reduction and under NET metering this portion is not subject to tax.

At present I can send to excel with equations and modify the cashflows to suit, however the inbuilt SAM modelling functionality and direct graphing, is somewhat lost. Is there something that I'm missing, or does SAM in Commercial mode always assume Gross metering?

I completely understand that your product is for and funded by the US market, but a feature for switching NET/GROSS metering where internally consumed power's financial benefit, for the portion of generation that is less than load, is not taxed (and visa versa) would be very helpful in our and other markets.

Regards
Mark

Dear Mark,

I think that SAM is modeling the commercial system as you want it to.

When you model a system in SAM using either the Commercial or Residential financial model, SAM calculates the project revenue based on the quantity of electricity delivered to the grid after meeting the building or facility load defined on the Electric Load page. In the cash flow table, SAM displays the total quantity of electricity generated by the system as "Energy (kWh)" in the first row, but the value of that energy ("Energy Value" in the second row) is based on the portion of that energy that was delivered to the grid. SAM calculates the income tax amount by applying the state and federal income tax rates to the energy value.

On the Utility Rate page, "net metering" means that the buy rate is equal to the sell rate, which I think is different than your use of the terms "net metering" and "gross metering." In the U.S., "net metering" refers to a set of local laws that determine how an electric utility sets prices for electricity that it purchases from its power-generating consumers.

To model your project, on the Utility Rates page, clear the "Enable net metering" check box, and use Flat Buy Rate for the power purchase price, and Flat Sell Rate for the FiT (feed-in tariff) rate. Unless you want to model time-of-use or tiered rates, make sure all of the other check boxes are clear. Then, on the Electric Load page, specify the in-house electricity consumption that the system will meet before selling power to the grid. That should model the revenue portion of the project as you describe.

Specifying the load data in SAM can be a little tricky. I've tried to explain it in the Electric Load topic in Help (you can also access that topic directly from the Electric Load page in SAM), but let me know if you have questions about how to do that.

Also, you may be interested in this newsletter announcement from AUSTELA describing work IT Power (Australia) did with us to develop sample files and a handbook for modeling Australian CSP projects in SAM.

Best regards,
Paul.

Hi Paul
Thanks for the update. Your comments were very helpful. I'm still doing a little post processing, however I have a much better handle on the functionality, especially the load side. I was caught out a little by the switch Normalise supplied load profile to monthly utility being on, however now all making sense.

Interesting article, in my own small way I'm doing similar for PV, but with no funding .

Thanks
Mark Norman