For a specific scenario, I have hourly PV output power measured over a year (8760 data points) and also a time series of the electric load. I want to simulate a microgrid with a PV system, an electric load, a gas generator, a converter and a lithium battery bank. I have the following two problems.

(1) I know that Homer allows me to use either NREL or NASA databases for GHI. It also allows me to input a time series of solar radiation. I want my simulation to generate the specific PV output power that I have, so I tried to convert this PV output power into solar radiation. I set up the PV array to a zero degrees inclination angle and zero degrees azimuth angle. I was expecting to obtain: PV output = GHI*(PV power)*(derating factor). From that equation I calculated GHI = (PV output)/((PV power)*(derating factor)).

I know that incident radiation is calculated from a series of equations available in the Homer web site, but since I set up the inclination angle and azimuth to 0 I expected the incident radiation to be equal to the GHI. It turns out that it is not equal. Furthermore, I am interested in a 2-week period of time, so I tried to adjust manually by trial and error the solar radiation to obtain the desired PV output power. However, a big change in solar radiation didn't translate to a change in PV output power. Do you have any ideas on how I can simulate a specific PV output power?

(2) As I mentioned before, I am interested in a 2 week scenario. I want the batteries to be the priority over the gas generator. However, I know that Homer always choose the cheapest source of electricity first, and it turns out that the gas generator is always cheaper than the lithium battery bank. The only way I could prioritize the batteries was by setting up a very low price for them, but then the economic analysis doesn't match. I know I can write down a Matlab code to create my own dispatch algorithm, but I was wondering if there is an easier way to make Homer use the batteries before the generator without decreasing the price of the batteries.

Edited: 1 month ago

Posted : March 19, 2018 1:36 pm

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