PV power modelling & temperature

[rjbergerud]

There's quite a bit of information we can make use of to get better PV power predictions given-data modelling. This however is unlikely to improve our results much, since we tend to have accurate outputs for fully-sunny days, which means our model probably has learned the relation betweeen solar irradiance and PV power pretty accurately.

What all this means is that the maximum power that a PV cell can generate decreases as the cell temperature increases, and since efficiency is power generated divided by power incident, the efficiency of a PV cell will decrease linearly with temperature. The exact amount of this decrease obviously depends on the details, and there is much research into how to minimize this efficiency hit, but sources estimate that a typical efficiency decrease is 0.5% per degree Celsius. [2] It is worth noting that even if efficiency goes down, overall power collected may go up if there is more sunlight on a cell, but the fact remains that a hot sunny day is a double-edged sword for a PV cell.

• http://large.stanford.edu/courses/2010/ph240/malone2/

What this means is that we could fit a linear model for efficiency of the panel as a function of temperature by selecting day where we're sure the irradiance value at the site is same as at stations. Knowing this relationship, which I don't think has much uncertainty associated with it, would mean that we can model site irradiance from solar power data (by taking the inverse function). That way, we're modelling the real point of uncertainty in the network of variables

{n weather stations irradiance} -> site irradiance -> solar power output

[rjbergerud]

Need to sort out which of these dependencies matter, because otherwise too many feedbacks to model

{n weather stations irradiance} -> site irradiance -> solar power output -> panel_temp solar power output -> panel_temp site_irradiance -> panel_temp site_temperature -> panel_temp panel_temp -> efficiency (site irradiance, efficiency) -> solar power output