Optimizing for Ontario: getting the most out of net-metered systems

As the price of solar PV modules continues to fall, fast and cost effective design optimization is becoming an increasingly critical tool for lowering overall system costs and maximizing project yields. Many of the latest modelling tools available to solar system designers allow for runs of parametric studies, which can quickly demonstrate the relative impact of changing system variables, such as panel tilt, row spacing, or array azimuth.

Design optimization of PV systems in Ontario will become ever more important as the FIT program winds down. Apricity expects the Ontario net-metering program to become an increasingly important platform that connects distributed PV systems to the grid. Gone will be the days of above retail price fixed-rate contracts that place no importance on when your power is generated. Under the present FIT program, designers have typically maximized yield by facing panels due south, and could care less about matching array output to building load or grid peak demand. But the success of a net-metered project is highly dependent on these factors! Matching production to periods of high personal consumption and/or market price of electricity is essential. As can be seen in the figure below, shifting the array azimuth westward can better align peak production with peak consumption:

A temporal comparison of power production from three PV arrays with different orientations (all 18 degree tilt), and a typical residential load profile (July).

A temporal comparison of power production from three PV arrays with different orientations (all 18 degree tilt), and a typical residential load profile (July).

As margins will be tight on early net-metered projects, design optimization will play a critical role in helping designers push system performance to the limit. The advent of Time-of-Use (TOU) rate structures has demonstrated the power of design optimization. In the past few years we have begun to hear of designs in TOU jurisdictions deviate away from what used to be optimal array orientation: due south. Arrays have become slightly westward facing, aimed at capturing more afternoon sun and producing electricity when market demand (and retail price) for electricity is higher. Ontario has recently adopted a time-of use billing system as well. Will we also see Ontario designs begin to shift their array azimuths westward?

The answer to this question is, of course, an optimization problem. A modelling tool (such as NREL's SAM) is capable of evaluating multiple system designs in comparison to various TOU rate structures. In Ontario the TOU structure for residential and small business consumers is as follows:

Ontario TOU rate structure as laid out by the IESO

Ontario TOU rate structure as laid out by the IESO

 

Summer rates peak from 11am-5pm, and winter rates peak twice between 7am-11am and 5pm-7pm. The summer peak rate especially is seen to be out of sync with when solar noon occurs in July (1:23pm). Combine this fact with the knowledge that residential consumption peaks later in the day during the summer and one would expect a westward shift to benefit a net-metered project in Ontario, right? Well, the models indicate otherwise:

Annual Electricity Savings for a 8.5kW residential solar system at different azimuth angles. Note that this analysis assumes a home with a large enough load to avoid credit expiration.

Annual Electricity Savings for a 8.5kW residential solar system at different azimuth angles. Note that this analysis assumes a home with a large enough load to avoid credit expiration.

 

According to the quick parametric study, there is no incentive under the current Ontario TOU structure to orient arrays towards the west. In fact, even with the off-peak rate reduced by 30%, and the peak rate increased by 30%, there still is no advantage. With the current rate structure in Ontario it would appear the designers have no reason to center production later in the afternoon. It just doesn’t make financial sense!

Ongoing review and feedback of Ontario’s LTEP should consider how rate structures can support increased distributed generation that more effectively helps reduce peak demand. This discussion needs to also consider how grid peaks will shift as more distributed generation gets added, and as consumption patterns change due to increased market penetration of electric vehicles, the advent of the connected home, and the decarbonisation of home space heating.

This analysis demonstrates the power modelling tools have to correct what our intuition might get wrong. At Apricity, our expertise in advanced modelling tools allows us to create site specific models that address: the accuracy of solar resource data, uncertainties surrounding load profiles, and the impacts of snow losses in Canadian climates. Managing these factors requires the use of professional tools and site specific data. Apricity is committed and excited to combine our expertise with the most robust data sources possible to turn future solar projects from a ‘No’ to a ‘No-brainer’.

DISCLAIMER: All data and information provided on this blog is for informational purposes only. Apricity Renewables Inc. makes no representations as to accuracy, completeness, currentness, suitability, or validity of any information on this blog and will not be liable for any errors, omissions, or delays in this information or any losses, injuries, or damages arising from its display or use. All information is provided on an as-is basis. Blogs posts do not necessarily reflect the views or opinions of Apricity Renewables Inc. and should not be construed as such.