Go west, young solar? An analysis

A rebate offered by a Missouri public utility is stirring up debate on how to use solar in addressing the vaunted “duck curve”.

August 11, 2017 Mark Burger

The recent announcement by Columbia (Missouri) Power and Light Company to introduce an additional incentive for west facing solar has brought renewed attention to the “duck curve” issue, this time outside of the California and Arizona markets. There is concern that large amounts solar being installed due south to maximize total electricity peaking at noon, whereas electricity demand, especially for summer cooling, peaks in late afternoon and early evening, causing a mismatch. This becomes more apparent where solar has made significant inroads, like California’s solar market share of over 10%.

The responses have ranged from providing various incentives for maximizing solar power availability during demand periods to discouragement of using solar at all. Assuming that solar power will stick around, incentives will be discussed here. Effective August 1, Columbia will offer solar installations up to 10 kW (essentially a residential market) an additional $125/kW that face due west to increase the ability of a fixed system to collect additional solar power in the mid/late afternoon that would be minimized by a due south orientation. Other rebates and net metering offerings will remain in place.

What does this mean to a Columbia residential solar customer? In doing a quick and dirty analysis using PVWATTS, a 5 kW system in Columbia facing south would be expected to generate 8,497 kWh in a typical year. The same size system facing due west would generate 7,327 kWh, a 14% or 1,170 kWh/yr fall off. June and July production numbers would hardly be affected, about a 2% loss. December and January would experience an over 30% loss of a much smaller output. The $625 additional incentive is like getting, at 11 cents/kWh, an additional 5,600 or so kWh paid up front, about five years’ difference between a south and west facing system.

What’s the value to both parties? To the system owner, it could mean a long term net loss of generation taking the metric of a PV system lasting 20-30 years. For the utility, it provides a passive way to get more electricity that would be needed to offset more expensive generation. Midwest Interstate Systems Operator’s high price so far in 2017 at its Indiana hub reached $305.15/MWh at 2 PM, May 18^th. Other spikes, mostly in the mid/late afternoon, put prices above $100/MWh.

There are concerns that Columbia is jumping the gun in maximizing solar for peak demand purposes when they are still working on the first 1% of total consumption of their electricity from the sun. One can say, however, that it’s a good thing for a utility to look ahead in this rapidly changing technology, economics and policy environment. Columbia has been more progressive than many utilities in this regards, wrapping up their Solar One program and rolling out new offerings in early 2018. The utilty’s latest annual report shows a renewable electricity share is over 6% from landfill gas, wind and solar, with costs declining in past years and any utility price increase capped at 3%.

Large scale deployment of renewable electricity like solar requires strategic planning and the need to segment markets. It also requires examination of infrastructure needs. Utility-scale solar tracking systems are one thing, residential tracking another. The residential market will likely have minimal deployment of tracking systems due to structural, shading and aesthetic issues. Battery storage, time of user and/or real time pricing and other tools are probably a ways off for Columbia, as, among other things, they are not at present a smart meter utility.

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