Until recently, most solar installations have been set up to generate the maximum kilowatt-hours per day/year possible. This was because the incentive programs in place only took into account the overall production of a plant. This is not an issue in regions with low solar PV penetration in their energy mix, but it’s becoming a problem in areas with high solar penetration relative to the peak demand, such as in California, south Germany, northern Chile, and southwestern United Kingdom. As I have argued before, all kilowatt-hours are not equal, but since the two most common policy incentives (feed-in tariffs and net metering) treat them as equal, installers choose to maximize generation.
There are some signs that this is changing. Chile has introduced a tender system that divides the market by delivery time, and there are efforts to introduce solar-based time-of-use (TOU) tariffs in some markets. But perhaps the strongest force pushing the industry away from equal kilowatt-hour values is corporate power purchase agreements (PPAs).
Unlike in traditional PPAs, in which a utility (or the government in the case of feed-in tariffs) buys electricity and then sells it to their customer base (which has different load requirements), corporate PPAs are signed with single entities that have a specific daily load demand curve. In this scenario, the offtaker corporation might prefer to match the PPA agreement (and hence generation profile of the project) as closely as possible to its demand curve, even if that means the project will produce less than its full potential.
New Technologies Widen the Opportunity
In a world that only looks at maximizing output at the lowest cost possible, the premium that innovative solar technologies that tackled the TOU mismatch was almost nothing; the modules that were sold at the lowest price per watt were king. Once TOU enters the equation, installations will favor technologies that maximize revenue (or avoid cost from the corporate view). It is possible to use technologies like energy storage systems or implement demand response systems to match generation and demand, but it can also be tackled from the solar system design, including new technologies like bifacial solar modules based on n-type PERT (passivated emitter, rear totally-diffused) module designs, which allow vertical installations that flatten the daily generation profile of an installation, producing more electricity in the morning and in the late afternoon and less at midday.