An almond farm in California and the electricity grid
What is demand response?
Demand response, or DR, is defined by the power sector as a mechanism through which an end- user’s load profile is changed (by the user, a third party or a utility) in response to grid system needs, often in return for economic compensation (e.g., payments or a different rate structure).
The decade old “duck curve” below portrays two major challenges faced by a high renewable penetration grid. The first challenge is solar overgeneration during the day, which requires thermal power plants to ramp down in order to make room for solar electricity. The second challenge is the steep evening ramp-up of thermal power plants as the sun goes away.
Meeting those challenges with the current fleet of power generators is difficult due to two important factors. First, most thermal power plants are not designed to handle such steep ramps. Second, economics will hinder many thermal generators to do so (nuclear and coal power plants are only economical if they run around the clock). Instead, one service that can ensure grid stability while financially benefiting end users is most commonly referred to as demand response.
Irrigation pumping uses electricity throughout the day, including evening peak hours. Demand for pumping water is highest during the midday hours with highest levels of evapotranspiration. This creates a perfect synergy for irrigation loads to shift demand from evening hours to midday hours. In other words, it helps reduce the evening ramp requirements and eliminate midday solar overgeneration.
Currently, a suite of DR incentive programs is offered through the utilities and third-party aggregators. Specific details of DR programs vary by service territory, but typically those programs provide the customer with a notification window (either day-ahead or day-of) and stipulate that interruptions will last no more than a set number of hours (typically 3-4 hours) and no more than a total number of hours per month (typically 30 hours per month). In return, growers will receive financial incentives to enable their pumps for
The duck curve shows steep ramping needs and overgeneration risk. Source: California Independent System Operator 2016 Net load – March 31
28,000 26,000 24,000 22,000 20,000 18,000 16,000 14,000 12,000 10,000
0
2012
(actual) 2013
(actual) 2014
2016 2015
2019 2018
Overgeneration risk 12 a.m. 3 a.m. 6 a.m. 9 a.m. 12 p.m. Hour 30 Irrigation TODAY | October 2018 3 p.m. 6 p.m. 9 p.m. 2017 2020 Ramp need
~13,000 MW in 3 hours
Megawatts [MW]
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