A European research team has investigated the effect of different time resolution data on the design of hybrid PV-wind power plants (HyPPs) and has found that lower resolution can result in an overestimation of the net present value (NPV) of the facilities by up to 3%.
“When performing feasibility studies for HyPPs, data on hourly resolution, or lower, is typically used, as it is the resolution which is commonly available in meteorological databases,” the group said. “However, when optimizing the topology of HyPPs with point of interconnection (POI) capacity limits, the techno-economic feasibility of these power plants might be overestimated since the curtailment and clipping losses will be underestimated when using hourly instead of higher resolution data.”
The research was based on data acquired from an operational HyPP in East Germany. This plant has an installed PV capacity of 11.64 MW and a DC-AC ratio of 1.13. The wind turbines have an installed capacity of 24 MW, and as they are installed 1.6 km from the PV panels, they do not cast shade on them. In 2020, the year the researchers conducted their research, the wind and PV assets generated 57.58 GWh and 12.80 GWh, respectively.
Weather and generation data from the German HyPP were recorded at a 5-second resolution and down-sampled for one minute and one hour for the comparative analysis. As part of the analysis, different DC-AC ratios were assumed for the PV part, effectively changing the plant's real capacity.
“It has been shown that for a HyPP consisting of 1 per unit (p.u.) of wind, PV, and POI capacity, respectively, the curtailment losses are estimated to be only 1.45% for the 5 s and 1.09% for the 1-hour resolution dataset, translating to income losses of 0.77% and 0.51% in the German day-ahead market, respectively,” they found. “These results demonstrate a discrepancy between the losses estimated by the hourly and high-resolution datasets.”
Moreover, the researchers found that using 1 min resolution data appears sufficient to approximate the curtailment losses predicted by the 5-second dataset. “Acquiring the data on 1-minute resolution seems to be a good compromise between accuracy and measurement effort,” they explained.
Conducting a techno-economic estimate to find the optimal size of the HyPP, the researchers found that using the 1-hour dataset leads to a 1.86% overestimation of the total NPV compared to the 1-minute dataset. They also said that when increasing the shares of the PV and wind capacities further relative to the POI capacity, this overestimation becomes larger.
“The techno-economic model indicates that the cost-optimal HyPP topology for this site consists of wind and PV capacities that are each slightly larger than, yet closely aligned with, the POI capacity. Utilizing the 1-hour instead of 1-minute resolution data appears to have little impact on identifying the optimal HyPP design,” they said. “However, for the optimal HyPP topology derived from the 1 h dataset, the NPV is overestimated by 2.99% when calculated with the 1-hour instead of the 1-minute dataset.”
Their findings were presented in “Influence of high-resolution data on accurate curtailment loss estimation and optimal design of hybrid PV–wind power plants,” published on Applied Energy. The group included academics from Norway's Institute for Energy Technology (IFE), the University of Oslo (UiO), and Germany's Fraunhofer Institute for Solar Energy Systems (ISE).
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