Jannik Haas

Mitigation Control Against Partial Shading Effects in Large-Scale PV Power Plants

This study proposes a novel control strategy to allow partially shaded photovoltaic power plants (PV-PPs) to mitigate the detrimental effects on the frequency of power systems without the need for energy storage. The strategy divides the PV-PP into N sections operating in a deloaded mode with a specific reserve level. A central controller continually monitors each of these PV sections. When one or more sections are under shaded conditions, the control orders the unshaded sections to deploy their active power reserves to smooth the power output at the interconnection point of the PV-PP. The proposed control was tested in the isolated power system of northern Chile considering different PV scenarios and levels of deload. Results show that the control is effective in assisting frequency regulation, especially under large PV penetration scenarios. For these cases, and only on days with high irradiance variability, the benefits gained from the control strategy could be more valuable for the system than the forgone revenues due to the deloaded operation.

Grid-wide subdaily hydrologic alteration under massive wind power penetration in Chile

Hydropeaking operations can severely degrade ecosystems. As variable renewable sources (e.g. wind power) are integrated into a power grid, fluctuations in the generation-demand balance are expected to increase. In this context, compensating technologies, notably hydropower reservoir plants, could operate in a stronger peaking scheme. This issue calls for an integrated modeling of the entire power system, including not only hydropower reservoirs, but also all other plants. A novel methodology to study the link between the short-term variability of renewable energies and the subdaily hydrologic alteration, due to hydropower reservoir operations is presented. Grid operations under selected wind power portfolios are simulated using a short-term hydro-thermal coordination tool. The resulting turbined flows by relevant reservoir plants are then compared in terms of the Richard-Baker flashiness index to both the baseline and the natural flow regime. Those are then analyzed in order to: i) detect if there is a significant change in the degree of subdaily hydrologic alteration (SDHA) due to a larger wind penetration, and ii) identify which rivers are most affected. The proposed scheme is applied to Chiles Central Interconnect System (SIC) for scenarios up to 15% of wind energy penetration. Results show a major degree of SDHA under the baseline as compared to the natural regime. As wind power increases, so does the SDHA in two important rivers. This suggests a need for further ecological studies in those rivers, along with an analysis of operational constraints to limit the SDHA.

A framework to identify Pareto‐efficient subdaily environmental flow constraints on hydropower reservoirs using a grid‐wide power dispatch model

Hydrologic alteration due to hydropeaking reservoir operations is a main concern worldwide. Subdaily environmental flow constraints (ECs) on operations can be promising alternatives for mitigating negative impacts. However, those constraints reduce the flexibility of hydropower plants, potentially with higher costs for the power system. To study the economic and environmental efficiency of ECs, this work proposes a novel framework comprising four steps: (i) assessment of the current subdaily hydrologic alteration; (ii) formulation and implementation of a short-term, grid-wide hydrothermal coordination model; (iii) design of ECs in the form of maximum ramping rates (MRRs) and minimum flows (MIFs) for selected hydropower reservoirs; and (iv) identification of Pareto-efficient solutions in terms of grid-wide costs and the Richard-Baker flashiness index for subdaily hydrologic alteration (SDHA). The framework was applied to Chiles main power grid, assessing 25 EC cases, involving five MIFs and five MRRs. Each case was run for a dry, normal, and wet water year type. Three Pareto-efficient ECs are found, with remarkably small cost increase below 2% and a SDHA improvement between 28% and 90%. While the case involving the highest MIF worsens the flashiness of another basin, the other two have no negative effect on other basins and can be recommended for implementation.

Advancements in the Development of ‘‘AtaMo’’: A Solar Module Adapted for the Climate Conditions of the Atacama Desert in Chile - The Impact of Soiling and Abrasion

Dust is currently one of the major problems of PV plants in Chile. In the present study we investigate the influence of abrasion and soiling on solar modules using different combinations of solar module materials and solar cells under simulated test conditions. Indoor and outdoor tests were performed at ISC Konstanz, Germany, and at the Solar Platform of the Atacama Desert (PSDA) in Yungay, Chile, respectively. We fabricated half-size and fullsize cell modules employing different cell types, glass thickness, encapsulants, backsheets or glass-glass configurations. Modules were measured in the field for eight months. During exposure time, cleaning was performed every 60 days. Preliminary outdoor results indicate that ARC glass type exhibits higher Isc losses than standard (STD) glasses due to soiling, regardless of the combination of other materials used for the modules. Transparent backsheets (TBS) or glass on the rear side help to compensate the soiling losses due to increased internal reflection of light coming from the rear side of the module. In dirty condition, higher performance ratio (PR) was observed on half-size than on full-size cell modules under monofacial operation condition (the rear side covered: 97% compared to 94%). Under bifacial operation much higher but similar PRs for halfand full-size modules (both 107%) were reached. For the abrasion outdoor test, no damage was observed until now, even on vertical installed glasses which were installed perpendicular to the wind speed and close to the ground. For the indoor abrasion and soiling test, we adapted the standard testing conditions for sand (IEC and MIL-STD) using representative parameters such as temperature and humidity registered by 12 years of measurements and dust from eight PV plants located in the Atacama Desert. For the abrasion indoor test, the ARC layer on the glass was removed by all dust types after one minute of exposure and for 200-500 μm dust grain size. Increasing the exposure time, higher transmissivity (T), reflectivity (R) and Isc losses were detected until the abrasion effect almost reached saturation. When changing the tilt angle from 90° to 30° and reducing the grain size to 63-112 μm, lower losses were observed. Regarding the indoor test, a model was performed to predict the T and R losses according to the geographic place, glass type and sand density on the glass surface. The model predicts 3.5% higher T losses and 2.4% R losses for ARC compared to STD glasses with dust of less than 63μm grain size, regardless of the location.

Opportunities to integrate solar technologies into the Chilean lithium mining industry – reducing process related GHG emissions of a strategic storage resource

The arid northern regions of Chile are characterized by an intensive mineral mining industry and high solar irradiance levels. Besides Chile’s main mining products, copper, molybdenum and iron, the production of lithium carbonate from lithium containing brines has become strategically important due to the rising demand for battery technologies worldwide. Its energy-intensive production may affect the ecological footprint of the product and the country’s climate targets. Thus, the use of solar technologies for electricity and heat production might constitute an interesting option for CO2 mitigation. This study aims to quantify the impacts of the lithium carbonate production processes in Chile on climate change, and to identify site-specific integration options of solar energy technologies to reduce GHG life-cycle emissions. The considered solar integration options include a parabolic trough power plant with a molten salt storage, a solar tower power plant with molten salt receiver and molten salt storage, ...