Mark Mikofski

DNV-GL · Solar

Photovoltaic systems may underperform expectations for several reasons, including inaccurate initial estimates, suboptimal operations and maintenance, or component degradation. Accurate assessment of these loss factors aids in addressing root causes of underperformance and in realizing accurate expectations and models. The performance loss rate (PL...

Solar energy modeling errors due to time-averaged hourly inputs are significant where solar resource variability and inverter loading ratio are both high. However, predictions of photovoltaic (PV) system performance are most frequently made with hourly solar resource inputs, typically computed from satellite data obtained every 15 or 30 min. Theref...

Trackers on variable terrain can incur electric mismatch losses from row-to-row shading even with backtracking. Tracker terrain loss is the difference between the performance of trackers on horizontal ground and that on variable terrain. SolarFarmer was used to study tracker terrain loss by simulating the Hopewell Friends Solar power plant, which h...

Over the past decade, the global cumulative installed photovoltaic (PV) capacity has grown exponentially, reaching 591 GW in 2019. Rapid progress was driven in large part by improvements in solar cell and module efficiencies, reduction in manufacturing costs and the realization of levelized costs of electricity that are now generally less than othe...

Slope-Aware Backtracking for Single-Axis Trackers

pvlib python is a community-supported open source tool that provides a set of functionsand classes for simulating the performance of photovoltaic energy systems. pvlib pythonaims to provide reference implementations of models relevant to solar energy, includingfor example algorithms for solar position, clear sky irradiance, irradiance transposition...

Partial shading is the condition of nearby objects casting shade onto part of a photovoltaic (PV) array, causing the PV modules to receive non-uniform irradiance. Non-uniform shading causes electrical mismatch between elements within the array, resulting in a non-linear reduction in energy capture. Accurately modeling mismatch conditions is a parti...

Predicted clear sky irradiance depends on atmospheric composition as well as solar position and extra-terrestrial irradiance. The effects on clear sky irradiance of year to year variations in atmospheric composition were studied using measurements of aerosol optical depth (AOD) and precipitable water (Pwat) at seven locations in the United States....

Predicted clear sky irradiance depends on atmospheric composition as well as solar position and extra-terrestrial irradiance. The effects on clear sky irradiance of year to year variations in atmospheric composition were studied using measurements of aerosol optical depth (AOD) and precipitable water (Pwat) at seven locations in the United States....

Accurately modeling the performance of partially shaded photovoltaic systems is well-known to be a difficult problem. Power loss is not only nonlinear with shade coverage, but also has a strong dependence on system configuration and location of the shade on a system. This paper presents a parameterized shade loss model (called the “Fast Shade Model...

Spectral shift from the ASTM G173-03 reference spectrum was calculated for different cell types from measured quantum efficiency and predicted spectral irradiance using the Bird Simple Spectral Model with measured aerosol optical depth and water vapor. Our predictions correlated well with measured spectral shift for different sites and cell technol...

Accurately modeling the performance of partially shaded photovoltaic systems is well-known to be a difficult problem. Power loss is not only nonlinear with shade coverage, but also has a strong dependence on system configuration and location of the shade on a system. This paper presents a parameterized shade loss model (called the “Fast Shade Model...

Spectral shift from the ASTM G173-03 reference spectrum was calculated for different cell types from measured quantum efficiency and predicted spectral irradiance using the Bird Simple Spectral Model with measured aerosol optical depth and water vapor. Our predictions correlated well with measured spectral shift for different sites and cell technol...

Establishing a strong basis for confidence in a solar technology requires being able to prove a low-degradation track record in the real world, and rationalize it with strong physical understanding and investigation. This paper briefly reviews our previously-published physical model for calculating degradation and reliability, PVLife, which compute...

We report results of an integrated model called PVLife that predicts the performance and degradation of a PV system over its entire lifetime. The model solves the coupled electro-thermal equations to calculate PV panel performance for a given set of weather conditions. Based on this calculated operating point and a series of physical sub-models for...

Predicting lifetime performance of PV systems is critical for determining the cost of solar energy. This paper introduces a physics-based model that predicts hourly performance, degradation and reliability of SunPower back-contact cells in a PV system using a series of one-diode cell models and sub-models for all major degradation modes. Other comp...

The flame structure of laminar inverse diffusion flames (IDFs) was studied to gain insight into soot formation and growth in underventilated combustion. Both ethylene–air and methane–air IDFs were examined, fuel flow rates were kept constant for all flames of each fuel type, and airflow rates were varied to observe the effect on flame structure and...

Flame heights of co-flowing cylindrical ethylene–air and methane–air laminar inverse diffusion flames were measured. The luminous flame height was found to be greater than the height of the reaction zone determined by planar laser-induced fluorescence (PLIF) of hydroxyl radicals (OH) because of luminous soot above the reaction zone. However, the lo...

Measurements of line-of-sight laser extinction in a co-annular ethylene-air laminar inverse diffusion flame (IDF) were made to determine soot concentration. Extinction has frequently been used in the literature to measure soot concentration in normal diffusion flames (NDFs), but it has rarely been applied to IDFs. A coflow IDF contains a primary ai...

Flame structure and soot and carbon monoxide (CO) formation were studied in laminar co-flowing co-annular inverse diffusion flames (IDFs) in normal and microgravity. An IDF is a non-premixed flame that consists of an inner air flow surrounded by a fuel flow. Soot formation is important to understand because soot particles are a health concern and h...

The structure of laminar inverse diffusion flames (IDFs) of methane and ethylene was studied using a cylindrical co-flowing burner. Several flames of the same fuel flow-rate yet various air flow-rates were examined. Heights of visible flames were obtained using measurements of hydroxyl (OH) laser-induced fluorescence (LIF) and visible images. Polyc...

Almost seventy percent of fire related deaths are caused by the inhalation of toxins such as CO and soot that are produced when fires become underventilated.(1) Although studies have established the importance of CO formation during underventilated burning,(2) the formation processes of CO (and soot) in underventilated fires are not well understood...

Direct numerical simulations of 0-g and 1-g CH4 and C2H4 inverse diffusion flames were combined with experimental results to gain insight into the earliest soot and CO formation processes. Qualitative agreement between experiments and models was achieved for flame shapes and relative flame heights. The inverse flames exhibited buoyancy-induced flic...

The structure of laminar inverse diffusion flames (IDFs) of methane and ethylene was studied using a cylindrical co-flowing burner. Several flames of the same fuel flow-rate yet various air flow-rates were examined. Heights of visible flames were obtained using measurements of hydroxyl (OH) laser-induced fluorescence (LIF) and visible images. Polyc...