getPVEfficiency: Get PV temperature, eletrical and thermal power

In mbask/meteopv: Tools to scrape meteorological data and to estimate pv cells power generation

Description

The relative PV cells efficiency and the energy they can potentially generate. Several models are available to estimate working temperature of PV cells based on environmental conditions. The simplest thermal model is based on the assumption that the ratio between the difference between cell temperature (Tc) and air temperature (Te) over sun irradiance on the cell (G) is constant:

\frac{T_c-T_e}{G} \approx k

This model is reasonable as far as Italy is concerned due to the absence of abrupt changes in irradiance over the course of the day and thermal inertia of PV systems can be neglected. The technical sheets of PV cells provide the NOCT value, that is the working temperature of the PV cell when air temperature is 20 ^\circC, sun irradiance is 800 W/m^2 and wind speed is 1 m/s. By coupling NOCT (Nominal Operating Cell Temperature) definition and the equation provided by the simple model we can estimate the PV cell temperature:

T_c = T_e + \frac{NOCT - 20}{800}G

By using γ, a power coefficient usually provided by technical sheets, the efficiency of the PV cell can be easily estimated:

η = η_{std}(1-γ(T_c-T_{c,std}))

where γ is the percentual decrease of power per Celsius degree, η_{std} is the power coefficient in standard conditions, T_{c,std} is PV cell temperature in standard conditions. A PV cell in standard conditions has T_c = 25 ^\circC, G = 1000 W/m^2, wind speed 1 m/s.

Usage

getPVEfficiency(env.town, cfg)

Arguments

env.town	a data.frame holding a time, place, Te and G
cfg	a list holding several cfg infos, see Details

Details

Parameter cfg is a list holding those parameters needed to

1. estimate T_c, η,

2. estimate electrical and thermal power corrected for the cell tilt and for the PV system losses.

As for the first set cfg must hold:

• NOCT Nominal Operating Cell Temperature in ^\circC, usually around 45^\circC for mono-crystalline and poly-crystalline Si systems, much lower for amorphous Si systems and Cadmium telluride systems

• etaStd γ_{std} in \%, typically around 15\%

• gamma γ in \%, a positive numeric percentual decrease of power per Celsius degree typically around 0.4–0.5\%

As for the second set cfg must hold:

• geoCoord a matrix of two columns: longitude and latitude for each location

• tilt the tilt angle of PV cells (0^\circ for an horizontal plane, 90^\circ for a vertical plane)

• PVlosses PV system losses in \%, typically around 30\%

Value

the original data.frame augmented by a few columns:

• tiltedCorrection a correction factor to convert sun irradiance on earth surface to irradiance on tilted PV panels

• tiltedPanelG the actual irradiance on the tilted panels in W/m^2

• Tc temperature of the panel in ^\circC

• tiltedTc temperature of the panel corrected for panel tilt in ^\circC

• eta PV panel efficiency in \%

• tiltedEta PV panel efficiency corrected for panel tilt in \%

• electricPower Potential electric power in W/m^2 generated by PV cells

• tiltedEPower Potential electric power in W/m^2 generated by tilted PV cells

• lossesTiltedEPower Actual electric power in W/m^2 generated by tilted PV cells and by taking into account mean percentual losses occurring in the PV system

• thermalPower Potential thermal power in W/m^2 dispersed by PV cells (basically the whole amount of irradiance that does not get converted into electric power)

• tiltedTPower Actual thermal power in W/m^2 dispersed by tilted PV cells

Author(s)

Marco Bascietto [e-mail]

References

F. Roveda, L'effetto della temperatura sulla efficienza dei moduli fotovoltaici: cosa sapere sul NOCT, 2011, http://www.energyhunters.it retrieved on 2012/10/09

E. Skoplaki and J.A. Palyvos, Operating temperature of photovoltaic modules: A survey of pertinent correlations, 2009, Renewable Energy 34, 1: 23–29.

W. Maranda and M. Piotrowicz, Extraction of thermal model parameters for field-installed photovoltaic module, 2010, 27th International Conference on Microelectronics Proceedings (MIEL) (presented at the 2010 27th International Conference on Microelectronics Proceedings (MIEL), IEEE, 2010), 153-156.

mbask/meteopv documentation built on May 21, 2019, 2:25 p.m.