Tic & dnc help urgently needed!!

Earthstore · Mar 3, 2012

Thanks chaps, I have read the links that you posted, and I have also read so many other files, just to try to understand this fully, why they have to have so many ammendments for what should be a simple rule is quite beyond me, still guess that is government for you.
TIC and DNC appears to be generic terms used for any type of SSEG, So DNC = power that can be produced- power that is used to produce that power.
I am still not convinced of TIC/DNC for PV, I do take on board your points though, and except that the Inverter makes up part of the system.
When I have time, just for my own peace of mind, I will research this further.
But thank you for all your comments.

mdovey · Mar 3, 2012

Given that DNC is defined to be the TIC less electrical consumed by the plant, so in effect the electrical losses, and since the inverter efficiency or capping is an electrical loss, the DECC view that the TIC is
the output of the panels doesn't seem unreasonable (in effect the output if all the wires have 0% loss and a 100% efficient uncapped inverter). This was certainly what I initial thought was the case before reading these forums.

However, although it has no official weight, I found this document the most convincing analysis - http://www.ownergy.co.uk/library/gosple/F2RCAP1d.pdf

This is almost the DECC view apart from in calculating the TIC of the panels it suggests using PVGIS data for the actual location and aspect of the panels rather than the STC value.

TIC definition
Based on the principles for defining the respective capacity measures in section 3 above, the TIC would be based on the output capability of the solar array given uninterrupted exposure to sunlight over a sustained period at its installed location. Suitable data on which this figure can be based is produced by the European Commission’s Joint Research Centre at Ispra, which maintains a resource called the Photovoltaic Geographical Information System (PVGIS)7.
PVGIS is based on extensive solar energy data throughout Europe. It has facilities to derive for any location and solar array angle three irradiance measures: Global ‘clear sky’ irradiance Global ‘real sky’ irradiance Diffuse ‘real sky’ irradiance
We propose to use the best month’s clear sky irradiance as the basis for the TIC calculation. This is the highest of the three figures, and that which best matches the ‘without interruption’ requirement of the definition.
We will use actual tilt angle and azimuth offset figures for installations constrained by the surface on which they are mounted (e.g. roofs). In the case of stand-alone and ground-mounted PV systems we will use the optimum tilt angle (also given by the PVGIS resource), and assume the array is oriented towards true South.
The TIC will then be calculated as the power output of the solar array at the average irradiance derived in this way.

DNC definition
The net output of a PV system, after conversion of light energy in each solar module, will be affected by configuration factors, such as ‘mismatch’ losses from the series and parallel interconnection of the modules, cable losses, voltage drops in metering and protection devices and the efficiency of the inverter and any other power conditioning equipment.
As described in section 4 above, it is proposed that these factors are deducted from the TIC to derive the DNC.