Two Different Types of PV

[RossThompson87]

Hi,

I am working on an EPC for a school building which has two separate PV arrays fitted by separate installers several years apart from each other.

IES allows you to enter the Area and Azimuth for as many arrays as you like. But what if the properties are different?

If one array is 'monocrystaline silicon' and one is 'polycrystaline' silicon this can't be entered. They both have to be the same.

I appreciate there are a number of work arounds that will get the right answer but then the inputs will look wrong if the project comes for an audit.

Ross

[Complex Potential]

The NCM Modelling Guide 2010, Para 171 states:



Note that it doesn't say anything about having to using the software's in-built methodology for calculating the annual electricity generation. In fact, it makes far more sense to talk about the required annual carbon off-set (a manufacturer will often be happy to give you their predictions on this) than the area/type of PV. You can then fiddle around with the PV settings in IES to match it.

For example, when specifying PV for compliance purposes I will approach a PV manufacturer and say I need to off-set 5000kg of CO2 per year, for example. They will then tell me what PV area that equates to regardless of what IES may think.

Given the above, you could independently work out the annual carbon offset of both arrays combined (perhaps working with the installer/manufacturer) and then fine tune your model to match in whatever manner you see fit.

[RossThompson87]

Hi,

Unfortunately our accreditation body are insistent that we provide the full inputs into IES. Something I can't say I agree with! It may be worth you checking what your own accreditation body say - just so you are covered.

Ross,
Your statement below is accurate, you should not use manufacturers projected data.

Kind Regards
Technical Advisor

From: Thompson, Ross
Sent: 20 March 2013 10:52
Subject: EPC Model IES PV Input

Hi,

Further to our conversation earlier, can you please confirm the following with regards to entering PVs on non-domestic IES projects:
• The IES inputs for array type, panel area etc. need to be obtained.
• It isn’t acceptable to adjust these inputs to give an annual yield that matches that provided by the manufacturer/installer.
• This is the case regardless of the detail of the manufacturer’s modeling or whether they have followed the SAP methodology.

Sorry to be pedantic, I just want email confirmation to share with my colleagues.
Regards
Ross

[Complex Potential]

Hmm... yet another email from an acceditation body that makes no sense at all.

I could put the same type and amount of PV into IES and Tas and they would come up with two different numbers and the NCM Guide does not detail the calculation engine that must be used. Does not compute.