Continue reading »]]> I have the IEC TC82 solar PV meeting all next week. We will be mostly working on four main documents:

IEC62548 – Design Requirements for Photovoltaic (PV) Arrays

This new IEC standard is nearly ready for final vote and has been the subject to a great deal of scrutiny around the world. While it will take a while until we potentially see it appear as a British Standard, I have been striving to make sure that the forthcoming edition of the PV guide here in the UK is aligned as far as possible with the requirements of 62548. There are likely to be a few differences, the biggest single one looking to be the approach taken to array frame earthing.

IEC62446 – Grid connected PV systems – minimum requirements for system documentation, commissioning tests and inspection

We have just embarked on the process that will produce Edition 2 of this existing standard (BS EN62446 here in the UK). We are looking to expand the remit slightly to encompass a wider range of test and commissioning regimes that can be applied to larger and more complex systems.

IEC62748 – PV on buildings

This is a piece of work that has only been approved relatively recently. We have a working draft, but there is much to be discussed next week

IEC 62738 – Design guidelines and recommendations for photovoltaic power plants

This was approved at more or less the same time as the PV on Buildings document – and is more or less at the same stage in the development process … again much to discuss

Continue reading »]]> Fairly understandably, I am getting a large number of enquires on the likely publication date for Edition 3 of the solar PV installation guide. The short answer is that I don’t know – but there is an MCS PV working group this Thursday that will hopefully provide the answer.

The delay to the guide has been due to the series of “gold rushes” caused by recent FIT changes … most of the editorial team have been extremely busy. It is not an ideal situation and the whole process has taken much longer than originally anticipated – but hopefully it is a situation we will sort on Thursday.

The good news is that the guide very nearly complete. Since the publication of the draft, all the comments MCS received have been individually considered and addressed. The final outstanding significant piece of work is agreement on the annual energy performance calculation – and an attempt to align with the forthcoming changes to SAP. This has involved discussion with the SAP team and we now have a series of data tables that need to be discussed and agreed on Thursday. There are a few other smaller items needing addressing, but nothing I consider that can’t be dealt with during the meeting.

Once the text is finalised, the guide will then be sent over to the designers – and hopefully we will then be able to fairly accurately identify a completion date. Watch this space !

Array frame earthing and transformer-less inverters

One reason I am frequently asked about the publication date for the new guide is due to the proposed changes to array frame earthing on systems with transformer-less inverters. This section of the guide has not changed significantly from the published draft and I do not foresee any alterations prior to publication. As the new (draft) guidelines are widely accepted throughout the industry many of the MCS certification bodies (eg Elecsa) permit installers to operate to the new guidelines. My message to any installers who ask about this, is to suggest talking to their certification body and seeing if the CB can provide, in writing, that you can follow the new guidelines.

Continue reading »]]> IEC 62446 Grid connected PV systems – minimum requirements for system documentation, commissioning tests and inspection

I am working on Edition 2 of IEC 62446 today … does anyone out there have any suggestions for things we need to add, remove or edit?

As well as correcting a few typos in the original, the general plan is to expand the document to include a wider range of system test and inspection regimes to encompass larger and more complex PV systems. IV curve tracing is an example of the sort of test we are looking to add, but there may be more suggestions out there …

Continue reading »]]> Over the last couple of years I have been participating in an MCS working group that addresses roofing and mounting issues for solar PV and solar thermal systems. This work has led to the publication of MCS 012 – Product Certification Scheme Requirements: Pitched Roof Installation Kits – Issue 1.0. The document, which was published last week, can be downloaded here.

MCS012 identifies “the evaluation and assessment requirements and practices for the purposes of certification and listing of installation kits for pitched roof mounted Solar PV Modules and Solar Collectors”. MCS012 will become a mandatory requirement in 18 months’ time (September 2013) … ie to comply with MCS, a PV system on a pitched roof will need to feature MCS005 listed panels, fitted by an MCS certified installer, using an MCS012 listed mounting system.

For integrated products like PV tiles, this means that the PV tile will need to have both an MCS012 and MCS005 listing. For on-top systems, just the mounting system will need to be MCS012 listed.

MCS012 provides a means for a manufacturer to demonstrate that a product meets various requirements of the Building Regulations and addresses three issues:

• Resistance to wind uplift
• Weather-tightness
• Fire rating

Resistance to Wind Uplift

The wind uplift test verifies the rated wind load for the system in question. No minimum value is required under MCS012. For systems that have a choice of fixing specifications (eg systems that require more roof brackets as wind loads increase) – a table showing the rated loads for each fixing specification will be produced.

The test involves fitting the PV product to a test roof and then applying increasing loads to the PV modules until failure occurs. Various failure modes are examined, from complete structural failure (something breaks or pulls out) to a functional failure which results in a residual gap of greater than 5mm in the roof tiles or other covering under test.

Weather tightness

The purpose of the weather-tightness test is to ensure the mounting of the PV array on or in the roof does not decrease the weather performance of the declared roof type(s). Various tests are described within MCS012, including a deluge test on a sample roof.

Fire rating

For integrated PV systems, MCS012 requires the product to be tested in accordance with BS476 part 3 – external spread of flame. For on-top systems, no testing is required if the roof covering it is used with is non-combustible (as defined in the Building Regulations).

Finally, it is worth pointing out that there are also to be a number of roofing related requirements incorporated into the forthcoming re-write of the PV guide. These include a section that determines when and how “bolt through” type fixing systems can be implemented.

Continue reading »]]> The Supreme Court has today refused the Department of Energy and Climate Change (DECC) permission to appeal the Court of Appeal’s judgement on the feed in tariff

 This means that all systems installed between December 12, 2011 and March 3, 2012 will receive the original higher FIT rates for  25 years.

More on this story can be found here

Continue reading »]]> I have been one of the speakers at the Solar Power UK – Coping with the Cuts road-show that has been running over the last few weeks … talking partly about the forthcoming changes to the PV guide and partly about Energy Performance Certificates (EPCs). EPCs are obviously very much in the mind of UK PV installers at the moment – given the requirement for Band D that will come into force for FIT applications from April 1st.

So what is an EPC?

An EPC tells you how energy efficient a building is and its impact on the environment. It is derived from assessment of the fuel cost per m2. For existing dwellings, the EPC is not based on actual energy usage, but standard assumptions of:

• Occupancy rates (based on the floor area)
• Assumed heating & electricity usage (based on the occupancy rate)
• Average fuel costs

The process for providing an EPC requires a certified assessor performing a site visit then inputting the data into an approved software program. For existing domestic properties, the assessor will look at the dimensions of property, the heating system, and then record details of items including loft insulation, wall insulation and windows. This data will then be fed into a software program that runs a reduced SAP (rdSAP) calculation.

Can the PV system count towards the EPC rating?

The short answer is yes … providing (as covered in an earlier post), the EPC is done after the PV installation and the EPC certificate is provided to the FIT Licensee at the time they process the FIT application.

Given this, a common question I am being asked is – “how many points will the PV system give me when calculation the EPC”. Unfortuanely there is no easy answer to this question as the point gain will vary and will depend on the property and the EPC rating before the installation. The only way to tell for sure is to feed the data into the rdSAP software.

Some other common questions …

•  Once the FIT application is processed, you can’t do improvements then re-submit for a higher FIT
• If a property has no EPC, or if the EPC is E or lower – then a 9p/kWh FIT rate applies
• The EPC requirement applies to domestic and non domestic buildings. It also applies to holiday lets.
• If the PV on a barn, which is wired to a house … an EPC needed on the house
• The only EPC exemption is where a customer can “demonstrate that it is not possible to obtain an EPC certificate for the building to which the solar PV installation is attached or wired “

Getting qualified

A typical process for becoming a Domestic Energy Assessor (DEA) is as follows …

• 3 days of initial training – assumes experience of surveying buildings
• Portfolio building – at least 5 surveys on different building types
• 1 day – exam & witnessed assessment

During the process, the assessors will need to become familiar with building features including:

• Types of boilers – controls and efficiency
• Wall construction – solid walls, cavity walls, timber frames
• Roofs – insulation and coverings
• Windows – type and materials
• Utility services – electricity, gas, water
• Central Heating – types and controls

Continue reading »]]> DECC has published some FAQ’s on the Feed in tariff …  FIT FAQs

This includes an answer to the question that many folk have asked over the last few days regarding the requirement to have a band D Energy Performance Cerificate (EPC) …

“Can I install the solar PV system to get a band D – and then apply for the FIT?”

The answer is, broadly, yes.

Timing will be everything – the DECC FAQ answer goes on to say that a generator must be able to provide as part of their FIT application an EPC certificate showing band D or above

Continue reading »]]> I have recently Just come across PV module that’s marketed as 235Wp +7% to +12%

To me that’s a 251Wp module with 0-5% variation in output

At first I was thinking – perhaps this is just marketing hype – but on reflection I am not so sure it isn’t more significant …

The module rating ultimately effects what FIT band a completed system falls into

• An array of 16 of these modules – according to the manufacturer – is rated at 3.76kWp >>> the highest FIT tariff band
• An array of 16 of these modules – at 251kWp each – is rated at 4.016kWp >> a lower tariff band

Obviously the larger the system – the bigger the impact. And if this principle is acceptable … what’s to stop a manufacturer rating a module at +20% to +25%

Continue reading »]]> One thing is certain about the Feed in Tariff at the moment – there is currently a lot of uncertainty!

FIT rates were not originally scheduled to be changed before 1st April 2012, yet at the end of October, in launching a consultation on the FIT scheme, the Government announced significant cuts to the FIT rates to come into effect on the 12th December 2011. This date was before the December 23rd closing date of the consultation period.

In a case heard in the High Court on 21st December – the judge agreed that the proposals to cut FIT payments before the official consultation closed were unlawful. DECC lodged an appeal against this decision. The Court of Appeal heard this case on January 13th and came back rejecting the appeal on January 25th. Following this failure, DECC announced: “The Court of Appeal has upheld the High Court ruling on FITs albeit on different grounds – we disagree and are seeking permission to appeal to the Supreme Court.” No formal appeal has yet been lodged.

While all this was happening, on January 19th DECC laid before Parliament an order which, regardless of the outcome of the appeal process, will set FIT rates for PV systems with an eligibility date after 3rd March 2012 to the lower levels as published in the consultation document.

So …

•  if the Government wins on appeal, we are where we were before legal action began, i.e. the Government will continue with the consultation process, DECC will respond to the consultation, and FIT rates are very likely to drop to the rates listed in the consultation document.
• If the Government does not win on appeal, then the 43p tariff looks set to remain in place for all registered installations until 3rd March.

Given all this, about the only thing we can state for certain is that any PV system installed from 12th December will get a FIT payment of at least those values published in the consultation document (e.g. 21p/kWh for 0 – 4kWp retrofit installations).

Continue reading »]]> The Standard Assessment Procedure (SAP) is used to assess the energy performance of dwellings and includes a section to estimate the annual performance of a solar PV system. PV installers should be very familiar with the PV – SAP calculation as it is the method currently proscribed under the Microgeneration Certification Scheme (MCS).

A proposed revision to SAP – SAP 2012 – is out for comment at the moment >> SAP 2012

The most significant change to the solar PV performance calculation procedure in the draft of SAP 2012 is a wholly new means to obtain the annual solar radiation for the site in question. Previously, SAP made no allowance for geographic location and a simple look-up table gave the values as shown below:

 SAP 2012 provides 21 different zones around the UK and proscribes a series of steps to generate the solar radiation value for each of these areas. As such it provides a much more region specific value for solar radiation. Examples for a couple of these zones in the same tabular format as the present SAP-2009 table are shown below (calculated from the draft SAP2012 procedure):

While this change should provide more accurate results, it is in my opinion spoilt by the retention of my least favourite table – table H2 – the Overshading factor. Solar PV systems are significantly affected by shade, so shade considerations form a big part in the assessment of any PV site. The SAP table simply allows for the selection of 4 options:

• None or very little shade (<20% of sky blocked by obstacles)
• Modest shade (20-60% of sky blocked by obstacles)
• Significant shade (>60% -80% of sky blocked by obstacles)
• Heavy shade (<80% of sky blocked by obstacles)

The “percentage of sky blocked by obstacles” is a very poorly defined term and in our experience is both very hard to determine and also very open to miss-use or variations in interpretation. Retaining this simplistic assessment of shade for PV systems seems at odds with the now improved methodology for assessing the solar radiation.

Solutions are of course difficult. We are currently trying to define a procedure for the new PV guide – see my earlier post.

The SAP 2012 consultation closes on 28 March.