solar panel problems

The Trouble With Commercial Solar

Common Problems with Solar Panels

If you own or occupy a commercial / industrial or other large building the chances are you’ve noticed that other similar buildings around are increasingly sprouting solar panels on their available roof areas.

You may even have investigated whether they may be a good idea for you, or been approached by a sales person trying to interest you in buying them for your building?

So, are solar panels a good idea on large buildings?

The short answer is usually “Yes”, although as ever with renewable technologies, and particularly solar, it’s a case of location, location, location.

It is also significantly more complex to install solar PV into larger buildings than it is onto a house and the bigger the system the more complex it will be.

The UK as a whole is perfectly suitable for installing solar technologies, and although you would of course get more from solar if you lived in southern Spain, we still get easily enough sun here to make it worthwhile, even if you’re far in the north of Scotland. Of course things will stack up better if you’re in Cornwall, but wherever you are there is a good chance that Solar PV will be a good investment just in terms of the sunshine you get where you are. I’ll not dwell too much on this though. Solar PV is now a well established technology in the UK with well over 4GW of installed capacity.

Of much more relevance will be the local environment around your building and the characteristics of the building itself.

There are a number of factors that will make a building either ideal for solar, less than ideal or not really worth the effort and it all comes down to a cost / benefit analysis at the end of the day. One way or another it would always be possible to install solar panels on any old building, and as long as they’re outside and pointing roughly towards the sky they’ll generate some electricity. The goal in deciding whether or not Solar PV is a good fit for your building is finding out whether or not the cost of installing them will be significantly outweighed by the energy they generate and the income and savings that come with that.

There is also the consideration that you are turning your building into a small power station and there are a number of additional complications and regulations that you may not have come across even if you’re familiar with Solar PV systems on houses.

I’ll go into a bit more detail in a moment, but before you read any further the financially minded among you may well be wondering what the prospects are on a typical building in the UK if you’re treating Solar PV as an investment. Solar PV will always be a long term prospect with a design lifetime of 20 to 25 years, but project payback periods will likely be somewhere between 7 and 10 years, with a 20 year IRR of something like 8%-16% under current FiT tariff rates. Not too shabby compared to commercially available investments, although possibly not as favourable as other ways of investing directly in your business. However, Solar PV will count towards your carbon reduction targets, insulate you against electricity price increases and provide a Government backed, index linked income for 20 years.

OK, so enough waffle I suppose. What specific considerations need to be looked at when assessing a building for it’s suitability for a solar PV system. Let’s start by looking at only the building itself and then think about the financial implications of what we find later.

Solar Panels on a Chicken Farm

200kWp Solar PV system installed onto a Chicken Farm

The main thing to always consider with a solar PV system is how much sunlight will it get? Although modern solar panels will generate a useful amount of energy even on cloudy days, they still generate a lot more when they’re in direct sun so we want to choose a site that will maximise that. Throughout most of the UK you’d want the module to be pointing as close to directly South as possible. You’ll also want to put them somewhere where they are not subject to shading cast by close by building, trees, large hills or other things like that as they will all limit the amount of direct sunlight the panels will get. There are some very sophisticated methods for assessing how much sun your modules would get and the impact of any shading that might be unavoidable, and it doesn’t necessarily write off the prospect just because you have some shading or don’t have a roof facing directly South, but in ideal circumstances you’d have a South facing roof with a Pitch of around 35 degrees and no shading.

If you’re reasonably confident that your roof will get enough sun to make a PV system worthwhile then the next thing to consider is that someone will actually have to get up on to the roof and install the panels. To do that they’ll have to be able to safely work on the roof, and to be able to lift all of the material up there in the first place. In almost all cases that means that there will have to be scaffold erected up to roof level. The result of that is that the higher your building is the more expensive the scaffolding is going to be and that makes the PV system itself more expensive, and in some cases impractical to install at all. If the roof you’re looking at backs on to train lines or a canal for example it will be close to impossible to put scaffolding up. In an ideal case then you’re looking for a relatively low roof so that access is not an issue.

Next on the list of things to look for will be the construction type of your roof. The PV modules will need to be fixed to the roof in some manner to stop them blowing away the next time it gets windy, plus the roof needs to be strong enough to take the additional weight of the PV panels and the people working on the roof to fit them. For most roof types this isn’t too much of a problem but if the roof is fragile, or is an old asbestos fibre roof for example, then it’s unlikely that you’ll be able to fit PV panels without replacing the roof which is usually prohibitively expensive, unless you were planning on replacing the roof anyway of course? For common roof types there are a wide range of fixing systems for PV panels that can be used to attached the PV panels without damaging the roof or compromising their weather tightness, although if your roof still hold a warranty from the original installer it’s worth being very careful which of these systems is used as it’s possible the warranty will be invalidated.

However, in order of ease of installation and cost effectiveness the roof types that are best suited to PV systems are:-

Trapezoidal corrugated metal roof solar panels

• Trapezoidal of corrugated metal roofs (built up or sandwich panel systems are equally good)











•Metal standing seamed roofs

Metal standing seamed roofs










Flat Roof solar panel problems

• Flat roofs (although felt roofs can be problematic as the design life of the felt tends to be less than of the PV system)











Concrete & Clay Tiled Roofs for Solar Panels

• Concrete or clay tiled roofs










Solar Panels on Slate Roof

• Slate roofs









Fibre Cement Roofs & Solar Panels

• Fibre cement roofs (problematic if fragile)










Green Roof Solar Panels

• Green roofs (the shading caused by the PV system can kill the green roof, and the fixing systems have to be part of the structure of the building). Solar Panels on thatched roofs don’t have this problem










Those first considerations cover the solar PV panels themselves on the outside of the building, but solar PV system is an electrical technology and the aim of having it installed is to harvest free electricity. That means that you’ll have to plug the whole system into the electrical system of your building and find somewhere to house the electrical equipment that comes with them.

The main electrical component of the PV system apart from the panel is called an Inverter. An inverter is an electrical device that converts the DC electricity generated by the panels to AC electricity as fed into our building by the National Grid. Depending on the size of your PV system you’ll need at least one and often several Inverters which must be housed somewhere. Ideally they would be situated indoors close to where the electricity meter and distribution equipment of the building is, although they can go outside or in something like GRP housings outside the building. They can even go on the roof with the panels although that can cause problems with maintenance later on down the line. Inverters are the element of a PV system which needs the most attention and although they will usually function well for long periods of time with little or no maintenance, if one does become faulty you’ll be losing out on precious generation and the money that comes with it so they should be in a position where they can be checked regularly or connected to a remote monitoring system that will alert you if they break down.

150kWp Solar Inverters

Inverters in a 150kWp solar PV system










Solar Inverters in a large 2000kWp solar PV system

Inverters in a large 2000kWp solar PV system










For the PV system to function it will need to be connected to the national Grid though your main connection point which also means that there will need to be wires run from the roof, down to wherever the inverters are housed and then from there to a final connection point in the existing electrical system of the building, usually in the main distribution board of the building. There is usually a relatively undisruptive way of achieving this but it is possible that a short building shutdown will be needed to safely connect the PV system so you should take this into account when planning how the system will be installed particularly if the building is very sensitive (Hospitals and data centres for example need particular care for obvious reasons).

For all of these questions you should be able to talk to a competent installer to get the answers you need, or there are various consultancy practices around that can guide you through the early stages of deciding whether it’s likely to be worth getting a PV system for your building. It’s usually worth getting expert advice early on if possible as there can be a lot of complications that arise before the system that can be installed and its worth trying to tackle them early on before any serious expense is incurred.

Ok, so I’ve talked about the major components and considerations needed for a larger solar PV system, but because you’re retrofitting a small power station onto your building there are various regulatory checks that have to be made if it’s to be installed safely. Again, a competent installer or consultant will be able to advise you fully on what needs to done, but in brief the approvals and checks that should seek before you begin the installation of a solar PV system are:-

• Your local DNO (Deregulated Network Operator) – these people own and operate the electricity network out in the street and at the sub-station and must give approval before any new generator can be connected to the National Grid, including PV. It is potentially a criminal offence to plug in a generator without their permission. This can be gained through what is called a G59 application which can take up to 13 weeks to be processed.

• The local Planning Authority – permitted development regulations in the UK mean that subject to a few fairly basic conditions, solar PV system do not usually need planning permission to be installed anymore, however if your building is in or close to a conservation area, or is listed or one of a variety of other reasons it may need planning permission granting to be able to install the PV system.

• Your building needs an EPC (Energy Performance Certificate) – because of the way Feed in Tariffs are structured now, if your building has an EPC rating of E or worse you will only get a very low rate paid for the electricity you generate and you should undertake other energy saving measures before you consider PV. Although the solar PV system can count towards the EPC rating that you need it is still strongly recommended that one is carried out well in advance of the PV installation or else you may find yourself with a significantly worse investment that you’d intended.

• A structural survey – Solar PV systems are not usually particularly heavy, but they do still add a reasonable amount of weight to the roof of your building and depending on how well your roof was designed and how much weight has been added to it since then the addition PV system could lead to structural damage if not properly checked, particularly as PV panels will cause some wind uplift on the roof structure that may not have been accounted for in the original structure. It is fairly unlikely that the structure of your roof won’t be able to take the additional weight, but the consequences of installing all of that weight on to a roof that it turns out couldn’t take it could be catastrophic so we’d advise that the additional expense is always worth it. The additional of PV system usually wouldn’t require pre-approval from Building Control (Except in Scotland where it usually does) but a building control officer may still ask to see your structural assessment at a later date so it’s worth having one for that reason as well.

• Asbestos surveys – although the installation of a solar PV system is not all that disruptive, it is still usually necessary to drill holes for cable penetrations and to mount electrical equipment. It is the responsibility of the building owner to ensure that any contractors working in is are safe from Asbestos hazards and although any responsible contractor should make sure on their own behalf, you could still be liable for Asbestos exposure to people working in the building. Consulting an asbestos specialist earl on should mitigate that risk and provide everyone involved with the information needed to carry out a safe installation.

• MCS (Microgeneration Certification Scheme) certification – for most PV systems (anything below 50kWp) your installer must be MCS accredited in order for you to be eligible to claim the Feed in Tariff. If they’re not, then you will lose out on most of the income that you would have gained from the PV system.

• CDM (Construction Design and Management) compliance – all construction activity falls under CDM Health and Safety regulations, but larger PV systems may de CDM declarable and require the engagement of a CDM coordinator, again this is the responsibility of the client (usually the building owner) and must be considered early on in the project.

Essentially the installation of a solar PV system on to any building is a small construction project and sometime not so small a project depending on the size of the building, and they should be carried out with all of the care and attention that you would apply to any new building project. You will also be the owner and operator of a power station for 20 to 25 years which if not built and maintained properly could become a very poor investment. However is built and maintained well, a solar PV system in the right place of the right size will significantly reduce your energy bills and provide a very stable income stream for all of that time.

As with pretty much all construction projects, the more complex a system you’re trying to achieve the more expensive it is likely to be and as you have probably gathered from everything I’ve talked about here there can be a lot of hoops to jump through and a lot of ways to waste money when commissioning a large solar PV system. We would always advise that you consult an expert as early on in the process as you can to be sure that you’re doing everything properly and legally right from the start. If you talk to an experienced installer they will be able to help you, possibly for free in exchange for then having a good chance of installing the system in the end. If your procurement rules make this problematic then there are consultants around that have good PV experience and will be able to help you, although they will likely require a fee up front for the work. It’s also worth being careful which installer or consultant you and ensuring that they have the necessary experience to be able to help with your project and goals. Ask to see a portfolio of PV projects if you’re in any doubt as a lot of general construction companies or consultants may not have the experience needed.