HELP System Design, conflicting sales/ installer advice

[TheChief]

I had loads of hassle with a solar thermal install so am cautious about picking a PV installer. I have read reams of forums/ building regs etc but have no clear answer. Had about 8 sales guys out, all have own opinion so some impartial advice might help me weed out the cowboys. I have a 2 storey extension roof on same plane as main roof facing SSW, but 50mm lower (local building regs nonsense) and a flat roof 6m x 4m on single storey extension. I/ they reckon main+ extension roof can fit maybe 10x 250w panels - 2 of which on the extension roof. There is a hipped roof on the SSW face of building, giving space facing ESE which might fit 1 or 2 panels. There is also a 1 storey flat extension 6m x 4m below, but would likely be shaded in winter by a small tree suffering butt rot which will need to be chopped down in next year or 2 anyway.

1. Do panels on main roof on 1 string (array?) need to be all Landscape or all Portrait or can they be mixed?
2. Can 1 or 2 panels on ESE facing roof be added into the same string without using eg seperate micro inverters?
3. Is the lower height of the extension roof a problem for the main string?
4. Should it be possible to fit a panel across the extension/ original roof join (ie brackets at different heights to offset roof difference)?
5. Does a 'bypass diode in every panel' (SOLAR KING UK) minimise shading/ orientation reduction in output?
6. Any idea whether my flat roof needs structural survey to put 4x 250w panels on it? The original roof will be timber beams across 4m span on top of brick walls, then renovated it had some kingspan added on top then new ply and 'thermoelastic' felt on top, so load would be well spread out.
7. To keep flat roof panels within 200mm of roof, are there brackets/ mounting that could angle them off horizontal at all?

Clearly I want to install as close to 4kw system as possible... Thanks for advice on any of above points.
ps does the 'Install company' (ie the one I am paying) need to have an MCS number, or is it OK for them to sub the work to MCS approved installers?

 

[Worcester]

1. Do panels on main roof on 1 string (array?) need to be all Landscape or all Portrait or can they be mixed?
A: Best design practice dictates that they should all be the same orientation on the same string.

2. Can 1 or 2 panels on ESE facing roof be added into the same string without using eg seperate micro inverters?
A: No though you might be able to use a very small inverter (enecyss micro inverters are on a running two week hold on delivery whilst they fix their quality issues), There are other small string inverters certified for UK use. Not all panels are enecsys compatible.

3. Is the lower height of the extension roof a problem for the main string?
A: No so long as panels are the same orientation (L/P), same elevation and same azimuth (direction N/S etc)

4. Should it be possible to fit a panel across the extension/ original roof join (ie brackets at different heights to offset roof difference)?
A: Depends, is it on the same plane with just the ridge lower, or is there actually a step in the roof surface?
If just a lower ridge, and the roof is solid and the rail is continous it should not be a problem.
If the roof plane is offset, then it would be better practice not to span it, in case of mounting alignment differences. 50mm is a big gap to make up, and may push the height of the panels above the roof to >200mm which will require planning permission.

5. Does a 'bypass diode in every panel' (SOLAR KING UK) minimise shading/ orientation reduction in output?
A: It helps, almost every panel on sale in the UK has at least one by-pass diode, on some panels e.g. Yingli they have 6, a significant number of panels have 3. Any shading will have an impact.

6. Any idea whether my flat roof needs structural survey to put 4x 250w panels on it? The original roof will be timber beams across 4m span on top of brick walls, then renovated it had some kingspan added on top then new ply and 'thermoelastic' felt on top, so load would be well spread out.
A: Good practice dictates that all roofs should have a structural survey and analysis done. On a flat roof it dpends how they are going to mount the panels, they will need either ballasting (extra weight) or bolting down to prevent overturning.
Load will only be spread out if the mounting system spreads it.

7. To keep flat roof panels within 200mm of roof, are there brackets/ mounting that could angle them off horizontal at all?
A: The only system I am aware of is the schletter FixZ-7 system profile that has two different rail heights, on a landscape panel 1m wide it adds 80mm to the height to give about a 5 degree slope. Keeping you just under the 200mm


If the company you contract wiith is NOT MCS regsitered, you do not know who will do the install - they could change it any time, also you are unlikely to be protected by the REAL Assurance scheme - All MCS registered companies MUST belong to and comply with the REAL Assurance Consumer Protection scheme.

If they are not MCS registered you are just dealing with a sales organisation that does not have to comply with any rules or codes of practice . Caveat Emptor

 

[MCS Renewables]

Beware of any company with Solar, Eco, Green or Energy in their name as they have been set up to exploit the PV boom and will probably be gone when the bubble bursts. Try to pick a local tradesman or trades company that still services its original customer base as these will still be trading in years to come. Electricians or plumbers with a good name local to you should be your first choice.
Any company with dedicated salesmen, shops, green energy centres, call centres, are obviously going to be more expensive . Why should you pay for that ?

As a example we can supply an install a 3.84 kW Sanyo, 16 x HIT 240 system with 4000TL and bluetooth, VAT and scaffolding for less than 14K,
Apple windows/conservatories near me, in Dorset, are selling a 2.3 kW system, 10 Moser x 230 system with inverter in loft and installed by subbies for 13.6K.
For virtually the same price the resulting system is either end of the scale.
Do loads of homework and avoid the sharks.

 

[solarsavings]

Beware of any company with Solar, Eco, Green or Energy in their name as they have been set up to exploit the PV boom and will probably be gone when the bubble bursts. Try to pick a local tradesman or trades company that still services its original customer base as these will still be trading in years to come. Electricians or plumbers with a good name local to you should be your first choice.

I started Solar Savings in 2005 when there were few fish let alone sharks about.

 

[TheChief]

Many thanks for comprehensive advice, a common thing to hear is, "well, what do you want installed?" mixed with sales type advice, implying they would install whatever I asked for, regardless. Unfortunately pretty much all installers seem to have rebranded with Solar in name, even if they were long standing business before so hard to discern more solid companies.

FYI I contacted Enecsys at the end of July to check whether an installer was just against the idea of micro inverters, I got this reply;
>We recently noticed an issue with certain sites where the SMI240-60 micro inverters were used. As a direct consequence of this, an investigation was undertaken and resulted in a halting of all production and shipments, including our 72 cell micro inverter range.

We identified the root cause and our in-house team implemented rigorous production and testing processes to ensure that we could resume producing and shipping high quality, reliable products into the marketplace. We also undertook extensive field tests on the newly produced micro inverters to ensure they met the high standard and expectations of our customers. These tests are still ongoing.

As a direct result of this, there has been a delay in production and shipping of the product and therefore all recent orders received were put on hold.

All orders will start shipping again in mid-August and we are hoping that our distributors will be fully restocked with Enecsys micro inverters by the first week in September.

The 72 cell micro inverters have been cleared for release as these were found not to have been affected by the same issue which affected the batch of 60 cell micro inverters, so our distributors have been told to release their stock of 72 cell micro inverters for sale and installation.

I would like to take this opportunity to confirm that if issues were to arise with any of our inverters which have been installed, these will be fully covered by our warranty.

 

[SRE]

Beware of any company with Solar, Eco, Green or Energy in their name as they have been set up to exploit the PV boom and will probably be gone when the bubble bursts. Try to pick a local tradesman or trades company that still services its original customer base as these will still be trading in years to come.

Bit of a sweeping statement! We've been going for 12 months and God forbid have energy in our name .. most of our work comes through customer recommendations, we convert 2 out of 3 sales because we listen to customers and spend time with them, we don't have sales people but we do have a lot of project management experience with contractors who were very well established and had a completely different concept of customer care to the vast majority of customers.

Be careful not to throw out the baby with the bath water. In our area we have a relatively well known pv firm established for 16 years who insist on telling customers that you can throw small bricks at the panels without any problems, don't return customers' calls, take 3 weeks to quote and make sweeping generalisations about shading - would you recommend them because they have a higer profile and have been established longer?? Our customers don't, they have selected us every time we have been in competition with them - our building reputation is all based on honesty.

 

[TheChief]

1. Do panels on main roof on 1 string (array?) need to be all Landscape or all Portrait or can they be mixed?
A: Best design practice dictates that they should all be the same orientation on the same string.

I accept that best practice dictates same orientation, but I have a very awkward roof with 2 velux, soil stack, boiler flue & existing solar thermal panels to work round. In practice, would a mix lead to electrical/ system faults or just a lower generating efficiency, and if the latter, a matter of a few per cent or more than that? In broad terms obviously.

 

[Worcester]

At different orientations, the panels respond diferently in different lighting conditions / orientations. Because of the way the MPP trackers work, you will always be pulled down by the lowest performing panel, so will never get the maximum you could. Electrically it will work, it will simply amount to a lower efficiency under almost all circumstances.

I'm not sure any software can give you the exact answer, I use PV*Sol expert which in some modes will allow you to do that configuration, though SRE or BruceB may be able to give you a better answer on the whole effect.

 

[series530]

Most of us want to get up to the 4KWp because we think it will offer the biggest payback. Buyers are seduced by this. Some of the cowboys just want to bung panels on the roof, charge an amount for them and run. You may get the SAP rate in harvest and you may get more. Equally, a poor design could result in less harvest and will end up costing you more and extending your ROI time. If somebody says that you are better off with a smaller system, don't dismiss them - they could be the ones who will serve you better.

Who knows where any of us will be in 2 years let alone 5 or even 10 - same is true for any company. With this in mind, I would look toward an independent insurance backed warranty. Your installer may not be around but you, at least, have somebody to call upon if something goes wrong.

I fully agree with others - pick a small company. You will most probably get a better service, a cheaper price and somebody who is reliant upon you for referrals. In my opinion, there is nothing wrong and everything right in having the company owner or the technical director doing the home visit and survey. They will care about you and their company. A pure salesman will care about commission and the next sale.

Don't be put off by a company who hasn't done that many installations. I would never want to be one of the first half dozen guinea pigs but, once a company has learned the ropes and honed their product and service they should be no worse than an installer with 100 or 1000 installations behind them.

Whether it be their 10th or their 1000th install, ask for references and follow them up. You can learn so much about them, their work, other installers and the industry.

Finally, and this is the big one as far as I see it: don't buy on price alone. The FIT pays based upon energy harvest and not array capacity and it should pay out for 25 years. The additional cost can be averaged out over 25 years and doesn't necessarily amount to a huge amount more per year in those terms. Better panels, for instance, harvest more power in dull or very bright conditions. Poor cabling causes heat and not harvest. Poor matching between inverters and panels reduces harvest potential. Just because system B may cost £1000 more than system A doesn't mean that you will get a return on investment more quickly with system A. A £1000 more expensive system only needs to harvest about 4% more power to recover your cost over the FIT. End up with a set of dodgy panels with a power output near the bottom of their range and you could loose more than that on that variable alone !

 

[Worcester]

The ROI math are actually quite complicated when done properly, if it was that simple you wouldn't have cheap as chips chinese panels used in all the large commercial installs. It is only critical where you are pushing at a band limit and space is restricted. We design, supply and install at both ends of the spectrum 2.4kWp Sanyo HIT systems and 50kWp Chinese, every product has it's place. The banks are very careful and want to ensure that they get a good rate of return, at the same time they want to minimise the risk to their investment, most of the chinese panels have no problem getting approved on bank backed projects.

Every product has its place in the market, and your ROI will be influenced by
1) Available capital.
2) Cost of system.
3) Size of the system kWp.
4) Size of the system (m2 / are available).
5) Estimated yield.
6) How much of the generated power you will use.
7) Maintenance costs
8) Warranties

N.b. Warranties have a cost associated with them as well (e.g. microinveters may have a 20 year warranty, however if it doesn't cover the labour cost of replacement, then it's value may be negated)

Your final decision (as a domestic consumer) will also be much more affected by brand perception / emotion, than in a commercial install. (Else we wouldn't have so many BMW's around )

 

[TheChief]

Thanks for all above. I recognise that there are many variables affecting the system performance, that's why I'm keen to understand myself some of the factors involved as it is apparent that plenty installers coming round here aren't really considering overall performance but merely want to bung up as many panels as possible. The only sales guy who seemed to do a detailed software analysis was from Solar King UK, he also discussed pertinent issues knowledgeably and took time to explain to me, but I've ruled him out as he offered me a free Ecoflow Gas Fuel 'Conditioner' and I couldn't take him seriously after that. I hate to say it but I can understand people getting Tesco to do it, as people have some degree of trust that they aren't going out of business, and problems will have to be rectified or else their whole business reputation will suffer. I have had 2 decent looking local companies out so far, on the home straight hopefully in deciding.

 

[SolarCity]

I hate to say it but I can understand people getting Tesco to do it, as people have some degree of trust that they aren't going out of business, and problems will have to be rectified or else their whole business reputation will suffer.

Judging by the way the steamroll over communites nationwide with their cut-throat capitalist attitude, I doubt that they'd be that concerned about any 'problems'.

I have no knowledge of their after care service but I'd be very interested to hear what their response would be if one of their installs, for example, was suffering from grid disturbance - a DNO's problem but often only after an installer has brought it to their attention.

I don't like the Tesco approach. It kills the customer/installer relationship, in my opinion, and this can't possibly be a good thing.