Green Rooftops / Renewable Energy

Q&A with John Sherborne on Solar Panels


Q&A with John Sherborne – Solar Panels.

The Green Rooftop recently posted about installing solar panels with about John Sherborne.  John worked for BP solar for a number of years before going on to work on solar development and installation in a freelance capacity.

We caught up with him again on May 9th, 2013.

Describe the panels you have installed on your own home.

My house has a nominal four-kilowatt installation.   It’s then de-rated by multiplying by something like 0.7 (I can’t remember what the exact figure is).  It’s de- rated because we’re further north than the tropics. Panels are rated at standard test conditions, which is tropical noonday Sun.  Obviously we don’t see much tropical noonday sun in the UK, we only see about 0.78 of that.

How do you go about installing solar panels on a house?

There’s a lot of preparation work that does get them behind the scenes before you actually begin the installation. Checking that the house is not a listed property and that you’re not in a special development area, that there are no planning constraints.  There aren’t normally, but just occasionally there are.  Even if there are it doesn’t mean you can’t do it, but it does mean you may need additional permissions.

You also need to check that the roof isn’t going to be shaded significantly at some part of the day, so large chimney stacks vents, cowling, large trees in the garden all of those things you need to consider.

You need to check the orientation of the roof the angle of the roof, of course the closer the angle is to a true east-west line the better. Once you’ve established that the site is suitable you also have to check that the electrical supply characteristics are suitable, and survey a cable route through the house.  Sometimes that’s outside the house, sometimes it’s taken down through the inside of the house.

Then you have to book scaffolding and contractors to carry out the work, and test the work. Various tests are scheduled – there are DC tests on the photovoltaic size and also AC tests on the main side.   And then sundry paperwork has to be filled in to notify the distributor network operators that you have installed solar panels on your house.

How much of an impact did installing your array actually have on your electricity bill? 

Approximately half our electricity bill as a straw poll.  Our summer quarters are virtually zero in that we use about as much as we generate.  Winter quarters obviously less so.  This month we’ve already generated nearly as much as the whole last month –just a few good days of sunshine.  We’re getting near to summer; the sun is well up in the sky and once you’ve got some good clear cloud-free days it really zips away.  25 kWh per day has been the last few days’ production, typically.

The worst months performance was in December and January of around 80 kWh and best month was June, July, August at around 400’s to 450 kWh at a maximum.

April has done around 400 kWh this year and in May we have some 150 kWh already.

How long have you been working in photovoltaics?

Well I first started working in photovoltaics in 1986, and BP solar was established well before that.  The earliest BP involvement in renewables was in the early 70s, and that was in solar thermal, looking at it as a vehicle for producing solar hot water collectors by a direct moulded plastic.  They then formed a joint venture with Lucas batteries to produce professional power supplies for remote area equipment.   So in those early days it would have been microwaves, computer stations, telecommunications equipment generally.  Navigation aids, and rural electrification programs funded by people like the World Health Organisation and the likes.  Solar powered vaccine fridges were big things in the early days, for small hospitals and the like.  And grid connected domestic installations just didn’t exist at that time.

I think the earliest grid-connecting array [in the UK] was probably…Dr Susan Roaf.  She had a house built that had a load of PV panels in it in 1995, just a couple of kilowatts.  And it made real waves; I don’t think she was allowed to connect it for a while.  It was a significant event; she forced the issue by building it.  She had the voice to say out loud… she was a power, an inspiration – I’m not quite sure what the right adjective is.

But really grid connect was largely driven by German interest.

How far would you say the UK is behind Germany? 

I think the… Germany has had nearly 20 years head start.  All the significant manufacturers of equipment, not necessarily panels but inverters, cabling systems, are German companies.  There are some American companies, but the significant ones are German, German or Swiss.

What’s your take on solar thermal?  I’ve seen a lot of it in Switzerland but not a lot in the UK.

There are people that install solar thermal…there are two issues with solar thermal in my mind, I think it’s been very badly sold over the years, and it’s very difficult to substantiate the claims.  With solar voltaics, if you install it and you say well I’m going to get this amount of power out of it, you jolly well know you’ll get that much.  If you apply the right amount of light level you can measure performance within an array and say, “yes, I’m getting it”.  You just see your energy meter accumulating kWh, you know what you’ve produced.  And it’s instantly useable by anyone anywhere.  Whereas if you produce a bit of hot water the only person who can use it is you, you see, you’re not going to export it.

And I think the quality of the systems out there are relatively poor.  I mean, there are some that are good.  I’ve been doing some work with a customer recently who’s got a solar hot water system on his roof.  And it’s quite clear he still has to use his boiler and his immersion heater to get hot water, it’s not meeting his household requirements.

So I know there’s a lot of talk out there about the green initiative.  Certainly my advice to anyone contemplating installing would be to look at the PV situation and don’t get your fingers burnt.  And PV is a much more reliable bet.

What’s the current state of solar power in the UK?

The ongoing scenario is a general state of not very much, really.  At the height of the PD boom there were new companies springing up like a rash, lots of companies that were jumping on the bandwagon, suppliers announcing that they were now producing whizzier, better, easier to use bits of kit, test equipment…  Manufacturers were making things.  Everybody was going for it, and it was all “very exciting, it’s a great area”.

Now of course it’s skidded to a halt. And the people who jumped on it because it was a craze business got their fingers burnt, and the people you were in it anyway (for ethical grounds, or had some kind of longer term commitment to seeing it happen) obviously had to tighten their belts, but are still there.  I mean for a long time PV used to be a world of open toed sandals and logger weavers but it isn’t any longer.

What do you think of the Feed in tariff arrangement?

The UK feed in tariff arrangement – you’re paid the feed in tariff, but you’re also paid a small sum for what you actually generate.  Assuming you export 50% of what you generate you get 3p per kWh effectively, which I think is pretty poultry.  I think it would have made more sense to have a less generous feed-in tariff to address the capital cost of the installation and a more honest pro-rata feed in tariff for the energy actually generated.

Could you explain that in more detail?

If you buy electricity from the electricity company you pay 14-15p per kWh.  It’s on the electricity bill you’re paying it, I pay it, everyone pays the electricity board a certain amount per kWh of electricity.  Now I think what they should have done is allow you to get credit at that rate and run a plus or minus account.

Separately, according to your install capacity, you are paid a nominal subsidy for a suitable period to cover the investment of putting panels in.

Now the feed in tariff changed from being of the order of 43p per kilowatt hour  installed to about 20p, and then it’s gone down again since that.  I don’t know by how much but it was a radical cutback. That has a direct impact on the payback period.   Based on the feed in tariff as was, our payback period from our installation would be something like 8-9 years in.  Now it would have a period of 10 to 15 years, and a payback period of 15 years is quite a long period, I mean how many people are going to be sure of still living in the same house in 15 years time?

Also because the feed in tariff has no bearing on what I actually produce I have no incentive to actually export electricity.  They let me generate it but they’re not making it attractive to me to export it.  It’s actually better for me to use my own solar generated electricity than to export it.

If I use my own electricity I use it at cost.  If I buy it off them it costs 14-15 p, whereas if I sell it to them I only get 3p.  No brainer, isn’t it?

By Philippa Hobbs


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