Solar PV advice sought

[Eric The Viking]

As the OP (from over 18 months ago) I'll also add our update.

When we saw the Feed in Tariff rates for PV we also thought it might be worth pursuing, so we started investigating the feasibility/options back in March. This is not a DIY option but has to be installed by approved contractors using approved equipment so it isn't a cheap 'on a whim' purchase.

Anyway, we finally ended up with a 3.25KW notional power system that was installed in August. The actual maximum output of mains power we get is 90% at just over 2.8KW - so far we have generated just over 500kW.

Do you mean 500kWh (kilowatt-hours)? (kilowatts are a rate of energy production or use, not a quantity).

Assuming kWh, and that 45 days have elapsed since installation (mid- August to mid- September plus two weeks and a bit), that gives an average power output of less than 0.5kW. Assuming you can only generate effectively for 8hours/day, it rises to roughly 1.5kW when it's working. I think the figure you're measuring is the peak output.

I've got a few questions:

1. Do you have a large battery array and an inverter, so that you can store what you produce?

2. Do you 'sell' to the grid, if so at what rate? Are you required to remit the 5%VAT to the government?

3. How much did the installation cost, and was there any sort of guarantee on output and longevity?

I have 8sqm of water heating panels on our roof. It's usable even in the depths of winter (when the sun is shining), but I can't store sufficient hot water to take full advantage of it.

Was it cost effective for us? That's hard to answer because the energy produced is very hard to measure. It cost around £4,000 to install, but some elements of the system were already in place (boiler and tank in proximity to the roof). We also scheduled the work to coincide with scaffolding being up, so that cost was spread. Our gas bills are very small in the summer (about a fivefold difference from winter quarter's usage), but it's not quite enough at present to cover the morning household dash to the showers. It is, however, long-lived, very simple in technology terms, and very low maintenance. I intend to 'upgrade' it with an additional water tank when I can, part of the delay is cost, part because I can't work out a suitable plumbing arrangement at the moment.

 

[RogerS]

There's the rub. All these 'high-tech' (as compared to a load of oft insulation) options have a really poor cost-benefit-analysis with payback times in eons.

I'm with Mike Garnham on this...anyone for a PassivHaus?

 

[misterfish]

Right - yes I do mean kWh, so we have generated over half a megawatt.

We did look into the possibility of having a large battery array, but the cost and maintainance of the batteries was somewhat prohibitative and suitable control/switching equipment was not readily available. The recommendation was that if we suffer lots of power cuts that the most cost effective solution was to obtain a diesel generator - but our mains supply is OK.

The way it works is that when generating power we use what what we produce and any excess is exported to the grid. If not generating enough we top up from the grid.

As it is solar PV it only generates when light falls on the panels - basically the brighter the sun the more power produced.

As for payments. The Feed in Tariff for PV is 41.3p per kWh generated, irrespective of whether we use or export the power. On top of this is a payment of (about) 3p per kWh per unit exported to the grid. Currently the electricity board meter cannot register exported power (which will change when smartmeters are installed 'in the next few years'. Until this time it is 'assumed' that half of what we generate is exported.

So we actually receive 42.8p per unit generated. This rate is index linked to inflation and guaranteed for 25 years (if you believe government promises). Also any payments made are not liable for income tax. So in the last two months we have earned £220 tax free. We remit nothing to the government.

The other thing is that our consumption of power from the grid will reduce and consequently so will our electricity bill.

I'll put together a graph showing our daily production a bit later.

Misterfish

 

[misterfish]

I've kept a spreadsheet of daily production since the system was installed and these are the monthly graphs.

Also, (due to my analytical/geeky nature) I've now

I've had a datalogger attached to the system for nearly three weeks - this allows recording of production values every 5 minutes!

Misterfish

 

[dickm]

Interesting, Misterfish. Don't think we will get quite as much up here in the short days, but in summer, when it hardly get's dark, we might catch up! So far, we've only managed 29kWhr over 5 days, but it's been real dreich most of that time. Unfortunately, our roof is only 30 degrees, not the 60 that is recommended for our latitude, so we can never hope to generate the rated 3.9kW, but I'm happy so far.

At the moment, I can't see another investment that is likely to make the same return (it's PROBABLY also the most "green", but s*d that if the economics make sense :twisted: )

 

[Eric The Viking]

Right - yes I do mean kWh, so we have generated over half a megawatt-hour...

... We did look into the possibility of having a large battery array, but the cost and maintainance of the batteries was somewhat prohibitative and suitable control/switching equipment was not readily available. The recommendation was that if we suffer lots of power cuts that the most cost effective solution was to obtain a diesel generator - but our mains supply is OK.

It's not for power-cuts specifically, but for night time. You must already have the locked inverter (solar cells are DC output), so a battery farm ought to be straightforward. Although that might cause you to fall foul of all the HSE regulations for battery rooms - tiled walls, special drainage, ventilation, etc. Lead acid is very low maintenance, as long as it's the right sort (will stand deep discharge etc.). The wet alkaline ones are even better, but nastier chemistry.

As for payments. The Feed in Tariff for PV is 41.3p per kWh generated, irrespective of whether we use or export the power. On top of this is a payment of (about) 3p per kWh per unit exported to the grid.

Flippin' 'eck! At that rate I ought to be billing SWEB for the solar panel I've got to trickle-charge the bike battery! Seriously, that means there is no incentive to store (or use) any of the energy you produce at all, since it's much more valuable to you sold-on to the grid.

Disconnect the house from the solar system and sell all of it!

Currently the electricity board meter cannot register exported power (which will change when smartmeters are installed 'in the next few years'. Until this time it is 'assumed' that half of what we generate is exported.

I thought you could wire them up to run backwards! At least, that's the way it's done on some of the estates round 'ere. Why don't they simply put one meter on your array's output and compare that with the standard one on the incoming supply? The difference is what you use over what you generate, or vice-versa, depending on whichever is the bigger number.

But as I said, it doesn't make economic sense to actually use any of it yourself!

I'll put together a graph showing our daily production a bit later.

Seriously (again), that will be very interesting.

I have to say though that it sounds complete nonsense in absolute economic terms - what were they thinking when they set the scheme up??? That rate is getting on for 5x the normal rate per consumer unit (must check my bill), which is hardly efficient (from everybody else's perspective!).

You also didn't say how much it cost to put in - a ballpark figure would be interesting. One idea that strikes me is that, since nobody's getting any decent return from deposits and shares at the moment, this might actually be a worthwhile investment in real terms, provided you really can sell the output to the grid for the foreseeable future

 

[Eric The Viking]

I've kept a spreadsheet of daily production since the system was installed and these are the monthly graphs.

Also, (due to my analytical/geeky nature) I've now

I've had a datalogger attached to the system for nearly three weeks - this allows recording of production values every 5 minutes!

Misterfish

I think my earlier post 'crossed' with yours. It certainly shows how gloomy September was! Out of idle curiosity, at what angle are they to the horizontal, roughly? I only ask because October seems surprisingly good so far (on the sunniest days). I'm assuming that's because the array is more perpendicular to the sunlight at the moment.

 

[misterfish]

The idea of the batteries to provide 'dark hours' power was included in our original wish list, but at this early adopter stage (at least as far as the UK is concerned) suitable and approved equipment is not available (unfortunately).

Now as far as the payment is concerned, the 41.3p per kWh is not a payment for the actual electricity but is a payment for green generation for the whole of the UK - it's to do with the legally binding EU/international undertakings given by the government to reduce carbon emmisions by at least 20% by 2020. Apparently if the UK doesn't attain its targets there are huge financial penalties that the country will have to pay. Hence this feed in tariff (FIT) payment is to encourage people to do their bit towards the target.

The actual electricity we produce is ours to do with as we wish. It is an option (renewable annually) to sell the excess back to the grid via the FIT scheme. Our electricity board supply meter is a digital device and unable to run backwards, but some of the older meters (those with the rotating disk) I believe can run backwards. Attached to our system is an approved 'total generation meter' that is used to calculate our payment.

We spent about 19K on our system of 15 panels and extra monitoring equipment. The panels are guaranteed for a long period (something like 20 years) and the inverter for 5 years.

The rear of our property faces SSW and part of the whole process was a critical analysis of shading to ensure the panels receive at least 6 hours per day of sun (cloud permitting). Part of the installation and certification of the system is an expected average annual output which in our case is 2580kWh

Our 15 panels (each rated at 215 watts) are split into 3 strings of 5 panels with 5 on the main roof (at about 43 degrees) and 2 lots of 5 on the flat roof of the granny annex/sun room. Those on the flat roof are at a much shallower angle. The software/hardware equipment used during the site evaluation allows tweaking of angles to give the best output. As the angles of our panels vary it will give a more equal output throughout the year. This shows what it looks like.

One of our early concerns was the requirement or not for planning permission as the rules had been changed to include solar panels in permitted development. Our property is considered to be in a 'strategic gap', is within the Chichecter Harbour area of outstanding beauty but outside of the Chichester Harbour conservation area. We took photos of what we were looking to do and spent an hour at the council offices with the duty planning officer. If we had been in the conservation area we would have needed planning permission. If the panels protruded more than 200mm above the ridge of the house or overhung the back of the property by more than 200mm the planning permission would be required. It was reassuring to see that the council offices in Chichester had their own PV system with a large internal production display and to then be told that they encouraged such systems.

I'll read back over the thread and see what other questions I've missed and answer them a bit later.

Misterfish

 

[samharber]

*) The human contribution to climate change is debatable to say the least and tiny in comparison to the contribution of natural processes like volcanic activity, rotting vegetation, solar activity, variations in the density or space, distribution of rain fall.

Without wanting to go off at a major tangent, this is palpably false.
There is no debate* as to whether or not humans are contributing to climate change. We are. The main debates are what the feedback mechanisms are and how the CO2 parts per million can be reduced to a (comparatively) safe level.
Both the US Geological Survey and the Royal Geological Society have recently shown that annual human CO2 output is massively greater than the average annual volcanic emmissions (that also have global cooling effects). Also, rotting vegetation, solar activity etc are all part of the background state and would take place at pretty much the same rate regardless.

I now return you to your scheduled programming.

*There's no debate amongst climate scientists, but a lot of poor quality argument from non scientists.

 

[wobblycogs]

Very interesting Misterfish, thanks for telling us about your system. I've kept an eye on the technology for years now but not the economics of it. It sounds like if you have a south'ish facing roof it's viable to have PV generally.

One thing I was wondering though, how come you didn't have all the panels installed on your roof. The majority seem to be on the flat roof which surely don't generate as much. Are they panels very heavy?

 

[dickm]

As for payments. The Feed in Tariff for PV is 41.3p per kWh generated, irrespective of whether we use or export the power. On top of this is a payment of (about) 3p per kWh per unit exported to the grid.

Flippin' 'eck! At that rate I ought to be billing SWEB for the solar panel I've got to trickle-charge the bike battery! Seriously, that means there is no incentive to store (or use) any of the energy you produce at all, since it's much more valuable to you sold-on to the grid.

I have to say though that it sounds complete nonsense in absolute economic terms - what were they thinking when they set the scheme up??? That rate is getting on for 5x the normal rate per consumer unit (must check my bill), which is hardly efficient (from everybody else's perspective!).

You also didn't say how much it cost to put in - a ballpark figure would be interesting. One idea that strikes me is that, since nobody's getting any decent return from deposits and shares at the moment, this might actually be a worthwhile investment in real terms, provided you really can sell the output to the grid for the foreseeable future

Like I said in my earlier post, financially it's too good to be true! But it seems it is true.
And the FIT is guaranteed not to reduce for 25 years. Hence (although I do have a greenish conscience) our decision that it made complete sense to invest. Our system is rated at 3.9kW, and cost about £14k. It's made up of 17 panels, each about 1.5 by 1m, on a roof that faces due south. Unfortunately, not quite steep enough pitch, but setting the panels more vertical would have cost a lot, and might not be a good idea given the windspeeds round here (now, could I fit a turbine mast in the corner of the garden??). Planning is not a problem, because recent legislation makes renewable generation systems a permitted development in almost all areas. You do still have to work within Building Regs, and it probably makes sense to get a structural survey to be absolutely sure your roof is strong enough (don't get the charlatan who did our survey - but that's another story).

With regard to the "green" aspects, an old academic friend tried to convince me that the carbon cost of manufacturing the panels outweighed the likely lifetime savings, but the latest figures I've seen indicate that the "carbon payback" is about the same as the economic one, around 7 years under good conditions.

 

[misterfish]

The panels we have are Sanyo HIP-215NKHE1 - they are 798 x 1580mm and each weigh 15kg. http://www.coolpower.ie/products/datash ... Series.pdf The mains connected inverter is a Fronius IG30 which allows the input from the three strings of panels. http://www.fronius.com/cps/rde/xchg/SID ... G_HTML.htm . The panels on the flat roof are fixed with an aluminium framework system that is lightweight and strong with most of the parts made by Schuco.

Ideally we would have liked more on the two parts of the main roof but the hipped part of the building that protrudes southwards produces shadows early in the day as does the step between the two parts of the roof and after discussion with the installation company we went with what seemed like the best compromise.

Our installation company were extremely thorough with the survey. The initial phone call to them taking well over 20 minutes looking at Google Earth to check the siting and aspect. The the initial site visit to evaluate shading and potential generation. Then the structure checked by a professional roofer before and after installtion with then doing the necessary work to ensure the watertightness of the flat roof. In fact the whole process was extremely thorough and professional and we would highly recommend Southern Solar.

As Dickm states the payments are guaranteed for 25 years and will rise in line with inflation.

The actual angle of the panels is always a compromise - in summer when the sun is at its highest (and strongest) the panels do best at a low angle, but in winter it's the other way round.

Misterfish

 

[jeffinfrance]

generating electricity is not difficult.

storing electricity is.

the national/global energy providers do not store electricity. electricity is only generated when it is required. if you are generating more electricity than you are using and sell it back to the "grid", where does it go?

oh by the way, anthropogenic global warming does not exist. enjoy your cold winter!

jeff

 

[Eric The Viking]

In fact the whole process was extremely thorough and professional and we would highly recommend Southern Solar.

As would I!

They did our hot water installation very proficiently (see this video for my daughters' overview). I was especially impressed by the tuning of flow rates and setting up the hysteresis control on the system.

I remain unconvinced by the overall value of PV though.

Cheers,

E.

 

[wobblycogs]

There will probably never come a time when we generate more electricity that we need. Any surplus energy generated gets pumped into the grid as you say and used by others.

There are some industries, like aluminium smelting, which use such vast quantities of electricity they have agreements with the grid to draw power only at off peak times, this helps balance the load on the grid throughout the day which helps the power generation companies as it means they need fewer fast on/off (read expensive) generation sources like gas fired power stations to meet peak loads. This means they can have more cheap coal fired (base line) generation.

If the whole country suddenly went PV generation loads of extra power would get put into the grid when the sun shone and it would be used by industry or perhaps even exported to parts of Europe where the sun wasn't shining.

Worst case we could store some of the power. A common large scale energy storage method is called pumped storage where they pump vast quantities of water up to a high level reservoir. Pumped storage like this is a great way to meet sudden spikes in load as it takes only a few minutes to come on-line.

 

[cambournepete]

my brother has just had PV installed on his house in sunny Suffolk.
As he worked for Eastern Electricity all his life and is careful with his cash* it must be worth doing if you plan to stay in your house for a long time.
He's getting a new meter installed as his started running backwards...

*That makes him sound mean - he definitely isn't

 

[misterfish]

I remember seing one of those 'How do they do it' type programs recently on Discovery where they were showing how they keep the electricity supply balanced. They have a steady background supply with other power staions on standby for rapid action when needed (like everybody making a cuppa after Corrie. They included the pumped option to refill reservoirs when excess power was available. It seemed to be a constant tuning to keep the voltage and 50Hz balanced with demand as well as coping with network problems.

Misterfish

 

[Eric The Viking]

I remember seing one of those 'How do they do it' type programs recently on Discovery where they were showing how they keep the electricity supply balanced. They have a steady background supply with other power staions on standby for rapid action when needed (like everybody making a cuppa after Corrie. They included the pumped option to refill reservoirs when excess power was available. It seemed to be a constant tuning to keep the voltage and 50Hz balanced with demand as well as coping with network problems.

Misterfish

That's why Dinorwig, and, I think, Ffestiniog and Cruachan*, are owned by the National Grid Company rather than one of the generators - they are giant 'batteries' rather than generating stations.

Even if we did have more nuclear, there would still be difficulties because the rapid changes in demand are too fast for nuclear stations to easily cope with. I'm not sure how Switzerland does it (IIRC they're almost entirely nuclear), but the risks of not managing the supply-demand relationship properly are either over/under voltage (which blows things up) or a shift in frequency (which also blows things up, and sets the clocks wrong).

Incidentally, does anyone know where the smallest, but arguably most dangerous British reactor was sited? It's not there any more, but I once walked past the window, none the wiser...

Cheers,

E.

*possibly Scottish Hydro.

 

[RogerS]

.....
Incidentally, does anyone know where the smallest, but arguably most dangerous British reactor was sited? It's not there any more, but I once walked past the window, none the wiser...

Cheers,

E.

Sellafield?

 

[wobblycogs]

AIUI nuclear is somewhere between coal and hydro-electric / gas in terms of how long it takes to go from cold to full power (closer to gas though). I would imagine the Switzerland (and to some extent France) cope because they are wired into a single grid that spans most of mainland Europe. It's unlikely that everywhere in Europe will all have a peak demand at exactly the same time so some power trading would sort out any problems.

I would have said probably the most dangerous nuclear plant in the UK is Dounreay as it is getting old and was designed for nuclear experimentation at a time when we didn't fully understand the risks. Decommissioning it is certainly going to be a real challenge. It's a close call between that and Windscale though. You've got to admit that setting fire to a reactor is the mother and father of all bad days at work