Solar Electricity

[hellymedic]

Capital is there, earning little in account, so won't need to borrow. With interest rates as pitiful as they are, spending on anything that may have a better return seems attractive.
Cooker and oven are gas, so electricity does not figure here.
We have no working dishwasher.
There's neither TV nor tumble drier.
Fridge-freezer is old (part of fitted kitchen in situ when I moved in).
Washing machine (Miele cold fill) is used about twice weekly.

Dad is advising me not to get this, which is amost a perverse incentive...

I could become eco-smug...

[The Seldom Killer]

What's your dad's logic?

Worth looking at replacing the fridge freezer, even without the solar panels and even in a fitted kitchen.

Older models can cost more than fifty quid a year more to run than a new applicance so can pay for themselves in 2 - 6 years depending on how fancy you like your white goods.

[hellymedic]

What's your dad's logic?

Worth looking at replacing the fridge freezer, even without the solar panels and even in a fitted kitchen.

Older models can cost more than fifty quid a year more to run than a new applicance so can pay for themselves in 2 - 6 years depending on how fancy you like your white goods.

Dad thinks I could spend the money better; he said I should consider how many holidays I could get for the cash. He is anti-green!
He is also concerned about how dust and dirt affect the panels (fair enough) but I should think the rain would help clean them and thinks there's not enough sun in London. I disagree...
Dad won't trust the government and is concerned guaranteed paybacks may evaporate.

[Wowbagger]

Peter,

your option looks interesting from my pov - except that my immersion heater is also part of the central heating system.  I can't see on the web ppage if this is a prob or not - how does your CH tie into the solar hot water stuff?

It just so happened that when we had it fitted, the old hot water tank disintegrated and we had to buy another one.

The heat exchanger for the central heating is still in place and we can use it if we want - but we never bother to burn gas to heat the water. I think in practice most people turn the hot tap on to wash their hands but have usually finished washing them by the time the hot water comes through.

What happens with the Solartwin version is that cold water is taken out of the bottom of the tank, sent through the panel and fed back into the top. This has the advantage that the usable water gets hot quicker and floats on the cold water, cycling backwards through the system. Also, the whole tankfull gets hot, not just the two-thirds above the heat exchanger. The disadvantage is that you have to have soft water, or a water softener fitted, else the panel will fur up.

Solartwin > Applet - showing basic operation of the Solartwin system shows how it works.

[Tim Hall]

On the shower/water heating tack, is there an argument for staying with an electrically heated shower (as used by Kim's Mum), and just buying "green" electricity?

Surely (wild handwaving) the efficiency of a gert big offshore windfarm is going to be greater than a slack handful of evacuated tubes on the roof?

Any one with Real Facts ^(TM) care to comment?

[simonp]

On the shower/water heating tack, is there an argument for staying with an electrically heated shower (as used by Kim's Mum), and just buying "green" electricity?

Surely (wild handwaving) the efficiency of a gert big offshore windfarm is going to be greater than a slack handful of evacuated tubes on the roof?

Any one with Real Facts ^(TM) care to comment?

I think your typical green tariff is just buying ROCs that would have been generated anyway under the renewables obligation, so I think in reality you're only buying a few % renewable at the moment.

A solar heating panel collects heat from the sun which would otherwise have warmed your roof.  There's no conversion step, basically it's 100% efficient isn't it?  (I suppose there's the energy to run the pump, so in reality it's not).

[inc]

I have double glazing, loft and cavity wall insulation...

Your rep failed to mention a few things. To be eligible for the FIT system your dwelling has to meet minimum energy saving standards, probably much higher than most UK houses. The tariff is 41.5p per kWh and you can also use that generated power and for any you manage to export get another 3p per unit. As others have mentioned shade ( chimney, trees etc) is a big problem for PV as any shade on the panel will reduce it's output significantly, even totally because of the serial wired unit's construction. A lot of people are also surprised that the system will be shutdown during a power cut so it can't feed power into a system the power company thinks is dead. Solar water is very cost effective with a 20 or 30 tube set up providing all or most of a family's hot water from April - Oct. The average home uses around 5000 kWh providing DHW so a big saving.

[The Seldom Killer]

Dad thinks I could spend the money better; he said I should consider how many holidays I could get for the cash. He is anti-green!
He is also concerned about how dust and dirt affect the panels (fair enough) but I should think the rain would help clean them and thinks there's not enough sun in London. I disagree...
Dad won't trust the government and is concerned guaranteed paybacks may evaporate.

Dirt and Dust. The majority of panels that are sold at the moment are finished with self cleaning glass. My understanding of that is that is it microdimpled so that when it is hit by rain the dirt and dust is knocked out and washed away. You should expect to need to clean the panels no more than twice a year. Hardly a burdenous task.

Sun. The solar accumulation maps that have been created from various sources indicated that London should be fine. Tell your dad to work from real facts rather than the letters page of the Daily Mail.

As for the evapouration of the payback period. Either he means we're going to stop getting sunshine, which is ranting lunacy, or he means that the government will pull the carpet on it. Possible, but as this is enacted in legislation that makes it nigh impossible for existing customers. If you get it, you should be fine for your 25 years. Even if it gets pulled after 5 or 6 you'll probably still come out on top.

[The Seldom Killer]

On the shower/water heating tack, is there an argument for staying with an electrically heated shower (as used by Kim's Mum), and just buying "green" electricity?

Surely (wild handwaving) the efficiency of a gert big offshore windfarm is going to be greater than a slack handful of evacuated tubes on the roof?

Any one with Real Facts ^(TM) care to comment?

It all comes down for efficiency for whom and how, which was Monbiot's point when he cam out against FITS. However, for the consumer, not paying for it is always going to be more efficient and economic than paying for it. In a well designed system for solar hot water, there's next to no loss from the panel to the tank and from there on it's equals.

[hellymedic]

I am concerned about the durability of these panels and how easily they could be retained and replaced should we need to reroof the house.
Despite Dad's involvement in photovoltaics over the past 40 years, I think he's wrong...

[The Seldom Killer]

Recent research has made an 85% efficient solar panel that can be mass produced
I am waiting for that, and the availability of ultra capacitors before I fit the stuff on chez vorsprung
We have quite a lot of roof facing south    Not sure if we'd be able to go entirely off grid however.

It's been claimed, but not reasonable demonstrated. Even the Japanese models with a theoretical 40% efficiency have only been able to 14% in laboratory conditions. Not even as good as existing panels and you would have to build your house in a laboratory. I think you can see the fail in this. There have been any number of claims of what the industry terms "messiah" panels. All have fizzled out to naught so far.

As for going off grid entirely. Plausible, but there is a problem. We humans love to use electricity at night, when it isn't being generated. That means you need batteries to be off grid and an energy dump for when the batteries are full. Batteries aren't a good idea and energy dumps aren't much better, on either health, economics or environmental scales. Much easier to have a grid connection and a couple of small boxes in the house doing all of that work instead.

[The Seldom Killer]

 A lot of people are also surprised that the system will be shutdown during a power cut so it can't feed power into a system the power company thinks is dead.

Not always true. Depends on where the company has put the isolation switch and how the system could manage unwanted energy that can't be exported.

[vorsprung]

As for going off grid entirely. Plausible, but there is a problem. We humans love to use electricity at night, when it isn't being generated. That means you need batteries to be off grid and an energy dump for when the batteries are full. Batteries aren't a good idea and energy dumps aren't much better, on either health, economics or environmental scales. Much easier to have a grid connection and a couple of small boxes in the house doing all of that work instead.

I agree about batteries
That's why I mentioned ultracapacitors

[The Seldom Killer]

I am concerned about the durability of these panels and how easily they could be retained and replaced should we need to reroof the house.
Despite Dad's involvement in photovoltaics over the past 40 years, I think he's wrong...

The panels are pretty durable. They are designed to be left outdoors for long periods of time (20-25 years). The rest really comes down to your installer and what system they choose to use.

For instance, the company that I visited for work last week used very simple racking that integrates into the existing structure of the house. It's designed to be quite quick to install and replace. Quick installation is their main objective. It means that they get more profit against the cost of the installation. Quick repair and replacement is a side effect. I reckon no more than a couple of hours to disassemble the roof array if needed. I'll conceed it isn't pretty, but neither is Drax power station and the do the same thing.

[vorsprung]

Recent research has made an 85% efficient solar panel that can be mass produced
I am waiting for that, and the availability of ultra capacitors before I fit the stuff on chez vorsprung
We have quite a lot of roof facing south    Not sure if we'd be able to go entirely off grid however.

It's been claimed, but not reasonable demonstrated. Even the Japanese models with a theoretical 40% efficiency have only been able to 14% in laboratory conditions.

The one I read about seem quite a recent development, not japanese and not using exotic materials

High-efficiency solar cells  | News | The Engineer

[The Seldom Killer]

OK, not read about that yet. Looks interesting and may have potential.

[campagman]

the Centre of Alternative Technology is good for info. Very good for a visit too. This could help.

[Quisling]

Hellymedic, I sell renewable technologies - happy to give impartial advice. Feel free to PM if you have specific questions.  I'm just doing PV at home myself once I get through Building Control.  Things to consider:

1. the FIT rate of 3p for export will be based on DEEMED export of 50% of total generation for installations under 30kWp (typical domestic scale is well under that) so no need for specific export meter, though your installer will advise if your existing import metering needs changing.  Your electricity SUPPLIER (who appoints the meter operator on your behalf) will be able to arrange this if necessary.  If you have an old electro-mechanical import meter it'll need upgrading to a digital meter.

2. Make sure you use a MCS accredited installer and kit, otherwise you won't be FIT eligible.

3. PV prices have dropped a lot this year.  Installed prices for 2kWp are now sub £12k, and some companies are talking nearer £10k, unless you live on the top storey of a block of flats or have tricky site conditions.

4. Typical simple payback under FITS for well sited PV (minimal shading, pitched roof, reasonably south facing) is in the order of 12 years, giving another 13 years of clear income.

5. Inverters - mean time to first failure of inverters is around 10 years, so even if the PV panels are guaranteed for 20 years or more you would need to assume you'll be replacing the inverter at intervals.  This could be £600 - £1200 at current prices. Even so, return on investment is still better than sticking your cash in an ISA at present, and the FIT income is free of tax and index linked.

6. Once you're awarded your FITS this won't be taken away.  The scheme will be reviewed at intervals (3 years I think) at which point the generosity of the scheme may be altered but existing users have "grandfather" rights - i.e. your 41.3p/kWh is guaranteed for the 25 years (+ indexation) so you won't get shafted by shelling out £000's and then find the plug is pulled.

7. to be paid fits you will need to provide regular meter readings - ask your installer or preferred FIT provider whether or not they'll install a smart generation meter which can be remotely read to save you the hassle.

8. All electricity suppliers > 50,000 customers are mandated FIT providers, and have to offer FITS to customers of smaller suppliers (e.g. Green Energy UK) so if you're with a noddy independent supplier you can still access FITS from NPower, E.ON etc.  Try feedintariffenquiries@eonenergy.com if you're an E.ON customer which is their dedicated FIT team.

9. your installer might not mention Building Control.  Some council BC depts don't seem too fussed, but mine insists I submit a Building Notice Application.  Check with your local dept.  Planning permission is a different thing.  PV does have "permitted development rights" which means you don't need planning permission if certain conditions are met (e.g. installation is not facing the road, the house isn't listed or in a conservation area, the panels don't project above the roof line or more than 200mm above the surface of the roof etc.

10. PV panels are generally good for 20 - 30 years with long manufacturers guarantees, though output performance is likely to drop 10-15%+ over the period.

Does that help?

[hellymedic]

Very helpful, thanks Quisling!
My meter is a newish digital job, installed about 4 years ago. It's in a 'cupboard on the front wall - fairly accessible. My back roof faces south-west; the house is a 30s semi with a hipped roof.
Rep thought I could generate about 1.8kW. I'm aware how poor most investment schemes are at present.
One thing that worries me a bit is the fact I may need to move into another house as my MS worsens. I presume any future buyer would inherit my FIT.

[Quisling]

I think it's your call what you do with the FIT.  You can re-assign the FIT to a third party I believe.  If you're going to re-assign the benefit to the new householder then you'd want to "sell" the remaining benefit (or a proportion of it) as a consideration into the valuation of the property.

The other option is that you sell the house at market rate and then continue to pocket the FIT BUT that's risky, since you have no access to maintain the system - replace the inverter when it fails etc so that would be problematic.

It's not so crucial that you have south facing roof like it is for solar hot water.  Obviously the output from the system will be less, but if you're SW facing it just means you'll hit peak generation in the afternoon which frankly is more usable for most people who are out during the day.

The optimum benefit you'll get is by using 100% of the output but still be being paid for 50% export!  I heartily recommend paying extra for an output display for the PV, something like a SMA Sunny Beam wireless unit Reviews: SMA Sunny Beam Display
If you also have something like an OWL monitor to show your instantaneous demand, then you can swiftly calculate whether you're generating more than you're using or vice versa.  If you're generating significantly more then that's the time to stick the washing machine on or do the vacuuming

[The Seldom Killer]

5. Inverters - mean time to first failure of inverters is around 10 years, so even if the PV panels are guaranteed for 20 years or more you would need to assume you'll be replacing the inverter at intervals. 

Just a comment on this. Some installers are finding it difficult to source inverters at the moment owing to high demand here and throughout the European market. As such they are having to get them from countries that are traditionally associated with the mass production of cheap electrical goods. Unfortunately these would seem to be of a lower quality with a shorter lifespan. Ask your installer about the source of their inverters and warrantable periods. On balance it may be worth waiting a little longer for a more reliable model to avoid hassle in the future.

It's a bit of a pity really because the UK actually has a fair amount of redundant capacity in the electrical manufacture industry and this is an area where it is probably easiest to reconfigure a production facility to meet a demand. Alas we just aren't cashing in on this.

[Quisling]

Inverters : Fronius or SMA are two best known/reputable makes. Much of the current shortage stems from increased demand in Germany ahead of FIT reductions. Suppliers reckon the shortages should be resolved by June or so. Interestingly most of the inverters use the same chips, which appears to be the supply critical item.

[The Mechanic]

I can understand the environmental argument for renewables but it seems to me that there are too many variables in the commercial argument.  A 13 year payback time (as quoted on here) is a long time and anything can happen in that period.  I also would be sceptical about the return on investment you would get if you sell the house before the payback time us up.  Not being an electrical engineer I am not on solid ground here but does 1.8kw mean that you will, at peak times in your consumption, be also drawing electricity from the grid.  A kettle, oven etc will all drw more than this unless you are going completely green and not using heat at all.

A system for heating hot water I can understand but PV, its a long shot IMHO.

[mrcharly-YHT]

No you are right.

However, it is possible to live with 1.8kW. When I moved from a boat with just a PV panel to a barge with a shoreline, the power system could only supply 1.6kW to the 240V AC circuit. We managed ok on that, running 3 computers, fridge, lighting.

[Quisling]

I can understand the environmental argument for renewables but it seems to me that there are too many variables in the commercial argument.  A 13 year payback time (as quoted on here) is a long time and anything can happen in that period.  I also would be sceptical about the return on investment you would get if you sell the house before the payback time us up.  Not being an electrical engineer I am not on solid ground here but does 1.8kw mean that you will, at peak times in your consumption, be also drawing electricity from the grid.  A kettle, oven etc will all drw more than this unless you are going completely green and not using heat at all.

A system for heating hot water I can understand but PV, its a long shot IMHO.

Indeed, a 10 - 15 year payback is a longtime for anyone but if you're planning on staying put the returns are much better than you get from leaving your cash in the bank at current rates.  Average occupancy for homeowners before they move is around 12 years I believe.  At present the estate agent/property surveying industry does not currently place much additional value on a property with microgeneration, though a good installation is a differentiator that would enable a little premium over an otherwise comparable property.  Of course "payback" is an interesting point.  Generally, you don't do payback calculations for other home improvements like double glazing (which is more of a comfort decision or undertaken for reasons of reducing decorating or improving security) or a replacement kitchen.  Indeed, double glazing would generally have a longer payback than PV under the FIT regime!

You're electrical assumption is right.  A PV array is sized as kWp - i.e. the kW peak output on a sunny day taking into account the siting factors (angle to the sun, latitude, shading factors etc).  Accordingly, for much of the time the output will be lower than the kWp rating for the array.  However, for well sited PV (i.e. negligible shading, pitched roof, reasonably southish facing) in much of England the output is likely to be around 800kWh per kWp per annum as a rule of thumb.  For a typical 3 bed semi something in the order of a 2kWp array is likely to generate up to about 50% of the annual electricity demand for the property, but of this generation the property will probably only use about half and spill the rest to the grid.  At other times the house will be importing electricity to cover the gap between instantaneous demand and instantaneous generation.

Until the Renewable Heat Incentive comes in next April, solar hot water actually looks less favourable unless you use a lot of hot water.  UK average water usage is in the order of 150 litres per person per day (in my household we've got that down to around 70, largely as a result of having 400 litres of water butts!), of which at least 50% is likely to be cold water for toilet flusing, washing machines, dishwashers, watering the garden, washing the car.  The residual usage of hot water can benefit from solar thermal.  However, from a carbon perspective an efficient gas boiler generates much lower emissions than usage of grid supplied electricity (see Part L of the building regs for emission factors, but typically 0.194kg/kWh for gas before taking boiler efficiency into consideration and 0.422 for grid supplied electricity).  Gas is also cheaper by a factor of say 3 - 4 times, so saving a bit of demand from your gas boiler is less beneficial both environmentally and financially that saving the same kWh off your power usage.  Obviously, the economics are better if your heat source is more costly/environmentally grim e.g. oil or solid fuel (coal etc).  In a household of 2 with lowish water consumption my A rated gas boiler is using around 6 kWh/day for water heating so if solar thermal meets half the annual needs I'd be saving around 1000kWh of gas at around 4p/kWh - i.e. £40 - £50 a year.  If you have 8 kids who all take deep baths and you have an old oil boiler then clearly the benefits are greater!

Q