Solar PV Panels

Cardew

Rosemary_Jane wrote: »

On several days I've noticed power production has been 3.81kW, which is probably the maximum, but production begins quite early in the morning, often over a kW by 7am, and goes on late, til around 9pm, which may offset the disadvantage of not making 3.96kW at noon.

Just a point of clarification.

The 3.96kWp rating of your panels is no indication of what output power(kW) it should achieve.

A PV panel of say 225wp will give an output of 225 watts under specific laboratory conditions of sunlight, temperature etc

So a 3.96p system might only produce a maximum output of 3kW in, say, Scotland, but in excess of 5kW in, say Spain.

Certainly the best way to treat the PV investment is as an annuity.

However which is best( annuity or PV system) depends on your age and life expectancy and other factors.

If you are in your 30's;) then the annuity would be better IMO!!

In all seriousness, assuming you are close to retirement age, then the PV is going to be the better bet.

Rosemary_Jane

Cardew wrote: »

... Certainly the best way to treat the PV investment is as an annuity.

However which is best( annuity or PV system) depends on your age and life expectancy and other factors.

If you are in your 30's;) then the annuity would be better IMO!!

In all seriousness, assuming you are close to retirement age, then the PV is going to be the better bet.

I'm 55. An index linked annuity for £14.1K would start at £30 a month for me!

R

PS thanks for the clarification! I'll keep watching for a higher spot reading!

zeupater

AidyB wrote: »

Long time out of date, but just worth noting that a lower start-up voltage on an inverter does not mean that the inverter starts earlier in the morning. Actually early morning or late at night the panel voltage is higher as panel voltage is lower with high temperature. It is the current that increases with irradiance

It is sharp sales tactics, nothing more or less.

Sorry

Hi AidyB

Welcome to the forum

Agree, sharp sales tactics, and a few extra minutes would make very little difference at either end of the day when considering the power generated is so low, however, as I understand it the inverter monitors the open circuit voltage and only applies a load when the Voc has been stable for a predetermined time, so without applying a load there is no current to monitor or increase.

As I understand it, there are a number of inverters which can be reconfigured to reduce the startup voltage, however, setting it too low could easily lead to the inverter frequently cycling between on & off in low light conditions due to voltage dropping when the load is applied and therefore causing unnecessary/excessive wear to the inverter switches .... this is obviously why these units have a supplied startup voltage which is higher than what is possible, I suppose that the only time that the standard setting should be changed is when the panels are low voltage/high current.

Z

furndire

RosemaryJane I'm using mine as annuity. System cost us £15,600 - just had first complete year £1608 in FiT - payments. Not a clue how much electric saved (meter problem), but I am sure that combining being more savvy with how we are using it, I think we have cut back quite a bit - mainly because we are more careful how & when we use it.

jimjames

AidyB wrote: »

Long time out of date, but just worth noting that a lower start-up voltage on an inverter does not mean that the inverter starts earlier in the morning. Actually early morning or late at night the panel voltage is higher as panel voltage is lower with high temperature. It is the current that increases with irradiance

It is sharp sales tactics, nothing more or less.

Sorry

PV Solar UK seem to be unique in pushing the lower voltage as an advantage of their inverter over everyone else's. Seemed very odd to me that SMA were the market leader but didnt perform as well as PV Solar's claimed system! They were also unique in claiming that they had dispensation to not use the standard SAP calculations but could use their own numbers that strangely enough gave a much faster payback!

Out of all the suppliers we had round to quote PV Solar UK were the only one that did the hard sell. It was actually quite comical with their salesman tapping away on a calculator for 5 mins pretending to get a figure out when he had a laptop sitting next to him! Every other company went away and sent their quote later by post or email.

The other aspect that put me off was their use of a compound 15% annual electricity price rise for 25 years. They seemed to miss that by their calculations electricity would account for 75% of take home pay at the end of 25 years as a result of the massive difference between RPI and their compounded figures.

rarevisitor

Any one got more recent experience of this company - the rush to get installed by 12th has lured me into getting quotes and they seem eager. Would be very grateful for any feedback

larkim

I think you might want to name the company so people can comment! Newbies can't post website addresses etc, so that may have caught you out.

HTH!

Matt

ProfGreen

Hello, can I join this thread with a newbie question.. Having fitted a 4 kW system in south London, on a South-facing roof with little/no shading, about 30-35 degree angle.. What should I expect to produce on a sunny and clear December day, with all panels in direct sunlight... Looking for peak output as well as expected daily production. And how would the production develop over the year (say March vs June vs Sept)? Greatful for any actual experience to shed light on what is reasonable. Thanks!

zeupater

ProfGreen wrote: »

Hello, can I join this thread with a newbie question.. Having fitted a 4 kW system in south London, on a South-facing roof with little/no shading, about 30-35 degree angle.. What should I expect to produce on a sunny and clear December day, with all panels in direct sunlight... Looking for peak output as well as expected daily production. And how would the production develop over the year (say March vs June vs Sept)? Greatful for any actual experience to shed light on what is reasonable. Thanks!

Hi Profgreen

Welcome to the forum ...

Peak output would depend on how clear the atmosphere is. This is much more important in the winter due to the shallow sun angles extending the lightpath through the atmosphere and therefore scattering the available radiation. A clear and frosty day with a really good sky will probably give somewhere over 70% of the peak rating of the system but recent sunlight around here has only achieved around 50% of the peak rating of our system.

I've seen data from a few systems around London which have recently been generating around 2.25kWh/kWp, so a 4kWp unshaded system could be producing around 9kWh/day ... we've really been suffering from cloud when the SE has been clear, but yesterday still managed over 5kWh, the best day for a while.

Remember, the above only addresses peak and in no way would by typical. To get an idea of what you would expect to produce by month have a look at the PVGIS system here .... http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php .... to use it in it's basic form simply feed in your location, orientation, roof angle, system size and select the 'Climate-SAF PVGIS' radiation database and the system will generate some target figures for you ....

HTH
Z

ProfGreen

Many thanks zeupater, that's a good help and confirmed what I thought.

Since install we have had some very bright and clear days, with the system in full sun (about 32 degree angle, 20 azimut (i.e. SSW)). Yet the system will only peak at 700W (ave 400 W for a little while on a sunny day) and I might get 1.5 kWh in a full December day...the best has been 2.3 kWh. On a cloudy day I'm getting Zero. This is obviously pitiful and I have compared to others who are getting up to 3kW peak and about 10.9 kWh in end November.. My peak is less than 20% of capacity on a bright sunny day, so something is not right at all.
The system is 17x Schott poly 235 with a SB inverter. Inverter sits in the loft with some 15m of DC good quality cabling.. So I am trying to figure out what to expect in order to get the installer to ID the problems.. Compare to your useful link estimator, which suggest I should get 4.14 kWh on average and 128 kWh in December.. (4.14kWh on average would suggest at least 7-8 kWh on a bright day, since weather will drag the average down of course).

Any more real experience to compare with would be most welcome.

Thanks.
LPG