photovoltaic panels. How to choose

[merv]

I'm seriously thinking about installing a 4KW system. How are the efficiencies of the different panels measured ? What units should I be looking at when talking to the salesperson ? Any pertinent questions to pose ?

Any help appreciated

Merv

[xone]

Does 4KW satisfy your needs for power consumption? Whats your budget?

http://www.futureenergysystems.org.uk/s ... voltaic-pv

[merv]

We are currently consuming 8-10 kWh per day. Solar water heating and wood fired central heating already installed.

Cannot get planning permission for more than 4kWhp.

So, to get the most bang for my buck I want information on how to compare the different offers the different salespeople are trying to sell me.

Then I can decide what sort of budget to apply to the project.

Unshaded exposure to south east. 35° slope tile roof.

Would you like to help ?

Merv

[xone]

Of course I'm happy to help. 4 kw is quite a substantial system, have you got suffiecent roof space? you're going to need about 37 panels and thats assuming you want it on the roof? Do you want a grid tied system of have it off grid? Are you sure you need a whole 4 kw? This isn't a problem really because next year the rules change about how, if you're grid tied, you're paid back buy your energy company, currently we're using the "roc" system and the best you get paid back per unit is 18p, southern electric, but when the new "feed in tarrifs" come in you can get upto and above 40p a unit depending on who you're with, this basicly slashes payback periods in half or into thirds. To give you an idea on cost, and this is really the decider, just for the panels for a 4kw system you're looking to pay £15'140. On top of this you'll need to consider installation as well as grid tie inverter or batteries, dump loads, roc meter etc etc. Really, you should decide a budget, if there is one and go from there. If you like you can PM me some contact details and I'd happily talk it through with you.


Going by your 8 - 10 kwh a day is that current of based on a calculation of a years reading? Bear in mind that will change with seasons etc. Figure out how much you're likley to use over a year, you may not need such a big system.

[Greenbeast]

can you not reduce consumption first?
We're down to rough 6kWh per day now and that's with electric cooking

and despite what xone says, electricity use isn't as seasonal as gas usage.
We used, on average 2kWh extra per day during the last winter than we do now, but i've also taken further energy saving measures since then too, which skews the results

[merv]

We probably could reduce consumption a bit more. Only "seasonality" for us would be on extra lighting.

However, we are determined to put in a pv system. What I want to know is how to choose the best/most economic.

And how to get the salesperson to give me the relevant information for an informed choice.

Merv

[contadino]

I have a book called Solar Electricity by Simon Roberts (ISBN 0-13-825068-5) which explains what I think you're after. It's more geared towards installing it all yourself, but there's quite a lot of stuff about mono vs polycrystaline panels, optimum pitch, system expandability, etc.. The problem is mine's a bit out of date and I don't know whether it's been reissued to include recent new product developments. Either way it may well be a good starting point.

[Clara]

Perhaps the most important consideration for reducing consumption is to find alternatives to any electrical appliances that produce heat (a cooker would be the worst offender, because they use lots of power and they are used for long periods).

[xone]

What I want to know is how to choose the best/most economic.

The best is dertimined by the latest product on the market but this is then restricted by cost as it'll be the most expensive. Solar PV is increasing efficiency every year so, like computers, your system will soon be over taken by a better more efficient product.

When you talk about "economic" are you reffering to cost to yourself or the efficiency of the panel?

[dave45]

>Solar PV is increasing efficiency every year so, like computers

emmm - not sure this is true.

computer processor chips have been increasing in power consumption (not efficiency) until recently

back in the days of the 386 processor, my entire system box (motherboard soundcard disks etc) consumed 38watts.
Years later, my Athlon XP processor ALONE took around 70 watts, and a more modern Athlon 64 processor can consume 125watts - thats why modern machines have such powerful fans.

But I guess it depends how you measure "efficiency" :-)

AIUI the basic technologies for solar panels (amorphous, polycrystalline, monocrystalline etc) have slightly improved their efficiencies (in converting sunlight to electricity per unit area) over the years by a small %, but new technologies in the labs promise much better efficiencies, but at unknown or huge cost and no certainty when or if they will see the light in commercial quantities. http://en.wikipedia.org/wiki/File:PVeff(rev110707)d.png

none of which really helps decide what to go for, sorry.

from personal experience the cheaper amorphous PV panels were disappointing in both efficiency and reliability.

[contadino]

The best is dertimined by the latest product on the market but this is then restricted by cost as it'll be the most expensive. Solar PV is increasing efficiency every year so, like computers, your system will soon be over taken by a better more efficient product.

AFAIK, the efficiency gains over the last 10 or so years are more aimed at making the manufacturing process simpler/cheaper. That's not to say that retail prices have changed - in fact they've risen - all the efficiency benefits have been swallowed up by manufacturers.

There are frequently press releases to say that such-n-such new technology will produce significantly better performing panels, but they rarely reach the market.

[xone]

>Solar PV is increasing efficiency every year so, like computers

emmm - not sure this is true.

.

I know they aren't on par, it was to give a sense of an idea.

Every year or so the technology gets better, as I'm sure you're aware there are a lot of companies producing solar PV and as with everything manufactured things get better and this has been proved not only in the computer industry but successfully in the solar photovoltaic industry as well.

I tried your link but it doesn't work.

[dave45]

if you copy the whole link by hand it works

http://en.wikipedia.org/wiki/File:PVeff(rev110707)d.png

the auto-link creation thingy on here must get confused by the RH bracket I guess

[AllanMiguel]

I'm seriously thinking about installing a 4KW system. How are the efficiencies of the different panels measured ? What units should I be looking at when talking to the salesperson ? Any pertinent questions to pose ?

Any help appreciated

Merv

The solar panels rigidly on the south-facing sections of our house roof. We have 40x100-watt modules (of 36 cells each) attached to a sturdy frame about 8-inches above, and parallel to, the roof. Each panel is nominal 17V open-circuit, and we have paired them up to give us a "24V" system. We have divided the total array into 4 sections, each having 4-6 24V module pairs, depending on the size of that section of the roof.

[sdm1965]

Looking for an installer of Solar PV for your home can be a tricky business especially with the introduction of the Feed in Tariff. With so many new start up companies jumping on the bandwagon you need to be aware that you are choosing the right installer. Main things to look for are that they are MCS Accredited for Installation and that the panels they install are MCS Approved. Also ensure they are members of the REAL Code of Conduct. Beware the high pressure sales techniques employed by some companies and if they start offering you discount steer clear. If they are REAL Members then they shouldnt be doing this. I have heard one story of a company offering 5 different prices to try and get them to signup on the night. If you need putting in touch with reputable, trusted quality installers with a pedigree in renewable energy then we hope to be of assistance. You can visit our regional advisory website or join in our forums at: