Solar PV or Solar Thermal

leo738

Hello All,

I've had a look at other discussions on the same topic so apologies if this covers ground already discussed.

I'm looking at installing a solar system & was going to go the solar thermal (i.e. fluid route) but I see solar PV has become cheaper and although more expensive than thermal, is worth considering.

Some points that are particular to my case:

• New house (2 yrs old) so no grants available
• B2 energy rating
• Conventional gas boiler (i.e not combi) & well insulated cylinder (regular sized, 200lt)
• I installed a 40 tube solar thermal system on our previous house & was happy with it's performance. Very few issues but I'm aware of the requirement to renew the fluid every 2 yrs.
• I don't expect to make a profit from this system, simply save on energy bills.
• I'm aware return on investment will be approx 10yrs+
• I'm aware that feed in tariffs are gone
• Our house is regularly occupied during the day, 2 adults 1 child
• Thanks to the builder the surface area on the south facing aspect is limited & not far from optimum in shape (dimensions below)
• I expect to do the install myself but realise for a PV system I'll have to get a sign-off to connect to the grid. I'm not going to consider storage batteries.

If I went solar thermal it looks like I could fit a 40 tube system which looks, if I went Kingspan, for the kit would come in at around €3400.
If I went solar PV it looks like I could fit at least 8 LG285 panels (producing 2.28kW), which at first glance looks like it would cost approx €3500. If I went this route I'd probably install roof hooks so I could add panels later to the max possible.

Has anybody any thoughts on which way I should go?


Thanks,


Leo

quentingargan

LG is a very expensive panel to use - you could get other brands of 285W modules, still tier 1 at a lower price. But either way, 2.28KwP solar PV will provide a total of 2,000 Kwhrs approx of electricity - about the same KwHrs as the thermal. Using a diversion device such as this, you could ensure that all the surplus power is used to heat your water. So some of the 2,000KwHrs would be saving you 18c on your electricity bill, and the remainder would be saving you 9c on your oil or gas.

So the PV system would give you more savings, and no maintenance.

I think PV has fallen in price sufficiently that thermal is only merited where you need to save space, or on a large industrial system. For domestic, I think PV is always the better option.

rolion

Hi,

Let me share my story....

Can't give advice but you can avoid some of my mistakes maybe.
I was very pro the PVs panels until I got a special deal for the 40 tubes SolarTubes_HotWater system and doubled with a SEAI grant, it got the balance in favour of the ST_HW and not the PVs.

Spent 3 months doing my home work.
Installed 40 tubes solar hot water panels, working fine along the local weather.
I have the combi boiler supplementing the hot water in the 300L cylinder BUT, i repeat BUT it takes the water from a mere 20ish and spending a small amount of energy, bumps it to 55ish,as per thermostat.
Even better, in March I had few days getting 50 - 50 full cylinder (bottom and top sensors).
I will like to upgrade it to a 60 tubes but my lovely home ,build by some smart developers back in "one house cash a week good for them times" will not take a bigger cylinder than 300L, due to doors frames sizes.

I was looking at PV panels for the past 5 months.
Final decision: in local weather with small amount of sunny days, breaking in smaller segments of per hour per day, due to sun alternating with clouds, not worth the investment.
I will love getting lots of panels to compensate for the lack of sun and "harvest" the maximum amount of photons reaching my house perimeter but again, i don't have the luxury to build / install trackers with 20 panels that will do the job.
Also, the PVs will need sun(direct exposure to solar photons) all the time to generate energy while ST_HW once it gets the sun heat(it needs sun heat not photons) will work fine as part of the running the heating agent in the closed loop system, giving a constant (going down-ward with the water temperatures once I open the taps, but the transfer from 55 degrees of hot water to a 35 degrees of hot water needed for a shower will not empty the cylinder. Then, once and if the sun comes again, it replenished with hotter water, back to 50ish.
The electrical PVs, if I have sun photons I have energy, i have electricity ... if cloudy or sun hides away, input current in Amps goes down the cable and no energy / no electricity generating at all. Nothing, I may have 30V but 250mAmps / 0,3A.

So, if I had big garden, full South oriented and unshaded with lots of space to anchor a solar tracker with minimum 10 panels (to give me an input Voltage of 10 panels x 30V = 300V ) to make my DC-AC inverter happy, yes will have had taken in consideration PVs.

rolion

leo738 wrote: »

If I went solar thermal it looks like I could fit a 40 tube system which looks, if I went Kingspan, for the kit would come in at around €3400.
If I went solar PV it looks like I could fit at least 8 LG285 panels (producing 2.28kW), which at first glance looks like it would cost approx €3500. If I went this route I'd probably install roof hooks so I could add panels later to the max possible.

For the solar tubes, why don't you go local, i went with Joules, local supplier /showroom in Dublin. I called in their office, met the tech guy, who explained the system in plain English. Final price is based on the charge of the installation, distance from tubes to cylinder, pipe work and so on.

PVs panels, i decided as well with LG300 Neo2,sourced off the continent, very good prices. There is a local supplier that can help you with installation and advice, if you like to do it.
Ignore the technical details of the PV panel. You need to asses the conditions of the site, your home in relation to south orientation or east-west, angle of the roof and if any shades present during the sun movement in the sky,8am to 8pm.If you go with static installation, very important near / adjacent roofs or trees.

My main problem is that the DC-AC inverter needs at least 90-120V to start-up running. That means at least 4 panels connected in series to give you the 4p x 30V - 120V.Is recommended to have panels running at around same voltage as the main AC voltage, ie 8 panels x 30V = 240V.
If you install the panels on the roof and the chimney in the morning AND/OR the near house roof shades or blocks O N E single panel connected in series, A L L the panels will be made practical non-functional.
You can mitigate the problem with a dual input MPPT but how will that work on your home roof dunno know yet.

Also, during day time when maximum input photons -=- maximum output energy process, you will need to use it otherwise is a waste. Charging batteries becomes a more expensive way than using it from the main ESB grid. If the FIT program is re-enabled, yes I may decide to reconsider the PV project. But, spending about €7,000 on a dual tracker 9 + 8 panels and a 6Kw inverter to have a return of ... in .. years may not be only about the figures !??

Until then, please share with us your experience !
Regards

rolion

Not lastly...
I keep an eye from time to time on these website links here, below.
It tells me how other people systems performing in Ireland, with the system setup, performance, parameters and a nice graphics / historical results.

Navan

Waterford

Bantry

Salthill

Coomanore

Water John

So rolion, those companies putting plans in place to build solar farms across the South of Ireland are deluding us and themselves?

rolion

Water John wrote: »

So rolion, those companies putting plans in place to build solar farms across the South of Ireland are deluding us and themselves?

Hi John,

I am sharing my personal experience.

Please be assured that I cried when I had to cancel my tracker's solar panel project, after spending time and money with structural engineer designing the support infrastructure, many emails to people involved in the industry.
In the end, is not working for me because the location, position, size, neighbourhood will not make it worth it, from any point of views.
I repost, is absolutely my particular case.

Please see below the two production of the PVs today.
My house will not survive on those spikes, caused by sun outage and/or clouds.






In relation to South of Ireland ,I'm delighted to hear that the projects have got the planning permission and began building them, as opposite the windfarms when one single person denied the whole project.

I don't have access to their business plan to see if they are viable, do you !??

Probable that their professionally designed and planned installation systems will have an output near ideal, like the one below:




Regards

Water John

The solar thermal for the south west is about the same as southern Germany.
I see on eco eye, one guy has €10M investment pot which he was using to put PV on farm buildings he would rent. Then all electricity connections in Germany are three phase.
It will all depend on the price, here.
Not many gone through planning yet but many in the pipeline.
Sadly, from what I hear, their are objectors in the pipeline too. Don't know what the complaint this time.
I live near turbines, don't know what's the issue.

None will be tracking. Each generally about 5Mw, 10 Hectares.

quentingargan

Water John wrote: »

Sadly, from what I hear, their are objectors in the pipeline too. Don't know what the complaint this time.

I think the objections here are partially valid. We have had no supports for rooftop solar on either industrial or residential, and now there are moves to support field scale solar. It is cheaper to put solar on the roofs of industrial buildings, and there is already a grid infrastructure in place. We haven't tested the water yet to see how this might roll out in Ireland and yet we already have sites with planning permission for large solar parks. Arguably this is a waste, often of good agricultural land.

In the UK, solar parks quickly mopped up grid capacity for solar, and in many areas, residential and industrial users cannot get grid access because the local grid's capacity to take solar has already been mopped up by solar parks.

I'm not an objector as such, and i think solar parks have their place, but I don't think we should launch into field scale solar without first having a debate about the scale that is appropriate in Ireland and what percentage of the mix should come from this source.

leo738

Thanks everyone for your inputs.

Our house is south facing & the roof is unobstructed. The useable south facing surface area of the roof is limited, enough to take 40 tubes & at least 8 pv panels but it would be nice to get up to what i think is the max per residence of 6kw if I do go down the pv route.

I assume some spreadsheets/ websites have been developed to calculate savings & costs of such systems. Anyone have any pointers?

quentingargan

Attached is a simulation of what you would expect to get from ten 260W panels in Dublin on south facing roof at 35 degree pitch. A similar simulation can be done for other options.

The savings made would depend on the feed in tariff / how much you use / whether you dump the surplus to hot water to cut your gas bill etc. But this is a good estimate of the energy production to be expected each month.

rolion

quentingargan wrote: »

Attached is a simulation of what you would expect to get from ten 260W panels in Dublin on south facing roof at 35 degree pitch. A similar simulation can be done for other options.

The savings made would depend on the feed in tariff / how much you use / whether you dump the surplus to hot water to cut your gas bill etc. But this is a good estimate of the energy production to be expected each month.

Thanks Quentin,
Based on my practical tests over past month, with panels left over on the ground, in my back garden:
* a panel placed at the correct fixed angle (p-down / vertically) towards the Sun gives me about 5.5Amps -=> 30V x 5.5A = 160W
* same panel ,in the same position vertically BUT moved so that it directly faces the Sun (tracking East-West / left-right ) gives me 8.5Amps -=> 30V x 8.5A = 250W

Therefore, if I will have PV panels installed, it will have to be on a hand manually moved / setup vertical (up - down) according to every month Sun move / angle around Earth AND moved/tracked by an electronic device facing the Sun(East -West / left-right) .

rolion

leo738 wrote: »

Thanks everyone for your inputs.

Our house is south facing & the roof is unobstructed. The useable south facing surface area of the roof is limited, enough to take 40 tubes & at least 8 pv panels but it would be nice to get up to what i think is the max per residence of 6kw if I do go down the pv route.

I assume some spreadsheets/ websites have been developed to calculate savings & costs of such systems. Anyone have any pointers?

Hi Leo,

Do you want to approach / attack this project as DIY or assisted / designed by a third party specialist ?
I can help you on the DIY side but professional advice may need to be sought if you want or can afford it.

Enjoy it.

rolion

rolion wrote: »

Based on my practical tests over past month, with panels left over on the ground, in my back garden:
* a panel placed at the correct fixed angle (p-down / vertically) towards the Sun gives me about 5.5Amps -=> 30V x 5.5A = 160W
* same panel ,in the same position vertically BUT moved so that it directly faces the Sun (tracking East-West / left-right ) gives me 8.5Amps -=> 30V x 8.5A = 250W

Really?
30V for both orientations? That's very odd for a loaded current source.

leo738

rolion wrote: »

Hi Leo,

Do you want to approach / attack this project as DIY or assisted / designed by a third party specialist ?
I can help you on the DIY side but professional advice may need to be sought if you want or can afford it.

Enjoy it.

This would be a DIY project with a helpful benefit of cutting energy costs.




Quite a significant difference. Is there any roof mounted system that would allow some degree of sun tracking to increase efficiency above a fixed system?

I understand it's against forum rules to post suppliers but if anyone could point me to companies willing to supply kits only I'd appreciate a private message. I've had a look online & can't see many companies doing supply only.

Also anyone recommend someone willing to sign off a DIY install so that it can be connected to the grid?

Regards,

Leo

Calahonda52

Leo,
u need to do the math, (leaving cert integration), for the different areas under the curve across the full year so as u can evaluate the cost benefit of the additional cost of the tracking system.
My guess is that for a small PV array the numbers just wont stack.

Water John

I would not know the yield differential but tracking is not done on any commercial projects as it would not be cost effective, TMK.

There's even simpler maths.
Structural integrity of your average roof versus foundations required for trackers.
Trackers require accessibilty and maintenance

leo738

Looks like roughly one third more available via tracked panels which is significant. However looks like it's a no go.

Still looking for suppliers. .

noel100

leo738 wrote: »

Looks like roughly one third more available via tracked panels which is significant. However looks like it's a no go.

Still looking for suppliers. .

Try segen in the UK good prices for kits.
I haven't bought.anything have set up a trade account.

Water John

In the domestic sense, tracking should not be that difficult for a whizz kid to rack up. Little solar motor etc. Stability, with wind might be the biggest issue.

leo738

leo738 wrote: »

Looks like roughly one third more available via tracked panels which is significant.

More like 20%.
The trackers use power.

Water John wrote: »

In the domestic sense, tracking should not be that difficult for a whizz kid to rack up. Little solar motor etc.

There is no such thing as a solar motor. Using a motor direct from the panel output will inevitably torque stall and fry the windings. A linear actuator from the mains or a battery with low voltage disconnect would be the way to do it... ...from the ground.

rolion

leo738 wrote: »

Looks like roughly one third more available via tracked panels which is significant. However looks like it's a no go.

Still looking for suppliers. .

Where are you based,where is the system been built ?
Pleasee feel free toPM and i can share few tricks.

Water John

Sir, are there not solar pumps attached to tube panels? Have their own little PV.
You would not link the motor to the overall panels just has its own small one.

But whole thing not worth it.

Does it have a battery?
Perhaps the point is semantic. A motor needs controlled input eg, voltage, current, frequency etc. So yes you can have a motor for a solar application but it is just a rudimentary motor. Afaik there is no motor that is designed to react to the wild power a PV module will supply without either protection circuitry or incurring damage.
Most motors rely on operation to drive their fans if you power them while stalled they tend to go to motor heaven.

Water John

Solar motors are used on the solar thermal. Its safer than relying on grid power.
Solar also used to power water pumps in many farm situations.

Again, it is not worth doing this for PV.

Most of these are universal motors, BLDC motors or sterling engines.

leo738

Thanks all for the input but if there is not a proven robust roof mounted system I won't be trying something experimental! I don't need the headache!

I'm based in Dublin

Jivin Turkey

I'm trying to get my head around whether from a pure economic point of view a residential solar installation stacks up. I'm looking at it for a 160 SqM residential property built in the late 1970s but undergoing a substantial renovation.

I've been looking at this guide (from 2010 admittedly)
http://www.seai.ie/Publications/Renewables_Publications_/Solar_Power/Best_Practice_Guide_for_PV.pdf

to calculate the per unit cost of the energy over a 20 year period.

I've seen quentingargan put out this performance analysis:
https://us.v-cdn.net/6034073/uploads/attachments/203800/381779.pdf

so perhaps I need to improve the Wp output but in any case, I'm coming out at a lifetime cost per unit 20 - 22c depending on the assumptions.

To me this doesn't see like a good investment on pure economic grounds given current electricity pricing is around 13 - 17c?

Am I missing something?

rolion

Hi,

Sometime you have to go based on the costraints of the physical location,house,neighbours,coverage.
Not lastly,the budget available.

I took all the elements in consideration when i planned mine and the main idea was to get maximum return on the coverage/location/exposure of my current house,the single element that is static in this dynamic game.
As with a normal house,we have only the roof availabe to play ,to be covered by panels (pv or tubes) and mostly the exposure 24/7/365 to God Sun !
Then, i looked at the availale budget and did it.

If i have to stay up and do maths on RoI and TCO...honestly,not worth it in at least 10 years.

Regards

Jivin Turkey

But even if I assume that coverage, tilt, orientation are the most favourable, and apply zero downtime for the installation or even forget about power heating a water tank to a level that I don't actually need on many days, the per unit cost is almost double the current market rate - and it's paid upfront for twenty years!?

My grid tie is shaded for half the day. Self installed it, no subsidy, second hand grid compliant equipment, self-consumption system. 4 year payback, I didn''t do it for the dosh though.

ferryman35

It's generally accepted that the payback on solar (at least thermal) is a 20 yr play - therefore if (and of course you should!) you are considering the payback, you need a system that makes best use of the available sun (i.e efficiency) and also that lasts long enough to give you a return.

Solar thermal is evaluated against town gas at say around 5c / kwh at the moment