Photovoltaic panels

Curious Geroge

Looking for the Pro's and Con's of installing Photovoltaic panels on a new build. We have an Air to Water HP going in and I was considering these to run it.

Are these expensive ? Do they need to be on a South facing roof ? What changes or retrofitting would be needed to a standard electric installation ?

Cheers

quentingargan

If you put them in while building it isn't too expensive. You should be able to buy all the hardware (very ballpark) for €1000 per Kw plus €500, so a complete 2kw system including mountings and inverter would be about €2.5k plus VAT. Installation is about 1 work-day for roofers and 4 hours for spark.

But usually they are used in new builds as a way of ticking the boxes on Part L - either renewable energy requirements, or in some cases to lower CPC/EPC. Photovoltaic systems work best in the summer when you won't really be using your heat pump much.

If you put in a PV system, you normally export your power to ESB getting paid (a rather miserly) 9c per KwHr for exports. If you have MHRV and other loads yourself, you displace them with your own electricity saving 19c per KwHr. That is much more cost effective.

I would do it if you want them / like the idea of having them, or if there is a lot of daytime electricity use. Or I would use them as a cost effective way of meeting Part L on any new build unless you want a heat pump for other reasons.

But i would probably not buy PVs to run your heat pump per se. Better to sell your electricity in the summertime at 9c and run your heat pump at night on off-peak power for about 7.5c

Curious Geroge

quentingargan wrote: »

If you put them in while building it isn't too expensive. You should be able to buy all the hardware (very ballpark) for €1000 per Kw plus €500, so a complete 2kw system including mountings and inverter would be about €2.5k plus VAT. Installation is about 1 work-day for roofers and 4 hours for spark.

But usually they are used in new builds as a way of ticking the boxes on Part L - either renewable energy requirements, or in some cases to lower CPC/EPC. Photovoltaic systems work best in the summer when you won't really be using your heat pump much.

If you put in a PV system, you normally export your power to ESB getting paid (a rather miserly) 9c per KwHr for exports. If you have MHRV and other loads yourself, you displace them with your own electricity saving 19c per KwHr. That is much more cost effective.

I would do it if you want them / like the idea of having them, or if there is a lot of daytime electricity use. Or I would use them as a cost effective way of meeting Part L on any new build unless you want a heat pump for other reasons.

But i would probably not buy PVs to run your heat pump per se. Better to sell your electricity in the summertime at 9c and run your heat pump at night on off-peak power for about 7.5c

Thanks.. 2.5k would be very reasonable but I'm getting 8/9k min which had a lifetime payback. Plus the invertor has a 10 year lifespan which is 2k ever 10years plus a service? Hard to get a good knowledge base on experience though.

quentingargan

Curious Geroge wrote: »

Thanks.. 2.5k would be very reasonable but I'm getting 8/9k min which had a lifetime payback. Plus the invertor has a 10 year lifespan which is 2k ever 10years plus a service? Hard to get a good knowledge base on experience though.

Yes - a price of €5 per watt was the going rate a few years ago, but prices have plummeted as solar parks have spawned mass production. Unlike wind, the economics of large scale solar do trickle down to domestic installations because the panels are the same whether it is three you a garage roof or a hundred thousand of them in a solar park. Inverters are also now mass produced. They are the only part which may fail during the lifetime of the system, but you should be able to get a 2kw one for between €400 an €800 plus VAT, depending on brand.

Curious Geroge

Got some prices sorted. the price I got for a complete 2kw system including mountings and inverter is €5.5k plus VAT. This would generate a max of 1800kw per year.

Using the national avg cost per unit at the moment of 16.36 cent, this would be an annual saving of €295. -- and thats assuming that I get and use the kw produced.

thanks quentingargan, you are correct; about €800 + VAT every 10 years for the invertor.

So, it would workk out at an annual saving of max €200 (295-(800/10)) for a min layout of 5.5K + VAT.

For PartL requirements, it probably helps but in terms of payback it seems to be 25 years.

That said, I might add a couple of cables to have them in place should I ever wish to do this down the line.

quentingargan

Curious Geroge wrote: »

Got some prices sorted. the price I got for a complete 2kw system including mountings and inverter is €5.5k plus VAT. This would generate a max of 1800kw per year.

Using the national avg cost per unit at the moment of 16.36 cent, this would be an annual saving of €295. -- and thats assuming that I get and use the kw produced.

thanks quentingargan, you are correct; about €800 + VAT every 10 years for the invertor.

So, it would workk out at an annual saving of max €200 (295-(800/10)) for a min layout of 5.5K + VAT.

For PartL requirements, it probably helps but in terms of payback it seems to be 25 years.

That said, I might add a couple of cables to have them in place should I ever wish to do this down the line.

That is about right, though I think the prices you are being quoted for a 2kw system are very high. The hardware cost can be as low as €2500 to €3500 for panels, frames and inverter, so someone is charging €2.5k to €3k to install it. That's doubling your payback time. But on the other side of the equation, I think you are optimistic in assuming you will use all of the power produced. In practice you may use about 1/3rd, so most of your income is at 9c rather than 16.5c.

Curious Geroge

quentingargan wrote: »

That is about right, though I think the prices you are being quoted for a 2kw system are very high. The hardware cost can be as low as €2500 to €3500 for panels, frames and inverter, so someone is charging €2.5k to €3k to install it. That's doubling your payback time. But on the other side of the equation, I think you are optimistic in assuming you will use all of the power produced. In practice you may use about 1/3rd, so most of your income is at 9c rather than 16.5c.

I'd agree but for the nay sayer that may respond it was useful to realise that even with 100% usage the payback is hard to achieve.

With 1/3 usage and 2/3 selling to the grid, its €198 per annum. or an annual saving of max €100 (198-(800/10)) for a min layout of 5.5K + VAT.

I think this is a PartL get out..

quentingargan

Curious Geroge wrote: »

I think this is a PartL get out..

Yep. That's my experience. Almost all PV installations I see are to tick the boxes of Part L on a new build, and it is by far the cheapest way to do that.

What a shame that the market for PV here is based on a stick and not a carrot. All of the emphasis on renewable energy in Ireland is wind. That is going to cause problems down the line with a lack of demand at night. A more balanced approach of wind and solar would be better, and arguably not a lot more expensive.

The worst aspect of this is that industrial consumers, which really could use PV for most of their consumption, are excluded from the 9c feed in tariff. So if they export, they get de nada. It wouldn't take much to give them the tariff and see warehouse roofs covered with PV.

Big Dec

Hi all,

Just jumping on this a bit late.

I was thinking of putting in the cabling to possibly add panels on the roof of my garage in the future if/when prices are more reasonable for both installation and feed in.

Any suggestions on what cables I should put in?
Just want to run something to the fuseboard in the utility room.

Cheers,
Dec.

quentingargan

Big Dec wrote: »

Hi all,

Just jumping on this a bit late.

I was thinking of putting in the cabling to possibly add panels on the roof of my garage in the future if/when prices are more reasonable for both installation and feed in.

Any suggestions on what cables I should put in?
Just want to run something to the fuseboard in the utility room.

Cheers,
Dec.

Depends on distance from garage to house, and what size system you propose (the max normally permitted on single phase is 6kw or 25A, but you may be thinking a lot less). I presume you are thinking of bringing the grid from the consumer unit to another consumer unit in the shed? If you are locating the inverter in the shed you should use a wire size calculator to work out what your voltage increase will be. Technically, when I did my solar PV training, the permitted standards was voltage drop of <1%.

The inverter will cut out if the grid voltage it senses is overr 253V. So if you had a 3% drop at full load,it would cut out when voltage at the fuseboard is 245V. It is at the other end that you are technically breaking regulations. The inverter should cut out if the grid goes below 207V. If you have a 3% voltage drop, it could theoretically continue to push power into the grid with the grid as low as 200V.

freddyuk

Lay a length of conduit with pull through? Worry about cable later.

murphaph

Yeah, make provision for it. I personally believe the battery tech will collapse in price like the panels themselves over the next decade and it will really be worth getting in. We're doing a new build here in Germany (FIT is also just 9c for installations done this year and our buy in price is much higher, around 27c, than Ireland...energy is expensive in Germany, gas is similarly expensive!).

We intend installing a fairly large system now, even if we have to export a lot in the early years. We intend adding batteries later, when they are a bit cheaper. Until then we'll attempt to maximise usage by using a heat pump for heating and DHW and running big loads (dishwasher, washing machine etc.) on a timer at noon, when we are at work.

The way I see it, the panels are cheap enough now to just lash as many up as possible and then I won't have to go climbing up there to add more when I add the battery tech later. Could be the wrong call if battery tech doesn't reduce in price as I expect, but there's massive research going on in batteries these days.

Edit: summers can be quite hot here, so we also intend using the PV to drive the heat pump in reverse to provide at least some passive cooling, if not full AC (running the compressor). This is also a way to extract more value out of the capital cost of the heat pump IMO.

Arklow10

I recently had a PV system installed, 3.3kw, any surplus electricity generated that is not used immediately heats up the hot water tank.Over this usage the electricity is wasted
I was wondering though if you could run a heater that would just use this excess PV generated energy or does such a system exist. Possibly the controls would be very expensive?

Any thoughts?

quentingargan

Arklow10 wrote: »

I recently had a PV system installed, 3.3kw, any surplus electricity generated that is not used immediately heats up the hot water tank.Over this usage the electricity is wasted
I was wondering though if you could run a heater that would just use this excess PV generated energy or does such a system exist. Possibly the controls would be very expensive?

Any thoughts?

Some diversion units have a connection for a second heater. However, on that kind of sunny day, do you really want more heat in your house? Can you arrange that the washing machine / dishwasher do their work during sunlight hours?

Arklow10

I do stagger washing machine and dishwasher usage say 1.5 hours each. Also some perpetual loads e.g. fridge, freezer are in place,
Then any unused electricity heats up the hot water- however occasionally each day there will be periods, in all seasons, where there will be some electrical energy wasted
I was wondering if instead of this just going back into the national grid , could this completely surplus electricity say in winter time put some energy into say a small storage heater?

quentingargan

Sure - you can do that OK. There are a few brands of device that have more than one output.

If yours doesn't, a smart spark could wire a thermostat on your boiler to a two pole relay that switches the surplus power to a second heater. You would need a way of disabling this when using the boost function though.

Arklow10

Ok thanks will check this option out. Appreciate the info

a148pro

Surely you're not producing excess in Winter though?

quentingargan

a148pro wrote: »

Surely you're not producing excess in Winter though?

You can get good days in the winter. For a 3.3kw system south facing in Dublin, this is a table of MAX values each hour. 'twould be rare to get max values all day, but with a storage heater releasing its heat at night after a bright winters day, it might make sense.

Arklow10

The system is installed only a couple of weeks now but there definitely are times every day when the house will not be consuming all the power created at various times, only talking about very little though overall.

I do like that hourly max schedule though

unkel

If you have a well insulated 300l or bigger hot water cylinder, none of your production will go to waste. It's an inefficient use of electricity, but it's not wasted! Provided you use quite a bit of hot water that is. Family of 4-5?