Solar PV support an Air Source Heat Pump?

[ashthekid]

I’m looking at locating an air source heat pump at the bottom of my garden with a single Solar PV panel situated next to it with possibly a simple battery storage unit next to it. Would that single PV generate enough electricity to power the heat pump independently and then if required take additional electricity from the grid to top up if necessary?

[PeterW]

Nope. Max output on a panel is 300W at peak, with losses it’s probably 85% output so 270W or with an inverter a little over 1A. 
 

Even a 5kW heat pump will draw 1.5kW so 6A min so it would be permanently drawing from the grid. 

[ashthekid]

Thank you for that, really useful info that I was unaware of. ????

[ProDave]

Even a normal sized 4kW solar PV array would not produce enough power in the winter to run the ASHP.  It is simply impossible to power an ASHP entirely from solar PV.

 

Instead regard solar PV as a way to reduce (not eliminate) what you need to import from the grid and it does this all year even when you are not using heating.

[ashthekid]

So probably still worth the investment on a single PV to simply help reduce your electricity usage? Maybe not substantially but enough to help.

[ProDave]

A single PV panel is probably not viable for domestic use.  The problem with just one panel is the DC voltage is low.  Most of the "proper" solar PV inverters are made to work with a string of panels in series and a higher input voltage, probably a minimum of 4 panels.

 

You can get a single panel to work, I have done that in an odd situation mainly to use up 2 "spare" panels, but the only inverter I could find is one of those horribly cheap "no name" Chinese inverters on ebay, except they are not as cheap now, I bought mine for £50 but they are now more like £75.  But they are not reliable, I have repaired mine once at not much more than 1 year old.  I am not sure what I will do if it goes again and I cannot repair it, I am not minded to buy the same one again, but don't know of a respected make that would do the job.

[NSS]

16 hours ago, ProDave said:

A single PV panel is probably not viable for domestic use.  The problem with just one panel is the DC voltage is low.  Most of the "proper" solar PV inverters are made to work with a string of panels in series and a higher input voltage, probably a minimum of 4 panels.

 

You can get a single panel to work, I have done that in an odd situation mainly to use up 2 "spare" panels, but the only inverter I could find is one of those horribly cheap "no name" Chinese inverters on ebay, except they are not as cheap now, I bought mine for £50 but they are now more like £75.  But they are not reliable, I have repaired mine once at not much more than 1 year old.  I am not sure what I will do if it goes again and I cannot repair it, I am not minded to buy the same one again, but don't know of a respected make that would do the job.

 

Any number of new builds around here with as few as two PV panels on the roof. Presumably there to help the developer reach the required EPC but, from what you say Dave, probably all but useless.

[ProDave]

4 minutes ago, NSS said:

 

Any number of new builds around here with as few as two PV panels on the roof. Presumably there to help the developer reach the required EPC but, from what you say Dave, probably all but useless.

They will no doubt help, but as you say probably there for the extra couple of SAP points needed to scrape a building regs pass.

 

I would be interested to see what small inverters they use.  I guess they don't care if they fit one of the cheap Chinese mini inverters and it goes pop after a year.  The home owner would probably not even notice, especially if it was hidden away in the loft.

[TonyT]

Personally I think it helps, even it it covers the standby/ phantom loads of the house, it something.

 

if every new install was required I have PV can’t be a bad thing

[dpmiller]

why would you go with a really crappy chinesium inverter @ProDave when a "proper" microinverter isn't much more expensive?

[Triassic]

20 minutes ago, NSS said:

Any number of new builds around here with as few as two PV panels on the roof.

Some new builds close to me have four panels. I was thinking what a waste of time.

[ProDave]

21 minutes ago, dpmiller said:

why would you go with a really crappy chinesium inverter @ProDave when a "proper" microinverter isn't much more expensive?

Because at the time I could not find a "proper" inverter that would work with just one 30V panel.  Please enlighten me.

[PeterW]

15 minutes ago, Triassic said:

Some new builds close to me have four panels. I was thinking what a waste of time.

Welcome to improving a SAP score ..!!

 

We have a new development with them near us and two of the houses have them on NW facing roof slopes so they will generate naff all but help the house get a “better” SAP score...!

 

32 minutes ago, TonyT said:

Personally I think it helps, even it it covers the standby/ phantom loads of the house, it something.

 

if every new install was required I have PV can’t be a bad thing

 

Agree about installing - the US did something similar with their 1m solar roofs initiative, but the cost in the UK far outweighs any benefit. A single panel will generate about 250kWh annually in a perfect installation so around £40 of peak electric - at current rates that will be around 7.5 years to pay back just its install costs. 

[TonyT]

14 minutes ago, ProDave said:

Because at the time I could not find a "proper" inverter that would work with just one 30V panel.  Please enlighten me.

https://www.pluginsolar.co.uk/?product_cat=micro-inverters
 

 

couple of inverters on gumtree at the moment in your area, in case you are looking. Not microinverter just the normal type

Edited March 7, 2021 by TonyT

[Nickfromwales]

A friend of mine had installed 4 x 250w panels he had second hand. They’re doing a great job with a surprisingly decent output and very much worth the effort IMO. 
Developer panels are prob ones with micro inverters factory fitted on the rear of the panel so a direct AC connection is quick and simple ( plug ‘n play ).

If I had to spend a couple of grand to save a couple of grand over 10 years and was no worse off at the end of it, I would do so simply to say fcuk you to the grid and the “big 6”. 
I think every home in the UK should have a minimum of 2-4 panels to input the grid with smart meters ensuring that what is exported is given back. A lot of UK homes have people out 9-5 and that’s a window of opportunity to produce some clean energy. 
Won’t happen of course, because the government is too focused on giving people money to have PV on the roof! FiT is just another of the utterly perverse schemes out there. Bonkers. That money should go to incentivising ( supporting ) homeowners to fit small arrays. 

Edited March 7, 2021 by Nickfromwales

[Nickfromwales]

And yes, I’m talking about the FiT that people will still be getting for the next Christ knows how long. 

[ProDave]

3 minutes ago, TonyT said:

https://www.pluginsolar.co.uk/?product_cat=micro-inverters
 

 

I looked at those and found this

 

In order to comply with G98/G99 regulations, each Enphase Micro-Inverter system requires an

Enphase Envoy Device to commission the system AND it needs to be left on site permanently.

 

So for 1 panel and 1 micro inverter that adds a lot of extra cost.

 

It is not clear if you could just use one of those microinverters without the Envoy device but I bet even if it worked, that's your 25 year warranty down the pan.

 

I was looking for a decent equivalent to the Chinesium micro inverter.  DC in one end, grid tied ac out the other, nothing else needed.  Just need to find a reliable version of that next time my Chinesium one lets some of it's smoke out.

[SteamyTea]

5 hours ago, Nickfromwales said:

A friend of mine had installed 4 x 250w panels he had second hand

So about 1 MWh/year.

5 hours ago, Nickfromwales said:

A lot of UK homes have people out 9-5 and that’s a window of opportunity to produce some clean energy. 

Trouble is that it will be going into the main grid, via the very much larger local grid losses.

 

Much better for developers to buy some land and stick a large solar farm on it with a dedicated connection.

 

A lot of houses are just not suitable for PV, the roofs are at the wrong azimuth, shaded, too remote a location etc.

 

Having said that, I still think about fitting some to my house.  If I cheat a little (use the full width of my roof) I should get 8 off standard 1.6m by 1m modules on the SW facing side.

Enough to heat DHW for 8 months of the year.  So 2.4 kW_p.

[dpmiller]

5 hours ago, ProDave said:

I looked at those and found this

 

 

 

 

So for 1 panel and 1 micro inverter that adds a lot of extra cost.

 

It is not clear if you could just use one of those microinverters without the Envoy device but I bet even if it worked, that's your 25 year warranty down the pan.

 

I was looking for a decent equivalent to the Chinesium micro inverter.  DC in one end, grid tied ac out the other, nothing else needed.  Just need to find a reliable version of that next time my Chinesium one lets some of it's smoke out.

 

I went with Hoymiles microinverters. They work perfectly well standalone, the DTU (equivalent to the Envoy) is only for data logging purposes although it does give the factory access to the devices to for firmware upgrades/ programmable limiting etc; thus the G98/9 requirement

. Midsummer don't sell them into the UK any more but they have them on their .ie site.

 

https://midsummer.ie/buy/hoymiles/hoy-mi300

 

I didn't get a DTU to begin with but have one now and am just awaiting an account being set up for me.

[ProDave]

What would make sense to me, is every business premises installing solar PV on it's roof.  They are working in the daytime (mostly) so ideally placed to self use all that they can generate.

 

If the rules on how much you can export were more flexible (i.e. take self usage into account rather than the silly rule that assumes all you generate will be exported) then they could fill their entire roof with PV.

[TonyT]

And let any qualified electrician do the install and stop rip off schemes like MCS

 

[SteamyTea]

46 minutes ago, ProDave said:

What would make sense to me, is every business premises installing solar PV on it's roof. 

I think what holds that back is the business model on commercial buildings.  The building owner may not be the building management company, or the freeholder. Lease holding companies can put stringent rules in place as well.

38 minutes ago, TonyT said:

And let any qualified electrician do the install and stop rip off schemes like MCS

 

Not sure I want an electrician ripping my roof off, drilling into rafters, fitting flashing, or doing the structural calculations.

The answer is to allow self management of the installation by making the rules and regulations accessible and clear.

DNOs could help by having an open register of how much capacity can be fitted in any area, and what any upgrade costs would be.

Edited March 7, 2021 by SteamyTea

[Stones]

4 hours ago, TonyT said:

And let any qualified electrician do the install and stop rip off schemes like MCS

 

 

You don't need an MCS installer to install PV. As long as you have type compliant equipment, and the grid connection is made by a competent person, i.e. a qualified electrician, you're good to go. Once installed, notify DNO. All very straight forward.

 

The only benefit of MCS is it would allow you to claim FiT and export payments.

[TonyT]

I know but the industry still trades on everything being MCS accredited equipment and installers bumping costs up.

got my sunny boy inverter in storage and await panels for a diy install on my garage

 

 

[ashthekid]

So going back to my original question of 1 Solar PV not being enough to generate a usable amount for a ASHP, would 2 or 3 be enough or still not worth it?

Out of curiosity, would a slate tile PV be of any use if a large enough area could be used to generate electricity?