stand alone pv systems

[scottishjohn]

with current and projected price rises  I,m wondering if its getting close to be viable for stand alone pv system   and batteries and a stand by gen for worst times

rather than 30k for a supply ?

and use it for ufh +hot water and no ASHP?

 

[SteamyTea]

Run your best estimate of usage though PVGIS 

[nod]

The Problem with PV is that it generates the most energy when you need it the least

I think you would need a lot of expensive batteries 

Being totally independent and saving 30k on a connection would certainly blow Tge payback argument out of the water 

If such a thing was possibly 

[scottishjohn]

looking at power prices now  and the 50% rise forecast in next year  it  is maybe  coming a more viable 

I can get a supply ,but if FIT stays at 4p - 

23 minutes ago, SteamyTea said:

R

it would maybe seem better choice to just go stand alone +batteries and gen for worst months ?

 something to look into in new year .

 my roof will faces s/w and be 24m long and 3m tall =24sqm - no shading due to where house is  --so no shortage of space and if I could save on slates as well -it could add up to being the way to go 

[scottishjohn]

24 minutes ago, SteamyTea said:

Run your best estimate of usage though PVGIS 

no idea at this time until final design is completed

as i,m building another house inside my granite outer structure/

TF is  what has been suggested ,but maybe a block type and use block and beam for second floor ,which will add a nice big thermal storage  to new house ?

 I,m doubtful it will be easy to get a TF kit that will easily inside thei old house ,as walls are unlikely to be true  ,so maybe just build inside  with block  or ICF?

no decisions made yet 

planning have eventually replied to me and are promising consent towards end of january 

then  I get  going with quotes etc

 

[SteamyTea]

2 minutes ago, scottishjohn said:

 my roof will faces s/w and be 24m long and 3m tall =24sqm

Be about 30 modules, so 10 kW_p.

So not particular large.

I quickly ran though my location and one near Aberdeen, used 4% as the interest rate, £800/kW_p installed price, came out that the levelized costs was 0.046p/kWh and 0.065p/kWh respectively.  That was for optimised systems.

[ProDave]

The price of Kerosense Vs mains electricity is making a diesel generator look attractive, particularly if you can use the heat it produces as well.

 

That would do the winter, with some batteries so it does not have to run all the time and the PV would do most of the summer.

 

Given your elevation, a wind turbine of a decent size is probably also viable.

[scottishjohn]

1 minute ago, SteamyTea said:

Be about 30 modules, so 10 kW_p.

So not particular large.

I quickly ran though my location and one near Aberdeen, used 4% as the interest rate, £800/kW_p installed price, came out that the levelized costs was 0.046p/kWh and 0.065p/kWh respectively.  That was for optimised systems.

I got more roof space if needed as that was just one side  

I got a south facing shorter one as well and if really needed i got loads of space for ground mounted system 

 i got wrong size it should have been 74sqm  and i could be small on that as guessing how tall it will be --not done the calc  30degree pitch and 2m+ from wall head to ridge 

[SteamyTea]

3 minutes ago, scottishjohn said:

,which will add a nice big thermal storage  to new house ?

Or not.  Any store needs direct heating.  Relying on natural inputs basically means you get cooling.  No one has ever built a large, unheated basement and said 'wow, it is always warmer in here than the house'

Others disagree, but it is what I studied at university and I am happy to stick by my findings.

If you are considering batteries, may as well add a heat pump, for the costs of 4 kWh of batteries you can get 5 kW of heating.

[Onoff]

Pity you can't use the quarry lake for ground source.

[SteamyTea]

7 minutes ago, Onoff said:

Pity you can't use the quarry lake for ground source.

Or water source, get a good CoP from them, as I keep telling the morons are the Jubilee pool who spend over a million doing a geothermal project that failed.  They then put in a WSHP.  They could have just used a couple and drawn energy from the Atlantic.

[joe90]

24 minutes ago, scottishjohn said:

planning have eventually replied to me and are promising consent towards end of january 

then  I get  going with quotes etc

That’s really good to hear ?

[scottishjohn]

31 minutes ago, Onoff said:

Pity you can't use the quarry lake for ground source.

that should all sold by end of january  and its close to 300ft below the house  too expensive for piping 

Edited December 25, 2021 by scottishjohn

[scottishjohn]

33 minutes ago, SteamyTea said:

Or not.  Any store needs direct heating.  Relying on natural inputs basically means you get cooling.  No one has ever built a large, unheated basement and said 'wow, it is always warmer in here than the house'

Others disagree, but it is what I studied at university and I am happy to stick by my findings.

If you are considering batteries, may as well add a heat pump, for the costs of 4 kWh of batteries you can get 5 kW of heating.

what ever heating system i use it will gradually heat up the mass  to ambient in house ,but take long time to cool down  specific heat of concrete is at least 5 times more then water-so it will be a heat sink .

will really depend on cost compared to std type floor -but i could end up with a 7m+ span -so maybe would do away with need for pillars or steels on ground floor ?

[Onoff]

21 minutes ago, SteamyTea said:

Or water source, get a good CoP from them, as I keep telling the morons are the Jubilee pool who spend over a million doing a geothermal project that failed.  They then put in a WSHP.  They could have just used a couple and drawn energy from the Atlantic.

 

Sorry, meant water source.

[scottishjohn]

42 minutes ago, ProDave said:

The price of Kerosense Vs mains electricity is making a diesel generator look attractive, particularly if you can use the heat it produces as well.

 

That would do the winter, with some batteries so it does not have to run all the time and the PV would do most of the summer.

 

Given your elevation, a wind turbine of a decent size is probably also viable.

planning would be a problem i think and would still need batteries  

[Onoff]

As you have elevation...and a digger...

 

Rather than a GSHP loop, is a pipe / single loop in a long trench a feasible option? Thinking if you had to trench from the road  up to the property anyway. 

[scottishjohn]

Just now, Onoff said:

As you have elevation...and a digger...

 

Rather than a GSHP loop, is a pipe / single loop in a long trench a feasible option? Thinking if you had to trench from the road  up to the property anyway. 

no gshp will never be a good choice over ashp  in this country  due to costs  and average winter temp  here is 3c

if it were like canada with  -10 to -20 for 3 months --yes 

 only place it might be is  in a lake where you can just throw the loop in from a boat -but trying get down 1m + on rocky ground --not good 

If I was in the quarry with a 30m deep lake --then yes that could work 

[SteamyTea]

1 hour ago, scottishjohn said:

specific heat of concrete is at least 5 times more then water-so it will be a heat sink .

Concrete

SHC 0.8 kJ.kg^-1.K^-1

Density 2700 kg.m^-3

Heat Capacity 2.16 MJ.m^-3

 

Liquid Water

SHC 4.18 kJ.kg^-1.K^-1

Density 1000 kg.m^-3

Heat Capacity 4.18 MJ.m^-3

 

[nod]

I’ve a friend who has installed GSHPs for about ten years now 

We have a 3 acre field So plenty of room 

Surprisingly he still recommends vertical shafts for the piping Apart from the obvious He recons they outperform laying long runs of pipe 

[Onoff]

10 minutes ago, nod said:

I’ve a friend who has installed GSHPs for about ten years now 

We have a 3 acre field So plenty of room 

Surprisingly he still recommends vertical shafts for the piping Apart from the obvious He recons they outperform laying long runs of pipe 

 

The one commercial one I know of in central London is vertical. Makes sense given space constraints and if you're piling anyway. 

 

A few places are planning retrofit heat pumps, afaic to tick a green box as the buildings in question are neither well insulated nor airtight. 

[nod]

56 minutes ago, Onoff said:

 

The one commercial one I know of in central London is vertical. Makes sense given space constraints and if you're piling anyway. 

 

A few places are planning retrofit heat pumps, afaic to tick a green box as the buildings in question are neither well insulated nor airtight. 

Good point 

nothing to add the shafts if you already have a rig on site 

[SteamyTea]

2 hours ago, nod said:

Surprisingly he still recommends vertical shafts for the piping Apart from the obvious He recons they outperform laying long runs of pipe 

Boreholes will perform better as the temperature is more stable.  Trenched pipework can freeze the ground and this reduces power transfer, this is much less likely to happen with a borehole.  There may also be a lot more free flowing ground water deeper down.

[Marvin]

38 minutes ago, SteamyTea said:

Boreholes will perform better as the temperature is more stable.  Trenched pipework can freeze the ground and this reduces power transfer, this is much less likely to happen with a borehole.  There may also be a lot more free flowing ground water deeper down.

Also the trenches are not really deep enough to avoid being affected by the surface temperature.

[nod]

50 minutes ago, SteamyTea said:

Boreholes will perform better as the temperature is more stable.  Trenched pipework can freeze the ground and this reduces power transfer, this is much less likely to happen with a borehole.  There may also be a lot more free flowing ground water deeper down.

Although I’m not using piled foundations 

I think I will go with virtual piping