being off grid

[billt]

13 hours ago, Ed Davies said:

 

That'd do me, my average consumption for 2018 December was 4.44 kWh/day

 

But would you want to pay £20,000+ for a battery based system to produce that? (About 90 years worth of electricity at 4kWh a day, 15p per unit.)

 

4kWh a day is exceptionally low. AIUI the average household electricity consumption is about 12kWh per day. We're profligate and use about 18-20kWh a day, mainly computer stuff that's on continuously.

[Ed Davies]

20 minutes ago, billt said:

But would you want to pay £20,000+ for a battery based system to produce that?

 

Yes. If the plot's £10 or 15k cheaper because of the cost of getting power to it. As mine was; £35k for 2.4 hectares with outline planning permission for two houses.

 

Also, that 4 kWh per day is bare electricity use. My house design includes a large thermal store which will need charging in the autumn to get through the coldest, dullest 8 weeks of the year. The excess of PV during that time (say from the beginning of September, or even earlier, onwards) would contribute to that so it's not just saving 4 kWh/day. Electricity here is already more than 15p/unit and will likely get more expensive over the years.

[Gone West]

11 hours ago, ProDave said:

mvhr and treatment plant each use about 2KWh per day constant

That doesn't sound right, neither of mine use anywhere near as much as 2kWh a day each.

[scottishjohn]

If i were going off grid ,then I would have solar thermal in the mix to heat your water and save pv for things that must use electric .

a bright day in winter will still give you 50c on panels to charge up your thermal store ,

I used a thermal store with 3 coils --solar in ,mid tank UFH out ,top dhw -which was then blended with cold to only send water to taps at 50c.

main volume of tank was heated if required by lpg ,but that could be Pv  or anything .

downside to my system was not large enough thermal store --so could not use all solar avialable alot of the time .

will not make that mistake again 

I was discounting it on new build but now no FIT from pv and ASHP maybe not much ,due to house energy rating -,its back on my list .

but got to wait for heat load of new house to  go nay further with tank size computations..

build a concrete one surrounded in pretty stone in middle of house --any energy that leeks will heat house anyway 

[Ed Davies]

32 minutes ago, scottishjohn said:

If i were going off grid ,then I would have solar thermal in the mix to heat your water and save pv for things that must use electric .

 

Agreed. I have 8 x 20 x 47mm evacuated-tube panels stored in the shed here ready to go along the bottom of the south side of the house. Bought them a few years ago when Navitron had a batch going very cheap (about half the normal price). Might only have room for 6 or 7 though, allowing fire escape from the bedroom windows, will have to measure up exact window positions given rafter placement but it's not the most urgent consideration.

 

However, I'd put it the other way round: use solar thermal for things which have to use heat then electricity (PV plus probably a bit of wind) for everything else. It's a lot easier to turn spare electricity into heat than spare heat (especially low-grade heat) into electricity. Thank you M. Carnot. I.e., the extra capacity required beyond that needed in, say, October and March should  produce electricity rather than heat. Excess heat in July and August is a pain to get rid of and possibly actually dangerous whereas too much PV is easy to deal with, put it in an electric car or leave it in the panels or…

Edited January 31, 2019 by Ed Davies

[scottishjohn]

If you go for small thermal store  dumping solar is easy use an  old house rad or a loop of pipe in  water  or ground and divert when needed .

having had solar for 20 years my way will be just a big tank ,or multiple cascade tanks -so I never get to postion like before where i had 180c+ melting foam insulation of copper pipes and thermal store boiling .LOL.

basic rule would be 20-30tubes to a 300litre tank should ok where you are

solar is simple if you have enough storage ,you can even get a small pv panel to run the circ pump independently 

no over heating --but not much storage for later

6 or 7 tubes will never overheat normal thermal store and  probably not worth the effort.

all plumbing must be copper --no plastic anywhere,cos if senor goes loopy as mine did you will melt the pipes.

If you going to do it and you don,t have a solar controller   I have a new one un-used kingspan  sc400  cost £130     £60 +carriage 

I wll be using something more complicated to control all heat inputs or maybe using ashp controller  as fitted to  my ecodan  in current house

[Ferdinand]

3 hours ago, JSHarris said:

 

 

With mine I just press the button on the remote (or via the Connected Drive app) up to 30 minutes before I want to drive off and it turns on whatever heating/cooling is needed so that all the windows, mirrors etc are clear and the interior as at whatever temperature I've set it to, by the time I get in.  The Prius had a similar feature on the remote, but only for pre-cooling, which wasn't something I often used.  The BMW preconditioning feature seems a lot more useful, so much so that I find I use it all the time.  If the car happens to be plugged in to the charger at the time it draws all the power needed to pre-condition the car from that, which makes a noticeable difference to battery range.

 

I am still learning to drive my presets !

 

F

[ProDave]

8 hours ago, PeterStarck said:

That doesn't sound right, neither of mine use anywhere near as much as 2kWh a day each.

Definitely right for the treatment plant. The current measurement might even suggest it uses more but it has a lousy power factor.  When I first installed it I ran it for a few days with absolutely nothing else on, and the electricity meter clicked up 2KWh per day.  The mvhr is probably less, I have current measurements (somewhere) for all the different fan speeds but have never done that metered KHh test on that alone.

[Jeremy Harris]

So, 2 kWh for the treatment plant pump is ~ 83 W, which seems on the high side.  Probably well worth looking at fitting a timed relay or SSR to cycle the pump on and off I think.  Our pump is rated at 40 W, but in reality it seems to use around 44W.  I have it cycling on and off, 30 minutes on, 30 minutes off, so the mean power consumption is around 22 W, or a bit over 0.5 kWh, so around 1/4 of the energy yours is using. 

 

Our usage will be a little lower than yours, with just the two of us, but I doubt that makes a significant difference in terms of the BOD of the effluent, as much of that seems to come from "other than human waste" that goes down the drains.  Our Bio Pure unit is near-identical in design to your unit as well, so probably has a very similar air demand.

 

 

[NWGEAR]

On 31/01/2019 at 08:30, JSHarris said:

The BMW preconditioning feature

 

Me mate hooked this up to Alexa...  "Alexa, precondition the BMW"  he say. Tosser ?