Big Neil Posted January 30, 2019 Share Posted January 30, 2019 I appreciate of course that there are lots of variables, tree coverage, cloud cover, snow cover etc etc. However all other things being equal and assuming for the sake of chaos an approximately east west orientation (if that actually makes a difference). How much PV would you want to put on your roof, to ensure that you never had to pull from the grid even on an averagely dull day. Lets assume for the sake of removing some more variables also, that you don't have an electric car to charge, or if you did could just charge at night, didn't have any massive drains on power like an industrial launderette attached to your house, and had lets say 2 tesla power walls as backup and for use at night. If it helps whoever wants to answer, i suppose you could even assume you aren't grid tied. Obviously there are major contributors to energy reduction like a house being passiv, having relevant smart systems which help control usage and such. lets assume at least the house is passiv dertified Link to comment Share on other sites More sharing options...
scottishjohn Posted January 30, 2019 Share Posted January 30, 2019 I take it grid connection is not possible and no hydro available?. It can be on the ground if you can get better orientation that way shading from anything is a major thing as it could cut in half the number of hours in a day you could get power production where you are in the country will also make a difference Link to comment Share on other sites More sharing options...
Big Neil Posted January 30, 2019 Author Share Posted January 30, 2019 evening John. It was more of a hypothetical question than anything, but lets say somewhere around OXford in the countryside as opposed to a town, no trees nearby to cause shade issues and that grid would be available but that i didn't want to connect and i wanted it on the roof not the ground. Link to comment Share on other sites More sharing options...
ToughButterCup Posted January 30, 2019 Share Posted January 30, 2019 21 minutes ago, Big Neil said: [...] How much PV would you want to put on your roof, to ensure that you never had to pull from the grid even on an averagely dull day. [...] Too much. As usual, @JSHarris has examined and written about this issue in some detail , and so has @ProDave. I'm damned if I can find the thread where they both discuss the topic in some detail - it was a while ago. And I've got to fizz off somewhere now.... I'll try and remember when and which thread. I remember one phrase in particular - something like '....well if the power's off for that long, treat the family to a meal out....' No point in writing the same stuff twice. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted January 30, 2019 Share Posted January 30, 2019 I doubt you could do it with just PV, TBH, as there will be periods in winter when you get several days in a row with virtually no generation, and even when you do get some generation in winter it's unlikely to be enough to top up any battery system so that you can ride out the poor generation days. Combining some wind generation might get you there, but in middle England I think even then you'd struggle, and would end up relying on a generator for a few weeks in the year. One person with lots of off-grid experience is Paul Camilli, up on Raasay. He has a lot of PV, wind generation and some background hydro generation yet still reckons a reliable generator is a must have. His blog is worth a read: https://lifeattheendoftheroad.wordpress.com/ Link to comment Share on other sites More sharing options...
Big Neil Posted January 30, 2019 Author Share Posted January 30, 2019 quality stuff one and all - thanks Link to comment Share on other sites More sharing options...
Ed Davies Posted January 30, 2019 Share Posted January 30, 2019 This is very much a how-long-is-a-piece-of-string question. It depends a lot on your energy needs and how much you're willing to trim your lifestyle to match the available energy. Oh, batteries are a bit low and it's not looking like it'll be sunny tomorrow, I'll just microwave this meal out of the freezer rather than baking those potatoes I planned. It seems to me that wind turbines complement PV very well. There are lots of dull days and lots of windless days but it's very rare for dull lulls to last more than a day or so. Link to comment Share on other sites More sharing options...
Big Neil Posted January 30, 2019 Author Share Posted January 30, 2019 Just now, Ed Davies said: This is very much a how-long-is-a-piece-of-string question. It depends a lot on your energy needs and how much you're willing to trim your lifestyle to match the available energy. Oh, batteries are a bit low and it's not looking like it'll be sunny tomorrow, I'll just microwave this meal out of the freezer rather than baking those potatoes I planned. This was in the back of my mind of course. I was just interested to see what solutions the heads came up with. Link to comment Share on other sites More sharing options...
billt Posted January 30, 2019 Share Posted January 30, 2019 You simply can't do it in the UK with PV. I have a total of about 16kW of panels and the average daily output for December was 10.8kWhr and for January about 11.5kWhr with many days producing less than 3kWhr. With enough batteries you could be independent of the grid for 9 months of the year with my grossly oversized array. No chance with a typical 3-6kW array and normal levels of consumption. Link to comment Share on other sites More sharing options...
scottishjohn Posted January 30, 2019 Share Posted January 30, 2019 1 hour ago, Big Neil said: evening John. It was more of a hypothetical question than anything, but lets say somewhere around OXford in the countryside as opposed to a town, no trees nearby to cause shade issues and that grid would be available but that i didn't want to connect and i wanted it on the roof not the ground. become a hermit LOL Link to comment Share on other sites More sharing options...
Ed Davies Posted January 30, 2019 Share Posted January 30, 2019 2 hours ago, billt said: You simply can't do it in the UK with PV. I have a total of about 16kW of panels and the average daily output for December was 10.8kWhr and for January about 11.5kWhr with many days producing less than 3kWhr. That'd do me, my average consumption for 2018 December was 4.44 kWh/day (plus burning a not-insignificant amount of oil). Depends, of course, a bit on the statistics of the lengths of the runs of power production less than that. And, as I say, your flexibility to adapt usage. Link to comment Share on other sites More sharing options...
ProDave Posted January 30, 2019 Share Posted January 30, 2019 1 hour ago, Ed Davies said: That'd do me, my average consumption for 2018 December was 4.44 kWh/day (plus burning a not-insignificant amount of oil). I marvel how you do that. My "non heating & non DHW" usage is running at about 14KWh per day and I just can't seem to find a way to get it down. Link to comment Share on other sites More sharing options...
Ed Davies Posted January 30, 2019 Share Posted January 30, 2019 OTOH @ProDave my average oil use (in kWh) daily since last September is nearly your weekly heating energy use in this cold period. OK, your actual heating energy use, including that harvested from outside by your ASHP, will be 3 to 4 times more but still… How confident are you of that 14 kWh/day figure? It's not your total metered use minus your metered heat pump use, is it? Subtract one big number from another and any discrepancy in the measurement gives a big error in the result. My background energy use (for router, data logging stuff, internet phone) is just under 20 W. The fridge uses about another 15 W on average. So that's about 0.84 kWh per day. The pump and boiler take about 150 W and ran 25% of the time in December (which was reasonably mild) so about 0.9 kWh/day. Laptop and monitor plus a bit of LED lighting takes the background 20 W up to 90 W so an additional 70 W for, when I'm in, 16 hours a day so about 1.12 kWh. So that's 2.86 kWh/day. The rest is cooking and the 7 kW electric shower. Link to comment Share on other sites More sharing options...
ProDave Posted January 30, 2019 Share Posted January 30, 2019 Yes I read the import meter weekly, and I have a meter measuring heating and hot water usage, so anything else is "stuff" mvhr and treatment plant each use about 2KWh per day constant. I suspect Fridge, WM, DW and tumble dryer are the biggest culprits. I must get a plug in KWh meter some time so I can monitor each individually for a week at a time and see how much each really uses. Link to comment Share on other sites More sharing options...
Onoff Posted January 30, 2019 Share Posted January 30, 2019 (edited) December 8th I had 300gal of oil left. As of today down to about 175gal so about 125gal/570L used for CH and DHW. Feels like I'm using a lot. Backed up like tonight by a 3kW fan heater in the lounge. Edited January 30, 2019 by Onoff Link to comment Share on other sites More sharing options...
Ed Davies Posted January 30, 2019 Share Posted January 30, 2019 Since December 8th my logging estimates my boiler's run for 330 hours. With the nominal consumption of the fitted nozzle (0.55 USgal/h) that's 2l/h so 660 litres. From comparison of similar numbers with actual amounts put in the tank that's probably a slight over-estimate so probably pretty close to @Onoff's 570 l. I'm a tad further north, of course, but not in the frost hollow or whatever is giving @ProDave his overnight lows. Link to comment Share on other sites More sharing options...
Onoff Posted January 30, 2019 Share Posted January 30, 2019 17 minutes ago, Ed Davies said: I'm a tad further north, of course, but not in the frost hollow or whatever is giving @ProDave his overnight lows. Frost hollow? Got that here. Sun doesn't get high enough for long enough to melt the snow. Like that micro climate in Z For Zacariah! You'd need orange balls to play the course next to me at the mo. I could do with a thermal camera I reckon to pinpoint all my loss points. Link to comment Share on other sites More sharing options...
Ferdinand Posted January 31, 2019 Share Posted January 31, 2019 A quick one for @JSHarris. Jeremy Has your idyllic valley suddenly turned into a frost pocket? Asking out of genuine interest. I suspect it may be big enough to avoid it if you have decent air movement in there, or are not right at the bottom. Ferdinand Link to comment Share on other sites More sharing options...
Onoff Posted January 31, 2019 Share Posted January 31, 2019 We should have a leader board / section for the lowest ambient temperature. I'm never going to win but did have to pour half my cup of tea over the gate lock this morning! Link to comment Share on other sites More sharing options...
Jeremy Harris Posted January 31, 2019 Share Posted January 31, 2019 1 hour ago, Ferdinand said: A quick one for @JSHarris. Jeremy Has your idyllic valley suddenly turned into a frost pocket? Asking out of genuine interest. I suspect it may be big enough to avoid it if you have decent air movement in there, or are not right at the bottom. Ferdinand Still a bit warmer here, -2.6 deg C outside at the moment and Boscombe Down is reporting -4.7 deg C, Southampton -7.0 deg C, Middle Wallop (where my wife is currently driving to) is -5.0 deg C. Link to comment Share on other sites More sharing options...
ProDave Posted January 31, 2019 Share Posted January 31, 2019 When you see on the weather the statement "colder in sheltered glens" that is us. We are 3 miles inland from the Cromarty Firth and in a glen with hills rising in all directions. When it is still, as it is now, we do indeed seem to be a frost pocket, though if you think it is bad here, take a walk down to the river at the bottom of the glen it's even colder down there. Last night it was only -11, the night before -14, and it has only been above 0 for one day in the last 2 weeks. This is pretty normal to get a few weeks like this each year. And throw in a bit of snow just for fun. But the new house is coping well and it's warm inside and the ASHP is handling the cold weather okay. Link to comment Share on other sites More sharing options...
Ferdinand Posted January 31, 2019 Share Posted January 31, 2019 WIth this posh new car the number of things with heaters is ridiculous. IT takes a little time to switch them all on ... windscreen, rear screen, mirrors, steering wheel, seats. There is even an ice scraper inside the fuel cap cover, which works well except when that is more frozen up than the doors. MInus five degrees here. F Link to comment Share on other sites More sharing options...
Onoff Posted January 31, 2019 Share Posted January 31, 2019 Seem to recall -19 a few years back in't valley. Let's see what tonight brings aside from snow from 18.00 to 23.00 Add snowmobile to the project list ( I've got the plans)! Link to comment Share on other sites More sharing options...
Jeremy Harris Posted January 31, 2019 Share Posted January 31, 2019 5 minutes ago, Ferdinand said: WIth this posh new car the number of things with heaters is ridiculous. IT takes a little time to switch them all on ... windscreen, rear screen, mirrors, steering wheel, seats. There is even an ice scraper inside the fuel cap cover, which works well except when that is more frozen up than the doors. MInus five degrees here. F 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. Link to comment Share on other sites More sharing options...
Onoff Posted January 31, 2019 Share Posted January 31, 2019 Ref off grid again, depending on how much source material you have you could investigate the Jean Pain compost water heating techniques. Then there's say biogas production from green/"brown" waste. Mother Earth News have a good (imo) biogas design. There's also a Nepalese biogas dome design around. In Winter of course these systems tend to go dormant but you could warm them up with an oversize solar thermal array home brewed with a Pex-Al-Pex loop. Link to comment Share on other sites More sharing options...
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