SteamyTea Posted January 2, 2023 Share Posted January 2, 2023 1 minute ago, Roger440 said: Same problem. Sun doesnt shine much in the winter. You cant sensibly store months of electricity to run said heat pump. No it don't. What is known though is the geometry, this is unaffected by cloud cover. So changing the array to be almost vertical and south facing helps a fair amount (change the slope in PVGIS and see what you can get). What is also known us where the sun will be during the hours of daylight, so it become easy to know when a heavier load can be applied. The times that lower output happen i.e. 8:30 to 10:30 and 14:30 to 16:30 are the times to top up the batteries. The idea if the batteries is to overcome the higher start up current of a heat pump, not to run anything long-term i.e. resistance heaters. The idea is similar to a hybrid car, use stored power to overcome short spells of high power. Link to comment Share on other sites More sharing options...
pdf27 Posted January 2, 2023 Share Posted January 2, 2023 21 minutes ago, SteamyTea said: Only once it has gone past the store temperature. This means it can loose our a lot of the time. Generally at sub 100W/m², PV is more effective, and cheaper. Comes back to the question of what you're trying to do. If you're storing solar energy in summer for use in winter, you're likely to be capturing it when the resource is >500W/m2 and be trying to capture a hell of a lot of energy to use in winter - hence most people trying to do this have gone for solar thermal. FWIW I think in this case it's a dead end either way! Link to comment Share on other sites More sharing options...
pdf27 Posted January 2, 2023 Share Posted January 2, 2023 8 minutes ago, Roger440 said: My house is mostly 170 years old, so zero possibility of passivhaus standards. Its going to use energy, even with sensible pragmatic works applied. Having ample space, i could generate enough PV or solar thermal in summer to run it in winter. Thats why i looked at milk tankers, buried if need be. But its simply economic madness. So yes, Yes, buying shares or similar seems to be a much better solution than actually solving the problem! Even at a £1 per Kwh, it still doesnt even start to stack up. Realistically I think your best options are to either buy Ripple shares or put in enough PV that the payment for your summer exports covers your winter energy consumption. Ripple is a lot cheaper. 1 Link to comment Share on other sites More sharing options...
Roger440 Posted January 2, 2023 Share Posted January 2, 2023 5 minutes ago, SteamyTea said: No it don't. What is known though is the geometry, this is unaffected by cloud cover. So changing the array to be almost vertical and south facing helps a fair amount (change the slope in PVGIS and see what you can get). What is also known us where the sun will be during the hours of daylight, so it become easy to know when a heavier load can be applied. The times that lower output happen i.e. 8:30 to 10:30 and 14:30 to 16:30 are the times to top up the batteries. The idea if the batteries is to overcome the higher start up current of a heat pump, not to run anything long-term i.e. resistance heaters. The idea is similar to a hybrid car, use stored power to overcome short spells of high power. Im aware of all that. Indeed, setting it up almost vertical for winter makes perfect sense, which i can do as it wont be roof mounted. However, Id still need a solar farm in mid winter though! 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted January 2, 2023 Share Posted January 2, 2023 3 minutes ago, pdf27 said: FWIW I think in this case it's a dead end either way! I do as well. Best you can hope for is to reduce losses from the building. So extra insulation on the colder North and East sides, floors and ceilings/roof. Find the best price you can export PV at, some say they are getting 7.5p/kWh and maximize your revenue. Use that to offset winter costs. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 2, 2023 Share Posted January 2, 2023 (edited) 4 minutes ago, Roger440 said: However, Id still need a solar farm in mid winter though! How many kWh/day of thermal energy do you really need? Edited January 2, 2023 by SteamyTea Link to comment Share on other sites More sharing options...
Roger440 Posted January 2, 2023 Share Posted January 2, 2023 5 minutes ago, pdf27 said: Realistically I think your best options are to either buy Ripple shares or put in enough PV that the payment for your summer exports covers your winter energy consumption. Ripple is a lot cheaper. Interesting. But i note they dont answer the question, what if they go bust? Which they probably will. I think investing in the stock market would be much safer. 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted January 2, 2023 Share Posted January 2, 2023 (edited) 10 minutes ago, pdf27 said: buy Ripple shares What will happen if the price of wind (and solar) energy is reduced to close to gas prices though legislation. RE companies are riding high at the moment because they were given a good deal a few years back. Those deals are now stopped and the legacy deals are coming to an end in the next decade. There may be a reason they are chasing small investors rather than the large institutional investors who know the industry very well. Edited January 2, 2023 by SteamyTea Link to comment Share on other sites More sharing options...
Roger440 Posted January 2, 2023 Share Posted January 2, 2023 7 minutes ago, SteamyTea said: How many kWh/day of thermal energy do you really need? My new house is smaller than my old one, but less thermally effiecent. Early indications are an oil consumption rate similar to the old one. Which was about 1700 litres of oil a year, so circa 16000kwh annually. Ok, im going to improve the current situation, so lets say im really good and halve it 7500. Just rough numbers its going to need over 1000kwh per month in mid winter, or 33kwh per day. Feel free to point out what bit ive got wrong, maths isnt my strong point, or how much PV i need in december / january. But its going to be an awful lot? Link to comment Share on other sites More sharing options...
Roger440 Posted January 2, 2023 Share Posted January 2, 2023 11 minutes ago, SteamyTea said: What will happen if the price of wind (and solar) energy is reduced to close to gas prices though legislation. RE companies are riding high at the moment because they were given a good deal a few years back. Those deals are now stopped and the legacy deals are coming to an end in the next decade. There may be a reason they are chasing small investors rather than the large institutional investors who know the industry very well. All good valid points, AND it still looks like a high risk for investor. Give us all your money now, for payback in the future. Not a new idea and we know how it often ends. I suspect this well outside the scope of any financial regulation. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 2, 2023 Share Posted January 2, 2023 1 minute ago, Roger440 said: Feel free to point out what bit ive got wrong, maths isnt my strong point, or how much PV i need in december / january. But its going to be an awful lot? Right, let us say you need 40 kWh (not kwh) a day. Let us also assume you get a heat pump with a CoP of 2.5 (though you would be better off with an A2AHP). So you ned to generate 16 kWh/day. A 1 kWp array, hanging on a south facing wall, will, on average, in December, produce 40 kWh. So 1.3 kWh/day. That implies you need a 12.5 kWp system. Now you need to give yourself a bit of head room, so a 16 kWp system should do it. General rule of thumb about storage is a third of the array size, so 5 to 6 kWh of battery storage. That may be reduced a bit if you can store more thermally, say in a couple of 300 lt cylinders. It is a lot, but not a huge amount. About 80 m2, 16 m by 5 m. 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted January 2, 2023 Share Posted January 2, 2023 11 minutes ago, Roger440 said: Give us all your money now, for payback in the future Or, give us more than the value of the assets and we will return you a small part of it. I sometimes think that the people that run these schemes don't know what they are doing, rather than actively trying to rob people. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted January 2, 2023 Share Posted January 2, 2023 1 hour ago, Iceverge said: Scanhome and University of Ulster did a project. A year in the life of a passive house with solar energy store V0.9 (energyexpertise.net) That's an interesting read - 23T of water and you cannot make it pay. Link to comment Share on other sites More sharing options...
Roger440 Posted January 2, 2023 Share Posted January 2, 2023 11 minutes ago, SteamyTea said: Right, let us say you need 40 kWh (not kwh) a day. Let us also assume you get a heat pump with a CoP of 2.5 (though you would be better off with an A2AHP). So you ned to generate 16 kWh/day. A 1 kWp array, hanging on a south facing wall, will, on average, in December, produce 40 kWh. So 1.3 kWh/day. That implies you need a 12.5 kWp system. Now you need to give yourself a bit of head room, so a 16 kWp system should do it. General rule of thumb about storage is a third of the array size, so 5 to 6 kWh of battery storage. That may be reduced a bit if you can store more thermally, say in a couple of 300 lt cylinders. It is a lot, but not a huge amount. About 80 m2, 16 m by 5 m. Ok, As i said, not good at maths. You introduced a p in there. Not sure what that means? Ive picked up FOC what is described as a 4.5Kw PV array (plus invertor) . Are you saying 4 of these would do the job? Im rather more keen on a massive water tank than batteries. I could potentially then heat it by other means too. Though i do have a battery powered forklift........ Link to comment Share on other sites More sharing options...
SteamyTea Posted January 2, 2023 Share Posted January 2, 2023 9 minutes ago, Roger440 said: You introduced a p in there. Not sure what that means The p means peak, basically the sum of all the panels nominal power. Sometimes you will see a subscript e or t , those mean electrical or thermal. It is easy to have a nominal 4 kWp (actually 16 amps per phase) system fitted as it is, in effect, approved by the local DNO, so if you have 3 phase, easy to have 12 kWp. Too have 16 kWp fitted will require special permission (G99). There are ways around this by limiting exports to 16A, but then, and assuming you go for an MCS installation, you are limited on how much you can get paid. With a larger array of modules (that just means lots of panels) you will be generating more than you can use most of the time, so export payment is worthwhile. Large storage seems a good idea, but if it is too large, then the storage temperature will be lower than optimal most of the time. Why I think 2 or 3 smaller storage cylinders is better than 1 of same volume. A 300 litre cylinder can shower a family of 4 if they are sensible, or one feckless teenage girl with long hair. Link to comment Share on other sites More sharing options...
Gus Potter Posted January 2, 2023 Share Posted January 2, 2023 (edited) 4 hours ago, SteamyTea said: ather than look at how much energy can be stored, look at how much energy will be lost, and how much insulation is needed to reduce those losses. Also look up Newtons Law of Cooling. What a great thread. @SteamyTea you have encouraged me to bush up on my maths in this area. Thank you. Edited January 2, 2023 by Gus Potter 1 Link to comment Share on other sites More sharing options...
Marvin Posted January 2, 2023 Author Share Posted January 2, 2023 1 hour ago, Roger440 said: Likewise. But if using PV, it needs to be more like 4 months surely? Which is where my crazy musings fall over. Theres no practical way to store enough energy for heating through a winter from PV. I hope to find out. We require (but for us the figures may be different from others) about 500kWh for the winter Link to comment Share on other sites More sharing options...
SteamyTea Posted January 2, 2023 Share Posted January 2, 2023 7 minutes ago, Gus Potter said: What a great thread. @SteamyTea you have encouraged me to bush up on my maths in this area. Thank you. Yes brush up, as it is easy to make an mistake, I do them a lot. Link to comment Share on other sites More sharing options...
Roger440 Posted January 2, 2023 Share Posted January 2, 2023 8 minutes ago, SteamyTea said: The p means peak, basically the sum of all the panels nominal power. Sometimes you will see a subscript e or t , those mean electrical or thermal. It is easy to have a nominal 4 kWp (actually 16 amps per phase) system fitted as it is, in effect, approved by the local DNO, so if you have 3 phase, easy to have 12 kWp. Too have 16 kWp fitted will require special permission (G99). There are ways around this by limiting exports to 16A, but then, and assuming you go for an MCS installation, you are limited on how much you can get paid. With a larger array of modules (that just means lots of panels) you will be generating more than you can use most of the time, so export payment is worthwhile. Large storage seems a good idea, but if it is too large, then the storage temperature will be lower than optimal most of the time. Why I think 2 or 3 smaller storage cylinders is better than 1 of same volume. A 300 litre cylinder can shower a family of 4 if they are sensible, or one feckless teenage girl with long hair. No 3 phase here. This was/is going to be DIY. It simply wont fly otherwise. Though, by my calcs id need another 50 odd panels. Ones like mine are going for around £100 a pop, so that would be £5k. I think i need a lie down! I take your point about summer export, though it was something id rather avoid. More complication and cost. Good point on the storage size. Hadnt considered that. I was considering large in case i wanted to add a gasification log boiler which would generate a lot of heat quickly (as per previous discussions). Need to ponder how that would work with smaller multiple tanks. A complicated control system i suspect. I dont like complicated. complication = unreliability. Link to comment Share on other sites More sharing options...
Radian Posted January 2, 2023 Share Posted January 2, 2023 9 minutes ago, Marvin said: We require (but for us the figures may be different from others) about 500kWh for the winter When it comes to lossless energy storage you can't do much better than bunch of rocks minding their own business. It takes approx. 50,000 Joules to lift 1000 kg 5 meters (roughly 14kWh) so around 35 tons to see you through the winter. 1 Link to comment Share on other sites More sharing options...
Roger440 Posted January 2, 2023 Share Posted January 2, 2023 2 minutes ago, Radian said: When it comes to lossless energy storage you can't do much better than bunch of rocks minding their own business. It takes approx. 50,000 Joules to lift 1000 kg 5 meters (roughly 14kWh) so around 35 tons to see you through the winter. Or 535 tons for my house. Not an entirely practical idea out in the real worl i think..................... 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted January 2, 2023 Share Posted January 2, 2023 2 minutes ago, Radian said: It takes approx MGH Where: M = mass in kg G = gravity 9.81 m/s2 H = height in metres Easy Peasy. Nothing to stop you pumping water up high. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 2, 2023 Share Posted January 2, 2023 (edited) 8 minutes ago, Roger440 said: complication = unreliability It's plumbing, only made complicated by plumbers. Edited January 2, 2023 by SteamyTea Link to comment Share on other sites More sharing options...
Roger440 Posted January 2, 2023 Share Posted January 2, 2023 4 minutes ago, SteamyTea said: It's plumbing, only made complicated by plumbers. But in this sceanrio, water needs diverting, that means valves. And that means valve control. Which means sensors and electronics. Electronics = unreliability. And a level of understanding to fix when it goes wrong that i dont possess. Back to where we started. Would need a passive divertor system as each tank reaches max temp. Something with a waxstat. More research required....... Link to comment Share on other sites More sharing options...
SteamyTea Posted January 2, 2023 Share Posted January 2, 2023 6 minutes ago, Roger440 said: Something with a waxstat. Thermosyphon, big fat pipes and no valves. Heat the lower cylinder first, then it rises to the other ones. With a bit of luck you will get reassuring gurgling sounds. Link to comment Share on other sites More sharing options...
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