SteamyTea Posted January 4, 2022 Share Posted January 4, 2022 27 minutes ago, CotswoldDoItUpper said: Silly question perhaps, but given that the cost of e7 is so much lower, would it be worth just buying some batteries, fully charging them on e7 and using that during the expensive times of the day? Wouldn’t that work out more effective then solar panels during the over production in the summer and under production in the winter? Thought of that, but my day usage is less than 2 kWh, 50p a day. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 4, 2022 Share Posted January 4, 2022 How much does your car take in a usual week? Link to comment Share on other sites More sharing options...
CotswoldDoItUpper Posted January 5, 2022 Author Share Posted January 5, 2022 19 hours ago, SteamyTea said: How much does your car take in a usual week? About 80kWh ish. 140kWh ish on house lighting/appliances/cooling etc. heating/DHW done by lpg combi. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 5, 2022 Share Posted January 5, 2022 34 minutes ago, CotswoldDoItUpper said: 140kWh ish on house lighting/appliances/cooling etc. That seems quite high to me. My daytime usage is sub 15 kWh a week. That would only go up slightly if there were more people in house. Link to comment Share on other sites More sharing options...
epsilonGreedy Posted January 5, 2022 Share Posted January 5, 2022 On 04/01/2022 at 15:57, CotswoldDoItUpper said: YI’d need about a 35kWh battery I guess. Any idea how much they cost? £7k to £9k. You would be looking at about 100 car size batteries or 40 huge two men to lift lorry size jobbies. Then add in the cost of building an extension to house these plus elevated insurance to cover the risk of explosive hydrogen venting off. Finally consider that this large bank of lead acid batteries would be exhausted after 3 years of deep discharge cycling. You could go lithium but now we are talking £30k, £50k or more. Link to comment Share on other sites More sharing options...
TonyT Posted January 5, 2022 Share Posted January 5, 2022 https://www.ebay.co.uk/itm/223639790102 you can buy them cheaper, so lots cheaper than £30,£50K Link to comment Share on other sites More sharing options...
CotswoldDoItUpper Posted January 6, 2022 Author Share Posted January 6, 2022 Ok so if I wanted to do this I would need I guess 5 of those lithium batteries (£6750+installation). Saving about £1250/year for about a 5 1/2-6yr payback, faster as £/kWh increase. Could I get a decent size solar array any not connect it to the main grid, just to the batteries/EVs and not have to inform DNO as it wouldn’t be connected to the grid? Or would I have to inform them of batteries anyway as they would be connected to the grid to power the house? Link to comment Share on other sites More sharing options...
joth Posted January 6, 2022 Share Posted January 6, 2022 12 hours ago, epsilonGreedy said: On 04/01/2022 at 15:57, CotswoldDoItUpper said: YI’d need about a 35kWh battery I guess. Any idea how much they cost? £7k to £9k. Do you have any link to a supplier for that? Most the systems I've seen designed for home install are just under 1£ per Wh, e.g. about £9000 for a 13.5kWh powerwall. So it'd be circa £27,000 to get (just over) 35kWh of storage the Tesla way. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 6, 2022 Share Posted January 6, 2022 (edited) 9 minutes ago, CotswoldDoItUpper said: Could I get a decent size solar array any not connect it to the main grid, just to the batteries/EVs and not have to inform DNO as it wouldn’t be connected to the grid? Yes, you can get what they call 'islanding' systems, and purely stand alone systems. How would you switch between your stored energy and grid energy for when you need extra power that the PV/battery system cannot supply i.e. 3 to 4 months in the winter. You also, when it come to calculating the cost, need to put a price on lost generation i.e. system losses, unused generation potential. Edited January 6, 2022 by SteamyTea Link to comment Share on other sites More sharing options...
epsilonGreedy Posted January 6, 2022 Share Posted January 6, 2022 (edited) 1 hour ago, joth said: Do you have any link to a supplier for that? No. I was using my previous experience of living on boats and being dependent on lead acid batteries. I hoped the later sentence, that you did not quote, highlighted the futility of running a home on battery power whens mains power is available. Long term liveaboard sailors are moving over to Lithium battery banks but these cost way more as you indicated. These sailors tend to cruise in tropical latitudes with PV arrays of 400w to 1000w. Their offgrid lives are sustainable with induction cooker hobs, washing machines, water makers and 12v lighting, however their daily energy consumption is much lower than a northern latitude house. Some of these sailors find PV+Lithium is enough and eventually ditch their onboard diesel genset but they always have the main yacht engine available to top up the battery bank on difficult days. Edited January 6, 2022 by epsilonGreedy 1 Link to comment Share on other sites More sharing options...
ProDave Posted January 6, 2022 Share Posted January 6, 2022 Does someone make a system where you have a large, say 10kWp solar PV array, connected to batteries, then an inverter, with the inverter output limited to 3.68kW? That would allow the over sized array to charge the batteries during the day and discharge over a longer period at the maximum G98 rate, thus allowing a larger array to be (loosely) grid connected. 1 Link to comment Share on other sites More sharing options...
epsilonGreedy Posted January 6, 2022 Share Posted January 6, 2022 12 hours ago, TonyT said: https://www.ebay.co.uk/itm/223639790102 you can buy them cheaper, so lots cheaper than £30,£50K The 3.5kw product you quote is a suspiciously small package for the claimed capacity, I note they claim to have developed their own variation of the lithium battery compound. This leads to two possibilities, either you have revealed the breaking wave of a new generation of battery technology or you have linked to some eBay snake oil merchant. The following lithium battery review gives a better indication of the cost of mainstream lithium batteries. https://www.pbo.co.uk/gear/lithium-batteries-for-boats-reviewed-12-of-the-best-lithium-boat-batteries-tested-62244 Link to comment Share on other sites More sharing options...
epsilonGreedy Posted January 6, 2022 Share Posted January 6, 2022 3 minutes ago, ProDave said: Does someone make a system where you have a large, say 10kWp solar PV array, connected to batteries, then an inverter, with the inverter output limited to 3.68kW? That would allow the over sized array to charge the batteries during the day and discharge over a longer period at the maximum G98 rate, thus allowing a larger array to be (loosely) grid connected. I have had long chats with my new self build neigbour who ran a renewables installation business for years. He tried to apply your logic for large PV installtions but the local DNO would decline such applications on the basis that the power limiting device might fail and whallop their local power lines with too much energy. Link to comment Share on other sites More sharing options...
ProDave Posted January 6, 2022 Share Posted January 6, 2022 5 minutes ago, epsilonGreedy said: I have had long chats with my new self build neigbour who ran a renewables installation business for years. He tried to apply your logic for large PV installtions but the local DNO would decline such applications on the basis that the power limiting device might fail and whallop their local power lines with too much energy. That is just stupid DNO logic that an inverter designed for 3.68kW output could produce 10kW output. It might for a few seconds before going bang. Even a simple 16A circuit breaker in the output would trip if it exceeded 3.68kW by much. Funny how they accept circuit breakers to stop you drawing too much from the grid, but would not accept such a proven reliable device to stop you exporting too much. Something needs to change to allow more schemes like that to actually happen. 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted January 6, 2022 Share Posted January 6, 2022 10 minutes ago, ProDave said: Does someone make a system where you have a large, say 10kWp solar PV array, connected to batteries, then an inverter, with the inverter output limited to 3.68kW? You would need a BMS, hopefully with MPPT to charge the batteries. Is there any reason to just spur off the DC side, before the inverter, to a BMS. Not sure how the load sharing will work, but if the BMS takes less load than the inverter, then charging is reduced, and visa versa. You can also tap of at a more suitable voltage for the BMS. Don't think they like 600V+. Link to comment Share on other sites More sharing options...
epsilonGreedy Posted January 6, 2022 Share Posted January 6, 2022 1 minute ago, ProDave said: That is just stupid DNO logic that an inverter designed for 3.68kW output could produce 10kW output. It might for a few seconds before going bang. My neighbour would enjoy sharing his views and frustration with you on this subject. He is building a fascinating semi underground off grid house with polystyrene blocks imported from Norway. Link to comment Share on other sites More sharing options...
CotswoldDoItUpper Posted January 6, 2022 Author Share Posted January 6, 2022 30 minutes ago, ProDave said: Does someone make a system where you have a large, say 10kWp solar PV array, connected to batteries, then an inverter, with the inverter output limited to 3.68kW? That would allow the over sized array to charge the batteries during the day and discharge over a longer period at the maximum G98 rate, thus allowing a larger array to be (loosely) grid connected. This is exactly the sort of set up I had in mind, just couldn’t put it into words… thanks @ProDave! seems very sensible and should be able to be made safe via fuses and would solve a lot of issues people have with PV! Link to comment Share on other sites More sharing options...
ProDave Posted January 6, 2022 Share Posted January 6, 2022 1 minute ago, CotswoldDoItUpper said: seems very sensible and should be able to be made safe via fuses and would solve a lot of issues people have with PV! Yes and it seems from a few posts above that the DNO's have said a big fat no to such a system. Great shame. Well that explains why you don't see such a system for sale anywhere. Link to comment Share on other sites More sharing options...
joe90 Posted January 6, 2022 Share Posted January 6, 2022 (edited) 8 minutes ago, ProDave said: the DNO's have said a big fat no to such a system. Could you not fit a 4Kw system then add panels afterwards ? and as @ProDave says protect the grid with a simple breaker ? Edited January 6, 2022 by joe90 Link to comment Share on other sites More sharing options...
ProDave Posted January 6, 2022 Share Posted January 6, 2022 2 minutes ago, joe90 said: Could you not fit a 4Kw system then add panels afterwards ? and as @ProDave says protect the grid with a simple breaker ? I wonder what the penalty is for having a non compliant system connected? It it was just being instructed to disconnect it immediately one might take a risk? If there was some more substantial penalty it might not be worth trying. Anyone care to look that up? 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted January 6, 2022 Share Posted January 6, 2022 3 minutes ago, ProDave said: Well that explains why you don't see such a system for sale anywhere. I suspect that the DNOs have to look at a much bigger picture. If there proportion of micro generation gets too large, grid stability issues may arise. I suspect that the 16A per phase is vert much on the safe side. Would be a worry if on a scattered cloud day an extra MW of poorly unregulated PV caused a 3 GW nuclear power station to go off line. We saw what two independent faults did in August 2019. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 6, 2022 Share Posted January 6, 2022 (edited) 5 minutes ago, joe90 said: 4Kw No, now wash your mouth out with soap. Edited January 6, 2022 by SteamyTea 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted January 6, 2022 Share Posted January 6, 2022 2 minutes ago, ProDave said: I wonder what the penalty is for having a non compliant system connected? It it was just being instructed to disconnect it immediately one might take a risk? If there was some more substantial penalty it might not be worth trying. Anyone care to look that up? We may find out as someone on here DIYed and failled to notify their DNO. 1 Link to comment Share on other sites More sharing options...
joe90 Posted January 6, 2022 Share Posted January 6, 2022 4 minutes ago, SteamyTea said: No, now wash your mouth out with soap. Sorry sir, I did put 4kW but spell check changed it without me noticing ? Link to comment Share on other sites More sharing options...
SteamyTea Posted January 6, 2022 Share Posted January 6, 2022 4 minutes ago, joe90 said: Sorry sir, I did put 4kW but spell check changed it without me noticing ? OK. The title of the thread becomes more appropriate. Link to comment Share on other sites More sharing options...
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