wexfordman2 wrote: » The only thing is, the way the front works, is if you want a 4kwp system the grant requires the battery, so if the battery costs you 5k, the actual cost to you is 2,600 idlf you discount the additional 2,400 in grant money you will get.
KCross wrote: » From analysis of my own consumption a battery makes no financial sense and I'm a high user of electicity. The payback is, imo, 15yrs+ Thats just too long to be a sensible buy. The quotes you get will talk about 7yr paybacks but they are generally rubbish claims as they use standard rate electricity for the calculations and they assume 100% utilisation of the energy by diverting to hot water which is skewing their figures to make it look better than it is. The figure you should be using to calculate your payback should be the night rate of 8c/kWh unless the battery is displacing something that cant be moved to night rate (background load, cooking etc). And when calculating the day rate it should use the discounted rate that everyone can avail of which is around 17c/kWh right now, not the 20-22kWh that the SolarPV providers use in their calculations..... add it all up and the payback will be 15yrs+, not 7.... at least thats what fell out the bottom of my spreadsheet anyway.... YMMV. By the time it has just paid for itself it will be very old tech, degraded and you are then crossing all your fingers that it will last another 10yrs to give you a payback. If anything goes wrong like a failed inverter (which does happen) your TCO is completely shot. It just doesnt make sense, imo. The payback needs to be <10yrs, preferably 5 to make it a sensible investment. There is also the distinct possibility that there will be a Feed-in-tariff in the next 10yrs which will cost ALOT less than battery tech and is much more usable and scalable and you're not worrying about battery degradation etc. If you have stumped up for a battery and then a FiT comes in you will have wasted your investment, imo. I know others on here believe in drawing the grant. I think its foolhardy. Decide for yourself but definitely run the numbers for your house and see what you get.
KCross wrote: » You are correct, thats how the grant system works. The payback is very long (15yrs+) even with the grant. Prior to the grant it was even longer, obviously.
wexfordman2 wrote: » Can't see it taking 15yrs. If you take even an assumption without pv and just using it as a night save device. Charge battery overnight, 5kwh at 8c per kwh, is 40c Discharge during the day, at 18c per kwh, and you save 50c per day, 3.50 per week or 182 euro per year, which is approx 15 year payback. That's without solar pv being used to charge the battery.
KCross wrote: » You're assuming that you will be able to fully charge and discharge the battery every day of the year which is a gross over-estimation/simplification. A 4kWp system today in Ireland would have generated less than 2kWh and most likely all of that would have been used by the house background load and nothing to the battery. How are you then going to manage the system to tell it to be a night saver device tonight but be an excess storage device tomorrow.... you'd need to be sitting on weather forcecasts and second guessing your generation continuously.... its not a viable way, imo, to use the system. It needs to be plug 'n play. Unless you have found an inverter with some super smart controls that I havent seen. If you have run the numbers for your own house and you are confident it works for you then great, I wish you the best with it. I just dont see it myself and I based my calculations on real world weekly figures from Solar PV systems installed in Ireland (they are publicly available stats) and I modelled it on a monthly basis with my house consumption along with the quotes I got.... it just didnt stack up and certainly didnt give anywhere near the payback time I was comfortable with. Even if my figures were out 20% it was still too long a payback. SolarPV on its own (no battery) just about makes sense but I'm trying to do a more direct labour route to reduce the ROI time further.... not sure yet if it will work out since you have to forego the grant in this scenario..... still working on it though, just need a spark now that I can trust and willing to do it.
wexfordman2 wrote: » The figures i have though were based on not using and solar pv, just charging during night to avail of low rate. What I was trying to show was that even the battery in it's own, at 2,600 would take less than the 15yrs payback you mentioned. As far as telling the system when to charge, i would think the smarts are not too much of a challenge. I mean, you charge it by the cheapest rate electricity available to you. A) excess solar night rate
Brecken Tart Newscast wrote: » Is that what you've done?
wexfordman2 wrote: » Install not finished yet, but I have night rate and the system will be tuned to utilise night rate and solar.
wexfordman2 wrote: » The figures i have though were based on not using and solar pv, just charging during night to avail of low rate. What I was trying to show was that even the battery in it's own, at 2,600 would take less than the 15yrs payback you mentioned.
wexfordman2 wrote: » As far as telling the system when to charge, i would think the smarts are not too much of a challenge. I mean, you charge it by the cheapest rate electricity available to you. A) excess solar night rate
KCross wrote: » How are you then going to manage the system to tell it to be a night saver device tonight but be an excess storage device tomorrow.... you'd need to be sitting on weather forcecasts and second guessing your generation continuously.... its not a viable way, imo, to use the system. It needs to be plug 'n play. Unless you have found an inverter with some super smart controls that I havent seen.
_dof_ wrote: » I think the Moixa does just that, looks like some pretty cool tech. Don't know if it's available in Ireland though.
air wrote: » Your assertion here that it is possible to simultaneously import and export to the grid just highlights that you have little to no understanding of the subject at hand.
air wrote: » In the situation outlined, (5kw production, 5kW load, 3.6kW inverter) the PV will provide 3.6kW to the load via the inverter and the remainder of 1.4kW will be imported from the grid.
KCross wrote: » If it was possible to get a 5kW inverter at the same cost and same efficiency as a 3kW inverter then of course you would buy it but clearly thats not the case. There is a cost.
unkel wrote: » Reading back what I posted about importing and exporting at the same time and indeed it makes no sense. I apologise
unkel wrote: » It makes no sense to me that you have to import from the grid at the high day rate while your battery is full
unkel wrote: » I maintain my position that a hybrid inverter of 3.6kW is too small for a 5kwp array + 6kWh battery
KCross wrote: » Thanks, that says it takes weather input... We’ll explain the “SMART” element of our solar energy service. Using machine learning, it utilises inputs from the weather and your energy usage patterns to create an optimal plan for your battery. However I dont think its in realtime or at least I cant see that from their website. Its something that is calculated by them and they advise you how to configure the system. Its still "hardcoded". I might fire them an email and confirm. And as you said, doesnt look like its in Ireland anyway.
air wrote: » The negligible cost difference you have listed goes a long way towards justifying the larger inverter especially if the purchaser has a mind to expand the PV array down the line.
Brecken Tart Newscast wrote: » Are they doing this for you? Is it in the price you quoted?
KCross wrote: » Yea, I understood your point. I'm pointing out that you wont get a full charge/discharge cycle every day with SolarPV, so your example doesnt really tell you anything. Maybe not that much of a challenge if the inverter is connected to the net and is reading forecasts or something but the reality is that the inverters, AFAIK, dont do anything like that. So, the reality is you would have to do the following each day... - check forecast for tomorrow - decide if there will be excess generation from your system or not. - calculate if that excess is enough to justify not charging the battery on night saver or maybe only half or quarter charging it etc. - Make the necessary changes to the system (if it even allows you to) for the next day. - repeat each day. Its not viable really to do it manually. It would have to be automated. If you are aware of an inverter that has that capability I'd like to hear about it and I'll recalculate myself. I believe the system will be setup to behave in one particular way and thats it. You wont get a full charge/discharge cycle out of it 365 days and thats the key point.
wexfordman2 wrote: » Sorry kc, but you are.missing the point. Fristly, you referred to a 15yr payback in a solar with battery, I queried that showing a payback of 15yrs for a battery system that is purely for night rate charging. So my point was, that if there is a 15yr payback in battery alone, then a battery with solar pv would have a greater payback. Secondly, most inverters are connected online now, and do provide the features you are talking about. The one I am getting iantalled will do just that.
_dof_ wrote: » I had heard the CEO of Moixa discussing it in an interview and my understanding was that it was all automatic, the smart controller learned your usage patterns and took the weather forecast and your usage patterns into account to automatically adjust the charging and of the battery to maximize usage of the PV and minimize import of the grid at high rate and minimize the export to the grid (assuming no FIT). So, if it knew that it would be cloudy tomorrow and had learned that your PV installation would only generate a small amount, it would charge the battery from the grid overnight to nearly full, but if it was forecast to be sunny tomorrow and your usage pattern showed that the PV wouldn't cover the first couple of hours of demand, then the battery would be charged just enough overnight to cover that shortfall, based on the prediction that the PV would generate enough to cover the house demand and charge the battery for the rest of the day. But I could be wrong. If you get more details from them, please do share.
KCross wrote: » I understand your point fine and I've explained already the logic to why that example doesnt stack up unless the system is automatically adjusting itself on a daily basis in advance based on weather forecasts. Does your inverter do that? If yes, as I already said, I'd like to know exactly what inverter that is, so I can research it for myself. If it doesnt auto adjust based on forecasts you wont get a full charge/discharge cycle every day. The one _dof_ posted sounds promising but any of the inverters I was quoted for did not have the ability to auto adjust each day like that. I'd be surprised if yours does but please do detail what one you are getting so we can all learn.
wexfordman2 wrote: » My inverter installers next Mondayhttp://primehybridenergy.com/downloads/prime_brochure_july_17.pdf
unkel wrote: » No EN50438 cert? That's interesting from a SEAI approved Solar PV installer.
Brecken Tart Newscast wrote: » Just to add to the debate - opinions appreciated - here's the spec i was offered. Is it good/bad or indifferent? Remember I was offered a smaller inverter/ less panels than wexfordman for the same money. I've to talk to him about that still but would like some feedback....wexford - how does the equipment compare to yours ? Project Overview Figure: Overview Image, 3D Design PV System 3D, Grid-connected PV System PV Generator Output 4.55 kWp PV Generator Surface 23.6 m² Number of PV Modules 14 Number of Inverters 1The yield PV Generator Energy (AC grid) 3,211kWh Grid Feed-in 3,211 kWh Down-regulation at Feed-in Point 0 kWh Own Power Consumption 0.0 % Solar Fraction 0.0 % Spec. Annual Yield 705.81 kWh/kWp Performance Ratio (PR) 88.3 % Yield Reduction due to Shading 0.0 %/year CO₂ Emissions avoided 1,92 System Data Type of System3D, Grid-connected PV SystemSimulation model used: - Diffuse Irradiation onto Horizontal Plane - Hofmann - Irradiance onto tilted surface - Hay & DaviesModule Areas x 2 (east & west) 1. Module Area - Building 01-Roof Area East PV Generator, 1. Module Area - Building 01-Roof Area East Name Building 01-Roof Area East PV Modules 7 x Q.PEAK DUO-G5 325 Rev1 Manufacturer Hanwha Q.CELLS Inclination 35 ° Orientation East 90 ° Installation Type Roof parallel PV Generator Surface 11.8 m²Inverter configuration Configuration 1 Module Areas Building 01-Roof Area East + Building 01-Roof Area West Inverter 1 Manufacturer SOLTARO Model SOLTARO HYPER-3680 Quantity 1 Sizing Factor 123.6 % Configuration MPP 1: 1 x 7 /MPP 2: 1 x 7Simulation Results Results Total System PV System PV Generator Output 4.6 kWp Spec. Annual Yield 705.81 kWh/kWp Performance Ratio (PR) 88.3 % Yield Reduction due to Shading 0.0 %/year Grid Feed-in 3,211 kWh/year Grid Feed-in in the first year (incl. module degradation) 3,211 kWh/year Standby Consumption (Inverter) 48 kWh/year CO₂ Emissions avoided 1,927 kg / year
wexfordman2 wrote: » I would def query the inverter size, it may be an error . My system was 18 panels, in the one south facing roof, so the yeild figures for yourself will be quite different as you are in two different roofs and not south facing. I wonder, if the lower inverter size is perhaps because you may not get the full yeild if you are not as well orientated. If it is the 3.6kw inverter and you are going for less panles (14) than mine there is def room for him to improve.the price. What make of inverter and battery did he spec?
GaryCocs wrote: » Hi Guys, Bit nervous now about the panels based on angles, roof size etc.https://www.dropbox.com/s/zu8nj4p780fzqaz/Screenshot%202018-11-13%2012.24.49.png?dl=0 Two roofs. Bigger one: Approx 7.2m by 2.1m Roof is facing South by South East Velux in the middle that doesn't/won't open. Also have another roof that is South West (I slated myself and could be replaced entirely with panels if that is an option) Approx 5m x 2.4m 12 square metres. Angle isn't great on that one from my reading of the above. How many panels in total do you think I can get and am I mad
