building 15-30Kw system

[olaFin]

I have small company and it is possible get up to 40% subsidizes for making wind or solar. There are some terms like I have to use most energy on my company use and minimum amount of subsidies so I have to make it big.

  Typically people make just regular solar without backup and half of the use goes back to grid. 

 We have grid failures many times a year and I would like to build backup for these events and maybe even go offgrid someday!

 I have some experiense building enphase and also small offgrid victron solar systems for pumping water etc..

 I see alot of benefits using sbms with victron multiplus three phase setup with diy build big lifepo4 battery pack.

 I think this bigger system would be better in 48v and I would not need to buy 6 to 12 victron inverters, I also would like to keep things simple. 

  I would not like to build two separate systems but maybe one solution is to put half of the system after multiplus with microinverters.  What are  your thoughts about this kind of build and what size systems have you build by sbms?

 I could also build smaller solar and add wind power also but I dont have any experience with it and cannot find reasonable priced 4-10kw reliable wind turbines.

[Dacian Todea]

Small wind turbine are just useless compared with PV panels way to expensive. I will not waste the money on wind turbines.

The SBMS0 can measure max 750A so that is about 20kW max load with 24V battery and same for charging but in dual PV array mode you can have 10kW + 20kW so 30kW max PV array is possible that way.

In a grid connected system you will sure not want a battery. Not sure where you are that the grid is so bad to be down a few times a year. Also what is the cost per kWh from the grid ? is there any payment for the energy you send to grid ?

[olaFin]

This summer we have had two grid failures 3 days and  1 day + short brakes more often.

 Generators are expensive, need more maintenance and I need to run my business so I think this is best solution for me. I don´t necessary need full power but I think 20kwh battery would be enough. 

 My electricity bills are abt 500euros/month, 20c/kwh and none or very little payment for sent electricity. 

[Dacian Todea]

500euro/month sounds huge considering 20cent/kWh

Even if half of that amount is for the actual electricty that means at least 1200kWh/month.

I'm fully offgrid and I have a energy usage of 120kWh/month and for that I have a 4.5kWh battery and 8kW PV array.

If you are using 1200kWh/month that gets to an average per day of 40kWh so not sure how will just a 20kWh battery help especially with that 3 day grid failure.

A small generator costs almost nothing and can take the full load for a few days per year and it will be way more cost effective than adding a battery even a 20kWh one.

Each kWh from generator will cost the equivalent of one liter of fuel and say you have 6 full days in average per year of grid down at 40kWh average per day is 240kWh per year that is 240 liters of fuel per year say at 1.5euro/liter (no idea how much fuel is there) that is 360 euro per year in fuel x 10 years 3600 euro + the cost of the generator but even a quality one will not be that expensive. So maybe the generator + fuel for 10 year will be similar in cost with a 20kWh LiFePO4 battery but there is much more equipment that is needed like a large inverter or inverter charger.  If your grid in average is down for 6 days or more per year then you may as well just go fully offgrid as that is a saving of 60000euro and for that you can buy the equipment to generate the needed energy assuming you have the space for a huge PV array and the money to make the investment in that as is like paying all the electricity bills for the next 10 years today. 

[olaFin]

Generator is out of the question. Having autostart quality gen is +10K here and its not like good image for my business, and there is same amount of maintenance with using it one hour/ year or 100h/year.

 I rather use that money for multiple victron multiplus or similar and battery to use with crucial stuff that need to be running when we are not in property.

 We get 40% incentive for building solar system, including battery inverters etc. That is reason I am investing big now and anyway this is last year to apply this. I buy and install everything possible myself so my calculation for paying this back looks appealing. 

 Our ground heat pump is on almost done and thats going to cut more than half of cooling and warming expense. Our goal is to cut our electricity use more than half. Totally offgrid would be nice but not possible with only solar in this climate where 3 months of the year is almost zero solar, thats why asked for the wind.

 I have space for big solar system and small room to make clean install.

 I have small offgrid system that produced 939.9kwh 2018, 898.8kwh/ 2019. It has 4x 250w panels.  Easy to calculate what bigger system produces here.

[Dacian Todea]

How have you calculated that you used around 900kWh/year from those 4x250W panels ? That seems similar to what is possible in case of grid connected where all PV energy is used and not realistic offgrid usage.

I used to only have a 3x 240W PV array and was able to use 50 to 60kWh/month that is around 600 to 700kWh/year but I was utilizing the system fairly well with a lot of the energy used during the day for electric cooking.

A fully offgrid system will be designed for worst month. If space for PV array is not a limit then you should add as much as you can up to 0.9 of battery capacity so say you go with a 20kWh battery then you can install at 18kW PV array and only part of the panels will charge the battery depending on the amount of sun and you can use the excess directly for heating.

I fully heat my house using PV electricity directly and I do not need any cooling in summer as house is well designed and I'm in Canada Saskatchewan.

You are likely in a warmer place if a ground heat pump is used and that is just way to expensive in terms of cost amortisation it will never be a cost effective option.

To get some idea about the costs amortisation for a fully offgrid installation here are the numbers

PV panels have a cost amortisation as low as $0.02/kWh while best case LiFePO4 will have a cost amortisation an order of magnitude higher around $0.2/kWh. This is just the cost amortisation for this components there are inverters and other equipment that will add to the total cost.

[olaFin]

This not calculated. Its just from meter and every energy goes battery and heating water.

 I disagree heavily, Ground heat pump is only cost effective way in cold climate if you are not using wood and use alot of work. We have more than meter of snow and most coldest day last winter was -36c.  Three months literally no solar at all. My ground heat pump system that warms and cools my house 200m2 and my 300m2 workplace, and total cost was 10,5K eur. Cop is 5.5 and pays itself in 4 years compared to last owners oil + wood heating.  Ground heat pump solutions in many counties are old fashioned compared to here in Scandinavia. 

 Certainly my choice would be different if we could have solar year around.

 

[Dacian Todea]

I see so you divert excess energy to water heating.

I'm in a cold climate and my calculations show that direct PV solar heating is the most cost effective heating method about equal with natural gas here if you already have a connection.

-36C is also common here in winter and heating season is fairly long 5 to 6 months.

Solar is maybe a bit better here not sure of your exact location (guess somewhere in northern Europe).

I doubt real COP is anywhere near 5.5 more closer to 3.5 probably.

You can check my cost caluclations page 5 in this document http://electrodacus.com/DMPPT450/dmppt-presentation-v01.pdf

My house is much smaller 65m2 and very good thermal insulation. The house needs 1000kWh for heating in coldest month January with average temperature of -16.7C. You can check the average temperature details for my location here  https://en.climate-data.org/north-america/canada/saskatchewan/regina-373/  so you can compare with your location.

[olaFin]

Hi.  This tool gives me following info about kWh/m2/day.

 

  Measured in kWh/m²/day onto a solar panel set at a 10° angle:
(Optimal winter settings)

Jan	Feb	Mar	Apr	May	Jun
0.10	1.33	2.48	3.65	4.22	4.38
Jul	Aug	Sep	Oct	Nov	Dec
4.19	3.68	3.03	1.67	0.77	0.04

Measured in kWh/m²/day onto a solar panel set at a 40° angle:
(Optimal summer settings)

Jan	Feb	Mar	Apr	May	Jun
0.09	1.26	2.61	4.23	5.23	5.52
Jul	Aug	Sep	Oct	Nov	Dec
5.28	4.40	3.29	1.65	0.68	0.04

http://www.solarelectricityhandbook.com/solar-irradiance.html

Your area has alot more solar on winter time. 

 Anyways, I would like to build solarsystem with backup. Could I just build it with sbms0 , diy battery, 3 pcs (three phace) victron quatro or victron multiplus? 

 I dont get the full incentive if I use all the money on just panels+ inverter because its meant for my use and not intent to sell to grid. 

 

[Dacian Todea]

olaFin,

I do not think you mentioned what is your exact location or the closest city.

You can use this online tool for more details https://pvwatts.nrel.gov/  keep in mind when selecting the tilt angle it will be the other way around as on that website you mentioned so 10 degree there will correspond to 80 degree here.

But yes based on that data I do have way more solar energy in winter months here in Saskatchewan Canada.

Looks like complete darkness in December and January.