Off-Grid Solar Powered Hostel - Colombia

[La Ponderosa Colombia]

Hello all,

I’m new to this forum as well as Solar Energy. I am in the process of designing & building an off-grid hostel on the north coast of Colombia which is in a remote location with a lot of open space ideal for solar panels.

I’m planning to open with a capacity of 20-30 people with a view to expand in the future. I have been calculating the predicted daily kWh consumption, I’ve decided to power the oven/stoves/grill with gas as these are high consumers of kw, we plan to create a bio-digester to create our own gas down the line. My daily kWh predictions are:

Total: 25.2 kWh
Consumption during daylight: 12.2 kWh
Consumption during the night (battery): 13 kWh

Given 13 kWh capacity with batteries is expensive I’m considering powering the security system and fridges/freezers with their own small solar set ups. Excluding these, this would take the daily kWh consumption to:

Total: 16.6 kWh
Consumption during daylight: 9.4 kWh
Consumption during the night (battery): 7.2 kWh

The system I am planning is:

5 kw 48v MPP Inverter/controller
5 kw total of panels
6 24v 50amp Battle Born LiFePo4 batteries (7.2kw)

With 7.5 hours a day of sunlight, 5kw system, 80% efficiency, this should give 30 kWh a day.

I believe the kWh consumption in the night sometimes will be higher than my prediction. This would be greater than the 7.2kw battery capacity. To start with I don’t want to add an additional 24v 50amp battery due to the cost. I have a 5.5kw generator which I’ll use before I install a solar set up and I’ll use as a back up. The generator has an ‘Automatic Transfer Switch’ which connects to the grid. When the grid fails (in this region its a lot) it automatically connects to the generator. My thought is that in this instance the ‘grid’ would in fact be the solar set up. I plan to connect the generator to the inverter as in the diagram below. I have a few questions for this connection/series of events. I see it as follows:

1. Solar Panels provide power to the AC Output & batteries
2. In the night the batteries will power the AC Output
3. In an event the consumption is >7.2kw battery capacity, the battery discharges and the battery voltage drops to low DC warning voltage or setting point
4. Either the stopping of the power from the battery triggers the ‘Automatic Transfer Switch’ on the generator and this turns on, or the MPP Inverter switches to the generator (I need to confirm if the inverter and generator are compatible to automatically make this switch or if it will be manual)
5. Generator charges the batteries & AC output
6. Is there a setting on the MPP Inverter which when the batteries are fully charged from the generator, the generator is turned off and the AC output switches back to being powered by the batteries?

I’d appreciate some advice, on the following:

1. From your experience, does this general set up/calculations sound accurate?
2. What level of discharge is advisable for LiFePo4 batteries?
3. Does the generator automatically turn on when the batteries are low or does this need to be manual?
4. When does the MPP inverter switch back to using the charged batteries rather than the generator?
5. Does anyone have advice/experience with solar power fridges/freezers & security cameras?
6. We have a large site, is it an issue that the MPP inverter could be 200 meters from the majority of the solar panels & some appliances using the AC Output will be 200 meters from the MMP Inverter?

Thanks!

 

[kernel]

Hello all,

I’m new to this forum as well as Solar Energy. I am in the process of designing & building an off-grid hostel on the north coast of Colombia which is in a remote location with a lot of open space ideal for solar panels.

I’m planning to open with a capacity of 20-30 people with a view to expand in the future. I have been calculating the predicted daily kWh consumption, I’ve decided to power the oven/stoves/grill with gas as these are high consumers of kw, we plan to create a bio-digester to create our own gas down the line. My daily kWh predictions are:

Total: 25.2 kWh
Consumption during daylight: 12.2 kWh
Consumption during the night (battery): 13 kWh

Given 13 kWh capacity with batteries is expensive I’m considering powering the security system and fridges/freezers with their own small solar set ups. Excluding these, this would take the daily kWh consumption to:

Total: 16.6 kWh
Consumption during daylight: 9.4 kWh
Consumption during the night (battery): 7.2 kWh

The system I am planning is:

5 kw 48v MPP Inverter/controller
5 kw total of panels
6 24v 50amp Battle Born LiFePo4 batteries (7.2kw)

With 7.5 hours a day of sunlight, 5kw system, 80% efficiency, this should give 30 kWh a day.

I believe the kWh consumption in the night sometimes will be higher than my prediction. This would be greater than the 7.2kw battery capacity. To start with I don’t want to add an additional 24v 50amp battery due to the cost. I have a 5.5kw generator which I’ll use before I install a solar set up and I’ll use as a back up. The generator has an ‘Automatic Transfer Switch’ which connects to the grid. When the grid fails (in this region its a lot) it automatically connects to the generator. My thought is that in this instance the ‘grid’ would in fact be the solar set up. I plan to connect the generator to the inverter as in the diagram below. I have a few questions for this connection/series of events. I see it as follows:

View attachment 8291

1. Solar Panels provide power to the AC Output & batteries
2. In the night the batteries will power the AC Output
3. In an event the consumption is >7.2kw battery capacity, the battery discharges and the battery voltage drops to low DC warning voltage or setting point
4. Either the stopping of the power from the battery triggers the ‘Automatic Transfer Switch’ on the generator and this turns on, or the MPP Inverter switches to the generator (I need to confirm if the inverter and generator are compatible to automatically make this switch or if it will be manual)
5. Generator charges the batteries & AC output
6. Is there a setting on the MPP Inverter which when the batteries are fully charged from the generator, the generator is turned off and the AC output switches back to being powered by the batteries?

I’d appreciate some advice, on the following:

1. From your experience, does this general set up/calculations sound accurate?
2. What level of discharge is advisable for LiFePo4 batteries?
3. Does the generator automatically turn on when the batteries are low or does this need to be manual?
4. When does the MPP inverter switch back to using the charged batteries rather than the generator?
5. Does anyone have advice/experience with solar power fridges/freezers & security cameras?
6. We have a large site, is it an issue that the MPP inverter could be 200 meters from the majority of the solar panels & some appliances using the AC Output will be 200 meters from the MMP Inverter?

Thanks!

At those distances, i would adopt high voltage dc pv home runs. 400V-500V operating strings..

 

[La Ponderosa Colombia]

At those distances, i would adopt high voltage dc pv home runs. 400V-500V operating strings..

and this would be done using transformers? would you recommend using a LG Chem Resu 10H 400v battery?

 

[jasonhc73]

and this would be done using transformers? would you recommend using a LG Chem Resu 10H 400v battery?

Voltage drop is not that big of an issue as it sounds.

Were talking about 9% at 200 meters.

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

MPP Solar does make high and low voltage inverters. Do you want 240V split phase? (US style electricity)
Keep in mind that 5K MPP Solar is total output, that means only 2.5K per leg/phase.

 

[La Ponderosa Colombia]

Voltage drop is not that big of an issue as it sounds.

Were talking about 9% at 200 meters.

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

MPP Solar does make high and low voltage inverters. Do you want 240V split phase? (US style electricity)
Keep in mind that 5K MPP Solar is total output, that means only 2.5K per leg/phase.

The local power here is 110v single phase, Im happy to keep this system the same

9% is at 220ft I believe, 220m looks to be a 30% drop. If this is the case then Id assume a high voltage inverter would be the best solution, 500v would have a 6.6% drop over 200 meters

 

[jasonhc73]

The local power here is 110v single phase, Im happy to keep this system the same

9% is at 220ft I believe, 220m looks to be a 30% drop. If this is the case then Id assume a high voltage inverter would be the best solution, 500v would have a 6.6% drop over 200 meters

Bigger wires! 6 awg is 20% at 220 "METERS" (stupid Mericans and their big feet ?).
Or even 4 awg if available.

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

 

[kernel]

Yes, im not sure of the max pv input of an mpp unit..... or if it has two pv inputs or if they can be bridged...

But assuming 150v max pv 120v ac power output and one or two pv circuits 120vdc home or 120vac all the way home from the array location and 200 meter /650'

Dude, you need #2 (2xpv) or 2/0 copper conductors to get there. These sizes could translate to a split phase 220? Dont have any idea how power is transmitted there. If it is delivered at 110vac, yes, 2/0 if the inverter is located at the array.

This brings up the question of the relationship of the other sources in the microgrid. Where is the utility drop? Generator, etc....

I would use high voltage dc and a good international inverter/charger with a grid and generator input. The mpp may well be it, gonna take big wire. You could bypass its charger or break into more strings...... i like to keep it as big and few as is practical.

This could all go away if you run home at 420vdc to 520vdc on #8 copper!!

 

[kernel]

Yes, im not sure of the max pv input of an mpp unit..... or if it has two pv inputs or if they can be bridged...

But assuming 150v max pv 120v ac power output and one or two pv circuits 120vdc home or 120vac all the way home from the array location and 200 meter /650'

Dude, you need #2 (2xpv) or 2/0 copper conductors to get there. These sizes could translate to a split phase 220? Dont have any idea how power is transmitted there. If it is delivered at 110vac, yes, 2/0 if the inverter is located at the array.

This brings up the question of the relationship of the other sources in the microgrid. Where is the utility drop? Generator, etc....

I would use high voltage dc and a good international inverter/charger with a grid and generator input. The mpp may well be it, gonna take big wire. You could bypass its charger or break into more strings...... i like to keep it as big and few as is practical.

This could all go away if you run home at 420vdc to 520vdc on #8 copper!!

And at 1.6 - 2% loss.

 

[La Ponderosa Colombia]

And at 1.6 - 2% loss.

Cheers for the advice. As mentioned I’m a novice with solar so Im still getting my head around the terminology. I’m also product & system config agnostic, I'm all ears for advice on inverters/batteries etc.

I’ve drawn up a very basic diagram of the system using your inputs, I’d like to put some panels on the roof of the house and the rest 100m away. Here are some of the specs:

• AC output of inverters are single phase 230v
• No utility input, completely off-grid
• Issue with the voltage drop for AC Output to bar
• Less voltage drop on DC input using higher voltage, requires high voltage inverter

Another option is to have 2 systems, put solar panels near the bar with own inverter & batteries. Then all of the panels for the house could potentially fit on the roof.

Pros: No need for high-voltage inverter, less money spent on wires
Cons: Need to buy/manage 2 systems (more money spent on 2x inverters?) generator would need 300m cable to provide back up to bar (could move the generator in between bar & house but not ideal due to noise), can a generator be set up to automatically back up both systems?

From doing this exercise now Im thinking 2 separate set ups would make more sense?

 

[kernel]

There you go! Wire makes a difference. Power is nice..... its gotta get there.

 

[jasonhc73]

Cheers for the advice. As mentioned I’m a novice with solar so Im still getting my head around the terminology. I’m also product & system config agnostic, I'm all ears for advice on inverters/batteries etc.

I’ve drawn up a very basic diagram of the system using your inputs, I’d like to put some panels on the roof of the house and the rest 100m away. Here are some of the specs:

View attachment 8382

• AC output of inverters are single phase 230v
• No utility input, completely off-grid
• Issue with the voltage drop for AC Output to bar
• Less voltage drop on DC input using higher voltage, requires high voltage inverter

Another option is to have 2 systems, put solar panels near the bar with own inverter & batteries. Then all of the panels for the house could potentially fit on the roof.

Pros: No need for high-voltage inverter, less money spent on wires
Cons: Need to buy/manage 2 systems (more money spent on 2x inverters?) generator would need 300m cable to provide back up to bar (could move the generator in between bar & house but not ideal due to noise), can a generator be set up to automatically back up both systems?

From doing this exercise now I'm thinking 2 separate setups would make more sense?

Now you are no longer in a Technical debate, but a Financial debate.

Does the cost of the two systems beat the cost of wire?
Transformers of good long term use(basically utility grade, and new) are about a $1000 on each end. If you can find them, real utility transformers, and can handle way more than little 1000v transformers we mear DIYers play with.

Be mindful that MPP Solar has many different off-grid solutions, if you get a 230V(This gives a 230V and a Neutral), that is different than a Split Phase 240V(This gives you 2 120V and a Neutral). They also offer simple single-phase 120V systems. They even have several 230V systems that offer batteryless operation.