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Home » Solar Energy » Design 100W solar UPS with solar panel and batteries
Design 100W solar UPS with solar panel and batteries
Q:
I am looking to design 100W solar UPS for my customer. I am using 100W solar panel. I want to run this UPS for 6 hours. I want to run 100Watt load with this setup. Can anyone tell me the batteries required for setting up this system?
Actually this system will run one 80Watt fan and one 20 Watt Energy saver for 6 hours. Yes it will run the load 24/7 where solar will be primary source of charging and utility will charge batteries as secondary source of supply.
The load will run at 220VAC and 50Hz.
Solar panels will be located at roof top.
As sun shine in Pakistan is average approximately 10 hours so charging time for solar panel will be approximately 9 to 10 hours depending on good sunshine day.
Battery bank will be located inside house at 30 to 45 temperature.
Now please tell preferred type of battery (lithium, nickle, lead, mercury, etc.) and battery size (Ah), preferred voltage 12V or 24V for battery.
A:
At first glance I wonder why you would use a battery at all in this system. A 100W solar panel will only generate 100W while operating under standard test conditions (STC). STC is 1000W/m^2, as well as a number of other parameters. If, for example, the panel is receiving 500W/m^2 at any given moment it will only be producing 50W, assuming all other conditions are equal to STC. it is only when the radiation goes above 1000W/m^2 that the panel will be producing more than 100W, again assuming that everything else matches STC. As you say there is quite good sunshine in Pakistan but I had a quick look at free sources (http://www.nrel.gov/international/ra_pakistan.html) and it looks like it doesn't go above 7kWh/m^2 (at latitude tilt) anywhere across the country.
In practice it is unlikely that everything else will match STC, with the temperature being a key place where it is unlikely to match. Different types of modules respond differently to changes in temperature of the module (usually significantly higher than air temperature), but in general if the temperature is above 25°C the performance will be reduced. To run an AC load you will need an inverter, which will have inefficiencies. You will also have losses in cabling. You can spend a lot of money to minimize these inefficiencies but there will always be some level of loss.
Essentially what I am saying is that there will be very little time at which your panel will be producing enough to fully power the load, let alone have excess with which to charge a battery. This makes me think that to optimize the solar usage you are best of skipping the battery entirely, and simply running the system with a normal grid-tied inverter so that you are offsetting some of the power requirements during sunny times, and being powered entirely by the grid the rest of the time.
It may be that you have your own reason for wanting to use a battery though, for example there may be different prices for grid power at different times of day, or grid power may simply not be available at some times. Your mention of UPS makes me think it may be the latter, in which case we come back to the frequency of demand cycles and operating conditions.
I suggest you look at it as three different questions, the first being whether it is worth having solar for this system, the second being whether it is worth having a battery, and the third being whether there is any benefit in having the two combined as one system.
I am looking to design 100W solar UPS for my customer. I am using 100W solar panel. I want to run this UPS for 6 hours. I want to run 100Watt load with this setup. Can anyone tell me the batteries required for setting up this system?
Actually this system will run one 80Watt fan and one 20 Watt Energy saver for 6 hours. Yes it will run the load 24/7 where solar will be primary source of charging and utility will charge batteries as secondary source of supply.
The load will run at 220VAC and 50Hz.
Solar panels will be located at roof top.
As sun shine in Pakistan is average approximately 10 hours so charging time for solar panel will be approximately 9 to 10 hours depending on good sunshine day.
Battery bank will be located inside house at 30 to 45 temperature.
Now please tell preferred type of battery (lithium, nickle, lead, mercury, etc.) and battery size (Ah), preferred voltage 12V or 24V for battery.
A:
At first glance I wonder why you would use a battery at all in this system. A 100W solar panel will only generate 100W while operating under standard test conditions (STC). STC is 1000W/m^2, as well as a number of other parameters. If, for example, the panel is receiving 500W/m^2 at any given moment it will only be producing 50W, assuming all other conditions are equal to STC. it is only when the radiation goes above 1000W/m^2 that the panel will be producing more than 100W, again assuming that everything else matches STC. As you say there is quite good sunshine in Pakistan but I had a quick look at free sources (http://www.nrel.gov/international/ra_pakistan.html) and it looks like it doesn't go above 7kWh/m^2 (at latitude tilt) anywhere across the country.
In practice it is unlikely that everything else will match STC, with the temperature being a key place where it is unlikely to match. Different types of modules respond differently to changes in temperature of the module (usually significantly higher than air temperature), but in general if the temperature is above 25°C the performance will be reduced. To run an AC load you will need an inverter, which will have inefficiencies. You will also have losses in cabling. You can spend a lot of money to minimize these inefficiencies but there will always be some level of loss.
Essentially what I am saying is that there will be very little time at which your panel will be producing enough to fully power the load, let alone have excess with which to charge a battery. This makes me think that to optimize the solar usage you are best of skipping the battery entirely, and simply running the system with a normal grid-tied inverter so that you are offsetting some of the power requirements during sunny times, and being powered entirely by the grid the rest of the time.
It may be that you have your own reason for wanting to use a battery though, for example there may be different prices for grid power at different times of day, or grid power may simply not be available at some times. Your mention of UPS makes me think it may be the latter, in which case we come back to the frequency of demand cycles and operating conditions.
I suggest you look at it as three different questions, the first being whether it is worth having solar for this system, the second being whether it is worth having a battery, and the third being whether there is any benefit in having the two combined as one system.
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