Can Solar Panels Run An Air Conditioner?
It was sobering to get an air conditioning bill as high as my winter heating bill! The comfort of using AC becomes quite painful when the electricity bill arrives. The ideal would be to reduce our power consumption and utility bills while continuing to using AC.
As a general rule a solar panel installation can run an air conditioner, if the surface area is big enough and an inverter is used to transform the power from a.c. to d.c. A battery bank may also be required, depending on the air conditioning running time during the day.
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How many watts does an air conditioner use per hour?
To determine how many watts an air conditioner uses per hour we need to understand how AC units are rated – in Tons. Why is AC rated in tons not in kW? It’s more convenient and accurate.
Different units may have different efficiencies in spite of having the same electrical energy needs. This means they may not have the same cooling effect, even though they draw the same power from the supply.
What does a ton mean in air conditioning?
A ton of refrigeration is approximately equal to 12,000 BTU/h or 3.5 kW. Therefore, the more tonnage an AC unit is rated at, the more air it can cool. 1 ton of cooling power means heat removed by a 1-ton AC in an hour.
Since 1 BTU = 1055 Joule, therefore the cooling capacity of 1 Ton AC in terms of Watts will be:
- (12000 x 1055) / 3600 = 3516 Joules / sec = 3516 Watts
What is the Energy Efficiency Ratio (ERR) formula for air conditioners?
Air conditioners are also rated in terms of their Energy Efficiency Ratio (ERR), which is the amount of heat removed in Watts in relation to the power consumed in Watts. (ERR=W/W)
In some countries individual AC units are given a star rating to show their efficiency – see table below:
|
Window A.C. |
Split A.C. |
|||
|
Star Rating |
Min EER |
Max EER |
Star Rating |
Min EER |
|
1 |
2.5 |
2.69 |
1 |
2.7 |
|
2 |
2.7 |
2.89 |
2 |
2.9 |
|
3 |
2.9 |
3.09 |
3 |
3.1 |
|
4 |
3.1 |
3.29 |
4 |
3.3 |
|
5 |
3.3 |
3.31 |
5 |
3.5 |
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Here are the electrical power ratings for various Star ratings. (1 Ton AC in terms of cooling Watts = 3516)
- 1 star – 1302 Watts
- 2 star – 1212 Watts
- 3 star – 1134 Watts
- 4 star – 1065 Watts
- 5 star – 1134.52 Watts
Example: A 5 star split AC with 1 ton cooling capacity is rated for 3516 Watts cooling power. It will consume 1134.52 watts electrical power per hour.
How much electricity does air conditioner use per hour?
For this calculation, we’ll use a 1 ton AC as an example.
- Energy =Power x time
- For a 1 ton unit Power = 3.516 kW
- Energy =3.516kW x 1 hour = 3.516kWh
So our 5 star split-AC with 1 ton cooling capacity is rated for 3516 Watts. It will consume 1134.52 watts of electrical power per hour.
1000 watts per hour is one unit of power consumed, so our 5 star unit consumes 1.13 kWh – but the compressor runs only 70 percent of the time during normal use.
Adjusted power consumption for one hour will be 0.7 units x 1.13 = 0.791 kWh
For 5 hours usage per day it will consume 0.791 x 5 = 3.95 kWh
How much power do solar panels produce per day?
Before we look at the question of calculating average solar panel output per day, we need to the understand difference types of solar panels and what is the insolation/irradiance level in your area.
What are the most efficient type of solar panels?
Three main solar technologies are commercially available are:
- Mono-crystalline
- Poly-crystalline
- Thin Film
|
Characteristics |
Monocrystalline |
Polycrystalline |
Thin Film (amorphous) |
|
Composition |
One crystal |
Multiple crystals |
Thin silicon layers |
|
Color |
Black |
Blue |
Multiple – varies |
|
Efficiency |
17 to 23% |
10 to 14% |
5 to 6% |
|
Lifetime Duration |
25 to 30 years |
20 to 25 years |
15 to 20 years |
|
Manufacturing Process |
Complicated |
Easier |
Complicated |
|
Cost |
Expensive |
Cheaper |
Expensive |
|
Temperature Tolerance |
0 to 5% |
-15 to +5% |
-3 to +3% |
Irradiance is the amount of sunshine received in any one place. It is a measure of the solar energy that is shining on a specified area at any instant in time.
Insolation is a measure of how many watts of energy shines over time. It is measured in KWh per square meter per day. Insolation map of USA.
A solar power meter can also be used to measure watts per square meter, which is often a more accurate way of checking the insolation levels for your particular location, rather than rely on area guidelines.
Solar panels ratings are given under Standard Conditions of insolation of 1000 watts per square meter at 25 degrees C. For average solar output let’s assume a 250-watt monocrystalline solar panel.
It can give maximum 250 watt of solar power under Standard Conditions that is, solar radiation is 1000 watt per square meter and temperature of panel is 25?.
The Standard Condition can be created in the laboratory but actually if solar radiation reaches 1000 watt/sq meter then the temperature would be much higher than 25 degrees C. It’s purely a theoretical standard for solar panel rating purposes only.
It is rare that solar radiation reaches 1000 watt per square meter, so actual power output of any solar panel will almost always be lower than its rated output.
For this exercise we’ll accept average energy output of a 250W monocrystalline panel as 250Watts/hour.
Solar engineers have a general rule of thumb that says on average we take 4 solar hours to represent a solar panel’s output over a 24 hour period.
In this case a 250W panel will produce 1kWh per day, which is 1 unit of electricity. Similarly, a 300W panel it will produce 300W*4= 1.2kWh (Remember these ideal numbers don’t exist in real life – panel output is much lower.)
How many solar panels to run an air conditioner?
As discussed earlier it depends on the size of air conditioner. For instance:
- For a 5 star 1-ton Ac the power rating = 1.1kW
As a rough guide, if we use a 250W panel and assuming Standard Conditions insolation, the number of panels required to run the air conditioner would be will be:
- 1.1/0.250 = 4.4 round off to 5
Can you run ac on solar without batteries?
Yes, we can run a ac without battery as describe above. To run a 5 star 1-ton AC you need to have 1.2 Kw solar System installed, or 5 to 6 solar panels rated at 250 watts, assuming irradiance of 1000 watts sunshine power per square meter.
The question is how long and in what part of the day can we run the AC? The strongest sunshine is in the two hours either side of mid-day. Before and after this period the power generated by fixed solar panels reduces dramatically.
Lunch-time is the hottest part of the day and it may be enough for your needs, but if air conditioning is needed at other times, or in cloudy weather, a battery bank will be require.
How many 12 volt batteries to run an air conditioner with solar?
The power input of a 1 Ton air conditioner is 1134.52W. This was calculated from:
- Power Input = Cooling Power in Ton/ERR = 3517/3.1 =1134.52W
Let’s say the AC runs for 6 Hours per day with power requirement 1134.52W:
- Total electricity consumption = 1134.52*6 = 6,807.12Wh
We have 5 solar panels of 250 watts each, which produce on average:
- 4 hours/day x 5 x 250 watts = 5000 Wh
Increasing the number of solar panels to 7 would generate enough to satisfy the AC energy consumption over 6 hours:
- 4 hours/day x 7 x 250 watts = 7000 Wh
12 volt battery bank capacity required is 7000 Wh = 583 Ah
Do portable solar powered air conditioners exist?
Portable solar power air conditioners are not in main stream usage till now but we will see portable ac as solar panel and particularly lithium battery technology develop.
DC power air conditioner do exist and they operate from two sources of electricity: photovoltaic as a priority and the electricity grid as a backup, when there is no sun. During the day time the air conditioner runs on solar and by night it will shifts to electricity by automatic switching.
Off-grid solar power air conditioners operate directly using DC 48V voltage from photovoltaics and batteries, without converting energy into AC 230V power and therefore without loss of efficiency.
When the sun is shining, the AC powered by the photovoltaic source which simultaneously recharges batteries. A MPPT controller optimizes this charge with an efficiency greater than 95%. A DC-powered solar air conditioner needs batteries, an inverter and solar charge controller to work in non-daylight hours – so they cost more than an AC unit.
Related Questions
How many solar panels to run 1 hp air conditioner?
For a 5 star 1-ton Ac the power rating = 1.1kW. You would need 5 x 250 watts solar panels to run this AC unit, assuming Standard Conditions of insolation.
How many solar panels to run 5 ton ac unit?
For a 5 star 5-ton Ac the power rating = 5kW. You would need 20 x 250 watts solar panels to run this AC unit, assuming Standard Conditions of insolation.
How many solar panels to run 3 ton air conditioner?
For a 5 star 3-ton Ac the power rating = 3kW. You would need 12 x 250 watts solar panels to run this AC unit, assuming Standard Conditions of insolation.
