Air Conditioning and Solar Panels

How Do Air Conditioners Work?

An air conditioner, or more properly, an air conditioner unit is a mechanical-electrical system that treats air in an enclosed area through a refrigeration cycle in which warm air is removed and replaced with cooler air.

The most important process in the operation of air conditioners is the 'refrigeration cycle'. In the refrigeration cycle, which is similar to what happens in a refrigerator, a pump transfers heat from a lower temperature source into a higher temperature heat sink. In other words, warm air is 'refrigerated' and then with the help of fans, pumped out and circulated in a closed space. This is the most common type of air conditioning.

A/Cs can be ducted, that is, transmitted through the entire building from a central ventilation system; self-contained and installed in windows or inserted in walls or come with an interior primary unit and an exterior compression in a two-stage split units. Though they are still available, self-contained window A/Cs have been outmoded by the more powerful split-units.

Can Air Conditioner Be Powered By Solar Panels?

Yes. Solar panels can be used to power a wide range of appliances that include air conditioning systems. Solar panels generate electricity from sunlight. The electricity they generate is not of a different type than what we receive through the national grid or from generators. In fact, solar panels produce a cleaner and safer electricity than grid power and generators. Also, much of the electricity that comes from the grid are 'low voltage' or 'low current' and may not power an A/C without a stabilizer. Solar panels produce electricity at optimum voltage.

There are not much or even any appliances that cannot be run on solar panels. It is rather a question of the power rating of the appliance than of its nature. A typical solar power system would incorporate solar panels, an inverter, a charge controller and battery for storage. It may not incorporate batteries. In this case, they will work only during the day when there is sunlight. Batteries are incorporated to provide back-up charge for when the solar panels cannot produce electricity and to maximize self-consumption. The charge controller controls and optimizes charging between the inverter and the solar panels.

What Then Are the Considerations?

What is the Efficiency of the A/C?

Split units come in three basic designs:

• the Standard or Non-inverter air conditioner;

• the Single Stage Inverter air conditioner and

• the Dual Stage Inverter air conditioner.

These technological configuration determines the efficiency of the air conditioner and in turn their power consumption. Relatively new, inverter air conditioners are technologically more advanced than conventional air conditioners. Inverter ACs are generally more efficient and therefore consume relatively less power than their non-inverter counterparts. This means that they will require fewer solar panels than non-inverter ACs. A standard can will use as much as 4X the power of a comparably sized dual inverter A/C. It is therefore necessary to choose an inverter A/C when thinking of adding it to your solar system.

The Power Rating of the Air Conditioner

Like all electronic appliances, A/Cs are rated by how much power in watts they consume per hour. This is the first consideration when designing a system that would power any appliance, an air conditioner included. For an already-existing system, a user can only incorporate an air conditioner running at peak power that does not overload his solar system. A user looking to acquire a new solar power system alongside an A/C would be guided by how the power needs of the washing machine matches his budget.

Is the System Dedicated?

Also, it will have to be determined if or what other appliances will use the solar power system while it is working. In most cases, A/Cs are used alongside other appliances like laptops, energy saver bulbs, LCD televisions and phone chargers. The user will have to decide the additional appliances that will be run on the system alongside the A/C. This will guide the engineer in designing the system.

How Much Grid-Power Is Available?

The amount (in hours) of grid power available to the user determines how long the A/C will be powered by the solar system. If grid power is sizeable, the system will be designed to provide backup power during the brief outage. If grid power is poor, then the system will be designed to provide the bulk of the power.

Will the A/C be Used Also At Night?

Solar panels do not work at night. Therefore, to be able to use them at night, which is often the case, the system will need to incorporate batteries. This adds severely to the cost of the system.

To give the requirements for designing a hypothetical solar power system for, the Hisense 1.0HP A/C, for instance: the popular Hisense 1.0HP is rated 2,800W. To power it alongside a few appliances, about ten (10) 350W solar panels (or any configuration that can deliver up to 3.5kW) are needed, and at least a 3.5kW to 4kW inverter. To maximise self-consumption at night, the system would require at least four (4) 200Ah batteries.

In the case of the Hisense 1.5HP, rated at 3,600W, the system will incorporate at least twelve (12) 350W solar panels and at least 4kW to 5kW inverter. To maximise self-consumption, the system would require at least four (4) 200AH batteries. Two A/Cs with similar power rating will require twice as much power, etc.

Solar Energy-Saver Hacks for A/C Users

1. Users are often encouraged to adjust their usage patterns when they seek to add a solar panel system. The first step is try and reduce net electricity consumption. One way of doing this is to switch from incandescent bulbs to energy saver bulbs. In the case of A/Cs, we advise users to buy inverter air conditioners instead of the standard air conditioners.

2. It is well known that when in use, doors should be closed to avoid the loss of cooled air.

3. We also advise users to turn off their A/Cs when not using them. This is a no-brainer and applies across the board.

4. Also, a ceiling fan should not be used alongside an A/C. A/Cs are installed towards the roof since cold air falls and when warm air rises. A/C units blow air cooled by their compressors down into the room, forcing the hot air to rise more rapidly and be captured and expelled by the A/C unit. By blowing down the warm air back, a ceiling fan interrupts this natural dynamic and therefore keeps the room warmer, in the case of which the A/C has to work harder and longer. House or room furniture should be arrayed in such a way that the A/C blows cold air directly without the need for a ceiling fan.

5. Most modern A/Cs come with a humidify and raindrop function on their remotes. Since we are in the tropics and receive more sunlight, the A/C should be mostly run on this setting. It will recirculate the air in your home and remove the moisture. It uses less power to dehumidify than to cool the room.

Solarkobo helps businesses and homeowners make the best choice of solar panels, inverters and other components that can meet their power needs. Our university-trained engineers also offer stellar installation services in Lagos and throughout Nigeria.