Smart technology has led to inventions and innovations that connect devices and people. Initially, apps controlled various stand-alone devices. Later, technology like Bluetooth and Wi-Fi interconnected devices. It’s grown beyond that to smart homes and commercial buildings. The Internet of things (IoT) connects everything, including climate control systems.
Technology demands ever-increasing amounts of electricity. Climate control systems average about half of the power coming into residences and workplaces. Huge bills from the energy companies face homeowners and building managers, especially during the record-setting heat and cold weather prevalent the past year.
Solar power is evolving to meet those energy needs, creating a growing demand for solar HVAC.
Photovoltaic (PV) panels are the most common way of converting sunlight into electrical energy. Excess energy is typically stored in batteries for use when there isn’t sunlight. The energy produced is DC (direct current) power. An inverter converts the DC power to AC (alternating current) power so that any system or equipment can use the electricity.
Determining the number of PV panels required involves several factors. Different parts of the country have varying hours of sunshine a day. Fewer hours of sunlight equal fewer hours of electrical power produced. Another factor is the size of the HVAC system. Expected usage is the final factor.
Calculations that account for all those factors are used to establish how many PV panels are needed, what size the panels should be, and how many batteries are necessary if the system will be used when there is no sunshine. The storage capacity of the batteries also affects how many will be needed. Experts consider 48V to be the most efficient.
The number of solar batteries required further depends on how much power it takes to run the HVAC system and for how long they will need to supply power. They can be configured to power only the climate control system or to power additional appliances. Most installations use lithium-ion batteries. Homeowners may use lead-acid batteries to save upfront costs. Lead-acid batteries wear out quicker and don’t store as much power as lithium-ion batteries.
Solar-powered air conditioning uses electrical energy produced by the PV panels. The systems are usually heat pumps. If the solar HVAC is a DC system, the power from the PV panels goes to it prior to being stored in batteries or used in other appliances.
Solar thermal air conditioning relies on flat metal plates to collect the sun’s heat. The heat powers an electric generator, which in turn powers the HVAC compressor. Conventional electrical power is required to power fans and other components. This process is generally referred to as solar air conditioning, as distinguished from solar-powered air conditioning.
Solar air conditioning has fallen out of favor as it is less efficient than solar-powered air conditioning. Some systems have been withdrawn from the market as they failed to meet the minimum energy performance standards set by the Department of Environment and Energy.
Various other types of solar collectors and technology capture the sun’s energy for use in climate control. These currently include:
With the exception of the concentrating system, the collectors only produce heat. They are used to heat buildings but are more often used for hot water heating. They are not heat pumps, and they are not used for cooling. The concentrating solar system produces heat of much higher temperatures than the other collectors and is the only one of the collectors that also produces electricity.
Some facilities may use absorption chillers. Components of these units cool the air through a process of condensation and evaporation. Solar power from PV panels or batteries can power the fans and motors.
Solar HVAC systems can be one of three types, depending on whether they use DC power, AC power, or a combination of AC and DC power. Most systems are small and intended to provide supplemental cooling or heating. Many are designated as “mini-split” or ductless systems.
A conventional DC air conditioner is wired to the power supply—in this case, the PV panels. The majority of climate control systems require AC power. Hybrid solar-powered air conditioners run on either DC or AC power. Each type of system has pros and cons.
Because DC systems are connected directly to the PV panels, they tend to be less expensive to install and maintain. They don’t require batteries if the homeowner is willing to forego climate control when the sun isn’t shining. Using the system when there isn’t sunlight requires the added expense of batteries and inverter.
AC climate control systems are tied to the electrical grid. If the PV panels produce excess power, the excess can be fed back into the grid, decreasing the cost of electricity from the electric company. When it’s dark, the system gets power from the grid so that the occupants have 24/7 climate control. Although the cost of the basic AC equipment is less than DC equipment, AC systems will not work off the grid.
Hybrid climate control systems use both AC and DC power. The systems can be connected to the PV panels and to the building’s electrical panel or to the grid. Most switch between AC and DC power automatically to provide continuous comfort. The system does not require an inverter or a battery, but most have an inverter, and a few include batteries. Excess power is stored in batteries if those are installed.
The systems often use plug and play technology that makes them easier to install. If they are installed off the grid and without a battery, the systems do not work when there is no sunlight.
Event Horizon’s ACDC12C unit is a hybrid solar air conditioner and heat pump. Although it’s a hybrid, it’s designed primarily for off-grid use. When used entirely off-grid, batteries and charge controllers are required. Although installation is touted as a DIY project for homeowners, adding refrigerant should be done by an HVAC technician. It requires PC panels that can produce about 750 watts.
Gree manufactures solar hybrid heat pumps with built-in inverters. The sensorless inverter fan motor and DC compressor use advanced technology to reduce noise and vibration while improving efficiency. Capacities range from three to ten tons, making the units appropriate for a variety of structures.
Hotspot offers several 48V DC heat pump units designed for full off-grid operation. They can save excess power in either golf cart or deep-cycle batteries. They feature variable speed, capacity, and refrigerant flow. Their ACDC12C models are hybrid heat pumps. While batteries can be added for off-grid use, Hotspot does not recommend doing so. Plug and play technology makes installation easy.
The Lennox SunSource products are complete systems designed for use with “solar modules.” Both heat pumps and air conditioners are available. All are high-efficiency units that are designed to run quietly. Rather than one inverter for the system, each solar module has a “microinverter.” Homeowners can expand their systems easier if needed.
The LEZETi hybrid is an air conditioner only. Although it runs off DC power from PV panels, it must always be connected to a 220/240VAC power source. It is not intended for off-grid use. It uses plug and play technology for ease of installation.
Solair manufactures hybrid solar-powered air conditioners and off-grid DC units. The hybrid units are available from 9,000 BTU to 24,000 BTU cooling and 9,500 BTU to 25,000 BTU healing capacity. The system must be connected to a 220/240VAC power source and automatically switches to that source when there isn’t enough sunshine.
The 48V DC air conditioner models range from 12,000 to 24,000 BTU capacity. They require charge controllers and batteries. Both the DC and hybrid models use plug and play technology.
YMGI solar-powered heat pumps all feature variable refrigerant flow technology. The systems are modular and can be installed in multiples of three so that they can be easily retrofitted or expanded. Systems are available in 36,000, 48,000, and 96,000 BTU cooling with 45,000, 54,000, and 108,000 BTU heating capacity.
They also manufacture smaller DC inverter heat pump systems. The units supply from 9,000 to 36,000 BTU cooling capacity and from 10,000 to 40,000 BTU heating capacity. They require from 450 to 1800 W to operate.
Solar Week is presented online every spring and fall. It’s designed to teach students from ages nine to 14 about the solar system. It features games, hands-on activities, and interactions with solar scientists. Each day of the week has a different lesson. The lessons, games, and activities are archived for year-round access.
Youngsters who are curious about the solar system, stars, weather in space, astronomy, or a career as a scientist will find a wealth of reliable information. The “Ask A Question” message board provides an opportunity to ask questions of the scientists. Recent ones included how to use solar energy, the strength of magnetic fields in sunspots, and what scientists like to look at through their personal telescopes.
Each day of Solar Week is devoted to a particular aspect of the sun and its relationship to the earth. The March 2021 lessons included the following:
The October 2021 curriculum has not yet been posted on the website. We encourage the participation of your school children as well as your personal contribution of time and knowledge.
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