DC Air Conditioner
Zamna Climate DC12 OFF GRID
12,000 BTU DC Air Conditioner For Off-Grid Solar & Telecom Applications
This pure-DC unit is for when main power comes from solar or 48v (or -48v) battery plant. EER >19 ultra low power consumption, military-grade compressor, AC & generator backup option available. Heat pump model available
If your power source is native 48VDC (or -48VDC) as part of a telecom or off-grid solar application, Zamna Climate DC12 OFF GRID all-DC air conditioners are your most efficient cooling choice. DC12 air conditioners can substantially reduce power supply/generation costs and battery requirements. An all-DC system means you get the advantage of extreme high efficiency without the need for inverters.
The Zamna Climate DC12 is a purpose-built DC powered air conditioner heat pump for native DC power. It's designed to conserve power, and operate reliably for many years without maintenance.
SeaSpray Anti-Corrosion technology protects circuit boards, condenser, evaporator, compressor, and fan motors from salt air corrosion. SeaSpray is available beginning Q2 2014.
The DC12 is a variable capacity, variable speed, variable refrigerant flow unit. There is no other solar or DC air conditioner like it on the market.
HOW IT WORKS
It starts with the compressor which uses 95% of the power consumed by an air conditioner. In all ultra-high efficiency AC-powered mini-split units, household electricity enters the air conditioner and passes through a rectifier, a component that converts the incoming Alternating Current (AC) to Direct Current (DC). The DC current passes through a frequency driver which applies power to the motor. The frequency of the power determines the output of the motor, which can be digitally managed to precisely control the motors speed. Because DC power can be used more efficiently, all of the highest efficiency AC-powered heat pumps and air conditioners on the market use DC powered compressors.
In an off-grid solar configuration where an AC-powered air conditioner is running from inverted solar power, the power is actually being converted twice. First, the native DC power from solar panels is inverted to AC by the inverter, and then the power is immediately converted back to DC after entering the air conditioner. Sound wasteful? It is, requiring more solar panels and more batteries as a result.
A key difference with our system – the DC12 unit skips all of these conversions and uses the DC power directly without conversion loss.
DC VRF Solution
In addition to avoiding the cost and power loss of an inverter, our system is engineered from the ground up for use with solar. Special electronics anticipate and smoothly handle voltage fluctuations of up to 38% without affecting the operation. In addition to the compressor and control circuits, all other electrical components are DC powered including high efficiency DC fan motors, DC valves & solenoids, etc. There are no inverters used inside the system.
The brushless DC compressor and fan motors we use provide a "soft-start" which means that the typical startup surge of an AC air conditioner running on an inverter is eliminated. A normal air conditioner will draw up to 500% more amps on startup, meaning that when running on an inverter, the inverter must be oversized accordingly. Oversized inverters are much less efficient. The DC motors and controls used in the DC12 system not only avoid needing an inverter, they also minimize the surge or spike at time of startup.
DC VRF Compressor
The system uses a VRF (Variable Refrigerant Flow) controller and frequency driver in conjunction with multiple sensors and an algorithmic control circuit to raise and lower the units capacity in real time based on conditions as they change. The VRF controller manages the compressor speed, refrigerant flow, fan speed, etc., which can all be precisely matched to the immediate cooling requirements. As the set-point is closely approached, the system will lower its capacity and power consumption, running at a very low energy draw as needed to maintain proper temperature rather than overshooting the set-point and then cycling on and off like a standard air conditioner. Not including the avoided DC to AC to DC power conversion losses, the VRF feature alone saves 30-40% compared to a standard air conditioner.
The DC12 air conditioner uses a neodymium permanent-magnet Brushless Direct Current (BLDC) hermetically sealed motor and compressor with high performance windings, similar to the technology used in the worlds highest efficiency air conditioners. This particular compressor is made for us by the same manufacturer that makes high efficiency compressors for Fujitsu, Carrier, Toshiba, and LG.
Considering the high cost of solar panels and batteries, it is crucial in an off-grid solar situation to make the absolute best use of every watt of power. That's where the DC4812VRF air conditioner proves its value by operating with the lowest possible amount of DC power consumption.
Charge Controller Options for Solar Air Conditioner
The Zamna Climate DC12 solar air conditioner always connects to a 48v battery plant. The battery plant typically consists of multiples of 6v or 12v batteries wired in series to produce a 48v string system. For example, you could use 4 x 12v or 8 x 6v (golf cart type) batteries. Then each of these battery strings could be paralleled with a duplicate string to increase the amp hours and still be at 48v.
Connecting the batteries to the solar panels is a component called a charge controller. There are two technology options for charge controllers, you would select either PWM (Pulse Width Modulation) or MPPT (Maximum Power Point Tracking).
The PWM type is very low cost but has less efficiency, particularly in colder climates. When a battery is charged to rated voltage, the charge controller must begin limiting the amount of current into the battery so that voltage is maintained but not surpassed. PWM sends power to the battery with pulses of a varying width, wider pulses allow a greater percentage of the input current to flow into the battery. The PWM option would be the Morningstar Tristar TS-45. This is a full featured 45a PWM charge controller that is available with remote meter and/or temperature sensor.
The other type, MPPT controllers, extract the maximum power from solar panels, but cost more. MPPT controllers use an algorithm to track the PV panel performance and manages the PV panel voltage based on the maximum power point. It checks the PV output and compares it to battery voltage, then makes adjustments to the voltage to input the maximum current into the battery. MPPT forces PV module to operate at voltage close to maximum power point to produce maximum available power. While we recommend MPPT controllers, we do offer a low-cost “budget option” of a PWM controller with our entry level solar air conditioner package. You can see several pre-configured solar AC packages here.
For maximum power utilization in a solar air conditioning application we recommend MPPT charge controllers and we offer the Morningstar TS-MPPT-45 and TS-MPPT-60 charge controllers for this purpose.
Here is a link to the Morningstar String Calculator
Here is a link to our advanced Carbon AGM batteries.
Solar 48v Battery Information
When used in a properly conditioned environment, batteries can store large amounts of energy that can be used when needed and last 6-8 years or longer. One application that that is rapidly growing is the demand for 48 volt DC air conditioners known as solar or DC mini split systems. When connected to a 48 volt battery bank, and a properly sized photovoltaic solar system, these solar mini-splits can run all day and/or all night without using any energy from the grid. These solar AC systems are designed for locations where utility power is unavailable or unreliable, of where people have decided to go off-grid for ecological or other reasons.
Solar Battery Wiring Diagrams
Deep Cycle Only
Want some really great solar deep cycle batteries? These cost more than buying Trojan batteries at your local Trojan dealer, but are well worth the difference in life expectancy and performance.
Deep cycle batteries can be charged and discharged repeatedly without damage to the battery when the manufacturer’s guidelines are followed. For this reason, only deep cycle batteries are recommended for solar and solar air conditioning applications. Note, marine batteries are often not “true” deep cycle batteries, so make sure to check the specifications of any battery you are considering.
The construction of a battery storage compartment or housing is critical because of the weight of the plates and insulators used to generate the proper voltage and current. All batteries consist of individual cells that generate voltage using chemical compounds to create an electrical charge. To use this charge, a conductive path is created by the electrodes and grids that are bonded internally. The battery cells are made up of insulators and plates that have both negative and positive polarities. The polarities are separated by an insulating material that varies by manufacturer. The electrolyte (lead acid) consists of free electrons that are liberated through a chemical reaction and are absorbed in the separator material.
What type of deep cycle battery is best for a solar or DC air conditioner?
Click Here For Advanced Carbon AGM Solar Batteries (Deep Cycle)
These are the most powerful and longest life batteries on the market. Not cheap to buy but much lower cost to own.
Lead Acid Batteries: Lead acid batteries contain electrodes and grids made from lead plates. Polarity is determined by the lead oxide material that coats the grids. These are the most common and lowest cost type and are also called flooded batteries.
Flooded Batteries: This battery is the most commonly produced and purchased type and therefore it is lowest cost solution on the market, this is what we normally recommend for solar air conditioners. Outside of solar, deep cycle flooded batteries are mainly used for forklifts, golf carts, floor buffer machines, etc. and are fine for most solar applications. They do require distilled water during quarterly maintenance periods.
Sealed Batteries: This type of battery is sealed and does not require periodic topping off of distilled water. The manufacturer fills the battery with a sufficient amount of water and acid to last through the stated warranty.
VRLA Batteries: Valve Regulated Lead Acid batteries are sealed. This is also a sealed battery that does not need maintenance. One advantage VRLA batteries have is they vent less gas than a standard lead acid battery. They are considered AGM or GEL type batteries because of the regulating valve used to vent the hydrogen gas produced when charging the battery.
AGM Batteries: Absorbed Glass Matt batteries are ideal when the battery storage area is poorly ventilated. Other advantages are the electrolyte is absorbed in a mat which means that what is inside cannot spill out like the acid in a flooded battery. They are vented with a pressure relief valve during charging, very similar to a VRLA battery. This type of battery is fine for off grid applications and remote telecom power plants although they are more costly than standard batteries.
GEL or Gel Cell Batteries: Because gel cell batteries are sealed like an AGM battery, maintenance is at a minimum. Silica and Sulfuric acid are combined to turn the substance into a jelly like form. This jelly is the electrolyte and must not be exposed to high amperage situations such as fast charging or discharging. Doing so may scar the jelly and lead to battery failure. These cells are very sensitive to over charging.
General Battery Info:
Always read the battery manufacturer's instructions concerning charging the battery. Always locate the batteries in a well ventilated and approved battery cabinet prior to connecting or charging the battery bank. Hazardous and explosive gases may be generated during the charging of the battery and can be dangerous. Please dispose of unusable batteries according to you local disposal codes.
Solar Battery Sizing Information:
To get the longest life from a deep cycle battery the idea is to limit the depth of the discharge. Discharging a battery all the way down will damage the battery slightly each time, lower the future performance, and shorten the life of the battery. For this reason it is recommended to oversize the battery plant such that the batteries don't discharge too deeply. For example, golf cart batteries that are discharged about 50% can last 6-8 years whereas the same battery discharged at 80% may last only 2-3 years. We suggest to never discharge a battery more than 60%. In general a 50% discharge is an ideal number, meaning that the AH of the battery system should be such that it is 200% of the expected requirement.
Selecting & Sizing Solar PV Panel Array
for DC Air Conditioner
Selecting the right PV solar panels for a small solar installation like a solar powered air conditioning application can be confusing. Here is what you need to know:
POLY VS. MONO
There are 2 main types of commonly available and affordable solar panels in the market, made from either polycrystalline (Poly) and monocrystalline (Mono) silicon cells. The difference is that Mono costs more per watt but has a higher power density. Note the panels are always priced by the Watt and Poly has a lower cost per Watt. The advantages of Mono are when you have a larger solar panel installation, you may see that incremental costs for installation, shipping, and mounting hardware are less per watt on Mono bringing the total cost per watt inline with that of a Poly installation. Sometimes this gives the Mono panels a slight total cost advantage on larger projects, but the advantage is not usually seen on smaller PV projects.
Mono panels take about 5% less roof space, so if roof area for mounting panels on a large project is tight, Mono may allow a few extra Watts to be installed in the same footprint. This is ultimately the net difference between these types of panels.
We recommend either type but since Poly is more widely sold and has lower cost per Watt it is generally better for small projects (under 4-5kW total size).
SIZING THE ARRAY
Panels are rated on their peak watts, meaning that under direct DNI (Direct Normal solar Insolation, 1000 watts per meter) this is the amount of power that a panel can produce per hour of sun at this strength.
Sun hours and daylight hours are not the same thing. Each area of the planet has a total number of “sun hours” also referred to as DNI, solar insolation, radiation, or irradiation. These are annual averages and consider the average rain or cloud cover for the area. Don’t let it confuse you, all of these solar terms mean the same thing. Solar power is measured at kWh (kilowatt hours) available per day per square meter. So for example an area with a rating of 5 kWh per day of solar irradiance or insolation would have 5 "solar hours” or “sun hours” or a DNI of 5 kWh. You can click here to see various solar insolation maps and charts that show the solar radiation for areas of the USA and around the world.
To know how many Watts are needed you must consider the total amount of solar energy needed per day. For off-grid applications like solar air conditioning this means the amount of power needed to run the system during the sun period PLUS the amount of power needed to be stored in batteries to provide after-sun operation. The amount of after-sun hours also determines the size of the battery plant.
For example, if your solar air conditioner needs 5 kWh per day to provide the number of hours of operation needed, and your area has 5 sun hours per day, you would need to install approximately 1 kWh of solar PV panels. This is based on 1 kWh of production capacity per hour multiplied by the 5 sun hours of your location.
The basic formula is to take the kWh needed per day by the system being powered and divide it by the sun hours for the location, then divide that by the panel Watts rating (in kW), to see how many panels are needed. Note that a 200 W panel would be expressed as .2 KW for this calculation.
Always round up to the next number of panels to create strings of 3, they must be grouped in strings of 3, so it will always be 3,6,9,12 etc.
Temperature is a factor. All solar panels are rated at a STC (standard test condition) at the time they are manufactured. The actual power will be lower at high temperatures and higher at lower temperatures. A string sizing calculator using the values from the panel specifications label can give you the best indication of real power at various temperatures. See string sizing information in the section on charge controllers.
You should allow a little extra for power loss across the batteries, charge controller, cables, etc. and you may also wish to allow for non-typical daily insolation values, called a cloud-margin or rain-margin. This means you could allow for some extra solar/battery capacity if the DC system may need to operate under cloudy or rain conditions that affect the normal ability of the panels to provide the rated power.
DC air conditioners require 48v batteries. The cheapest way to do this will be with 8x 6v golf cart batteries. The best way to do it is to use the 20-year maintenance free Carbon AGM batteries here.
Solar & DC Air Conditioner
System Kit Information
Values given below are for areas with 5 solar hours per day. To calculate the sun hours for your area please use the resources listed at the bottom of this page.
Complete system prices are examples only and do not include shipping costs. Contact us for current price and availability of any solar components.
Battery prices included are for reference only and are based on typical market prices in the USA. We do not sell batteries. Please get your batteries from a local supplier or contact us for assistance in locating a supplier in your area.
NOTE* BELOW ARE BUDGETARY SYSTEM COST ESTIMATES. PV module sizes and cost per watt change frequently.