Green Cooling: Why CO2 Heat Pumps are Future, Insights

In recent years, the world has witnessed a significant shift in the way we approach heating and cooling systems. One technology that has been gaining traction is the use of CO2 heat pumps. In this comprehensive article, we'll delve into the reasons why CO2 heat pumps are emerging as the future of cooling, exploring their history, advantages, applications, and the technology behind them.

The Evolution of CO2 as a Refrigerant

Green Cooling Why CO2 Heat Pumps are Future, Insights
Green Cooling Why CO2 Heat Pumps are Future, Insights

CO2, or carbon dioxide, is not a new player in the world of refrigeration. In fact, it was a popular refrigerant alongside ammonia in the mid-19th century. However, due to its need for specialized components to handle increased heat and pressure, it fell out of favor. The advent of CFCs and HCFCs in the 20th century brought new refrigerants, but they were later discovered to be harmful to the ozone layer, leading to a phase-out.

CO2 in Heat Pumps: A Game-Changer

1. Thermophysical Properties of CO2

CO2's unique thermophysical properties make it an excellent candidate for heat pump technology. Its ability to operate efficiently at both high and low temperatures sets it apart. Unlike traditional refrigerants, CO2 doesn't fully change phase, making it "transcritical" or "super critical."

2. Efficiency in Heat Transfer

CO2's efficiency in heat transfer makes it a standout choice for heat pumps. The nature of CO2 allows heat pumps to operate with a higher coefficient of performance (COP), reaching values from 2.6 to 5.5 depending on ambient temperatures. This surpasses the performance of many traditional heat pumps.

The Advantages of CO2 Heat Pumps

1. Cost-Effectiveness

CO2 is cost-effective, with a price tag of 1 to 2 dollars per pound compared to 5 to 14 dollars for most other refrigerants. Its affordability, coupled with its efficiency, makes it an attractive option for both manufacturers and consumers.

2. Safety and Environmental Benefits

CO2 is non-toxic, odorless, and environmentally friendly. Unlike CFCs and HCFCs, it does not contribute to ozone layer depletion. The minimal amount of CO2 used in heat pumps makes leaks less concerning, and its harm per pound is significantly lower than other refrigerants.

CO2 Heat Pumps in Action

1. Operational Characteristics

CO2 heat pumps operate at higher temperatures, allowing them to handle diverse applications. The ease with which CO2 can be pressurized and its effectiveness in absorbing and releasing heat make it an ideal choice for various heating and cooling needs.

2. Combination with Water Heaters

The combination of CO2 with water heaters is a synergistic relationship. Water, known for its excellent cooling properties, complements CO2, making the cooling process more efficient. This partnership extends to the heating of water, a challenging task that CO2 makes more effective than other common refrigerants.

Challenges and Optimizations

While CO2 heat pumps offer numerous advantages, they are not without challenges. The technology's higher temperature and pressure requirements necessitate more advanced and expensive components, impacting upfront costs. Despite this, companies like Harvest Thermal are optimizing CO2 heat pumps with smart energy management, offering substantial energy cost savings.

Innovations in Commercial Use of CO2 Heat Pumps

In the commercial sector, CO2 heat pumps are making waves with innovative applications and solutions that go beyond traditional heating and cooling. Let's explore how companies like Harvest Thermal are taking CO2 heat pump technology to new heights.

Harvest Thermal's Breakthrough: The SANCO2 System

Harvest Thermal has taken the lead in optimizing CO2 heat pumps for commercial and industrial use. Their system, based on the existing SANCO2 heat pump product from Eco2, introduces two key elements that enhance performance: a large water tank for hot water storage and a smart management system called the "smart pod."

1. Thermal Battery for Energy Storage

The integration of a large water tank serves as a thermal battery, allowing the system to store excess heat generated by the CO2 heat pump during periods of lower energy demand. This stored energy can then be utilized during peak demand times, reducing reliance on the electrical grid during high-cost periods.

2. Smart Energy Management with the "Smart Pod"

Harvest Thermal's "smart pod" is a game-changer in the world of CO2 heat pump technology. This intelligent management system optimizes the operation of the heat pump by running it during periods of low electricity costs. By leveraging the duck curve phenomenon, where electricity prices are lower during the day when solar electricity production is abundant, the system capitalizes on cost savings.

The Duck Curve Phenomenon

The duck curve illustrates the typical daily electricity demand curve, showing higher demand during mornings and evenings and lower demand during midday. Harvest Thermal's smart pod strategically aligns the operation of the CO2 heat pump with the low-cost periods, maximizing energy cost savings.

Performance Metrics: COP and Energy Savings

1. Coefficient of Performance (COP)

The SANCO2 heat pump, enhanced by Harvest Thermal's innovations, achieves impressive COP values ranging from 2.6 to 5.5, depending on ambient temperatures. This surpasses the performance of traditional heat pumps, making it a cost-effective and energy-efficient solution.

2. Energy Cost Savings

Harvest Thermal claims a potential 45% reduction in energy bills compared to standard gas heaters. The combination of CO2 heat pump efficiency, thermal battery utilization, and smart energy management contributes to substantial cost savings for consumers.

Challenges and Considerations

While the SANCO2 system presents groundbreaking advancements, challenges remain. The upfront installation cost, approximately twice that of a standard HVAC system, poses a barrier for widespread adoption. Additionally, the need to replace both air conditioners and water heaters increases the spatial and financial requirements.

The Road Ahead: CO2 Heat Pumps as a Sustainable Solution

1. Environmental Impact

CO2 heat pumps contribute to a more sustainable future by minimizing environmental harm. Their non-toxic nature, low risk of leakage, and reduced reliance on traditional refrigerants align with the global push for eco-friendly solutions. As the world seeks alternatives to combat climate change, CO2 heat pumps present a compelling option.

2. Diverse Applications in Sustainable Practices

Beyond heating and cooling, CO2 heat pumps have the potential to play a crucial role in broader sustainability initiatives. From reducing reliance on fossil fuels to optimizing energy consumption, the technology aligns with global efforts to transition to cleaner and more efficient energy solutions.


In conclusion, the future of sustainable heating and cooling is increasingly intertwined with the evolution of CO2 heat pump technology. While challenges such as upfront costs persist, the long-term benefits, environmental considerations, and the versatility of CO2 heat pumps position them as a promising solution. As the world continues to prioritize sustainable practices, the adoption of CO2 heat pumps may become a cornerstone in the journey toward a greener and more energy-efficient future.

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